Article

Organic matter digestibility of poplar (Populus) and willow (Salix) forage trees and its in vitro prediction

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Abstract

Cuttings from poplar (Populus) and willow (Salix) trees are used increasingly as supplementary feed for livestock in summer-dry and drought-prone regions of New Zealand. The present experiment aimed to measure in vivo organic matter digestibility and digestibility of organic matter in the dry matter in tree fodder and investigated whether the in vitro system of Roughan and Holland can be used to predict in vivo organic matter digestibility and digestibility of organic matter in the dry matter in poplar and willow tree fodder, which contains high concentrations of secondary compounds, including condensed tannin. In vivo work showed that the digestibility of tree fodder declined from late spring to autumn (p < 0.05) and that this decline was much smaller than the decline in digestibility of grass-based pastures in New Zealand over the same time period. Mean metabolizable energy concentrations and digestibilities were generally higher for willow than for poplar. The in vitro enzymatic system of Roughan and Holland can be used to predict in vivo digestibility of tree fodder. A standard curve using in vivo values determined with animals fed tree fodder would be preferable, owing to the very different chemical compositions of pasture and tree fodder, particularly the greater concentration of secondary compounds in willow and poplar. However, the accuracy and the range of prediction need to be improved. Willow and poplar had similar ME concentrations to high-quality lucerne hay; willow cuttings also had similar ME and CT concentration to vegetative Lotus corniculatus, a high-quality forage legume. Copyright © 2005 Society of Chemical Industry

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... However, it must be remembered that predicting nutritive value of tree material reliably from chemical analysis is difficult, because of the interference of CT's and other phenolic compounds with the digestibility of the fibre fraction (Tolera et al., 1997). McWilliam et al. (2005) validated a reasonably reliable calibration curve for prediction of in vivo digestibility of willow by sheep, from the results of in vitro analysis based on the enzymatic method of Rougham and Holland (1977), across a limited range of composition. This gave slightly different predictions from those derived using a calibration curve for grass-clover herbage and was therefore deemed preferable. ...
... Measuring digestibility in vivo would be the best method to determine digestibility. Organic matter digestibility measured in cryptorchid lambs in New Zealand fed fresh tree fodder twice daily, ranged from 0.64 to 0.70 for willow and from 0.62 to 0.67 for poplar over one growing season (McWilliam et al., 2005). Intake of these lambs was between 0.75 and 1.12 kg DM/day for poplar and 0.91 and 1.01 kg DM/day for willow (McWilliam et al., 2005). ...
... Organic matter digestibility measured in cryptorchid lambs in New Zealand fed fresh tree fodder twice daily, ranged from 0.64 to 0.70 for willow and from 0.62 to 0.67 for poplar over one growing season (McWilliam et al., 2005). Intake of these lambs was between 0.75 and 1.12 kg DM/day for poplar and 0.91 and 1.01 kg DM/day for willow (McWilliam et al., 2005). ...
Article
Agroforestry, the integration of trees and agriculture, is valued as a multifunctional land use approach that balances the production of commodities (food, feed, fuel, fibre etc.) with non-commodity outputs such as environmental protection and cultural and landscape amenities. In this study, the possibilities for fodder production from a short rotation coppice of willow (Salix viminalis) used for wood chips to produce energy were investigated. The nutritional value and ensilability were assessed from first year regrowth of willow harvested on 29 June 2011 at Wakelyns Agroforestry, Suffolk, UK. The willow branches with a stem diameter less than 8 mm were manually harvested from 4 plots in two replicates. From 2 plots, another sample was prepared including leaves only. Both dried raw material and silage samples ensiled in evacuated polyethylene bags were analyzed. The crude protein concentration was relatively high in leaf + stem silage (182 g/kg dry matter (DM)) and even higher in leaf only silage (219 g/kg DM) and the fibre concentration was relatively low. However, the organic matter digestibility determined by in vitro pepsin-cellulase method was low (0.421 for leaf + stem silage and 0.511 for leaf only silage) and it cannot be considered as a suitable feed for lactating dairy cows. However, it might be suitable for other animal groups with lower energy requirements. The appearance and smell of the silage samples at opening of the vacuum plastic bags was rather pleasant with minor deteriorations (probably yeasts) visible. The extent of fermentation was low and pH high (5.79) for a rather low DM material (DM concentration 276 g/kg). The water soluble carbohydrates of the raw material (35 g/kg DM) and the residual water soluble carbohydrate concentration in silages was relatively low, which at least partly explains the restricted production of fermentation acids. The fermentation profile was heterofermentative (acetic acid dominated instead of lactic acid). The concentrations of total condensed tannins fractions were almost twice as high in the leaf only silage compared to leaf + stem silage. Although the feed values of willow were low, it may have a role in multifunctional systems, where it can provide additional values in grazing situations such as self-medication and microclimate benefits. For easy and efficient use in animal production, controlled browsing might be used; otherwise methods for harvesting and preservation need to be developed. There seems to be some scope for ensiling willow material. This work is part of an EU FP7 funded project “Sustainable organic and low input dairying” (SOLID, KBBE.2010.1.2-02). For more information on the project, see www.solidairy.eu
... Nutrients accumulated in leaves can be fed back to the stock to prevent nutrient deficiencies, especially in times of drought. Poplar and willow trees can provide leaves with a high concentration of condensed tannins, proteins and trace elements (Moore et al., 2003;McWilliam et al., 2005;Robinson et al., 2005), that may be beneficial for livestock health. Both willow and poplar leaves showed high concentrations of condensed tannins (Matheson, 2000), which may enhance protein digestion in animals. ...
... Especially on hills and in riparian zones, poplars and willows reduce soil erosion through their extensive root systems and high evapotranspiration rates (Douglas et al., 2010), which helps drying out waterlogged soil (Guevara-Escobar et al., 2000;Ball et al., 2005;McWilliam et al., 2005). Erosion control may result in an increase in livestock carrying capacity and mitigating soil and nutrient losses into nearby streams and catchments (McWilliam, 2004). ...
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Intensive pastoral farming has been linked to adverse environmental effects such as soil degradation and increased fluxes of nitrogen, phosphorus, sediments, and pathogens into waterways, resulting in their degradation. Stand-off pads are engineered structures covered with bedding materials, available for occupation by stock to minimise those adverse effects to soil and water bodies. Wood chips are ideal for bedding due to their low cost, high water holding capacity, and stock preference as resting areas. While they reduce the mobility of both nutrients and pathogens, their effectiveness depends on the type of wood, size of the chips, pH, pad design, and feeding management used. Dissolved organic carbon, present in wood residue, may slow nitrogen mineralisation thereby decreasing loss via leachate. This effect depends on plant tannins and nutrients already stored within the plant tissue. Poplar and willow have high concentrations of tannins in leaves and bark with potential nitrification-inhibiting properties. When grown on-farm, these deep-rooted trees also reduce nitrogen leaching and prevent soil erosion. This review addresses the use of temporary stand-off pads within poplar or willow silvopastoral systems. Harvested trees can provide suitable wood chips for constructing the stand-off pad, while the deep rooting systems of the trees will reduce the moisture content of the pad, preventing waterlogging. A key objective is to discuss the feasibility and establishment of multiple temporary stand-off pads that allow for stock rotation from pad to pad, and subsequent on-site composting of wood-wastes into fertiliser, reducing both nutrient inputs and losses in agricultural systems. The review highlights the potential suitability of poplar and willow tree species for such a system.
... Bioproducts from poplars (propolis, flavonoids, bud extracts) have also various applications in medicine, health foods, cosmetics and plant disease control [146,147]. Poplar foliage and rameal wood are currently used as an inexpensive fodder during drought or as supplements to increase livestock reproductive capacity [148,149]. Litter fall from poplar buffers reaching adjacent cropping systems can contribute to improving soil fertility and food crop productivity [150]. Planted poplars are also naturally colonised by a wide array of fungi, including the oyster mushroom (Pleurotus ostreatus), a well-known edible mushroom [151] (Figure 5c), which can also be cultivated on poplar logs. ...
... ‚ For bioenergy production, select productive clones with a high energy content per unit of biomass. Food ‚ Poplar foliage and rameal wood can be used as a fodder for livestock, but also as a supplement to increase reproductive capacity [148,149]. ‚ Poplar litter has a positive effect on adjacent farm soil fertility [150]. ‚ ...
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In temperate agricultural watersheds, the rehabilitation of tree vegetation in degraded riparian zones can provide many ecosystem services. This study evaluated ecosystem service provision potential following the conversion of non-managed herbaceous buffers to hybrid poplar (Populus spp.) buffers in three watersheds (555–771 km2) of southern Québec (Canada), with contrasting agricultural land uses. To extrapolate services at the watershed level, total stream length where hybrid poplars could be established was calculated using GIS data from hydrological and land cover maps. After nine years, a 100% replacement of herbaceous buffers by hybrid poplar buffers along farm streams could lead to the production of 5280–76,151 tons of whole tree (stems + branches) biomass, which could heat 0.5–6.5 ha of greenhouses for nine years, with the potential of displacing 2–29 million litres of fuel oil. Alternatively, the production of 3887–56,135 tons of stem biomass (fuelwood) could heat 55–794 new farmhouses or 40–577 old farmhouses for nine years. Producing fuelwood in buffers rather than in farm woodlots could create forest conservation opportunities on 300–4553 ha. Replacing all herbaceous buffers by poplar buffers could provide potential storage of 2984–42,132 t C, 29–442 t N and 3–56 t P in plant biomass, if woody biomass is not harvested. The greatest potential for services provision was in the Pike River watershed where agriculture is the dominant land use. A review of the potential services of poplar buffers is made, and guidelines for managing services and disservices are provided.
... Balsam poplar (Populus balsamifera) as a possible feed ingredient for cattle has been studied since they contain a wide range of bioactive compounds with antioxidant activity [16][17][18]. Cuttings from poplar were shown to have good digestibility [19]. Bark of aspen (Populus tremuloides), which belong to the same genus as balsam poplar, was suggested as a good feed for goats [20]. ...
Article
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There is an urgent need to develop new strategies to minimize the environmental impact of animal production and support sustainability of food production and consumption. Feed additives have been for a long time used in animal nutrition to improve animal growth and performance as well as animal health. Balsam poplar plants (Populus balsamifera) is well known as a rich source of bioactive compounds with positive health effects, and might be used in agriculture as a feed additive for ruminants. The aim of the present study was to evaluate the effect of balsam poplar-based additives on growth and performance of fattening young bulls of Simmental breed. In the present study, we used 4 combinations of extract from balsam poplar buds or its components as a feed additives. The animals were given the supplements at the age of 15 months, 3 months before slaughter. The growth and slaughter characteristics of young bulls were studied. After the first and second month of feeding with dietary supplements, animals from the groups fed 10% balsam poplar buds extract and dry shredded balsam poplar buds had significantly higher live weight compared to the control animals fed a diet without any supplements (P < 0.05). At slaughter, group fed 10% balsam poplar buds extract had significantly higher live weight compared to control. Average daily gain was also greatest in that group. Major sensory as well as physical and chemical parameters were not affected by balsam poplar-based supplements (p > 0.05 for all) and were in line with regulatory meat hygiene requirements.
... Goat willow is thought to be so named due to the use of the tree as a browse source for goats, and has traditionally been used as a fodder for livestock (Austad and Hauge 2006) with organic matter digestibility similar to hay and grass silage (Musonda et al., 2009;Pitta et al., 2007). One of the limitations of using tree fodder as a feed is that nutritive value and digestibility peaks in spring and decreases through to autumn (McWilliam et al., 2005). ...
Article
Silvopastoral agroforestry, the integration of trees into livestock production systems, is an ancient practice with benefits to animal welfare and nutrition. Intensification of farming practices have reduced the presence of trees and hedgerows in the agricultural landscape. Environmental benefits coupled with improvements to ecological resilience and the long-term sustainability of farm productivity have led to a resurgence in interest in silvopastoral farming systems. The objective of this study was to investigate the nutritional composition and potential use of tree leaves as a supplementary fodder for ruminant livestock, with particular reference to sheep. Leaves (including petioles) were collected during spring (June) and autumn (September) from goat willow (Salix caprea), oak (Quercus spp) and alder (Alnus spp) from three sites in the UK. On the third site samples of ash (Fraxinus excelsior), beech (Fagus sylvatica), sweet chestnut (Castenea sativa) and sycamore (Acer pseudoplatanus) were also collected. Tree leaves were analysed to determine mineral content, dry matter (DM), crude protein (CP), modified acid detergent fibre (MADF) and metabolisable energy (ME) which were then compared to the nutritional requirements of grazing sheep (Ovis aries). Leaves from all tree species used in this study were able to exceed the dietary ME and CP concentration requirements (NRC) for growing lambs (40 kg lamb @ 150 g/d). Alder contained the most ME and CP of the studied species. There was no significant effect of season although CP was higher in spring than autumn for all tree species. Zinc and cobalt concentrations were found to be dependent on tree species with negligible site and season effects. All (NRC) sheep requirements of both elements were exceeded by willow, met by alder and not met by oak, willow exceeded these requirements for zinc and cobalt by approximately 3-6 and 10-15 fold respectively. Leaf selenium concentrations were site specific with site 1 almost able to meet maximal requirement, whilst all other sites (all tree species) were around the minimal requirement. To conclude, ME and CP concentrations of the tree leaves were generally within a requirement range to support adequate growth of lambs if leaves fed alone (not likely in practice). Selenium concentrations were site dependant, iodine was mainly season dependent with tree species effects for zinc and cobalt. The zinc and especially cobalt concentrations of willow leaves were sufficient to suggest that willow could be used as a bio-supplement when fed within a conventional grazing system, especially useful for growing lambs.
... Leguminózy obecně obsahují lignin, který se na rozdíl od trav rozpouští v alkalickém prostředí jen částečně, což je způsobeno větším podílem sta-bilních vazeb (MÍKA et al., 1997b). Stravitelností organické hmoty krmiv se zabývala řada dalších autorů (MADRID et al., 2002;McWILLIAM et al., 2004;SCHUBIGER et al., 2001 a další). ...
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The influence of the stage of maturity of alfalfa on the chemical composition and in sacco digestibility was studied in a laboratory experiment. Alfalfa plants were analysed in 8 vegetation stages harvested in regular intervals before the beginning of bud setting until the fall of blossoms. The contents of ni-trogenous substances, fat, crude fibre, ADF, NDF, Ca, P, Na, K and Mg were determined in the samples, and using the in sacco method also the organic matter digestibility in the rumen. Further we assessed the energy content and calculated the N-free extractives (BNLV) value. In some stages the chemical changes were monitored in the whole plant. It was discovered that during vegetation there was a statistically significant increase in the crude fibre content and in the ADF and NDF fractions and a reduction in nitrogenous substances. A strong negative correlation was detected between the stage of maturity of alfalfa and content of crude protein and net energy for lactation (r = -0.97 and r = -0.92, respectively). In the individual stages of vegetation the differences in the content of nitrogenous sub-stances, fibre and fat were statistically significant (P < 0.05). The statistically highest content of crude protein (28.97%) was detected in the first stage before bud setting and the lowest (11.97%) in the stage after the fall of blossoms. Later vegetation also had a stronger depressive effect on the content of fat and NEL. The organic matter digestibility (P < 0.05) was the lowest in alfalfa in the last stage of sam-pling (62.6%) when it reached a mere 85.99% of the digestibility at the beginning of bud setting. The highest organic matter digestibility (72.80%) was detected in a sample of young alfalfa prior to bud setting. In the experiment we confirmed a strong and negative correlation (r = -0.97) between the crude fibre content and organic matter digestibility. The correlation was also strong between the stage of maturity of alfalfa and the content of magnesium (Mg).
... On the other hand, additives, such as polyethylene glycol (PEG) or supplemental protein, can induce goats and lambs to increase intake of tannin-rich species (Petersen and Hill 1991;Silanikove et al. 1996;Gilboa et al. 2000;Landau et al. 2002;Villalba et al. 2002a, c). To our knowledge, no prior studies have examined the effects of feed supplementation on intake levels of sheep that have access to willow, a plant genus, which usually contains high levels of tannins (Palo 1984;McWilliam et al. 2005). ...
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Macronutrients and additives have been used to suppress or promote livestock intake of upland tannin-containing browse species, but to our knowledge this technique has not been applied to sheep that feed on tannin-rich species in riparian areas. The objective of this study was to determine the effect of four supplement regimes on coyote willow (Salix exigua) intake by sheep during the dormant and growing seasons. Twelve Western White Face lambs (48 kg ± 4.5 kg) were placed in individual pens and assigned to one of four treatments which consisted of a basal diet of sudangrass and supplements predicted to either suppress (whole corn or quebracho tannin) or promote (cottonseed meal or polyethylene glycol, PEG) willow intake. Each of the four supplements was tested with dormant and growing willow in a Latin rectangle design with three periods and six lambs per group. Basal diet (sudangrass) intake was not affected by either promoter nor suppressor treatments in either season. Cottonseed meal effectively promoted intake of willow compared to the control and PEG treatments (P< 0.05) in the dormant season. No difference was detected between the control, quebracho-tannin, and whole-corn treatments, although the latter tended to depress dormant-willow intake of lambs. None of the treatments altered intake of coyote willow in the growing-season trials. Protein and possibly corn-based supplements may be effective tools to manipulate sheep browsing levels of Salix exigua but need to be tested in a field setting before management strategies with supplementation can be applied.
... Willow and pasture samples of the diet selected were stored at −20 • C, freeze dried and ground to pass a 1 mm diameter sieve. Total N concentration was determined using the Dumas method (Leco Corporation, St. Joseph, Michigan, USA; and organic matter (OM) by ashing samples for 16 h at 550 • C. In vitro OM digestibility (OMD) was determined by the enzymatic method of Roughan and Holland (1977), using separate standard curves prepared from in vivo values for forages and willow fed to sheep (McWilliam et al., 2005a). Metabolisable energy (ME) was calculated as 16.3 × in vitro digestible OM/100 g DM (DOMD; Drew and Fennessy, 1980). ...
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A grazing experiment, conducted for 116 days from 19 January to 15 May in the late summer/autumn of 2006 at Massey University's Riverside dry-land Farm, near Masterton (New Zealand), compared effects of grazing willow (Salix spp.) fodder blocks or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture, during the pre-mating and mating periods, on gastrointestinal nematode parasite control and reproductive rates in 7-month old ewe hoggets. A rotational grazing system with 348 weaned Romney ewe hoggets was used, with 116 hoggets per treatment (control pasture with regular anthelmintic drenching, control pasture with trigger drenching and willow fodder blocks with trigger drenching). Hogget live weights (LW), dag scores (DS), faecal nematode egg counts (FEC) and reproductive rates at foetal ultrasound scanning, lambing, tail docking and weaning were measured. Total N concentration (35g/kg dry matter; DM), organic matter digestibility (OMD; 0.68) and metabolisable energy (ME; 10MJ/kgDM) were similar for fodder block pasture and control pasture; the selected tree fodder had lower concentrations of N (24g/kgDM) and was higher in OMD (0.74) and ME (10.4MJ/kgDM). Tree fodder contained higher concentrations of condensed tannins (CT; 22.9g/kg versus 1.6g/kgDM) than control pasture and herbage in willow fodder blocks. Grazing willow fodder blocks increased LW gain (approximately 97g/day versus 86g/day) and increased reproductive rate corrected to equal LW by approximately 17lambs/100 hoggets mated, due to increases in both oestrus activity and conception rates (hoggets pregnant/100 mated). Calculated daily DM (1.41kg) and ME (14MJ) intakes were similar in all groups. Calculated daily CT intake (6.0g versus 2.1g) and CT intake/100g CP intake (2.2g versus 0.7g) were higher for willow fodder block hoggets than for the control pasture groups, and this may have increased the flow of undegraded dietary protein to the small intestine leading to increases in reproductive rates of this group. Grazing willow fodder blocks failed to reduce the number of anthelmintic drenches (3) needed to maintain FEC below 1000eggs/g wet faeces, but was successful in reducing DS compared to grazing conventional ryegrass/white clover pastures. Grazing willow fodder blocks can be beneficial in sustainable farming systems since tree fodder can sustain growth rates, increase reproductive rates and reduce dag formation in parasitized hoggets.
... Sodium sulfite was not added to the ND. In vitro OM digestibility (OMD) was determined by the enzymatic method of Roughan and Holland (1977), using separate standard curves prepared from in vivo values for forages and for willow fed as the sole diet to sheep in indoor digestibility studies (McWilliam et al., 2005c). The ME in the diet select samples was calculated as 16.3 × digestible OM/100 g DM (DOMD; Drew and Fennessy, 1980). ...
Article
Effects of supplementing willow stem cuttings to ewes grazing drought pastures upon plasma amino acid (AA) concentrations was studied on Massey University's Riverside Farm, near Masteron, on the East Coast of New Zealand. Ewes of similar age and weight (i.e., 59.0±2.22kg) were assigned to two groups of 7 each, either with (supplemented) or without (control) supplementation of willow, and experimental grazing was carried for 10 weeks from early February until mid April of 2005. Live weight (LW) was recorded fortnightly and body condition score (BCS) was monthly. Blood samples for quantification of plasma amino acids were collected at week 5 and 10. Both groups had a similar pre-grazing pasture mass (i.e., 2000kg of dry matter/ha) and dead matter content (0.80) with the diet selected by the ewes containing a metabolisable energy (ME) of 8.3MJ/kg DM, which is typical of drought conditions. The willow was readily eaten, with intake averaging 0.26kg DM/ewe/d. Willow was of higher ME content than short drought pasture (i.e., 10.1 versus 8.4MJ/kg DM) and contained condensed tannins at 40.8±1.97g/kg DM. Both groups of ewes lost live weight at about 50g/d. Plasma concentration of 3-methyl histidine (88 versus 127μmol/L) at week 5 and non-essential amino acids (1082 versus 1417μmol/L) at week 5 and (1155 versus 1324μmol/L) at week 10, were substantially lower (P
... Aspen stand decline is spatially and temporally heterogeneous with some regions realizing aspen persistence (Kulakowski et al. 2004(Kulakowski et al. , 2006Binkley 2008;Sankey 2008). There are also regions where aspen is used as a forage base and livestock grazing is used to manage aspen (Semiadi et al. 1995;McWilliam et al. 2005). ...
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There is concern over the decline of aspen and the lack of successful regeneration due to excessive browsing of aspen suckers by cattle and other wild and domestic ungulates. We conducted a 2-yr study on Lassen National Forest, California, to aid development of cattle grazing strategies to enhance aspen regeneration. We evaluated seasonal biomass, nutritional quality, and utilization by cattle of aspen suckers, aspen herbaceous understory vegetation, and meadow herbaceous vegetation within six aspen-meadow complexes. Aspen suckers had greater nutritional quality compared to aspen understory and meadow vegetation regardless of season or year. Nutritional quality declined with season in all three vegetation types. Early-growing season foraging by cattle focused on meadow and aspen understory vegetation. Mid-growing season decreases in meadow and aspen understory nutritional quality coincided with a marked increase in utilization of aspen suckers. By late-growing season, utilization on aspen suckers was significantly greater than aspen understory or meadow vegetation. Managers can use early-growing season grazing to reduce aspen consumption by cattle, set stocking rates so that adequate herbaceous vegetation is available throughout the growing season, provide nutritional supplements to reduce demand for nutritious aspen suckers, construct protective fencing, and implement grazing systems that insure years with mid- and late-growing season rest from heavy browsing.
... Total nitrogen (N) concentration was determined using the Dumas method (Leco CNS 2000 analyser, Model 602 600 200, USA). In vitro OMD was determined by the Roughan and Holland (1977) enzymatic method, using separate standard curves prepared from in vivo values for forages and willow fed to sheep (McWilliam et al., 2005a). ME content was calculated as 16.3 × in vitro digestible organic matter/100 g DM (DOMD; Drew and Fennessy, 1980). ...
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A grazing experiment was conducted in the East Coast region of the North Island of New Zealand with 180 weaned ram lambs grazing typical dryland summer pasture versus grazing willow (Salix spp.) fodder blocks. The experiment was conducted over a 14-week period with three forage treatments, comprising control pasture, restricted access to willow fodder blocks and full access to willow fodder blocks, with each treatment further divided into undrenched and regularly anthelmintic drenched groups. Live weight (LW) and dag score (DS) were recorded at 14-day intervals. Fifteen lambs in both drenched and undrenched groups were regularly monitored for faecal nematode egg counts (FEC) and nematode larval cultures (LC). Carcase weight (CW; kg) and LW (kg) data was collected from 12 additional lambs slaughtered at the beginning of the experiment to predict initial CW of the experimental lambs from their initial LW. At the end of the grazing experiment, all lambs were slaughtered in a commercial abattoir; CW and GR (fatness) was recorded. The abomasum and small and large intestines were collected from 10 lambs from each undrenched group for estimation of total worm nematode numbers. Organic matter digestibility (OMD; 0.65) and metabolisable energy (ME; 9.7MJ/kgDM) content were similar for fodder block pasture and control pasture; the selected tree fodder had a higher OMD (0.71) and ME concentration (10.7MJ/kgDM). Herbage condensed tannin (CT) concentration in willow fodder blocks was consistently higher than the trace CT levels detected in control pasture (14.5g/kgDM versus 6.2g/kgDM); tree fodder contained higher concentrations of CT (45.5g/kgDM). Undrenched lambs grazing either control pasture or willow fodder blocks had lower LW gain (LWG) and CW gain (CWG) than lambs regularly drenched with anthelmintic (P
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Complex interactions between livestock, trees and pasture occur in silvopastoral systems. Between trees and pasture, competition for soil resources (nutrients and water) occurs, becoming especially relevant when one of them is in scarce supply. Trees reduce light and water reaching the understorey layers according to tree density and canopy size. However, they may ameliorate extreme climatological features (reducing wind speed and evapotranspiration, and alleviating extreme temperatures), and improve soil properties, for example, deciduous tree litter may contribute to increased pH and soil nutrient concentrations. During tree establishment, there are generally negligible effects on pasture, irrespective of tree type. However, there is a decline in pasture production and nutritive value under shade with increasing tree age and higher stand density. Under the same conditions, deciduous trees affect pasture later (extinction point of pasture occurs at 85% of canopy closure) than evergreen trees (about 67% for Pinus radiata D. Don). This is mainly because deciduous trees have a leafless period that enables pasture recovery, and their litter smothers pasture less intensely because of its relatively fast decomposition. Silvopastoral studies conducted in New Zealand are reviewed to discuss these effects, and differences in the effects of evergreen and deciduous trees are shown using the examples of P. radiata, and Populus and Salix spp. respectively, which exist in many temperate countries. Future research needs are outlined.
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A grazing experiment, conducted for 71 days from 31 January to 12 April in the late summer/autumn of 2001 at Massey University’s Riverside Farm, in Masterton (New Zealand), compared the effect of poplar supplementation (Populus deltoides × nigra, clone Veronese), during mating, on ewe production and reproduction when grazing low quality drought pasture. A rotational grazing system with 300 mixed age Romney ewes ( ) was used, with 100 ewes per treatment. All ewes were offered 0.70 kg dry matter (DM)/day of low quality pasture, containing 84% dead matter, with pre- and post-grazing pasture masses of 1040 and 531 kg DM/ha. Ewes were randomly allocated to three treatment groups, being: high supplementation, low supplementation and control. The high and low treatment groups were offered 1.50 kg/ewe/day (fresh) and 0.75 kg/ewe/day (fresh) poplar cuttings, respectively. The effect of poplar supplementation on liveweight (LW) and body condition score (BCS) change; reproductive rate at pregnancy scanning, lambing, docking and weaning; and wool production and staple length was measured. The poplar diet selected contained 22 g/kg DM of phenolic glycosides and higher levels of nitrogen (N; 28.4 g/kg DM versus 17.8 g/kg DM) and condensed tannin (CT; 7.0 g/kg DM versus 1.5 g/kg DM) and was of higher organic matter digestibility (0.66 versus 0.52) than the pasture diet selected. Voluntary DM intake of poplar progressively increased with time of supplementary feeding for both treatments (P<0.01), due to increases in both DM content and the diameter of stem consumed. Reproductive rate was low in the control ewes (121 lambs born/100 ewes mated), and poplar supplementation increased ewe reproductive rate by approximately 20 and 30% units for the low and high treatment groups, respectively, compared to the control group, at scanning, lambing, docking and weaning. The increase in reproductive rate in supplemented ewes was due to increases in both conception rate and fecundity, with a higher proportion of pregnant ewes, and a higher proportion of multiple pregnancies, in the supplemented groups. Ewes in the high and low treatments lost slightly less LW (−67 and −71 g/day versus −82 g/day; P<0.05) and BCS (−0.78 and −1.27 units versus −1.31 units; P<0.05) as a result of poplar supplementation, but these differences did not occur in the post-treatment period. There were no treatment effects on wool production or staple length, and only small treatment effects on the LW of single- and twin-born lambs at birth and weaning. Poplar cuttings are a beneficial supplement for increasing the reproductive rate of ewes grazing drought pasture during the pre-mating and mating periods. Poplar supplementation increased intakes of DM, metabolisable energy (ME) and crude protein (CP), and increased the estimated g CP/MJ ME eaten during the mating period. Increased concentrations of total N, CT and water-soluble carbohydrate (WSC) in the diet of supplemented ewes would also be likely to increase outputs of undegradable dietary protein and microbial protein from the rumen, per unit of CP consumed. A combination of these mechanisms, especially the likely increased absorption of protein, probably explains the increased ewe reproductive rate from poplar supplementation.
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An 87 days grazing experiment, in the late summer/autumn of 2002 in Masterton (New Zealand), compared the effects of willow (Salix) versus poplar (Populus) supplementation (1.3kg fresh/ewe/day), during mating, on reproductive performance and wool production in ewes grazing low quality drought pasture. A rotational grazing system with 285 mixed age Romney ewes (55.2±0.54kg) was used, with 95 ewes per treatment (control, willow-supplemented and poplar-supplemented). All ewes were offered about 0.70kg dry matter (DM)/day of low quality pasture, containing 62% dead matter, with pre- and post-grazing pasture masses of 941 and 456kgDM/ha. Pasture consumed was typical of drought pasture; 571g neutral detergent fibre (NDF)/kgDM, 0.540 organic matter digestibility (OMD). Both the willow and poplar diets selected were higher in OMD and metabolisable energy (ME) and had a higher ratio of readily fermentable carbohydrate (CHO) to structural CHO, than the pasture diet selected. Willow contained higher concentrations of condensed tannin (CT; 52g/kg versus 19g/kg; P
Article
A procedure was developed for extraction of ‘free’ condensed tannins (CT) using a mixture of acetone/water/diethyl ether (4.7:2.0:3.3), followed by extraction of protein-bound and fibre-bound CT using boiling sodium dodecyl sulphate containing 2-mercaptoethanol (SDS). CT concentrations in all three fractions were determined by a modified butanol-HCI procedure. Separate standard curves using purified CT in water or SDS solution were utilised for analysis of extractable CT (water standards) and protein-bound and fibre-bound CT (SDS standards). The method accurately predicted the concentration of CT added to forage extracts. CT extractable in acetone/water/diethyl ether comprised, on average. 68% of total CT in a range of freeze dried forage legume samples, with most of the remainder being bound to protein. When total CT concentration was low (0.6-3.0% DM), a lower proportion was extractable (33-35%). In protein concentrate meals containing CT, the extractable, protein-bound and fibre-bound components comprised 15, 60 and 25% respectively of total CT. Total CT concentration in the forages Lotus corniculatus and Coronilla varia was considered appropriate for ruminant nutrition (2.1 and 3.0% DM). whilst CT concentration in the forage of Dorycnium spp (13–19% DM) was more suitable for soil conservation purposes. The substantial CT concentration in cottonseed meal (1.6% DM) may be involved in the high resistance of proteins in this product to ruminal degradation. CT concentration was indistinguishable from zero in perennial ryegrass forage, in barley and triticale grains and in soya bean meal (0.1% DM).
Article
The effect of condensed tannins (CT) on the nutritive value of temperate forages and on the health of grazing ruminant animals is reviewed. The CT bind with proteins and other entities mainly by hydrophobic and hydrogen bonding in a pH-reversible manner, which is influenced by the structure and molecular weights of both the CT and the proteins. These reactions can be used to reduce the degradation of forage proteins in the rumen, without reducing the amount of microbial protein synthesized. CT in Birdsfoot trefoil (Lotus corniculatus) and sulla (Hedysarum coronarium) can be used to increase the absorption of essential amino acids (EAA) from the small intestine, but CT in Big trefoil (Lotus pedunculatus) and sainfoin (Onobrychis coronarium) produce no net increase; differences in CT structure and reactivity probably explain these differences.
Article
A 95-day rotational grazing experiment was conducted in the summer of 2002/2003 under dryland farming conditions to compare effects of grazing Lotus corniculatus L. (Birdsfoot trefoil; cv. Grasslands Goldie) and perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture on body growth and dynamics of nematode parasite infection in Suffolk×Romney weaned lambs fed ad libitum. Half of the lambs (n=30), grazing either L. corniculatus or pasture received oral anthelmintic at the start and at monthly intervals (i.e., regular-drenched groups), whilst the remaining 30 lambs in each treatment only received oral anthelmintic when mean faecal nematode egg counts (FECs) exceeded 1000eggs/g wet faeces (i.e., trigger-drenched groups). This only occurred on day 58 for both groups. Trigger and regular-drenched lambs grazed separate areas. Total condensed tannin (CT) concentration in the diet selected was 31–40g CT/kg DM for L. corniculatus, with only trace amounts in pasture. In vitro organic matter (OM) digestibility (OMD), digestible OM in dry matter (DOMD), and metabolisable energy (ME) concentration were higher for L. corniculatus versus pasture and declined less under drought conditions versus grass-based pasture. Regular-drenched lambs grazing L. corniculatus had higher liveweight gain (LWG; 298g/day) and carcass weight gain (133g/day) than all other groups, whilst trigger-drenched lambs grazing L. corniculatus had higher LWG (228g/day) and carcass gain (99g/day) versus regular-drenched (200; 66g/day) and trigger-drenched (187; 63g/day) lambs grazing pasture. Carcass fatness was lower for trigger-drenched lambs versus regular-drenched lambs, when fed either L. corniculatus or pasture. Dag score was consistently lower for regular-drenched lambs grazing L. corniculatus versus pasture; trigger-drenched lambs showed similar effects up to day 48, with no differences between the groups thereafter. Regular anthelmintic treatment maintained FECs at low values, while parasitised grazed lambs on L. corniculatus tended to have higher FECs than pasture fed lambs. Relative to trigger-drenched lambs that grazed pasture, grazing L. corniculatus reduced worm burdens at slaughter of Haemochus contortus, Teladosargia spp., Nematodirus spp. and Cooperia spp., but higher burdens of Trichostrongylus spp., Chabertia ovina, Oesophagostonum spp. and Trichuris ovis ocurred in L. corniculatus fed lambs. Grazing Lotus corniculatus L. (Birdsfoot trefoil; cv. Grasslands Goldie) under dryland farming conditions can increase growth of weaned lambs, whilst reducing reliance on anthelmintic drenches to control parasites. These effects are possibly due to increased metabolisable protein supply, from the protein binding action of CT, enabling the lambs to grow faster when carrying a parasite burden, and to L. corniculatus better maintaining its high ME value under drought conditions. Mechanisms for the action of CT are discussed.
Article
Two grazing experiments were conducted over 9.5-month periods of 2001 and 2002 at Massey University's Riverside dryland farm, in the Wairarapa, New Zealand. Dry conditions occur during the summer/autumn and were more severe in Experiment 1 than in Experiment 2. The experiments compared effects of grazing ewes on Lotus corniculatus L. (birdsfoot trefoil; cv. Grasslands Goldie) versus perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture for 9 weeks (Experiment 1) and 11 weeks (Experiment 2) during late summer/autumn, including the mating period. Experiment 2 also investigated the length of time (days) that ewes need to graze L. corniculatus before mating to maximise reproductive performance.
Article
Two grazing experiments were conducted for 12 and 13 weeks, respectively, over the spring periods of 2000 and 2001 at Massey University's Riverside farm in the Wairarapa (New Zealand) to compare effects of grazing Lotus corniculatus (birdsfoot trefoil; cv. Grasslands Goldie) or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) dominant pasture during lactation on ewe and lamb live weight (LW), wool production, faecal nematode egg counts (FEC) and dag score. Ewes and their lambs (mainly twins) were rotationally grazed on lotus or pasture (n = 50) without any anthelminitc treatment at a herbage allowance of 6.5 and 8.0kg green DM/ewe/days for Experiments 1 and 2, respectively. Total condensed tannins (CT) concentration in the diet selected was 24 to 27g CT/kg DM for lotus and 1.4 to 1.5g CT/kg DM for pasture. In vitro organic matter digestibility and metabolisable energy (ME) concentration were higher for lotus than for pasture in both experiments, whilst the concentrations of neutral detergent fibre (NDF) was lower in lotus than in pasture. The LW gain, weaning LW and wool production were consistently higher (P < 0.001) for lambs grazing lotus, in both Experiment 1 (258 versus 189g/days; 36.1 versus 30.1 and 1.17 versus 0.98kg) and in Experiment 2 (247 versus 162g/days; 31.8 versus 24.1 and 1.17 versus 0.81kg), respectively. Ewe and lamb dag score were strongly and positively correlated with dag weight (P < 0.001), and generally increased with time in sheep grazing pasture; while grazing on lotus consistently reduced dag score. FEC in ewes grazing pasture showed a post-parturient rise (PPR) following lambing, whilst ewes grazing lotus had a reduced PPR in FEC. Up to day 70, FEC in lambs grazing lotus was lower than that for lambs grazing pasture, but between day 70 and the end of both experiments (approximately day 90), FEC in lambs grazing lotus increased to similar values as for pasture-fed lambs. FEC was not correlated with dag score or dag weight in ewes or lambs grazing pasture, but these indices were weakly and positively correlated in ewes and lambs grazing lotus, suggesting that lowering FEC on lotus also reduced dag formation. Under dryland farming conditions, the use of Lotus corniculatus (cv. Grasslands Goldie) during the spring/early summer lactation period can be used to increase lamb growth and wool production, whilst eliminating the need for pre-lambing anthelmintic drenching and, probably, reducing the amount of insecticide needed to control flystrike. These effects are probably due to the CT in lotus reducing rumen protein degradability and controlling internal parasites, and to the higher digestibility and voluntary feed intake (VFI) of lotus compared to perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. The absence of endophyte in lotus may also have contributed to these effects.
Article
This study was undertaken to investigate the effect of willow supplementation of beef cattle grazing dry, sparse summer pastures in the Wairarapa district of New Zealand for 81 days. Three groups each of 15 beef cows were allocated to control, low willow supplementation and high willow supplementation. Liveweight (LW) was measured throughout the experimental period. The chemical composition and nutritive value of the willow and pasture eaten, diameter of willow eaten and willow dry matter (DM) eaten per day were also measured.Post-grazing residual DM was approximately 1700 and 850kg/ha in the first and second half of the experiment; dead matter content of the feed offered was respectively 0.65 and 0.35 of total DM. Diet selected for willow and drought pasture contained respectively 9.3 and 8.4MJ ME/kg DM, 18 and 24gN/kg DM, and 27 and 1g condensed tannin/kg DM. This defined the pasture as sparse and of low quality, typical of drought conditions.Willow supplementation of cattle grazing dry, sparse summer pasture reduced LW loss (−0.36 to −0.45kg per day), when compared with a control group grazing similar pasture (−0.64kg per day). The treatment×time interaction was significant (P0.10). The diameter of the willow eaten continuously increased over the experimental period (P
Article
Voluntary intake and apparent digestibility of tree willow (Salix matsudana Χ alba) and of osier willow ( Salix viminalis ) were measured with male sheep and goats and voluntary intake only with male deer. Both willow species had been selected for extremely rapid growth, and were grown in coppices on high fertility soil. In a first experiment spring primary growth of both willows was fed to sheep, goats and deer in early summer, whilst in a second experiment summer regrowth (i.e. secondary growth) of osier willow was fed to sheep and goats in autumn. Although the ratio of readily fermentable to structural carbohydrate (0·51–0·70) and total N concentration (18–24 g/kg D.M.) in primary growth of the willows was less than normally found in high quality fresh temperate forages, the values were similar to those of many dried forages normally used as supplements. Averaged over sheep and goats, voluntary intake of digestible D.M. was 22% less for osier than for tree willow, this being associated with higher concentrations of lignin (197 ν 182 g/kg D.M.) and of condensed tannin (66 ν 29 g/kg D.M.) in the osier willow. The lower digestible dry-matter intake was attributable to both lower voluntary intakes and lower digestibility of the D.M. (0·57 ν 0·64). Both voluntary intake and apparent digestibility of secondary growth willow were lower than that of primary growth. When expressed as functions of the amount required for maintenance, voluntary metabolizable energy intake of goats was approximately double that of sheep, both for primary growth (2·2 ν 1·1) and for secondary growth (1·8 ν. 0·7) willow. This was attributable to consistently higher voluntary D.M. intakes/kg W0'6 by goats, and to a trend for higher digestibility than sheep, which attained significance in Expt 2 but not in Expt 1. The ratios of dry-matter intake/kg W075 per day for sheep: deer: goats fed primary growth willow were 1·0:1·5:1·9, with deer thus being intermediate between the other two species. There were no differences in voluntary intake (g/kg W 0·75 per day) of sheep, goats and deer fed a high quality lucerne hay. It was concluded that willows grown during spring and summer could adequately be used as supplementary feed during summer droughts and that willow could be used most effectively if fed to goats, followed by deer, with sheep being the least efficient. Tree willow is a preferred choice to the osier willow used here, and it was further concluded that like Lotus pedunculatus , high concentrations of lignin and condensed tannin, both of which are produced by the same biochemical pathway, are likely to be limiting nutritive value of the more leafy osier willow.
Article
A series of subtropical grasses and temperate grasses, herbs and legumes were analysed for the presence of extractable and bound condensed tannin (CT) using colorimetric analysis by the butanol–HCl method. Condensed tannins are routinely purified using affinity chromatography with Sephadex LH-20 as a matrix. Therefore, Sephadex LH-20 extracts were further analysed for the presence of CT by 13C nuclear magnetic resonance, for anthocyanidin formation after butanol–HCl treatment and for their ability to precipitate ribulose-1,5-bisphosphate carboxylase (Rubisco) protein from lucerne, at pH 7·0. Criteria for the presence or absence of CT were defined. Trace amounts of CT (0·2–2·5 g kg−1 dry matter; DM) were identified and confirmed in summer grass (Digiteria sanguinalis), perennial ryegrass (Lolium perenne) and red clover (Trifolium pretense), with chicory (Chicorium intybus), lucerne (Medicago sativa) and plantain (Plantago lanceolata) identified as probably containing CT. It was concluded that the subtropical grasses kikuyu (Pennisetum clandestinum), paspalum (Paspalum diatatum), smooth witchgrass (Panicum dichotomiflorum) and crowfoot (Eleusine indica) and the temperate grass, Yorkshire fog (Holcus lanatus) probably did not contain CT. Analysis of the extractable fractions by vanillin–HCl gave higher values for CT than analysis by butanol–HCl and wrongly identified some forages as containing trace levels of CT. It was concluded that vanillin–HCl was not specific enough for the detection of trace levels of CT in forages. These results raise the possibility of plant selection programmes to increase the level of CT in grazed forages to approximately 5 g kg−1 DM, the suggested minimum level required to prevent bloat in cattle and to increase wool growth in sheep. It is suggested that this be considered for perennial ryegrass, chicory, red clover and lucerne.
Article
A potent cellulase solution was prepared from culture filtrates of an artificially-produced mutant of Trichoderma species. The filtrates were diluted to provide a standardised, simulated rumen liquor which was then used to study the correlation between cellulase digestibility and in-vivo digestibility of a range of plant materials. Cell walls of whole, dried plant material were either not attacked by the cellulase or were attacked only very slowly, but cell walls isolated by neutral-detergent extraction were readily hydrolysed. Cellulase digestibility, defined as the percentage of whole, dry plant material solubilised by neutral-detergent extraction followed by exhaustive hydrolysis with standardised cellulase, was highly correlated with in-vivo dry matter digestibility (DMD) (r=0.98) and predicted that parameter with reasonable accuracy (r.s.d., residual standard deviation = 2.83). The form of the regression equation was in-vivo DMD = 0.98 × cellulase solubility - 10.12, suggesting that the same factors limited cellulase and in-vivo digestibility. The method was simple and reliable and results were known within 48 h.
Article
The phenolic glucosides of seven willow species with different glucoside patterns were extracted, purified and analysed by gas-liquid (GLC) and high-performance liquid chromatography (HPLC). Two sample preparation methods were used. It was shown that the HPLC and GLC methods give comparable qualitative and quantitative results for the phenolic glucoside contents of the tested willows. Consequently, both methods can be used for species-specific screening of the glucoside patterns of Salicaceae species.
Article
There is a need to standardize the NDF procedure. Procedures have varied because of the use of different amylases in attempts to remove starch interference. The original Bacillus subtilis enzyme Type IIIA (XIA) no longer is available and has been replaced by a less effective enzyme. For fiber work, a new enzyme has received AOAC approval and is rapidly displacing other amylases in analytical work. This enzyme is available from Sigma (Number A3306; Sigma Chemical Co., St. Louis, MO). The original publications for NDF and ADF (43, 53) and the Agricultural Handbook 379 (14) are obsolete and of historical interest only. Up to date procedures should be followed. Triethylene glycol has replaced 2-ethoxyethanol because of reported toxicity. Considerable development in regard to fiber methods has occurred over the past 5 yr because of a redefinition of dietary fiber for man and monogastric animals that includes lignin and all polysaccharides resistant to mammalian digestive enzymes. In addition to NDF, new improved methods for total dietary fiber and nonstarch polysaccharides including pectin and beta-glucans now are available. The latter are also of interest in rumen fermentation. Unlike starch, their fermentations are like that of cellulose but faster and yield no lactic acid. Physical and biological properties of carbohydrate fractions are more important than their intrinsic composition.
Article
When allowed to select between macronutrients in a 1-h-a-day meal paradigm, Zucker rats consume 20-80% of their total caloric intake as fat. If they receive an intraperitoneal injection of DHEA 2 h before such a test meal, they consume fewer total calories. The magnitude of this effect on each macronutrient depends upon the animal's initial preference for fat; the higher the initial fat preference, the more profound is the decrease in caloric intake and the more pronounced the effect on fat consumption. Doses as low as 25 mg DHEA/kg body weight are effective. Lean Zucker rats that prefer to consume a high-fat diet have higher epinephrine and dopamine levels in select regions of the hypothalamus known to control food intake. Administration of DHEA to such animals 2 h before decapitation reduces the content of norepinephrine and these monoamines to levels that mimic the values found in the low-fat-preferring animals. It is hypothesized that exogenous DHEA causes the acute release of norepinephrine, epinephrine, and dopamine in select regions of the hypothalamus, and this release causes a decrease in food intake, particularly fat.
Supplementary Feeding, New Zealand Society of Animal Production Occasional Publication no 7
  • Drew
Drew KR and Fennessy PF, Supplementary Feeding, New Zealand Society of Animal Production Occasional Publication no 7. AgResearch Invermay, Mosgiel, New Zealand. (1980).
Pasture as a nutrient source
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Waghorn GC and Barry TN, Pasture as a nutrient source, in Livestock Feeding on Pasture, Ed by Nicol AM. New Zealand Society of Animal Production Occasional Publication no 10, Chap 2, pp 21–37 (1987).
The effect on sheep reproduction of grazing coppiced willows during drought
  • Dw Pitta
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17 Pitta DW, Barry TN, López-Villalobos N and Kemp PD, The effect on sheep reproduction of grazing coppiced willows during drought. Proc NZ Soc Anim Prod, in press (2004).
Pasture as a nutrient source New Zealand Society of Animal Production Occasional Publication no 10
  • Gc Waghorn
  • Tn Barry
Waghorn GC and Barry TN, Pasture as a nutrient source, in Livestock Feeding on Pasture, Ed by Nicol AM. New Zealand Society of Animal Production Occasional Publication no 10, Chap 2, pp 21-37 (1987).
Practical tree fodder experience during drought, in Using Trees on Farms Grassland Research and Practice Series no 10
  • Ag Olsen
  • Jfl Charlton
Olsen AG and Charlton JFL, Practical tree fodder experience during drought, in Using Trees on Farms, Ed by Charlton JFL. Grassland Research and Practice Series no 10. New Zealand Grassland Association, Wellington, pp 17-22 (2003).
Farmer experience with tree fodder, in Using Trees on Farms Grassland Research and Practice Series no 10
  • Jfl Charlton
Charlton JFL, Farmer experience with tree fodder, in Using Trees on Farms, Ed by Charlton JFL. Grassland Research and Practice Series no 10. New Zealand Grassland Association, Wellington, pp 7-16 (2003).
New Zealand Society of Animal Production Occasional Publication no 7
  • Kr Drew
  • Pf Fennessy
  • Supplementary Feeding
14 Drew KR and Fennessy PF, Supplementary Feeding, New Zealand Society of Animal Production Occasional Publication no 7. AgResearch Invermay, Mosgiel, New Zealand. (1980).
The effect on sheep reproduction of grazing coppiced willows during drought
  • Pitta