[Show abstract][Hide abstract] ABSTRACT: Understanding how weed communities assemble as a function of biotic and abiotic filters and transform through time has important implications for the sustainable management of agronomic systems. In a three-year study, we evaluated weed community responses to lucerne (Medicago sativa, perennial) vs. continuous spring wheat (Triticum aestivum, annual, CSW) and weed management practices where weeds in the CSW system were managed with three contrasting approaches (herbicide, tillage or sheep grazing). Our results indicated no differences in weed diversity between the perennial and annual crops or across the different management practices in CSW. However, there were differences in weed community composition. Lucerne, with the exception of the establishing year, impeded the growth and reproduction of several annual weeds, including Amaranthus retroflexus, Thlaspi arvense, Lamium amplexicaule and Chenopodium album, but favoured perennial broad-leaved weeds such as Taraxacum officinale and Cirsium arvense. The replacement of herbicide treatments in pre-plant and post-harvest in CSW with soil tillage or sheep grazing selected for different weed communities beyond the second year of establishment. The weed species driving the differences in CSW systems were Androsace occidentalis, more common in CSW managed chemically; Asperugo procumbens, more common in CSW managed with tillage; and T. officinale and Lactuca serriola, more common in CSW managed with sheep grazing. Understanding how cropping systems modify weed communities is a necessary step to shift from reactive weed control programmes to predictive management strategies.
Weed Research 04/2015; 55(4). DOI:10.1111/wre.12155 · 1.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previous research has reported high variation in intake of self-fed protein and/or energy supplements by individual animals, however little is known about variation in consumption of mineral supplements. Sixty mature range ewes (non-pregnant, non-lactating) were used in a completely randomized design repeated 2 years to determine if feeding method of intercropped field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) forage (swath grazed or fed as hay in confinement) affected individual ewe mineral consumption. Thirty ewes were allocated to 3 confinement pens (10 ewes/pen) and 30 ewes were allocated to 3 grazing plots (10 ewes/plot). Ewes had ad libitum access to feed, water, and a mineral supplement containing 1% titanium dioxide as an external marker. Forage dry matter intake (DMI) was calculated using estimates of fecal output, and in vitro 48-h forage DM digestibility. Ewe supplement intake was determined from fecal and supplement Ti concentrations, and fecal output. Forage and mineral intakes were analyzed using ewe as the experimental unit, and plot or pen as the experimental unit for intake variation. A year x treatment interaction (P < 0.01) existed for DM forage and mineral intake. Ewes in confinement consumed more forage DM than grazing ewes in 2010, but less than grazing ewes in 2011. Mean mineral intake was highest (P < 0.01) by grazing ewes in 2011 and 2010 (average 69 g/day), intermediate by confinement ewes in 2010 (57 g/day), and lowest by confinement ewes in 2011 (31 g/day). A year x treatment interaction (P = 0.05) existed for mineral intake CV which was higher (P = 0.04) for confinement ewes in 2011 (67 vs. 34%), but was not different (P > 0.05) between treatments in 2010. In this study, variation in individual ewe intake of mineral supplement was large in both grazing ewes and ewes fed hay in confinement.
[Show abstract][Hide abstract] ABSTRACT: Crop diversification and integration of livestock into cropping systems may improve the economic and environmental sustainability of agricultural systems. However, few studies have examined the integration of these practices in the semiarid areas of the Northern Great Plains (NGP). A 3-yr experiment was conducted near Bozeman, MT, to compare the effects of crop rotation diversity and weed management practices imposed during fallow periods [sheep (Ovis aries) grazing, reduced tillage, and conventional tillage] on spring wheat (Triticum aestivum L.) yields and weed pressure. Management treatments were applied to replicated whole plots, within which the split-plots received crop rotation treatments [continuous spring wheat (CSW) and a 3-yr rotation of annual forage, fallow, and spring wheat, where each phase was present in each year]. In the initial 2 yr, the realized rotational treatments were wheat–fallow and CSW. In the final year, wheat was grown following all phases of the diversified rotation. Yields were similar among management treatments within the wheat–fallow and CSW rotations. Weed pressure was generally low but perennial weeds were more abundant in grazing-managed, wheat–fallow systems. The integration of livestock into the annual hay crop–fallow–spring wheat rotation was associated with a nearly 30-fold increase in weed pressure and a yield reduction of 51.2% compared to conventional management. The results suggest that although targeted sheep grazing is a viable alternative to conventional fallow management in CSW and wheat– fallow rotations, successful integration of livestock in diversified cropping systems requires more effective weed management practices.
[Show abstract][Hide abstract] ABSTRACT: Sheep (Ovis aries L.) grazing, a costeffective
method of weed control compared to herbicide
application and tillage, may influence N cycling
by consuming crop residue and weeds and returning N
through feces and urine to the soil. The objective of
this experiment was to evaluate the effect of sheep
grazing compared to tillage and herbicide application
for weed control on soil particulate and active soil N
fractions in dryland cropping systems. Our hypothesis
was that sheep grazing used for weed control would
increase particulate and active soil N fractions compared
to tillage and herbicide application. Soil samples
collected at the 0–30 cm depth from a Blackmore silt
loam were analyzed for particulate organic N (PON),
microbial biomass N (MBN), and potential N mineralization
(PNM) under dryland cropping systems from
2009 to 2011 in southwestern Montana, USA.
Treatments were three weed management practices
[sheep grazing (grazing), herbicide application (chemical),
and tillage (mechanical)] as the main plot and
two cropping sequences [continuous spring wheat
(Triticum aestivum L.; CSW) and spring wheat–pea
(Pisum sativum L.)/barley (Hordeum vulgare L.)
mixture hay–fallow; W–P/B–F] as the split-plot factor
arranged in randomized complete block with three
replications. The PON and MBN at 0–30 cm were
greater in the chemical or mechanical than the grazing
treatment with CSW. The PNM at 15–30 cm was
greater in the chemical or mechanical than the grazing
treatment in 2009 and 2011 and at 5–15 cm was
greater with W–P/B–F than CSW in 2010. From 2009
to 2011, PON at 0–30 cm and PNM at 15–30 cm
reduced from 2 to 580 kg N ha-1 year-1 in the
grazing and chemical treatments, but the rate varied
from -400 to 2 kg N ha-1 year-1 in the mechanical
treatment. Lower amount of labile than nonlabile
organic matter returned to the soil through feces and
urine probably reduced soil active and coarse organic
matter N fractions with sheep grazing compared to
herbicide application and tillage for weed control.
Reduction in the rate of decline in N fractions from
2009 to 2011 compared to the herbicide application
treatment, however, suggests that sheep grazing may
stabilize N fractions in the long-term if the intensity of
grazing is reduced. Animal grazing may reduce soil N
fractions in annual cropping systems in contrast to
known increased fractions in perennial cropping
[Show abstract][Hide abstract] ABSTRACT: The two predominant systems for weed management in summer fallow are tillage with a field cultivator
or multiple applications of broad spectrum herbicides with zero tillage. Both systems are based on
substantial use of off farm resources. Our objective was to determine if strategic grazing of sheep may
allow grain growers to more sustainably manage crop residues, volunteer crop, and other weeds during
fallow periods. We conducted a study near Bozeman, Montana, USA, comparing three fallow weed
management systems in two crop rotations from 2005 to 2008. Fallow weed management systems were
conventional tillage, chemical-fallow (herbicide application), and sheep grazing. The crop rotations were
summer fallow–spring wheat and summer fallow–winter wheat. In late fall, chemical-fallow treatment
had greater residue cover and soil water content than did tilled- or grazed-fallow. At 0–15-cm depth,
soil had lower bulk density in chemical- and tilled-fallow than in grazed fallow. Similarly, soil NO3-N,
Ca, SO4-S concentrations and EC were lower following grazed-fallow than tilled-fallow, but Na concentration
was higher following grazed-fallow than tilled- or chemical-fallow. Following spring and winter
wheat, soil properties were not influenced by treatments. Grain yield was greater in winter wheat than
in spring wheat but the trend reversed in protein concentration. Although soil properties varied among
treatments, fallow management system had little influence on yield or quality of spring and winter wheat.
Sheep grazing during fallow periods had limited impact on subsequent wheat yield and quality, and is a
suitable practice for weed and residue management in wheat–fallow systems.
Field Crops Research 10/2013; 146:75-85. DOI:10.1016/j.fcr.2013.03.010 · 2.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sheep (Ovis aries L.) grazing, a cost-effective method of controlling weeds compared to herbicide
application and tillage, may influence soil C and N levels by consuming plant residue and returning feces
and urine to the soil, but little is known about the practice on soil C and N storage under dryland cropping
systems in the northern Great Plains, USA. Three weed control practices [sheep grazing (GRAZ), herbicide
application (CHEM), and tillage (MECH)] and three cropping sequences [continuous alfalfa (Medicago
sativa L.) (CA), continuous spring wheat (Triticum aestivum L.) (CSW), and spring wheat-pea (Pisum
sativum L.)/barley (Hordeum vulgaris L.) hay mixture-fallow (W-P/B-F)] were evaluated on a Blackmore
silt loam from 2009 to 2011 in southwestern Montana, USA. Crop yields and soil organic C (SOC), total N
(STN), NH4-N, and NO3-N contents at the 0–120 cm depth were quantified. Annualized spring wheat
grain and biomass (stems + leaves) yields and C and N contents were greater with CSW than with W-P/B-
F, but hay biomass and C content were similar between CA and W-P/B-F. While C and N in aboveground
biomass after spring wheat and hay harvest were removed through haying in CHEM and MECH, sheep
grazing removed about 99% of these elements in GRAZ. The SOC and STN at 5–15 cm were greater with
CSW or W-P/B-F than with CA in GRAZ and MECH, but SOC at 30–60 cm was greater with CA than with
CSW in MECH. The NH4-N content at most depths varied among treatments and years, but NO3-N
content at 5–120 cm was greater with CSW and W-P/B-F than with CA. Longer duration of sheep grazing
during fallow periods due to increased return of C and N through feces and urine or residue incorporation
to a greater depth probably increased soil C and N storage at the surface layer with CSW and W-P/B-F in
GRAZ and MECH, but increased root biomass likely increased C storage at the subsurface layer with CA in
MECH. Absence of N fertilization and/or greater N uptake probably reduced soil NO3-N level with CA than
with other cropping sequences. Regardless of treatments, SOC and STN declined from 2009 to 2011,
probably due to residue removal from haying and grazing. Moderate sheep grazing during fallow periods
can be used to increase soil C and N storage, obtain farm C credit, and sustain dryland crop yields
compared to herbicide application for weed control in the semiarid regions.
Soil and Tillage Research 08/2013; 134:133-141. DOI:10.1016/j.still.2013.07.015 · 2.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sheep (Ovis aries L.) grazing is an inexpensive method of weed control in dryland
cropping systems, but little is known about its effect on net greenhouse
gas (GHG) emissions. We evaluated the effect of sheep grazing compared
with herbicide application for weed control on GHG (CO2, N2O, and CH4)
emissions from May to October 2010 and 2011, net global warming potential
(GWP), and greenhouse gas intensity (GHGI) in a silt loam under dryland
cropping systems in western Montana. Treatments were two fallow management
practices (sheep grazing [GRAZ] and herbicide application [CHEM])
and three cropping sequences (continuous alfalfa [Medicago sativa L.] [CA],
continuous spring wheat [Triticum aestivum L.] [CSW], and spring wheat–pea
[Pisum sativum L.]/barley [Hordeum vulgaris L.] hay–fallow [W-P/B-F]). Gas
fluxes were measured at 3- to 14-d intervals with a vented, static chamber.
Regardless of treatments, GHG fluxes peaked immediately following substantial
precipitation (>12 mm) and N fertilization mostly from May to August.
Total CO2 flux from May to October was greater under GRAZ with CA, but
total N2O flux was greater under CHEM and GRAZ with CSW than other
treatments. Total CH4 flux was greater with CA than W-P/B-F. Net GWP and
GHGI were greater under GRAZ with W-P/B-F than most other treatments.
Greater CH4 flux due to increased enteric fermentation as a result of longer
duration of grazing during fallow, followed by reduced crop residue returned
to the soil and/or C sequestration rate probably increased net GHG flux
under GRAZ with W-P/B-F. Sheep grazing on a cropping sequence containing
fallow may not reduce net GHG emissions compared with herbicide application
for weed control on continuous crops.
Soil Science Society of America Journal 04/2013; 77(3):1012-1025. DOI:10.2136/sssaj2012.0386 · 1.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sweep net sampling of spring and winter wheat (Triticum spp.) was conducted in
2007 and 2008 at the Fort Ellis Research and Extension Center, Montana State University,
Bozeman, MT to determine hymenoptera parasitoid family composition, abundance, and
diversity in two wheat-fallow cropping systems managed by either tillage, herbicides, or
domestic sheep (Ovis aries) grazing. Eleven hymenopteran families classified as parasitoids
were captured in 2007 and 16 families in 2008. The mean abundance of parasitoids was
greatest (P < 0.05) in crops where the fallow component of the rotation was managed with
sheep grazing, as opposed to tillage and herbicide systems. Family diversity, as indexed by
Simpson’s D, did not differ between fallow management treatments (P = 0.88) or cropping
system (P = 0.74) but did differ between study year (P < 0.01).
Journal of the Kansas Entomological Society 01/2013; 86(1):22-35. DOI:10.2317/JKES110223.1 · 0.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neonatal lamb mortality is a major factor affecting profitability in the sheep industry, and lamb thermogenesis is a key element in neonatal lamb survival. Increased lamb vigor has been reported when ewes were supplemented during late gestation with algae-derived docosahexaenoic acid (DHA); however, the effects of DHA on lamb thermogenesis and immunocompetence have not been investigated. Eighty twin-bearing Targhee ewes (ages 2 to 5 yr; 68.5 ± 3 kg) were assigned randomly to 1 of 2 supplement treatments to determine the effects of feeding DHA to ewes during late gestation and early lactation on lamb thermogenesis, serum metabolites and hormones, and lamb growth. Supplement treatments were 12 g·ewe(-1)·d(-1) of algae-derived DHA (DHA Gold Advanced Bionutrition Corp., Columbia, MD; algae-derived DHA); and no algae-derived DHA (control). Supplements were individually fed daily during the last 30 d (±7 d) of gestation and pen fed (6 pens/treatment with 6 or 7 ewes/pen) during the first 38 d (±7 d) of lactation. One hour after lambing and before nursing, twin-born lambs were weighed, blood sampled via jugular puncture, and placed in a dry cold chamber for 30 min (0°C), and rectal temperatures were recorded every minute for 30 min. Lambs were removed from the cold chamber, blood sampled, warmed for 15 min, and returned to their dam. Ewes were blood sampled, and colostrum samples were collected 1 h postpartum. Ewe and lamb sera were assayed for glucose, NEFA, cortisol, and leptin. Lamb rectal temperature, glucose, NEFA, cortisol, leptin, and birth weights did not differ between treatments. The BW at 38 d was greater (P = 0.03) for lambs born to control ewes than for lambs born to algae-derived DHA-supplemented ewes; however, the colostrum of algae-derived DHA-supplemented ewes had a greater specific gravity (P = 0.05) than for control ewes. Overall, despite a potentially positive effect on ewe colostral IgG concentrations, supplementation of algae-derived DHA during late gestation and early lactation had a negative effect on lamb BW and did not affect indices of lamb thermogenesis.
[Show abstract][Hide abstract] ABSTRACT: A total of 16 mature healthy horses (body weight: 515.3 ± 37 kg [mean ± SD]) were used in two experiments to determine (1) how psyllium affects postprandial blood glucose and insulin concentrations, and (2) how psyllium affects blood glucose and insulin concentrations after an intravenous glucose infusion. Psyllium was fed along with a grain and hay ration (given twice daily) for 60 days. Treatments were as follows: (1) 90 g psyllium/d, (2) 180 g psyllium/d, (3) 270 g psyllium/d, (4) an isocaloric, no supplemental psyllium control. Pre- and postprandial blood samples were collected on day 60 for experiment 1, and blood samples collected before and after intravenous glucose infusion were analyzed for experiment 2. In experiment 1, horses fed with psyllium for 60 days had lower (P .01) mean postprandial blood glucose concentrations and there was a treatment × time effect for glucose (P < .001) and insulin (P = .03). Plasma glucose was lower at 90 minutes (P = .05) and 120 minutes (P .001) after a meal in horses fed with psyllium as compared with an isocaloric control. Postprandial serum insulin concentrations were lower at 90 minutes (P = .002) and 300 minutes (P .001) after a meal in horses fed with psyllium as compared with an isocaloric control. In experiment 2, peak glucose concentrations were lower (P = .01) in horses fed with psyllium for the previous 60 days compared with untreated horses and there was a treatment by time effect for glucose (P = .05). Peak blood glucose response was lower (P = .01) in horses fed with psyllium as compared with an isocaloric control after intravenous glucose infusion, whereas peak insulin concentrations and average insulin concentrations remained similar. Psyllium fed daily for 60 days alters postprandial glycemia and insulinemia in normal, nonobese, and unexercised horses.
[Show abstract][Hide abstract] ABSTRACT: Annual spring-seeded forage crops use less water than cereal grains, including durum (Triticum turgidum L. var. durum), and may be suitable to replace summer fallow. We conducted an experiment from 2002 through 2006 comparing yield, quality, and water and N use of durum and three annual forages, barley (Hordeum vulgare L.), barley interseeded with pea [Pisum sativum L. ssp. arvense (L.) Poir.], and foxtail millet [Setaria italica (L.) Beauv.] in 2-yr rotations. Durum in rotation with summer fallow and alfalfa (Medicago sativa L.) were included. Averaged over 5 yr, alfalfa had higher forage yield and quality, water use, and N accumulation compared to annual forages. Annual forages had similar preplant and postharvest soil water contents, but barley and barley–pea had higher yields and water use compared to millet. Barley–pea intercrop had superior forage crude protein (CP), neutral detergent fiber (NDF) and N accumulation compared to barley and millet, but acid detergent fiber (ADF) and nitrogen recovery index (NRI) were similar among annual forages. Averaged over 4 yr, preplant soil water and residual N content were greater for durum following fallow than for durum following annual forages, resulting in reduced fertilizer N requirement and greater yield, water use, grain N accumulation and NRI following fallow. Replacing summer fallow with annual forages reduced durum grain yield by 727 kg ha–1 but provided forage yield of 4.9 Mg ha–1. Annualized net returns in annual forage-durum systems were $127 ha–1, $77 and $34 ha–1 greater than for fallow-durum and alfalfa, respectively. Replacing summer fallow with annual forages reduced durum yield but improved profitability.
[Show abstract][Hide abstract] ABSTRACT: Sheep (Ovis aries L.) grazing during fallow for weed control in wheat (Triticum aestivum L.)-fallow systems may influence soil C and N levels and grain yields by returning part of consumed crop residue to the soil through feces and urine. We evaluated the effects of fallow management [sheep grazing (grazing), herbicide application (chemical), and tillage (mechanical)] for weed control and soil water conservation and cropping sequence [continuous spring wheat (CSW), spring wheat-fallow (SW-F), and winter wheat-fallow (WW-F)] on soil organic C (SOC), inorganic C (SIC), total N (STN), NH4-N, and NO3-N levels at the 0- to 120-cm depth and wheat yield. The experiment was conducted in a Blackmore silt loam (fine-silty, mixed, superactive, frigid, Typic Argiustolls) from 2004 to 2008 in southwestern Montana. Annualized wheat grain and biomass yields were greater in CSW than in SW-F and WW-F and greater in 2004 than in other years. From 2004 to 2007, SOC concentration at 0- to 15-cm declined by 2.99 g C kg-1 yr-1. In 2008, SOC content at 10- to 120-cm was greater in the mechanical or chemical than in the grazing treatment in CSW and SW-F. The STN content at 0- to 5-cm was greater in the chemical and mechanical than in the grazing treatment but at 30-to 60-cm was greater in the grazing than in the chemical treatment in CSW. From 2004 to 2006, NO3-N content at 0- to 60-cm was greater in SW-F or WW-F than in CSW. In 2008, NO3-N content at 30- to 120-cm was greater in CSW and SW-F than in WW-F and at 60- to 90-cm was greater in the mechanical than in the chemical treatment. The SIC and NH4-N contents were largely not influenced by treatments. Continuous tillage, followed by reduced amount of wheat residue returned to the soil from 2004 to 2007 probably reduced soil organic C and total N. In contrast, greater amount of N removed by wheat grain due to continuous cropping probably reduced soil NO3-N in CSW. For sustaining wheat yields and maintain soil C and N levels, reduced tillage with continuous cropping and less intensive sheep grazing that increase the amount of wheat residue returned to the soil could be adopted.
[Show abstract][Hide abstract] ABSTRACT: Late gestation supplementation of feed additives, such as rumen undegradable intake protein (RUIP), vitamin E, Zn, and chlortetracycline, has inconsistently improved ewe/lamb productivity. In 3 experiments, Western white-faced ewes were supplemented for at least 30 d during late gestation with 204 g/(ewe.d) on a DM basis of high (HS; 12.5% RUIP, 880 IU/kg of vitamin E, 176 mg/kg of Zn supplied by an AA complex, and 352 mg/kg of chlortetracycline) or low (LS; 7.56% RUIP and no supplemental vitamin E, Zn, or chlortetracycline) supplements. Ewes of different age (Exp. 1; 3- vs. 6-yr-old; n = 52) and BCS (Exp. 2; good vs. poor BCS; 3.0 and 1.7 +/- 0.5, respectively; n = 40) were supplemented individually in a 2 x 2 factorial arrangement of treatments for 29 d. Thereafter, each ewe was group fed the appropriate supplement until lambing (14 +/- 7 d). Ewe intake, colostral IgG, ewe and lamb parainfluenza type 3 (PI(3)) titers, milk production, ewe BW and BCS change, and lamb production were measured in both experiments. In Exp. 3, approximately 600 ewes were group fed HS or LS over 2 yr. Ewe BW, ewe BCS, lamb production, and lamb survival was measured in Exp. 3 with groups within year as the experimental unit. In Exp. 1, lambs born to 3-yr-old ewes fed the HS had greater (P = 0.01) anti-PI(3) antibody titers than lambs born to 3-yr-old ewes fed the LS. Three-year-old ewes had greater (P < 0.01) DMI than 6-yr-old ewes. In Exp. 1 and 2, d 3 and 10 milk production differences (P <or= 0.10) were detected among treatments; however, lamb production did not differ among treatments in either experiment. In Exp. 3, late gestation supplementation did not affect indices of ewe or lamb production. Under the condition of these 3 studies, late gestation supplementation of HS or LS did not affect ewe productivity. Similarly, ewe age and BCS did not affect productivity, nor did ewe age or BCS interact with type of late gestation supplement.
[Show abstract][Hide abstract] ABSTRACT: Backgrounding lambs on forage-based diets after weaning may provide producers with alternatives to traditional market-ing of lambs directly to feedlots. Our objective was to evaluate feedlot performance of lambs from different backgrounding treatments. Seventy-two crossbred lambs were randomly assigned to one of four backgrounding treatments. Treatments were imposed after traditional, range-weaning practice (140 d of age). Treatments were: 1) drylot ad libitum access to 80:20 alfalfa:barley pellets (PELLET); 2) cool-season, grass-paddock grazing (GRASS); 3) unweaned, dormant-range grazing (LATE WEAN); and 4) weaned, dormant-range grazing (RANGE). After 29 d of backgrounding, lambs within backgrounding treatment were assigned to feedlot pens (3 pens/treatment). Lamb-BW and ultrasound measurements were taken at wean-ing (d-29), after backgrounding (d 0), after transition to 70 per-cent grain diet (d 19), and at the end of the feedlot period (d 68). Lambs backgrounded on PELLET had greater BW (P < 0.10) at d 0 and d 68 than lambs assigned to other treat-ments. Feedlot DMI of PELLET lambs was greater than all other treatments, and feedlot ADG of PELLET lambs was greater than LATE WEAN and RANGE lambs (P < 0.10). At the end of the feedlot period (d 68), ultrasound measures of LM were greater (P < 0.05) for GRASS than either LATE WEAN or RANGE when BW on d 68 was included as a covariable. No differences (P > 0.10) in 12th-rib-fat thickness were detected among treatments at d 68. Results from our 2007 study indicate that 29-d-background treatments on dormant range diminished subsequent-feedlot performance; however, GRASS back-grounding had similar feedlot performance to PELLET back-grounding.
[Show abstract][Hide abstract] ABSTRACT: Twin-bearing Targhee ewes (Exp. 1, 1 yr, n = 42) and 1,182 single- and twin-bearing whiteface range ewes (Exp. 2, n = 8 experimental units over 2 yr) were used in a 2 x 2 factorial arrangement of treatments to determine the effect of supplemental energy source and level of vitamin E supplement on lamb serum metabolites and thermogenesis (Exp. 1) and on lamb growth (Exp. 2). During late gestation, ewes were individually fed (Exp. 1) or group-fed (Exp. 2) a daily supplement. Supplements were 226 g/ewe of daily safflower seed (DM basis; SS) with either 350 IU/ewe daily (VE) or no added supplemental (VC) vitamin E; or 340 g/ewe daily of a barley-based grain supplement (DM basis; GC) and either VE or VC. One hour postpartum in Exp. 1, twin-born lambs were placed in a 0 degrees C dry cold chamber for 30 min. Lamb rectal temperature was recorded every 60 s and blood samples were taken immediately before and after cold exposure. In Exp. 2, lambs were weighed at birth, at turnout from confinement to spring range (32 d of age +/- 7; turnout), and at weaning (120 d of age +/- 7). Ewes were weighed at turnout and weaning. In Exp. 1, a level of vitamin E x energy source interaction was detected (P < 0.10) for body temperature and change in NEFA and glucose concentrations. Lambs from SSVC ewes had the lowest (P = 0.01) body temperature and had decreased (P = 0.08) NEFA concentration. The SS lambs tended to have decreased (P < 0.11) concentrations of blood urea N (BUN) and thyroxine at 0 min than did lambs born to GC ewes. After 30 min of cold exposure, SS lambs had increased and GC lambs had decreased BUN, triiodothyronine, and triiodothyronine:thyroxine concentrations (P < 0.10). In Exp. 2, kilograms of lamb per ewe at turnout and weaning and lamb survival at weaning were greater (P < 0.07) for GC than SS lambs. Based on the decreased body temperature in SSVC lambs at birth, the greater change in BUN during the cold exposure for SS than GC lambs, and the decreased survival rate for SS than GC lambs, SSVC-supplemented ewes appeared to give birth to lambs with an apparently decreased energetic capacity. This may compromise the ability of the newborn lamb to adapt to extreme environmental conditions.
[Show abstract][Hide abstract] ABSTRACT: Changes in soil bulk density and soil nutrient profiles are a major concern of dryland grain producers considering grazing sheep on cereal stubble fields. Our objective was to compare burned, grazed, tilled, trampled and clipped wheat stubble fields on changes in soil bulk density and soil nutrient profiles. Treatments were evaluated in a series of three experiments using a randomized complete block design and four replications at each site. Contrast statements were used to make pre-planned comparisons among treatments. For Experiment 1, treatments were fall tilled, fall grazed, spring grazed, fall and spring combined (Fall/Spr) grazed, and an untreated control. Five mature ewes were confined with electric fence to a 111 m2 plot for 24 h for fall and spring grazed plots resulting in a stocking rate of 452 sheeps d/ha. For Fall/Spr, the stocking rate was 904 sheeps d/ha. For Experiment 2, treatments were fall grazed, fall burned, fall tilled, and an untreated control. In Experiment 3, treatments were fall trampling by sheep, spring trampling by sheep, fall and spring combined (Fall/Spr) trampling by sheep, hand clipping to a stubble height of 4.5 cm, and an untreated control. Trampling treatments were done at the same stocking rates as grazing treatments but sheep were muzzled to prevent intake. In Experiment 1, post-treatment organic matter tended to be greater (P = 0.09) in the mean of the grazed treatments than control plots. In all of the experiments, change in soil bulk density, and soil nutrient profiles did not consistently differ (P > 0.07) among treatments in any manner that would suggest a detrimental impact of grazing sheep on small grain residue. These results indicate a strong potential for grazing sheep on grain stubble without adversely impacting soil bulk density or nutrient profiles.
Small Ruminant Research 02/2007; 67(2-3). DOI:10.1016/j.smallrumres.2005.10.003 · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Weed control in fallow management to conserve soil moisture and nutrients is the largest variable cost to dryland grain production. Our objective was to compare burning, grazing, tilling, trampling and clipping wheat stubble fields on changes in total aboveground biomass and weed density. Treatments were evaluated in three experiments using a randomized complete block design for each experiment with four replications at each site. Contrasts statements were used to make pre-planned comparisons. For experiment 1, treatments were fall tilled, fall grazed, spring grazed, fall and spring combined (Fall/Spr) grazed, and an untreated control. For grazing treatments, five mature ewes were confined with electric fence to 111 m2 plot for 24 h for fall and spring resulting in a stocking rate of 452 sheep day/ha. For Fall/Spr the stocking rate was 904 sheep day/ha. For experiment 2, treatments were fall grazed, fall burned, fall tilled, and an untreated control. In experiment 3, treatments were fall trampling by sheep, spring trampling by sheep, fall and spring combined (Fall/Spr) trampling by sheep, stubble hand clipped to a height of 4.5 cm, and an untreated control. Trampling treatments were applied at the same stocking rates as grazing treatments but sheep were muzzled to prevent intake. Data were collected in the fall, prior to treatment imposition, and spring, after treatments had been removed. Post treatment biomass and weed density were greater (P < 0.05) in either control or tilled plots when compared to grazed plots. Post treatment biomass and weed density were greater (P < 0.01) for control than burned plots. Post treatment biomass, weed density, and percent change in these variables, did not differ (P > 0.08) between burned and tilled, and burned and grazed treatments. These results indicate the potential for using grazing sheep as a component in fallow management to reduce biomass and control weeds.
Small Ruminant Research 02/2007; 67(2-3):216-221. DOI:10.1016/j.smallrumres.2005.10.004 · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae) is the most damaging insect pest to Montana's $ 1 billion dollar per year grain industry. Current WSS control methods are either expensive, reduce wheat yields, or are not effective. Our objective was to compare burning, grazing, tilling, trampling and clipping wheat stubble fields on over-wintering WSS larval populations. Treatments were evaluated in three experiments using a randomized complete block design and four replications at each site. Eight, six, and two sites were used for Experiments 1, 2, and 3, respectively. Contrast statements were used to make pre-planned comparisons among treatments. For Experiment 1, treatments were fall tilled, fall grazed, spring grazed, fall and spring combined (Fall/Spr) grazed, and an untreated control. Five mature ewes were confined with electric fence to 111 m2 plot for 24 h in the fall and spring grazed treatments resulting in a stocking rate of 452 sheep d/ha. For Fall/Spr, the stocking rate was 904 sheep d/ha. For Experiment 2, treatments were fall grazed, fall burned, fall tilled, and an untreated control. In Experiment 3, treatments were fall trampled, spring trampled, Fall/Spr trampled, hand clipped to a stubble height of 4.5 cm, and an untreated control. Trampled treatments were done at the same stocking rates as grazing treatments but sheep were muzzled to prevent intake. Wheat stem sawfly larval numbers were collected in the fall and spring, pre- and post-treatment, respectively, by collecting all plant material from three, 0.46 m lengths of row and counting the number of live larvae present. In Experiment 1, WSS mortality was greater (P < 0.01) for the mean of all grazed treatments (68.4%) than either control (43%) or tilled (47%) plots. Mortality did not differ (P = 0.75) between fall (67%) and spring (64%) grazed plots but was greater (P = 0.02) for Fall/Spr (74%). In Experiment 2, larva mortality was greater (P < 0.01) for fall grazed (63%) than burned plots (52%). In Experiment 3, WSS mortality was greater (P < 0.01) for the mean of all trampling treatments (57%) than either control (33%) or clipped (32%) plots. Mortality did not differ (P > 0.25) between fall (54%) and spring trampling (47%) but was greater (P = 0.01) for Fall/Spr (70.6%). No differences (P > 0.25) were detected for WSS mortality when grazing was compared to trampling. These results indicate the potential for using grazing sheep to control wheat stem sawfly infestations in cereal grain production systems.
Small Ruminant Research 02/2007; 67(2-3):209-215. DOI:10.1016/j.smallrumres.2005.10.002 · 1.13 Impact Factor