P G Hatfield

Montana State University, Bozeman, Montana, United States

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Publications (49)61.15 Total impact

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    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 systems.
    Nutrient Cycling in Agroecosystems 06/2014; 99:79-93. · 1.42 Impact Factor
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    Lenssen, A.W, U.M. Sainju, P.G. Hatfield
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    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. · 2.47 Impact Factor
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    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. · 2.37 Impact Factor
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    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; 77:1012-1025. · 1.82 Impact Factor
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    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. · 0.55 Impact Factor
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    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.
    Journal of Animal Science 07/2011; 89(12):4305-13. · 2.09 Impact Factor
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    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.
    Journal of Equine Veterinary Science - J EQUINE VET SCI. 01/2011; 31(4):160-165.
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    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.
    Agronomy journal 10/2010; · 1.52 Impact Factor
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    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.
    Agronomy journal 07/2010; 102:1553-1561. · 1.52 Impact Factor
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    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.
    Journal of Animal Science 12/2009; 88(3):1125-34. · 2.09 Impact Factor
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    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.
    Sheep & Goat Research Journal Sheep & Goat Research Journal. 01/2009; 24.
  • Journal of Equine Veterinary Science - J EQUINE VET SCI. 01/2009; 29(5):357-358.
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    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.
    Journal of Animal Science 07/2008; 86(11):3194-202. · 2.09 Impact Factor
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    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.
    01/2007;
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    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 m 2 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 01/2007; 67(67):209-215. · 1.12 Impact Factor
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    ABSTRACT: Seasonal availability of lamb in the Western United States contributes to a large fluctuation in lamb supply. However, alternatives to fall marketing may not be practical unless feedlot performance and carcass characteristics of older lambs finished in the spring is equal to or superior to fall finished lambs. Our objective was to evaluate feedlot performance and carcass characteristics of spring-born wether lambs that were either feedlot finished in the fall and slaughtered at 7–8 months of age, or feedlot finished in the spring and slaughtered at 14–15 months of age. April- and May-born whiteface wethers (n=240) were used in a complete random design experiment with wethers finished on an 80% whole barley-based diet starting when they were either 5–6 months (FALL), or 12–13 months (SPRING) of age in October or May, respectively. Wethers were fed in outdoor pens with 12-pens/finishing trial, four lambs/pen, and six finishing trials (three fall and three spring) during a 3-year period. Feedlot response variables included BW, DMi, gain:feed ratios, ADG, and body composition. Carcass variables were body wall thickness, back fat, yield, and USDA quality grade. Year×treatment interactions were detected for all feedlot variables (P0.50). Intake, ADG, final BW (years 2 and 3 only), and body wall thickness were greater (P0.05) between FALL and SPRING finished lambs. Gain:feed ratio did not differ (P>0.05) between FALL and SPRING wethers in year 1, but was greater (P
    Small Ruminant Research - SMALL RUMINANT RES. 01/2006; 66(1):102-107.
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    ABSTRACT: In dryland farming areas of Montana, annual precipitation is not sufficient for annual planting of cereal grains. Instead, a crop-summer fallow farming system is used to conserve soil moisture and increase available nitrogen for subsequent crop growth. Managing this summer fallow, either by mechanical means or with herbicides, is the highest variable cost associated with dryland grain production in Montana. Wheat stem sawfly, Cephus cinctus (Hymenoptera: Cephidae) is the most damaging insect pest to Montana's US$ 1 billion per year grain industry. Weed management is the largest variable cost associated with dryland grain production and summer fallow management. Six fields, located on four commercial Montana grain operations, were grazed by sheep and goats from October 2002 to May 2003 to determine the impact grazing has on C. cinctus populations, weed and volunteer cereal growth, soil compaction, and gravimetric water concentrations. Percent C. cinctus larval mortality and percent reduction of weed biomass was greater in grazed compared to non-grazed areas (P 0.01). No differences in soil bulk density or gravimetric water concentrations were found between treatments (P > 0.11). Grazing fallow with sheep and goats appears to successfully improve C. cinctus and weed management in grain production systems without impacting soil compaction. # 2005 Elsevier B.V. All rights reserved.
    09/2005;
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    ABSTRACT: The objective of this study was to determine whether increasing levels of dietary safflower oil would alter unsaturated fat (especially CLA) and tocopherol content of lamb, animal performance, carcass characteristics, or color stability of lamb muscle tissue. Targhee x Rambouillet wethers (n = 60) were assigned to one of three diets (four pens per treatment with five lambs per pen) in a completely random design. Diets were formulated with supplemental safflower oil at 0 (control), 3, or 6% (as-fed basis) of the diet. Diets containing approximately 80% concentrate and 20% roughage were formulated, on a DM basis, to be isocaloric and isonitrogenous and to meet or exceed NRC requirements for Ca, P, and other nutrients. A subsample of 12 wethers per treatment was selected based on average BW (54 kg) and slaughtered. Carcass data (LM area, fat thickness, and internal fat content) and wholesale cut weight (leg, loin, rack, shoulder, breast, and foreshank), along with fatty acid, tocopherol, and color analysis, were determined on each carcass. The LM and infraspinatus were sampled for fatty acid profile. Increasing safflower oil supplementation from 0 to 3 or 6% increased the proportion of linoleic acid in the diet from 49.93 to 55.32 to 62.38%, respectively, whereas the percentage of oleic acid decreased from 27.94 to 23.80 to 20.73%, respectively. The percentage of oil in the diet did not (P > or = 0.11) alter the growth and carcass characteristics of lambs, nor did it alter the tocopherol content or color stability of meat. Increasing levels of safflower oil in lamb diets decreased (P < 0.01) the weight percentage of oleic acid in the infraspinatus and LM, and increased linoleic acid (P < 0.01). Oil supplementation increased (P < 0.01) the weight percentage of various isomers of CLA in muscle, with the greatest change in the cis-9,trans-11 isomer. Supplementation of sheep diets with safflower oil, up to 6% of the diet, resulted in increasing levels of unsaturated fatty acids and CLA in the lean tissue, without adversely affecting growth performance, carcass characteristics, or color stability of lamb.
    Journal of Animal Science 09/2005; 83(9):2175-81. · 2.09 Impact Factor
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    ABSTRACT: Fifty wether lambs were used in a 48-day finishing study to evaluate the effects of feeding diets high in linoleic acid on animal performance, carcass characteristics and conjugated linoleic acid (CLA) content of muscle and fat tissue. Lambs were fed either a safflower supplemented diet containing 6% oil from safflower seeds or a control diet containing no added oil. Morlin safflower seeds, containing 37% oil with 79% linoleic acid, were utilized. Lambs fed the safflower supplemented diet had greater (P=0.04) ADG than those fed the control diet (0.29±0.01kg per day versus 0.25±0.01kg per day, respectively). Gain to feed ratio was greater (P=0.02) for lambs fed the safflower than control diet (14.8±0.54kg/100kg of feed versus 12.7±0.54kg/100kg of feed, respectively). Dressing percent, internal fat weight and longissimus muscle area did not differ (P>0.30) between lambs fed safflower or control diets. However, back fat thickness tended to be greater (P=0.17) for the lambs fed safflower diet (4.03±0.48mm versus 3.03±0.48mm, for safflower versus control lambs, respectively). Fat content of muscle tissue was greater (P=0.02) in safflower supplemented lambs (4.3±0.23g/100g muscle tissue versus 3.4±0.23g/100g muscle tissue for safflower versus control lambs, respectively). Safflower supplemented lambs had 2.3 percentage units lower (P=0.004) oleic acid (C18:1), 2.6 percentage units higher (P
    Small Ruminant Research 01/2003; 49(1):11-17. · 1.12 Impact Factor
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    ABSTRACT: Yearling Targhee ewes (n = 24; not pregnant or lactating) were used in a 2 x 2 factorial arrangement of treatments to determine the effects of supplemental vitamin E (0 IU [0vitE] vs 330 IU vitamin E x ewe(-1) x d(-1) [+vitE]) and Zn (0 mg [0Zn] vs 140 mg Zn x ewe(-1) x d(-1) [+Zn]) on serum alpha-tocopherol concentrations, antibodies to parainfluenza type 3 (PI3), ewe BW, Zn liver concentrations, and serum alkaline phosphatase activity. Ewes were managed as one group, grazed native pasture, and had ad libitum access to white salt and water. Ewes that received supplemental vitamin E were orally dosed every other day with 660 IU of DL-alpha-tocopherol acetate in a gelatin capsule beginning on d 1 and continuing to d 63 of the study. Ewes that received Zn supplement were orally dosed every other day with 280 mg of Availa-Zn 100 (Zinpro Corp., Eden Prairie, MN, IFN 6-32-054) in gelatin capsules for 63 d. All ewes were vaccinated with killed PI3 on d 22 and 42. No interactions were detected (P > 0.35); however, serum alpha-tocopherol concentrations and PI3 antibody titer dilutions changed (P = 0.001) over the length of the study. Ewe BW change, serum alkaline phosphatase activity, and liver Zn concentrations did not differ (P > 0.22) between 0Zn and +Zn or 0vitE and +vitE ewes. Serum a-tocopherol tended to be higher (P = 0.08) in +vitE than 0vitE ewes and was numerically higher (P = 0.16) in +Zn than 0Zn ewes. Antibody titer dilutions were higher (P = 0.06) in 0Zn than +Zn ewes and did not differ (P = 0.83) between 0vitE and +vitE ewes. These results indicate that high levels of supplemental Zn may have a tendency to improve serum alpha-tocopherol concentrations but may have negative impacts on humoral immune function.
    Journal of Animal Science 05/2002; 80(5):1329-34. · 2.09 Impact Factor