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Forty-five weaned wether goats (12 Alpine, 12 Angora, 10 Boer (87.5%) and 11 Spanish) were used to determine effects on growth performance of consumption of a 75% concentrate diet (DM basis) for 24 weeks (75C) or for 12 weeks subsequent to 12 weeks of feeding a 50% concentrate diet (50C). Initial BW was 20.2, 12.2, 20.7 and 19.2 kg (S.E.=0.73) for Alpine, Angora, Boer and Spanish, respectively, and age was 4 months when the experiment began. There were no interactions between genotype and dietary treatment in DM intake, ADG or gain efficiency in weeks 1–12 or 13–24. DM intake in weeks 1–12 ranked Alpine and Boer>Spanish>Angora (703, 689, 567 and 436 g per day; P<0.05) and in weeks 13–24 was significantly greater for Alpine and Boer versus Angora and Spanish (712, 702, 515 and 456 g per day; P<0.05). DM intake was similar between dietary treatments. In week 8, OM digestibility was 79.3 and 71.3% (S.E.=1.57) and NDF digestibility was 54.2 and 52.1% (S.E.=3.46) for 75C and 50C, respectively. Total VFA concentration was similar between diets; the acetate:propionate ratio was greater (P<0.05) for 50C versus 75C (4.12 versus 2.56). ADG in weeks 1–12 was greatest (P<0.05) for Boer (59, 59, 90 and 49 g per day for Alpine, Angora, Boer and Spanish, respectively); in weeks 13–24 ADG was lowest (P<0.05) for Spanish (25 g per day) and tended to be greater (P<0.10) for Boer versus Alpine (82 versus 58 and 63 g per day). Gain efficiency (ADG:DM intake) was greater (P<0.05) for Angora and Boer than for Alpine and Spanish in weeks 1–12 (132 and 127 versus 85 and 85 g/kg), and in weeks 13–24 was lower (P<0.05) for Spanish than for Angora and Boer (80, 121, 104 and 51 g/kg for Alpine, Angora, Boer and Spanish, respectively). ADG and gain efficiency were greater (P<0.05) for 75 versus 50% dietary concentrate in weeks 1–12 (ADG: 73 and 55 g per day; gain efficiency: 122 and 92 g/kg), and tended to be greater (P<0.11) for 50C than for 75C in weeks 13–24 (ADG: 49 and 65 g per day; gain efficiency: 77 and 101 g/kg for 75C and 50C, respectively). In conclusion, differences in growth performance among Alpine, Angora, Boer and Spanish wether goats were similar with 50 and 75% concentrate diets, and the genotypes responded similarly to the change in dietary concentrate level from 50 to 75%. [Copyright &y& Elsevier]

Abstract: A study was conducted to determine effects of grazing of mixed grass/forb pastures at three stocking rates (SR) on subsequent performance of goats and sheep fed a concentrate-based diet. Experimental periods, in 2002 and 2003, were 15 weeks in length, following 16 weeks of grazing (May to September) of pastures with warm season grasses and various forbs. Sheep (Katahdin) and goat (≥75% Boer blood) wethers were 4–5 months of age when grazing began. Stocking rates were four (SR4), six (SR6), and eight (SR8) animals per 0.4ha pasture, with equal numbers of sheep and goats and three pastures per SR. Two sheep and two goats from each pasture were used in the subsequent confinement period, with initial BW of 25±0.6 and 23±0.5kg, respectively. Average daily gain by all animals during grazing tended to decrease linearly (P <0.10) with increasing SR (61, 51, and 47g/day for SR4, SR6, and SR8, respectively). In the period after grazing, DM intake tended (P <0.10) to be affected by an interaction between SR and year (year 1: 958, 966, and 1011g/day; year 2: 1109, 904, and 930g/day for SR4, SR6, and SR8, respectively (S.E.=56.8)). There was a tendency (P <0.07) for an interaction between SR and year in overall ADG (year 1: 172, 160, and 177g; year 2: 193, 135, and 141g for SR4, SR6, and SR8, respectively (S.E.=12.6)). Sheep had higher overall ADG than goats (193 versus 133g; S.E.=7.9). Gain efficiency (ADG:DMI) was not influenced by SR (P >0.10). Energy expenditure (EE) measured in weeks 3 and 9 via heart rate increased linearly (P <0.05) with increasing SR (562, 589, and 628kJ/kg BW0.75 for SR4, SR6, and SR8, respectively; S.E.=16.4). In conclusion, SR had no impact on ADG of sheep and goat wethers consuming a concentrate-based diet subsequent to the grazing period, which may involve effect of prior SR on subsequent EE. [Copyright &y& Elsevier]

Abstract: Differences among ruminant species in forage selectivity offer potential for efficient utilization of pastures with diverse arrays of plant species. One common management strategy that may influence forage selectivity is stocking rate (SR). Therefore, this experiment was conducted to determine effects of SR on performance and forage selectivity of growing sheep and goat wethers co-grazing grass/forb pastures. Grazing was for 16 weeks in 2002 and 2003. Pastures consisted of various grasses, primarily bermudagrass (Cynodon dactylon) and johnsongrass (Sorghum halepense), and forbs (e.g., ragweed; Ambrosia spp.). Sheep (Khatadin) and goats (75% Boer) averaged 21±0.7 and 21±0.5kg initial BW, respectively, and were 4–5 months of age when grazing began. Stocking rates were four (SR4), six (SR6), and eight (SR8) animals per 0.4-ha pasture, with equal numbers of sheep and goats. The nine pastures (three/treatment) were divided into four paddocks for rotational grazing in 2-week periods. Forage mass (pre- and post-grazed) and composition of grass versus forbs were determined by quadrat samples and transect analysis, respectively. BW was measured every 4 weeks and preference values for grass, forbs, and ragweed (10: highest possible preference; 0: consumption in proportion to availability; −10: no consumption) were determined from fecal microhistology and transect measures. There was a year×SR interaction (P &#60;0.05) in herbage DM mass before grazing (year 1: 2937, 3298, and 3351kg/ha; year 2: 3033, 2928, and 2752kg/ha for SR4, SR6, and SR8, respectively (S.E.=174.4)). Post-grazed forage mass decreased linearly (P &#60;0.05) as SR increased (2279, 1693, and 1288kg/ha for SR4, SR6, and SR8, respectively (S.E.=102.6)). In vitro true DM digestibility of pre-grazed forage samples was similar among SR, but SR×year interacted (P &#60;0.05) for post-grazed samples (year 1: 57.0, 54.4, and 53.5; year 2: 56.8, 49.0, and 48.3 for SR4, SR6, and SR8, respectively (S.E.=2.16). Year and SR interacted (P &#60;0.05) in the percentage of grass in pastures post-grazing determined by transect (year 1: 64, 69, and 74%; year 2: 50, 66, and 73% for SR4, SR6, and SR8, respectively (S.E.=8.4)). The preference for grasses was higher and that for total forbs lower for sheep than for goats (P &#60;0.05). The preference value for ragweed, measured in year 2, was lower (P &#60;0.05) for sheep than for goats (−1.6 versus 0.2) and increased linearly with increasing SR. Average daily gain tended (P &#60;0.10) to decrease linearly as SR increased (61, 51, and 47g/day), and total BW gain per hectare increased linearly (P &#60;0.05; 610, 759, and 933g/day for SR4, SR6, and SR8, respectively). In conclusion, post-grazing herbage mass >1000kg/ha at most measurement times suggests that decreasing forage availability with increasing SR may not have been primarily or solely responsible for the effect on ADG by limiting DM intake. Rather, the effect of SR on available forage mass could have limited the ability of both sheep and goats to compensate for the effect of SR on forage nutritive value. [Copyright &y& Elsevier]

Abstract: A study was conducted to assess effects of stocking rate (SR) on grazing behavior and energy expenditure (EE) by growing sheep and goat wethers co-grazing grass/forb pastures. Grazing was for 16-week periods in 2002 and 2003. Pastures consisted of various grasses, primarily bermudagrass (Cynodon dactylon) and johnsongrass (Sorghum halepense), and forbs (e.g., ragweed; Ambrosia spp.). Sheep (Khatadin) and goats (≥75% Boer) averaged 21±0.7 and 21±0.5kg initial BW, respectively, and were 4–5 months of age when grazing began. Stocking rates were four (SR4), six (SR6), and eight (SR8) animals per 0.4-ha pasture, with equal numbers of sheep and goats. The nine pastures (three/treatment) were divided into four paddocks that were rotationally grazed in 2-week periods. In weeks 3, 8, and 13 of both years, EE was determined on one goat and one sheep in each pasture via heart rate. In the same weeks, behavioral observations (position and activity) were made every 30min of 13.5h of daylight on two goats and two sheep in each pasture. Grazing behavior using IGER Grazing Behavior Monitoring System units was also measured over 24-h periods on animals used for EE measurement. Based on visual observations, grazing (52.7, 57.1, and 61.4%) and standing time (61.1, 66.3, and 69.8%) increased and idle time in daylight (24.2, 21.1, and 15.9% for SR4, SR6, and SR8, respectively) decreased linearly (P &#60;0.05) as SR increased. Species interacted (P &#60;0.05) with year in daylight time spent standing and ruminating. Grazing time during daylight was similar between species (56.1 and 58.0% for sheep and goats, respectively), although idle time was greater (P &#60;0.05) for goats (23.6% versus 17.2%; S.E.=1.41). Time spent ruminating in daylight was similar among SR but was greater for sheep in year 2 but not year 1 (year 1, 22.3% versus 19.0%; year 2, 27.8% versus 15.1% for sheep and goats, respectively; S.E.=1.44). Based on the IGER units, the number of steps increased linearly (P &#60;0.05) with increasing SR (2279, 2707, and 2788 for SR4, SR6, and SR8, respectively (S.E.=96.4)), but was similar for the two species. As SR increased, time spent eating increased (7.4, 8.4, and 9.6h) and time spent lying (11.0, 10.2, and 8.9h), ruminating (7.9, 7.7, and 6.8h), and idle (8.6, 8.0, and 7.6h for SR4, SR6, and SR8, respectively) decreased (P &#60;0.05). Goats spent less time eating (1.1h) and more time idle (0.7h) than did sheep (P &#60;0.05). SR, species, and year interacted (P &#60;0.05) in EE of wethers (year 1, sheep: 510, 569, and 572kJ/kg BW0.75; year 2, sheep: 572, 597, and 648kJ/kg BW0.75; year 1, goat: 524, 524, and 640kJ/kg BW0.75; year 2, goat: 499, 496, and 551kJ/kg BW0.75 for SR4, SR6, and SR8, respectively; S.E.=17.0). In summary, influences of SR on grazing time and EE can vary with grazing season. With forage conditions of this study, SR had similar effects on grazing behavior of sheep and goats when co-grazing. Effects of SR on EE may contribute to impact on ADG by small ruminants. [Copyright &y& Elsevier]