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Arkansas Animal Science Department Report 2001 these levels of gain, the conversion efficiencies were 14.9 and 8.3 lb of supplemental grain required to produce an additional pound of gain from 2.5GS and 5GS, respectively. These conversion efficiencies are somewhat better than observed in a previous study from feeding grain sorghum at 1% of BW (9.5 lb/lb; Galloway et al. 1993a), but are worse that from another study from feeding corn at .5% of BW to calves grazing bermudagrass pastures (6.1 lb/lb; Galloway et al. 1993b). The rate of shrink (%/hour) during the period between 2 and 4 hours after removal from pasture was lower (P < 0.10) from calves on the 5GS treatment than from calves on the 0GS or 2.5GS treatments (Table 2). However, total weight loss over the entire 10-hour period (lb and % of initial body weight) did not differ (P > 0.10) among treatments. Therefore, feeding supplemental grain sorghum to calves grazing bermudagrass pastures during the late grazing season improved weight gain, but conversion efficiencies were poor making the economic efficiency questionable. In order for the calves to gain approximately 2 lb/day during the late grazing season, it was necessary to feed them 25 lb of ground grain sorghum each week (5GS). Feeding grain sorghum prior to a period of feed and water deprivation did not impact cattle shrink over a 10-hour period. Implications In order to achieve body weight gains in excess of 1.5 lb/day in a typical summer grazing period from calves on bermudagrass pastures, supplements must be fed. Feeding at levels at or above 0.5% of body weight should improve animal gain, but conversion efficiencies may limit economic benefits of the supplementation. Feeding ground grain sorghum immediately prior to removing calves from bermudagrass pastures should have minimal impact on body weight loss during a period of feed and water deprivation. Literature Cited Galloway, D. L., et al., 1993a. J. Anim. Sci. 71:1288. Galloway, D. L., et al., 1993b. Prof. Anim. Scientist 9:173. Gunter, S., and M. Phillips. 1998. AR. Agric. Exp. Sta. Rept. 464. pp. 93-95. Lusby, K.S., and G.W. Horn. 1991. Prof. Anim. Scientist 7:43. Table 1. Growth performance by stocker steers grazing bermudagrass pastures and fed different levels of ground grain sorghum. Level of ground grain sorghum, lb/day M-F Item 0 2.5 5 SE Initial weight, lb 490 489 492 1.2 Weight – d 29, lb 523 522 535 4.2 Final weight, lb 562 b 567 b 584 a 5.7 Total gain, lb 72 d 78 cd 92 c 5.9 Daily gain, lb 1.49 d 1.61 cd 1.92 c 0.123 Feed/additional gain, lb/lb - 14.9 8.3 - a,b Means within a row without a common superscript letter differ (P < 0.10). c,d Means within a row without a common superscript letter differ (P = 0.11). Table 2. Weight loss during a 10-h drylot shrink by stocker steers fed different levels of ground grain sorghum. Level of grain sorghum, lb/day M-F Item 0 2.5 5 SE Shrink, %/h 0-2 h 1.32 1.44 1.47 0.279 2-4 h 0.98 a 1.06 a 0.56 b 0.127 4-6 h 1.13 0.84 1.38 0.207 6-8 h 0.61 0.63 0.62 0.112 8-10 h 0.17 0.53 0.31 0.153 Total weight loss, lb 45 51 49 1.7 Total weight loss, % 9.8 10.1 10.0 0.13 a,b Means within a row without a common superscript letter differ (P < 0.10). 62
Influence of Fish Oil Addition on Growth Performance and Immune Function of Grazing Cattle T. J. Wistuba, E. B. Kegley, and J. K. Apple 1 Story in Brief In the U.S., intake of n-3 fatty acids by humans is approximately 1.6 g/d, of which 1.4 g is α-linolenic acid (ALA; 18:3) and 0.1 to 0.2 g is eicosapentaenoic acid (EPA; 20:5) and docosahexanoic acid (DHA; 22:6). The predominant sources of EPA and DHA are fish and fish oils. Inclusion of fish oil in ruminant diets may fortify the fatty acid composition of meats and modulate the immune system. Therefore, an experiment was conducted to determine the effects of supplemental fish oil on growth performance and immune characteristics of beef calves. The experiment (78-d study) used 48 crossbred steers (509 ± 48.5 lb initial BW) grazing mixed grass pastures (n = 16). Steers were supplemented with 4 lb/d of one of four treatment supplements. Treatment supplements consisted of: 1) corn-based supplement; 2) corn-based supplement with 1.5% fish oil; 3) wheat midd-based supplement; and 4) wheat midd-based supplement with 1.5% fish oil. Fish oil supplementation had a negative impact on ADG when added to the corn-based supplement and no effect when added to the wheat midd-based supplement (3.0 vs. 2.6 and 2.8 vs. 2.7 lb/d, respectively; base-supplement x fish oil interaction, P < 0.03). Isolated lymphocytes from calves fed the corn-based supplement with fish oil had a greater response to stimulation with concanavalin A than lymphocytes from calves fed the corn-based supplement, and there was no effect of fish oil addition to the wheat midd-based supplement (base-supplement x fish oil interaction, P < 0.01). Fish oil supplementation in the current trial seemed to stimulate the immune system. However, the reduction in performance may limit its use as an immune stimulant and may limit the potential to use it for altering the fatty acid composition of meat. Introduction Fish industry by-products are potential sources of valuable nutrients. Therefore, methods of converting fish industry by-products into reliable sources of animal feeds would benefit both the fish and livestock industries. In the United States, intake by humans of n-3 fatty acids is approximately 1.6 g/d, of which 1.4 g is α-linolenic acid (ALA; 18:3) and 0.1 to 0.2 g is eicosapentaenoic acid (EPA; 20:5) and docosahexanoic acid (DHA; 22:6) (Kris-Etherton et al., 2000). The predominant sources of EPA and DHA are fish and fish oils. Recently, the dietary recommendation for the highly unsaturated n-3 fatty acids has increased, specifically EPA and DHA, from 0.15 to 0.65 g/d. To achieve this four-fold increase in consumption, consumers will either have to adjust their diets, or the nutrient content of certain foodstuffs may be able to be changed. However, feeding diets that alter the fatty acid content of meat may also affect other aspects of beef production. Theis et al. (1999) reported that dietary fish oils may have a negative impact on immune function and fatty acid composition in pigs. The objective of this study was to determine the effects of dietary fish oil addition on growth and immune function of cattle consuming a forage based diet. Materials and Methods Forty-eight steers (509 ± 48.5 lb initial BW) were obtained from the University Livestock and Forestry Branch Station in Batesville. Steers were shipped to the University of Arkansas Stocker and Receiving Unit in Savoy prior to the start of the study. Calves were weighed upon arrival, blocked by weight (four blocks) and randomly assigned to pens. There were three steers in each of the 16 pens, for a total of 12 animals per treatment. Pens were 1.1 acre mixed grass pastures. Supplements were fed at a rate of 4.0 lb/d. Treatment supplements (Table 1) consisted of: 1) corn-based supplement; 2) corn-based supplement with 1.5% fish oil; 3) wheat middbased supplement; and 4) wheat midd-based supplement with 1.5% fish oil. The diets were mixed at approximately weekly intervals. Steers were fed their respective diets for 78 d. Steers were weighed on day 0, 14, 28, 42, 56, and 78 and were observed daily for signs of clinical disease. Steers were weighed on consecutive days at d 0 and 78 to start and finish the trial. On d 78 of the study, all calves were bled by jugular venipuncture, and blastogenic response of peripheral lymphocytes to phytohemagglutinin (PHA; Sigma Chemical Co., St. Louis, MO), concanavalin A (CONA; Sigma Chemical Co.) and pokeweed mitogen (PWM; Sigma Chemical Co.) 1 All authors are associated with the Department of Animal Science, Fayetteville. 63
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Arkansas Animal Science Department
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spine copy ARKANSAS ANIMAL SCIENCE
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INTRODUCTION The faculty and staff
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COMMON ABBREVIATIONS Abbreviation T
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The Effects of Nitrogen Fertilizati
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Demographics and Academic Success o
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Influence of Moisture Concentration
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Impact of Spontaneous Heating Durin
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Effects of Tall Fescue Inoculated w
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Yield and Nutritive Value of Easter
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2000 Dairy Herd Improvement Herds i
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The Impact of Multiple Antimicrobia
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The Impact of Multiple Antimicrobia
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The Use of Hurdle Technology to Red
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Consumer Acceptability of Forage Fe
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