Gillis M H, Duckett S K, Sackmann J R, Realini C E, Keisler D H, Pringle T D
Department of Animal and Dairy Science, University of Georgia, Athens 30602-2771, USA.
J Anim Sci. 2004 Mar;82(3):851-9. doi: 10.2527/2004.823851x.
Thirty-six Angus x Hereford heifers (365 kg) were used to determine effects of dietary lipid supplementation from two sources during the final 32 or 60 d of feeding on serum and adipose tissue leptin concentrations, animal performance, and carcass characteristics. Following an initial feeding period of 56 d, heifers were fed one of three diets in a 3 x 2 factorial arrangement: 1) basal diet, 2) basal diet plus 4% (DM basis) corn oil, or 3) basal diet plus 2% (DM basis) rumen-protected conjugated linoleic acid (a mixture of Ca-salts of palm oil fatty acids with 31% conjugated linoleic acid). Jugular blood samples were collected at 28-d intervals (d 28 to 118) and serum subsequently harvested for leptin quantification via RIA. Real-time ultrasound measurements were collected at 28-d intervals across time on feed. At slaughter, samples were obtained from various adipose depots. Data were analyzed with dietary treatment, length of supplementation, adipose depot (when appropriate), and all two- and three-way (when appropriate) interactions in the repeated measures model. Measures of feedlot performance, including ADG, DMI, and gain:feed did not differ (P > 0.23) with dietary treatment or supplementation length. Heifers supplemented with corn oil tended (P < 0.07) to have higher marbling scores following 32 d of treatment than those supplemented with rumen-protected conjugated linoleic acid, with controls intermediate. Quality grade and hot carcass weight did not differ (P > 0.15) with treatment or length of supplementation. Leptin concentrations were higher (P < 0.05) from d 57 to 118 on feed than the initial period (d 0 to 56) of dietary adaptation when all animals received the basal diet. Circulating leptin concentrations were not affected by dietary treatment. However, leptin concentrations in adipose tissues were greater (P < 0.05) for heifers supplemented with corn oil than either control or rumen-protected conjugated linoleic acid diets, which did not differ. Compared with adipose tissues from rumen-protected conjugated linoleic acid-supplemented animals, tissues from heifers fed corn oil contained 68% greater leptin concentration. Correlations between performance, carcass traits, and serum leptin concentrations were low. Serum leptin concentrations across time on feed were not associated with carcass and performance data, including ADG, DMI, and gain:feed. Based on these data, concentrations of leptin are not related to indices of feedlot performance and carcass quality in beef cattle.
选用36头安格斯×海福特小母牛（体重365千克），以确定在育肥期最后32天或60天添加两种来源的日粮脂肪对血清和脂肪组织中瘦素浓度、动物生产性能及胴体特性的影响。经过56天的初始育肥期后，小母牛按照3×2析因设计分为三种日粮处理组：1）基础日粮；2）基础日粮+4%（干物质基础）玉米油；3）基础日粮+2%（干物质基础）瘤胃保护共轭亚油酸（棕榈油脂肪酸钙盐混合物，含31%共轭亚油酸）。每隔28天（第28天至118天）采集颈静脉血样，随后收获血清，通过放射免疫分析法（RIA）测定瘦素含量。在整个育肥期内每隔28天进行实时超声测量。屠宰时，从不同脂肪沉积部位采集样本。采用重复测量模型，分析日粮处理、添加脂肪时间、脂肪沉积部位（如适用）以及所有二元和三元（如适用）交互作用对数据的影响。育肥性能指标，包括平均日增重（ADG）、干物质采食量（DMI）和料重比，在日粮处理或添加脂肪时间上无显著差异（P>0.23）。添加玉米油的小母牛在处理32天后大理石花纹评分有高于添加瘤胃保护共轭亚油酸小母牛的趋势（P<0.07），对照组居中。胴体质量等级和热胴体重在处理或添加脂肪时间上无显著差异（P>0.15）。当所有动物采食基础日粮时，从第57天到118天育肥期内的瘦素浓度高于日粮适应期初始阶段（第0天至56天）（P<0.05）。日粮处理对循环瘦素浓度无影响。然而，添加玉米油的小母牛脂肪组织中的瘦素浓度高于对照组和添加瘤胃保护共轭亚油酸组（P<0.05），后两组之间无差异。与添加瘤胃保护共轭亚油酸组动物的脂肪组织相比，采食玉米油的小母牛脂肪组织中瘦素浓度高68%。生产性能、胴体性状与血清瘦素浓度之间的相关性较低。育肥期内血清瘦素浓度与胴体及生产性能数据，包括ADG、DMI和料重比均无关联。基于这些数据，瘦素浓度与肉牛育肥性能和胴体品质指标无关。
