Strauch T A, Neuendorff D A, Brown C G, Wade M L, Lewis A W, Keisler D H, Randel R D
Texas Agricultural Experiment Station, Overton, TX 75684, USA.
J Anim Sci. 2003 Jun;81(6):1363-70. doi: 10.2527/2003.8161363x.
Objectives were to determine effects of lasalocid on reproductive performance and serum concentrations of leptin and IGF-I, and to correlate concentrations of leptin and IGF-I with reproductive performance of beef cows. Forty-one purebred, multiparous Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments by BW, BCS, and predicted calving date. Treatment began 21 d before expected calving. Cows were each fed 1.4 kg daily of an 11:1 corn:soybean meal supplement, with the L group receiving 200 mg of lasalocid/cow daily. Cows and calves were weighed, and cow BCS was assessed at calving and at 28-d intervals thereafter. Blood samples were collected weekly precalving, at parturition, and twice weekly thereafter. Sterile marker bulls were maintained with cows for estrous detection. Six days after estrus, ovaries were evaluated for corpus luteum formation, and blood samples from d 6, 7, and 8 after estrus were collected. Serum samples were assayed for progesterone (P4), IGF-I, and leptin concentration. Progesterone concentrations > 1 ng/mL were considered indicative of a functional corpus luteum. Treatment ended after completion of a normal estrous cycle, and cows removed from treatment were placed with a fertile bull equipped with a chinball marker. There were no treatment differences in calving date, calf sex, cow BW, BCS, calf BW, calf ADG, or in serum concentrations of P4, IGF-I, or leptin. Prepartum cow ADG was increased (P < 0.01) in L cows and tended (P < 0.011) to be increased from calving to d 56 after calving in L cows. Postpartum interval (PPI) was not affected by treatment; however, a greater percentage (P < 0.05) of L cows conceived by 90 d after calving (43% L vs. 15% C). First-service conception rate tended (P < 0.08) to be greater in L vs. C cows (68 vs. 40%), but pregnancy rate was not different (P < 0.12; 86% for L vs. 65% for C). There were no treatment differences (P > 0.18) for serum IGF-I concentrations. At calving, leptin was positively correlated with IGF-I (P < 0.04; r = 0.32), BCS (P < 0.06; r = 0.29), and cow BW (P < 0.02; r = 0.36), and was negatively correlated with PPI (P < 0.06; r = -0.29). These results provide evidence that feeding an ionophore before calving and during the postpartum period may increase the number of cows that rebreed to maintain a yearly calving interval. Cows with higher concentrations of leptin postpartum may exhibit shorter PPI.
本研究旨在确定拉沙洛西对繁殖性能以及瘦素和胰岛素样生长因子-I（IGF-I）血清浓度的影响，并将瘦素和IGF-I的浓度与肉牛的繁殖性能相关联。41头纯种经产婆罗门母牛按体重、体况评分（BCS）和预计产犊日期分为对照组（C；n = 20）或拉沙洛西组（L；n = 21）。在预计产犊前21天开始处理。每头母牛每天饲喂1.4千克11:1的玉米:豆粕补充料，L组母牛每天额外添加200毫克拉沙洛西。对母牛和犊牛进行称重，并在产犊时及之后每隔28天评估母牛的BCS。在产犊前每周采集血样，产犊时采血，之后每周采集两次。用不育的试情公牛与母牛接触以检测发情。发情后6天，评估卵巢黄体形成情况，并采集发情后第6、7和8天的血样。检测血清样本中的孕酮（P4）、IGF-I和瘦素浓度。孕酮浓度>1纳克/毫升被认为表明黄体功能正常。在完成一个正常发情周期后结束处理，从处理组转出的母牛与配备有下巴球标记的可育公牛合群。在产犊日期、犊牛性别、母牛体重、BCS、犊牛体重、犊牛平均日增重（ADG），或P4、IGF-I或瘦素的血清浓度方面，处理组间没有差异。L组母牛产犊前的平均日增重增加（P < 0.01），并且从产犊到产犊后56天L组母牛的平均日增重有增加的趋势（P < 0.011）。产后间隔（PPI）不受处理影响；然而，产犊后90天内L组母牛受孕的比例更高（P < 0.05；L组为43%，C组为15%）。L组母牛首次输精受胎率有高于C组的趋势（P < 0.08；分别为68%和40%），但妊娠率没有差异（P < 0.12；L组为86%，C组为65%）。血清IGF-I浓度在处理组间没有差异（P > 0.18）。在产犊时，瘦素与IGF-I呈正相关（P < 0.04；r = 0.32）、与BCS呈正相关（P < 0.06；r = 0.29）、与母牛体重呈正相关（P < 0.02；r = 0.36），并且与PPI呈负相关（P < 0.06；r = -0.29）。这些结果表明，在产犊前和产后期间饲喂离子载体可能会增加再次配种以维持每年产犊间隔的母牛数量。产后瘦素浓度较高的母牛可能表现出较短的PPI。
