Lammoglia M A, Bellows R A, Grings E E, Bergman J W, Bellows S E, Short R E, Hallford D M, Randel R D
BovaGen, San Antonio, TX 78216, USA.
J Anim Sci. 2000 Sep;78(9):2244-52. doi: 10.2527/2000.7892244x.
Prepubertal F1 heifers (n = 246; from crossbred dams bred to either Hereford [H], Limousin [L], or Piedmontese [P] sires) were fed 1.9% (LF) or 4.4% (HF) dietary fat from 254+/-4 d of age until they reached puberty or the breeding season started. Safflower seeds (37% oil with 79% linoleic acid) were the added fat source. Blood samples and backfat thickness measurements were obtained from 60 randomly selected heifers representing the sire breeds and diets studied. In addition, five H-sired heifers from both diets were serially bled at 28-d intervals. Total gain, ADG, body condition score, and backfat thickness were affected by sire breed (P < 0.001) but not diet. Backfat thickness was affected (P < 0.01) by the diet x time on feed interaction. Diet did not affect pubertal age (P > 0.10) but tended (P = 0.08) to affect the percentage of heifers pubertal by the beginning of breeding (June 4). Sire breed effects on puberty age at beginning of breeding, percentage pubertal at the beginning of breeding, and puberty age during the entire study were all highly significant. The effect of the diet x sire breed interaction on percentage of heifers pubertal at beginning of breeding (P < 0.05) was 74.4 vs 76.3% in H-sired, 69.8 vs 60.5% in L-sired, and 76.2 vs 97.6% in P-sired heifers (LF vs HF, respectively). Number of AI services per pregnancy and final pregnancy percentage were not affected by diet or the diet x sire breed interaction. Diet affected progesterone (P < 0.05) and cholesterol (P < 0.001) concentrations, and sire breed tended to affect (P = 0.06) cholesterol concentrations. The effect of the diet x time on feed interaction on cholesterol concentrations was highly significant. There were no effects of diet or sample period on insulin or growth hormone concentrations in serially collected blood samples. We conclude that effects of supplemental dietary fat may be breed-dependent and hypothesize that a feeding period of approximately 60 d duration may be more appropriate than the 162 d used in this study.
青春期前的F1代小母牛（n = 246；其杂交母本与赫里福德[H]、利木赞[L]或皮埃蒙特[P]种公牛配种）从254±4日龄开始，直至达到青春期或繁殖季节开始，分别饲喂1.9%（低脂肪，LF）或4.4%（高脂肪，HF）的日粮脂肪。添加的脂肪来源为红花籽（含油37%，亚油酸79%）。从60头随机挑选的代表所研究的种公牛品种和日粮的小母牛身上采集血样并测量背膘厚度。此外，对两种日粮组的5头H系小母牛每隔28天进行连续采血。总增重、平均日增重、体况评分和背膘厚度受种公牛品种影响（P < 0.001），但不受日粮影响。背膘厚度受日粮×采食时间交互作用的影响（P < 0.01）。日粮不影响青春期年龄（P > 0.10），但在繁殖开始时（6月4日），日粮对青春期小母牛的百分比有影响趋势（P = 0.08）。种公牛品种对繁殖开始时的青春期年龄、繁殖开始时青春期小母牛的百分比以及整个研究期间的青春期年龄的影响均高度显著。日粮×种公牛品种交互作用对繁殖开始时青春期小母牛百分比的影响（P < 0.05）为：H系小母牛中，低脂肪组对高脂肪组分别为74.4%对76.3%；L系小母牛中，分别为69.8%对60.5%；P系小母牛中，分别为76.2%对97.6%。每次妊娠的人工授精次数和最终妊娠率不受日粮或日粮×种公牛品种交互作用的影响。日粮影响孕酮浓度（P < 0.05）和胆固醇浓度（P < 0.001），种公牛品种对胆固醇浓度有影响趋势（P = 0.06）。日粮×采食时间交互作用对胆固醇浓度的影响高度显著。日粮或采样期对连续采集血样中的胰岛素或生长激素浓度均无影响。我们得出结论，日粮补充脂肪的影响可能因品种而异，并推测大约60天的饲喂期可能比本研究中使用的162天更合适。
