Renden J A, Benoff F H, Williams J C, Bushong R D
Department of Poultry Science, Auburn University, Alabama 36849-5416.
Poult Sci. 1990 Jan;69(1):16-26. doi: 10.3382/ps.0690016.
The purpose of the present experiment was to measure changes in physical variables with sexual maturity (SM), the oviposition of first egg, in sex-linked dwarf pullets when SM was delayed by the photoschedule. Offspring were produced from matings of dwarf Single Comb White Leghorn chickens divergently selected for high (H) or low (L) 20-wk BW. At 15 wk of age, pullets from half-sibling sets were randomly assigned to a diet either of low energy (LE: 2,500 kcal/kg of ME, 15% CP) or high energy (HE: 3,000 kcal/kg of ME, 15% CP) and were placed in cages. When a pullet reached SM, the mature (M) pullet and an immature (I, absence of oviposition), half-sibling pullet on the same diet were sampled for BW as well as for the weights of abdominal fat, liver, ovary, oviduct, whole egg (M pullets), yolk, and shell and for the number of rapidly developing follicles. Proximate measurements (wet weight) were made for defeathered carcasses and livers as well as for ovaries and oviducts. There were significant (P less than or equal to .01) line effects for BW at SM (H greater than L); age at SM (L greater than H); weights for the liver, abdominal fat, egg, albumen, shell (H greater than L), and yolk (L greater than H); number of developing follicles (H greater than L); percentage of carcass protein (L greater than H) and of fat (H greater than L); as well as for liver protein (L greater than H), fat (H greater than L), and ash (L greater than H). There were significant (P less than .01) diet effects for abdominal fat (HE greater than LE) and shell weight (LE greater than HE). There was a line-by-diet interaction for total feed intake and for total energy intake from 15 wk to oviposition of the first egg. There were significant (P less than .01) SM effects (M greater than I) for BW at SM, number of developing follicles, oviduct weight, and fat content of the reproductive organs; also, reproductive organ weights accounted for differences in BW at SM. There was an interaction for line by maturity state; the L pullets showed a greater increase in ovarian weight with oviposition of the first egg than did the H pullets. The results of this study indicated that the threshold requirements for BW, composition, or both, for SM may have been exceeded in Leghorn-type chickens when photoscheduling was used to delay the onset of SM.
本实验的目的是测量性成熟（SM）（即产下第一枚蛋）时身体变量的变化，该实验针对的是通过光照程序延迟性成熟的伴性矮小蛋鸡。后代由经过不同方向选育的矮小单冠白来航鸡交配产生，选育方向为高（H）或低（L）20周龄体重。15周龄时，将半同胞组的小母鸡随机分配到低能量（LE：2500千卡/千克代谢能，15%粗蛋白）或高能量（HE：3000千卡/千克代谢能，15%粗蛋白）日粮组，并放入笼中。当小母鸡达到性成熟时，对成熟（M）小母鸡和同一日粮组的未成熟（I，未产蛋）半同胞小母鸡进行体重采样，同时采集腹部脂肪、肝脏、卵巢、输卵管、全蛋（M小母鸡）、蛋黄、蛋壳的重量以及快速发育卵泡的数量。对去毛后的胴体、肝脏以及卵巢和输卵管进行近似测量（湿重）。性成熟时体重存在显著（P≤0.01）的品系效应（H大于L）；性成熟年龄（L大于H）；肝脏、腹部脂肪、蛋、蛋白、蛋壳（H大于L）和蛋黄（L大于H）的重量；发育卵泡数量（H大于L）；胴体蛋白质（L大于H）和脂肪（H大于L）的百分比；以及肝脏蛋白质（L大于H）、脂肪（H大于L）和灰分（L大于H）。腹部脂肪（HE大于LE）和蛋壳重量（LE大于HE）存在显著（P＜0.01）的日粮效应。从15周龄到产下第一枚蛋期间，总采食量和总能量摄入量存在品系与日粮的交互作用。性成熟时体重、发育卵泡数量、输卵管重量和生殖器官脂肪含量存在显著（P＜0.01）的性成熟效应（M大于I）；此外，生殖器官重量导致了性成熟时体重的差异。品系与成熟状态之间存在交互作用；L品系小母鸡产下第一枚蛋时卵巢重量的增加幅度大于H品系小母鸡。本研究结果表明，当采用光照程序延迟性成熟时，来航型鸡可能已超过性成熟对体重、组成或两者的阈值要求。
