Juengel Jennifer L, Davis George H, Wheeler Roger, Dodds Ken G, Johnstone Peter D
AgResearch, Invermay Agricultural Centre, Mosgiel, 9092, New Zealand.
AgResearch, Invermay Agricultural Centre, Mosgiel, 9092, New Zealand.
Anim Reprod Sci. 2018 Apr;191:34-43. doi: 10.1016/j.anireprosci.2018.02.002. Epub 2018 Feb 7.
The objectives of this study were to determine factors affecting lamb birth weight (BWT) and differences between BWT of the largest and smallest littermates (BWTD) and to assess the relative importance of BWT and BWTD on lamb survival and growth to weaning. Records from twin (n = 5369) or triplet (n = 1664) litters born on pasture were utilised. Breeds included Coopworth, Romney, Perendale, composite and Texel. Ewe and sire breed, age and weight of the dam, sex, and number of lambs born (NLB) affected BWT. Neither embryo loss nor ovulation pattern (i.e. all ova released from one ovary or some from each) were associated with BWT. Dam weight and NLB affected BWTD but dam age, sire or dam breed did not. Loss of an embryo reduced BWTD, and BWTD was lower when the ewe ovulated from both ovaries versus only one ovary for twins, but not triplets. Whereas BWT was moderately heritable (h = 0.20), BWTD was not heritable (h = 0.003). Lamb survival was positively associated with BWT. Lambs with BWTD > 1.3 kg were less likely to survive (73.3%) than those from litters of smaller BWTD (range 82.8-85.7% survival). Growth rate of twin and triplet lambs was positively associated with BWT. Surprisingly, lambs from litters with moderately high BWTD had slightly greater (approximately 3%) growth rate than those from lambs of low to intermediate BWTD. Thus, while large BWTD were negatively associated with survival, BWT itself, which was moderately heritable, appeared to be a stronger driver of lamb survival and average daily gain.
本研究的目的是确定影响羔羊出生体重（BWT）的因素以及最大和最小同窝羔羊出生体重之间的差异（BWTD），并评估BWT和BWTD对羔羊存活及断奶前生长的相对重要性。利用了在牧场出生的双羔（n = 5369）或三羔（n = 1664）同窝羔羊的记录。品种包括库泊沃思羊、罗姆尼羊、佩伦代尔羊、杂交羊和特克塞尔羊。母羊和公羊的品种、母羊的年龄和体重、性别以及出生羔羊数（NLB）会影响BWT。胚胎损失和排卵模式（即所有卵子从一个卵巢排出或每个卵巢各排出一些）均与BWT无关。母羊体重和NLB会影响BWTD，但母羊年龄、父本或母本品种则不会。胚胎损失会降低BWTD，对于双羔而言，当母羊从两个卵巢排卵时，BWTD低于仅从一个卵巢排卵时，但三羔则不然。虽然BWT具有中等遗传性（h = 0.20），但BWTD不具有遗传性（h = 0.003）。羔羊存活与BWT呈正相关。BWTD>1.3千克的羔羊存活可能性（73.3%）低于BWTD较小同窝羔羊（存活范围为82.8 - 85.7%）。双羔和三羔羔羊的生长速度与BWT呈正相关。令人惊讶的是，BWTD中等偏高的同窝羔羊的生长速度比BWTD低至中等的羔羊略高（约3%）。因此，虽然较大的BWTD与存活呈负相关，但具有中等遗传性的BWT本身似乎是羔羊存活和平均日增重的更强驱动因素。
