Daniel Z C T R, Brameld J M, Craigon J, Scollan N D, Buttery P J
Division of Nutritional Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK.
J Anim Sci. 2007 Jun;85(6):1565-76. doi: 10.2527/jas.2006-743. Epub 2007 Feb 12.
Two experiments were conducted to determine whether the decreased proportion of fast muscle fibers seen previously in 2-wk-old lambs from ewes that were dietary restricted from d 30 to 70 of gestation are still evident in older lambs and what the consequences may be in terms of growth rates and carcass composition. Throughout both experiments, ewes were fed on an individual basis according to the recommended dietary allowance throughout pregnancy relative to metabolic BW (BW(0.73)). Control groups were fed as above, and the treatment groups had their nutrient supply reduced to 50% of this recommended allowance from d 30 to 70 (Exp. 1) or d 30 to 85 (Exp. 2) of gestation, after which they were returned to the same level of nutrition as the control group. All twin lambs were kept with their dams, and at 2 wk were given access to creep. After weaning, lambs were individually housed and fed ad libitum to 24 or 17 wk of age for Exp. 1 and 2, respectively. Although not significant (P = 0.18), growth to 24 wk (Exp. 1) resulted in a small decrease in the protein content and therefore an increase in the fat:lean ratio in the carcass of lambs subjected to maternal dietary restriction. This was not apparent when animals were slaughtered at 17 wk (Exp. 2; P > 0.68). Few significant effects of maternal dietary restriction on the fiber type composition of muscles were observed. In Exp. 1 the number of fast fibers increased (P < 0.008) with no effect on slow fiber number in LM. In Exp. 2 an increase in the total number of fibers in male lambs and an increase in type II (A and B) fibers in female lambs were observed in the LM, and an increase in IIB fiber number was observed in semitendinosus (ST) muscle from male lambs. Prenatal maternal dietary restriction during the time of muscle differentiation demonstrated an increase in type IIB muscle fibers and increase in intramuscular fat; although significant, effects on subsequent carcass quality of lambs were relatively small. These data suggest that the lambs adapted to changes in muscle fiber composition previously observed at 2 wk. However, lambs in this study were well fed during postnatal growth. Whether offspring would still have been able to compensate if they had received poor nutrition postnatally and whether that failure to compensate would have influenced carcass composition remain to be determined.
进行了两项试验，以确定之前在妊娠第30至70天饮食受限的母羊所产2周龄羔羊中观察到的快肌纤维比例降低的情况在年龄较大的羔羊中是否仍然明显，以及这对生长速度和胴体组成会有什么影响。在两项试验中，整个孕期都根据相对于代谢体重（BW(0.73)）的推荐日粮供应量对母羊进行单独饲喂。对照组按上述方式饲喂，处理组在妊娠第30至70天（试验1）或第30至85天（试验2）将其营养供应减少至该推荐供应量的50%，之后恢复到与对照组相同的营养水平。所有双羔羔羊都与母羊一起饲养，2周龄时可自由采食开食料。断奶后，试验1和试验2中的羔羊分别单独圈养，并自由采食至24周龄和17周龄。尽管差异不显著（P = 0.18），但在试验1中生长至24周龄时，母羊孕期饮食受限的羔羊胴体蛋白质含量略有下降，因此脂肪与瘦肉比例增加。当动物在17周龄屠宰时（试验2；P > 0.68），这种情况并不明显。未观察到母羊饮食受限对肌肉纤维类型组成有显著影响。在试验1中，腰大肌（LM）中快肌纤维数量增加（P < 0.008），慢肌纤维数量无变化。在试验2中，观察到雄性羔羊的LM中纤维总数增加，雌性羔羊的II型（A和B）纤维增加，并且在雄性羔羊的半腱肌（ST）中IIB型纤维数量增加。在肌肉分化期进行产前母羊饮食限制表明IIB型肌纤维增加，肌内脂肪增加；尽管有显著影响，但对羔羊后续胴体品质的影响相对较小。这些数据表明，羔羊适应了之前在2周龄时观察到的肌纤维组成变化。然而，本研究中的羔羊在出生后生长期间饲养良好。如果后代在出生后营养不佳，它们是否仍能进行补偿，以及这种无法补偿的情况是否会影响胴体组成，仍有待确定。
