Bielli A, Gastel M T, Pedrana G, Moraña A, Castrillejo A, Lundeheim N, Forsberg M, Rodriguez-Martinez H
Department of Anatomy and Histology, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
Anim Reprod Sci. 2000 Feb 28;58(1-2):73-86. doi: 10.1016/s0378-4320(99)00076-7.
The aim of the present study was to determine whether pre- and post-pubertal young rams on different grazing regimes, resulting in differences in live weight (LW), would show corresponding differences in testicular growth or testicular morphometry that could influence the reproductive traits of these rams upon reaching adulthood. Forty-one spring-born Corriedale rams were reared on either native pasture (low feeding level, Group L, n=22) or improved pasture (higher feeding level, Group H, n=19) from 1 to 7 months of age. Thereafter, half the animals in the native-pasture group were placed on improved pasture and vice versa, thus creating an additional four differential-grazing treatment groups (Groups LL, n=11; LH, n=11; HL, n=10; and HH, n=9). Animals were managed in this way until 18 months of age. Half the animals from each group were then castrated and their testes were subjected to morphometric analysis. The remaining animals (Groups LL, n=6; LH, n=6; HL, n=5; and HH, n=4) were managed together until 30 months of age (from 18 to 27 months on native pastures and from 27 to 30 months of age on improved pastures, at a stocking rate of two to three rams per hectare), whereupon they were also castrated for testicular morphometry. LW and scrotal circumference (SC) were recorded every 60 days. The stereological analysis of testicular parenchyma included counts of elongated spermatids and Sertoli cells. Differences (P<0.001) in LW were observed between feeding levels, even at 30 months of age. Differences (P<0.001) in SC existing at the end of the differential treatment (18 months of age) disappeared (n.s.) soon after. Most differences (P<0.05) in testicular morphometry existing at the end of the differential treatments were no longer significant 1 year later. It is concluded that changes in grazing management during pre- and post-pubertal periods can induce short-lived differences in testicular post-natal growth in Corriedale rams but do not influence testicular morphology or function later in life.
本研究的目的是确定处于不同放牧制度下的青春期前和青春期后的年轻公羊，由于体重（LW）存在差异，其睾丸生长或睾丸形态是否会出现相应差异，而这些差异是否会在公羊成年后影响其繁殖性状。41只春季出生的考力代公羊在1至7月龄时，分别饲养在天然牧场（低饲养水平，L组，n = 22）或改良牧场（高饲养水平，H组，n = 19）。此后，天然牧场组中的一半动物被转移到改良牧场，反之亦然，从而形成另外四个不同放牧处理组（LL组，n = 11；LH组，n = 11；HL组，n = 10；HH组，n = 9）。动物以这种方式管理至18月龄。然后，每组中的一半动物被阉割，并对其睾丸进行形态分析。其余动物（LL组，n = 6；LH组，n = 6；HL组，n = 5；HH组，n = 4）一起管理至30月龄（18至27月龄在天然牧场，27至30月龄在改良牧场，每公顷放养两到三只公羊），之后也进行阉割以进行睾丸形态分析。每60天记录一次体重和阴囊周长（SC）。睾丸实质的体视学分析包括对延长型精子细胞和支持细胞的计数。即使在30月龄时，不同饲养水平之间的体重差异也很显著（P<0.001）。差异处理结束时（18月龄）存在的阴囊周长差异（P<0.001）在之后不久就消失了（无显著差异）。差异处理结束时存在的大多数睾丸形态差异（P<0.05）在1年后不再显著。研究得出结论，青春期前和青春期后放牧管理的变化可在考力代公羊出生后的睾丸生长中诱导短暂的差异，但不会影响其后期的睾丸形态或功能。
