The impact of enhanced early postnatal nutrition on the histomorphological features of the ovaries in fat-tailed Sanjabi ewe lambs.

Abstract

This study aimed to investigate whether providing additional ad libitum feeding could improve reproductive characteristics in prepubertal ewe lambs. Twelve Sanjabi ewe lambs, approximately one-month-old and with an average initial weight of 11.6 ± 1.3 kg, were monitored over a 3-month period, which was divided into three distinct periods of 30 days each. The first period spanned from the lambs' age of one to two months, the second period covered their age range of two to three months, and the third period encompassed their age range of three to four months. The lambs were randomly assigned to either a control group (C) or a treatment group (T). The control group received a basal diet consisting of hay and milk, whereas the treatment group received an enhanced diet comprising hay, milk, and concentrate. Live weight (LW) and average daily gain (ADG) were measured weekly, and blood samples were collected from the jugular vein at days 30, 60, and 90 of the experiment to determine the concentrations of progesterone (P4) and estrogen (E2). Following the 90-day experiment, the lambs were humanely euthanized in accordance with established protocols. Subsequently, both ovaries from each animal were removed, weighed and subjected to a comprehensive histological analysis. The ovaries underwent fixation, embedding, and sectioning procedures, followed by staining with hematoxylin and eosin (H&E) to facilitate microscopic examination. Ovary microscopic sections from both C and T groups were examined to assess follicles at various developmental stages, including primordial follicle number (PreFN) and diameter (PriFD), primary follicle number (PriFN) and diameter (PriFD), secondary follicle number (SFN) and diameter (SFD), antral follicle number (AFN) and diameter (AFD), and granulosa layer thickness of secondary (GLTSF) and antral follicles (GLTAF). The impact of diet and three experimental periods on ADG and LW exhibited significant variations. There was a significant increase (P < 0.05) in LW in the T group compared to the T group, with noticeable differences in LW fluctuations observed during distinct periods. However, ADG was more prominent in the initial and second observation periods than in the third. The impact of diet and experimental periods on P4 and E2 concentrations was found to be negligible. The T group showed significant improvements (P < 0.05) in PreFD, PriFN, and GLTAF compared to the C group. This study suggests that ad libitum concentrate feeding may promote reproductive characteristics in prepubertal ewe lambs. Further research is needed to explore its potential impact on the age of puberty.