Metabolic changes, ovarian function and growth related gene expression in goats given stair-step feeding during estrous cycle

• Compensatory growth is a physiological process by which organism expedites growth.
• We proposed simplified stair-step feeding during the estrous cycle in goats.
• A possible link between compensatory growth and reproduction was observed.
• Feeding management affected not only metabolic but also ovarian functions.
• Expression of BCL-2 gene was partially induced by stair-step feeding in goats.

The study was conducted to determine effects of the stair-step feeding during estrous cycle on metabolic changes, ovarian function, and growth related gene expression. Mature goats (n = 48) that exhibited at least two normal, consecutive estrous cycles were randomly assigned to either the control or stair step fed group. In the control group, goats were fed at 100% of nutrient requirement (at a rate to maintain normal growth of 46–50 g/day) throughout two consecutive estrous cycles. The goats in the stair-step group were fed 70 and 130% of the control for first estrous and second estrous cycles, respectively. Blood and ovaries samples were collected throughout the 6-week experiment to examine concentration of blood metabolites, progesterone (P4) and ovarian cells proliferation. Serum glucose, insulin concentrations and number of visible follicles were greater (P < 0.05) in stair-step fed goats than in control goats. Serum P4 concentrations were not different (P > 0.05) throughout the experiment. Percentages of good oocyte quality obtained from all sizes of follicle were better (P < 0.05) in the stair-step fed goats than that of the control goats. Rates of cell proliferation in granulosa and thecal layers across all follicular size, as determined by labeling index, were greater (P < 0.05) in stair-step fed goats than in control goats. The mRNA levels of BCL-2 gene in granulosa and thecal layers in all follicular size were similar between groups, except for granulosa layer of follicle size 1–3 mm, expression of BCL-2 gene in the stair-step fed goats was greater than (P < 0.05) that of the control group. These data demonstrate the stair-step feeding management affects metabolic, ovarian functions, and expression of BCL-2 gene in goats.