Short-term supplementation with maize increases ovulation rate in goats when dietary metabolizable energy provides requirements for both maintenance and 1.5 times maintenance

Abstract

This study aimed to evaluate ovarian follicular dynamics in goats submitted to synchronization of estrus and supplemented with diets that differed in the metabolizable energy source and amount of energy. The experiment was carried out using 42 does allocated into three treatments, fed for nine days with a ration providing 1.0 times maintenance containing maize (1MM, n = 14) or without maize (1M, n = 14) or a ration providing 1.5 times maintenance containing maize (1.5MM, n = 14). Estrus was synchronized with two injections of cloprostenol given seven days apart. Does were also treated with intravaginal progesterone inserts and eCG. The number of ovulations and size of the follicles were measured using ultrasonography on Days 10, 11 and 12 after the start of the dietary treatment. The interval to estrus and duration of estrus did not differ between treatments (P = 0.382). Does fed with 1MM and 1.5MM had a similar number of ovulations, but a greater number of ovulations than goats fed with 1M (P = 0.028). The mean number of small, medium, large and total number of follicles on Days 10 to 12 of ultrasound evaluations did not differ (P = 0.204) between treatments, but mean numbers changed over time (P < 0.001). The mean frequency and amplitude of LH pulses and concentrations of glucose, insulin, leptin and IGF-1 in plasma were not significantly affected (P > 0.258) by any of the treatments. In summary, the inclusion of maize in the ration can stimulate ovulation rate at maintenance level. Similar results between groups fed diets that included maize and provided metabolizable energy at 1.0 and 1.5 maintenance demonstrate that in order to increase ovulation rate when synchronizing estrous cycles in does, dietary supplementation with maize can be restricted to provide a maintenance level of metabolizable energy only, which would reduce dietary costs.