The objective of this study was to test the €œmale effect€ on the reproductive performance of Anglo Nubian does (n = 180), aged between 24 and 60 months, under different male-to-female ratios (1:20 €“ T20, 1:30 €“ T30, and 1:40 €“ T40) and climatic conditions (dry season €“ DS, and rainy season €“ RS). Does were randomly distributed into three groups (T20, T30, and T40) and were isolated from bucks at a distance of 300 m for 60 days before the start of the experiments. The first manifestation of estrous during the DS occurred 6.83 ± 4.54 (T20), 6.72 ± 4.56 (T30) and 7.05 ± 5.23 (T40) days following the onset of the breeding season (P>0.05). In the RS, onset of estrous was observed 6.60 ± 4.74 (T20), 6.70 ± 4.43 (T30) and 7.46 ± 4.54 (T40) days after the beginning of the breeding season (P>0.05). Estrous induction in females during the DS occurred in 95% (T20), 80% (T30), and 75.5% (T40) of all females. During the RS, estrous detection reached 100% (T20), 100% (T30), and 97.5% (T40) of all females, with no difference between all RS and DS groups. Estrous synchronization during the DS occurred in 35.00% (T20), 36.66% (T30), and 32.50% (T40) of all females, for an average occurrence of 34.72%. During the RS, synchronization occurred in 65% (T20), 70% (T30) and 62.25% (T40) of all females, for an average occurrence of 65.75%; no difference was detected between the RS and the DS. Pregnancy rates in the DS groups were 65.0% (T20), 70.0% (T30), and 62.5% (T40), while pregnancy rates in the RS were 90.0% (T20), 86.6% (T30), and 95.0% (T40). No difference was observed for conception rates between any of the RS and DS groups. Prolificacy during the DS was 1.30 (T20), 1.30 (T30) and 1.35 (T40), while in the RS prolificacy was 1.29 (T20), 1.25 (T30) and 1.30 (T40). Thus, the male effect can be used effectively for goats under 1:20€“1:40 male-to-female ratios in a 45-day mating season under varying climatic conditions.
The aim of this work was to evaluate the effect of heat stress during oocyte maturation on ovine in vitro embryo production. Ovaries were collected at abattoirs and oocytes retrieved from follicles ranging from 2 and 6 mm in diameter. After selection, all oocytes, in 10 replicates, were placed in in vitro maturation (IVM) during 24 hours. The oocytes were submitted to heat stress at 41º C during 3, 6, 12, 18 and 24 hours and were further transferred to 39º C in order to complete IVM, which was the temperature of maturation of control oocytes. Embryonic development was determined on days 3, 4, 5, and 8 post-fertilization. Embryo evaluation was performed as total cell count by DAPI staining and determination of positive blastomere for apoptosis by the TUNEL assay. We observed that heat stress diminishes (P < 0.05) oocyte maturation capacity in accordance with exposure time at 41º C. In the group of oocytes incubated at 39 ºC, 70.70% matured, while in the groups exposed to heat stress at 41º C, only 45.28%, 35.17%, 12.30%, 9.74% and 4.60% matured after 3, 6, 12, 18 and 24 hours of incubation, respectively. The duration of exposure to heat stress was inversely proportional (P < 0.05) to embryonic developmental capacity and directly proportional (P < 0.05) to the number of blastocysts positive to apoptosis. However, the cleavage rate and embryonic development from 8 to 16 cells and morulae stages were affected by heat stress (P > 0.05) only up to 18 hours of incubation. The results allow the conclusion that heat stress during oocyte in vitro maturation reduces the quantity and quality of ovine embryos produced in vitro determined by the high incidence of apoptosis
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