11 Fertility Evaluation of the Goat Semen Diluted in Citrate-Egg Yolk Extender With High or Low Egg Yolk Concentration, Cooled and Stored at 5°c for 24 Hours

Abstract

This experiment was designed to evaluate, in vitro and in vivo, the cooling resistance of the goat semen diluted in citrate-egg yolk extender with high (20%) or low (2.5%) concentration of egg yolk. The experiment was conducted at Dairy Goat Station of the Animal Science Department (Federal University of Viçosa, MG, Brazil), during the natural breeding season (March to June). Four bucks of the Alpine (n = 2) and Saanen (n = 2) breeds were used as semen donors. The bucks did not have apparent abnormalities of the reproductive tract and the fertility was proved based on andrologic examination and the records from the previous breeding season. The semen was collected by the artificial vagina method and a fresh sample was analyzed for the sperm cell motility and concentration. Therefore, the semen was diluted in citrate-egg yolk extender with high (T1 = 20%) or low (T2 = 2.5%) concentration of egg yolk, cooled and stored at 5°C for 24 h, before being used either for quality analysis or for AI. Reproductive-age female Saanen and Alpina goats (n = 68) were inseminated via cervix with cooled semen from T1 (n = 32) or from T2 (n = 36). The parametric data from cooled semen quality (sperm cell motility, vigor, hyposmotic swelling test, morphology, and supravital staining) were analyzed by ANOVA, for the main effect of the treatment, using the SAEG 9.0 program (UFV, 2005). The differences between means were accessed by the Student-Newman-Keuls test. The qualitative data from pregnancy rate were tested by chi-square (Ayres et al. BioEstat 2.0, 2000). The mean ± SEM for each quality test of the cooled semen, as well the P-value for comparisons between treatments were as follows: motility, 68.6 ± 15.5 and 78.0 ± 5.6% (P < 0.05); vigor, 2.5 ± 0.6 and 3.2 ± 0.3 (P < 0.05); supravital staining, 59.4 ± 17.3 and 71.2 ± 10.6% (P < 0.05); and hyposmotic test, 42.3 ± 15.8 and 56.3 ± 11.6% (P < 0.05), respectively, for T1 and T2. The pregnancy rate was higher (P < 0.05) in goats inseminated with cooled semen from T2 (66.7%) than in those inseminated with T1 (31.25%). The number of the offspring did not differ (P > 0.05) between treatments (1.3 ± 0.5 and 1.4 ± 0.5 kids, forT1 andT2, respectively). The interpretation was that the goat semen diluted, cooled, and stored in citrate-egg yolk extender prepared with a low (2.5%) concentration of egg yolk produced higher pregnancy rate and the tests of semen quality were sensitive to assess this difference. Financial support was provided by CnPQ (Brazil).