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This study was conducted to evaluate the effects of season, year of lambing, parity, and the effect of ram on litter size, birth, and weaning weight through 8 years. Data of 4078 lambs sired by 21 rams and 1072 ewes were analyzed by a lineal model. There was a significant effect (P < 0.05) of lambing number on litter size and birth weight, but not on weaning weight (P > 0.05). For litter size, the lowest numbers were obtained on the first lambing ewes (1.21 ± 0.03) and the highest ones inewes starting from the fourth lambing (1.69 ± 0.04). Lowest body weights were found in lambs born from first lambing ewes (3.01 ± 0.1 kg) and the highest ones in lambs born from the second (3.14 ± 0.1) to the fifth (3.15 ± 0.2) lambing ewes. The lambing breeding season had a significant effect on weaning weight: the highest weaning weights were recorded in lambs born in spring (12.70 ± 0.20 kg) and the lowest ones in those born in summer (11.93 ± 0.20 kg). Lambing year had a significant effect (P < 0.05) on litter size and weaning weight, since the values of both traits improved through the years. Effect of ram was significant (P < 0.05) for each of the traits considered: there were differences up to one lamb per litter, also differences up to 1.5 kg for birth weight and up to 6.5 kg for weaning weight among rams. In conclusion, these results indicate that environmental conditions are important source of variation in litter size, birth, and weaning weight in hair sheep under semi-arid climate.

The objective of this study was to evaluate sexual behaviour and semen quality of St. Croix ram lambs bred in a semi-desert region. In Experiment 1, 24 yearling rams were assigned to two groups: T1 with 12 males confined for 11 months; T2 with 12 males confined individually for the same period of time. In Experiment 2, 20 four-month-old ram lambs were assigned to two groups of 10 animals each. In each experiment, sexual behaviour and semen quality were evaluated every 2 weeks over 11 months. In Experiment 1, rams that were individually confined showed better sexual activity than lambs confined together (P<0.05), whereas in Experiment 2 ram lambs confined individually only showed shorter time to first mount with ejaculation (P<0.05). In experiment 1, sperm with better progressive motility (P<0.05) was recorded per yearling ram confined individually (63.4±0.2%) in comparison with rams confined together (51.60.1%). In Experiment 2, ram lambs confined together showed better semen quality (P˂0.05). In both trials, an effect of the season was observed on both sexual behaviour and semen quality (P<0.05). In conclusion, this study of St. Croix males showed different sexual behaviours according to age and type of enclosure.

The aim of this research was to evaluate the effectiveness of three pFSH doses (80 mg; 145 mg and 215 mg) on ovarian response and on quantity and quality of transferable embryos of goats during the breeding and the non-breeding seasons. Ovary structures were exposed (laparatomy under general anaesthesia) and numbers of follicles and corpora lutea were registered. Surgical embryo flushing was conducted to count and classify embryos. There were more follicles (3.4 ± 1.1) in does administered 80 mg of pFSH (p < 0.05) than in goats administered 145 mg of pFSH (2.2 ± 1.1) and 215 mg of pFSH (0.9 ± 0.6). Numbers of corpora lutea, blastocysts, and recovered and transferable embryos of goats administered 145 mg pFSH (13.4 ± 3.7, 2.42 ± 1.0, 3.4 ± 1.2 and 3.2 ± 1.1, respectively) and those of goats administered 215 mg pFSH (11.6 ± 2.6, 3.2 ± 0.9, 5.7 ± 1.5, and 5.6 ± 1.5) were greater (p < 0.05) than values obtained from goats administered 80 mg pFSH (4.0 ± 1.5, 0.5 ± 0.3, 1.0 ± 0.5, and 0.8 ± 0.5). Numbers of morula of does administered 80 and 145 mg pFSH (0.4 ± 0.4 and 0.8 ± 0.3) were lower (p < 0.05) than those obtained from animals treated with 215 mg pFSH (2.4 ± 0.9). There was no effect of season upon the analyzed variables. In conclusion, under the prevalent conditions in north-eastern Mexico, administration of 145 or 215 mg pFSH in a decreasing dose schedule over 3.5 days to bred goats provided a satisfactory superovulatory result.