Nutritional supplementation improves the sexual response of bucks exposed to long days in semi-extensive management and their ability to stimulate reproduction in goats

In confined management systems, well-nourished bucks rendered sexually active by exposure to long days are efficient in fertilizing out-of-season goats. However, underfeeding is common in semi-extensive management systems and may reduce the reproductive efficiency of bucks. The objective of the present study was to determine whether nutritional supplementation improved the sexual activity of bucks submitted to long days in semi-extensive management systems and their ability to stimulate the reproduction of goats in semi-extensive or confined conditions. In experiment 1, three groups of bucks were placed in different flocks and grazed daily with females for 7 h. Each day after grazing, males were separated from females and moved into open pens. One group did not receive any treatment (control group; n = 6). Two other groups were submitted to artificially long days from 15 November to 15 January. From 16 January, one group did not receive nutritional supplementation (long-day group; n = 5), whereas bucks from the other group each received 600 g of a commercial concentrate (long-day+supplementation group; n = 5). The fourth group was kept in confined conditions, exposed to long days and fed alfalfa hay (long-day confined group; n = 6). On 26 March, anovulatory goats from other flocks were assigned to four groups (n = 27 each) and confined separately in open pens. Three bucks of each group were housed with the females. Pregnancy rates were greater in the goats housed with the long-day group than those housed with the control group (P < 0.01). However, pregnancy rates did not differ between the long-day confined group (89%) and long-day+supplementation group (70%; P = 0.09), but these rates were greater than those from the long-day (37%) and control groups (0%; P < 0.05). In experiment 2, two groups of males (n = 3 each) were incorporated into two flocks under semi-extensive management and grazed daily with females for 7 h. One group of males did not receive any treatment (control group). The other group was submitted to long days and nutritional supplementation as in experiment 1 (long-day+supplementation group). Males remained with females during the whole study. The pregnancy rate was greater in the goats joined by males of the long-day+supplementation group (78%) than in those from the control group (0%; P < 0.001). We conclude that long days and nutritional supplementation improve the ability of bucks kept in semi-extensive management to stimulate reproduction of out-of-season goats in confined or semi-extensive management systems.

Male effect using photostimulated bucks and nutritional supplementation advance puberty in goats under semi-extensive management

Well-nourished spring-born female goats reach puberty in the autumn of the same year. Contrastingly, undernourished spring-born females reach puberty in the autumn of the following year. Therefore, in this study, we reared female goats (undernourished) under semi-extensive management and determined whether the introduction of photostimulated, sexually active males, advances puberty in these females, and whether nutritional supplementation increases the proportion of kidding females. Goats were born on March 30 and weaned at 2 months of age. Then, they grazed natural vegetation from 10:00 to 18:00 each day. Starting in December, two groups did not receive feed supplementation after grazing, whereas two other groups received 600 g daily supplements of a commercial concentrate. In April, one non-supplemented (n = 10) and other supplemented groups (n = 11) were moved indoors and kept in separate pens, where they were joined with sexually active bucks (n = 1 per group). Males were rotated daily between groups for 7 days. Other non-supplemented (n = 8) and supplemented groups (n = 11) were not joined with males. Most of the female goats under study reached puberty (70-100%). However, in supplemented and non-supplemented groups joined with males, puberty commenced much earlier (April) than in those non-exposed to males (September) (P < 0.001). The proportion of pregnant goats did not differ between groups joined with males (P > 0.05), but the proportion of goats that kidded was higher in supplemented (7/11) than in non-supplemented goats (2/10) (P < 0.05). In conclusion, in spring-born goats, the male effect using sexually active males advanced puberty, and nutritional supplementation increased the proportion of kidding goats in females reared under semi-extensive management.

Progesterone doses of 5, 3 or 1 mg do not prevent short ovulatory cycles in goats exposed to photo-stimulated bucks

The aim of this study was to determine whether lower doses than 25 mg of progesterone reduce the frequency of short ovulatory cycles in seasonal anestrous goats exposed to sexually active bucks. Females from the control group were given an im dose of 2 mL olive oil (n = 9). Females from the experimental groups were given an im dose of 1 mg (n = 15), 3 mg (n = 16), 5 mg (n = 15) or 25 mg (n = 16) of progesterone diluted in 2 mL olive oil, 48 h prior exposition to bucks (n = 1 per group). Males were daily switched among groups, and they remained with goats during 21 days. The proportion of goats that ovulated was high (≥87%), and was not different among groups (P > 0.05). In contrast, the proportion of goats that displayed short ovulatory cycles differed among groups (P < 0.05). Indeed, the proportion of goats displaying short ovulatory cycles was lower in those treated with 25 mg (12%) than in those from the control (78%), 1 mg (85%), 3 mg (50%), or 5 mg (71%) groups (P < 0.05), but there were no differences among these last four groups (P > 0.05). Finally, the percentage of kidding females (≥40%) and the number of kids born per female (≥1.4) did not differ among groups (P > 0.05). In conclusion, an im dose of 25 mg of progesterone was more effective than 5, 3 or 1 mg to avoid the short ovulatory cycles in seasonal anestrous goats exposed to the male effect.