Stimulation of reproductive activity in anovulatory Alpine goats exposed to bucks treated only with artificially long days.

ABSTRACT

Two experiments were conducted in a subtropical latitude to determine the response of Alpine male goats to a treatment with artificially long days (experiment 1), and the response of anovulatory lactating Alpine does exposed to males treated only with artificially long days (experiment 2). In experiment 1, one group of males was kept under natural photoperiod (n = 4) while another was exposed to 2.5 months of artificially long days (16 h of light/day) from 1 December (n = 4). Plasma testosterone concentrations were determined weekly. Intensity of odor of males was determined every 2 weeks. Sexual behavior of bucks was observed during 3 days about 90 days after the end of the long day treatment. A treatment-by-time interaction was detected for testosterone secretion (P < 0.001). In control males, low plasma concentrations of testosterone were observed from March to June. In contrast, in long-day treated males, high levels of testosterone were observed from March to June (P < 0.05). A treatment-by-time interaction was detected for the intensity of male odor (P < 0.01). The male odor was stronger in long-day treated bucks than in untreated ones from March to June (P < 0.05). The number of ano-genital sniffing, nudging and flehmen was greater in long-day treated males than in untreated ones when exposed to anestrous does (P < 0.05). In experiment 2, one group of males was left under natural photoperiod variations (n = 5) and the other (n = 5) was submitted to the same photoperiodic treatment described in experiment 1. On 3 May, three untreated and three long-day treated males were put in contact with anestrous Alpine does left under natural photoperiod. Fertility was higher in does exposed to light-treated males (36/45, 80%) than those in contact with untreated ones (3/45, 7%; P < 0.05). Prolificacy was similar (P > 0.05) in does exposed to treated (1.8 ± 0.1) and untreated males (1.7 ± 0.3). These results indicate that the sexual activity of Alpine male goats raised in subtropical latitudes can be induced using only artificially long days and that such males are effective in stimulating reproductive activity in anovulatory females in late spring.