Reproductive performance of Alpine dairy goats in a semi-arid environment of Mexico under a continuous breeding system

Reproductive data from an Alpine dairy goat farm in a semi-arid area of Mexico were studied from 1987 to 1993. Goats were kept at night in confinement and pastured during the day with a male present all year. Yearly distributions of kidding (n = 589) were studied by months and seasonal period (Period 1, January-March; Period 2, April-June; Period 3, July-September; Period 4, October-December). Kidding was 75% from October to January. Seasonal kidding was 27% from January to March (n = 159), 11% from April to June (n = 65), 4% from July to September (n = 24), and 58% from October to December (n = 342). Average kidding interval (KI) was 345 (+/- 70)days (n = 314), varying from 339 ( +/- 72)days in yearlings to 346 (+/- 70)days in adult goats. Seasonal KI was 324 (+/- 68)days, 262 (+/- 48)days, 481 (+/- 50)days and 364 (+/- 57)days for Period 1 (n = 82), Period 2 (n = 32), Period (n = 6) and Period 4 (n = 190), respectively, with a significant difference between periods (P < 0.05). Goats kidded for the first time at 14 months (+/- 3), litter size of goats averaged 1.69 (+/- 0.5) and seasonal distribution was 1.63 (+/- 0.5), 1.50 (+/- 0.5), 1.91 (+/- 0.3) and 1.74 (+/- 0.5), respectively. Kidding from July to September had a larger litter size. Although photoperiod is a factor governing the reproductive activity of these Alpine goats, other factors such as rain could influence the onset of the breeding season. It is concluded that with continuous male presence, seasonality in Alpine dairy goats under tropical conditions is not eliminated but some out-of-season breeding does occur. Overall, 85% of the breeding occurred between May and September. Therefore the continuous presence of a male increases the percentage of out-of-season kidding. (C) 1998 Elsevier Science B.V.