Seasonal breeding in United States dairy goats.

Effects of breed, region, and interaction of breed with region on seasonality of breeding in United States dairy goats were studied. Reproductive performance data were from 76,350 official National Cooperative Dairy Herd Improvement Program records on Alpine, La Mancha, Nubian, Saanen, and Toggenburg does. Variables were month of conception, month of kidding, days open, and deviation of kidding date from March 1. Four northern regions were: 1, greater than or equal to 45 degrees latitude; 2, 40-45 degrees; 3, 35-40 degrees; and 4, less than or equal to 35 degrees. About 20% of Nubians conceived from January through August, whereas only 10% of Alpines and of Toggenburgs conceived during those months. La Manchas conceived most frequently in November whereas other breeds conceived most frequently in October. Each breed kidded most frequently in March. In September and October, 3 to 4% more conceptions occurred in Regions 1 and 2 than in 3 and 4, whereas in November, 7.3% fewer conceptions occurred in Regions 1 and 2 than in 3 and 4. In January, 13.2% of kiddings occurred in Region 4 compared to 5.6% in Region 1. Similarly, during July through December, proportionally more kiddings (11.8%) occurred in Region 4 than in Region 1 (5.2%). In the range of latitudes studied, differences in degree of seasonality due to breed, region, and interaction, although significant, were minor.