Interbreed Matings in Dairy Cattle. I. Yield Traits, Feed Efficiency, Type and Rate of Milking

Abstract

Performance and efficiency in first lactation for 88 two-breed and 49 three-breed crosses among Ayrshires, Brown Swiss, and ttolsteins were compared to the weighted mean of purebred contemporaries of the three breeds to estimate heterosis resulting from crossbreeding. All possible combinations of two-breed and three-breed crosses were included. The animals were sired by 18 Ayrshire, 18 Brown Swiss, and 17 Holstein sires selected by random drawings from among all bulls of the three breeds in regular AI service. The two-breed crosses had 4 to 15% heterosis for days open. Ayrshire Holstein and Swiss Holstein crosses were 8 to 10% above the parental mean for production traits, but Ayrshire Swiss showed no heterosis. Heterosis for measures of efficiency of feed utilization was about one-half that for production in Ayrshire Holstein and Swiss Holstein crosses, but was zero in Ayrshire Swiss crosses. In general, the estimates of heterosis for three-breed crosses were higher than for two-breed crosses. These were superior to the mean of the parental breeds by 13.8, 11.9, 13.8, 12.2, 9.2, 13.0, 12.9, 7.2, and 0.3% in days open in lactation, milk, fat, SNF, protein, FCM yields, therms produced, three measures of efficiency, and persistency of nfilk yield, respectively. The Ayrshires, Brown Swiss, and Ayrshire Swiss crosses were significantly below Holsteins in production and efficiency traits. The Ayrshire Holstein, Swiss Holstein, and three-breed crosses were slightly lower in milk and FCM yields but generally superior to Holsteins in fat yield and efficiency. These results indicate certain crossbred groups