Garcia-Peniche, T: Comparisons of dairy breeds in the United

Dairy breeds have been thoroughly studied with respect to production and type traits, and their performance is acceptably well known. Besides, as a result of genetic selection, production traits have greatly increased through time. Contrastingly, scarce or even null improvement has occurred for other important traits, sometimes called fitness traits, which include fertility and longevity. The dairy industry is presently less concerned about production and focusing more on improving, or at least, preserving, those traits. Fertility and Longevity are complex and low heritable and can be evaluated in several indirect ways. The general objective of the research was to compare the three most abundant breeds in the United States for some fertility-related and longevity-related traits. This work comprises two studies. The first one aimed to evaluate breed differences for heat-stress resistance, and the second one ed to compare and make inferences about survival-related traits, assessing breed by region interactions for seven regions of the United States using linear and nonlinear models. This work should be of interest to anyone related to dairy science.