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Background: Somatic cell score is an important parameter to predict milk quality and health of cows. However, in countries like Brazil, this trait is still not selected on a large scale, and no genetic parameters are reported in the literature. Objective: To estimate the variance components and genetic parameters for somatic cell score, milk yield, fat yield, protein yield, fat percentage, and protein percentage in Holstein cows. Methods: Records from 56,718 animals were used to estimate variance components, heritability, and genetic correlations using a multi-trait animal model by the REML method. Results: The heritability estimates were 0.19 for somatic cell score, 0.22 for milk yield, 0.26 for fat yield, 0.18 for protein yield, 0.61 for fat percentage, and 0.65 for protein percentage. The estimates of genetic correlations among analyzed traits ranged from -0.50 to 0.82. Conclusion: The low heritability observed for somatic cell score indicates that selection for this trait should result in benefits related to animal health and milk quality, but only in the long term. The low correlation between productive traits and somatic cell score indicates that inclusion of somatic cell score in animal breeding programs does not interfere negatively with the genetic selection for milk yield or solids. [ABSTRACT FROM AUTHOR]

With the aim of quantifying the genotype-environment interaction (GEI) and the phenotypic stability in multibreed bovine population of the Colombian Northwest, registries from 16 herds located in three agroecological regions (E1, E2, E3) from low tropic systems (humid subtropic forest, humid tropic forest and dry tropic forest, were collected from 1995 to 2007. Weight at 12-mo (W12), weight at 18-mo (W18), and weight at 24-mo (W24), were evaluated with 1806, 1455, and 1197 data, 14, 11, and 10 genetic groups respectively; animals of the breeds and crossbred between Angus (A), Blanco Orejinegro (B), Zebu (Z), Holstein (H), Romosinuano (R), and Senepoll (S) were used. In a mixed model, the fixed effects of contemporary group (year-season-sex) and the age covariate were used, which showed a significant effect (pCon el objetivo de cuantificar la interacción genotipo-ambiente (IGA) y la estabilidad fenotípica en una población bovina multirracial del noreste colombiano, se usaron registros de 16 rebaños localizados en tres regiones agroecológicas del trópico bajo: bosque húmedo subtropical (R1), bosque húmedo tropical (R2) y bosque seco tropical (R3), entre los años 1995 y 2007. Los pesos fueron evaluados a los 12 (P12), 18 (P18) y 24 meses (P24), con 1806, 1455 y 1197 datos, y 14, 11 y 10 grupos genéticos, respectivamente. Fueron usados animales puros y cruzados entre las razas Angus (A), Blanco Orejinegro (B), Cebú (C), Holstein (H), Romosinuano (R) y Senepol (S). Se utilizó un modelo mixto, en el que los efectos fijos de grupo contemporáneo y la edad presentaron efecto significativo (pCom o propósito de quantificar a interação genótipo ambiente (IGA) e estabilidade fenotípica em populações bovinas multiraciais no trópico baixo colombiano foram utilizados registros desde 1995 até 2007 de 16 fazendas localizadas em três regiões agroecológicas: bosque subtropical úmido (E1) bosque tropical úmido (E2) e bosque tropical seco (E3). Foram avaliadas o peso aos 12, 18 e 24 meses, com 1806, 1455 e 1197 registros, respectivamente de 10 grupos genéticos das raças Angus, Blanco Orejinegro, Zebu, Holandês, Romosinuano e Senepol. O Modelo mixto utilizado incluiu os efeitos fixos de grupo contemporâneo (ano, época e sexo) e a idade como covariavel, os quais foram significativos (p