Effect of Heat Stress On Nonreturn Rate in Holstein Cows: Genetic Analyses

Abstract

The genetic component in heat tolerance for nonreturn rate in Holsteins was estimated using an animal linear model augmented by a random regression on a temperature-humidity index (THI). Data consisted of 18,059 nonreturn rates at 45,60, and 90 d after insemination and 81,674 first-parity test-day milk yields from 78 herds in Florida. The THI on the day of insemination or test day was added to each record. Only first-insemination records were used. The model for nonreturn rate included the effects of herd-year-season, age, days in milk, milk yield, THI as a covariable, regular additive effect, and random regression on THI for heat-tolerance additive effect. With a single-trait model, heritability estimates for NR45, NR60, and NR90 at THI = 70 for first-lactation cows were 0.006, 0.014, and 0.053, respectively. Genetic correlation between regular NR90 and heat tolerance was -0.95. A bivariate analysis for NR90 and test-day milk production yielded a correlation between regular merit and heat tolerance for NR90 of -0.35, substantially lower than by the univariate model, indicating a bias in the univariate estimates caused by ignored selection. The regular genetic correlation between NR90 and milk yield was -0.41. Genetic correlation between heat tolerance for NR90 and heat tolerance for milk yield was -0.04, indicating the need to separate selection.

Genetics of Ascites Resistance and Tolerance in Chicken: A Random Regression Approach

“…The EBVs can be used for selecting genetically superior individuals but also in gene mapping studies. We applied the plateau-linear model of Ravagnolo and Misztal (2000a,b), yet an alternative would have been a mixture model analysis (Zerehdaran et al 2006), which would assume heart ratio has two underlying distributions, one for healthy and one for affected birds whose growth is different affected. So far, the challenge in animal science has been that resistance and tolerance are difficult to uncouple, and the traits may be confounded in trait recording.…”

“…It is expected that body weight is reduced only in affected animals with heart ratio greater than 27% to 30%, whereas in healthy animals no relationship between heart ratio and body weight should exist. To make such a plateau-linear model (Ravagnolo and Misztal 2000a,b), heart ratio equal to or below 29% was coded as zero, and heart ratio greater than 29% was coded as: RATIO-29%. This corrected heart ratio (trait: RATIOPlat) was then used as an x -axis in the tolerance analysis.…”

“…In farm animal science, tolerance is sometimes called resilience (Riffkin and Dobson 1979; Albers et al 1987; Bisset and Morris 1996). In addition to pathogens, tolerance can be assessed against abiotic factors such as heavy metals, temperature, frost damage, or against production diseases causing damage to body tissues (Ravagnolo and Misztal 2000a,b; Schat et al 2002; Agrawal et al 2004; Kause 2011; Bloemhof et al 2012). In farmed plant and animal species, both increased resistance and tolerance serve as ways to insure global food security.…”

Metabolic and hormonal acclimation to heat stress in domesticated ruminants

“…Moreover, heat stress may reduce summer fertility in dairy and beef cows by causing poor estrous expression due to reduced estradiol secretion from the dominant follicle developed in a low luteinizing hormone environment (Biggers et al, 1987; De Rensis and Scaramuzzi, 2003;Amundson et al, 2006). About a 20% to 27% drop in conception rates (Lucy, 2002; Chebel et al, 2004) or decrease in 90-day non-return rate to the first service in lactating dairy cows (Al-Katanani et al, 1999;Ravagnolo and Misztal, 2002) occurs in summer. Roy and Prakash (2007) reported a lower plasma progesterone and higher prolactin concentration during estrous cycle in heat-stressed Murrah buffalo heifers.…”

Utilization of farm animal genetic resources in a changing agro-ecological environment in the Nordic countries

“…In addition, modern highly productive farm animal breeds, which typically show increased metabolic heat production may tolerate extreme climatic conditions less well than moderate and low-output breeds (Nardone et al, 2006; Hoffman, 2010 and references therein). Ravagnolo and Misztal (2002) showed that there is genetic variation among individual (Holstein) cows in their heat stress sensitivity, both with respect to milk yield and fertility, and that high-yielding cows were more prone to decrease their production when heat stressed. The heat stress sensitivity for milk yield was, however, not genetically correlated to that for fertility, and the authors hypothesize that different metabolic and physiological processes are responsible for heat tolerance for these two traits.…”