Genetic Parameters for Milk Yield and Persistency in Carora Dairy Cattle Breed Using Random Regression Model

Abstract

In tropical environments, lactation curves with lower peaks and higher persistency (PS) might be desirable from both an economical and a physiological point of view. The objective of this study was to obtain genetic parameters for test day (TD) yields, and PS for the tropical breed Carora and to compare these with results from a standard 305-d-milk yield animal model. Four random regression models (RRM) were used on a dataset composed of 95,606 TD records collected in Venezuela and tested to find the best fitting the data. Estimated daily heritabilities for milk yields ranged from 0.21 to 0.30, with the lowest values around the peak of lactation. Lactation repeatabilities ranged from 0.50 to 0.56. Correlations between the breeding values obtained with the RRM and the lactation model currently used in Venezuela [single trait Animal Model (stAM)] are quite high and positive (Pearson correlation=0.71 and Spearman correlation=0.72). Correlations between PS and 305-d-milk yield estimated breeding values (EBV) ranged from -0.18 (PS as the deviation of daily productions in the interval 50-279 days in milk from a point at the end of lactation) to 0.52 (PS as EBV difference between the second and the first stage of lactation). The use of PS indexes accounting for milk yield may allow the selection of individuals able to express their potential genetic values in tropical environment, without incurring in excessive heat stress losses.

Effects of production stage and fertility traits on milk production of pasture-grazed Holstein and Jersey cows in a Mediterranean-type climate region

“…Because of this, the lactation curve of the cows that calved in summer tended to be flatter (Figure 2), indicative of lactation persistency compared with those that calved in winter. Because cows with high lactation persistency are reported to be less susceptible to nutritional disorders and possible more fertile as a result thereof (Hickson et al, 2006;Mostert et al, 2008;Tullo et al, 2014), summer can be seen as an ideal calving season in the Western Cape.…”

Associations between Peak Yield and Peak Day with Productive and Reproductive Traits of Holstein-Friesian Dairy Cows in Egypt

“…However, Atashi et al (2013) documented that the lower peak yield and higher persistency improves cows' robustness to the stress of lactation and metabolic disorders, as a consequence of shallower energy imbalance, followed by less body reserves mobilization to meet the nutrient demand for lower milk production. Generally, under tropical environment conditions, lactation curves with lower peaks and typical peak day, subsequently higher persistency, might be desirable from both an economical and a physiological point of view (Tullo et al, 2014…”