Genetic parameters for milk components including lactose from test day records in the New Zealand dairy herd

Abstract

There are currently few published estimates of genetic parameters for lactose yield or lactose percentage for dairy cows. Recent trends in milk standardisation for whole milk powder have resulted in whole milk being standardised with the ratio of protein to protein-plus-lactose of at least 0.39. Currently whole milk powder produced from New Zealand milk has a protein to protein-plus-lactose ratio of 0.43, thus requiring additional lactose to be imported to maximise the return from the current product portfolio. Estimates of genetic parameters were obtained using 15,366 test day records from 4378 first-lactation cows in the Livestock Improvement Corporation sire proving scheme in the 2011-12 dairy season, distributed across 70 herds. These data included milk, fat, protein and lactose yields; fat, protein and lactose percentages; somatic cell count; days in milk; and the protein to fat ratio and protein to proteinplus-lactose ratio. Mean milk yield was 13.8 L/day, containing 5.16% fat, 3.93% protein and 5.12% lactose. Heritability estimates were 0.22, 0.35, 0.32 and 0.25 for milk yield, fat, protein and lactose percentages, respectively, which were lower than those reported in the literature but enough to allow for selection of lactose percentage.

Genetic parameter estimation to milk yield and fat and protein yield deviated from 3% of concentration in milk, in dairy herds of southern Chile

“…Phenotypic correlations found in this study (table 3) are much different than those of Sneddon et al (2015) who reported phenotypic correlations among milk yield and fat and protein yield of 0.75 and 0.92, respectively. Similar findings, for pure bred Holstein cows, were reported by Elzo et al (2004) where the correlations, in the same order, were estimated at 0.82 and 0.88.…”

“…These results are very close to the average between estimates of Lembeye et al (2016 b ) for fat and protein yield (0.25±0.010), and fat and protein percentage (0.66±0.009). Sneddon et al (2015) found heritabilities, for fat and protein percentage, at 0.35±0.05 and 0.32±0.05, respectively, which are lower than the estimates presented in this research. The estimates of Elzo et al (2004) for fat and protein yield in Chilean cows ranged from 0.29 to 0.37 and 0.17 and 0.24, respectively.…”

“…Uribe and Smulders (2004) found that heritability of milk yield for Chilean Overo Colorado cattle was 0.25, which is also higher than the estimated heritability reported in this study. However, Sneddon et al (2015) analysing 15,366 test day records of 4,378 New Zealand cows born in 2009 reported a hereditability estimate of 0.19, which is closer to the heritability reported in this study. Higher heritability estimates, for milk yield, were found by Lembeye et al (2016 b ) they were at 0.33 and 0.36 for once-and twice-a-day milking cows, respectively.…”

“…Although the fat and protein traits reviewed here and reported by previous researchers are not exactly the same as the ones used in this work, it seems that fat and protein yield deviated from 3% of concentration in milk follow similar behaviour for fat and protein percentage; this may help to explain the higher heritability of fat and protein yield deviated from 3% of concentration in milk, when compared to fat and protein yields. Genetic correlations among milk yield and milk solids yield has been usually found positive and high (Elzo et al 2004a,b , Sneddon et al 2015 however, genetic correlations among milk yield and milk solids percentage have been found negative (Lembeye et al 2016 b ;Sneddon et al 2015). In this work the correlations among fat and protein yield, deviated from 3% of concentration in milk, and milk yield were negative (table 3), these findings might indicate that the behavior of the traits analysed here is closer to solids concentration than to solids yield.…”

Predicted dairy product yields and deficits of lactose for manufacturing under differing selection and manufacturing scenarios in New Zealand

“…Genetic gain per year was predicted to remain as published by NZAEL (2013) at 44 L of milk, 2.22 kg fat, 1.82 kg protein and −0.039 kg live weight for the 2013-2014 dairy season. Genetic gain in lactose percentage was assumed to be unchanged by selection on BW, this was assumed from the high genetic correlation (0.98-0.99 between milk and lactose yields) (Hossein-Zadeh & Ardalan 2011; Miglior et al 2007;Sneddon et al 2012Sneddon et al , 2014cWelper & Freeman 1992), which resulted in lactose gains of 2.07 kg per year, which is 4.7% of the 44 L gain in milk yield. Improvement of productive performance caused by better feeding, supplementary feeding or management was not considered in the simulation.…”