Selection for feed efficiency is of increasing interest for cattle breeders, and countries are combining data to develop genomic breeding values to be used across feeding systems. Also a classical question is if we should breed cows with a higher feed intake (capacity) so they can convert more roughage into milk, or should we breed cows that are efficient and have a lower feed intake for a given yield, i.e. that are more profitable (milk yield - feed intake). To answer this question genotype by environment (GxE) was investigated. Experiments with a total of 1,602 cows recorded for dry matter intake (DMI), fat-protein corrected milk (FPCM) and liveweight) (LW) were grouped into a high, medium and low nutritional environment to estimate genetic parameters. Heritability for DMI and LW were constant across the environments, for milk yield there was a decrease in h2 from high to low environment. Genetic correlations between the environments ranged between 0.68 to 0.90 for DMI, and were slightly lower for FPCM, and higher for LW. Selection index calculations demonstrated that selection for higher intake gave heavier cows, and when selecting for a higher intake relatively to milk yield on a higher density diet there was no benefit in terms of profit on lower density diets. Therefore, the breeding goals should always be for profit (FPCM – DMI) independent of the nutritional environment. Keywords: R.F. Veerkamp, feed intake, genotype by environment interaction, breeding goal, dairy cattle

Bart Ducro, Roel F Veerkamp

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Feed Intake and Efficiency 1, , 189, 2018
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