Breeding values for daily dry matter intake in Norwegian Red dairy cows and correlation to other traits
The current study aimed to estimate genetic parameters of feed intake in Norwegian Red (NR) dairy cows. Data from eight commercial herds with equipment for monitoring individual roughage intake was available. Our aim was also to predict breeding values (EBV) for feed intake in lactating cows and calculate index correlations to other traits in the Total Merit index (TMI) for NR. Data on daily feed intake from roughage and concentrates together with results from weekly feed analyses were used to compute daily dry matter intake (dDMI) kg. A total of 557 NR cows with 61 321 records on feed intake from January to October 2022 were analysed. The mean dDMI was 20.37 kg. A linear animal repeatability model was used to estimate variance components. The estimated heritability (standard error) of dDMI was 0.18 (0.04). The EBV’s for dDMI varied from -3.32 to 3.65 (±1.2), with significant differences between individuals. Index correlations between cows EBV’s for dDMI with other traits in the breeding goal of NR were calculated. The index correlations were in general low, ranging from -0.21 to 0.34, the strongest correlation was between 305-day protein yield and EBV for dDMI. Milk yield and body exterior traits had positive index correlations to dDMI. On the contrary, indexes for health and fertility were negatively correlated with EBV for dDMI. Although index correlations between dDMI and other traits for NR cows were not strong, our results indicate that dry matter intake are correlated with production, body exterior, fertility and health traits. We need more knowledge on the effects of selecting for novel feed intake traits, and how we best can define feed efficiency in Norwegian Red needs to be addressed. Our results so far show individual variation of feed intake capacity amongst Norwegian Red dairy cows. More phenotypes on more cows are needed to estimate genetic correlations, as well as increased knowledge on how to balance feed efficiency with production, health and fertility in the current breeding goal of Norwegian Red.
Key words: Feed intake, heritability, dairy cows, index correlations
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