Heterogeneity in genetic variation for feed intake and adjusted feed intake between dairy cow breeds

• Dry matter intake (DMI) and adjusted feed intake (AFI) are two traits related to feed efficiency in dairy cattle. This study aimed to estimate genetic variances and genetic parameters for DMI and AFI in cows of two dairy breeds, Holstein and Jersey, by random regression methods (RR). In total, DMI observations in the first 44 lactation weeks from 813 primiparious Holstein cows and 301 primiparious Jersey cows were included. Two RR methods, RR using linear splines and RR using Legendre polynomials, were used to estimate the variance components for DMI and AFI for each breed. The analyses for AFI were carried out by adjusting DMI observations for the cows' milk yields, metabolic body weights (MBW), and the change of body weight during the 44 lactation weeks in the genetic model. The results indicated potential differences between Holstein and Jersey cows in genetic variance for DMI and AFI. The genetic variance for AFI was lower than that for DMI over the 44 lactation weeks. The genetic variance for DMI significantly increased along lactation in each breed, whereas the genetic variance was relatively stable for AFI during the 44 lactation weeks. Both DMI and AFI were moderately heritable, but the heritability for AFI tended to be lower than that for DMI. The heritability for DMI and AFI were less different between breeds compared with genetic variances. In addition, the breed difference was also shown in the regression coefficient of DMI on the change of body weight, whereas the two breeds were similar in their regression coefficients of DMI on milk yields and MBW. The results from the two RR analyses in this study showed high consistency. Based on our current findings, heterogeneity might exist between dairy breeds in genetic variation for feed intake and for AFI, which should be considered in a future multi-breed genetic evaluation for feed efficiency in dairy cattle. Additionally, adjusted feed intake could be a candidate trait for feed efficiency in dairy cattle due to its moderate heritability and its considerations on cows' milk production and body maintenance.

Ämnesord

LANTBRUKSVETENSKAPER  -- Bioteknologi med applikationer på växter och djur -- Genetik och förädling inom lantbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agricultural Biotechnology -- Genetics and Breeding in Agricultural Sciences (hsv//eng)

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