Genetics of Grass Dry Matter Intake, Energy Balance, and Digestibility in Grazing Irish Dairy Cows

Abstract

The objective of this study was to estimate genetic parameters for grass dry matter intake (DMI), energy balance (EB), and cow internal digestibility (IDG) in grazing Holstein-Friesian dairy cows. Grass DMI was estimated up to 4 times per lactation on 1,588 lactations from 755 cows on 2 research farms in southern Ireland. Simultaneously measured milk production and BW records were used to calculate EB. Cow IDG, measured as the ratio of feed and fecal concentrations of the natural odd carbon-chain n-alkane pentatriacontane, was available on 583 lactations from 238 cows. Random regression and multitrait animal models were used to estimate residual, additive genetic and permanent environmental (co)variances across lactations. Results were similar for both models. Heritability for DMI, EB, and IDG across lactation varied from 0.10 [8 days in milk (DIM)] to 0.30 (169 DIM), from 0.06 (29 DIM) to 0.29 (305 DIM), and from 0.08 (50 DIM) to 0.45 (305 DIM), respectively, when estimated using the random regression model. Genetic correlations within each trait tended to decrease as the interval between periods compared increased for DMI and EB, whereas the correlations with IDG in early lactation were weakest when measured midlactation. The lowest correlation between any 2 periods was 0.10, -0.36, and -0.04 for DMI, EB, and IDG, respectively, suggesting the effect of different genes at different stages of lactations. Eigenvalues and associated eigenfunctions of the additive genetic covariance matrix revealed considerable genetic variation among animals in the shape of the lactation profiles for DMI, EB, and IDG. Genetic parameters presented are the first estimates from dairy cows fed predominantly grazed grass and imply that genetic improvement in DMI, EB, and IDG in Holstein-Friesian cows fed predominantly grazed grass is possible.

Analysis of feed intake and energy balance of high-yielding first lactating Holstein cows with fixed and random regression models

“…This trajectory differs from those found by Svendsen et al (1994) and Berry et al (2007), who observed increasing heritabilities. It has to be noted that a comparison with the cited studies is difficult.…”

“…The trajectory of the heritability of the dry matter intake over the lactation estimated in the present study (Table 5) is similar to the one found by Berry et al (2007) on grazing cows. An increase of the heritability to a maximum around the 110th day in milk as mentioned by Koenen and Veerkamp (1998) and Karacaö ren et al (2006) has not been identified as well as the decline of the heritability of the feed intake as published by Coffey et al (2001) andvan Elzakker andvan Arendonk (1993) could not be confirmed.…”

“…Svendsen et al (1994) used another definition of the energy balance. In the study of Berry et al (2007), who estimated the food intake of grazing cows in Ireland, a totally different system of livestock farming (feeding regime, housing) was analysed.…”

Genome-wide associations for feed utilisation complex in primiparous Holstein–Friesian dairy cows from experimental research herds in four European countries

“…Quantitative genetic studies have shown that genetic variation exists among animals in the feed utilisation complex, and in its component traits (e.g. feed intake, milk production and body weight; Veerkamp et al, 2000;Berry et al, 2007). Feed intake, as a trait, was initially targeted in breeding programs to try to reduce the quantity of feed required per unit of production, that is, improving feed efficiency.…”

“…This is primarily because of the large resource demand of measuring individual feed intake in dairy cows. This makes routine selection in breeding programmes too difficult, but also means that studies that estimated genetic parameters for the feed utilisation complex in dairy cows have generally been confined to a small number of animals from research herds (Svendsen et al, 1994;Veerkamp et al, 2000;Berry et al, 2007). As a result, there has been considerable interest in predictors of the feed utilisation complex, like, for example, BCS (Koenen et al, 2001;Banos et al, 2004;Dal Zotto et al, 2007), or other predictors of body energy state (Coffey et al, 2003).…”