Genetic parameters of milking frequency and milk production traits in Canadian Holsteins milked by an automated milking system

Abstract

Twice-a-day milking is currently the most frequently used milking schedule in Canadian dairy cattle. However, with an automated milking system (AMS), dairy cows can be milked more frequently. The objective of this study was to estimate genetic parameters for milking frequency and for production traits of cows milked within an AMS. Data were 141,927 daily records of 953 primiparous Holstein cows from 14 farms in Ontario and Quebec. Most cows visited the AMS 2 (46%) or 3 (37%) times a day. A 2-trait [daily (24-h) milking frequency and daily (24-h) milk yield] random regression daily animal model and a multiple-trait (milk, fat, protein yields, somatic cell score, and milking frequency) random regression test-day animal model were used for the estimation of (co)variance components. Both models included fixed effect of herd x test-date, fixed regressions on days in milk (DIM) nested within age at calving by season of calving, and random regressions for additive genetic and permanent environmental effects. Both fixed and random regressions were fitted with fourth-order Legendre polynomials on DIM. The number of cows in the multiple-trait test-day model was smaller compared with the daily animal model. Heritabilities from the daily model for daily (24-h) milking frequency and daily (24-h) milk yield ranged between 0.02 and 0.08 and 0.14 and 0.20, respectively. Genetic correlations between daily (24-h) milk yield and daily (24-h) milking frequency were largest at the end of lactation (0.80) and smallest in mid-lactation (0.27). Heritabilities from the test-day model for test-day milking frequency, milk, fat and protein yield, and somatic cell score were 0.14, 0.26, 0.20, 0.21, and 0.20, respectively. The genetic correlation was positive between test-day milking frequency and official test-day milk, fat, and protein yields, and negative between official test-day somatic cell score and test-day milking frequency.

Genetic parameters between feed-intake-related traits and conformation in 2 separate dairy populations—the Netherlands and United States

“…The estimated genetic variances and heritabilities of MY were in the range reported in the literature Berry et al, 2003b;Kadarmideen and Wegmann, 2003;Muller et al, 2006;Nixon et al, 2009;Liinamo et al, 2012). The estimated heritabilities for BW were also in the range of literature from 0.43 to 0.65 (Veerkamp and Brotherstone, 1997;Koenen and Veerkamp, 1998;Berry et al, 2003b;Muller et al, 2006;Dechow et al, 2010).…”

Genetic and environmental determinants of the urea level in cow's milk

“…1 confirm that there is a changing effect of genetic factors on MU during lactation. The resultant curve is similar to that presented by other authors in relation to milk yield and milk content (Nixon et al, 2009;Strabel and Misztal, 1999).…”

Changes in milking parameters with robotic milking

“…André et al (2010) emphasised that a higher MCD value and herd size may increase revenues from an AMS, but this strategy is related primarily to the milk yield of individual animals. As emphasised by Nixon et al (2009), following the introduction of an AMS, the intermilking intervals may vary widely, from very short to very long, depending on the animal. A study by Klaas et al (2003) concluded that high-yielding cows receive a large proportion of concentrates during milking in the AMS, which induced them to go to the milking machine more frequently.…”