Genetic parameters for serial, automatically recorded milkability and its relationship to udder health in dairy cattle

Abstract

Serial measurements of three milkability traits from two commercial dairy farms in Germany were used to estimate heritabilities and breeding values (BVs). Overall, 6352 cows in first, second and third lactations supplied 2 188 810 records based on daily values recorded from 1998 to 2003. Only the records between day 8 and day 305 after calving were considered. The estimated genetic correlations between different parities within the three milkability traits ranged from r g 5 0.88 to 0.98, i.e. they were sufficiently high to warrant a repeatability model. The resulting estimated heritability coefficients were h 2 5 0.42 for average milk flow, h 2 5 0.56 for maximum milk flow and h 2 5 0.38 for milking time. We analysed the genetic correlation between milkability and somatic cell score (SCS) and between milkability and the liability to mastitis, respectively, as the optimum milk flow for udder health is not well defined. There were 66 146 records with information on somatic cell count. Furthermore, 23 488 days of medical treatment for udder diseases were available, resulting in 2 600 302 days of observation in total. Heritabilities for the liability to mastitis, estimated with a test-day threshold model, were h 2 5 0.19 and h 2 5 0.13, depending on the data-recording period (first 50 days of lactation and first 305 days of lactation, respectively). With respect to the relationship between milkability and udder health, the results indicated a slight and linear correlation insofar as one can assume: the higher the milk flow, the worse the udder health. For this reason, bulls and cows with high BVs for milk flow should be excluded from breeding to avoid a deterioration of udder health. The establishment of a special data-recording scheme for functional traits such as milkability and mastitis on commercial dairy farms may be possible according to these results.

Genome-wide association study for milking speed in French Holstein cows

“…A previous study in French Holstein reported positive genetic correlations between MS and CM (0.18) and between CM and SCS (0.70; Govignon-Gion et al, 2016). Similarly, a positive genetic correlation between MS and SCC was reported by several authors [0.44 (Rupp and Boichard, 1999), 0.60 (Gäde et al, 2007), and 0.46 (Samoré et al, 2010)], indicating the existence of an unfavorable relationship between MS and mastitis. Genetic correlation between MS and SCS was similar over 2 lactations, with an average correlation of 0.62 (Boettcher et al, 1998).…”

“…Heritability of MS is moderate: h 2 = 0.17 for 305-d farmer scores in French Holstein (Rupp and Boichard, 1999) and 0.14 in Canadian Holstein (Sewalem et al, 2011). It is higher for measured milking time (e.g., 0.38 in German Holstein; Gäde et al, 2007). These values are moderate and high enough for genetic selection to be effective.…”

“…This relationship is plausible because both traits are affected by the anatomy of the teat canal. Animals with a wider teat canal and sphincter on average show a higher milk flow, but the main disadvantage is that teat canals with a greater diameter simultaneously facilitate access to pathogens (Gäde et al, 2007;Sewalem et al, 2011). Another mechanism explaining this positive correlation is that fast milking extracts more alveolar milk rich in somatic cells (Ferneborg and Svennersten-Sjaunja, 2015).…”

Random regression models using different functions to model milk flow in dairy cows

“…Hence, the use of such models could prevent considerable loss of data. Gäde et al (2007) suggested that milkability should be included in breeding deci-sions, because this parameter is related to labor efficiency and udder health. Greater milk flow is associated with a decrease in labor time, and thus a decrease in expense.…”

“…Milk flow has an intermediate optimum; hence, there is value in reducing variation around that optimum, but it is not easily accomplished. To obtain a more uniform milking duration among the cows, and to simultaneously avoid deterioration in udder health, cows with low or high milk flow should be discarded from breeding group (Gäde et al, 2007).…”