Genetic analysis of somatic cell score and udder type traits in South African Holstein cows

Abstract

Selection accuracy for resistance to mastitis may be increased by combining somatic cell score (SCS) and udder type into an udder health index, using genetic parameter estimates among them. A multi-trait animal model was used to estimate genetic parameters among lactation average SCS and udder type traits in South African Holstein cattle, through REML procedures. Data comprised records on 22 999 Holstein cows in 722 herds, collected through the National Milk Recording Scheme from 1996 to 2002. Average SCS in the first three lactations (SCS 1 , SCS 2 , SCS 3 ) were considered as different traits and the udder type traits were fore udder attachment (FUA), rear udder height (RUH), udder cleft (UC), udder depth (UD), fore teat length (FTL) and fore teat placement (FTP). Heritability estimates for SCS were 0.19 ± 0.02, 0.17 ± 0.02 and 0.19 ± 0.02, respectively for SCS 1 , SCS 2 and SCS 3 . Udder type traits had heritability estimates ranging from 0.13 ± 0.01 for UC to 0.34 ± 0.01 for FTL. The genetic correlations between lactation SCS ranged from 0.82 ± 0.04 to 0.99 ± 0.03 for correlations of SCS 3 with SCS 1 and SCS 2 , respectively. Genetic correlations between SCS and udder type traits were in the range -0.01 ± 0.07 between FUA and SCS 3 to -0.38 ± 0.04 between UD and SCS 1 and SCS 2 . Slow genetic progress is expected when selection is applied independently on SCS and udder type traits, due to the generally low heritability estimates. Low, shallow udders with narrowly placed teats are associated with low SCS in the South African Holstein population. _______________________________________________________________________________________

An analysis of the genetic relationship between udder health and udder conformation traits in South African Jersey cows

“…2 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 Year Genetic correlations among lactation SCS The genetic correlations among lactation SCS were similar to those reported by Reents et al (1995), Poso and Mantysaari (1996), Boettcher et al (1998), Carlen et al (2004 and Mostert et al (2004). In addition Dube et al (2008) reported similar findings in South African Holstein cattle. Mrode and Swanson (2003) however obtained lower correlations for lactation one with lactations two and three.…”

“…Heritability estimates of SCS Estimates of heritabilities reflect the generally low heritability of SCS, in agreement with most other studies (Reents et al, 1995;Serrano et al, 2003;Mostert et al, 2004;Dube et al, 2008). Estimates are similar to those obtained using lactation SCS averages but higher than those from individual test-day models.…”

“…Estimates were however within the range of those obtained by Rupp andBoichard (1999), DeGroot et al (2002) and Dube et al (2008). The results suggest that deep, loosely attached udders with widely placed rear teats are associated with high SCS.…”

“…Trends of SCS The increases in genetic trends for SCS are similar to those reported by Dube et al (2008) and indicate deterioration in resistance to mastitis. These trends may be a correlated response to intense selection for increased milk yield, which has remarkably increased genetic merit for milk yield in the past two decades 2006b).…”

“…Heritability estimates of udder-type traits The heritability estimates obtained in this study compared well with those obtained recently in the same population (Theron and as well as in several other studies (Boettcher et al, 1998;Fuerst-Waltl et al, 1998;Setati et al, 2004;Dube et al, 2008). Monardes et al (1990) obtained much lower estimates for FUA, UC, fore and RTPs.…”