Genetic Parameters and Responses of Linear Type, Yield Traits, and Somatic Cell Scores to Divergent Selection for Predicted Transmitting Ability for Type in Holsteins

Abstract

The objective was to examine the direct and correlated responses of linear type, yield traits, and somatic cell scores (SCS) to divergent selection for predicted transmitting ability for type (PTAT) in Holsteins, while maintaining selection for yield traits across lines. For four generations, one-half of the University of Nebraska research Holstein herd was bred to Holstein sires with PTAT > 1.50 and the other half to sires with PTAT < 1.25, with nearly equal predicted transmitting abilities for yield traits for both groups. Estimates of genetic and residual correlations and heritabilities were obtained from REML estimates of (co)variance components. Model for type traits included fixed effect of date cows were classified, effects of age in days at freshening, and stage of lactation at classification. Year-season when cows freshened was fixed effect in model for yield and SCS. Animal genetic and residual effects were random. Final score, milk, fat, and protein yields, and SCS had heritability estimates of 0.38, 0.13, 0.22, 0.09, and 0.38, respectively. Heritability estimates for type traits ranged from 0.04 to 0.52. Estimates of genetic correlations of final score with SCS and milk, fat, and protein yields were −0.64, 0.01, −0.18, and 0.06, respectively. Estimates of genetic correlations among linear type traits ranged from −0.77 to 1.00. Means of estimated breeding values for final score, stature, strength, body depth, fore udder attachment, rear udder height and width, udder cleft, udder depth, and front teat placement were significantly different between lines in the third generation. Milk, fat, and protein yields were not significantly different between lines in third generation, whereas SCS was significantly different. Estimate of genetic correlation between final score and SCS sug-

Heritabilities and genetic correlations of lactational and daily somatic cell score with conformation traits in Polish Holstein cattle

“…Heritabilities of linear type traits were higher than estimates reported by Dal Zotto et al (2007) and Zavadilová et al (2009), and similar to or lower than heritabilities obtained by Boettcher et al (1998), DeGroot et al (2002) or De Haas et al (2007). Estimates of udder and teat trait heritabilities were very close to those reported by Rupp and Boichard (1999), except h 2 for fore udder attachment (0.18).…”

“…Generally, LSCS and leg traits were not genetically correlated in Polish Holstein-Friesian cattle, whereas DeGroot et al (2002) obtained favourable close genetic relationships between those traits (-0.61 for rear legs -rear view and rear legs -side view; -0.48 for foot angle), and Berry et al (2004) only for foot angle (-0.53). Rear legs -side view showed a positive genetic correlation with DSCS (0.14), indicating that sickled legs were associated with a high somatic cell count in milk.…”

“…These results were in agreement with Boettcher et al (1998), Mrode et al (1998) and Kadamideen (2004), who reported significant correlations of LSCS with udder depth (-0.26, -0.19 and -0.12, respectively), and of a similar magnitude with fore udder attachment. DeGroot et al (2002) also found close relationships of LSCS with udder depth (-0.20) and fore udder attachment (-0.24), whereas Berry et al (2004) obtained a similar correlation only for fore udder attachment (-0.25) and a much weaker genetic relationship for udder depth (-0.07). Lower SCS for more tightly attached, shallower and higher rear udders were observed by Nĕmcová et al (2007) in Czech Holstein cows.…”

“…Charfeddine et al (1997), Kadarmideen (2004), and Ptak et al (2009a) obtained lower h 2 for LSCS (0.13-0.14); Berry et al (2004) reported even much lower h 2 (0.07) but they did not impose any restrictions on the number of SCS tests per lactation used for calculating LSCS. DeGroot et al (2002) obtained relatively high heritability for LSCS (0.38) but their data were restricted to one dairy research herd and were preadjusted for age, season of calving and length of lactation before analysis. Th e diff erences between h 2 estimates may be attributable mainly to diff erences among the models used for statistical analyses, the population sizes in the studies, restrictions imposed on data, and the defi nitions of the analysed traits (Rupp and Boichard, 1999).…”

Genetic parameters for type traits in Holstein cows in Brazil

“…Several studies (DeGroot et al, 2002;Peres-Cabal et al, 2006;Lagrotta et al, 2010) have shown that the emphasis of selection for increased milk production may result in a decrease in the merit of some traits of type and influence the health of cows, resulting in decreased productive life (longevity) and involuntary culling by factors such as non-productive systems related to udder, reproductive, structural and locomotive issues. In this context, type traits have a direct influence on the management of cows and are related to the profitability of the herd (Berry et al, 2005;Darili et al, 2008), suggesting the importance of studies aimed at reducing involuntary culling and selection for resistant animals.…”