Genetic and phenotypic parameters and annual trends for milk production and fertility traits of the Sahiwal cattle in semi arid Kenya

Abstract

Data comprising 7211 lactation records of 2894 cows were used to estimate genetic and phenotypic parameters for milk production (lactation milk yield, LMY and lactation length, LL) and fertility (calving interval, CI; number of services per conception, NSC and age at first calving, AFC) traits. Genetic, environmental and phenotypic trends were also estimated. Variance components were estimated using univariate, bivariate and trivariate animal models on based restricted maximum likelihood procedures. Univariate models were used for each trait, while bivariate models were used to estimate genetic and phenotypic correlations between milk production and fertility traits and between LMY, LL, CI and NSC within each lactation. Trivariate models were used in the analysis of LMY, LL, CI and NSC in the first three lactations. Heritability estimates from the univariate model were 0.16, 0.07, 0.03, 0.04 and 0.01 for LMY, LL, CI, AFC and NSC, respectively. The heritability estimates from trivariate analysis were higher for milk production traits than those from univariate analyses. Genetic correlations were high and undesirable between milk production and fertility traits, while phenotypic correlations were correspondingly low. Genetic trends were close to zero for all traits, while environmental and phenotypic trends fluctuated over the study period.

Phenotypic and genetic parameters for selected production and reproduction traits of Mpwapwa cattle in low-input production systems

“…The repeatability for CI (0.10) was low, which is consistent with other previous studies for crossbred cows in sub-Saharan Africa (Chagunda et al, 2004;Ilatsia et al, 2007). The low genetic parameter estimates could be owing to the small number of records for CI used in this study.…”

“…Heritability estimates for 305LMY was higher than for LMY. Heritability estimates for milk production traits were within the range of previous estimates for improved zebu and crossbred cows in sub-Saharan Africa (Mwatawala et al, 2002;Demeke et al, 2004;Ilatsia et al, 2007). Heritability estimates for LMY and 305LMY were moderately high, which implies that the trait could be used for the genetic improvement of the breed via selection.…”

“…The estimates for LMY and 305LMY were higher compared with previous studies of improved zebu in low-input production systems in sub-Saharan Africa (Ilatsia et al, 2007;Badri et al, 2011). Conversely, the repeatability estimates for LL was moderate, but consistent with other studies of improved zebu in the tropics (Ilatsia et al, 2007;Badri et al, 2011;Santos et al, 2013). The repeatability estimates for production traits indicate that selection of the best cows to be kept in the herd for production could be done with some degree of precision based on estimates for LMY, 305LMY and LL of the cows.…”

“…Heritability estimates for LMY and 305LMY were moderately high, which implies that the trait could be used for the genetic improvement of the breed via selection. The heritability estimate of 0.13 ± 0.11 for AFC was higher than for Sahiwal cattle and crossbred cows (Mwatawala et al, 2002;Amimo et al, 2006;Ilatsia et al, 2007), but lower than for purebred HolsteinFriesians in Malawi (0.2) (Chagunda et al, 2004) and Kenya (0.38) (Ojango & Pollott, 2001). Heritability value for CI was low (0.10), which is similar to improved zebu and crossbreds (Mwatawala et al, 2002;Ilatsia et al, 2007), but lower than Kenyan Holstein Friesians (Ojango & Pollott, 2001).…”

“…The heritability estimate of 0.13 ± 0.11 for AFC was higher than for Sahiwal cattle and crossbred cows (Mwatawala et al, 2002;Amimo et al, 2006;Ilatsia et al, 2007), but lower than for purebred HolsteinFriesians in Malawi (0.2) (Chagunda et al, 2004) and Kenya (0.38) (Ojango & Pollott, 2001). Heritability value for CI was low (0.10), which is similar to improved zebu and crossbreds (Mwatawala et al, 2002;Ilatsia et al, 2007), but lower than Kenyan Holstein Friesians (Ojango & Pollott, 2001). 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 Heritability for AFC and CI is generally considered low, which suggests that these traits are affected by environment and other farm management polices more than additive gene action.…”