Weight, growth and maturing characteristics of Kenya Sahiwal cattle

Vita.Pedigree Sahiwal cattle data kept at the National Animal Husbandry Research Station, Naivasha, Kenya from 1964 through 1983 were analyzed to identify the main factors affecting weight, growth and maturing patterns and to estimate genetic parameters of the herd. Number of records analyzed ranged from 6022 for birth weight to 1108 for maturing patterns. Sire and birth year affected all characteristics studied. Birth year x season interaction also affected all characters except degree of maturity at birth. Season affected cow and calf weights at birth and growth to 27 mo of age. Parity and preceding calving interval affected cow and calf weights at birth with the effect of the latter influencing calf growth to 55 kg. Calf sex affected cow and calf weights at birth. Sex effect on calf growth persisted up to 125 kg. The cattle exhibited the following weights: 22.9 [plus or minus] .09, 284.2 [plus or minus] 1.6, 410.9 [plus or minus] 1.8 and 423.5 [plus or minus] 1.9 kg for mean birth, 27 mo, parturition and mature weight (MW), respectively. Mean absolute growth rates were 339.5 [plus or minus] 2.9, 409.7 [plus or minus] 3.3, 329.0 [plus or minus] 9.6 and 379.8 [plus or minus] 7.0 g/d from birth to 55 kg, 55 to 125 kg, 125 kg to 27 mo and from birth to 27 mo age intervals, respectively. Corresponding relative growth rates for three periods were .930 [plus or minus] .009, .575 [plus or minus] .004, .155 [plus or minus] .003 and .330 [plus or minus] .003%/d. Average maturing rates were .087, .111 and .069%MW/d from birth to 55 kg, 55 to 125 kg and from 125 kg to 27 mo weight, respectively. Degrees of maturity were 5.2 [plus or minus] .04, 13.1 [plus or minus] .06, 29.8 [plus or minus] .13 and 65.2 [plus or minus] .31% for birth, 55 kg, 125 kg and 27 mo weight, respectively. Heritability estimates ranged from .036 (DEMA) to .391 (DAW567) and were relatively higher for growth and weight than for maturing characters. Heifer selection based on absolute growth rates from birth to 27 mo or from 125 kg to 27 mo was most appropriate for the herd. Animals heavier at any stage were also more mature at that stage and more mature animals at early stages were lighter at maturity. Faster growing animals postnatal were also heavier at maturity. Genetic phenotypic correlations between growth rates and milk yield were nonsignificant