Factores que afectan la primera lactancia de vacas criollas limoneras

With the data accumulated in the Carrasquero Experimental Station during the years 1972 to 1979, the factors that affect the first lactations of 133 cows, daughters of 25 sires, fed on pasture, milked twice a day without the calf and receiving about 0.75 kg of concentrate at milking were determinated. By least squares method the effects of year, season (dry, half rainy and rainy), sire and birth weight on the weight and the age at calving, the milking period and milk production were studied. The years and seasons showed significant differences (P less than 0.01) on the weight and age at calving. The effect of sire (P less than 0.01) on the age at calving and (P less than 0.05) the weight, milking period and milk production was observed. The birth weight had high significant effect (P less than 0.01) on milk production. A higher milk production was observed in cows which birth weight oscillated between 25 and 28 kg, suggesting that this parameter could be a criterion of selection for Criollo cattle and justifies future studies. The means of birth weight, weight at calving, age at calving, milking period, total milk production and 305 days milking production were respectively: 29.9 plus or minus 3.9 kg, 332.7 plus or minus 30.7 kg, 1,347.2 plus or minus 97.1 days, 278.3 plus or minus 88.8 days, 1,440.1 plus or minus 573.8 and 1,364.2 plus or minus 491.5 kg