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The influence of the winter plane of nutrition on the growth rate and subsequent parturient behavior of beef heifers Kansky, Ladislav Leo

Abstract

Four groups of weanling Hereford heifers were placed on four different winter planes of nutrition for a period of two years according to the following pattern: Group I - Low plane of nutrition Group II - Medium-low plane of nutrition Group III - Medium-high plane of nutrition Group IV - High plane of nutrition During the summer seasons the heifers were kept on pasture providing the same feeding level for all animals. The one year old heifers were bred during the months of June and July. All animals were weighed weekly and feed consumption was recorded weekly. To illustrate the growth rate of the heifers, K-values were calculated for all animals by the method of least squares and their growth curves were constructed. At the end of the second winter period all parturition data were carefully recorded and the rate of growth of the calves studied. From the results obtained in this experiment the following conclusions can be drawn: (1) The first post-weaning winter period is very important in regard to the feeding level of young growing heifers. The medium-low plane of nutrition (Group II) showed the best results from the economic point of view. (2) Young heifers can be bred as yearlings if the previous winter-feeding level allows them to grow continuously and to reach at least 700 pounds body weight before the breeding period starts. (3) The gestation period did not result in a decreased growth rate of the bred heifers. (4) The physical difficulties of parturition in two year old heifers do not appear to be insurmountable if the winter plane of nutrition is adequate. (5) The lactation period means a heavy drain on the young female hence a high level of nutrition must be provided in terms of sufficient amount of pasture dry matter during the grazing season. (6) Average birth weight of calves was 62.9 pounds, being higher for bull calves than heifer calves. (7) Pasture dry matter requirements for beef cattle may be calculated from the following equation: DM = 0.17 w•⁷ (w is animal weight given in pounds)

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