A crossbreeding experiment with cattle, with special reference to the maternal effect in South Devon—Dexter crosses

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Abstract
An investigation was carried out to determine the extent of the maternal influence on size of calves at birth and during subsequent stages of growth, by making reciprocal matings between large South Devon and small Dexter cattle. As a preliminary to the experimental results, data concerning the respective parent breeds were analysed. From the first part of the study the following information was obtained:1. The mean weight at birth of purebred South Devon calves was 100·3 ± 1·47 lb. with a tendency, though not statistically significant, for male calves to be heavier. Calves born during the months April to July appeared to be heavier than those born at other times, but the age of the dam had no definite effect on the birth weight of offspring. It was found, however, that the sire may influence birth weight to a significant degree.2. The mean period of pregnancy for South Devon females, carrying purebred foetuses, was 287·0 ± 0·42 days, the tendency being for males to be carried longer, but the difference of 0·97 days was not statistically significant. A statistically significant difference indicated that winter calvers carry their foetuses longer as a rule, but though heifers have shorter gestation periods than cows, the difference of 1·6 days was not significant.

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