Maternal Effect on Birth Weight in South Devon − Dexter Cattle Crosses

Abstract

IN reciprocal crosses between the Shire horse and Shetland pony, representing respectively extremes in large and small breeds, Walton and Hammond¹ demonstrated that the size of the offspring at birth and the placental weight are directly proportional to the size of the dam, and not simply intermediate between the sizes of the parent breeds. Hammond² postulated that the limitation of size in the cross-bred fœtus carried in the small mother is possibly brought about by a higher rate of metabolism of maternal tissues, as compared with a lower rate in the large breed. Otherwise, it was argued, special growth substances of maternal origin may be involved.