The concept of maternal effects on size and growth of beef cattle
offspring was probably based on studies of growth behavior in the horse.
Research in the United Kingdom (Walton and Hammond, 9) showed that
crossbred foals from Shetland mares were smaller at birth and remained
smaller at all subsequent stages of development than their reciprocal
crosses from Shire mares. This was attributed to the fact that leg length
from the knee and hock downwards increased very little after birth, and
the size to which the reciprocal crosses grew was affected accordingly.
However, beef cattle research (Joubert, 2) showed that the knee and
hock heights increased by 55.9% and 56.0% respectively from birth to
maturity, which indicates that differences in size at birth may not remain
permanent but might be altered by compensatory growth.
 Further research on maternal influence by Joubert and Hammond (3)
utilized two breeds of beef cattle of an extreme size difference, the South
Devon and Dexter. The average adult South Devon female weighed 1568
lb (712 kg) and the Dexter 650 lb (295 kg), a difference of 241%. Birth
weight of Dexter calves was 51.8 lb (23.5 kg), whereas for South Devon
calves it was 100.3 lb (45.5 kg), a 96.3% difference. Reciprocal crossbred
calves from South Devon cows weighed 12.5% more at birth than calves
from Dexter cows. The difference increased to 28.6% at 7 months of age
and was 16.5% at 12 months. Results from this study show that maternal
effects due to dam size exist in the offspring and could continue into adult
life.
 Actual cow weights may not be the true genetic size of the breeds used
in this study. The variations in environmental conditions existing in the
United States could be involved in producing important effects of geno-
type-environment interaction on actual weight. In Montana (Pahnish et
al., 4), Charolais cows were only 10% heavier than Angus, whereas in
Missouri (Sagebiel et al., 7) the difference was 23%, and at Ona, Florida
(Peacock et al., 6), the difference was 26%.
 The results from this study and those from the United Kingdom on
 crossing breeds with large variations in genetic size show that maternal
 effects on size are transmitted to offspring when genetic effects are
 additive and performance of offspring is void of heterosis. However,
 when crossing genetically divergent breeds where a high degree of heter-
 osis for growth is obtained, maternal effects on size could be masked.
 Even though maternal effects might occur in the first cross, these effects
 would diminish in the next generation (offspring from F, cross females),
 with little grand-dam maternal effects in the offspring.