Effect of Age at Breeding on Reproduction in Local Sheep
Forty nulliparous West African Dwarf and Permer X West African Dwarf crossbred ewes were used in two separate experiments to study the effect of eight breeding groups (6, 7, 8, 9, 10, 11, 12 and 13 months) on weight at breeding, gestation length, frequency of twinning, birth weight, frequency of stillborn, placenta weight, frequency of milk ejection and weaning weight. In the first experiment, four out of five West African Dwarf ewes in the six month age group showed heat. After breeding the estrous ewes, only one appeared pregnant but later returned to heat about 57 days post breeding. All the ewe in the 7 month age group showed heat and after breeding only one was pregnant which later aborted about 131 days post breeding. All West African Dwarf ewes bred between the ages of 8 - 13 months were pregnant and successfully went to term. There were significant differences in breeding weight and birth weight among the ewes in age group 8 - 13 months. On the whole breeding at 8 months of age appeared to have the same effect as breeding at a later age. Age and breeding weight were significantly correlated. One out of thirty fetuses (one fetus from group 10) was stillborn and there was 100% milk ejection. In the second experiment, three out of five Permer X WAD ewes assigned to the 6 month age group showed heat but after breeding none became pregnant. All ewes in 7 month age group showed heat but after breeding all showed heat regularly except two which later returned to heat 43 and 47 days (respectively) post breeding. All Permer x WAS ewes bred between the ages 8 - 13 months were pregnant and successfully went to term. Of the age groups that went to term, there was no difference amongst them in all the variables studied except in placenta weight. There was no significant correlation between age and anyone of the variables measured.