A morphological, physiological and gentic investigation of the African pygmy goat Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/t148fm36r

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  • Six groups of goats were used in the study. These were the normal group (Saanen, French Alpine, and Nubian breeds), 1/4 pygmy group (first backcross to normal), 1/2 pygmy group (F1) 3/4 pygmy group (first backcross to pygmy), 7/8 pygmy group (second backcross to pygmy), and pygmy group0 The mean weight of the 1/2 pygmy group approximated more closely that of the normal group than that of the pygmy group. The mean weight of the 1/4 pygmy group approximated that of the normal group more closely than the mean weight of the 1/2 pygmy group. The mean weight of the 3/4 pygmy group approximated the mean weight of the 1/2 pygmy group more closely than that of the pygmy group. The same relationships among groups that were observed for the weights were also observed for the 12 and 24 week measurements, and the 15 month weights and measurements. As the relationship to the pure pygmy group increased, the goats became proportionally deeper, wider, longer and greater in circumference than would have been expected on the basis of the measurements of the normal goats In the same manner, as the relationship to the pygmy increased, the weights and measurements of the internal organs increased above that expected on the basis of weights and measurements of the normal goats Three blood chemicals, amino acid nitrogen, urea nitrogen, and alkaline phosphatase, were examined at 4, 6, 8, 10, 12, 16, 20, and 24 weeks of age. Amino acid nitrogen did not change significantly with increasing age or weight. However, the level generally decreased in the six groups during the preweaning period, and increased during the postweaning period. Urea nitrogen levels in creased significantly in both sexes as age and weight increased The levels of urea nitrogen increased during both the preweaning and postweaning periods. Alkaline phosphatase activity decreased significantly with increasing age, but showed no significant association with changes in weight. Three levels of alkaline phosphatase activity were observed; high, medium, and low. All three levels were found in the normal, 1/4 pygmy, and 1/2 pygmy groups The medium and low level were found in the 3/4 pygmy, and 7/8 pygmy groups. Only the low level was found in the pygmy group0 The low point in alkaline phosphatase activity was found during the period following weaning. A genetic model was proposed for the inheritance of the pygmy characteristic. The proposed model consists of two genes, a major gene and a modifier gene. The effect of the major gene is to produce large changes in the size of the animals, while the effect of the modifier gene is to regulate the effectiveness of the major gene. Both appear to show incomplete dominance when in the heterozygous condition. The genotype of the normal goats was proposed as being NNaa, that of the pygmy as being nnAA, and that of the 1/2 pygmy as being NnAa where N and n are alleles of the major gene, and A and a are alleles of the modifier gene, Using the weight of the normal goat as a standard, the theoretical values of each possible genotype in each group was calculated. Theoretical means were calculated for each of the groups and found not to be significantly different from the means actually obtained.
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