Thesis - University Access Only
Master of Science (MS)
Department / School
To evaluate the potential of the melatonin receptor MTNRlA gene as a candidate gene for association to reproductive efficiency of the ewe in fall lambing, the following study was undertaken. Three breeds of ewe were used to evaluate the MTNRIA gene. They were Hampshire, Columbia and a Finnsheep-Dorset-Targhee composite ewe. The traits that were measured for this research were lambing success and number born. Two restriction enzymes were used to digest the amplified MTNRlA gene using methods designed by Messer et al. (1997). The genotypes derived from the digestion of the MNTRIA gene by Mn! I were the same as work by Pelletier et al. (2000), yielding two homozygote genotypes and a heterozygote genotype with the same restriction fragment length polymorphisms. A new fragment length derived from Rsa I is presented in this study that varies from previous work by Messer et al. (1997). A 273 to 276-bp fragment was elucidated replacing the earlier presented 290-bp fragment. This study yielded the 295-bp fragment found in earlier work as well. The study analyzed the homozygote genotypes and the heterozygote genotype for Rsa I as well as the genotypes generated by digestion of the MTNRlA gene by Mnl I. Statistical analysis of the traits of number born and fall lambing rate showed that in the FDT composite ewe, neither genotype or the combination of the genotypes was significant in prediction of either trait. For the Hampshire ewe, again, neither genotype or combinations of the genotypes was significant in predicting either reproductive trait analyzed. Within the Columbia breed, however, the genotypes derived from Mnl I were significantly different (P = 0.008). For each copy of the C allele derived from Mnl I, the odds of the Columbia ewe increasing fall lambing rate would be 2.50 times higher. In an effort to compare the results of Pelletier et al. (2000), the Hampshire and Columbia ewes were sorted to those ewes with fall lambing rates ::::25% or >75% and then analyzed with the same model with the addition of breed as a variable. The results of this analysis showed that the genotypes derived from Mnl I were significant (P = 0.02) in predicting fall lambing rate. Per copy of the C allele, the odds of a ewe increasing her lambing rate were multiplied by 3.32 times. In all of the analyses performed, the genotypes derived from the restriction enzyme Rsa I were not significant in predicting the fall lambing success of the ewes or the number born in the fall.
Library of Congress Subject Headings
Ewes -- Breeding Ewes -- Reproduction Melatonin Genetic polymorphisms
Number of Pages
South Dakota State University
Wright, Casey D., "Polymorphisms at the Melatonin (MTNR1A) Gene and Their Association to Reproductive Performance in Fall Lambing Ewes" (2000). Electronic Theses and Dissertations. 780.