Search

The purpose of the present study was to asses specific gene markers associated with the sheep milk production in Teleorman Black Head ewes. For the proper selection of the best candidates for milk production, the genetic markers such as CSN3, BLG and PRL were selected. To detect CSN3, PRL and BLG polymorphisms, genomic DNA was isolated from blood samples collected from 50 ewes. ASA-PCR and PCR-RFLP methods were used for genotyping of animals; the genotypes frequencies and Hardy-Weinberg equilibrium were estimated using R software. In our samples, for CSN3 gene were identified two genotypes (CC and CT), the most frequent being CT genotype (94%). For PRL gene, were identified three genotypes (AA, AB and BB), AA and BB genotypes being the most frequent (36% and 40% respectively). Also, three genotypes were identified for BLG gene (AA, AB and BB), with an increased frequency of AB genotype (44%). These preliminary data will be correlated in the next experiments with phenotypic data, generating important tools for genetic selection of the Teleorman Black Head sheep population. [ABSTRACT FROM AUTHOR]

The aim of this paper was to study the breeding values and genetic parameters estimation methodology applied on Teleorman Black Head Sheep breed genetic improvement programs. Throughout study were estimated heritability using test-day milk yield and the genetic correlation between test-days milk yield for Teleorman Black Head Sheep from Dobroteşti Teleorman area. The genetic parameters of daily milk yield during one lactation of Teleorman Black Head ewes were estimated with random regression test-day animal model. Data consisted of 1032 test-day records from 344 ewes. The breeding values for test day milk yield for the best ewes were ranged between 14.57 g milk and 28.48 g milk. The heritability estimates for three test-day milk yield of ewes were: 0.105 for first test day record, 0.270 for second test day record and 0.250 for third test day record. Genetic correlations between individual test days milk yield records were positive and of medium magnitude. Once again during the present research we observed that the test-day is the most appropriate methodology for milk production genetic evaluation in sheep, who offer the best improvement of the performances by genetic progress. That why random regression model was used the most in different countries, giving a better accuracy for breeding value, and ranking better the best ewes. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the genetic parameters represented by heritability for test-day milk yield and the genetic correlation between test-days milk yield and the breeding value for Teleorman Black Head sheep. The genetic parameters of daily milk yield during the first three lactations of Teleorman Black Head ewes were estimated with the random regression test-day animal model. Data consisted of 631 test-day records of 81 ewes at first lactation, 351 test-day records of 58 ewes at second lactation and 229 test-day records of 33 ewes at third lactation from experimental farm of INCDBNA Balotesti. Lactations were analysed separately. The heritability estimates for test-day milk yield of ewes at first lactation ranged from 0.015 at 200 day in milk to 0.19 at 10 day in milk. For the ewes at second lactation the heritability estimates ranged from 0.016 at 180th in milk to 0.246 at 10 day in milk. For the ewes at third lactation the heritability estimates for test day milk yield ranged from 0.018 at 180th in milk to 0.249 at 10th day in milk. Genetic correlations between individual test days milk yield were high and positive. [ABSTRACT FROM AUTHOR]

Genetic parameters of Montbeliarde cows were estimated for test-day milk yield with a random regression spline model. The spline model has been considered as a good alternative to Legendre polynomials to direct interpretation of parameters. With this model the lactation curve is divided into sections by knots. The milk yield between any two knots is assumed to be changing linearly. The random regression was fitted with linear splines with five knots: 7, 54, 111, 246, 302. The herd-test-day is the fixed effect of the model. The heritability estimates for test-day milk yield ranged from 0.346 at 65th day in milk, to 0.422 at 35th day in milk. Genetic correlations between individual test days were positive and tended to decrease with an increase in days between when the yields were measured. Random regression models using linear splines were proved to be useful for genetic evaluations of cows. [ABSTRACT FROM AUTHOR]