No abstract

The aim of this paper was to estimate genetic parameters for body weight and five body measurements for an experimental population of Iranian Makooei sheep maintained at the Makooei Sheep Breeding Station at Makoo, Iran. To do this, yearling live weight (YW), and five body measurements, i.e., body length (BL), heart girth (HG), height at withers (HW), height at back (HB) and scrotal circumference (SC), were analyzed in a multi-trait animal model using the DXMUX program of DFREML software package. Heritability estimates were 0.22±0.08, 0.11±0.06, 0.21±0.07, 0.17±0.06, 0.17±0.06 and 0.32±0.10 for YW, BL, HG, HW, HB and SC, respectively. These estimates indicate that selection in Makooei sheep would generate moderate genetic progress in body weight and body measurements. Scrotal circumference, as an indicator of reproductive potential, exhibited the highest heritability. This trait, therefore, could successfully be used to increase productivity of males and, indirectly, female fertility. Genetic correlations between traits studied were all positive and ranged from 0.15 (YW/HB) to 0.99 (HW/HB). Phenotypic correlations were also positive and ranged from moderate (0.32, HW/SC) to high (0.94, HW/HB). Positive genetic and phenotypic correlations indicate that improvement in body measurements both at the genetic and phenotypic levels is expected through selection on body weight and vice versa.

The aim this paper is to investigate whether characteristics of the first lactation (FL) curve of Iranian Holstein cows is associated with survival. Cows with least 10 Test days of milk production in their FL were used. The persistency of lactation (PL) and survival were estimated using a Random Regression Model by REML with the ECHIDDNA software. We also used the Wood model to parameterize each individual lactation curve and then analyze various curve characteristics using an animal model. The EBV of the characteristics of the lactation curve of the cows from day 40-305 predicted. The EBV of the production range (PR) and the slope of line in increasing phase (m_(40,Peak)) of production curve of sires with higher survival EBV were lower than other sires (p˂0.05). The estimates of LP were independent of survival estimate. Therefore, the PR from 40th day after calving can be considered as a definition of PL. Because the lower the PR, the flatter is the milk production curve. Genetic evaluation of young bulls for survival needs the data of death or culling of their daughters. Therefore, the bulls can genetically be evaluated for survival according to the LP and m_(40,Peak) of FL information of their daughters.