Document Type : Original Article
Authors
1
Animal Production .Dept , Fac. Agric., Mansoura University, Egypt
2
Animal Production. Research Institute, Agric Res Center, Ministry of Agric. Egypt
Abstract
Estimates of covariance component and some genetic parameters were evaluated by using multi traits animal models, for Total milk yield (TMY),Lactation length (LL) ) ,Dry period (DP) and Days open(DO). In this study the normal lactation records(4758) of Friesian cattle collected during the period from (2002 to 2010) from the farm of Investment Company Dairy Products Kilo 80 Cairo Alexandria Desert Road ( Dina farm) were used .In the three mixed model used the analysis included the non genetic effects of month and year of calving and the random effects of additive direct genetics, maternal effect and residual. The overall means for TMY, LL,DP and DO were 10224 kg, 413d, 108d and 221d,respectively.However,the coefficient of variation (C.V%) were ranged from (32%) TMY to (82%) DP during the first lactation. The large coefficient of variation, would be important indicative leaders in this study. The results showed the estimates of covariance components and heritability for different studied traits.The obtained results showed that, Additive genetic variances were higher; in model(2)for total milk yield, in model(3) for lactation length, in model(1) for dry period and in model(3)for days open. In the other side maternal genetic variances was higher in model(3) for the studied traits. However, residual and phenotypic variances were higher mostly in model (2)and model(3)than their corresponding values in model(1).The estimates of heritabilities using the three models for TMY,LL, DP and DO were ranged from (0.48±0.04) to (0.59±0.03), (0.01±0.00) to (0.06±0.3) , (0.03±0.07) to (0.08±0.03) and(0.01±0.0) to (0.12±0.03), respectively. However, the obtained estimates of maternal heritabilities were very low in the three models for TMY, LL, DP and DO. It ranged from (0.00 ±0.00) to (0.19±0.02),(0.00 ±0.00)to (0.01±0.01),( 0.01±0.01) to ( 0.07 ±0.02) and(0.00 ±0.00)to (0.01±0.01),respectively.The results recorded different estimates of phenotypic and genetic values between examined traits ,The experimental results lead to concluded that, the influence of the maternal genetic effect for traits were the lowest, thereby no relative efficiency of improvement .vice-versa, direct heritability for TMY and DO would be efficiency.
Keywords
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