Breeding values for some milk production and reproductive traits in a commercial Holstein cattle herd raised in Egypt

Abstract EN

Data of some milk production traits (305-day milk yield (305d-MY, kg), ; length of lactation period (LP, day) ; duration of dry period (DP)) and reproductive ones (calving interval (CI) and age at first calving (AFC) using records of 5662 normal lactations produced by 1029 Holstein cattle raised in El-Salhia farm, Ismaillia Governorate, Egypt were used in this study.

Breeding values of cows, sires and dams were obtained through analyzing the data by Multiple trait Derivative free Restricted Maximum Likelihood ( MTDFREML) using the multiple trait Animal model Analysis for all traits of the study.

The breeding values were estimated by using data of all the available lactations.

The main results of this study could be briefed as follows:The ranges of cow breeding values, were 2504.11kg for 305d-MY, kg, 14.86days for (LP), 16.56 days for duration of (DP) , 92.48 days for (CI) and 5.80 months for(AFC).

The corresponding ranges for top 25% of cow breeding values were 1682.60kg, 9.10days, 5.01 days, 54.88 days and 4.47months.

The accuracy of minimum and maximum estimates of cow breeding values, for all traits of the study (ranged from 0.35 to 0.87).The percentage of cows that recorded positive cow breeding values was 49.17, 52.19, 48.00, 60.64 and 38.39% for 305-day milk yield, length of lactation period, duration of DP, CI and AFC, respectively.

The ranges of sire breeding values, were 1502.85kg for 305d-MY, kg, 12.20 LP, 13.79 for duration of DP, 62.20 days for CI and 3.44 month for AFC.

The corresponding ranges for top 20% of sire breeding values were 1019.51kg, 7.82days, 8.99days 36.91 days and 2.27 months.

The accuracy of minimum and maximum estimates of sire breeding values, for all traits of the study ranged from 0.24 to 0.95.

The percentage of sires that gave positive sire breeding values was 53.23, 51.30, 48.92, 47.50 and 48.92% for 305d-MY, kg, LP, duration of DP, CI and AFC , respectively.

The ranges of dam breeding values, were 1451.00kg for 305d-MY, kg, 6.82 days for LP, 7.70 days for duration of DP, 25.54 days for CI and 2.90 month AFC.

The corresponding ranges for top 25% of dam breeding values were 892831kg, 3.85days, 5.28days 29.10 days and 2.04 months.

The accuracy of minimum and maximum estimates of sire breeding values, for all traits of the study ranged from 0.10 to 0.43.

The percentage of dams that showed positive dam breeding values was 56.66, 50.63, 48.98, 47.80 and 45.77% for 305d-MY, kg, length of LP, duration of DP, CI and AFC, respectively.

The ranges of cow breeding and the magnitudes of the minimum cow breeding values for all traits of the study (when using data of all lactations) were always higher than their corresponding of either sire or dam breeding values.

Therefore, it could be stated that selecting cows for milk production and reproductive traits of the study according to cow breeding values would be more reasonable and efficient than selecting them according to their sires or dams breeding values.