Moghaddar, Nasir

Eftekhtar, Shahroudi F

Nasiri, Moghaddam H

2001

Pajouhesh-va-Sazandegi, 14(2), p. 26-29

1019-9632

https://hdl.handle.net/1959.11/15103

fa

Ministry of Agriculture

Study of environmental effects and predicting phenotypic and genotypic parameters of annual and cululative records in Holstein dairy cattle

Journal Article

Publication

To study the factors that affect monthly and cummulative milk production, ten years records of a holstein dairy herd were used. Average daily milk production in ail records was 18.35±7.71 in monthly records, year of calving was highly significant except in 10th month (p<0.01). In first month of lactation about ten percent of phenotypic variation was due to year of calving and this amount decreased to one percent at the latest month of lactation. The effect of season of calving in all monthly records except 2nd and 10th month of lactation was highly significant (p<0.01). The effect of calving season from first to 7th month of production increased and after that decreased. The effect of age of cow at calving was significant until 7th month of production (p<0.01), and showed a descending trend from first to the end of a lactation. Linear regression of monthly production from days open was significant only in 9th and 10th month of lactation (p<0.05). In all of the cummulative records the effect of year of calving was significant and the maximum effect was on cummulative records of 90 to 150 days. The effect of season of calving on all of the cummulative records was significant (p<0.05) and its influence increased to 240 days cummulative records and after that decreased. The effect of age of cow at calving was significant in all cummulative records (p<0.0) and its effect decreased during a lactation from start to end. Days open was significant only in 305 days milk production (p<0.05). The heritability of 305 days milk production was calculated by three method (Half sib correlation, MUVQUE and REML estimation of variance component) and was 0.257±0.127, 0.312 and 0.266 respectively. Repeatability of 30S days milk production was 0.325±0.047.