Document Type : Research Paper

Authors

1 Graduate Student, Department of Animal Science, University of Zabol, Zabol, Iran

2 Assistant Professor Department of Animal Science, University of Zabol, Zabol, Iran

3 Faculty Member Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, Canada

4 Instructor Animal Breeding Center of Iran, Karaj, Iran

Abstract

Birth Weight (BW) is the first trait recorded fllowing birth. It can influence the performance of the
cow and as well impact the performance of the calf it,s duringits maturity. To investigate the effect of
a calf,s BW on the performance of Holstein dairy cattle in Iran, the records gathered between 1967 and
2010 were obtained from the Iranian Animal Breeding Center. The data were then used to model the
productive and reproductive traits including Calving to First Insemination (CFI), First Service to
Conception (FSTC), Calving Interval (CI), and dystocia. BW of calves within each herd were grouped
into five categories based on standard normal distribution (z≤-0.8416, -0.8416 <z≤-0.2533, -
0.2533<z≤0.2533, 0.2533<z≤0.8416, <z 0.8416) to survey the effects of BW of each calf on the
production and reproduction of dams. The results indicated that a calf,s BW significantly (P<0.001)
affected the production, CFI, CI, and dystocia in the first three calving periods. The trend of BW of a
calf on the productive and reproductive traits found to be respectively positive vs. negative The effect
of BW on the incidence of dystocia was higher for the first calving than for the second and third ones.
A maximum deviation of least square means of dystocia in the first three calving periods was observed
in the fifth weight group. They were recorded as: 0.310, 0.154 and 0.137, accordingly. In conclusion,
BW of a calf may be well related to the efficiency of Holstein herds in Iran and which could be
considered in the breeding and management programs.

Keywords