Abstract
The effzcts of season of calving an economic traits of crossbred
dairy cattle produced under va.i>us projects sponsored by the Pakistan
Agricultural Research Counci! were studied during the years 1974 to
1980. These animals were stationed at the Livestock Production
Research Institute, Bahadurnagar (LPR), Livestock Experiment
Station, Karachi¢LES) and the University of Agriculture, Faisalabad
(UAF) Luacal Sahiwal (SWL) cattle were crossed with two Eurcop-
ean breeds, Holstein Friesian (HF) and Jersey (J) at LPRI and
UAF. At LES, the native Red Sindhi (RS) was crossed with the
HE and ] breeds. At LES and UAF, the crossbred progeny,
thus produced comprised of halfbreds only, while at LPRI 3/4 HF
and 3/4 J groups were also available for this study. A highly signi-
ficant influence of season of calving on milk production was obser-
ved among the LPRI groups, whereas this effect was non-significant
at LES and UAF. The sire-breed by season interaction was non-
significant at all stations for milk production. However, for days
dry the season and sire-breed by season were significant in LPRI
and highly significant in UAF groups. These effects were significant
for days open at LPRI and higbly significant for calving interval
at UAF and LPRI. Generally, the milk prod uction was the highestin
the spring calvers and lowest for the summer calvers, Also, the
animals calving in winter produced more than those calved either
io summer or fall season.
