The effect of stocking rate on the performance of beef cows and their progeny in the highland sourveld areas of Natal.
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Date
1988
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Abstract
In three separate. but related studies, the performance of
weaner/replacement heifers, dry pregnant cows, and first calvers and
mature cows and their progeny, at different stocking rates in the
Highland Sourveld, was investigated. The study area was located in
Bioclimatic region 4e in the Province of Natal, Republic of South
Africa.
In the first study, carried out over four seasons, the effect of
winter and summer nutritional levels on the performance of replacement
heifers, bred at two years of age, was investigated. The results of
this study indicated that compensatory growth was a potentially
important factor in reducing feed costs, but the degree of compensation
was highly dependent upon stocking rate and the condition of the veld.
The most economical regime for rearing heifers up to the mating stage
was a low growth rate (0 - 0,25 kg/day) during the first winter (post
weaning) followed by a low stocking rate (0,75 AU/ha) on summer veld.
Treatment did not generally affect the number of heifers attaining
puberty, nor their conception rates. Pregnancy rates as high as 96%
were achieved. Treatment also had no apparent effect on subsequent
calving rates.
In the second series of experiments, the role of condition scoring
as a management tool in the Highland Sourveld was studied. The
condition score of the cow was shown to be an important factor
determining conception rate and time of conception. Only 8% of the cows
mated at a condition score of 1,5, conceived, whereas 80% conception
rates were achieved when the cows were mated at a condition score of
3,0 - 3,5. The cost of improving a cow's condition from 1,5 to 3,0 was
R108, whereas the cost of improving a cow's condition from 2,0 to 3,0
was R54.
In the third study, carried out over nine consecutive seasons, the
effect of stocking rate and lick supplementation on the performance of
iactating cows and first calvers was investigated. Four stocking rates
were applied - 0,83, 1,0, 1,25 and 1,67 cows plus calves per hectare.
The very high stocking rate was terminated after four seasons because
of a significant decline in both cow and calf performance, and the
severe deterioration of the natural pasture. There was no benefit to
either the cows or calves with access to a urea-based lick at the very
high stocking rate, but at the low stocking rate (1,0 cow + calf/ha)
the cows were in such a condition that the grazing season could have
been extended, thereby saving on winter feed costs. First calvers
produced weaners as heavy as those of the mature cows and were in
similar body condition at the end of the grazing season. The excellent
performance of the first calvers was attributed largely to the fact
that they calved 3 - 4 weeks prior to the mature cows.
The grazing behaviour of the first calvers and the mature cows, at
the different stocking rates, was observed in the fourth study which
was carried out over two consecutive seasons. There were no significant
differences in the grazing time between the first calvers and the
mature cows at any of the stocking rates. In all the treatments, the
first calvers appeared to establish the grazing patterns, with the
mature cows adopting a followership role. Alloparental behaviour was
noted in the early part of both grazing seasons.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1988.
Keywords
Beef cattle--KwaZulu-Natal., Beef cattle--Feeding and feeds., Beef cattle--Growth., Cattle--Feeding and feeds., Theses--Animal and poultry science.