Summer supplementation of beef cattle on veld and kikuyu pastures.
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Date
2004
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Abstract
In KwaZulu-Natal the production of beef in summer from veld is a common
enterprise. Many techniques are available to optimise the productivity of this enterprise,
from improving the quality of the grazing resource (planted pastures) to improving the diet of
animals using nutritional supplements. To gain an insight into the production potential and
financial returns possible from such improvements a trial was established at the Ukulinga
Research Farm during two consecutive summer growing seasons (1997-1998 and 1998-1999).
The aim was to determine the optimum beef production system for the area from both
veld and kikuyu pastures. To evaluate the benefits of supplying supplementary nutrition, four
alternate feed supplements, namely: 1) a Standard commercially available molasses-based
protein/mineral/energy supplement; 2) a Brewers grain based protein/mineral/energy
supplement, and two supplements consisting of the Brewers grain ration with either; 3)
Avoparcin (an additive that improves dietary energy) or 4) Bentonite (an additive that
increases the bypass of protein) were compared. As stocking rate has been shown to
influence the quality of the diet consumed, the kikuyu pasture was grazed at both the
recommended (1.92 LSD ha¯¹) and half the recommended stocking rate for the region. In
addition, a commercial hormonal implant was applied to half of the cattle in each treatment.
Grazing was monitored using the falling plate disc meter to measure pasture bulk
density and laboratory analyses of herbage grab samples for digestibility and crude protein
percentage. Cattle were weighed on a weekly basis and their condition was scored prior to
slaughter. All enterprise costs and returns were recorded to facilitate financial analyses of the
five treatments.
Low rainfall and high midsummer temperatures had a detrimental effect on the
productivity of the grazing and hence it was difficult to optimise production in either season.
In the first season, a midsummer drought decreased the quality and quantity of both veld and
kikuyu, limiting mass gain during the latter part of the season. A delay in the onset of rain at
the start of the second season limited the available grazing season to 121 days as opposed to
154 days, though fodder production during the season was not limited.
Trends in herbage production (quality and quantity) from veld showed moderate
quality (Crude protein 7.02%; digestibility 50.2%) with an average available herbage of 1670
kg DM ha¯¹. As anticipated, kikuyu had higher quality (Crude protein 10.84%; digestibility
53.5%) and available herbage (2730 kg DM ha¯¹). These results were similar to regional
benchmarks. The variable rainfall highlighted both the drought tolerance of veld and the minimum water requirements of kikuyu pastures. Lighter stocking rates tended to reduce the
negative impact of moisture stress on Kikuyu pastures.
The best method of producing beef (averaged over two seasons) was from heavily
stocked Kikuyu pastures using the Standard supplement (1107.63 kg livemass ha¯¹). Cattle
grazing veld and utilising the Avoparcin supplement produced beef at a rate of 95.96 kg ha¯¹.
In comparison, the unsupplemented cattle grazing Kikuyu produced 834.87 kg ha¯¹, whilst veld grazing produced 64.43 kg ha¯¹. Hormonal implants significantly (P≤0.05) improved beef production from all sources of grazing. A lack of rain limited grazing time, causing all the cattle to be marketed whilst too lean - this negatively affected live mass gain and, hence,
net financial. Although improved biological production is desirable, it is important to ensure that these gains are financially sustainable. Within the trial environment, implanted cattle fed the Standard supplement and grazing Kikuyu pastures at a high stocking rate provided the highest average gross margin of R 859.59 ha¯¹. Changing to this production system from unsupplemented veld improved expected profit by R 632.58 ha¯¹ (averaged over both seasons). Further financial analyses indicated that beef purchase price had the greatest influence on the added profit from switching from the control treatment. From a scientific standpoint these data are conclusive but it is important to remember that consumer pressure and concerns can often limit the introduction of production
improvements. Such is the case with both hormonal implants and antibiotic feed additives (Avoparcin) although considering the impact of such limitations is speculative and beyond the scope of this trial.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.
Keywords
Beef cattle--Feeding and feeds., Beef cattle--Economic aspects--KwaZulu-Natal., Beef cattle--Management., Grazing--KwaZulu-Natal., Kikuyu grass--KwaZulu-Natal., Theses--Grassland science.