Beef production from kikuyu and Italian ryegrass.

Abstract

Four grazing trials to characterise cultivated pastures, in terms of

beef production, were conducted in Bioclimate 3 of Natal.

Dual purpose and British beef type cows were run on kikuyu at stocking

rates from 2,81 to 7,30 cows plus calves per ha. During the eight seasons

of the trial the seasonal rainfall varied from 580 to 933 mm. There was a

positive linear relationship between rainfall and pasture yield with maximum

yield of kikuyu being recorded during February - March. Stocking rate

affected pasture yields only during favourable rainfall seasons. Crude

protein (CP) and crude fibre (CF) of kikuyu fluctuated markedly within and

between seasons. However, CP increased and CF decreased as stocking rate

increased. There were significant relationships between stocking rate and

(a) calf performance, (b) calf livemass gain, (c) period required to attain

maximum mass, (d) period on pasture for the cows, and (e) cow mass change:

Weaners were run on irrigated Italian ryegrass at 5, 7 and 9 weaners per

ha for four seasons. Stocking rate had little effect on the growth pattern

of the pasture but affected dry matter yields. Reducing the stocking rate

resulted in increased pasture yields and CF content but reduced CP levels of

material on offer. Steers exhibited higher gains than heifers but lower

carcass grades and stocking rates for maximum gain per ha (SRmax). Livemass

gains of 1315 and 1224 kg per ha can be expected at SRmax of 6,85 and 9,54

for steers and heifers respectively.

Yearling heifers run at four stocking rates on kikuyu for one season

showed a negative linear relationship between stocking rate and gain and a

positive linear relationship between pasture height and gain. A SRmax of

8,85 allows for a livemass gain of 1 040 kg per ha. The effect of feeding concentrates on foggaged kikuyu was evaluated.

Foggaged kikuyu can be used as a source of roughage for fattening steers.

However, as the steers became adapted to the concentrate the intake of

kikuyu declined from 39 to 19% of their daily intake.

Regressions derived from the characterisation trials allow for

developing beef systems for different situations.