Pastures In Southern Australia Research Articles

Effect of weaning age and post-weaning nutrition on the growth of calves and the liveweight of their dams

A factorial grazing experiment conducted during 1970,1971 and 1972 at the Pastoral Research Station, Hamilton, Victoria, studied two major management factors in beef production. Post weaning liveweight changes of calves and their dams were measured to compare the effects of either an eight or ten month weaning age and differing nutritional regimes applied from 8 to 12 months post calving. The cows stocked at the higher rate (1.7 cow ha -1) post weaning lost less weight or gained more weight during the test period in three out of four occasions than the cows stocked at the lower rate (1.5 cow ha-1). The results from this experiment confirm the finding of Bailey and Bishop 1972 and show that on perennial pastures in southern Australia, calves weaned at ten months old from autumn calving Hereford cows are likely to be heavier at 12 months old than are calves weaned at eight months onto dry pasture. However, weaning calves at eight months onto hay aftermath would be an effective alternative to ten month weaning. This would also reduce the risk of weight loss by the cow due to later weaning.

Competitive growth of capeweed (Arctotheca calendula) and some annual pasture species

A comparison of the relative growth rates (RGR) of plants of capeweed (Arctotheca calendula), subterranean clover (Trifolium subterraneum) and annual ryegrass (Lolium rigidum) under high soil fertility conditions showed capeweed to have a higher RGR in the early weeks of growth, offsetting the effect of smaller seed size. However, when grown in mixed swards with the clover, under conditions of high NPK and water availability, capeweed did not readily suppress clover growth. If the capeweed and clover began growth together, clover growth was reduced by associated capeweed only after twelve weeks of growth, and then only slightly. If the capeweed was established four weeks before the clover there was a marked reduction of clover growth at the harvest eight weeks after the clover was sown. The results suggest that 'smothering' of clover by capeweed through competition for light is unlikely in grazed pastures in southern Australia.

Effect of age at weaning and post-weaning stocking rate on the growth of autumn born calves

Autumn born calves of Hereford cows, stocked at 1.5 per ha were weaned at four, six, eight, or ten months of age and grazed after weaning at 1.9, 2.6, 3.3, or 4.0 calves per ha. The weight of the calves in the following autumn increased with increasing weaning age (stocking rates pooled); 225 kg, 229 kg, 253 kg, and 271 kg in 1969 and 196 kg, 219 kg, 250 kg, and 253 kg in 1970. Because of a sex X weaning age interaction, the liveweight of 12-month-old heifers was not reduced, by early weaning, as much as was steer liveweight. Increasing the post-weaning stocking rate of the calves reduced growth to 12 months of age but there was no interaction between post-weaning stocking rate and weaning age. The results indicated that under normal seasonal conditions on perennial pastures in southern Australia, autumn born calves will be heavier at weaning and as yearlings if weaned after rather than before eight months of age.

Chemical curing of annual pastures in Southern Australia for beef cattle and sheep

A desiccant herbicide (paraquat) was used to kill an annual pasture during the late spring months when the digestibility of the dry matter (DM) was 75%. The nutritive value of this standing herbage during the summer drought period was compared in field and pen studies with pasture allowed to mature naturally in the Mediterranean environment of South Australia. The herbicide treatment resulted in a significant reduction of standing herbage at the beginning of the summer period (5766 v. 2791 kg DM/ha). The DM digestibility by beef cattle of treated and untreated herbage was similar (52.4 v. 53.0% respectively). There was no difference between the paraquat-treated and the naturally matured pasture in the content or the apparent digestibility of organic matter, water-soluble carbohydrate, cellulose, or lignin; but nitrogen content, digestibility, and retention were significantly higher for paraquat-treated herbage. Rainfall between spraying and the beginning of the summer period was 140 mm. Indirect evidence from a separate study indicates that the fall in digestibility of the herbage after paraquat treatment was influenced by both rainfall and the spraying treatment. The productivity of beef cattle and sheep grazing the treated and untreated pastures during the dry summer confirmed the results of the digestibility studies, there being no difference between treatments in weight change or wool production. After the commencement of the autumn rainfall season the proportion of grass . on the sprayed area was greatly reduced, and the growth of cattle was significantly impaired. Thus the overall effect of the paraquat treatment was to reduce cattle growth.

The summer nutrition of immature sheep: The nitrogen excretion of grazing sheep in relation to supplements of available energy and protein in a Mediterranean environment.

The nitrogen excretion of 24 yearling Merino sheep grazing the summer herbage of annual grass-subterranean clover (Trifolium subterraneum L.) sown pastures was measured over four consecutive periods of 28 days in relation to supplementation with available energy (E) and nitrogen (N). The experiment was of change-over design and included nine combinations of supplement E1, E2, E3 x N1, N2, N3 and an unsupplemented (control) treatment; the respective daily allowance of E was 11 3, 227, and 340 g total digestible nutrients daily, and of N supplied as protein 4,8, and 12 g/day. Unsupplemented sheep grazing mature pasture herbage excreted 23.4 g N/day in urine and faeces. Supplementary energy produced an N-sparing effect whereas added protein was associated with an increased excretion of N. Urinary N accounted for all the changes in N excretion, the faecal N component remaining constant throughout the four periods. Relative changes in herbage intake were estimated: as the level of E (dry matter) increased the estimated herbage intake of sheep was observed to fall linearly, but no significant change in estimated herbage intake was associated with changing N. Significant increases in wool production (P<0.05) were associated with supplementary N. Direct and indirect estimates of the N turnover of the grazing sheep are compared, and a crude N balance sheet is presented. Supporting data are presented which suggest that the N intakes of sheep grazing the mature herbage of sown clover-grass pastures in southern Australia are commonly of the order of 12-18 g N/day.