No abstract

AbractAn experinienl w;is t;()iK!uclt;iJ Ui cnmp;trc tiio cl'tects of the grazing by ewes and weaned lanihs on aflermath and previously continuoii.sly gnized perennial rycgras.-;-dominanl swiirds. al two sward heiglils (4 and 8 cm) in lhe auitimn. on cliangcs m Mruclurc and growih of the swards. The cxperinienl had a taclorial design, was replicated iwice and was conducled from mid-August to early November with measuremeni.s being made on three occa.si{ins in the autumn. Aftermath .swards hatJ lower tiller population densities and lower herbage mas.ses than those that had been previously conlinuously grazed, the differences being greatest in August. On an area basis net growth rates of herhage on aftermaths were lower than lho.se on previously continuou.sly grazed swurds in August and September but not in October. Growth rates of herbage were higher on the taller .sward, but the senescence rate.s were similar at the two sw:ird heights. It was concluded thnt autumn swarcis may be managed at taller sward heights than summer swards without increasing senescence of the sward and a consequent reduction in efficiency of utilization. The effects of previous sward management on tissue turnover in the autumn were not long lasting.tPresent Address: Insiitulo de Investigaciones Agropecuarias, Casilla 296. Coyhaique. XI Region. Chile.

The effects on herbage intake and ingestive behaviour by ewes and weaned lambs of grazing aftermath and previously continuously grazed perennial ryegrass-dominant swards at two different sward heights (4 and 8 cm) in the autumn were studied. The experiment had a factorial design, was replicated twice and was conducted from mid-August to early November. There were six ewes and six weaned lambs per treatment plot and measurements were made in three periods. The effects of previous treatment of swards on herbage intake by ewes and weaned lambs were greatest in August, with herbage intakes being significantly lower on the aftermath swards. Differences disappeared by October. Tbe lowest herbage intakes were obtained on the aftermath sward at the lowest sward height, with ewes being more affected under those conditions than lambs. Grazing time and biting rate increased with a reduction in sward height and were higher on aftermath swards. However, these increases did not compensate for reductions in estimated bite size on the aftermaih swards. It was concluded that the effects of the sward management treatments in the summer on tissue turnover of the sward and herbage intake in the autumn were considerable in the early part of the auttimn but had largely disappeared by the end of the autumn period.

The low level of legumes in New Zealand hill pastoral systems is a recognized problem that is likely to affect sustainability. The relative importance of the factors that cause low legume abundance has not been sufficiently tested, especially on dry hill country. This paper reports the effects of grass suppression in two contrasting years in a summer-dry hill country site on the east coast of the North Island. Suppressing grass with haloxyfop herbicide (Gallant) in late autumn increased legume abundance by > 25% in both years, but the response patterns were strongly influenced by soil moisture status. Moist late spring and summer conditions produced 34% more legume growth in both ± herbicide treatments. Residual effects of grass suppression favoured white clover over subterranean clover growth under moist seasonal conditions. The control of grass growth in these hill swards improved legume abundance, but the overriding factor affecting legume content in the pasture was the level of soil moisture. Key words: grass suppression, haloxyfop herbicide, hill country, legume abundance, soil moisture, subterranean clover, summer-dry, white clover

Western Patagonia lamb production systems are based on extensive rangeland. The harsh climate limits the adoption of more intensive systems. Therefore, producers must focus on developing differentiated products. The aim of this study was to evaluate growth patterns, carcasses and nutritive value of meat from 45 lambs. Lambs were divided into three groups: 15 lambs were slaughtered at weaning (W), with the remaining 30 weaned lambs being allocated to grazing either alfalfa (AG) or permanent pasture (PPG). AG lambs were significantly heavier and had higher condition scores than PPG lambs. Further, AG lambs showed higher carcass weight and larger tissue depth and commercial cuts. Moreover, W lambs had lower shear force and more tender meat than either AG or PPG lambs. The three systems showed a low shear force and acceptable sensory traits. Low levels of cholesterol, with low levels of saturated fat, classified these cuts of meat as extra lean. W lambs had higher omega-3 fatty acid content than AG or PPG lambs. Overall, results showed that meat from the three lamb production systems showed health claimable levels of omega-3 fatty acids and were low in fat and thereby, can be classified as lean meat.