The effect of internal parasites on the performance of lambs grazing different forage species was examined in two experiments.

Mortality data on 5163 Romney X Suffolk lambs were collected at Winchmore Irrigation Research Station from 1976 to 1.981. M?rtality from birth to tailing (25 days) for single, twm, and triplet births was 14.1, 14.7, and 33.0% with mean birthweights of 5.2, 4.1, and 3.3 kg respectively. Ninety-four percent of all deaths occurred within 72 h ofbirth. Dystocia accounted for 50.4% of all single deaths and starvation/exposure for 45.0% ofall multiple deaths. The proportion ofewes assisted at lambing increased with birthweight above 4.5 kg to reach almost 19 and 8% for single and twin births respectively. If lambs that were assisted at birth, but survived to weaning, are regarded as potential deaths, the overall potential mortality of single and twin lambs was 27.9 and 20.2% respectively. Ewe liveweight gain during the last 6 weeks of pregnancy was associated with increased birthweights of single and twin lambs (P< 0.05). A liveweight change of approxi.mately 10 kg in ewes was required to alter birthweight by 0.5 kg in both single and twin lambs. Single l~mb mortality was not significantly affected by liveweight gain or ewe livewei~ht at lamb~ng on.either a between-mob or a within-mob basis. ThIS suggests that with single bearing ewes it may be more economical to save feed for lactation when feed requirements of ewes are high, rather tha~to offer it in late pregnancy. However, when multiple bearing ewes were offered additional feed in la~e pregnancy to increase liveweight, lamb mortality was reduced, suggesting merit in improved pre-lamb feeding for these ewes.

Coopworth and Merino lambs were slaughtered at 8 months after being grazed together on ryegrass/clover pasture from weaning. The flavour and odour intensities of the cooked lean (longissimus lumborum muscle) and odour intensity of subcutaneous fat were assessed by an analytical panel. Sheepmeat flavour in the lean was stronger (P < 0.01) in Coopworth and foreign flavour was stronger in Merino (P < 0.001). However, the mean pH of the meats also differed significantly (P < 0.001) (Coopworth, 5.77; Merino, 6.16), thereby confounding the effects of pH and breed. Panellists' comments pointed to a breed effect in subcutaneous fat odour, but means for sheepmeat and foreign odours in the fat were statistically identical. Meat toughness, assessed by the same panel, peaked around pH 6.0, irrespective of breed. In a parallel study of the Merino lambs and five Merino cross breeds, an in-house panel assessed acceptability rather than intensity of meat attributes. All crosses and the pure Merino produced meat that was acceptable (5 or more on a 1-9 hedonic scale) for aroma, flavour, tenderness, texture, and juiciness. There was a breed effect for tenderness (P < 0.05) however, with Merino being the most tender and the Texel x Merino being the least. When breed was disregarded, texture and tenderness were the best predictors of overall acceptability (r = 0.86, 0.80) and pH, which ranged between 5.41 and 7.12, was

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