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Notes: To investigate the effect of sward height on liveweight change in goats grazing grass/white clover swards, an experiment was conducted from mid-August to mid-November with groups of non-lactating female cashmere goats that continuously grazed perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) swards. Three replicated different sward height treatments — 10–8 cm (high), 7–5 cm (medium) and 5–3 cm (low) — were used to examine the effects on the competitive ability of grass and clover components within the sward canopy and their effect on liveweight. The pasture after grazing by goats had relatively higher ryegrass leaf (+0·26, high; +0·32, medium; and +0·18, low) and lower dead ryegrass proportions (−0·28, high; −0·23, medium; and −0·18, low) than at the beginning of the experiment, whereas the white clover fraction in the sward remained constant (+0·04, high; −0·02, medium; and +0·03, low). Higher proportions of the white clover leaf lamina and petiole were found near the top of the sward canopy and were negatively correlated with the rate of liveweight gain by goats (P 〈 0·05). Goats gained 50·2 g Live weight (LW) d−1 on the tallest treatment (high) but lost 0·01 and 42·3 g LW d−1 on the medium and low sward height treatments respectively (s.e.d. 13·21, P 〈 0·001). Liveweight changes that occurred between sampling periods were also correlated (R2= 0·858, P 〈 0·001) with changes in the mean sward height and proportion of white clover lamina-petiole at the sward surface in relation to the proportion found within the whole sward. These results suggest that goat liveweight gains would be increased if another species was introduced to reduce the white clover proportion in the surface horizon.

Notes: Several experiments were performed in spring summer over the period 1982–85 to study the relationships between digestibility of energy (DE), gross energy intake (GEI), acid detergent fibre (ADF) and dry matter (DM) content in pasture.Wether sheep in metabolism pens and fed ad libitum with daily-cut fresh pasture were used. Two plots with different botanical composition were used to provide herbage; one dominated by Lolium perenne and the other by Holcus lanatus. A high correlation (r= -0·91) was observed between DE and ADF. The prediction used a second-order degree polynomial.Gross energy intake and digestibility of energy were scarcely correlated (r= 0·50) when all cases as a whole were considered. Higher correlations between GEI and DE (r= 0·69) were obtained when only data from pastures where Holcus lanatus prevailed were considered, and still higher (r= 0·91) in those pastures dominated by sown species with DE values lower than 70%.Herbage DM content had a large effect on GEI(r= 0·83) in the pastures dominated by perennial ryegrass with DE higher than 70%, the correlation between DE and GEI being low and negative (r=-0·36). It is possible, therefore, to predict apparent digestibility of pasture energy from ADF. However, DE is closely related to GEI only in those pastures in which DE is lower than 70%, DM content being an important factor limiting the intake of those fresh pastures dominated by Perennial ryegrass when DE is above 70%.

Notes: The effect of the proportion of Calluna vulgaris cover on diet composition, intake and performance of sheep grazing hill vegetation communities in northern Spain is examined. A total of 591 non-lactating Gallega ewes grazed for five consecutive grazing seasons (June to September) on replicated plots of hill pastures (1700 m.a.s.l.) composed principally of Festuca, Agrostis, Nardus and Calluna spp. but with different proportions of Calluna vulgaris cover, either 0·3 (C0·3) or 0·7 (C0·7) of the total area. In 1 year, twenty-eight ewes suckling single lambs also grazed the plots. The mean stocking density over the 5 years was 8·7 ewes ha–1. On treatment C0·3, daily liveweight gains (33 g d–1) of non-lactating ewes were significantly (P 〈 0·001) greater than on treatment C0·7 (12 g d–1). Likewise in lactating ewes the difference in mean daily liveweight change was 40 g d–1 (–5 vs. –45 g d–1 for C0·3 and C0·7 treatments respectively; P 〈 0·001). Liveweight gains of lambs were only 80–100 g d–1 from June to August and lambs only maintained live weight during August and September. The effect of lactational status on liveweight changes was not significant. Liveweight gains of non-lactating ewes increased significantly (P 〈 0·001) from the first to the last year of the experiment on both treatments.The composition of the diet was significantly affected by treatment (P 〈 0·001), with a higher proportion of grass species on the C0·3 treatment and a higher digestibility of the diet in the first half of the grazing season (P 〈 0·001). The proportion of C. vulgaris in the diet was significantly (P 〈 0·001) higher on the C0·7 treatment and increased significantly (P 〈 0·001) from July to September on both treatments. There were no significant differences in the composition of the diet selected by lactating and non-lactating ewes.The results demonstrate that on hill vegetation communities, in which the grass components (Festuca rubra, Agrostis capillaris, and Nardus stricta) cover at least 0·3 of the area and on which the preferred grass component (Festuca and Agrostis spp.) is maintained at a sward height of at least 2·5 cm, non-lactating ewes can increase their live weight and body condition, but this increase is influenced by the proportion and quantity of species of grass in the diet, which is affected in turn by the species of grass available and their nutritive quality. However, ewes suckling lambs were not able to maintain their live weight and body condition except when Calluna cover was 0·3 and grass height was more than 3·5 cm.It is concluded that these indigenous vegetation communities can be used in sheep production systems to complement the use of improved pastures at other times of year. In particular, they can be utilized during the non-lactating period (summer) to increase body condition before the beginning of the mating period in autumn.

Notes: Abstract Effects of breed and sward surface height on ewe liveweight and body condition changes and on lamb liveweight gains during grazing in the spring and autumn were studied. The output per hectare in each season was also calculated.A total of 112 Gallega ewes (35·6 kg live weight) and 204 Latxa ewes (47·5 kg live weight) with their lambs were used during the spring (March–June) to study the effect of five target sward heights (3·0, 4·5, 5·5, 6·5 and 8·0 cm) and the interaction with breed. In autumn (October–December) 155 Gallega and 126 Latxa ewes were used to study the effect of three target sward heights (4·0, 5·5 and 7·0 cm) and the interaction with breed. Each study was replicated twice.A quadratic relationship was found between sward height and ewe liveweight and body condition changes and lamb liveweight gain during the spring grazing season, with the maximum individual performance being achieved at around a sward height of 6·0 cm. There were significant breed × sward height treatment interactions for ewe liveweight and body condition changes, and lamb liveweight gains. Higher liveweight gains were achieved by Latxa ewes and lambs in swards taller than 6·5 cm but they also sustained higher liveweight losses in swards shorter than 4·5 cm. Nevertheless, a higher output (liveweight gains of ewes + lambs) per hectare for a given weaning date or age was achieved by the Gallega ewes. In autumn, the relationship between liveweight change and sward height was linear, with a breed–sward height interaction similar to that observed in the spring.Sward surface heights of 4·0–4·5 cm and 4·5–5·0 cm were required to maintain live weight and body condition in spring and autumn respectively. Lamb and ewe liveweight gains per hectare decreased considerably in swards taller than 6·5 cm.