Published online by Cambridge University Press: 02 September 2010
Ewes of the Segureña breed were allocated to groups and were group-fed different diets composed of concentrates and roughage (lucerne hay in experiment 1 and barley straw in experiment 2), in late pregnancy and lactation. The concentrates were formulated with sunflower cake and barley, either alone (control group) or partly replaced with olive cake (OLC) and olive molasses (OLM) in a 5:1 ratio. The OLC was either untreated or was treated with NaOH or ammonia. Concentrates were given to provide proportionately 0·4 and 0·7 of calculated metabolizable energy (ME) requirements in experiments 1 and 2 respectively. In experiment 2 a further group grazed pasture and was given barley at a reduced rate.
In experiment 1, the mean ME intake during late pregnancy (5+1 weeks pre-lambing) for all treatment groups was about 796 kj/kg M0·75 per day and largely exceeded their average energy requirements, whereas it was close to requirements (601 kj/kg M0·75 per day) in experiment 2. During lactation, ME intake was adjusted to the theoretical needs for ewes suckling a single lamb (835 to 870 kj/kg M0·75 per day) and was slightly deficient (990 to 1020 kj/kg M0·75 per day) for ewes with twins, irrespective of both treatment (except the group at pasture) and experiment.
Minor differences in animal performance, attributed to the type of concentrate offered, were found. In pregnancy, alkali treatment of OLC significantly improved live-weight gains (P < 0·01). Live-weight gains of ewes in experiment 2 were lower than those in experiment 1 in accordance with their lower ME intake, the lowest gains being found in the group at pasture (P < 0·05). Weight losses in lactating ewes in experiment 1 were 17 to 100 and 9 to 165 g per ewe per day for ewes suckling single and twin lambs respectively. In experiment 2 ewes with twins gained weight, while those with single lambs showed little weight change, although differences between experiments were too small to attain statistical significance. No differences in barley straw intake by pregnant ewes were found between treatment groups. However, the intake of barley straw by lactating ewes in the groups offered concentrates containing OLC and OLM was significantly higher than that by controls (P < 0·05).
Birth weight of lambs tended to be higher in experiment 2 when ewes consumed less ME during pregnancy, although variations were not statistically significant. The most important cause of growth rate variation was the number of lambs born to a ewe (P < 0·001). The growth rate of lambs in the outdoor group was significantly lower than that of lambs in the indoor groups (P < 0·05).
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