THE RESPONSE OF LACTATING AND DRY EWES TO ENERGY-INTAKE AND PROTEIN-SOURCE IN THE DIET

In this lactation experiment, 40 Rasa Aragonesa ewes rearing two lambs were distributed to four treatments to study two levels of metabolizable energy restriction, 80% (E(1)) and 70% (E(2)) of the requirements, and two protein sources in the concentrate (soybean cake or fish meal) on milk yield and lamb growth. At weaning on Day 67 after lambing the ewes were allocated to four treatments to study the effect of the level of energy restriction in lactation and of the amount of barley grain (fresh matter) offered from weaning until 70 days later (250 and 500 g per ewe per day) on the recovery of body reserves. Ewes which were fed fishmeal produced milk with higher protein content (4.98 vs. 4.69%; P < 0.05) and had greater output of protein in milk than the ewes fed soybean cake (62 vs. 55 g day(-1); P < 0.001). Lambs suckling ewes fed fishmeal had higher daily gains (194 vs. 163 g day(-1)), greater total weight increase (6.97 vs. 5.88 kg) and lower conversion of the milk than lambs from ewes fed soybean cake (P < 0.05). Difference in body condition score (BC) between Treatments E(1) and E(2) at beginning of the recovery period was eliminated during the 70 days. Amount of barley offered affected change in BC (0.64 vs. 0.48 points; P < 0.001) and final BC (P < 0.01). Total live weight and BC increases were higher in animals with larger amounts of barley during the recovery period (P < 0.01 and P < 0.001, respectively). In conclusion, the level of feeding after weaning had greater effects on total recovery of reserves than the level of energy restriction during lactation.