FURTHER-STUDIES ON THE RESPONSE OF LACTATING EWES TO DIETARY-PROTEIN

Four experiments were made during early lactation on individually penned Finnish Landrace × Dorset Horn ewes, each suckling two lambs. In Experiment 1, 14 ewes of mean body weight 74 ± 2·4 kg received daily, 1·9 kg dry matter, 20 MJ of metabolizable energy and 300 g of crude protein from a diet (H) containing hay, barley and fish meal. Reduction of the daily crude protein intake of half the ewes to 225 g by replacing fish meal with barley (diet L) in week 2 of lactation resulted in a decrease (P< 0·01) in daily milk yield of 0·53 kg (17%) compared with no change for ewes remaining on diet H. The effect was reversed by returning the ewes to diet H at the end of week 3. In Experiment 2 the use of four ewes fitted with abomasal cannulae showed that the additional non-ammonia nitrogen reaching the abomasum when fish meal was given was used with an efficiency of 0·51 for the production of milk nitrogen. In Experiment 3, involving 20 ewes, a restriction in protein intake for more than 10 days in early lactation by replacing the fish meal with barley depressed subsequent milk yield. In Experiment 4, 24 ewes were given either fish meal, soya bean meal or groundnut meal as protein supplements. In early lactation fish meal was superior by 0·40 and 0·43 kg of milk per day to soya bean meal and groundnut meal respectively, and this was attributed to the greater quantity of non-ammonia nitrogen reaching the abomasum in the fish meal compared with the soya bean meal and groundnut meal supplements. The commercial significance of the results is discussed. © 1979, British Society of Animal Science. All rights reserved.