Evaluation of differential energy and protein supplementation to maize silage for slaughter lambs An investigation was conducted into the effects of dietary protein and energy content as well as protein source in slaughter lamb production on maize silage plus maize meal diets. Maize silage was fed ad lib. as a basal diet and maize meal was offered at one of the following three levels, viz.: (a) 1% of body mass from 17 to 40 kg, (b) 1% of body mass from 17 to 30 kg and then increased to 2% from 30 to 40 kg and (c) 2% of body mass from 17 to 40 kg. Each of the above 3 energy treatments were subdivided into 2 protein treatments, viz.: (i) 14% crude protein content from 17 kg weaning to 40 kg (slaughter) and (ii) 14% crude protein content from 17 to 30 kg body mass which was reduced to 11% crude protein content from 30 to 40 kg body mass. In these diets fish meal was the only protein source used. Two further treatments were included to test the replacement offish meal on an iso-nitrogenous basis with 2 different protein sources viz. a commercial product containing starch and urea (Starea) and a mixture of lucerne meal and urea. In these 2 treatments maize meal was fed at 1%of body mass from 17to 30 kg and 2% from 30 to 40 kg body mass. The protein levels were 14% of dry matter intake from 17 to 30 kg and 11% from 30 to 40 kg body mass. From the results it was evident that the replacement of fish meal with either of the other protein sources resulted in a significant reduction in growth rate; On all diets except on the one containing Starea, the growth rate increased after the experimental animals reached 30 kg body mass. In the group where Starea was used as a N-supplement, the growth rate gradually declined to a daily rate of 81 g/ day. The carcase grade was Super for all treatments. Slaughter percentages were significantly higher for the NPN treatments. The slow growth rates observed where NPN was included were ascribed to a possible earlier deposition of fat.