Intake and digestion by lambs fed a low-quality grass hay supplemented or not with urea, casein or cassava meal

Ten Polwarth×Texel lambs (21 ± 3 kg live weight), housed in metabolic cages and fed ad libitum a low-quality grass hay ( Cynodon sp.) were used in a replicated 5×5 Latin Square experiment to evaluate effects of supplement type on forage and total intake, rumen fermentation, microbial protein synthesis, digestibility and N retention. Supplements were a non-fibre carbohydrate (NFC) source ( i.e., cassava meal), NFC plus a degradable true protein N (TPN) source ( i.e., calcium caseinate), NFC plus a non-protein N (NPN) source ( i.e., urea:ammonia sulphate, 9:1), NPN alone or no supplement (control). Hay and fibre intake, as well as fibre digestibility, rumen microbial protein synthesis and N retention were lowest (P