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

2007, Animal Feed Science and Technology

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<0.05) in lambs supplemented with NFC alone. Total organic matter (OM), digestible energy intake, rumen microbial protein synthesis and N retention improved (P<0.05) with supplementation with NFC plus either TPN or NPN. Rumen pH, as well as rumen concentrations Abbreviations: ADFom, acid detergent fibre (exclusive of ash); ADIN, acid detergent insoluble N; CHO, total carbohydrate; CM, hay plus cassava meal; CMCA, hay plus cassava meal plus calcium caseinate; CMU, hay plus cassava meal plus urea; CP, crude protein; DE, digestible energy; DM, dry matter; EE, ether extract; H, hay alone; lignin(sa), lignin determined by the sulphuric acid method; LW, live weight; OM, organic matter; NFC, non-fibre carbohydrate; aNDFom, neutral detergent fibre (with a heat stable amylase and exclusive of ash); NDIN, neutral detergent insoluble N; NPN, non-protein N; RDP, rumen-degradable protein; OMTD, OMtrue digestibility; TPN, true protein N; U, hay plus area * Corresponding author. Tel.: +55 55 3220 8355; fax: +55 55 3220 8355.