Effect of different levels of physically effective neutral detergent fibre from forage in whole corn grain-based diets for feedlot lambs

Context. The minimum requirements of physically effective neutral detergent fibre of forage (peNDF-F) in finishing diets for feedlot lambs has not been consolidated. Aims. The present study evaluated the effect of increasing levels of peNDF-F on growth performance, blood metabolites, carcass characteristics, and ingestive behaviour of feedlot lambs fed a whole corn grain-based diet. Methods. Forty-five Dorper x Santa In & ecirc;s rams, with an initial bodyweight (BW) of 22.6 +/- 5.3 kg (mean +/- s.d.) and 88 +/- 10 days old (mean +/- s.d.), were used. The experimental design was a randomised complete block (five treatments and nine blocks), defined by the initial BW and age at the beginning of the experiment. The experimental diets were formulated to be isonitrogenous and isoenergetic. The experimental diets were as follows: ground corn-based diet with 72 g/kg of peNDF-F from coastcross (Cynodon sp.) hay (CONT, positive control); whole corn grain-based diet without coastcross (Cynodon sp.) hay (0(pe)NDF-F); whole corn grain-based diet with 36 g/kg of peNDF-F from coastcross (Cynodon sp.) hay (36(pe)NDF-F); whole corn grain-based diet with 72 g/kg of peNDF-F from coastcross (Cynodon sp.) hay (72(pe)NDF-F); whole corn grain based diet with 108 g/kg of peNDF-F from coastcross (Cynodon sp.) hay (108(pe)NDF-F) (DM basis). Key results. The increasing concentrations of peNDF-F in whole corn-based diets reduced the dry-matter intake (P < 0.0001), average daily gain, feed efficiency, final BW, carcass characteristics (P < 0.05), AST (P = 0.01), and glucose concentration (P < 0.03). Additionally, the increasing concentrations of peNDF-F decreased the area (P < 0.02) and the length of ruminal papillae (P = 0.008). The rumination and chewing times (min/day) showed a quadratic response; a longer rumination time (P = 0.001) was observed with 72(pe)NDF-F and the longer chewing time (P = 0.006) with 108(pe)NDF-F. Conclusions. Whole corn grain-based diets can be used without the addition of pepNDF-F for lambs. Implications. Thus, utilisation of whole corn grain diet can be a strategy to successfully feed and fatten lambs to slaughter.