WANDEE TARTRAKOON, KATTIKA WUTHIJAREE, KWANCHAT UDOMSRI
Chiang Mai University, Department of Animal Science, Thailand
The influence of protein level in pig diets on nitrogen excretion was evaluated using three crossbred barrows (DxLWxLR) in a 3 x 3 latin square design study. The pigs were fed with one of grower pig (50kg BW) diets containing 18, 16 and 14% crude protein (CP), respectively, with the same 0.77% apparent ileal digestible lysine. The finisher pig (65kg BW) diets contained 15.5, 13.5 and 11.5% CP, respectively, with the same 0.61% digestible lysine. The diets were referred to as diets 1, 2 and 3, respectively. Average feed intake (FI, g d-1) of grower pigs fed diet 3 tended to be lower than others. As a result, the pigs fed diet 3 had significantly lower (p < 0.05) average N intake (Ni; g d-1) than the pigs fed diet 1. Urinary N (Nu; g d-1) and faecal N (Nf; g d-1) excretion was significantly lower (p < 0.05) for the pigs fed diets 2 and 3 than the pigs fed diet 1. There were no significant (p > 0.05) differences in Nu:Nf ratio among treatments. The pigs fed diet 3 had lowest (p < 0.05) N excretion in slurry (Ne, g d-1 and % Ni) and had highest (p < 0.05) N retention. There were no significant (p > 0.05) differences in FI among treatments in finishing phase. However, Ni of pigs fed diet 3 tended (p > 0.05) to be lower than the others and tended (p > 0.05) to have lowest Nu. On the other hand, the pigs fed diet 1 had the highest (p < 0.05) Nf and tended (p > 0.05) to have the highest Ne. Results of the present study showed that the reduction of CP from 18 to 14% in grower pig diet could reduce N in urine, faeces and slurry by 84.72, 42.65 and 56.42%, respectively while the reduction of CP from 15.5 to 11.5% in finisher pig diets reduced N in urine, faeces and slurry by 59.80, 27.98 and 32.25%, respectively. Dietary CP can therefore be reduced to 14 and 11.5% in the growing and finishing phases of pig diets, respectively.
Keywords: Finishing pigs, growing pigs, low protein diet, N-excretion