The Effect of Level of Crude Protein and Available Lysine on Finishing Pig Performance, Nitrogen Balance and Nutrient Digestibility

摘要

Two trials were conducted to investigate the effect of decreasing the crude protein (CP) content of diets for finishing pigs containing two levels of available lysine on nutrient digestibility, nitrogen (N) balance and production performance. Ten finishing lets containing five levels of CP (on average 144, 155, 168, 182 and 193 g/kg fresh basis) and two levels of available lysine (6.9 and 8.2 g/kg fresh basis) were formulated. The diets were offered to pigs on a performance trial (n = 800 Large White(LW)xLandrace (LR) pigs) from 10 wk of age until finish at 21 wks+5 d of age. Average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were calculated. In addition, a digestibility/N balance trial was conducted using pigs (n = 80 LWxLR) housed in metabolism crates. Digestibility of dry matter (DM), CP, oil, fibre and energy was determined. N balance values were determined anatysis of N content of urine and faeces (‘as determined’). N balance values were also calculated using ADG values and indicated that 16% of growh is protein deposition (“as calculated”). Pig performance was poor between 10 and 13 wk of age which indicated that the dietary treatments were nutritionally inadequate for pigs less than 40 kg. Therewas a significant (p<0.01) quadratic effect o increasing CP level on feed intake, ADG and FCR from 10 to 13 wk which indicated that the lower CP levels did not supply equa e levels of essential or non-essential amino acids. There was no effect of increasing available lysine level throughout the early drive optimum with the response in older pigs, suggested that both 8.2 and 6.9 g/kg available lysine were insufficient to. There was a positive response (p<0.05) to increasing available lysine level from 13 wk to finish which indicated that 6.9 g/kg available lysine was not adequate for finishing pigs. Energy digestibility decreased with decreasing CP level of diets g 6.9 g/kg available lysine which may be attributed to the higher fibre content of the lower CP diets. Nitrogen excretion (gd) red when dietary CP was reduced regardless of whether the values were determined through balance or calculated using ADG. balance N excretion decreased linearly (p<0.001) and quadratically (p<0.001) with decreasing dietary CP content. When the N gures calculated in this study were compared with those quoted in the Northern Ireland and English Nitrates Directive Action rogrammes, N excretion was less per pig (wean to finish) offered a 169 g/kg CP, 8.2 g/kg available lysine diet (2.39 kg vs 3.41 kg ern Ireland) and 2.93 kg (England)).