Pig growth, body composition and nutrient balance with local protein sources no mineral phosphate, but with amino acid and phytase supply

Surplus of nitrogen (N) and phosphorous (P) in agricultural system and reliance on imported protein feed and mineral phosphates (MP) challenge Swiss pig production. The objective was thus to feed pigs from 22 to 105 kg body weight (BW) grower and finisher diets without imported protein sources and MP and with minimal contents of crude protein (CP) and P. The 48 pigs were blocked by litter, gender and BW. Each pig of a block was assigned to 1 of the 4 iso-energetic diets (C=control, N-=minimal use of soybean meal, P-=no MP, and N-P-=combination of N- and P-). In N-, soybean meal was replaced by local protein sources and synthetic amino acids (AAs) to reach minimal CP, but equal digestible AA contents as in C. In P-, MP was removed and calcium:dP ratios remained as in C by adjusting CaCO3. All diets were supplemented with 750 FTU/kg of microbial phytase. Compared to C, grower and finisher N- diets contained respectively 2.7% and 0% soybean meal and 140 and 116 g CP/kg, leading to 10% and 15% less CP; diets with P- contained 2.2 and 2.0 g digestible (dP)/kg, and 3.4 and 3.0 g P/kg, leading to 24% and 21% less dP, and 20% and 22% less P. Daily individual feed intake and BW at start, diet change and end were recorded. Nutrient excretion was derived by subtracting nutrient intake and body nutrient accretion derived from body composition assessment by dual X-ray absorptiometry at the start, diet change and end. There were no interactions (P>0.05) between N- and P- effects. Growth performance was not affected by N- and P- effects, except that P- impaired finisher feed conversion rate (P<0.05, 2.66 vs 2.60). Diets did not affect pig’s body composition except that P- reduced bone mineral content (P<0.001). Excretion of N and P were reduced (P<0.01) in grower, finisher and overall periods by N- and P-, respectively. These findings illustrate that the substitution of imported protein sources with local ones and AAs, the complete removal of MP, combined or separately permitted to reach minimal CP and P contents and was successful in reducing N and P excretion, while maintaining pig’s growth.