Performance and nitrogen balance in growing-finishing pigs fed restricted or ad libitum diet with lowered protein content

The objective of the present study was to determine the effect of lowered by 10% feed crude protein level in relation to the requirements for pig feeding standards in mixture concentrates for fatteners fed a restricted or ad libitum diet on animal growth, feed conversion ratio and nitrogen balance. The animals (36 pigs) were assigned into 3 groups maintained in pens, 2 animals each. Group I (control) received standard mixture concentrates with a recommended crude protein and amino acids level in compliance with pig feeding standards, whereas the animals from for groups II and III had a diet with a reduced by 10% crude protein and amino acids content. The fatteners from group I and II were fed a restricted diet, while those from group III had free access to feedstuffs (ad libitum). The animals were weighed at the beginning of the experiment at 68-70 BW and before slaughter, with regular control of feed intake. The N-balance tests were performed in metabolic cages on 4 porkers from each group at 35, 55, 75 and 95 kg BW. The results, i.e. daily gains (896, 894 and 911 g daily) and feed conversion ratio (2.41; 2.42 and 2.64 kg/kg bodyweight gain, respectively, throughout the fattening period from 25 to 110 kg) in groups I, II and III as well as N-excreted in manure (36.5, 31.5 and 34.4 g N daily) indicated the potential to minimize nitrogen emission through feed protein reduction by 10% in relation to the pig feeding standards, in case of free access to feedstuffs.