ENERGY AND NITROGEN DIGESTIBILITY AND RETENTION BY PIGS AS INLUENCED BY DIET, SEX, BREEDING GROUP AND REPLICATE

Apparent digestible energy (DE) and nitrogen (DN), metabolizable energy (ME) and nitrogen retention (NR) of high (HE) and low (LE) digestible energy diets were determined with Duroc × Yorkshire, Hampshire × Yorkshire and Yorkshire pigs at an average weight of 50 kg. The diets were formulated to contain similar ratios of crude protein, lysine, methionine and cystine and calcium to estimated DE. The coefficients of DE, ME and DN were higher (P < 0.01) for the HE diet than for the LE diet. A lower percentage (P < 0.05) of digestible N was retained on the HE than on the LE diet. Digestibility of N did not significantly influence NR. The results suggest that standard NR procedures overestimate the actual protein retained by pigs. ME was a relatively constant proportion (96.2%) of DE, suggesting that either DE or ME may be used with equal accuracy in describing energy requirements for swine. Sex and breeding group did not significantly affect DE, ME, DN, or NR. There was a diet × replicate interaction (P < 0.01) for DN. A lower intake of the LE diet was associated with a higher DN coefficient. The study suggests that DE, ME, and DN values may be used for diet formulation without need of correction for breed or sex.