Evaluation of reduced nutrient levels in growing-finishing pig diets
Résumé
The aim of this study was to evaluate the effects of a nutritional program with reduced nutrient content, on nutrient ingestion and nitrogen (N) and phosphorus (P) balance in growing-finishing pigs from 25 to 130 kg body weight. Forty gilts and 40 barrows (24.5±1.8 kg) were distributed in a randomized block design with two treatments, 10 replications per treatment, and four animals per experimental unit. The feeding program was in four phases. Two diets were formulated for each feeding phase. One was adjusted using InraPorc® model to minimize the nutrient excess (LN), and the other (SN) was formulated with standard Brazilian recommendations. Nutrient consumption was measured and N and P balance were determined according to intake and retention. Data were subjected to ANOVA with the main effects of treatment, block, sex and interaction between treatment and sex. Over the whole experimental period, there was no statistical difference (P>0.10) between treatments for energy intake (mean of 33.3 MJ ME/d) and average daily gain (0.92 kg/d). Dietary treatments affected (P<0.05) daily lysine (18.9 vs 21.3 g/d), crude protein (352 vs 419 g/d) and P (11.3 vs 12.6 g/d) intake, with lower values for LN pigs. Nitrogen (28.8 vs 38.0 g/d) and P (5.7 vs 6.5 g/d) excretion were lower (P<0.05) for LN pigs, without difference (P>0.05) on body retention (n=23.5 and P=4.8 g/d). This resulted in higher nutrient utilization efficiency in animals that were fed with the adjusted diet. The sex affected (P<0.05) all variables, with the gilts showing lower intake and excretion values than barrows. According to these results it seems possible to reduce the levels of nutrients that are commonly used in Brazil, without affecting the N and P retention. Moreover, nutritional adjustment proves to be an efficient tool to reduce nutrient excretion and, consequently, environmental impacts.