Levels of metabolizable energy and crude protein in rations formulated according to the concept of ideal protein and phytase for piglets of 15 to 35 kg / NÃveis de energia metabolizÃvel e de proteÃna bruta em raÃÃes formuladas segundo o conceito de proteÃna ideal e fitase para leitÃes dos 15 aos 35 kg

Marcelo JosÃ Milagres de Almeida

Two experiments were conducted in the Swine Production Sector of the Animal Science Department at UFLA to verify by using the metabolism, performance assay, blood parameters and comparative slaughter, the effects of different levels of metabolizable energy (ME) and crude protein (CP) in rations formulated according to the ideal protein concept and phytase for piglets of 15 to 35 kg. The rations were formulated based on corn, soybean meal, modified powdered milk and starch with the treatments in a factorial scheme 3 x 2 + 1, three being the levels of metabolizable energy (3,080, 3,230 and 3,380 kcal/kg), two of crude protein (14% and 16%), supplemented with synthetic aminoacids (lysine, methionine, threonine, tryptophan and valine) and supplementation of 1000 FTU/kg in the ration of NatuphosÂ10000 phytase, in addition to the additional treatment, formulated on the basis of CP and without any phytase to meet the nutrient requirements of piglets according to Rostagno et al. (2005). In all the trials, a randomized block design was utilized with six replications, the time of beginning of the experiment was considered as a block. For the factorial scheme treatments, the means were compared by the SNK test at 5%. For comparison of the additional treatment with the other treatments, Dunnet test at 5% was used. Experiment I was a metabolism trial with the purpose of evaluating the total digestibility of nutrients and excretion of minerals in the feces. A total of 21 commercial hybrid barrows pigs (Agroceres X MS60), with an average initial weight of 18.9 Â 1.9 kg, housed individually in metabolism cage (experimental plot) were utilized. In Experiment II, 84 barrows and gilts of the same genetic stock of the previous experiment (average initial = 15.3 Â 1.4 kg and final weight of 32.5 Â 3.1 kg) were utilized to evaluate the performance, blood parameters, body composition, weights of organs and bone mineralization. At the end of the experimental period, the blood of 42 animals was collected through a puncture in the sinus orbital. Three animals were slaughtered at the beginning of the Experiment II and, after the experimental periods ends, one animal of each pen was slaughtered; the liver, kidneys, stomach and small intestine were removed and weighed and the 3rd and 4th metacarpal bones were taken for analyses of ashes, Ca, P and bone resistance. In experiment I, there was a significant difference (P<0.01) among the levels of ME and CP, independent, for DE and among the levels of ME, independent of ME. In the metabolizable energy, the highest values were found for 3,380 kcal ME/kg and among the levels of CP for Nitrogen Intake (NI), nitrogen excreted in feces (NEF) and in urine (NEU), the lowest values being found with 14% CP and, for nitrogen retention (NR), with the highest values verified for 14% CP. In comparing the means of each combination of ME and CP with the control treatment, the digestibility coefficient of crude protein (CDPB), NI, NEF, NEU, RN, contents of ashes calcium and phosphorus in the feces were significantly influenced (P<0.05). The piglets fed rations with different levels of ME and CP, formulated on the basis of ideal protein and phytase showed decreased excretion of nitrogen, calcium and phosphorus and increased CDPB and RN relative to the control treatment. In experiment II, the levels of EM, independent of the levels of CP, influenced (P<0.01) ration intake, (P<0.05), fat percentage, fat deposition rate and energy retained in the carcass as fat, the highest levels being found for the levels of 3,380 kcal ME/kg. There was a significant difference between (P<0.05) CP, independent of ME utilized for efficiency of nitrogen utilization for gain (EUNG), the highest efficiency being found for the piglets fed rations with 14% CP. In the comparison of means of each combination of ME and CP with control, both EUNG and blood urea were significantly influenced (P<0,05). The piglets fed rations with different levels of ME and CP, formulated according to the concept of ideal protein and phytase showed higher EUNG and lower blood urea content relative to the control. It was conclude that the levels of ME, CP, Pd and Ca of the rations should be reduced to 3,080 Kcal/kg, 14% , 0.54% and 0.28%, respectively for piglets when the rations were formulated based on ideal protein concept with supplementation of phytase without affecting the piglets performance, the body composition and bone mineralization of piglets from 15 to 35 kg.These results shown that manipulating ration it is possible a reduction of 36% in the nitrogen excretion in the feces and 44% in the urine nitrogen and 31% phosphorus in the feces, contributing this way to the reduction of the environmental poluition due to swine dejects.

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