NÃVEIS DE LISINA E ENERGIA EM RAÃÃES FORMULADAS COM BAIXO TEOR DE PROTEÃNA BRUTA PARA SUÃNOS EM CRESCIMENTO / Levels of lysine and energy in diets formulated with low crude protein for barrws on growth.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Two experiments were conducted to evaluate the effect of digestible lysine levels (DLys) in diets with low level of crude protein (CP) in different levels of metabolizable energy (ME), on the performance, carcass characteristics, balance of nitrogen and energy in growing barrows. In experiment I, were used 104 barrows from high genetic potential, with initial weight means of 22.5 Â 1.43 kg, housed in stalls of growth over a period of 31 days. In the experiment II were used 52 barrows, with an means weight of 36.13 Â 2.8 kg housed individually in a metabolism cages. The total amount of feed daily basis was based on metabolic weight (PV0,75). The experiment was conducted in four periods of 10 days, with 13 animals in each. The first seven days were used to adapt the animals and 3 days remaining to collect a total feces and urine. In both experiments, the animals were randomly divided into blocks in a factorial 3x4+1, three levels of ME (3060, 3230 and 3400 kcal / kg), four of DLys (0.7, 0.9, 1, 1 and 1.3%) in diets with 14% of CP and a control treatment with 3230 kcal ME /kg, 1.03% DLys and 18% CP, formulated according to national tables. In experiment I there was no interaction (P>0.05) between the levels of DLys and ME on the performance variables. In relation to means daily gain, the quadratic effect (P<0.05) shown that 1.08% of digestible lysine shown the best result, while the highest level of energy shown (P<0.05) lower feed intake, reflecting in a better (P<0.05) feed conversion by increased levels of digestible lysine (Dlys) up to 1,3%. Compared with the control treatment, any of these variables shown a significant difference (P>0.05). The levels of DLys and ME also influenced (P<0.05) the carcass characteristics, and 1.03% level Dlys shown better carcass yield in diet with 3230 kcal of ME, therefore these results were similar to the control treatment. In relation to longissimus muscle area, it was observed a quadratic effect (P<0.05) in the diets with 3230 and 3400 kcal ME /kg, and the best results were observed with 1.00 and 1.04% of DLys, respectively. Increasing levels of synthetic amino acids resulted in a linear increase (P<0.05) in the backfat tickness in the barrows fed diets formulated with 3060 kcal/kg. However the diet with 3400 kcal ME/kg resulted in a linear drop (P<0.05) in the thickness of same. Increasing levels of synthetic amino acids resulted in a linear increase (P<0.05) in the backfat tickness in the barrows fed diets formulated with 3060 kcalME/kg. The results also shown that diets with 3400 kcal ME/kg shown a linear decreased (P<0.05) in the thickness characteristics. The best meat:fat relationship in level 3230 kcal ME was obtained with 1.09% of digestible lysine. It is concluded that the levels of digestible lysine and metabolizable energy indicated in the national literature can be used in low crude protein diets, if the diets were supplemented with synthetic amino acids, without influencing the performance and the carcass yield of growing barrows. In the nitrogen and energy balance test (experiment II) the results shown that in 3060 kcal ME/kg levels there was quadratic regression (P<0.05) for absorbed nitrogen, 0.98% being the best lysine level. For nitrogen withheld in the level of 3400 kcal ME/kg there was a decreasing linear regression (P<0.05) for lysine levels. In the relationship nitrogen withheld /nitrogen absorbed, there was a decreasing linear regression (P<0.05) when 3400 kcal / kg was used, where the lower levels of DLys showed the best results. In the study of the energy balance in the highest energy levels (3230 and 3400 kcal/kg), there was (P<0.05) greater absorption of energy. For the retained energy variables and the relationship between energy retained /absorbed there was no interaction (P>0.05) between the levels of DLys and ME studied. There was no significant difference (P>0.05) between the experimental diets and diet control for these variables. It is concluded that the levels 3230 kcal ME/ kg and 1.03% of DLys may be used without affecting the use of nitrogen by growing pigs on diets with low content of crude protein.

ASSUNTO(S)

metabolismo aminoÃcidos sintÃticos zootecnia conformaÃÃo de carcaÃa nutriÃÃo

ACESSO AO ARTIGO

Documentos Relacionados