Utilização de enzimas Exógenas na nutrição de ovinos

Abstract

The present study was divided into four experiments aiming to evaluate the effects of different types and dietary levels of exogenous enzymes on feed intake, digestibility, nitrogen and energy balance, feeding behavior and blood metabolites in sheep. The experiments were conducted at the Federal University of Uberlândia in the Sheep and Goat Research Center of the Capim Branco farm from February to May 2017. The treatments consisted of a control diet and four inclusion levels of enzymes (0.5; 1.0; 1.5 and 2.0%). The commercial products evaluated were AMAIZETM (amylolytic enzyme), FIBROZYME® (fibrolytic enzyme), ALLZYME® SSF (enzyme complex), and a MIX of these three products in equal proportions. All animals were housed in individual metabolic cages for sixty days. All experiments were conducted using a Latin square design (5x5), with five treatments and five replicates. The dietary inclusion of the amylolytic enzyme (AMAIZETM) was evaluated in experiment I. Five ewe lambs with a mean initial body weight of 54.04 ± 4.5 kg and aged eight months were used. There was a significant difference for apparent digestibility coefficient of dry matter, organic matter, total carbohydrates, non-fibrous carbohydrates, total digestible nutrients, and gross energy digestibility. Enzyme level had a quadratic effect on gross energy digestibility, reaching its peak at 0.82% of enzyme inclusion. The same trend was observed for dry matter digestibility. The remaining parameters were not influenced by the dietary inclusion of the amylolytic enzyme. The dietary inclusion of the fibrolytic enzyme (FIBROZYME®) was evaluated in experiment II. Five ewe lambs with a mean initial body weight of 46.48 ± 5.60 kg and aged seven months were used. Creatinine concentration decreased linearly by 0.22 mg/dL with each 0.5% addition of enzyme, whereas the remaining parameters were not affected by the dietary inclusion of the fibrolytic enzyme. The dietary inclusion of an enzyme complex composed of pectinase, protease, phytase, beta-glucanase, xylanase, cellulase, and amylase (ALLZYME® SSF) was evaluated in experiment III. Five ewe lambs with a mean initial body weight of 61.16 ± 5.80 kg and aged eight months were used. There was a significant difference for the blood metabolites albumin and aspartate aminotransferase (AST), with linear reductions of 0.085 mg/dL and 8.9 IU/L with each 0.5% addition of the enzyme complex, respectively. However, the enzyme complex was not effective in altering the feed intake and nutrient digestibility in lambs. The dietary inclusion of an enzyme MIX composed of three commercial products at the equal proportions ( AMAIZETM; FIBROZYME®; and ALLZYME® SSF) was evaluated in experiment IV. Five male lambs with a mean initial body weight of 25.89 ± 2.6 kg and aged four months were used. There was no significant difference for dry matter intake as a percent of body weight (%BW-1) and metabolic weight (BW0.75). There was no significant difference for apparent digestibility coefficient of dry matter and fecal score. The fecal output weight (organic matter basis) differed significantly in lambs fed different inclusion levels of the enzyme MIX. The water intake increased linearly by 183 mL with each 0.5% addition of the enzyme MIX. The blood metabolites glucose and aspartate aminotransferase reduced linearly with the inclusion of the enzyme MIX. Only the enzyme MIX and AMAIZETM products caused significant effects on apparent digestibility and nutrient intake. Products capable of degrading specific substrates such as starch or cellulose are necessary for enzymes to function properly and to exert their lytic effects on the ruminoreticular environment, resulting in higher ruminal degradation rates of nutrients and improved animal performance.