Levels of protected lysine and methionine in the diet of lambs: nutritional parameters and protein metabolites

The objective of this study was to evaluate the effect of inclusion of different levels of protected lysine and methionine on the nutritional parameters and protein metabolites of lambs. The experiment was carried out at the Capim Branco Experimental Farm, at Uberlândia Federal University, during the months of September and October 2016. Five blood lambs ½ Dorper × ½ Santa Inês, approximately eight months old and with an average weight of 50 kg, were distributed in a Latin square scheme 5 × 5 (five treatments and five replicates). The treatments consisted of the inclusion in the diet of different levels of lysine and methionine protected from ruminal degradation (MicroPEARLS LM®): 0 g, 8 g, 16 g, 24 g, and 32 g. The diet was composed of corn silage and concentrate in a ratio of 30V:70C.The experiment was divided into five phases. Each phase had a duration of fifteen days (ten days of adaptation of the animals to the experimental diets and five days of data collection). The animals were kept in individual metabolic cages. A digestibility assay was performed to determine the apparent dry matter intake and digestibility (DMI/DDMI), nitrogen balance, and protein metabolites. The DMI (kg day-1) and in relation to the metabolic weight presented a positive linear equation, and was highest for the treatment with 32 g of amino acids, as well as the ingested nitrogen and nitrogen balance, being positive in all treatments. There was no difference (P > 0.05) in the DDMI. The crude protein and urea concentrations remained above the recommended levels and the concentration of creatinine remained below the recommended level. The inclusion of protected amino acids up to 32 g increases DMI and urinary nitrogen excretion without negatively affecting digestibility. The protein metabolism was altered, without causing damage to the performance of the animals.