Abstract
The objective of this study was to evaluate the effects of including slow-release urea microencapsulated in beeswax in the diet of adult sheep on intake, digestibility, and nitrogen (N) balance. Two microencapsulated system formulations were developed with ratios (wt/wt) of 1:2 (UME1:2) and 1:2 + sulfur (UME1:2+S) between the core (urea) and encapsulant (beeswax). The UME1:2 formulation had greater yield values, microencapsulation efficiency and thermal stability than UME1:2+S. The most efficient formulation (UME1:2) was added to the diet of twenty-four uncastrated male sheep, adult, crossbred Santa Inês, 9 months old with an average body weight of 28.2 kg ± 0.6 kg. The experimental arrangement was a completely randomized design in which the animals were distributed into four treatments that included different levels of urea microencapsulated in beeswax, UME1:2 without S (0, 1.5, 3.0 and 4.5% in total dry matter (DM)), and six replicates in a total experimental period of 19 days, with 14 days for adaptation. The inclusion of urea microencapsulated in beeswax did not affect (P > 0.05) DM, crude protein, ether extract, ash, total carbohydrate or crude energy intake or digestibility. In addition, the nonfibrous carbohydrate (NFC), neutral detergent fiber (NDF), and acid detergent fiber (ADF) intake, N intake, N excretion (urinary and fecal), N absorbed, N retained, N retention/N intake and N retained/N absorbed were not affected (P >0.05) by the inclusion of urea microencapsulated in beeswax. However, there was a linear increase in NDF (P = 0.031) and ADF (P = 0.004) digestibility as the inclusion level of encapsulated urea increased from 0 to 4.5%. The NFC digestibility showed a quadratic increase (P <0.001) with the greatest digestibility at 3.0% microencapsulated urea. Beeswax was shown to be an efficient microencapsulant to obtain microparticles containing urea, and the formulation of UME1:2 without the addition of S is recommended since it showed better yield and efficiency than the formulation with S. The inclusion of up to 4.5% urea microencapsulated in the lipid matrix of beeswax is recommended to improve NDF and ADF digestibility without affecting intake and N balance.
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