Intake, digestibility, ruminal parameters, and performance in lamb fed with increasing levels of red propolis extract.

The objective of this study was to examine the effect of increasing levels of red propolis extract (RPE) on the intake, digestibility, feeding behavior, rumen parameters, metabolic parameters, and performance of feedlot lambs. Thirty-five uncastrated male Santa Inês lambs with an initial weight of 17.08 ± 2.36 kg were used in a completely randomized design with five treatments (0, 7, 14, 21, or 28 mL RPE/animal/day). The animals were confined for 68 days. Red propolis extract induced a negative quadratic response (P < 0.05) in the intakes of dry matter, organic matter, crude protein, ether extract, neutral detergent fiber, non-fibrous carbohydrates, and metabolizable energy. The apparent digestibility coefficients of dry matter, organic matter, and neutral detergent fiber, as well as the rumen concentration of NH3-N, also responded quadratically (P < 0.05) to RPE. Feeding efficiency increased linearly (P < 0.05) with the inclusion of RPE, whereas rumination efficiency was maximum (P < 0.05) at the RPE level of 16 mL/day. Red propolis extract induced a linear response (P < 0.05) in serum total protein, albumin, creatinine, and gamma-glutamyl transpeptidase. There was a quadratic effect on final body weight and average daily gain with minimum values for inclusion of RPE of 12.89 mL/day and 10.93 mL/day respectively. Feed efficiency rose linearly (P < 0.05) with the increasing concentrations of RPE in the diet. The inclusion of 21 mL RPE/day (8.5 mg total flavonoids/mL) in the diet of feedlot lambs is recommended to reduce the rumen NH3-N production and increase the animals' performance.