Ensiling Sorghum with Urea, Aerobic Exposure and Effects on Intake, Digestibility, Ingestive Behaviour and Blood Parameters of Feedlot Lambs

SIMPLE SUMMARY: Urea, due to its fungicidal effect, when used as a chemical additive in sorghum ensilage improves the aerobic stability of the silage, minimising material losses after opening and exposure to oxygen. Thus, sorghum silage, as a source of roughage, when treated with up to 2% urea based on natural matter, can be used in the feeding of beef sheep in the growth phase, without harming the productive performance of the animals. We also hypothesised that sorghum silages treated with urea, given the potential of this additive, present greater aerobic stability compared to sorghum silages that were not subjected to chemical treatment during ensiling. In this way, it is possible to maintain them for a longer period exposed to oxygen, so that there is little impairment of ingestion, performance and nutritional value of this silage until consumption. ABSTRACT: This study was carried out to evaluate the effect of ensiling sorghum silage with urea and amending the aerobic exposure nutrients intake and apparent digestibility, ingestive behaviour and blood serum metabolites of feedlot lambs. Forty uncastrated crossbred Dorper × Santa Inês lambs, aged 150 ± 15 days and with an initial body weight of 21.73 ± 2.40 kg, were used. Animals were assigned in a 2 × 3 factorial arrangement. Thus, six silage diets were produced with various urea addition levels (UA: 0 and 5 g/kg on a natural matter basis) and periods of aerobic exposure of silages (PAE: 0, 24 and 48 h). An effect was observed for nutrient intakes of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre corrected for ash and protein (NDFap) and total digestive nutrients TDN (g/day) and for the total apparent digestibility of DM, OM and CP. There was an interaction effect between urea levels and aerobic exposure for ether extract (EE) and NDFap intakes (g/kg) and nonfibrous carbohydrate (NFC) digestibility (g/kg) (p = 0.012). The addition of 5 g/kg of urea to sorghum ensilage improved the digestibility parameters without changing dry matter intake and ingestive behaviour. The addition or not of urea does not change the blood parameters of the animals.