Supplementation of Molasses-Based Liquid Feed for Cattle Fed on Limpograss Hay

SIMPLE SUMMARY: Seasonality in forage production may limit the quantity and quality of forage. Even when forage is available in the period of scarcity, protein might still be a limiting nutrient in animal performance. Feed supplementation is a powerful tool to adjust nitrogen (N) levels in the diet of ruminants during critical periods. Urea is commonly used as a source of non-protein nitrogen in molasses supplements. This dietary protein provides amino acids as well as nitrogen for microbial protein synthesis. Moreover, molasses has organoleptic characteristics, such as palatability, increasing dry matter intake, through microbial growth, especially for fiber-digesting bacteria. The objective of this work was to evaluate the effects of different levels of liquid supplementation based on molasses enriched with 32% crude protein (as fed; 45% on DM basis) on ingestion, digestibility, and rumen fermentation. The results of this study indicated that addition of a molasses-based liquid feed to a Hemarthria altissima hay-based diet can improve the nutrient supply to animals; notably, volatile fatty acids (VFA) and microbial N. Liquid supplementation had an additive effect on intake of animals fed Hemarthria altissima hay but did not increase hay intake. ABSTRACT: Two experiments were performed to evaluate the effects of (1) different levels of liquid supplementation (LS) based on molasses enriched with 32% (as fed; 45% on DM basis) crude protein (CP) on intake of Hemarthria altissima hay (LH), digestibility, and rumen fermentation, and (2) different levels of LS based on molasses enriched with 32% CP in the in vitro gas production in LH diets. In Exp. 1, twelve heifers and 12 adult male castrated and cannulated cattle were used. Treatments were allocated in a randomized block design, in four treatments: (CTL) access ad libitum to the LH; (SUP2) ad libitum access to LH and supplementation with 0.9 kg d(−1); (SUP4) ad libitum access to LH and supplementation with 1.8 kg d(−1) and; (SUP6) ad libitum access to LH with 2.7 kg d(−1). In Exp. 2, treatments were carried out in a randomized block design with four different proportions of LH diet: (CTL) 100 LH, (SUP2) 85 LH and 15 LS, (SUP4) 70 LH and 30 LS, (SUP6) 55 LH and 45% LS. In Exp. 1, liquid molasses-based supplementation did not affect LH intake (p > 0.05). Molasses intake improved as the supply increased, not reducing the intake of LH. In Exp. 2, the addition of LS to the LH caused a change in the VFA profile, with an increase in propionate production in vitro.