Multiple supplements for beef heifers on pasture during the dry season: nutritional characteristics

The objective was to evaluate levels of multiple supplements supplied to beef heifers in low supply of pasture on intake and nutrients digestibility, pH and concentration of ruminal ammonia nitrogen, nitrogen balance, synthesis and microbial efficiency. Five Nellore heifers with initial body weight of 344.00 +/- 21.10 kg and average initial age of 22 months were used. The following supplements were evaluated as fed to the animals: control (mineral supplement) and supplementation levels of 2, 4, 6 and 8 kg/animal/day, composing the following percentages of body weight (BW): 0.55, 1.11, 1.66 and 2.22%, respectively. The experimental design was a Latin square with five replications and five supplements. Intakes of total dry matter, crude protein (CP) and total digestible nutrients, and total apparent digestibility of dry matter, crude protein, total carbohydrates and no fiber carbohydrates increased linearly (P <0.0001) and dry matter intake of forage decreased (P <0.0001) with supplementation levels. Supplementation strategies promoted reduction on ruminal pH (P = 0.0343) and increased concentration of ruminal ammonia nitrogen (NH3-N) (P = 0.0004) before the supply of supplements, and after, this NH3-N presented quadratic behavior (P = 0.0023). Nitrogen intake, excretion of urea in urine and nitrogen excretion in feces increased linearly (P <0.0001) according to supplementation levels. The supply of high levels of multiple supplements reduces forage intake and presents itself as an alternative to cattle maintained in a systems with low supply of pasture in the dry season.