Performance and metabolic status of grazing beef heifers receiving increasing protein supplementation pre- and postpartum

The objective of the present study was to evaluate the effect of increasing levels of prepartum and postpartum protein supplementation on nutrient intake and digestibility, productive performance and metabolic status of beef heifers on tropical pasture. Twenty-eight pregnant beef heifers with bodyweight and body condition score of 459.7 +/- 6.8 kg and 5.8 +/- 0.10 respectively, were used. The experiment was performed according to a completely randomised design, with the following four treatments: 0.0, 0.4, 0.8 and 1.2 kg/animal.day of protein supplement containing 25% crude protein. All animals received a mineral mixture ad libitum. The experiment lasted 210 days, divided into three experimental periods. The supplementation level increased the intake of all evaluated nutrients, digestibility of organic matter, neutral detergent fibre corrected for ash and protein, as well as higher average daily gain prepartum and bodyweight of calves at birth (P < 0.05). Protein supplement at the levels evaluated did not affect body condition score (P > 0.05). An interaction effect between treatment x days in relation to calving occurred for concentrations of serum urea nitrogen, total proteins, albumin and globulins (P < 0.05). Supplementation did not affect glucose, triglyceride, non-esterified fatty acids, beta-hydroxybutyrate or progesterone (P > 0.05). In conclusion, supply of up to 1.2 kg/day of protein supplement for grazing beef heifers optimises forage intake and average daily gain before calving, and improves the indicators of the protein status.