Effect of Supplementation Plans and Frequency on Performance and Metabolic Responses of Grazing Pregnant Beef Heifers.

Our objective was to evaluate the effects of protein supplementation frequency and supplementation plans during gestation on productive performance and metabolic responses of grazing super-precocious Nellore heifers. Thirty-five pregnant Nellore heifers were used in a completely randomized design in a 2 × 2 factorial arrangement with an additional control group. The factors were the following: 1. Frequency of supplementation: (a) Daily (seven times per week), (b) Infrequent (three times per week); 2. Supplementation plans: (a) Constant, (b) Increasing. A control group with no supplementation was included. Two digestibility trials were carried out on the 40th and 130th experimental days. Productive performance and body composition were evaluated in the prepartum and postpartum periods. Blood samples were collected at -114, -113, -15, -14, +15, +30, and +45 days relative to calving for measuring metabolic status. Supplementation (daily and infrequent) increased the intake of total dry matter (DM) (p ≤ 0.004), average daily gain (p < 0.001), and body weight at calving (p = 0.008) at prepartum. However, frequency or supplementation plan did not alter (p > 0.17) the intake of total DM and forage DM. There was an effect (p ≤ 0.02) of the supplementation plan on subcutaneous thickness fat in the prepartum period and albumin and non-esterified fatty acid concentrations (p < 0.004) in the postpartum period. Nonetheless, frequency and supplementation plans did not affect (p ≥ 0.10) heifers' productive performance during the postpartum period. In conclusion, protein supplementation frequency and supplementation plan during beef heifers' gestation do not negatively impact their productive performance or metabolic responses.