Effects of frequency of supplementation during peri and postpartum of grazing primiparous Nellore cows

The goal with this study was to evaluate the effects of supplementation frequency during pre (105 d from parturition) and postpartum (105 d from parturition) of Nellore primiparous cows on performance and physiological responses. Twenty-five pregnant heifers with average BW of 408±2 kg and 172±2 d of gestation were used in this trial. Animals were housed in 6 paddocks with full access to water and stocking rate was defined on the basis of potentially digestible DM availability (DMpd). Evaluated treatments were: control – (ad libitum mineral mix); daily supplementation – (1.5 kg of concentrate /animal); and every 3-d supplementation – (4.5 kg of concentrate/animal). Two 9-d digestibility trials were performed at 55 d before parturition and 55 d after parturition. Plasma concentrations of glucose, IGF-1, NEFA, beta-hydroxybutyrate (BHB) were used as indicators of energy state and collected at 27 and 9 d before parturition, on the day of parturition, and 9 and 27 d after parturition. The response variables were analyzed using PROC MIXED in SAS 9.4 (SAS Inst., Cary, NC) assuming a completely randomized design with 3 treatments and 2 replicates per treatments. Treatment was considered fixed effect whereas treatment within paddock considered random. The DMpd observed during the experiment for pre and postpartum was 4.4 t/ha and 2.9 t/ha, respectively, which corresponded to the momentary mean availability of 78.6 and 52.9 g/kg BW. The DMI was not affected by supplementation frequency during peripartum (P>0.10) or postpartum (P>0.10). The supplementation frequency did not affect BW neither at 10 d before parturition (P>0.10) nor at 105-d after parturition (P>0.10). Glucose concentration was affected by supplementation frequency, (72.27 vs. 65.62 mg/dL for pre and postpartum respectively; P<0.10). Most likely, daily supplementation reduces oscillation and increases circulating concentrations of glucose. Circulating concentrations of IGF-1 (206 vs. 222 vs. 201 ng/mL for pre and postpartum respectively; P>0.10), NEFA (0.21 vs. 0.23 vs. 0.18 mmol/L for pre and postpartum respectively; P>0.10) and BHB (0.45 vs. 0.52 vs. 0.45 mmol/L for pre and postpartum respectively; P>0.10) did not differ among treatments. The forage availability associated with lack of supplementation frequency effect on intake may have contributed to no changes in performance and physiological responses. These results suggest that when there is non-restriction on forage availability, supplementation frequency during pre and postpartum does not affect performance or physiological responses of primiparous Nellore cows.