Mineral supplementation of dairy heifers in Marandu-Grass pasture in spring and summer seasons

ABSTRACT Here in this study we assessed dairy heifers kept in tropical grasslands during spring and summer seasons to observe the effects of two supplementation strategies upon their performance. Sixteen dairy heifers (Holstein 5/8 x Gyr 3/4) with 135.25 kg of body mass were randomly assigned in two supplementation treatments (e.g., mineral salt and protein salt supplement) during spring and summer seasons, divided into two groups of eight animals that represented 4.29 animal unit ha. Initial and final fasted weights (i.e., feed and water withheld for 16h) were obtained before to start and at the end of each grazing cycle (28 days), and then the weight gain (kg animal-1) per grazing cycle was calculated by the difference between final and initial weights. There was no significant effect (P <0.05) on the intake of dry matter, crude protein, ether extract, neutral detergent fiber, and dry matter digestibility, between treatments (P <0.05). However, there was a significant effect (P <0.05) between seasons; e.g., respective means of dry matter intake (kg day-1,% BW g / kg 0.75), intake of crude protein (g day-1 g / kg 0.75), ether extract (g day-1), neutral detergent fiber (g day-1 and% BW) were 3.95 and 2.88 kg, 2.54 and 1.65%, 89.27 and 59.56 g kg0.75, 429.89 and 298.43 g day-1, 9.72 and 6.18 g kg0.75, 118.79 and 84.07 g day-1, 2.90 and 2.05 kg day-1, 1.86 and 1.18%, for Spring and Summer seasons. Moreover, the dry matter intake (% BW and g kg 0.75 of DM) were higher (P < 0.05) during the spring season (e.g., 2.53 vs 1.64 % BW; and 89.26 vs 59.56 g kg0.75 DM).