Abstract
The response of energy supplementation was evaluated on the development and reproductive performance of beef heifers on temperate grasslands. Twenty-eight Charolais × Nellore heifers, with initial average age of 18 months and initial live weight of 274.9 kg were utilized. The animals were maintained on oat + ryegrass pasture and distributed in the following treatments: no supplementation (NS): heifers kept exclusively on pasture; MEG: supplementation with protected fat Megalac®; BRM: supplementation with brown rice meal; BRM+MEG: supplementation with BRM + protected fat. The average final weight of the heifers was of 403.4 kg and corresponded to 89.5% of the adult weight. The body condition of heifers increased linearly with daily increase of 0.012 points, correlating positively with the final weight. There was interaction between treatment and period for average daily weight gain. The highest daily weight gain, 1.395 kg, occurred in the first period when the animals were supplemented with BRM+MEG. In the last period, the NS animals presented the lowest daily weight gain, 0.888 kg. Supplementation with brown rice meal and/or protected fat does not interfere in the intake of pasture by heifers or increase the total intake of dry matter, not changing, therefore, the average daily weight gain at the end of the period of grazing. The daily weight gain does not change during supplementation. The use of temperate pasture with and without supplementation promotes the proper development of the structure and reproductive tract of heifers, benefiting the animal performance indexes in the first mating at 25-27 months of age.
Highlights
Rearing replacement heifers is certainly one of the most important stages within the reproductive system aimed at breeding, where improving the reproduction of young females, through the additional inclusion of food in the process of growth is important for increasing the productivity of this system (Barcellos et al, 2003)
The Megalac® supplement intake for the treatment which received only the product was inferior to the treatment which was mixed with the brown rice meal, a fact that was associated with their low palatability when provided as the sole source of supplementation, which stops occurring when mixed with another product accepted by cattle
The contribution of crude protein (CP) of the pasture (Table 1) was above the requirements for maintenance and gain for beef heifers over the year, 126 g/kg of dry matter (DM), according to the NRC (1996), which would enable the use of only energy supplementation up to 11.2 g/kg of live weight (LW) with no protein deficit
Summary
Rearing replacement heifers is certainly one of the most important stages within the reproductive system aimed at breeding, where improving the reproduction of young females, through the additional inclusion of food in the process of growth is important for increasing the productivity of this system (Barcellos et al, 2003). Much of the low animal productivity of most Brazilian properties happens due to the deficiency in pasture management and lack of forage and property planning (Lupatini, 2000). In this context, the incorporation of temperate grasslands exactly during the period of greatest forage need has crucial role for beef cattle. The use of supplements rich in fat such as brown rice meal and protected fat may improve the use of temperate grasslands, because, according to Pascoal et al (2000), these pastures present high crude protein content, and the energy level is the limiting factor for the animal performance. The response of the supplementation with brown rice meal and/or protected fat was evaluated on the development and reproductive performance of beef heifers on temperate grassland
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