Abstract
This study was performed to identify the ideal amount of concentrate required for a diet based on cactus cladodes, sugarcane, and urea used to feed heifers. Twenty Girolando heifers (160 +/- 8.39 kg) were randomly distributed into four experimental treatments with 0, 0.40, 0.80, or 1.20 kg day(-1) of concentrate. The basal diet contained [on dry matter (DM) basis] 38.1% sugarcane, 56.5% cactus cladodes [Opuntia stricta (Haw). Haw], 0.5% common salt, 1.1% mineral mixture, and 3.8% urea plus ammonium sulfate. The concentrate contained [on DM basis] 87% corn meal and 13% soybean meal. The basal diet and the concentrate were formulated to provide 13% crude protein (CP). The intake of DM (4.34-4.96 kg day(-1)), organic matter (3.96-4.98 kg day(-1)), CP (0.57-0.64 kg day(-1)), non-fibrous carbohydrates (2.20-2.61 kg day(-1)), and metabolizable energy (10.3-12.4 Mcal day(-1)) increased linearly with concentrate amount. Final body weight (196-224 kg), total body weight gain (36.9-61.2 kg), and average daily body weight gain (0.51-0.85 kg day(-1)) increased linearly with concentrate amount. The nitrogen balance was positive and increased linearly (54.8-62.3 g day(-1)) with concentrate amount. Based on the data, we recommend supplying six-monthold Girolando heifers (160 kg body weight) 1.20 kg concentrate day(-1) added to a diet based on sugarcane and cactus cladodes plus urea for better productive and economic performance.
Highlights
Heifer rearing provides high-quality genetic material to replace older cows from the herd
We recommend supplying six-monthold Girolando heifers (160 kg body weight) 1.20 kg concentrate day−1 added to a diet based on sugarcane and cactus cladodes plus urea for better productive and economic performance
Concentrate addition did not influence the digestibility of any nutrients (Table 3)
Summary
Heifer rearing provides high-quality genetic material to replace older cows from the herd. The age at first calving depends on the heifers’ feeding and rearing program. The age at first calving should occur at 24 months of age with 85% of adult body weight (BW). The key point for reducing the age at first calving is weight gain from birth to mating. This factor is related to management, feeding, and sanitary conditions. The age at first calving in Brazil is 34 months (Facó et al, 2005; Canazacayo et al, 2018). Analyses of economic indicators of milk production systems in tropical conditions
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