Performance and nutritional requirements of growing Nellore heifers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior This work was developed based on three experiments conducted aiming to evaluate animal performance and determine the nutritional requirements of growth in Nellore female cattle. The first two experiments aimed evaluate the dry matter intake (DMI) and nutrients, average daily gain (ADG), feed efficiency (FE), diet digestibility, microbial efficiency and cold carcass yield (CCY) and primal cuts (PC) of young Nellore heifers receiving two levels of concentrate. Nineteen heifers with initial average weight of 165.6±29.8 kg were used. Three animals were used in a trial to determine the digestibility and microbial efficiency of the two levels of concentrate diet (22.5 and 45%) and also including treatment with a restricted intake maintenance level. The remaining 16 heifers were confined for 168 days for evaluation of performance and intake, divided into two levels of concentrate, being 22.5 and 45% concentrate diet. Every 42 days, four animals, two from each level of concentrate, were slaughtered to determine carcass characteristics, making a factorial arrangement 2 × 4. The digestibility and microbial efficiency were not affected (P>0.05) by concentrate level and not by the level of intake, ad libitum or restricted. Heifers fed 45% concentrate diet had greater ADG (P0.05) between levels of concentrate. ADG (kg / day), DMI (% body weight/day) and EA were higher (P0,05) pelo nível de concentrado na dieta e nem pelo nível de consumo, ad libitum ou restrito. Novilhas recebendo 45% de concentrado na dieta apresentaram maior GMD (P0,05) entre os dois tratamentos. O GMD (kg/dia), CMS (% do peso corporal/dia) e EA foram maiores (P