PSX-27 - The impact of feeding young Nellore bulls with a low concentrate diet for different periods followed by a high concentrate diet on dry matter intake and performance

Abstract: In Brazil, it is common practice to feed young bulls a low-concentrate diet (LCD) after weaning, followed by a high-concentrate diet (HCD) during the finishing phase to optimize animal growth while reducing the cost of concentrated feed. By restricting the concentrate intake during the early phase, the animals can potentially adapt better to a high-energy diet during the finishing phase, leading to improved performance. Thus, the objective of this study was to evaluate the impact of different LCD feeding periods after weaning, followed by feeding a HCD, on dry matter intake (DMI), average daily gain (ADG), feed efficiency (G:F), and final body weight (BW) of young Nellore bulls. Thirty-two young Nellore bulls (average initial BW = 265 ± 5 kg; age = 7 ± 1 mo) were used in a completely randomized design into four groups (n = 8/group) and assigned to receive one of 4 treatments containing different periods of LCD. The LCD consisted of 800 g/kg of forage sorghum silage and 200 g/kg of concentrate, while the HCD contained 200 g/kg of corn silage and 800 g/kg of concentrate. The diets were formulated according to BR-CORTE (2016) to achieve ADG of 0.6 kg/day and 1.2 kg/day for the LCD and HCD, respectively. The experiment lasted 154 days (14 days for adaptation to the HCD). The LCD and HCD feeding periods respectively were: 0 and 140 (T0), 28 and 112 (T28), 56 and 84 (T56), and 84 and 56 (T84) days. All animals were fed ad libitum in an electronic feeder (INTERGADO®, Intergado Ltd., Contagem, MG, Brazil), and individual daily feed intake was recorded. The bulls were weighed at the beginning and the end of the LCD and HCD feeding periods after undergoing 16 h of fasting to measure BW and ADG of both periods. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) assuming the significance level of 0.05. There was no evidence that different LCD feeding periods impacted DMI (P= 0.99), ADG (P = 0.59), or G:F (P = 0.48) during the LCD feeding period. The DMI during the HCD feeding period of T0 did not differ from the others, the T28 was not significantly different from the T84, and the T56 treatment was higher than T28 and T84 (P < 0.05). No significant difference was found between the treatments for ADG (P=0.09) and G:F (P=0.98) during the HCD feeding period. The T0 had the highest final BW, while there was no difference between the T28 and T56 groups, and the T84 group had the lowest final BW(P < 0.01). Given that the final BW was higher for T0, it may be inferred that there are no benefits to using LCD feeding periods.