PS2-19. Early Weaning Calves with Self-feeding Diets Including r-zeta® Additive.

Abstract Feeding programs for early weaned calves must ensure adequate feed intake immediately after being separated from their dams and must prevent overfeeding in the following weeks. The objective of this study was to evaluate the performance of early weaned calves with self-feeding of a balanced ration with the additive r-zeta® (Zorion US LLC) to manage feed intake. The additive r-zeta® is a commercial formulation that acts on intake regulation, has modulators of the intestinal flora, enzymes that improve the degradation of food, liver protectors and gastrointestinal anti-inflammatories. A total of fifty-four Hereford calves (81.9 ± 17.1 kg live weight -LW- and 77.2 ± 18.3 days old) from the INTA Concepción del Uruguay Experimental Station were weaned. The animals were randomly allocated in two groups based on their diet (3 pens/group, 9 calves/pen) for 56 days. In the Control group, the animals received a weaning protocol with increasing levels of a balanced pellet and in the r-zeta® treatment, animals were fed with a balanced pellet with the additive offered ad libitum, without fiber, from day one. Both diet types had 18.0% crude protein (CP) and 2.8 metabolizable energy -EM-/kg dry matter (DM). The Control diet was provided daily in the morning in linear feeders at increasing levels to ensure feed availability after 24 hours. In the r-zeta® treatment, the self-feeder was refilled every 3–4 days. All animals were weighed individually every 14 days to estimate average daily gain (ADG, kg/head/day) and total kg gain (TKG). The remaining feed was weighed daily in the control groups and every 3–4 days in the r-zeta® groups. Dry matter intake (kg DM/head/day and as a % of body weight) and feed conversion ratio (kg DMI/kg LW) were estimated. Statistical analysis was performed using Infostat software (Tukey's test, α = 0.05). The animal performance results are presented in Table 1. No differences were detected for final LW, ADG or TKG. However, feed intake was lower in calves weaned with the r-zeta® diet. Therefore, those animals presented better ratio conversion (p = 0.0383). In early weaning with adaptation protocols to high-concentrate diets, intake could be abrupt when postweaning stress decreases and hunger is excessive. Thus, animals with permanent quality food availability from day one are free from digestive risks due to the regulation intake provided by the additive. They can access the self-feeder whenever they are hungry, encouraging natural, frequent and small-meal behavior. The use of balanced feed with the additive allowed for early weaning without the need for fiber or daily feeding protocols. Further research is required to assess whether r-zeta® additive can be used in beef calves at first month of age and to discover long term growth impacts. For image description, please refer to the figure legend and surrounding text.