# Do Protein Supplementation Levels Influence the Performance of Male Nellore Calves Under a Grazing System at Pre-Weaning?

## TL;DR

This study found that reducing protein in supplements for young Nellore calves does not harm their growth or health under grazing conditions.

## Contribution

The study shows that lower protein supplements can be used without negative effects on pre-weaning Nellore calves in tropical grazing systems.

## Key findings

- Reducing supplement protein from 300 to 150 g CP/kg DM did not affect calf performance or efficiency.
- Lower protein supplements did not impact forage intake, muscle fiber traits, or blood metabolic markers.
- High-protein supplements increased CP intake and CP to DOM ratio compared to low-protein supplements.

## Abstract

Many studies with beef calves in tropical conditions report increased performance in response to increasing the protein level in the supplement. However, evaluating the use of supplements with an adequate protein proportion and ideal supplementation period for Nellore calves in the tropical grasses can allow establishing supplementation strategies that optimize animal performance and improve bioeconomic efficiency. This study measured the effect of different protein levels in the supplement on male Nellore calves at pre-weaning. Our results showed that decreased protein levels in the supplement, from 300 to 150 g CP/kg DM, do not detrimentally affect performance and efficiency of grazing male Nellore calves.

This study aimed to evaluate the effects of sequential supplementation with different crude protein levels and periods on performance, nutritional and metabolic characteristics, and efficiency of nitrogenous compounds use in grazing male Nellore calves at pre-weaning. Fifty male Nellore calves during pre-weaning were distributed in a completely randomized design in a 2 × 2 factorial arrangement. The strategies were as follows: Supplementation period in the initial pre-weaning was 1–78th experimental day and in the final pre-weaning was 79–156th experimental day. The Low and high protein levels in the supplement were 150 g CP/kg) and 300 g CP/kg, respectively. All animals received 6 g/kg BW of supplement. Protein levels in the supplement did not affect intake of forage DM, and neutral detergent fiber in the animals. However, a higher CP intake and the CP to DOM ratio (p-value < 0.05) was evidence for the high calves compared with low calves. Supplementation strategies did not affect the blood concentrations of IGF-1, glucose, and total protein. Likewise, protein levels in the supplement did not affect the ADG and number and diameter of muscle fibers. In conclusion, the decrease in protein levels in the supplement from 300 to 150 g CP/kg DM does not detrimentally affect performance and nutritional and metabolic characteristics in male beef calves under a grazing system at pre-weaning.