Effects of different additives on cattle feed intake and performance - a systematic review and meta-analysis

In the last few years, there has been a growing interest in the use of natural feed additives in animal feed. These can be used as replacements for antibiotics, to alter rumen fermentation and increase feed efficiency in ruminants. Therefore, the objective of this study is to evaluate the effects of adding different feed additives in the diet of beef and dairy cattle on their performance, dry matter intake (DMI) and feed efficiency, through a systematic review followed by meta-analysis. The systematic review suggested 43 peer-reviewed publications, according to the pre-established criteria. In beef cattle, the ionophore antibiotics reduced the DMI, improved the feed efficiency without interfering in the average daily gain (ADG). Non-ionophore antibiotics and propolis extract increased the ADG. In dairy cattle, the ionophores, yeast-based additives, and enzyme additives increased the feed efficiency, DMI, and daily milk production (MY), respectively. Essential oil supplementation in beef and dairy cattle had no effect on the feed intake and animal performance. The systematic review and meta-analysis allowed us to conclude that different feed additives have different effects on cattle performance, however, our results suggest that there are a few gaps regarding their effects on animal performance.