Meta-analysis of relationship between weaning age and daily weight gain of piglets in the farrowing and nursery phases

A systematic review of the literature was carried out to perform a meta-analysis to assess effects of age at weaning on the performance of piglets in the range of 14 to 42 days old. This step consisted in defining the databases and keywords to be employed in searching for papers for the meta-analysis. To that end, the databases Capes Publication Portal and Google Scholar were searched for researches published from 2001 to 2019. After the acceptance and exclusion criteria had been defined and applied, 28 papers were selected. The data were collected with Excel (R) software of Microsoft Office for later statistical analysis. Orthogonal polynomial contrasts were used and the linear and quadratic regression equations were fitted with hypotheses tested at the 5% significance level. The results confirmed the disadvantages of early weaning and the benefits of weaning at around 28 days old. In the farrowing phase, piglets weaned after 35 days had lower daily weight gain (DWG) (P =0.002) than those weaned at 27 days. The derivative of the regression of DWG while nursing on age revealed that a weaning age of 26.34 days yielded the maximum DWG among the ages assessed. After weaning, the maximum DWG was achieved by weaning piglets at 32.26 days. Given the performance of piglets in the farrowing and nursery phases, the results of this metaanalysis indicated the best weaning age was between 26 and 32 days.