82 Effect of feeding Mesquite (Prosopis spp.) pods on productive performance and methane emissions in small ruminants: a systematic review and meta-analysis

Application: Mesquite pods are an alternative feed to provide energy and protein to small ruminants in arid regions.Introduction: Small ruminant producers in arid regions use mesquite pods to provide their herds with a low-cost source of energy and protein and improve production parameters. This legume is a good source of protein, fiber, and sugars, which makes it a good ingredient for nutrition [2]. Furthermore, mesquite pods are rich in secondary bioactive substances such as alkaloids, flavonoids, terpenes and phenolic compounds [1]. Results of studies that assess effects of mesquite pods inclusion on ruminant rations has been inconsistent. The aim of this study was to carry out an analytical review to quantify the effect of the inclusion of mesquite pods on productive performance and methane (CH4) emissions of small ruminants.Materials and methods: A compressive and structured search of articles was performed using the following electronic databases: Google Scholar, Primo (UAEH), PubMed, Science Direct and ISI Web of Knowledge. The final database includes 37 studies with the following response variables: dry matter intake (DMI), average daily gain (ADG), feed conversion rate (FCR), digestibility (g/100 g DM) and CH4. To explore heterogeneity, a meta-regression analysis was performed, including the following a priori selected explanatory variables: dosage, species (goat and sheep), breed, body weight and processing of mesquite pods (ground, chopped, extract and meal). All analyses were performed in the R environment for statistical computing using the ‘meta’ package [3].Results: Inclusion of mesquite pods in small ruminant rations had a positive effect on ADG (+9.94 g/d), digestibility (1.45 g/100 g DM), FCR (-21.2 g/g) and DMI (+68.57 g/d)(Figure 1). The heterogeneity was substantial to all variables (>80.4), however, this was reduced when the explanatory variables were added to mixed-effect model. An increase of CH4 emission was observed to mesquite group (+0.57 g/d), likely associated with better DMI and digestibility of supplemented animals. There was a positive relationship between level of incorporation of mesquite pods and DMI, ADG and CH4 response. The largest effect size to DMI in response to mesquite supplementation was observed to meal processing following by ground and extract (Figure 2).