Zhi Li;Bocheng Xu;Zhaoqing Lu;Yizhen Wan

National Engineering Laboratory of Biological Feed Safety and Pollution Prevention and Control, Key Laboratory of Animal Nutrition and Feed of Ministry of Agriculture, Key Laboratory of Animal Nutrition and Feed Science of Zhejiang Province, Institute of Feed Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang Province, 310058, People's Republic of Chin;National Engineering Laboratory of Biological Feed Safety and Pollution Prevention and Control, Key Laboratory of Animal Nutrition and Feed of Ministry of Agriculture, Key Laboratory of Animal Nutrition and Feed Science of Zhejiang Province, Institute of Feed Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang Province, 310058, People's Republic of China

Energy density;Finisher pig;Grower pig;Growth performance;Long-chain fatty acid;Meta-analysis;Production performanc

Background Supplementation of feed with long-chain fatty acids (LCFAs) during the grower and finisher phases has long been discussed as a growth promotion strategy in pigs, but its effects are inconsistent. The purpose of our study was to comprehensively evaluate its effects on the growth performance based on the average daily gain (ADG), average daily feed intake (ADFI) and gain: feed (G:F) ratio and to unveil the roles of the basal diet, LCFA concentration and LCFA saturation. Results We searched the PubMed and Web of Science databases (articles published from Jan 1(st), 2000, to Sep 30(th), 2018; restricted to English) and compared LCFA-supplemented diets with control diets. We retrieved 2346 studies, 18 of which (1314 pigs, 26 records) were eligible for our analysis. We used a random-effects model to calculate the weighted mean differences (WMDs) and 95% confidence intervals (CIs). LCFA supplementation in the grower-finisher phase improved the ADG (WMD = 41.74 g/d, 95% CI: 8.81 to 74.66, P = 0.013) and G:F ratio (WMD = 0.019, 95% CI: 0.006 to 0.032, P = 0.003). For supplementation solely in the finisher phase, we found a similar performance in the ADG (WMD = 39.93 g/d, 95% CI: 26.48 to 53.38, P < 0.001) and G:F ratio (WMD = 0.019, 95% CI: 0.006 to 0.032, P < 0.001) but a reduction in the ADFI (WMD = - 83.863 g/d, 95% CI: - 156.157 to - 11.569, P = 0.023). Specifically, approximately 5% LCFA supplementation in the finisher phase had significant effects on the ADG (WMD = 51.385 g/d, 95% CI: 35.816 to 66.954, P < 0.001), ADFI (WMD = - 102.869 g/d, 95% CI: - 189.236 to - 16.502, P = 0.02) and G:F ratio (WMD = 0.028, 95% CI: 0.018 to 0.039, P < 0.001), whereas a concentration of approximately 1% exhibited no effects. Conclusions Overall, regardless of the basal diet and saturation, LCFA supplementation greatly improves the growth performance of grower and finisher pigs, primarily by increasing the energy density.