Optimizing dietary fat supplementation to improve energy intake and growth performance of weaned piglets: a meta-analysis

Dietary fat supplementation is a common strategy to promote growth of weaned piglets, but its effects have been inconsistent. Furthermore, the fat requirement is currently lacking in the nutrient requirements of swine. Therefore, this meta-analysis aimed to (1) assess the effects of dietary fat supplementation on growth performance, nutrient digestibility, and blood biochemistry parameters of weaned piglets; and (2) determine the appropriate fat supplementation and standardized ileal digestible (SID) fat contents in diets. A total of 24 studies were included, and effect sizes were pooled using a random-effects model, presented as standardized mean differences between fat-supplemented and un-supplemented treatments. Results indicated that fat supplementation increased the average daily gain (ADG) on 15-28/35 days and 0-28/35 days, improved the average daily energy intake (ADEI) across all phases, and reduced the average daily feed intake (ADFI) on 0-14 days and the feed to gain (F/G) during all phases of weaned piglets ( P < 0.05). The apparent total tract digestibility (ATTD) of crude fat was significantly enhanced by dietary fat supplementation ( P < 0.05); it had no impact on ATTD of other nutrients ( P > 0.05). Furthermore, subgroup analysis revealed that fat supplementation exceeding 5% but not exceeding 10% significantly reduced the ADG ( P < 0.05), whereas supplementation not exceeding 5% significantly reduced ADFI ( P < 0.05) and increased the ATTD of dietary dry matter for weaned piglets ( P < 0.05). Plant oil supplementation improved growth performance, the ADEI, and the ATTD of crude fat and gross energy ( P < 0.05); the animal fat only reduced ADFI on 15-28/35 and 0-28/35 days ( P < 0.05). The appropriate fat supplementation and SID fat content in diets were 4.45% and 6.79% in 0-14 days, and 3.78% and 5.23% in 15-28/35 days, respectively. In conclusion, the appropriate fat supplementation (especially for the plant oil) in the diet can benefit growth performance, primarily by increasing the energy density. • Dietary fat supplementation improved growth performance for weaned piglets, primarily by increasing the energy utilization rather than broad nutrient digestibility. • Subgroup analysis indicated that fat supplementation at 0-5%, particularly from plant oils, was associated with more favorable growth performance in weaned piglets than higher inclusion levels (5-10%) or animal fats. • Dose-response analyses were conducted to determine the appropriate fat supplementation and standardized ileal digestible (SID) fat contents in diets.