Effects of Fat Pre-Emulsification on the Growth Performance, Serum Biochemical Index, Digestive Enzyme Activities, Nutrient Utilization, and Standardized Ileal Digestibility of Amino Acids in Pekin Ducks Fed Diets with Different Fat Sources

SIMPLE SUMMARY: Emulsifiers, which can reduce fat chylomicrons and improve fat emulsification, are currently widely used in animal feed to increase the utilization of fats and improve animal growth performance. However, the traditional method of adding emulsifiers directly to feed has shown inconsistent effects on livestock and poultry. Moreover, China is the largest duck-producing country, and it can, therefore, be anticipated that many duck processing enterprises will produce a large amount of duck fat. However, there is no information about the effects of duck fat as a fat source for Pekin duck. Considering the increase in oil prices, this study was conducted to investigate the effects of fat pre-emulsification (preE), which is a new method to improve the utilization of dietary oil, on Pekin ducks fed diets with different fat sources. The obtained results revealed that fat preE contributed to the utilization of dietary nutrients, serum lipid metabolism, intestinal digestive enzyme activities, and liver health, thereby improving the growth performance of ducks; duck fat has higher bioavailability for ducks based on dietary ether extract (EE) utilization. ABSTRACT: This experiment was conducted to evaluate the effects of fat pre-emulsification on growth performance, the serum biochemical index, intestinal digestive enzyme activities, nutrient utilization, and the standardized ileal digestibility of amino acids (SIDAA) in Pekin ducks fed diets containing different fat sources. Three hundred and twenty healthy ten-day-old Pekin male ducks (409 ± 27 g) were assigned to a 2 × 2 factorial design and given one of two types of poultry fat (duck fat or a mixed type of fat composed of chicken fat and duck fat in a 1:1 ratio) that had been pre-emulsified or not. This resulted in four treatments of eight replicates, with each replicate having ten ducks. The results showed that fat pre-emulsification (preE) significantly increased (p < 0.05) body weight and body weight gain and decreased (p < 0.05) the feed-to-gain ratio, the liver index, the activity of aspartate aminotransferase (AST) and the concentration of total cholesterol (TC) in the serum. Fat preE also tended to decrease the activity of lipase (p = 0.07) and significantly reduced (p < 0.05) the activity of trypsin in the duodenum. The utilization of dietary dry matter, ether extract (EE), energy, and total phosphorus, as well as apparent metabolizable energy (AME) and the SID of serine (p = 0.090), were improved by fat preE. Duck fat markedly increased (p < 0.05) the serum TC concentration and the utilization of dietary EE; however, it also tended to decrease the serum triglyceride (TG) concentration (p = 0.09) and markedly decreased (p < 0.05) the activity of trypsin in the jejunum and duodenum. These results indicated that fat preE contributed to the utilization of dietary nutrients, serum lipid metabolism, intestinal digestive enzyme activities, and liver health, thereby improving the growth performance of ducks. Duck fat has higher bioavailability for ducks based on dietary EE utilization.