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Impact of the source and level of dietary fat on growth performance as well as apparent and true total tract digestibility of acid hydrolyzed ether extract in growing and finishing pig diets
The pig industry utilizes a variety of fat sources and levels in pig diet to increase dietary energy content. The objective of this experiment was to investigate the impact of fat source (FS) and fat level (FL) on rate and efficiency of gain and to determine the apparent (ATTD) and true total tract digestibility (TTTD) of acid hydrolyzed ether extract (AEE). In a 134 d experiment a total of 1,213 pigs (PIC 280 × PIC Camborough 42; PIC, Hendersonville, TN) with an initial BW of 32.0 ± 0.4 kg were randomly allotted to 1 of 6 treatments arranged as a 2 × 3 factorial: corn oil (CO; IV = 123.2) versus choice white grease (CWG; IV = 66.8) and fat levels of 2, 4 or 6%. Ten pens of ~20 pigs each were randomly assigned to each of the 6 treatments and provided with feed and water ad libitum. Titanium dioxide was included as an indigestible marker at 0.4%. Fecal samples were collected from multiple pigs directly on d 39 (~ 68 kg). These samples were then polled within pen for analysis. TTTD (%) of AEE was calculated via correcting ATTD of AEE for endogenous fat losses at 20 g of AEE/kg of dry matter intake. Data were analyzed via PROC MIXED with FS and FL as fixed effects, room as a random effect, and pen as the experimental unit. ADG was not affected by FS (mean = 0.917 kg/d; P = 0.928) or FL (P = 0.445). FS did not alter ADFI (mean = 2.53 kg/d; P = 0.429), or G:F (mean = 0.361; P = 0.120). Increasing FL tended to decrease ADFI (P = 0.094), and increased G:F (2% = 0.349, 4% = 0.360, 6% = 0.374 g/d; P < 0.001). Increasing CO elicited a greater response in terms of ATTD of AEE than CWG resulting in a FS × FL interaction (2% CO = 66.2, 4% CO = 74.9, 6% CO = 79.2, 2% CWG = 65.3, 4% CWG = 75.4, 6% CWG = 75.7%; P = 0.012). TTTD of AEE of CO-based diets (94.1%) tended to be higher than that of CWG-based diets (92.4%; P = 0.063), but was not affected by FL (mean = 93.4%; P = 0.954). In conclusion, increasing FL improved efficiency but not rate of gain. The TTTD of AEE tended to be higher in diets based on CO than CWG.
Keywords: fat digestibility, corn oil, choice white grease