The Impact of Duration of Feeding and Saturation of Dietary Fats on Changes in Body Fat Over Time and on Final Carcass Lipid Iodine Values
The inclusion of unsaturated fats in pig diets has raised issues related to pork carcass lipid quality. The objective of this experiment was to understand how withdrawal from the diet of unsaturated dietary fat prior to slaughter impacts the composition of jowl fat during the finishing period and at market. Fifty pigs (PIC 337 X C22/29; initial BW = 59.3±3.64 kg), were allotted to an 82d experiment based on sex and initial BW to 10 treatments: 3 dietary fat withdrawal times prior to slaughter (21, 42 or 63d) by 3 fat sources ( 5% animal-vegetable blend (AV; iodine value (IV)=90.7), 2.5% corn oil (2.5%CO; IV=122.7), 5% corn oil (5%CO), plus a control diet with no added fat (CNTR) fed throughout the duration of trial. Pigs were individually housed to measure ADFI and dietary fat intake. Pigs were weighed and jowl adipose samples were collected on days 0, 21, 42, 63 and at harvest on d82. Carcass measurements were recorded at harvest using a durometer compression measurement (1 least firm; 100 most firm). Data were analyzed using PROCMIXED with treatment and sex as fixed effects, and pen as a random effect. Carcass IV (CIV) was affected by dietary fat inclusion duration across all lipid source treatments (P<0.01). Dietary fat source affected firmness measured bydurometer (CNTR=36, 2.5%CO=39, AV=40, 5%CO=31; P<0.05). Sex did not affect CIV (P>0.30) or firmness (P>0.13). Duration of lipid inclusion did improve gain to feed (CNTR=0.31 kg, 21d=0.31 kg, 42d=0.33 kg, 63d=0.34 kg; P<0.001). In conclusion, 2.5% CO and 5% AV maintained CIV below 74 g/100g, while a 21d withdrawal of 5% corn oil was required to maintain CIV below 74 g/100g.