Effects of dietary level and withdrawal period of distillers dried grains with solubles on pork belly fat iodine value

Abstract Text: There is concern over the potential negative effects of feeding corn distillers dried grains with solubles (DDGS) to growing-finishing pigs on fat composition and quality, particularly of the belly.  The objective of this study was to evaluate the effect of increasing dietary level of DDGS (8.8% crude fat) and of DDGS withdrawal period prior to harvest on belly fat iodine value (IV).  A RCBD was used with a 3 × 4 factorial arrangement of treatments: 1) DDGS inclusion levels 20, 40, and 60%; 2) DDGS withdrawal period 0, 3, 6, and 9 wk prior harvest.  A control (0% DDGS fed throughout the study) was included as a contrast treatment.  The study was carried out in a commercial facility using a total of 3,536 pigs housed in mixed-sex groups of 34 (8 pens/treatment); start and end BW were 23.4 ± 4.43 kg and 129.5 ± 12.04 kg, respectively.  At the end of the growth period, pigs were harvested at a commercial facility and a fat sample was taken from the anterior end of the belly from a randomly selected sample of half of the pigs in the pen (equal numbers barrows and gilts).  Iodine value was measured using near-infrared spectroscopy.  Increasing dietary DDGS inclusion level linearly increased (P < 0.001) belly fat IV (67.5, 71.2, 74.6, and 77.3 g/100 g, for 0, 20, 40, and 60% DDGS, respectively; SEM 0.43).  Withdrawing DDGS from the diet prior to harvest linearly reduced (P < 0.001) belly fat IV (77.9, 75.4, 73.1, and 70.6 g/100 g, for withdrawal periods of 0, 3, 6, and 9 wk, respectively; SEM 0.33).  Regression of belly fat IV on timing of DDGS withdrawal showed that the rate of decrease was greater (P < 0.001) for pigs previously fed the higher levels of DDGS (slopes of linear regression -0.45, -0.82, and -1.17 g/100g for the 20, 40, and 60% DDGS inclusion levels, respectively).  The results of this study suggest that the increase in belly fat IV from feeding DDGS can be mitigated by feeding diets without DDGS prior to harvest and that the extent of change in IV during the withdrawal period is influenced by the level of DDGS fed previously.

Keywords: Pigs, DDGS, Withdrawal, IV