36 Effects of grinding method on ileal digestibility of amino acids in different short-season corn cultivars fed to growing pigs

Decreased corn production was previously observed in Manitoba due to the low climatic temperatures; however, corn production has increased by developing corn hybrids that require low corn heat units, and therefore can grow in areas with decreased heat units. Milling technology affects feed particle size and shape, which may affect the digestibility of nutrients and growth performance of pigs. Therefore, this study aimed to determine the effects of grinding methods on the apparent (AID) and standardized (SID) ileal digestibility of amino acids (AA) in selected short-season corn cultivars fed to growing pigs. A total of 18 ileal cannulated barrows (56.8 ± 2.9 kg) were assigned to 1 of 6 dietary treatments in a triplicate 6 × 2 incomplete Latin square design with 6 diets and 2 periods to give 6 observations per treatment. Dietary treatments were arranged in a 3 × 2 factorial design with three different corn cultivars [two Manitoba-origin short-season corns (A or B) or a US-origin corn] and two grinding methods [hammer mill or roller mill]. Each ingredient was included as the sole source of protein in the diets. All diets contained 0.3% titanium dioxide as an indigestible marker. Each experimental period lasted 7 d including the first 5 d for adaptation and the last 2 d for ileal digesta collection. After feeding the experimental diets, all pigs were fed a low-protein diet for 7 d to quantify endogenous losses of N and AA for determining the SID of N and AA. Pigs were fed the diets at 2.8 times the maintenance energy requirement based on their body weight at the beginning of each period. Data were analyzed using the PROC MIXED of SAS. The statistical model included diet as fixed effect and replication, animal within replication, and period within replication as random effects. The AID of Arg, Ala, Ser, and Gly were greater (P < 0.05) in short-season corn B compared with US-origin corn. The AID and SID of His in both short-season corns were greater (P < 0.05) than in US-origin corn. The AID of His and SID of Thr in hammer-milled corns were greater (P < 0.05) than in roller-milled corns. A significant interaction was found whereby AID of Ile in hammer-milled corn was not different between short-season corn B cultivar and US-origin corn but in roller-milled corn, short-season corn B cultivar had a greater (P < 0.05) digestibility than US corn. In conclusion, the digestibility of AA was greater in short-season corn than in US corn, and pigs had greater digestibili