Defining the energy and nutrient content of corn grown in drought-stressed conditions and determining the relationship between energy content of corn and the response of growing pigs to xylanase supplementatio

Two experiments were conducted to determine the effects of xylanase on apparent total tract-(ATTD) and apparent ileal digestibility (AID) in corn-based diets using higher and lower energy corn samples with pigs. The objective of these experiments was to determine if the efficacy of exogenous xylanases are increased in less digestible, as compared to more digestible, corn samples. First, corn samples of higher and lower digestible energy had to be identified. The 2012 drought-stressed growing conditions provided an opportunity to identify these samples. In experiment 1, 28 corn samples were selected from the 2012 crop, using yield as an initial screen for drought-stress, along with 2 samples from the 2011 crop to serve as controls. A total of 60 individually-housed barrows were randomly allotted to 1 of 30 diets, each containing 1 of the 30 corn samples, in a partial crossover design with 4 periods. Energy and nutrient content of corn grown in drought-stressed conditions (DS corn) was not different than what would have been expected in a typical year, but acid detergent fiber (ADF) and neutral detergent fiber (NDF) were higher in the DS corn than in the control corn (P < 0.02). Additionally, 2 corn samples of higher (HE) and 2 of lower (LE) digestible energy (3.74 and 3.75 Mcal DE/kg vs. 3.56 and 3.63 Mcal DE/kg) were identified in experiment 1 for use in a second experiment. In experiment 2, dietary treatments were arranged in a 2 x 2 factorial design: HE and LE corn samples, with and without xylanase supplementation; for a total of 8 dietary treatments. Sixteen individually-housed ileal-cannulated barrows were randomly allotted to 1 of the 8 diets in a 4-period partial crossover design. Mean ATTD and AID coefficients in the LE diets were not statistically different from the HE diets with the inclusion of exogenous xylanase (P > 0.10). However, there was an overall effect showing an increase in ATTD of GE and DM with xylanase supplementation (84.8 vs. 83.6% for GE, P = 0.008; and 84.2 and 83.0%, P =0.007). In conclusion, xylanase supplementation was not more effective in LE diets, as compared to HE diets, but there was an overall effect of enzyme increasing digestibility at the total tract level.