Defining the physical properties of corn grown under drought-stressed conditions and the associated energy and nutrient content for swine.

Abstract

Historically high temperatures and low rainfall during the 2012 growing season resulted in drought-stressed conditions in much of the U.S. corn belt. The objective of this experiment was to investigate the impact of these conditions on the composition and energy content in corn and determine if relationships exist among corn quality measurements, chemical composition, and digestibility of energy. Twenty-eight samples of corn from the 2012 drought-stressed crop (DS), plus 2 representative corn samples from the 2011 crop (CNTRL), were collected in Iowa and Illinois using yield as an initial screen for drought impact. Yields ranged from 2.5 to 14.8 t/ha. Each sample was graded by an official of the U.S. grain inspection agency and analyzed for 1,000 kernel weight, kernel density, ether extract, starch, GE, NDF, and CP content. Diets were formulated using each of the 30 corn samples and were fed at 2.6 times the estimated maintenance energy requirement according to the . Sixty individually housed barrows (PIC 359 × C29; 34.2 ± 0.2 kg initial BW) were randomly allotted in an incomplete crossover design to 30 diets across 4 periods. Diet and fecal samples were analyzed to determine DE values. Both ME and NE values were then calculated from DE values using methods developed by and , respectively. Mean DE, ME, and NE values between the CNTRL and DS were not different (3.72 vs. 3.68 Mcal/kg, respectively, 3.66 vs. 3.62 Mcal/kg, respectively, and 2.92 vs. 2.87 Mcal/kg, respectively; > 0.10). Comparing CNTRL with DS, there were no differences ( > 0.10) in ether extract (4.07 vs. 3.96%), CP (8.56 vs. 9.18%), or starch (70.5 vs. 69.5%). However, ADF and NDF were higher in the DS (2.23 and 8.19%, respectively) when compared with CNTRL (1.89 and 6.92%, respectively; < 0.001 and = 0.015, respectively). Small but significant correlations were observed between DE and NDF ( = -0.51, = 0.008), kernel density ( = 0.51, = 0.007), and percent damaged kernels ( = 0.41, = 0.031). No statistically significant correlations were observed between DE and starch or ADF content or between DE and test weight. We can conclude that corn grown in drought-stressed conditions has energy content similar to corn grown under more favorable conditions and, therefore, can be successfully used in swine diets. Furthermore, NDF proved to be superior to fat, starch, and ADF content in explaining the variation in corn energy content.