322 The Influence of Previous Plane of Nutrition on Grain or Grass-fed Finished Steers: Water-Related Gene Expression in the Kidney

Abstract

Abstract The extenuating stressors inherent to various beef cattle backgrounding systems in the U. S. may imprint different nutritional carryover effects of earlier stages of life onto the finishing phase. Therefore, the objective of this study was to evaluate the effects of previous plane of nutrition (PPN) onto water-related gene expression in the kidney of grain or grass finished steers. Twenty-four crossbred Angus steers were randomly distributed into either low or adequate PPN during the background phase. After 85d of backgrounding, animals were moved onto a 105-d finishing phase blocked by their PPN. The grass-finished group received only alfalfa hay, whereas the grain-finished group received a high grain diet (80% whole corn and 20% alfalfa hay). By the end of the finishing phase, animals were harvested and kidney samples were collected. Changes in gene expression of Aquaporins (AQP) -2, -3, -4, -7, ATP1A1, ATP1B1, SGK1, and CLIC1 from kidney tissue were assayed via real-time qPCR; and the 18S rRNA was used as an endogenous control. One-way ANOVA followed by Tukey post hoc analysis were conducted. When comparing grain versus grass-finished according to their PPN, ATP1B1 (P = 0.0290) was the only gene significantly different, with animals coming from a low PPN finished on grass having greater expression than for the grain-finished. However, within animals backgrounded at a low PPN, AQP3 (P = 0.0289), AQP7 (P = 0.0260), ATP1B1 (P = 0.0239), and SGK1 (P = 0.0411) were upregulated for the grass-finished animals. No differences were found for the other genes analyzed. These results suggest that PPN can impact water-related gene expression in the kidney of finishing steers; the greatest impact for water-related gene expression occurred in animals from a low PPN that were fed different finishing systems, where grass-fed animals had a greater gene expression compared with grain-fed animals.