Effect of Decreasing the Maize Content of Feed on Growth Performance, Rumen pH, and Blood Chemistry in Grain-Fed Holstein Bull Calves

The aim of the study was to evaluate the impact of replacing the maize portion of the diet on growth, rumen health and blood chemistry of Holstein bull calves. A maize plus protein supplement feed (MS), a MS plus corn distiller’s dried grain with soluble matter (DDGS) feed (MSD), a maize plus canola meal plus DDGS feed (MCD), a barley plus canola meal plus DDGS feed (BCD), and a hay grass negative control feed (N) were all given ad libitum. Three-month-old bull calves were assigned randomly to MS, MSD, MCD and BCD, 80 animals per treatment, 10 per pen. An additional group of five bull calves were assigned to N. Blood HCO3-, anion gap, urea, glucose, pH, PCO2,L-lactate and lipopolysaccharide binding protein were measured. Daily duration below pH 5.6 (DpH5.6)in the rumen was logged. A mixed linear model (Proc Mixed) was used for data collected over time from individual animals. Histology results and liver rejections were analysed using a chi-square test (Proc Freq), and linear regressions to evaluate the relationships between DpH5.6 and ADG.MSD and MCD produced similar growth but did not decrease DpH5.6 or affect blood parameters. BCD decreased DpH5.6 and improved gain at the finishing phase but did not affect blood parameters. Diets had no effect on rumen epithelium and lamina propria, or on the frequency of liver abscesses. Partial or total replacement of maize by DDGS, barley and canola meal appears not to affect livestock performance.