Date of Award
Master of Science
Peter M Hoffman
Data from a 5-year study was used to look at the effects of housing (shelter or no shelter), diet (high moisture corn grain or corn silage), maximal and minimal daily temperature, day of year (beginning with January 1st), dry matter intake (DMI), and body weight on water intake of steers. Steers were started on a particular ration four times per year coinciding with the start of each season. These steers were put into a feedlot with one of two housing treatments, one-half of the feedlots were sheltered (S) pens, and one-half were no shelter (NS) pens. Within housing one-half of the feedlots of cattle were fed high moisture corn grain (HMC) based diets and one-half were fed diets that were predominately whole plant corn silage (CS). Daily water recordings for each pen of cattle were used to calculate average daily water intake (DWI) per steer by subtracting each week's recording from the previous week's recording and dividing this difference first by the number of steers per pen and then by the number of days in a week. These data were used to produce four regression plots comparing average DWI of steers per feedlot within week with respect to average maximal weekly temperature (Tmax), average minimal weekly temperature (Tmin), the day of year, and average steer weight per pen. To examine this information in more detail, data were separated into groups based on whether the steers were provided S or NS and on whether the steers were fed principally HMC or CS diets. The average DWI for these groups were compared with respect to Tmax, Tmin, and day of year, but not for average steer live weight because this variable had a very small coefficient of determination in the overall data evaluation. This process created 12 new regression plots. Additionally, data was grouped into categories based on whether the steers were provided S or NS and on whether the steers were fed HMC or CS. These data were evaluated in the same manner as the previous data set, creating 12 additional regression plots, bringing the total to 28. It was concluded that Tmax is the best variable that can be used to predict water intake for steers with a R² value from a polynomial regression of 0.49, followed by Tmin with R²=0.41, day of year with R²=0.43, and live weight of steers with R²=0.05. The group of cattle that consumed water correlating best with Tmax, Tmin, and day of year was found to be the feedlot with grain-fed cattle not provided shelter, for which Tmax had an R² value of 0.73, Tmin an R² value of 0.64, and day of year an R² value of 0.62. From further data analysis with SAS (SAS Inst. Inc., Cary, NC) it was found that log water intake showed an increase as Tmax or DMI increased (P<0.01). The rate of increase in water intake was lower for CS diet for Tmax and DMI (P<0.01). Mean log water intake values were different between CS and HMC diets as well (P<0.01). However, the mean log water intake was not different between the S and NS, but the rate of increase in water intake with respect to increased temperature was higher for the cattle with NS (P<0.01). The Tmin was not included in the SAS analysis because of multicollinearity with Tmax. With the SAS program the following equation for predicting steer water intake was created in which Tmax = the maximal weekly temperature average in °F, DMI = amount of DMI in lb, housing = 0 if S and housing = 1 if NS, diet = 0 if HMC and 1 if CS. When using the appropriate estimates from the solution for fixed effects generated with SAS the following formula was created and can be used for predicting steer water intake as log(water intake) = 0.43750 + 0.43790*diet + 0.01528*Tmax + -0.00314*Tmax*diet + 0.01349*DMI + -0.00914*DMI*diet + 0.00162*Tmax*housing.
Cody James McDonald
McDonald, Cody James, "Factors that impact water intake of feedlot steers throughout the feedlot period" (2012). Graduate Theses and Dissertations. 12400.