PSIV-35 The relationship between weather variables and dry matter intake in beef steers

Abstract

Abstract The objective of this experiment was to examine the relationship between weather variables and dry matter intake (DMI) in beef steers. Daily intake data from 790 beef steers collected from years 2011 to 2017 using an Insentec feeding system were used for this experiment. Data were condensed from daily data into weekly averages (n = 13,895 steer-weeks). The variables considered for this experiment include DMI (2.50 to 23.60 kg/d), body weight (197.3 to 796.1 kg), dietary energy density (NEm; 0.793 to 2.970 Mcal/kg), absolute ambient temperature (-23.7 to 21.4 °C), minimum ambient temperature (-28.2 to 15.7 °C), maximum ambient temperature (-19.3 to 27.3 °C), range of temperature (2.8 to 19.4 °C), dew point (-27.8 to 14.3 °C), wind speed (2.08 to 6.49 km/h), solar radiation (30.8 to 297.1 W/m2), and two weeks lag (average of previous two weeks values) and monthly lag (average of previous four weeks values) of each weather variable listed. Residuals of DMI generated after fitting week of year as a fixed effect were used in scatter plots with explanatory variables to identify if non-linear relationships existed. Body weight and energy density had both linear and quadratic relationships with DMI, while the relationship with DMI for other variables were tested linearly. The MIXED procedure of SAS was used to assess the fit and regression parameters of explanatory variables as fixed covariates. Repeated measures were handled using the REPEATED statement and within-individual relationship was accounted for using the Toeplitz covariance structure. There were some interactions between weather variables. Important variables in our model and their interactions are shown in table 1. This study shows the important weather variables (Table 1) that affect DMI of beef steers and will help in improving the accuracy of DMI prediction equations.