Recombinant bovine somatotropin on heifer’s biometric measures, bodyweight, blood metabolites, and dry matter intake predictions

Abstract

This study aimed to determine the influence of sustained-release recombinant bovine somatotropin (rbST) injections on biometrics measures, bodyweight (BW), average BW gain, observed and predicted DM intake, accuracy of recent methods to estimate DM intake, blood metabolites, haematological profile and rectal temperature in dairy heifers. Thirty Holstein heifers (132 ± 27 kg BW and 6.2 ± 0.35 months of age) were used in a complete randomised design experiment. Heifers were assigned to treatments: (1) Control (CON), 250 mL of saline solution, or (2) rbST, 250 mg of sustained-release rbST every 15 days. Treatments were injected in the subcutaneous of ischiorectal fossa or subscapular region in a regular alternating manner (right and left side) every 15 days throughout a period of 90 days. Prediction of DM intake was calculated using either non-linear or linear models for heifers in tropical conditions. rbST injections increased the average values of thoracic perimeter, length, and rump width in heifers. rbST-treated heifers had higher average BW and BW gain than CON. Regardless of the model applied, both observed and predicted DM intake were higher for heifers rbST-treated in relation to CON. Non-linear model was accurate without significant bias. rbST injections elevated blood glucose and high-density lipoprotein cholesterol concentration in heifers. No differences were detected on haematological profile and rectal temperature of heifers. rbST injections every 15 days to growing heifers promoted animal performance by increasing biometrics measures and BW gain. In addition, non-linear model was accurate to predict DM intake of heifers.