Training responses of two-year-old Quarter horses fed rapidly fermentable carbohydrates

Abstract

Two replicated experiments (Exp. 1: May 14 to June 8; Exp.2: June 25 to July 20) evaluated effects of feeding grain to 2-yr-old Quarter horses on behavior and physiological parameters during early stages of training. In each experiment, 6 different horses were allotted by sex and weight to 2 diets; hay only or hay plus 2.3 kg/d grain. Horses were group-housed with ad libitum access to grass/alfalfa hay and water, and were individually fed 1.15 kg grain or 40 g salt (placebo) at 0800 and 1600 for 7 d prior to and during training. The trainer was blind to diet assignments. Horses were trained 5 d/wk for 3 wk and scored (1 to 5) by the trainer daily on obedience (willingness to ride with a loose rein and little leg pressure), life (willingness to move at any desired speed), and direction (suppleness in the poll and loin), while an observer scored fearfulness. A heart monitor recorded minimum, maximum, and mean heart rate daily during training. Categorical data were transformed by subtracting the daily median as each horse's score was relative to the other horses on that day. Data were analyzed as repeated measures (Proc Mixed of SAS) with horse as the experimental unit. In Exp. 1 grain did not affect (P = 0.83) obedience, while horses fed grain in Exp. 2 were less obedient during training (P = 0.02) than those not receiving grain. Horses fed grain showed greater (P = 0.05) fearfulness than horses fed hay alone. Life:direction (ideal is 1.0, > 1.0 indicates high self-preservation) was higher (P = 0.04) in horses fed grain than in those fed hay alone (1.29 vs. 1.08, respectively). Maximum heart rate was not affected (P = 0.21) by grain, while mean heart rate was higher (P = 0.03) for horses fed grain than hay alone (126 vs. 119 beats/min, respectively). Horses fed grain during training exhibited more self-preservation behavior, increased mean heart rate, and an unbalanced life to direction ratio, which could inhibit training effectiveness.