Feed Intake Patterns and Associated Blood Glucose, Free Fatty Acid and Insulin Changes in Ponies

Abstract

The feeding patterns of five pony geldings fed pelleted diets ad libitum were quantified for five 24-hr periods. Eighty percent of a given pony's total daily intake (6.3 ± .81 kg or 2.9 ± .41% BW) was eaten in 10 ± .9 separate meals. Each meal averaged .49 ±.13 kg of pellets and lasted 44 ± 10 minutes. The mean intermeal interval was 84 ± 10 min, with a maximum of 3 hour. The animals spent 38 ± 7.2% of a 24-hr period engaged in eating activities, 84 ± 3.7% of which was devoted to meals, the other 16% spent in nibbling activities. Forty-nine percent of the total daily intake was consumed between 0800 and 1700 hours. Fewer (P<.01), smaller (P<.05) and less frequent (P<.01) meals were observed between 1700 and 0800 hour. Wood chewing was observed only in the course of aggressive interactions between ponies. The ponies were placed on a feeding schedule that mimicked their normal ad libitum feeding patterns. Venous blood samples were drawn 1) after 1 hr of feeding; 2) after a subsequent 3-hr fast; 3) at the end of a second meal after the fast. Plasma glucose dropped from a satiety level of 111.4 ± 7.1 mg/100 ml to 87.5 ± 4.9 mg/100 ml after the 3-hr fast (P<.05) and had risen to the previous satiety level (104.6 ± 13.4, P<.005) at the end of the subsequent meal. Immunoreactive Insulin (IRI) dropped from 85.2 ± 43 µU/ml t0 52.4 ± 43 (P<.005) during the fast and rose to 91.4 ± 48 (P<.05) after the second meal. Plasma free fatty acids (FFA) did not change significantly from the first satiated state (.187 ± .04 meq/ml) to the normal hunger state (.196 ± .03 meq/ml) or at the second satiated state (.184 ± .05 meq/ml). There were interpony variations (P<.01) in the plasma IRI at all three sampling times. The plasma glucose level at normal hunger was negatively correlated (P<.01) with the subsequent meal size and rate of eating. It is postulated that plasma glucose levels may play a role in the control of feed intake in ponies.