Interrelationships among voluntary intake, eating and ruminating behavior and ruminal motility of heifers fed corn silage

Six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) with ruminal, duodenal and ileal cannulae given ad libitum access to corn silage with or without 100 mg monensin X head-1 were used to determine interrelationships among behavior, ruminal motility and intake. Voluntary intake was positively related (P less than .001) to eating time, duration of the main morning meal and daily mastication time. Intake was negatively related to unitary times min X g dry matter-1 X (kg body weight X 75)-1] of eating (P less than .05), rumination (P less than .001), mastication (P less than .001), unitary number of rumination boli (P less than .001), and latency time between termination of morning meal and onset of rumination (P less than .05). Both daily and unitary eating and ruminating time were positively related (P less than .001) to daily and unitary mastication time and unitary number of strong cranio-dorsal ruminal contractions. Positive relationships (P less than .01) were found between mean duration of daily meals, main evening meal and unitary eating time, and between mean duration of rumination periods and unitary ruminating time. Daily and unitary number of rumination boli and mean duration of one bolus were positively related (P less than .01) to unitary ruminating time. Interrelationships between intake, eating and ruminating activities and associated cranio-dorsal ruminal motility were all influenced (P less than .01) by individual heifer, which indicates potential in identifying individuals with better than average mastication behavior and ruminal motility.(ABSTRACT TRUNCATED AT 250 WORDS)