VARIATION IN AND RELATIONSHIPS AMONG FEEDING, CHEWING AND DRINKING VARIABLES FOR LACTATING DAIRY-COWS

Twelve Holstein cows (63 DIM; 6 primiparous) were offered a common die t and monitored for 21 d (11 d of adaptation, 10 d of collection) with a data acquisition system to measure continuously feed and water inta kes and chewing behavior. Objectives were to examine relationships amo ng feeding behavior variables for noncompeting cows producing various quantities of milk and to determine experimental designs with adequate power to detect reasonable treatment differences in future experiment s. Coefficients of variation across cows ranged from 5 to 41 % for the variables studied. Milk production was correlated positively with DMI and water intake within and across parities. For multiparous cows, pr oduction was related positively to meal size (r = .78) and length of e ating bouts (r = .75) and unrelated to meal number and eating rate. Fo r primiparous cows, production tended to be related positively to meal number (r = .55) and eating rate (r = .87) and unrelated to meal size . Rumination and total time spent chewing per unit of DMI were correla ted negatively (r = -.58) with milk production within and across parit ies. These correlations suggest that differences exist among cows for chewing efficiency. Reasons why high producing cows consume and chew m ore effectively deserve further study. Contrast differences of 10% of means for variables examined had an 80% probability of detection with a Latin square design utilizing 12 cows monitored for 5 d.