Measuring the feeding behavior of lactating dairy cows in early to peak lactation.

The objectives of this study were to: 1) objectively define meal criteria (minimum interval between meals) of free-stall housed cows fed via a feed alley, 2) determine which measures of feeding behavior were most repeatable, and 3) describe changes in the feeding behavior from early to peak lactation. An electronic monitoring system was used to record individual cow presence (hits; 6-s resolution) at the feed alley for 21 lactating cows for three 8-d periods: period 1, 35 +/- 16 (mean +/- SD), period 2, 57 +/- 16, and period 3, 94 +/- 16 DIM. A mixture distribution model was used to calculate the meal criterion (27.74 min) by fitting the log10 frequency distribution of the intervals between hits. The within-cow repeatability was highest for feeding activity (hits d(-1)) and intensity (hits per meal min), moderate for total daily mealtime (min d(-1)) and meal duration (min meal(-1)), and lowest for meal frequency (meals d(-1)). From periods 1 to 2, all cows showed increases in total daily mealtime, meal frequency, and meal duration; however, cows with lower meal frequencies and feeding intensity in period 1 showed the greatest increases. Cows with high feeding activity and intensity during period 2 showed proportionally greater increases during period 3. These results illustrate that some measures of feeding behavior are highly repeatable within cows, but variable between cows and across stages of lactation. Thus, tests of treatment effects on feeding behavior should be within cow and control for days in milk.