Factors affecting sampling behavior of cattle are poorly understood. The objectives of this study were to measure the effects of variation in feed quality on the feeding behavior of Holstein dairy heifers.

Thirty-two heifers were housed in four groups of eight. Each group pen had eight distinct feeding stations. The total mixed ration (TMR) provided was low energy (TMR-L), moderate energy (TMR-M), or high energy (TMR-H).

During trial 1 (days 1 to 8), heifers were offered a uniform baseline diet (TMR-M in all eight feeding stations) interspaced with two uniform test diets on days 3 and 6 (TMR-L or TMR-H in all 8 feeding stations).

During trial 2 (days 9 to 17), heifers were offered a nonuniform baseline diet (seven feeding stations with TMR-L and one feeding station with TMR-H) interspaced with three uniform test diets on days 11, 14, and 17 (TMR-L, TMR-M, or TMR-H in all 8 feeding stations). Heifers were observed in pairs (n=16) for 15minutes following delivery of fresh feed.

Relative to the uniform baseline period of trial 1, 31 percent fewer switches occurred between feeding stations when offered TMR-H and 51 percent more switches when offered TMR-L.

Relative to the nonuniform baseline of trial 2, 49 percent fewer, 27 percent fewer and 25 percent more switches occurred during the TMR-H, TMR-M, and TMR-L treatments, respectively.

In general, when heifers were offered a diet that was lower in energy density than that previously experienced, they spent less time at each feeding station and when offered a higher energy diet, heifers spent more time at each feeding station. The greater the contrast in energy density between the test and baseline diets, the greater the change in the behavioral response. Competitive interactions at the feed bunk were most frequent when TMR quality varied among the eight feeding stations; during the nonuniform baseline period of trial 2, the number of competitive interactions was over 3.5 times higher than during all uniform dietary treatments.

In summary, dairy heifers sample feed quality by changing feeding locations at the feed bunk and this sampling behavior is affected by variation in diet quality along the feed bunk and across days.

Source: J.M. Huzzey, J.A. Fregonesi, M.A.G. von Keyserlingk, D.M. Weary/Journal of Dairy Science