| Popis: |
Operant conditioning procedures were used to assess preference for a standard dairy concentrate containing either 0, 9, 23, or 34% processed poultry excreta. Eight 8-mo-old Holstein heifers were trained to operate a two-choice feeder in an operant chamber. When heifers pressed the muzzle plate that activated the feeder mechanism, they had access to one of the paired feeds for 3s every 15s on an average. Heifer responses were recorded electronically during daily 20-min sessions. All concentrates were fed in the operant chamber. Between sessions daily and on weekends and holidays heifers received alfalfa hay for ad libitum consumption. Data from the last five sessions, when response had stabilized, were analyzed. An average of 21 sessions was required to reach stability for a choice comparison test, but this was highly variable for individuals and ranged from 9 to 44 sessions. Data from each heifer were corrected for any bias for the right or left side, based on a comparison of responses with control sessions. There were no differences among heifers in the number of choices made during the five sessions or in deviations from random responses (.5). The number of responses and homogeneity of response differed among heifers. Heifers preferred concentrate containing less processed poultry waste; ranking of preference was 0>9>23>34% processed poultry excreta. Heifers usually rejected concentrate containing 34% processed poultry excreta. |
