341. Effects of Chromium Propionate Supplementation During Pre-conditioning and Receiving Programs on Performance of Feeder Cattle.

Abstract

This experiment evaluated the effects of chromium propionate supplementation during a 44-d preconditioning followed by a 56-d receiving program on the performance of feeder cattle. Eighty-two newly-weaned feeder calves originating from the same farm were unloaded to the feedlot facility on d − 1 and weighed on d − 1 and d 0. Calves were blocked by body weight (BW) and sex and allocated to 18 drylot pens in a randomized complete block design. Pens were assigned to receive 1) a total mixed ration (TMR) supplemented with 0.4 mg of Cr/kg DM (Cr; n = 41) or 2) a TMR without chromium propionate (CON; n = 41). Animals were fed once daily at 0800 h ad libitum, and SmartFeed units were used to measure individual dry matter intake (DMI). Feed samples were collected daily to determine TMR dry matter (DM) concentration and adjust supplement amounts. During the preconditioning phase, calves remained at the feedlot for 44 d. At the end of this period, calves were weighed on d 43 and d 44 to determine final BW. Calves were then transported on d 44 for 1,310 km over 18-h, with ambient temperatures estimated to range from 2 to 15 °C. After transportation, calves returned to the feedlot and were weighed on two consecutive days to determine initial BW for the receiving phase. Subsequently, calves were re-randomized across pens to simulate a new receiving environment while maintaining their respective dietary treatments. Final BW was determined as the average of BW measurements collected on d 99 and d 100. Average daily gain (ADG) was calculated as the difference between final and initial BW divided by the number of days between weighs for both phases. Feed efficiency (G:F) was calculated as the ratio of total BW gain to total DMI within each phase. Data were analyzed using the MIXED procedure of SAS, using animal as the experimental unit. As designed, initial BW was similar during the preconditioning phase (P = 0.90; Table 1). Dry matter intake was not affected by chromium propionate supplementation (P = 0.80). However, calves supplemented with chromium propionate had greater ADG (P < 0.05) and G:F (P < 0.05) compared with CON. Additionally, chromium-supplemented calves tended to have greater final BW (P = 0.06; Table 1). During the receiving phase, calves supplemented with chromium propionate also showed a tendency for greater initial BW compared with CON (P = 0.09; Table 2). However, chromium propionate supplementation did not affect DMI (P = 0.34), final BW (P = 0.20), ADG (P = 0.88), or G:F (P = 0.60). In summary, chromium propionate supplementation improved growth performance during the preconditioning phase. This improvement was reflected in a tendency for greater initial BW at the start of the receiving phase; however, no differences were observed in performance during the receiving period.

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