Management strategies to improve beef feedlot performance and assessment of nutrient composition of beef retail cuts.

摘要

Two experiments investigating the impact of: (1) feeding frequency and (2) feedbunk management on feedlot steer performance were conducted. In experiment 1, three treatments (N=270) were utilized: (1) offered 100% of their ration at 0800 hours (h), (2) offered 60% of their ration at 0730h and 40% of their ration at 1300h, and (3) offered 34% of their ration at 0700h, 33% of their ration at 1000h, and 33% of their ration at 1400h. Average daily gain (ADG) was similar for steers fed once or twice per day (1.63 and 1.64 +/- 0.02 kg/day, respectively). However, ADG, dry matter intake (DMI), hot carcass weight (HCW) and number of condemned livers were greater in steers fed three times per day compared to other treatments. In Exp. 2, 127 steers were utilized to investigate the impact of feedlot bunk scoring on steer DMI. Overall DMI was greater for steers that consistently received enough feed to ensure 2.27 to 9.05 kg of orts each morning. By allowing 2.27 to 9.05 kg of orts each morning daily DMI was increased which could result in increased performance and decreased days on feed.;The objective of the third experiment was to determine the impact of timing of anthelmintic administration relative to vaccination on antibody titer response to vaccine components and subsequent rectal temperature and antibody response to an Infectious Bovine Rhinotracheitis (IBR) challenge. Thirty-three individually-fed, colostrum deprived Holstein bull calves (initial BW of 131 +/- 4.2 kg) were utilized. On day 88 all calves were challenged with IBR and blood samples were obtained on day 0, 1, 3, 4, 6, 8, 10, and 12 post inoculation. Post IBR inoculation animals in all groups had elevated rectal temperatures. Control animals had greater rectal temperatures than DPV and DV on day 88, 89, and 97. These data suggested that deworming before or at vaccination decreases parasite burden and rectal temperature following an IBR challenge in animals.;Experiments 4 and 5 were focused on beef retail cut nutrient composition. The objective of the first study was to determine if cooking method and degree of doneness (DOD) affect nutrient composition of beef strip loin steaks. Seven steaks were obtained from each strip loin for a total of 147 steaks. Steaks within strip loin were randomly assigned to one of six treatments. Treatments consisted of: (1) pan fried (PF), 60°C; (2) PF, 71°C; (3) PF, 77°C; (4) grilled (GR), 60°C; (5) GR, 71°C; (6) GR, 77°C. Steaks were cooked fresh, immediately after fabrication. A set of raw steaks was used as a control group for nutrient analysis. Cooking method and temperature to which steaks are cooked play a major role in the nutrient composition of steaks and these factors should be accounted for when determining nutrient profiles of beef retail cuts.;Experiment 5 consisted of two separate experiments conducted to investigate factors that influence the nutrient composition of purge and cook drippings (CD). For experiment 1, twenty six chucks were Selected from carcasses based on QG (16 Choice and 10 Select), YG (11 YG 2 and 15 YG 3), and gender (12 heifer and 14 steer carcasses). Each cut was cooked based on consumer popularity. For experiment 2, strip loins were removed from the right sides of 21 low Choice steer carcasses and aged for 14 d. Seven steaks were obtained from each strip loin. Steaks (N = 147) were randomly assigned to treatment within strip loin. Treatments consisted of (1) Pan Fried, 60°C (2) Pan Fried, 71°C (3) Pan Fried, 77°C (4) Grilled, 60°C (5) Grilled, 71°C (6) Grilled, 77°C. A set of raw steaks was used as a control group for nutrient analysis. For both experiments, purge was collected from each cut immediately after package removal. In Exp. 1, cook drippings were collected into conical tubes immediately after cooking. Effects of YG and gender were minimal. Yield grade 2 cuts had greater (P 0.05) DM cook drippings than YG 3 cuts. Based on gender, heifers tended (P 0.10) to have lower DM cook drippings compared to steers. The DM content of purge differed (P 0.05) between roasts steaks, and braised cuts (10.30, 10.33, and 9.68 +/- 0.18). The Ash content of purge also differed (P 0.05) between roasts, steaks, and braised cuts (3.10, 2.66, and 3.50 +/- 0.19). Dry matter, ash, and crude protein of cook drippings were different (P 0.05) relative to type of cut. Results of this study indicated that type of cut, cooking method, and degree of doneness contributes to the overall nutrient composition of purge and cook drippings from retail cuts. (Abstract shortened by UMI.)