Short communication: effect of vitamins E and C on cortisol production by bovine adrenocortical cells in vitro.

The aim was to determine if vitamins E and C inhibit the release of cortisol from bovine adrenocortical cells when stimulated with ACTH in vitro. A factorial arrangement of treatments was used to culture bovine adrenocortical cells with different concentrations of vitamins E and C [(+)-α-tocopherol at 0, 2.3, and 16 µM and l-ascorbic acid at 0, 15, and 50 µM]. After 3 and 7 d of vitamin treatments, cell cultures were stimulated with ACTH (1 nM) for 24h and the culture medium extracted to measure cortisol released by the cells using HPLC with UV detection. Vitamin E, vitamin C, or their combination did not affect the amount of cortisol released by the adrenal cultures to the media. Cortisol released by the adrenal cultures ranged from 33.6±6.85 to 49.7±8.01 nmol per 10(7) cells. The modulation effect of vitamins E and C on the stress response does not take place at the cortex of the adrenal gland.

Finishing steers with diets based on corn, high-tannin sorghum, or a mix of both: feedlot performance, carcass characteristics, and beef sensory attributes.

The objective of this work was to compare feedlot performance, carcass characteristics, and beef sensory attributes from steers finished with diets based on corn, high-tannin sorghum (HTS), and a mix of both grains. Angus crossbred steers (n = 11 steers per treatment, initial BW = 404 +/- 18 kg) were finished on diets containing 765 g/kg of DM of corn, HTS, or a 1:1 mix of corn and HTS. Final BW (P < 0.01), ADG (P < 0.001), and G:F (P < 0.01) were reduced in steers fed HTS when compared with steers fed corn. Steers fed the mixed diet had greater G:F than the average between corn and HTS diets (P = 0.04), which indicated that mixing corn and HTS had positive associative effects. Estimated NE(m) of HTS was 1.91, and estimated NE(g) was 1.35 Mcal/kg of DM. Hot carcass weight (P < 0.01), trimmed carcass weight (P < 0.01), yield grade (P = 0.04), and 12th-rib fat thickness (P = 0.01) were less in steers fed HTS than in those fed corn. Estimated percentage of HCW as boneless, closely trimmed retail cuts was greater in steers fed HTS compared with those fed corn (P = 0.02) but, due to the decreased HCW, estimated amount of boneless, closely trimmed retail cuts was less in steers fed HTS than in those fed corn (P = 0.03). Steers fed HTS had greater pH on LM (P = 0.02) than steers fed corn, but the difference was small (5.42 +/- 0.02 vs. 5.36 +/- 0.02, respectively) and within the range of normal beef pH. Diet had no effect on Warner-Bratzler shear values (P > or = 0.72). Multivariate ANOVA indicated a difference in sensory attributes of beef from corn and HTS steers (Wilks' Lambda, P = 0.04). When evaluating each sensory attribute independently, panelists found beef from steers fed HTS to be less juicy (P < 0.01), less tender (P = 0.03), and more cooked (P < 0.01) than beef from animals fed corn. Data from this study indicated that by using a 1:1 mix of HTS and corn it is possible to finish steers to similar BW and carcass quality as by using a corn-based diet. Also, total replacement of corn by HTS in the diets produced lighter and leaner animals. Total replacement of corn by HTS in the finishing diet changed beef sensory attributes, reducing the perception of beef tenderness and juiciness by panelists but without changing instrumental tenderness.

Finishing steers with diets based on corn, high-tannin sorghum or a mix of both: Color and lipid oxidation in beef.

We tested the hypothesis that feeding high-tannin sorghum (HTS) to steers would produce beef more resistant to oxidative deterioration. We observed lower thiobarbituric acid-reactive substances (TBARS) in Gluteus medius of steers fed HTS before it was displayed (P=0.028), which could be explained by a reduced response to stress in these animals. While steers finished with corn and corn+HTS had elevated plasma cortisol at the end of the feeding period (P=0.047 and 0.093, respectively), animals fed HTS and corn+vitamin E did not. However, feeding HTS increased the rate of discoloration and TBARS accumulation after aerobic display of Longissimus lumborum and Gluteus medius. Diet did not affect the activity of oxidation-related enzymes and fatty acid composition of muscle. The accelerated rate of lipid oxidation during display of beef could be partially explained by a numerically lower concentration of tocopherols in the tissue.

Growth performance and muscle oxidation in rats fed increasing amounts of high-tannin sorghum.

Oxidative processes deteriorate the quality of meat products. High tannin sorghums (HTS) contain flavonoid oligomers known as proanthocyanidins or condensed tannins. These compounds act as anti-oxidants in vitro, but their effectiveness in vivo remains unclear. We tested the hypothesis that moderate amounts of dietary HTS could reduce markers of oxidation on muscle of rats without having detrimental effects in growth. We used 2 groups of 38 male Sprague Dawley rats at 5 and 13 wk of age each. Each age group was fed 4 diets in a completely randomized design. The younger group was fed the experimental diets for 10 wk (10W); whereas the older group was fed for 2 wk (2W). The diets were modified from the NIH-07 diet and contained HTS and corn at ratios of 0:50 (S0, control), 20:30 (S20), 35:15 (S35), and 50:0 (S50) as a percentage of the diet. Growth and the efficiency of gain were assessed periodically measuring BW, ADFI, ADG, and G:F. Oxidation in muscle was measured in fresh tissue and after 6 d of aerobic-refrigerated storage. Muscles evaluated were LM and soleus (SM). Fresh liver was also evaluated. Thiobarbituric acid-reactive substances (TBARS) and carbonyl content were used as markers of lipid and protein oxidation, respectively. No differences in BW, ADFI, ADG, and G:F were observed in 2W rats. Greater (P < 0.05) ADFI and ADG were observed in 10W-S35 group between d 1 and 7 and greater BW (P = 0.049) was observed in group 10W-S35 at d 70 compared with 10W-S0. No differences were observed between S0 and any HTS diet in G:F in 10W and 2W rats. No differences in TBARS or carbonyls were observed in liver. No differences in TBARS were observed in fresh and aged LM and SM. When LM samples were aged for 6 d, decreased carbonyl contents (P < 0.01) were observed in 10W-S35 and 10W-S50 diets compared with 10W-S0. Reductions in carbonyls were also observed in aged SM between 2W-S50 and 2W-S0 (P = 0.013). We concluded that inclusion of 35% HTS in the diet increased intake and growth rate of young, fast-growing rats without changing the efficiency of gain. Feeding HTS reduced markers of protein oxidation in rat muscle after 6 d of refrigerated storage. If similar results are observed in animals such as swine or cattle, the use of HTS as animal feed should be reassessed.