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Vitamin E and turkey poults

As researchers learn more about the importance of a strong antioxidant status in maintaining health and performance, they are taking a closer look at the low tissue concentrations of vitamin E found in turkey poults during the critical first few weeks after hatching.

Over the past few years, Iowa State University researchers have documented that poults' tissue levels of vitamin E drop precipitously within a week after hatching. According to a recent study (Applegate and Sell, 1996), dietary vitamin E supplementation can markedly reduce this decline.

This study included feeding supplemental vitamin E at the rate of 150 IU/kg (136,079 IU /ton) of the diet to poults from day one through day 22; control birds received no vitamin E supplementation. As in the previous experiments, plasma levels of vitamin E in the control birds fell dramatically from day one through day seven--from 17.77 to 3.18 µg/mL. They continued to drop through the rest of the three-week study and were only 0.97 µg/mL on day 22. Liver concentrations showed an even greater decline, falling from 172.2 µg/g on day one to 2.52 µg/g on day 22.

In vitamin E supplemented poults, however, declines in liver and plasma vitamin E concentrations were significantly less severe. Furthermore, plasma concentrations of vitamin E first stabilized and then rose by days 13 and 22. At the end of the study, plasma concentrations were 16.22 µg/mL, close to the 17.77 µg/mL at hatching. Liver concentrations of vitamin E continued to decline in supplemented poults through day 13, but then stabilized. Furthermore, at 14.92 µg/g on day 22, they were almost six times greater than in the controls.

The importance of these differences became clear when the researchers subjected liver and red blood cells to an in vitro oxidative assault (Table 1). On day one, red blood cells from both control and supplemented poults were resistant to hemolysis even when a relatively high concentration of the inducing agent was used; only 4 percent of the cells were destroyed. The researchers note that this resistance was probably due in large part to a high concentration of vitamin E in red blood cells that parallels high concentrations in the plasma.

 
Table 1

On day seven, with vitamin E levels low for both treatment groups, hemolysis was 80 percent for controls and 72 percent for supplemented poults. As plasma levels of vitamin E in supplemented birds stabilized and then rose, however, hemolysis was significantly less than in the controls. On days 13 and 22, hemolysis in controls remained at 80 and 100 percent, respectively, but fell to 10 and then 9 percent in supplemented birds.

Liver susceptibility to oxidative damage showed similar differences by treatment. As in research on meat quality, oxidation was measured by TBARS (thiobarbituric acid reactive substances); the concentration increases with peroxidation. TBARS levels were identical for the two treatments one day after hatching, but by day 13 had shown a marked divergence. On day 22, they were 20.3 percent higher than at hatching for the controls but 8.7 percent lower than at hatching for supplemented poults.

The researchers note that these results correspond with earlier research, such as Soto-Salanova  et al. (1993), which showed that tissue concentrations of vitamin E were severely decreased by five days after hatch. In that study, 100 IU of vitamin E/kg (90,719 IU/ton) of diet partly prevented the decline in liver and plasma concentration. These results are further supported by Fuhrmann  et al. (1994), who reported that red blood cells of chicks were susceptible to hemolysis unless at least 22 IU/kg (19,958 IU/ton) of diet were fed.

It is also important to note the sequence of metabolic decline caused by low levels of vitamin E. Applegate and Sell point out that research dating back to the late 1970s (Brownlee  et al. 1977) has indicated that lipid oxidation and hemolysis are concurrent, rather than consecutive, events in red blood cells. The long-term effects of vitamin E supplementation remain to be determined. However, field research and a number of other studies have also found improved live performance and meat quality with vitamin E supplementation.

 

References:

  • Applegate, T.J., and J.L. Sell. 1996. Effect of dietary linoleic and linolenic acid ratio and vitamin E supplementation on vitamin E status of poults. Poultry Sci. 75:881.
  • Brownlee, N.R., et al. 1977. Role of vitamin E in glutathione-induced oxidant stress: methemoglobin, lipid peroxidation and hemolysis. J. Lipid Res. 18:635.
  • Fuhrmann, H.S., et al. 1994. Bioefficiency of different tocopherols in chicken as assessed by haemolysis test and microsomal pentane production. Br. J. Nutrition. 71:605.
  • Soto-Salanova, M.F., et al. 1993. Research note: vitamin E status of poults as influenced by different dietary vitamin E sources, a bile salt and an antioxidant. Poultry Sci. 72:1184.

 
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