Dietary effects on selenite toxicity in the chick

Area of Science:

• Animal Nutrition
• Toxicology
• Biochemistry

Background:

• Selenium (Se) is an essential trace element, but its toxicity (selenosis) can occur at elevated levels.
• Dietary composition significantly influences selenium toxicity and metabolism.
• Yeast-based diets are common in animal feed, but their impact on selenium toxicity varies.

Purpose of the Study:

• To investigate the comparative toxicity of sodium selenite (Na2SeO3) in diets based on torula yeast (TY), brewers' yeast (BY), and corn-soy (CS).
• To evaluate the protective effects of TY against Na2SeO3 toxicity in broiler chicks.
• To identify potential mechanisms behind the observed protective effects of TY.

Main Methods:

• Chicks were fed diets containing 50 or 75 ppm Se as Na2SeO3 with TY, BY, or CS base.
• Mortality, feed consumption, weight gain, liver Se accumulation, and liver histopathology were assessed.
• Partial or total replacement of TY with BY was also investigated.

Main Results:

• Chick mortality from Na2SeO3 was significantly lower in TY diets compared to BY or CS diets.
• TY diets mitigated the negative effects of Se on feed intake and weight gain.
• Chicks fed Se in TY diets showed lower liver Se accumulation and less severe fatty liver changes compared to those fed BY diets.
• Replacing TY with BY increased mortality due to Se toxicity.
• The ash fraction of TY demonstrated some protective effect against Se toxicity.

Conclusions:

• Torula yeast (TY) confers significant protection against sodium selenite (Na2SeO3) toxicity in broiler chicks.
• The protective effect of TY may be partly attributed to its mineral content, as indicated by the ash fraction's efficacy.
• Dietary yeast source critically influences selenium toxicity, with TY being superior to BY in mitigating adverse effects.