Effects of glycine and glutamic acid supplementation to low protein diets on performance, thyroid function and fat deposition in chickens

Abstract

Consumption of low crude protein (CP) diets causes elevation in fat accumulation in chickens, and this effect is independent of dietary essential amino acid levels. Thyroid hormones, because of their metabolic regulatory characteristics, might be an effective factor in lipogenesis. Therefore, a study was conducted to investigate the influence of low CP diets on hormonal function of the thyroid. Two hundred and sixteen male broiler chicks, 10 -25 days of age, were fed experimental diets that contained 230, 210, 190 and 170 g CP/kg with adequate amounts of total and digestible essential amino acids at or above NRC (1994) recommendations. Two other diets were the same as the 190 and 170 g CP/kg diets but contained additional glycine and glutamic acid. Reduction in CP below 190 g/kg led to a decline in body weight and feed intake and an increase in fat deposition in body, as would be expected. Plasma T 4 concentration decreased significantly in the birds on the 170 g CP/kg diet and supplementation of glycine and glutamic acid had no effect on hormonal levels of the thyroid despite the reduction in whole-body and abdominal cavity fat deposition. Plasma T 3 concentration was not affected. Therefore, it is concluded that a reduction in circulatory levels of T 4 that occurs in broiler chicks fed diets containing below 190 g CP/kg though with adequate essential amino acids, may be an effective method of increasing fat deposition.

Effects of glucose oxidase on the growth performance, serum parameters and faecal microflora of piglets

“…Triiodothyronine and thyroxine are tyrosine-based hormones produced by the thyroid gland, and plasma T 4 can be converted into T 3 (Sterling et al, 1970). Thyroid hormones have profound effects on important physiological processes such as development and growth (Visser, 1990;Namroud et al, 2010) and regulation of metabolism (Decuypere et al, 1983;. Another key factor is GH, which mainly stimulates growth, cell reproduction and regeneration (Sorensen et al, 1992).…”

“…Various commensal and pathogenic bacterial species are present in the gastrointestinal tracts of pigs, especially pathogenic, which represent a major source of economic loss to the pig industry worldwide (Pluske et al, 2002;Namroud et al, 2010). Of these, haemolytic enterotoxigenic, Escherichia coli, is the primary infectious agent of post-weaning colibacillosis, which provokes hypersecretory diarrhoea through the release of specific enterotoxins (Argenzio, 1992;Jones et al, 2001).…”

Supplementation of L‐glycine and L‐glutamate to Japanese quails from 01 to 36 days of age using the ideal protein concept

“…A reduced feed intake was also observed in broilers fed reduced protein content levels and supplemented with limiting essential and non‐essential amino acids (McGill et al, ; Namroud et al, ; Yamazaki, Murakami, & Takemasa, ).…”

“…It is still controversial to what extent dietary protein may be reduced (Aftab, Ashraf, & Jiang, ). Many authors corroborate the premise that reductions above four percentage points decrease broiler performance and increase the fat content in the carcass (Aftab et al, ; Namroud, Shivazad, & Zaghari, ; Namroud, Shivazad, Zaghari, & Zare Shahneh, ; Waldroup, Jiang, & Fritts, ; Yamazaki, Murakami, & Takemasa, ).…”

“…Carew et al () and Sun et al () reported that the reduction in feed intake and performance may be caused by changes in serum levels of triiodothyronine and thyroxine. When studying the protein reduction and supplementation of L‐glycine and L‐glutamate in broiler diets, Namroud Shivazad Zaghari and Zare Shahneh () observed a reduction in thyroxin levels. This led to reduced broiler performance and increased fat content in carcasses, the same response evidenced in the present study.…”