Oxidative stability and α‐tocopherol retention in turkey burgers during refrigerated and frozen storage as influenced by dietary α‐tocopheryl acetate

1. The effect of vitamin E (α‐tocopheryl acetate) in turkey diets on the oxidative stability of raw and cooked turkey burgers and on the retention of α‐tocopherol during refrigerated (4°C) or frozen (‐20°C) storage was investigated. One hundred and two, one‐day‐old T‐8^S turkey poults were divided at random into 3 groups of 34 animals each and fed on either a basal diet (normal commercial turkey diet) supplemented with 20 mg α‐tocopheryl acetate/kg (control) or fed an α‐tocopherol supplemented diet containing 300 (E300) or 600 (E600) mg α‐tocopheryl acetate/kg for 21 weeks.

2. Dietary supplementation with α‐tocopheryl acetate significantly reduced TBARS numbers in both raw and cooked burgers during refrigerated and frozen storage.

3. The mean values of α‐tocopherol in raw and cooked burgers stored at 4°C did not change during storage.

4. In the case of both raw and cooked samples stored at ‐20°C, the α‐tocopherol values decreased from 5.67 to 3.54 and from 3.56 to 2.30 μg/g in the raw burgers from turkeys from the E600 and E300 treatments, respectively, after 4 months storage. The values decreased from 5.60 to 2.88 and from 3.29 to 1.85 μg/g in cooked burgers from turkeys from the E600 and E300 treatments, respectively, after 5 months storage.     

Influence of heated vegetable oils and α‐tocopheryl acetate supplementation on α‐tocopherol,fatty acids and lipid peroxidation in chicken muscle

1. Chicks were fed on diets containing fresh, heated or α‐tocopheryl acetate‐supplemented heated vegetable oils. The effects on α‐tocopherol status, and on the fatty acid composition and oxidative stability of thigh and breast muscle were determined.

2. Plasma α‐tocopherol was significantly correlated with α‐tocopherol concentrations in thigh and breast muscle.

3. The fatty acid profiles of muscle lipids reflected dietary fatty acid composition.

4. The consumption of heated sunflower and linseed oils reduced α‐tocopherol status, altered fatty acid composition of muscle lipids and increased susceptibility of muscle to lipid oxidation.

5. Supplementation of diets containing heated oils with α‐tocopheryl acetate resulted in some alleviation of these effects.

6. The results indicate that caution should be exercised in the use of thermally oxidised oils in poultry diets if undesirable changes in composition and oxidative stability of carcase lipids are to be avoided.     

Effects of dietary protein content,addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphur‐containing amino acids in broilers

1. Two experiments were conducted with male broiler chicks from 2 to 5 weeks of age to determine the effect of dietary protein content and amino acid balance on the response to dietary sulphur‐containing amino acids (SAA) in terms of performance and carcase quality.

2. In experiment 1, 5 graded amounts of a DL‐methionine and L‐cysteine (1:1 by weight) mixture were added to basal diets containing 197 or 233 g crude protein/kg. The diets containing 197 g protein/kg were fed with or without the further addition of 36 g crude protein/kg from nonessential amino acids. The amino acid balance of all diets was kept constant for all essential amino acids except the SAA. In experiment 2, 5 graded amounts of SAA from either a crystalline source (DL‐methionine or a mixture of DL‐methionine and L‐cysteine) or from intact proteins were added to a diet containing 208 g protein/kg.

3. At each protein concentration there were significant responses to the SAA addition in weight gain, food conversion efficiency, and carcase quality. Non‐linear exponential regression analyses were used to describe bird responses to SAA concentration. The broiler chick's requirement for SAA increased with increasing dietary protein concentrations ranging from 197 to 259 g protein/kg.

4. The utilisation of SAA differed also with differences in origin (crystalline or peptide‐bound), and methionine:cysteine balances. Compared to DL‐methionine, a 1:1 mixture of DL‐methionine and L‐cysteine was only 81% or 86% as effective in supporting growth or food conversion, respectively. SAA from added protein was even less effectively utilised.

5. The addition of nonessential amino acids tended to decrease food intake without affecting SAA utilisation.

6. Slaughter yield and breast meat yield were clearly increased while fat deposition was clearly decreased, by SAA addition. The response in breast meat yield suggested an important economic benefit for further meat processing. Nitrogen retention was significantly enhanced by SAA supplementation from crystalline sources, and this led to reductions of up to 30% in the amount of nitrogen excreted per kg weight gain.