Determinations of cell fragility were performed on cod muscle frozen at −29° and then stored at −0.5° to −3.5°, at half degree intervals. The rate of denaturation was found to be maximal at a temperature close to −1.5°. Fresh tissue supercooled to the same temperature was not denatured.
For 8 weeks feeding trial, two hundred and seventy, 53 weeks old laying hens were used to investigate the effects of dietary supplementation of vitamin B12 or biotin and/or bile acids on performance, egg quality, fat digestibility and liver composition and histopathology. Birds were randomly divided into 6 groups (three replicates) and fed the experimental diets; group1 (G1) fed on the basal diet without additives as control while G2 and G3 supplemented with 0.02 ppm vitamin B12 and 0.3 mg biotin/kg diet respectively, groups 4-6 fed as the previous detailed design of G1-G3 with the addition of 400 g of dried bile acid (DBA) /tone feed. Biotin supplementation significantly (P˂0.05) increased body weight losses of laying hens, both vitamins significantly (P˂0.05) decreased daily feed intake (FI) and improved FCR. DBA addition alone or with biotin reduced these weight losses along with significant (P˂0.05) increase in daily FI. Vitamin B12 supplementation alone or with DBA increased average egg production (P˂0.05) while was reduced with biotin supplementation. Fat digestibility was non-significantly improved (P≥0.05) with both vitamins supplementation without or with DBA. Biotin significantly (P˂0.05) reduced the average yolk relative weight, which was increased when mixed with DBA, while significantly increased average egg albumin relative weight. Vitamin B12 or biotin addition without or with DBA non-significantly increased blood serum GOT and GPT activities, non-significantly reduced (P≥0.05) fat content of liver tissue (on dry matter or fresh basis) and serum lipid profile parameters except serum HDL concentration, was increased, with no histopathological changes in hepatic tissue. It could be summarized that vitamin B12 supplementation without or with DBA is recommended in layer diet as it gave the best performance, reduced serum lipid profile and improved fat digestibility and the hepatic health.
The denaturation of cold‐stored cod fillets was inhibited to some extent by treatment with glycerol solution before freezing, 10% being the optimum concentration. There was less ice present at a given temperature in frozen tissue pre‐treated with glycerol than in the controls, and this observation has shed some light on the nature of the protective mechanism.
LOVE et a1.-PROTEIN DENATURATION I N FROZEN FISH. X 259 PROTEIN DENATURATION IN FROZEN FISH. X.*-Changes in cod muscle in the unfrozen state, with some further observationson the principles underlying the cell fragility method By R. M. LOVE, M. M. AREF,? M. K. ELERIAN, (the late) J. I. M. IRONSIDE, ELEANOR M. MACKAY and M. G. VARELASA study was made of the changes in the muscle proteins that occur when cod are kept in ice, using both protein extractability in salt solution and cell fragility ' values as criteria. The results by the two methods did not agree, and the reason for this is discussed with the aid of photomicrographs of homogenates of cod muscle. I t appears that changes in extractability are the consequence of a binding together of structural protein molecules and perhaps myofilaments, while a binding together of myofibrils is the agent causing changes in cell fragility readings. Cold storage changes the fragility of the cells (breakdown to fibril level), while bacterial action during stowage in ice changes the fragility of the myofi brils.
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