Prediction of pork quality using visible/near-infrared reflectance spectroscopy.

Near-infrared spectroscopy is a rapid screening technique that may be used to determine meat quality traits. While several calibrations on meat quality parameters have been published, the accuracy and robustness of a calibration has rarely been validated with independent samples. In this study, in 207 loin muscles from three independent batches of pigs of different breeds drip loss, colour values, pH and intramuscular fat were determined. Calibrations were made from each combination of two batches and validated with the third batch. Validations of pH, intramuscular fat, drip loss, and L(∗), a(∗), and b(∗) colour values had on average 1.27 times the accuracy of the calibration. Breed did not influence the accuracy of the calibration. Intramuscular fat can be determined with good accuracy. Muscle pH and colour values are reasonably well predicted. Drip loss can not be determined quantitatively with sufficient accuracy, but classification of quality groups is possible.

Quantification of calpastatin using an optical surface plasmon resonance biosensor.

An immunological biosensor for calpastatin was developed on a surface plasmon resonance based system (Biacore Q). The performance of the biosensor assay was evaluated using ovine and bovine muscle and heart extracts with known calpastatin activity. In addition, the relationship between immunologically detectable calpastatin at 1 day postmortem and shear force at 14 days postmortem was investigated for bovine longissimus dorsi. Calpastatin biosensor results for several experiments were linearly related to calpastatin activity measurements with correlation coefficients ranging from 0.51 to 0.99. The intra- and inter-assay CVs were <6% (n=12). During postmortem storage, the amount of immunologically detectable calpastatin decreased faster than the inhibitory activity in the enzymatic assay. Probably, the epitope recognized by the antibody is degraded faster than the inhibitory sites of calpastatin during postmortem storage. Calpastatin content at 1 day postmortem was correlated to shear force at 14 days postmortem (r=0.75). It is anticipated that developments in the near future will allow for at-line calpastatin determinations in beef plants. At present, the calpastatin biosensor assay appears suitable for research purposes where large numbers of samples need to be processed for breed evaluation or selection programs because this assay requires less labor than other methods.

Short-term feeding strategies and pork quality.

Two experiments were done to determine whether short-term supplementation (5 days pre-slaughter) with magnesium acetate, or a combination of magnesium acetate, tryptophan, vitamin E and vitamin C would improve pork quality. In the first experiment the pigs (Pietrain×Yorkshire, n=96) were fed a standard feed or a magnesium supplemented feed for 5 days prior to slaughter. As a possible stress factor half of the animals were slaughtered upon arrival at the slaughterplant whereas the remaining animals were allowed two hours of rest in lairage before slaughter. Magnesium supplementation did not result in an increase in plasma magnesium concentration at slaughter. Omission of lairage resulted in higher plasma glucose concentrations, but plasma lactate concentrations were not affected. Drip loss and ultimate pH were not affected by diet or omission of lairage. Omission of lairage resulted in poorer color characteristics. This effect was prevented by supplementation with magnesium. In the second experiment the pigs (Pietrain×Yorkshire, n=92) were fed a standard feed or this standard feed supplemented with magnesium acetate, tryptophan, vitamin E and vitamin C for 5 days prior to slaughter. Supplementation with vitamin E did not increase muscle vitamin E concentration. Inclusion of supplements in the diet failed to improve water-holding capacity or color characteristics. These results indicate that short-term supplementation with magnesium acetate, tryptophan, vitamin E and vitamin C is of little value in improving pork quality when pigs are not stressed beyond levels associated with routine slaughter procedures.

Plasma activities of lecithin:cholesterol acyltransferase, lipid transfer proteins and post-heparin lipases in inbred strains of rabbits hypo- or hyper-responsive to dietary cholesterol.

Plasma lipoproteins, plasma activities of lecithin:cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP) and post-heparin lipases were measured before and after cholesterol challenge in two inbred strains of rabbits with either a high (hyper-responders) or a low (hyporesponders) response of plasma cholesterol to dietary cholesterol. The purpose of this study was to provide clues about the mechanisms underlying the effect of dietary cholesterol on lipoprotein levels and composition, and particularly those underlying the strain difference of this effect. Cholesterol feeding (0.15 g of cholesterol/100 g of diet) caused increased plasma total cholesterol concentrations and an increased ratio of cholesteryl esters:triacylglycerol in all lipoprotein particles in both strains; these effects were significantly greater in hyper- than hypo-responsive rabbits. Feeding on the high-cholesterol diet lowered plasma triacylglycerols in hyper-responders, but caused increased plasma triacylglycerol levels in hyporesponders. This was accompanied by significantly greater increases in the activities of hepatic triacylglycerol lipase and lipoprotein lipase in hyper- than in hypo-responders. Both strains showed a dietary-cholesterol-induced rise in plasma CETP as well as in PLTP activity. The increase in PLTP activity was greater in the hyper-responders, but that of CETP was less. There was no effect of dietary cholesterol on LCAT activity. It is hypothesized that the lipases are involved in the removal of cholesterol-rich lipoproteins.

Dietary cholesterol-induced down-regulation of intestinal 3-hydroxy-3-methylglutaryl coenzyme A reductase activity is diminished in rabbits with hyperresponse of serum cholesterol to dietary cholesterol.

Key enzymes of cholesterol metabolism were studied in two inbred strains of rabbits with hyper- or hyporesponse of serum cholesterol to dietary cholesterol. Baseline 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase activity in liver was similar in hypo- and hyperresponders, but that in intestine was twofold higher in the hyporesponders. The addition of cholesterol (3 g/kg) to the diet caused similar depression of hepatic HMG-CoA reductase activity in the two strains, whereas intestinal HMG-CoA reductase activity was significantly reduced in hyporesponders but not in hyperresponders. Cholesterol feeding induced higher free cholesterol concentrations in hepatic and intestinal microsomes of both hypo- and hyperresponders and higher activity of hepatic acyl-CoA:cholesterol acyltransferase (ACAT). Hepatic ACAT activity was significantly lower in cholesterol-fed hyperresponders than in hyporesponders, which may have contributed to the observed higher free cholesterol concentrations in hepatic microsomes of cholesterol-fed hyperresponders. Intestinal ACAT activity was similar in hypo- and hyperresponders; cholesterol feeding tended (P = 0.11) to elevate the activity of this enzyme. Hepatic cholesterol 7 alpha-hydroxylase activity was significantly higher in cholesterol-fed hyperresponders than in hyporesponders; it was slightly depressed after cholesterol loading in both rabbit strains.

[Supplementary hay reduces fur chewing in rabbits]. / Hooi als bijvoeding reduceert pelsbijten bij konijnen.

We tested the hypothesis that loose grass hay as a supplement to a pelleted diet reduces fur chewing in rabbits. Weanling rabbits (n = 315) were given one of three diets ad libitum: a control, pelleted diet, the pelleted diet containing 20% (wt/wt) hay meal or the pelleted diet plus loose hay. Fur chewing was assessed indirectly by blind scoring of the extent of alopecia in live rabbits and the amount of gastric hair after slaughter. Rabbits given either loose hay or the diet pellets containing hay displayed significantly less alopecia on the back and sides than control rabbits did. Loose hay, but not the pellets containing hay, completely prevented the development of alopecia on the forehead. The provision of loose hay as supplement to the control diet pellets significantly reduced the amount of gastric hair, whereas inclusion of hay meal into the pellets had no effect. It is concluded that supplemental loose hay prevents rabbits from pulling off fur from the forehead of cage mates. This effect of hay might be related to satisfaction of a craving for nibbling.

Secretion of lipoprotein cholesterol by perfused livers from rabbits hypo- or hyperresponsive to dietary cholesterol: greater dietary cholesterol-induced secretion in hyperresponsive rabbits.

In two inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol, secretion of lipoprotein cholesterol by perfused livers was determined. The perfused rabbit livers secreted cholesterol into the perfusate at essentially constant rates between 30 and 120 min of perfusion. Most of the secreted cholesterol resided in VLDL. Addition of cholesterol to the diet of the donor rabbits caused a higher cholesterol:triglyceride ratio of lipoproteins secreted by the perfused liver. Such a rise was also seen in the plasma lipoproteins of cholesterol-fed rabbits. Plasma and perfusate lipoproteins differed in that the former had a higher cholesterol:triglyceride ratio. Cholesterol feeding produced a higher output of lipoprotein cholesterol by the perfused liver, the increment being greater in hyper- than in hyporesponders. Cholesterol-fed hyperresponders had higher liver cholesterol concentrations than their hyporesponsive counterparts. There was a direct relationship between the rise of liver cholesterol concentrations and the rise of hepatic secretion of lipoprotein cholesterol; this relationship was identical for hypo- and hyperresponders. We conclude that the higher cholesterolemic response to cholesterol feeding in the hyperresponders, when compared with the hyporesponders, can be explained, at least partly, by a greater cholesterol-induced hepatic secretion of lipoprotein cholesterol.

Evaluation of the use of serum lathosterol concentration to assess whole-body cholesterol synthesis in rabbits.

Serum lathosterol concentration in rabbits was assessed as a possible indicator of whole-body cholesterol synthesis. In random-bred New Zealand White (NZW) rabbits fed a control diet or a diet containing either cholesterol, simvastatin, or cholestyramine, neither serum lathosterol concentration nor the serum lathosterol:total cholesterol ratio systematically corresponded with the anticipated rate of cholesterol synthesis. In control rabbits and those fed simvastatin or cholestyramine, whole-body cholesterol synthesis, which was calculated from the sterol balance, was correlated with serum lathosterol concentration when expressed relative to cholesterol in very low, intermediate, and low density lipoproteins (VLDL + IDL + LDL) (r = 0.61; n = 23; P = 0.002). The low correlation coefficient indicates that the predictive value of the lathosterol: (VLDL + IDL + LDL) cholesterol ratio is limited when applied to individual rabbits. Cholesterol and simvastatin feeding reduced the group mean serum lathosterol:(VLDL + IDL + LDL) cholesterol ratio, whereas cholestyramine in the diet raised the group mean ratio in the NZW rabbits. We conclude that the serum lathosterol:(VLDL + IDL + LDL) cholesterol ratio may be an indicator of group mean rates of whole-body cholesterol synthesis in rabbits but may not yield reliable information on individual rabbits. The lathosterol:(VLDL + IDL + LDL) cholesterol ratio predicted that in hyperresponsive inbred rabbits, showing an excessive hypercholesterolemia after cholesterol feeding, baseline whole-body cholesterol synthesis is lower than in hyporesponsive rabbits. Addition of cholesterol to the diet caused a reduction of predicted cholesterol synthesis in hypo- but not in hyper-responsive rabbits.

Influence of dietary fats on butyrylcholinesterase and esterase-1 (ES-1) activity in plasma of rats.

We studied the effects of dietary fats, especially fish oil, on the activities of esterase-1 (ES-1) and butyrylcholinesterase in the plasma of rats. The identification of nutritional determinants of these enzymes could provide clues as to their physiological function. Fish oil, when compared with corn oil, consistently caused increased activities of both enzymes. Plasma ES-1 activity, but not butyrylcholinesterase activity, was increased after isocaloric replacement of carbohydrates by coconut fat. Dietary medium-chain triglycerides, when compared with corn oil, produced decreased and increased activities of butyrylcholinesterase and ES-1, respectively. Various plant fats, such as corn oil, linseed oil, coconut fat, palm oil, palm kernel oil, soybean oil and rapeseed oil, did not differentially influence butyrylcholinesterase activities. Plasma triglyceride concentrations were lowered by fish oil and increased by coconut fat and palm kernel oil. For individual rats in 5 out of 6 experiments, weak, negative correlation coefficients of the order of 0.3 were found between the changes in plasma butyrylcholinesterase activities and in plasma triglyceride concentrations.