Identification of pork quality parameters by proteomics.

A major parameter for quality of pork is its waterholding capacity (WHC). Prediction of WHC immediately after slaughter would be of benefit both to slaughterhouses for reasons of better logistics and/or branding of premium-meat, and to consumers for improved quality of meat products such as ham. In our pilot study on proteome analysis of porcine muscle by two-dimensional electrophoresis, we have identified at least three and possibly eight significantly changed proteins that may serve as marker proteins for waterholding capacity. The most clearly identified proteins are creatine phospho kinase M-type (CPK), desmin, and a transcription activator (SWI/SNF related matrix-associated actin-dependent regulator of chromatin subfamily A member1, SNF2L1). A possible mechanism of how these proteins may influence WHC is discussed. An optimised protocol for protein extraction that provides for sufficient amounts of relatively pure proteins has been developed. Further studies are needed to validate and extend our preliminary results.

Enzymatic degradation of prion protein in brain stem from infected cattle and sheep.

Prions-infectious agents involved in transmissible spongiform encephalopathies-normally survive proteolytic and mild protein-destructive processes. Using bacterial keratinase produced by Bacillus licheniformis strain PWD-1, we tested conditions to accomplish the full degradation of prion protein (PrP) in brain-stem tissue from animals with bovine spongiform encephalopathy and scrapie. The detection of PrPSc, the disease-associated isoform of PrP, in homogenates was done by Western blotting and various antibodies. The results indicated that only in the presence of detergents did heat pretreatment at >100 degrees C allow the extensive enzymatic breakdown of PrPSc to a state where it is immunochemically undetectable. Proteinase K and 2 other subtilisin proteases, but not trypsin and pepsin, were also effective. This enzymatic process could lead to the development of a method for the decontamination of medical and laboratory equipment. The ultimate effectiveness of this method of prion inactivation has to be tested in mouse bioassays.

Active immunization against gonadotrophin-releasing hormone in Chinese male pigs: effects of dose on antibody titer, hormone levels and sexual development.

The objective of this study was to determine the optimal dose of a GnRH vaccine for immunocastration of Chinese male pigs, based on immune, endocrine and testicular responses. Forty-two crossbred (Chinese Yanan x Large White) male pigs were randomly assigned to one of the five treatments as follows: (I) 0 microg (control, n=8); (II) 10 microg (n=8); (III) 62.5 microg (n=8); (IV) 125 microg (n=8); (V) 250 microg (n=10), D-Lys6-GnRH tandem dimer (TDK) peptide equivalent of conjugate (TDK-OVA), using Specol as the adjuvant. Pigs were immunized at 13 and 21 weeks of age and were slaughtered at 31 weeks of age. Blood samples for antibody titer and hormone assays were collected at 13, 21, 24 and 31 weeks of age. At these time-points, testis size was also measured. At slaughter, testis weight was recorded and fat samples were collected for androstenone assay. Four animals, one out of each immunized group, responded poorly to the immunization (non-responders). At slaughter, serum testosterone and LH levels, fat androstenone levels and testis size/weight of these non-responders were similar to those in control animals. Antibody titers of non-responders were substantially lower (P<0.05) than in other immunized pigs. For the animals that responded well to the immunization (immunocastrated pigs), serum testosterone and LH levels, fat androstenone levels and testis size or weight were reduced (P<0.05) as compared to either controls or non-responders, at all doses tested. There was a significant effect of dose of TDK-OVA on antibody titers. The overall mean antibody titers in the 62.5 or 125 microg dose group (53.6 and 50.5% binding, respectively) were significantly higher than in the 10 or 250 microg group (39.2 and 40.24% binding, respectively). At slaughter, there was a significant dose effect on testis size or weight and on serum testosterone levels, but there was no dose effect on serum LH levels and fat androstenone levels. Testis size or weight in the 10 microg group was reduced to a lesser extent (P<0.05) than in the three higher dose groups. At slaughter, in comparison to controls, mean testis size of immunocastrated pigs in treatments II-V was reduced to 55, 21, 33 and 25%, respectively, whereas testis weight was reduced to 39, 12, 18 and 14%, respectively. Reduction of testis size and/or weight is important for visual assessment of castration at the slaughterline, therefore, it is concluded that a dose of 10 microg peptide is not suitable. We conclude that, within the dose-range studied, the 62.5 microg dose is optimal for future GnRH immunization studies or future practical use in immunocastration of Chinese male pigs.