| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作系所 === 98 === Mastitis is the one of the most costly diseases in the dairy industry, with economic losses of approximately two billion dollars annually in the United States alone. Mastitis results in decreased milk production, increased veterinary costs, and early culling or death of animals. Conventional herd management practices such as pre- and post-milking teat dipping and dry cow therapy with antibiotics are unable to reduce the incidence of new infections. New therapeutic agents are therefore needed for mastitis control and prevention. Soluble CD14 (sCD14) has been shown to play an important role in the resistance to mastitis induced by Gram-negative bacteria. The level of sCD14 milk might be important to the susceptibility of mastitis during lactation period. In the present study, cows with high and low levels of sCD14 in milk were challenged by live E. coli bacteria the mammary gland, and our
results showed that cows with higher levels of sCD14 in milk had higher somatic cells counts (SCC), rectal temperature, and milk production, coupled with decreased bacterial load, than those with lower levels of sCD14 in milk. Therefore, selecting cows with a naturally high concentration of sCD14 in milk could be beneficial to the dairy industry. In addition, porcine sCD14 was characterized in the body fluids of pigs. The porcine sCD14 with a molecular weight of about 50 kDa was detected in colostrum, milk, and serum. The concentration of sCD14 in porcine milk secretion was high in the first three day (colostrum) and after that it was declined. In order to produce recombinant porcine sCD14 (rposCD14) for further research and as a potential feed additive to enhance the immunity of weaning piglets, Pichia pastoris (GS115 and X-33) were used as the expression system. Analysis of the genomic DNA sequences showed that the rposCD14 gene was integrated into the genome of P. pastoris. However, the expression was not successful. The expression of rposCD14 was also carried out in a baculovirus expression system without success. Factors responsible for the failure of expressing rposCD14 in both systems required further investigation.
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