Chick production data

The exact form in which non-crosslinked elastin is secreted from smooth muscle cells is yet to be clearly defined. Foster et al. (36) have suggested that a non-cross linked elastin (pro-elastin) is secreted from smooth muscle cells in a form that is approximately 120,000 to 140,000 daltons. They have suggested that proelastin is cleaved to smaller molecular weight forms of non-crosslinked elastin. It should be noted, however, that this view is not entirely supported by data from other laboratories. There are two reports on the use of isolated mRNA from chick aorta suggesting only a 70,000 dalton non-cross linked elastin is the major product of translation (37,38). There is also a recent report suggesting that aortic mRMA translates a 200,000 dalton putative elastin product (39). We have recently isolated a non-crosslinked elastin from the aortas of copper deficient chicks that appears to be 100,000 daltons (27). Its amino acid composition is similar to that for tropoelastin (Table III). A major problem in resolving these points is that the trypsin-like proteinase associated with elastin is not easily denatured or separated from the non-crosslinked forms of elastin. The proteinase is also not readily inhibited by commonly used inhibitors for trypsin-like proteinases (26). 

The data showed that E. coli was almost 100% resistant to therapeutic antibiotics such as penicillin, erythromycin, tetracycline and streptomycin, which have been in use for a long time. Newer antibiotics are still effective but E. coli may become resistant to them as well overtime. Due to this rapid development of resistance, E. coli diarrhoea in piglets, MMA in sows and umbilicus inflammation in chicks may become more severe, leading to higher economic losses in livestock production. Some potential problems in layers are displayed in table 2. 

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