Turtle. W. L. and S. L. Balloun. 1976. Leucine, isoleucine and 

 valine interactions in turkey poults. Poult. Sci. 55:1737. 



Development and Transfer of Bacterial 

 Resistance to Antimicrobial Compounds 



A portion of the enteric bacteria of all animals 

 may possess resistance to antimicrobial drugs 

 commonly used therapeutically and at low levels 

 in the feed of animals for growth promotion and 

 disease prevention. Research on these factors (R- 

 factors) has shown that the incidence of R-factor 

 containing bacteria increases when antibiotics are 

 fed and that this resistance can be transferred 

 from one strain of bacteria to another. The poten- 

 tial threat to human and animal health from the 

 acquisition of such resistance, and recognition of 

 those practices related to the use of drugs that 

 increase the population of resistant bacteria in our 

 ecosystem, has developed into an important and 

 urgent area of investigation. 



A complete understanding of the nature of bac- 

 terial resistance to antimicrobial drugs is essential 

 for the protection of animals and human health. If 

 there is a greater risk of transfer of resistance to 

 pathogenic bacteria from the common usage of 

 antibiotics, the extent and nature of the risk must 

 be established. A true appraisal of the R-factor 

 pool in man and animals is badly needed to deter- 

 mine when any further change occurs as well as 

 the significance of such change to animal and 

 human health and to medical practice. 



Gutzmann. F., H. Layton. K. Simkins and H. Jarolmen. 1975. 

 Influence of antibiotic-supplemented feed on occurrence and 

 persistence of salmonella typhimurium in experimentally in- 

 fected swine. Am. i. Vet. Res. .17:649 



Lakhotia, R. I., and J. F. Stephens. 197.3 Incidence of drug 

 resistance and R-factor among Salmonellae isolated from poul- 

 try. Poult. Sci. 52:2266. 



Nivas, S. C, M. D. York and B. S. Pomeroy. 1976. In vitro 

 and in vivo transfer of drug resistance for Salmonella and 

 Escherichia coli strains in turkeys. .37:433. 



Walton. J. R. 1971. The public health implications of drug-re- 

 sistant bacteria in farm animals. Ann. NY Acad. Sci. 1X2:358. 



Successful Transfer of Fertilized Ova in 

 Cattle, Sheep, and Swine 



Blood hormone studies, together with surgical 

 and laboratory procedures have established the 

 necessary technology for successful transfer of 

 fertilized ova in cattle and swine. Radio-immune 

 assay techniques are being used to determine 

 optimum timing with hormonal synchronization 

 between donor and recipient females. Surgical 

 procedures, techniques for superovulation, and 

 laboratory requirements for storage and transport 

 of ova have been developed. 



The new knowledge gained of ovarian function, 



8 AGRICULTURE 



requirements for in vitro culture of ova, and the 

 technique for transfer of fertilized ova from don- 

 or to recipient females in these species has greatly 

 extended the potential genetic contribution of 

 superior females. Both private and commercial 

 applications of this technology are already appar- 

 ent. Much of the basic information obtained is 

 being applied to research on the potential for mul- 

 tiple births in cattle and control of litter size in 

 swine. The greater control over ovarian function 

 now permitted, together with a better understand- 

 ing of ovarian-uterine relationships, has also pro- 

 vided a basis for further determining causes of 

 prenatal death in both species. 



Dziuk. P. J. 1968. Egg transfer in cattle, sheep and pigs. The 

 Mammalian Oviduct, edited by Hafez, E. S. F., and Blandau, 

 R. J., p. 407. University of Chicago Press. 



Rowson. L. E. A.. R. A. Moor and R. A. S. Lawson. 1969. 

 Fertility following egg transfer in the cow: effect of method, 

 medium and synchronization of oestrus. J. Reprod. Fertil. 



18:517. 



Seidel, G. E., Jr., L. L. Larson. C. H. Spilman. J Hahn and 

 R. H. Foote. 1971. Culture and transfer of calf ova. J. Dairy 

 Sci. 54:923. 



Wright, R. W., P. T. Cupps, M. Drost and G. E. Bradford. 

 1974. Culture of sheep and cow ova in various media. Proc. 

 West. Section Am. Soc. An. Sci. 25:293. 



Discovery of Biological Function of Alpha- 

 Lactalbumin 



Alpha-lactalbumin is a protein found in the 

 skim milk of many species. It is one of two pro- 

 teins required for the lactose synthetase enzyme, 

 the enzyme responsible for biosynthesis of lactose 

 in the mammary gland or in a test tube. This dis- 

 covery resulted from efforts to purify the enzyme 

 from bovine skim milk into two fractions A and 

 B. There was no enzyme activity in either protein 

 A or protein B tested separately, but the presence 

 of both proteins A and B gave significant enzy- 

 matic activity. Protein B was shown to be alpha- 

 lactalbumin, a relatively low molecular-weight 

 substance, and a subunit in the enzyme structure. 

 This subunit has been considered a "specifier pro- 

 tein," having the ability to change the catalytic 

 activity of an existing protein, similar to other 

 enzymes that have regulatory subunits. 



Current work on lipid metabolism, rather than 

 the above carbohydrate metabolism, is finding the 

 "specifier factor" to be a useful concept in syn- 

 thesizing fats with liver microsomes. 



Brodbeck, U. and K. E. Ebner. 1%6. The subcellular distribu- 

 tion of A and B proteins of lactose synthetase in bovine and 

 rat mammary tissue. J. Biological Chemistry. 241. 5526-5532. 



i;hncr. K E. and Brodbeck, U. 1968. Biological role of alpha- 

 lactalbumin. A review. J. Dairy Science, 51, 317-322. 



