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Title: Milk production traits of beef cows as affected by horn fly count and sire breed type

item MAYS, ANGELA - University Of Arkansas
item BROWN, MICHAEL - Retired ARS Employee
item VONTUNGELN, DAVID - Retired ARS Employee
item ROSENKRANS, CHARLES - University Of Arkansas

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2014
Publication Date: 2/3/2014
Citation: Mays, A.R., Brown, M.A., Vontungeln, D.L., Rosenkrans, C.F. 2014. Milk production traits of beef cows as affected by horn fly count and sire breed type. Journal of Animal Science. 92(3:1208-1212.

Interpretive Summary: Annual economic losses caused by external parasites including horn flies are estimated to range be up to $1 billion. Horn fly infestation can result in cattle with dermatitis and poor hide quality; mastitis and reduced milk production; diminished time grazing and subsequent reduced weight gain; and increased heart and respiratory rates Cattle producers have used pesticides as their primary means of controlling horn fly infestations. However, that practice has resulted in horn fly resistance to most pesticides. An alternative to chemical control of horn flies is use of natural or genetic resistance. It has been demonstrated that beef cattle resistance to horn flies had a heritability coefficient of 0.59 and hybrid vigor for horn fly resistance has been identified. Pests are one of many forms of stress that affect cattle production. Heat shock protein-70 (Hsp70) is one member of a large family of proteins that act via cellular mechanisms to protect animals from stress. Research by scientists at the University of Arkansas and USDA-ARS with Brahman, Angus, and reciprocal-cross cattle discovered alleles in Hsp70 that resulted in greater hornfly resistance in these cattle. It is anticipated that the use of genotyping for hornfly resistance can provide a reasonable alternative to use of pesticides for control of horn flies in beef cattle.

Technical Abstract: Horn fly infestations on beef cattle results in decreased productivity and challenges enterprise sustainability. Objective of this experiment was to determine the relationships among, cattle breed, heat shock protein 70 (Hsp70) genotype, and horn fly density. Angus (n = 20), Brahman (n = 17), and reciprocal cross (n = 31) cows were assigned to one of two permanent forage types. The two forages were wild-type endophyte-infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] and common bermudagrass [Cynodon dactylon (L.) Pers]. Fly density was determined weekly for each cow from May through October. Genomic DNA from each cow was prepared from buffy coat and purified. Specific PCR primers were used to produce Hsp70 coding sequence (G2033C) and promoter (C895D and G1128T) amplicons. Each amplicon was sequenced and genotypes assigned to each SNP site. Horn fly density was affected (P < 0.0001) by an interaction between month of fly count and forage. In September, cows grazing tall fescue had fewer (P < 0.05) flies than cows grazing bermudagrass. Cows that were heterozygous at coding sequence SNP G2033C had more (P < 0.07) flies than homozygous cows. Similarly, cows that were heterozygous for either of the two SNP of the promoter region had a higher (P < 0.1) fly density than cows that were homozygous for either SNP. Use of Hsp70 genotyping in combination with forage management could be useful in identifying production systems that decrease horn fly infestation which would increase the profitability and sustainability of cattle production.