In Iowa, dairy cattle are most commonly raised on land having rolling topography. Because the nitrogen contributions of alfalfa, their typical forage, and manure reduce the need for commercial fertilizer application, dairy cattle make a strong contribution to a more sustainable agricultural system. The high productivity of the dairy cattle, combined with the significant savings in purchased inputs, offers some producers a financially stable, environmentally preferable alternative to more traditional row-cropping approaches

Freeman, Albert E.

Kehrli, Marcus E., Jr.

English

In Iowa, dairy cattle are most commonly raised on land having rolling topography. Because the nitrogen contributions of alfalfa, their typical forage, and manure reduce the need for commercial fertilizer application, dairy cattle make a strong contribution to a more sustainable agricultural system. The high productivity of the dairy cattle, combined with the significant savings in purchased inputs, offers some producers a financially stable, environmentally preferable alternative to more traditional row-cropping approaches.</p

Freeman, Albert

Kehrli, Marcus

Digital Repository @ Iowa State University (ISU)

COMPETITIVE GRANTLeopold Center LEOPOLD CENTER FOR SUSTAINABLE AGRICULTURE Improved disease resistance in dairy cattle: Correlation of health disorders with measures of immune status and Genetic improvement for disease resistance by identify­ing sires whose daughters have fewer disease problems Background and goals In Iowa, dairy cattle are most commonly raised on land having rolling topography. Because the nitrogen contributions of alfalfa, their typi­cal forage, and manure reduce the need for commercial fertilizer application, dairy cattle make a strong contribution to a more sustain­able agricultural system. The high productiv­ity of the dairy cattle, combined with the significant savings in purchased inputs, offers some producers a financially stable, environ­mentally preferable alternative to more tradi­tional row-cropping approaches. As dairy cattle have been bred for higher production, however, their health problems have increased. Although many infectious diseases can be controlled by vaccines, others, such as mastitis and uterine infections, cannot. Furthermore, antibiotics in lactating cows are increasingly restricted because of their poten­tial to contaminate the milk and meat supply; only four antibiotics are currently approved for treating mastitis in lactating cows. More­over, these drugs are expensive. Because such diseases cause the greatest economic loss of any disease in dairy cattle, these investigators studied genetic selection as a means for cost-conscious dairy producers to avoid infectious diseases in cattle. Objectives of this research included (1) correlating health disorders with measures of immune status; (2) assessing its implications for a more sus­tainable dairy management system; and (3) using genetic	 improvement for disease resistance by identifying sires whose daughters have fewer disease problems. Leopold Center Progress Reports The ultimate goal of this work was to find methods to identify sires whose daughters will have fewer health disorders. Reducing the incidence of disease by breeding disease-re-sistant cattle may save money, reduce stress in cattle, and address health concerns associated with consuming meat and milk from cows that have been treated with drugs. Approach and methods Earlier work by these investigators and others using cows in mid-lactation indicated that there was at least some genetic control over disease resistance; the genetic implications were iden­tified by analyzing data from a battery of innate immune response tests and class I BoLA genetic typing. (In cattle, BoLA refers to a region on the twenty-third chromosome where all known genes that affect immune response are located.) The work evaluated the ability of neutrophils (white blood cells) to kill bacteria by ingesting it, as well as other, related abili­ties of neutrophils. It also measured cows' effectiveness in producing lymphocytes, an­other type of white blood cell, and their ability to multiply and produce antibodies and serum proteins. The results from this study indicated that differences between sire progeny groups could be detected, and it encouraged the inves­tigators to continue the work with funding from the Leopold Center. Because previous results suggested that ge­netic selection against mastitis and intramammary infections was a realistic goal, investigators collected data on mastitis inci­dence in particular and all health problems in general in a research herd. This way, mastitis occurrences could be clearly defined. (Re-REPORT 90-05 and 92-04 Principal investigator A. E. Freeman Animal Science Iowa State University Co-investigator M. Kehrli, Jr. National Animal Disease Laboratory, USDA-ARS Budget (90-05): $28,000 for year one $30,750 for year two (92-04): $33,000 for one year 77 Marcus Kehrli, Jr., of the National Animal Disease Laboratory (seated) and A. E. Freeman, ISU animal scientist, collaborated on this project. search herds were used instead of commercial herds because it is difficult to obtain a clear and consistent definition in the latter, which in turn makes conclusive statements on genetic variability in mastitis resistance unrepeatable across herds.) Cows from the ISU Dairy Breeding Research Herd at Ankeny were used for this project. Because most health disorders occur around calving, blood samples were collected five weeks before calving through five weeks following calving. Tests for 20 innate immune functions showed that all cows' immune systems were depressed at or near calving (see Fig. 1). To better illustrate the suppression of cows' immune system during calving, leukocytes were isolated from steers and used to establish laboratory standards. Data were analyzed via statistical models. In addition to this same battery of innate im­mune response assays used in the earlier work, class II BoLA locus 3.2 typing (the location of the gene on the 23rd chromosome) was used to evaluate the immune responses of the 137 cows in this project. Retroviral infections (such as bovine leukosis virus [BLV] and bovine immunodeficiency virus [BIV]) were also studied, but it was difficult to establish genetic relationships to indicators of disease resistance for BLV and BIV because the presence of antibodies in response to these diseases represents different disease stages and may be under different genetic control. Findings Older cows had more mastitis than younger cows, and length of lactation affected all mea­sures of mastitis including kind of cultured bacteria from the udder. Cows resulting from genetic selection for high milk production versus average production had neutrophils with greater capacity to kill bacteria. The heritabil­ity (proportion of total variation that is under genetic control) of all mastitis indicators aver­aged 10%. Generally, the result of the assays showed that levels of the innate immune re­sponses were high before calving, dropped at or near calving, and increased after calving; however, these levels differed among cows. Heritability estimates were obtained before, at, and after calving for the immune responses. Sire progeny groups differed significantly from each other for all but one assay. Further, some sires that had daughters with high production ranked high consistently for all neutrophil assays. This finding implies that immune profiles could be used for the selection of cattle with improved innate immune response with­out adverse effects on milk productivity. This work also indicated clearly that there are measurable genetic differences between cows for health disorders, particularly mastitis. Class II BoLA genes were found to be associated with immune response, affected resistance to mastitis, and together with immune responses accounted for between 30% and 40% of the variation in clinical mastitis. In addition, some sires that had consistently high neutro­phil activity were high production sires. These results clearly indicate that selection can be practiced to reduce health problems in dairy cattle. However, from a breeding perspective, mastitis indicators such as somatic cell count may be questionable as selection criteria be­cause it is not known whether a high milk somatic-cell score is indicative of a cow with mastitis, or whether a high score helps the cow combat or resist infection. Use of somatic cells as a selection criterion is under study by other investigators. Volume 3 (1994) 78 In summary, investigators demonstrated and thus confirmed altered immunologic functions in 137 periparturient dairy cows. This work constitutes the most comprehensive study of this nature conducted to date in that it included a larger number of tests conducted on a greater number of cows. This calving period coin­cides with an increased incidence of subclinical and clinical infectious disease. Underscoring the credibility of this study was the fact that the cows were at separate geographic locations and housed under completely different condi­tions (free stalls), fed different rations, and handled by different herd managers and milk­ers from those in experiments conducted by other investigators that preceded this work. In addition, previous studies involved a milking schedule with 7- and 17-hour intervals; a more conventional, 12-hour milking interval was followed in this study. These disparities in approach, when contrasted with similarity of results, illustrate that immune system suppres­sion occurs in calving cows under divergent management systems. Thus far, attempts to prevent immunosuppres­sion by preventing hypocalcemia (abnormally low calcium levels in the blood), by adminis­tering cytokines (proteins that allow commu­nication among cells of the immune system), or by nutritional manipulation have had lim­ited success. Thus, a genetic approach to Fig. 1. Activity in enhanced immunocompetence and disease re­sistance appears to be needed, and this work indicates such an approach is both feasible and justified. Implications When dairy cattle are incorporated into farm­ing operations, typically those located on ero-sion-prone topography, alfalfa is often used as a forage crop in rotation with corn and soy­beans. Because alfalfa and manure each con­tribute nitrogen to the soil, dairy cattle thus constitute an important component of a more sustainable farming system by reducing the need for commercial nitrogen fertilizer appli­cations. However, as production increases, so does the incidence of health problems in cattle. This research has demonstrated that health disorders can be reduced by genetic selection, which in turns reduces the use of antibiotics and other drugs that potentially threaten the safe production of dairy products and—via the milk and meat supply—human health as well. Other organizations supporting this work in­cluded Iowa State University, which provided its dairy breeding research herd for the experi­ments, and the National Animal Disease Cen­ter, which provided all laboratory work. This work has also been funded by Eastern Artifi­cial Insemination Coop., Inc. and 21 st Century Genetics Coop., Inc, Preliminary work, pre-the bfoodstream by neutrophils (white blood ceiis that fight bacteria), assessed by an iodination assay, increased untii two weeks before parturition and decreased rapidly by the first week after calving. Leopold Center Progress Reports 79 For more information contact A. E. Freeman, Animal Science, Iowa State University, Ames, Iowa 50011, (515) 294-3352. ceding the Leopold Center-funded experi­ments, was funded in part by the Holstein Association. This project included a significant education and outreach component. Numerous scien­tific publications have resulted from this work; in addition, investigators have disseminated project findings through various seminars and poster presentations as well as an invitational presentation at the Agricultural University of Wageningen in The Netherlands. These experiments attracted the attention of 21st Century Genetic Coop of Shawano, Wis­consin, and have resulted in a very large field trial now under way. A repeatability trial conducted by Dr. Marcus Kehrli, Jr., of the National Animal Disease Center—USDA-ARS, is evaluating blood from 10 bulls to establish the feasibility of conducting the im­mune assays. These blood samples were pro­vided by 21st Century. Pending successful completion of these trials, 60 bulls that are producing their first progeny at 21 st Century wil be immune suppressed to mimic the natu­ral immune suppression in cows. These 60 bulls will be ranked for their immune compe­tency. The investigators will then ask produc­ers in Iowa, Wisconsin, and Minnesota, where at least 20 daughters of the 60 bulls will be produced, to record all health problems of the daughters and their herdmates. This project is intended to determine how accurate the rank­ing is for the sires, based on the health prob­lems recorded by producers of about 400 herds. Assuming this undertaking is successful, this will be the first direct application of ranking sires for the health of their daughters on the basis of laboratory tests. The work is being conducted by Al Kack of 21st Century Genet­ics Coop, Kehrli of the NADC, and the princi­pal investigator of the project summarized above. Volume 3 (1994) 80 

Improved disease resistance in dairy cattle: Correlation of health disorders with measures of immune status; and Genetic improvement for disease resistance by identifying sires whose daughters have fewer disease problems

https://dr.lib.iastate.edu/handle/20.500.12876/53230

Improved disease resistance in dairy cattle: Correlation of health disorders with measures of immune status; and Genetic improvement for disease resistance by identifying sires whose daughters have fewer disease problems

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