US Cattle Research Articles

Anthelmintic resistance in cattle nematodes in the US

The first documented case of macrocyclic lactone resistance in gastrointestinal (GI) nematodes of cattle was seen in the US approximately 10 years ago. Since that time the increase incidence of anthelmintic resistance has continued at an alarming rate. Currently parasites of the genera Cooperia and/or Haemonchus resistant to generic or brand-name macrocyclic lactones have be demonstrated in more than half of all operations examined. Both of these parasite genera are capable of causing economic losses by decreasing food intake and subsequently animal productivity. Currently, there are no easy and quick means to detect anthelmintic resistant GI nematodes. Definitive identification requires killing of cattle. The most commonly used field detection method is the fecal egg count reduction test (FECRT). This method can be adapted for use as a screening agent for Veterinarians and producers to identify less than desired clearance of the parasites after anthelmintic treatment. Further studies can then define the reasons for persistence of the egg counts. The appearance of anthelmintic resistance is largely due to the development of very effective nematode control programs that have significantly improved the productivity of the US cattle industry, but at the same time has placed a high level of selective pressure on the parasite genome. The challenges ahead include the development of programs that control the anthelmintic resistant nematodes but at the same time result in more sustainable parasite control. The goal is to maintain high levels of productivity but to exert less selective pressures on the parasites. One of the most effective means to slow the development of drug resistance is through the simultaneous use of multiple classes of anthelmintics, each of which has a different mode of action. Reduction of the selective pressure on the parasites can be attained through a more targeted approach to drug treatments where the producer's needs are met by selective treatment of different classes of animals and not by blanket treatment at a location. The implementation of such programs will vary by the sector of the industry and the individual site. In general, the feedlot will be the easiest sector for developing of programs, while stocker/backgrounder operations will provide the most challenging problems. A major question that must be addressed is whether it is important that parasite control programs to be sustainable over time, or if the pharmaceutical industry develop new control agents at a rate sufficient to render sustainability unimportant.

Minimum cost to control bovine tuberculosis in cow–calf herds

Bovine tuberculosis (bTB) outbreaks in US cattle herds, while rare, are expensive to control. A stochastic model for bTB control in US cattle herds was adapted to more accurately represent cow–calf herd dynamics and was validated by comparison to 2 reported outbreaks. Control cost calculations were added to the model, which was then optimized to minimize costs for either the farm or the government. The results of the optimization showed that test-and-removal costs were minimized for both farms and the government if only 2 negative whole-herd tests were required to declare a herd free of infection, with a 2–3 month testing interval. However, the optimal testing interval for governments was increased to 2–4 months if the model was constrained to reject control programs leading to an infected herd being declared free of infection. Although farms always preferred test-and-removal to depopulation from a cost standpoint, government costs were lower with depopulation more than half the time in 2 of 8 regions. Global sensitivity analysis showed that indemnity costs were significantly associated with a rise in the cost to the government, and that low replacement rates were responsible for the long time to detection predicted by the model, but that improving the sensitivity of slaughterhouse screening and the probability that a slaughtered animal's herd of origin can be identified would result in faster detection times.

Case–control study of microbiological etiology associated with calf diarrhea

Calf diarrhea is a major economic burden for the US cattle industry. A variety of infectious agents are implicated in calf diarrhea and co-infection of multiple pathogens is not uncommon in diarrheic calves. A case–control study was conducted to assess infectious etiologies associated with calf diarrhea in Midwest cattle farms. A total of 199 and 245 fecal samples were obtained from diarrheic and healthy calves, respectively, from 165 cattle farms. Samples were tested by a panel of multiplex PCR assays for 11 enteric pathogens: bovine rotavirus group A (BRV-A), bovine coronavirus (BCoV), bovine viral diarrhea virus (BVDV), bovine enterovirus (BEV), bovine norovirus (BNoV), Nebovirus, bovine torovirus (BToV) Salmonella spp. (Salmonella), Escherichia coli (E. coli) K99+, Clostridium perfringens with β toxin gene and Cryptosporidium parvum (C. parvum). The association between diarrhea and detection of each pathogen was analyzed using a multivariate logistic regression model. More than a half of the fecal samples from the diarrheic calves had multiple pathogens. Statistically, BRV-A, BCoV, BNoV, Nebovirus, Salmonella, E. coli K99+, and C. parvum were significantly associated with calf diarrhea (p < 0.05). Among them, C. parvum and BRV-A were considered to be the most common enteric pathogens for calf diarrhea with high detection frequency (33.7% and 27.1%) and strong odds ratio (173 and 79.9). Unexpectedly BNoV (OR = 2.0) and Nebovirus (OR = 16.7) were identified with high frequency in diarrheic calves, suggesting these viruses may have a significant contribution to calf diarrhea.

Long-Term Climate Sensitivity of Grazer Performance: A Cross-Site Study

Climate change will affect grasslands in a number of ways, but the consequences of a warmer, drier world for grazers is uncertain. Predicting future grazer performance is complex since climate change affects both the quantity and quality of forage through a combination of processes that occur over a range of time scales. To better predict the consequences of climate change for grazer performance, a dataset was compiled of over a quarter million bison weights distributed across 22 US herds that span a large range of climates. Patterns of bison body mass among sites, age classes, and sexes were analyzed with respect to differences in geographic patterns of climate and interannual variation in climate. While short-term effects of climate variability are likely to depend on the magnitude and timing of precipitation during the year, grazers will be negatively affected by sustained hotter, drier conditions most likely associated with reductions in forage quality. Short-term, little effect of high temperatures on bison performance is observed, which suggests that the long-term effects of higher temperatures are likely to accrue over time as nitrogen availability in grasslands is reduced and forage quality declines. If relationships observed for bison are general for cattle, the economic consequences of higher temperatures due to decreased weight gain in US cattle could be on the order of US$1B per 1°C increase in temperature. Long-term monitoring of forage quality as well as native and domesticated grazer performance is recommended to better understand climate change effects on grazers.

Evaluation of BTA1 and BTA5 QTL Regions for Growth and Carcass Traits in American and Korean Cattle.

Previously identified QTL regions on BTA1 and BTA5 were investigated to validate the QTL regions and to identify candidate genes for growth and carcass traits in commercial cattle populations from the USA and Korea. Initially, a total of 8 polymorphic microsatellite (MS) markers in the BTA1 and 5 QTL regions were used for Chi-square tests to compare the frequencies of individual alleles between high and low phenotypic groups for the US (Michigan Cattleman’s Association/Michigan State University; MCA/MSU) cattle. For a subsequent study, 24 candidate genes containing missense mutations and located within the QTL regions based on bovine genome sequence data were analyzed for genotyping in the two commercial cattle populations. Re-sequencing analyses confirmed 18 public missense SNPs and identified 9 new SNPs. Seventeen of these SNPs were used for genotyping of the MCA/MSU cattle (n = 98) and Korean native cattle (n = 323). On BTA1, UPK1B, HRG, and MAGEF1 polymorphisms residing between BM1312 and BMS4048 were significantly associated with growth and carcass traits in one or both of the MCA/MSU and Korean populations. On BTA5, ABCD2, IL22 and SNRPF polymorphisms residing between BL4 and BR2936 were associated with marbling and backfat traits in one or both of the MCA/MSU and Korean cattle populations. These results suggested that BTA 1 and 5 QTL regions may be segregating in both Korean Hanwoo and USA commercial cattle populations and DNA markers tested in this study may contribute to the identification of positional candidate genes for marker-assisted selection programs.

Evaluation of an alternative method of herd classification for infection with paratuberculosis in cattle herds in the United States

To develop a better system for classification of herd infection status for paratuberculosis (Johne's disease [JD]) in US cattle herds on the basis of the risk of potential transmission of Mycobacterium avium subsp paratubeculosis. Simulated data for herd size and within-herd prevalence; sensitivity and specificity for test methods obtained from consensus-based estimates. Interrelationships among variables influencing interpretation and classification of herd infection status for JD were evaluated by use of simulated data for various herd sizes, true within-herd prevalences, and sampling and testing methods. The probability of finding ≥ 1 infected animal in herds was estimated for various testing methods and sample sizes by use of hypergeometric random sampling. 2 main components were required for the new herd JD classification system: the probability of detection of infection determined on the basis of test results from a sample of animals and the maximum detected number of animals with positive test results. Tables were constructed of the estimated probability of detection of infection, and the maximum number of cattle with positive test results or fecal pools with positive culture results with 95% confidence for classification of herd JD infection status were plotted. Herd risk for JD was categorized on the basis of 95% confidence that the true within-herd prevalence was ≤ 15%, ≤ 10%, ≤ 5%, or ≤ 2%. Analysis of the findings indicated that a scientifically rigorous and transparent herd classification system for JD in cattle is feasible.

First long-term, direct measurements of evapotranspiration and surface water balance in the Nebraska SandHills

The Nebraska SandHills is a vast grassland ecoregion that also serves as the main recharge zone for the High Plains (Ogallala) aquifer. Despite the national importance of this region in supplying irrigation water and supporting the US cattle industry, there have, until now, been no long-term, direct measurements of the components of the surface water balance. We have addressed this issue by installing energy balance/Bowen ratio (EBBR) flux towers in three key ecosystems. We report here the results of 7 years of measurements and interpret them in terms of annual weather variability. Additionally, these data have allowed us to make first-order estimates of the recharge rate to the aquifer. We found that the three ecosystems behave in very different ways, and that, in a first-order estimate, the region provides approximately 115±20mm year−1 of recharge to the aquifer over the 2003–2009 period.

Tracing the origins of Mycobacterium bovis tuberculosis in humans in the USA to cattle in Mexico using spoligotyping

ObjectivesTo compare genotypes of Mycobacterium bovis strains from humans in Southern California with genotypes of M. bovis strains in cattle in Mexico and the USA to explore the possible origins of human infections. MethodsWe conducted a descriptive analysis of M. bovis genotypes from a binational population of humans and cattle using spacer oligonucleotide typing (spoligotyping). ResultsOne hundred six human M. bovis spoligotypes were compared to spoligotypes from 496 Mexican cattle and 219 US cattle. Twelve spoligotype patterns were identified among human cases and 126 spoligotype patterns were detected in cattle. Over 91% (97/106) of the human M. bovis isolates had spoligotypes that were identical to those found in Mexican cattle. Four human cases had spoligotypes that matched both cattle born in Mexico and in the USA. Nine human cases had spoligotypes that did not match cattle born in Mexico or the USA. ConclusionsOur data indicate that the population of M. bovis strains causing human TB disease in Southern California is closely related to the M. bovis strain population found in Mexican cattle and supports existing epidemiological evidence that human M. bovis disease in San Diego likely originated from Mexican cattle.

Development of breed identification markers based on a bovine 50K SNP array

In Japan, Japanese Black and Holstein cattle are appreciated as popular sources of meat, and imported beef from Australia and the United States is also in demand in the meat industry. Since the BSE outbreak, the problem of false sales has arisen: imported beef has sometimes been mislabeled as domestic beef due to consumer concerns. A method is needed to correctly discriminate between Japanese and imported cattle for food safety. The objective of this study was to develop breed discrimination markers between Japanese and US cattle using a 50K SNP array. As a result, five US-specific markers (BISNP7, BISNP15, BISNP21, BISNP23, and BISNP26) were developed with allelic frequencies that ranged from 0.102 (BISNP15) to 0.250 (BISNP7) and averaged 0.184. The combined use of the five markers would permit discrimination between Japanese and US cattle with a probability of identification of 0.858. This result indicates the potential of the bovine 50K SNP array as a powerful tool for developing breed identification markers. These markers would contribute to the prevention of falsified beef displays in Japan.

Overcoming Obstacles to the Canada-Korea Free Trade Agreement – The Beef Issue

This paper reviews the WTO beef dispute between Canada and Korea against the background of the stalled bilateral negotiations towards a free trade agreement, the free trade agreement that Korea has signed with the United States, and importantly the resumption of Korean beef imports from the United States and the Korean public reaction thereto. The paper argues that, given the deep integration of North American beef production and the essentially identical nature of the Canadian and US cattle herds, farming practices and regulatory systems, once Korea opened up its beef market to imports from the United States pursuant to the US-Korea FTA (including beef and beef products from Canadian feeder cattle if they are fed in the United States for 100 days prior to slaughter), there were no plausible grounds to maintain the ban on imports directly from Canada. The WTO panel is likely to reach the same conclusion. The same reality of a deeply integrated North American beef production system and the similarity of the Canadian and US products means that the economic impacts of the ban on Korean beef production are relatively muted: by far the closest substitute in the Korean beef market for Canadian beef would be the imports from other countries, most notably the United States. Accordingly, there are not likely to be tangible benefits for Korea either on human health grounds or in terms of protection for its beef sector in maintaining the ban.

A review of bovine spongiform encephalopathy and its management in Canada and the USA

Geographic proximity and a long history of integration between US and Canadian cattle industries have resulted in similar management of BSE risk factors. Both countries have had a single imported case of BSE followed by multiple endemic cases of the bovine disease. Comparable risk management strategies have been put in place, such as a ban on the feeding of ruminant materials to other ruminants, a ban on the use of specified risk materials in human and animal feed, and targeted import policies designed to limit the possibility of introduction and propagation of BSE to and within the domestic cattle herd. Despite these similarities, Canada has had experienced a much greater economic challenge than the US in response to BSE due to its higher reliance on beef and cattle exports and the greater number of BSE cases detected within the country.

Effect of Oral Flunixin Meglumine on Heart Rate, Physical Activity, and Salivary Cortisol Concentration following Cautery Disbudding of Dairy Calves

US dairy calves are often disbudded at an early age without analgesics, whereas several other countries require analgesics. Administration of nonsteroidal antiinflammatory drugs (NSAIDs) in milk replacer would be a simple, stress-free method to deliver analgesics for disbudding if shown to improve well-being. Most studies of NSAID efficacy involve older animals, NSAIDs not labeled for use in US cattle, or NSAIDs administered by injection. Our objective was to determine the effects of administering an NSAID labeled for use in US cattle (flunixin meglumine; FM) in milk replacer on heart rate (HR), physical activity (PA), and salivary cortisol concentration (SCC) in young dairy calves disbudded by cautery.

Parasite Resistance in US Cattle

Parasite resistance to the macrocyclic lactones (ivermectin, doramectin, eprinomectin, and moxidectin) is receiving considerable attention in the US cattle industry at a time when the economics of parasitism constitute one of the most important factors involved in beef production. Knowing whether a dewormer is effective is extremely important to an operation. If parasites become resistant to a particular product or product formulation, a serious problem can develop unknowingly unless producers have an easy way to determine product efficacy. The fecal egg count reduction test (FECRT) is a simple test recommended by the American Association of Veterinary Parasitologists (AAVP) as the best way for the practitioner to help producers verify that the dewormer(s) they are using is effective. The FECRT involves conducting a fecal check at the time of treatment and again 14 days following treatment. In the fall of 2007 continuing through the summer of 2008, free lab support was offered to bovine practitioners throughout the US to conduct FECRTs with their clients. This was done according to a standard protocol involving a minimum of 20 samples per treatment group at each collection time. The results are being recorded in a national data base supported by Intervet/Schering-Plough Animal Health and the University of Nevada-Reno. Over 58 veterinary clinics in 19 states have already participated in this program, with over 119 separate tests involving 4,765 samples using a wide range of products and formulations. These data confirm that macrocyclic lactone resistance is widespread and that continued vigilance is required by the veterinary profession, since the problem now appears to be at a critical stage with millions of dollars in production losses at stake.

US feedlots and slaughterhouses: bounding industrial ecology with the extreme case

The potential contribution of Industrial Ecology (IE) to sustainable development, though immense, remains elusive. This is due to the field boundaries whose demarcation lacks specificity. To address the challenge of boundary definition, an agro-industrial complex, the US Cattle Feedlot-Slaughterhouse System (CFSS), has been chosen to illustrate and provoke a discussion about where those boundaries should be set. The selection of the CFSS, a system opposed to the practices usually associated with IE, is justified in the light of the extreme events research methodology. On this basis, the author highlights the many agro-industrial flows among the main CFSS components and then analyses them in terms of their appropriateness for specifying the boundaries of IE.

A review of the biology of bovine herpesvirus type 1 (BHV-1), its role as a cofactor in the bovine respiratory disease complex and development of improved vaccines

Infection of cattle by bovine herpesvirus type 1 (BHV-1) can lead to upper respiratory tract disorders, conjunctivitis, genital disorders and immune suppression. BHV-1-induced immune suppression initiates bovine respiratory disease complex (BRDC), which costs the US cattle industry approximately 3 billion dollars annually. BHV-1 encodes at least three proteins that can inhibit specific arms of the immune system: (i) bICP0 inhibits interferon-dependent transcription, (ii) the UL41.5 protein inhibits CD8+ T-cell recognition of infected cells by preventing trafficking of viral peptides to the surface of the cells and (iii) glycoprotein G is a chemokine-binding protein that prevents homing of lymphocytes to sights of infection. Following acute infection of calves, BHV-1 can also infect and induce high levels of apoptosis of CD4+ T-cells. Consequently, the ability of BHV-1 to impair the immune response can lead to BRDC. Following acute infection, BHV-1 establishes latency in sensory neurons of trigeminal ganglia (TG) and germinal centers of pharyngeal tonsil. Periodically BHV-1 reactivates from latency, virus is shed, and consequently virus transmission occurs. Two viral genes, the latency related gene and ORF-E are abundantly expressed during latency, suggesting that they regulate the latency-reactivation cycle. The ability of BHV-1 to enter permissive cells, infect sensory neurons and promote virus spread from sensory neurons to mucosal surfaces following reactivation from latency is also regulated by several viral glycoproteins. The focus of this review is to summarize the biology of BHV-1 and how this relates to BRDC.

Genotype distribution of the prion protein gene (PRNP) promoter polymorphisms in Korean cattle

Recently, an association between bovine spongiform encephalopathy (BSE) and insertion/deletion (indel) polymorphisms in the bovine prion protein gene (PRNP) promoter region has been reported in German cattle. These PRNP polymorphisms cause changes in PRNP expression and are thought to play an important role in BSE susceptibility. BSE has been reported in British and Japanese Holstein cattle but has not been diagnosed in Hanwoo cattle (Bos taurus coreanae) up to now. These results prompted us to investigate the genotype distributions of these PRNP promoter polymorphisms in 107 Hanwoo cattle and 52 Holstein cattle and compare the results with those of previous studies. A significant difference (P=0.0249) in allele frequency of the 23 bp indel polymorphism was observed between Hanwoo and the BSE-affected German cattle previously investigated. There were no significant differences in the genotype (P=0.2095) or allele (P=0.8875) frequencies of the 12 bp indel polymorphism between Hanwoo and BSE-affected German cattle. Interestingly, the genotype and allele frequencies of the 23 bp indel polymorphism in Korean Holsteins were very similar to those previously reported for BSE-affected German cattle and healthy US cattle sires.

Parameters of Ear Notch Samples for BVDV Testing

Infection with bovine viral diarrhea viruses (BVDV) is a major source of economic loss for the US cattle industry. Houe (2003) estimates that losses in areas where BVD is endemic range between $10 to 40 million per million calvings. Results of serology surveys in the US suggests that our losses are in the upper end of this range (Houe et al, 1995a; Houe et al, 1995b; Paisley et al, 1996). In 2004, 37.6 million calves were born in the US; thus, US losses by this estimate would be between $376 million to 1.5 billion for 2004. The 2005 calf crop was ~37.8 million, making the 2005 estimate very similar to that of 2004.&#x0D; While BVDV infections are well recognized as reproductive pathogens among dairy producers, producers are less aware that BVDV infections are also associated with increased respiratory disease, increased severity of secondary infections and decreased milk production. Persistently infected (PI) animals are the major vectors for spreading BVDV within and among herds. Based on studies of dairies of 100 cows or more, Joly et al (2005) estimated that the presence of one PI animal in a herd resulted in a loss of $1.93/cwt of milk sold. Studies estimate that 10-15% of US herds have at least one PI animal (Houe et al, 1995c; Wittum et al, 2001). In 2004, US dairies produced 170,805 million lb (77,638 kg) of milk. If 10% to 15% of dairy herds have at least one PI animal, then the cost to milk production is between $330 to 494 million per year.&#x0D; Control efforts in the US are geared towards identifying and eliminating Pis. Several tests based on detection of either antigen or viral RNA in blood, serum, bulk milk or skin biopsies are currently in use (Cornish et al, 2005; Fulton et al, 2006). Ear notch samples have become the tissue of choice for screening for PI animals because 1) they are easy to collect; 2) equipment requirements are minimal; 3) they are not affected by presence of passive antibodies; and 4) they can be used as the sample for a wide variety of tests including immunohistochemistry, real-time polymerase chain reaction and antigen-capture ELISA.&#x0D; While ear notches have become one of the samples of choice, there is little information available regarding sample size requirements and stability. Further, while pooling of ear notch samples has been proposed for reducing the cost of surveillance programs (Kennedy et al, 2006), the viral load available for detection from ear notch samples is largely undetermined. The purpose of this study was to establish working parameters for sample size, viral detection limit and sample storage conditions for real-time PCR and antigen-capture ELISA.

Characterization of Bovine Viral Diarrhea Virus (BVDV) Genetics, Antibody Response and Viremia from a Group of BVDV Persistently Infected Calves

Bovine viral diarrhea virus (BVDV) infections cause major problems in the US cattle industry. BVDV persistent infections are the result of fetal infections in the first trimester of pregnancy. Persistently infected animals are a major reservoir of the virus in nature and are extremely efficient at spreading the virus among cattle populations. Understanding the nature of persistent infections and developing diagnostics and surveillance schemes that eliminate PI animals is vital to the control of BVDV. In this study we look at variations in clinical presentation, viral spread, immune response and viral stability in a large group of calves infected with the same BVDV strain.

Recombinant expression of bovine LFA-1 and characterization of its role as a receptor for Mannheimia haemolytica leukotoxin

Mannheimia ( Pasteurella) haemolytica leukotoxin (LktA) is the primary virulence factor contributing to the pathogenesis of lung injury in bovine pneumonic mannheimiosis (BPM), a disease which causes major economic loss to the US cattle industry annually. Recent work from our laboratory using an antibody-based approach has shown that LktA binds to bovine LFA-1 in target cells. While this study suggests that LFA-1 might be a specific receptor, it remains to be conclusively shown that LFA-1 is sufficient to induce susceptibility to LktA. It was of interest to determine if functionally active bovine LFA-1 could be reconstituted on a LFA-1 negative cell line and reconstitute susceptibility to LktA. Here, we report the successful recombinant expression of bovine LFA-1 on the cell surface of the human erythroleukemic K562 cell line. The BoLFA-1 transductant expresses bovine CD18 and CD11a as a heterodimer. We found that LktA binds to both the CD18 and CD11a subunits of BoLFA-1 cells. Exposure of BoLFA-1 cells to LktA, induced tyrosine phosphorylation of the CD18 tail, elevation of intracellular calcium, and cytolysis. This is the first report on recombinant expression of functionally active bovine LFA-1 by transduction into an LktA-non-susceptible human cell line.

Editorial

There is certainly nothing new in saying that inbreeding, the mating of related individuals, has negative consequences in farmed animal populations. Inbreeding leads to loss of genetic variation and most importantly to reductions in performance (i.e. inbreeding depression) particularly in traits related with fitness such as fertility and viability. Reductions in fitness traits can eventually make further progress imposible despite the presence of genetic variance. Even large populations are experiencing large increases in the rates at which inbreeding accumulates. Examples include US and UK Holstein dairy cattle populations where the worldwide use of few elite sires is leading to current rates much higher than those observed in the past and where deteriorations in health and reproductive traits have been observed. Broadening the breeding objectives for livestock species (Simm et al., 2001) would alleviate this but still effective methods for controlling inbreeding need to be applied.