Assessing performance of feedlot operations using epidemiology.

The progressive feedlot veterinarian must be well versed not only in individual production animal medicine, but also in population-based medicine. Feedlot health programs must be goal oriented, and evaluation of these goals is accomplished through diligent use of record systems and analytic evaluation of these record systems. Basic feedlot monitoring parameters include health and economic parameters in addition to the use of bench marking parameters between and among feed yards. When these parameters have significant changes, steps should be initiated to begin field investigations. Feedlot epidemiology uses several novel applications such as partial budgeting, risk assessment, and packing plant audits to provide scientifically sound and economically feasible solutions for the feeding industry.     

Prevention of lameness in cow-calf operations.

Lameness is a significant cause of economic loss, premature culling, and loss of genetics in cow-calf operations. In recent years, attention to treatment and prevention of lameness has increased. Veterinarians must be aware of factors associated with lameness such as genetics, environment, and nutrition so that preventive measures can be instituted in consultation with ranchers.     

Management of mineral supplementation programs for cow-calf operations.

Wasting diseases, hair loss, depigmented hair, skin disorders, noninfectious abortion, diarrhea, loss of appetite, bone abnormalities, tetany, low fertility, and pica have all been attributed to dietary mineral deficiencies or excesses in beef cattle diets. When discussing the mineral nutrition of beef cattle, it is common to focus on readily observable problems such as these. It is a fact, however, that the probability of a particular beef operation ever encountering one of these classical symptoms of deficiency or excess is vanishingly small. Most economic losses associated with mineral nutrition stem from less obvious circumstances (ie, sub-clinical deficiencies or toxicities). Problems with animal health or performance are frequently the result of interaction between one or more minerals in the diet and not due to deficiency or excess per se. Even more likely to cause economic harm is a mineral supplementation program that is mismanaged or overpriced. This article will attempt to distinguish between facts and perceptions regarding mineral nutrition of beef cattle and to make suggestions on cost effective supplementation practices.     

Breed effects on crossbred cow-calf performance

Effects of seven breeds of cow's sire and 12 breeds of cow's maternal grandsire on preweaning performance of crossbred cows and their calves were examined in data from two experiments conducted at the Roman L. Hruska U.S. Mean Animal Research Center. Data included 1,836 records over three to five parities for 516 cows by 143 sires and by 307 maternal grandsires. The statistical model fitted effects of calf sex, parity, cow birth-breeding year or cow-calf birth year, the breed effects and their interactions. Deviations of breed of sire or equivalent grandsire effects on each trait from the mean for Hereford x Angus cows ranged from -1.6 to 5.5 kg (P less than .001) for calf birth weights, -15 to 1% (P less than .001) for calving difficulty, nonsignificant for preweaning calf mortality and -2 to 27 kg (P less than .001) for calf weaning weight. Deviations were nonsignificant for conception rate and calves weaned per cow exposed to breeding, but -2 to 40 kg (P less than .001) for calf weight weaned per cow exposed for breeding, -7 to 78 kg (P less than .001) for cow weight and -20 to 2% (P less than .001) for body condition score. The advantages of Holstein and Brahman cross over Hereford x Angus cows of 23 and 13% in weight of calf weaned/cow-breeding exposure must be compared with the expected greater feed requirements from 7 or 8% heavier cows and at least 50% higher milk production, which emphasizes the need to include input measures and costs in breed evaluation schemes.     

Aspects of the epidemiology of nematode infections in a cow-calf herd in Ontario.

On May 29, 1980, 108 cows and calves were placed on a 20 hectare pasture until October 26, except that from September 18 to October 2 they were in a barn. Every two weeks during the total period, fecal samples were taken from 17 cows and 14 calves and herbage samples were collected from the pasture. Parasite fecal egg counts were estimated using the Cornell-Wisconsin centrifugation technique and herbage infective larvae by a modified Sandwich technique. Daily maximum and minimum air temperature and precipitation were recorded. The principal parasite egg found was the trichostrongyle-strongyle morulate, oval-shaped egg referred to as a gastrointestinal nematode (GIN) egg. The mean GIN egg/g of feces for cows varied from 14.2 to 23.9 and for calves it rose from 0.2 in the spring to 134.8 in the fall. Nematodirus, Trichuris, Strongyloides, Moniezia and coccidia were also found. Larvae were recovered first in July, with the greatest number, over 2000/kg of dry weight of herbage, in September and were primarily Cooperia and Ostertagia.     

Beef cow-calf production.

Cow-calf production occurs in all 50 states over varied resource bases and under vastly different environmental conditions. Multiple breeds exist and management styles and objectives are as numerous as the number of cow-calf producers. There is not one area of the country, one breed of cattle, or one management style that is most profitable for producing cows and calves. There are, however, some common strategies that can be employed by cow-calf producers to enhance profitability. Costs need to be controlled without jeopardizing cow herd productivity or net returns. It appears that the cost associated with purchased and harvested feeds varies considerably across operations. Understanding cyclic and seasonal price patterns, weight-price slides, cattle shrink, and other marketing costs can help producers enhance their profit by marketing (and not by just selling) their cattle. Producers with superior cattle genetics can become part of a specific alliance or, at a minimum, document the performance of their cattle so that they can get paid for the superior genetics. The beef industry is changing and will likely continue to change. Cow-calf producers will need to examine their own management practices to determine whether they are optimal for the current industry. Those producers who are most adept at matching their management abilities to their cattle type, their resource base, and the appropriate market outlet will be the most successful in the future.     

Mefluidide effects on smooth brome composition and grazing cow-calf performance

Mefluidide, a plant growth regulator, was evaluated in two cow-calf grazing trials and one herbage trial on smooth brome (Bromus inermis) pastures stocked at recommended densities in eastern Nebraska. Mefluidide-treated pasture increased cow and calf production during August of 1982 (P = .03) and calf production was greater during July of 1983 (P = .09). Mefluidide-treated smooth brome pastures increased calf production over the 1982 grazing season (P = .11) and cow gain over the 1982 (P = .12) and 1983 grazing seasons (P = .13). Mefluidide decreased neutral detergent fiber (NDF) content and increased crude protein content of smooth brome during both years (P less than .05), and increased in vitro dry matter disappearance (IVDMD) in 1982 (P less than .05). In ungrazed smooth brome, mefluidide treatment appeared to shift dry matter production to green leaves from green stem and brown leaf and stem fractions. Cell wall components [NDF, acid detergent fiber (ADF) and lignin] of green leaves were not affected significantly by mefluidide treatment, although green stems treated with mefluidide were lower in ADF and lignin (P less than .05).     

Prevalence of Giardia duodenalis assemblages in weaned cattle on cow-calf operations in the United States

To determine the prevalence of Giardia duodenalis in weaned beef calves on cow-calf operations in the United States, fecal specimens were collected from 819 calves (6-18 months of age) from 49 operations. After cleaning and concentration procedures to maximize recovery of cysts from feces, DNA was extracted from each of the 819 specimens. The presence of G. duodenalis was determined by nested PCR of a fragment of the SSU rRNA gene. All positive PCR products were subjected to sequence analysis. The overall sample level prevalence of Giardia was 33.5% with prevalence ranging from 0 to 100% among operations. The highest within herd prevalence of infected beef calves was found in one cow-calf operation from the South region (100%), followed by a cow-calf operation from the West region (90%), and three cow-calf operations from the Midwest region (87.5, 85, and 85%). Giardia was not detected in samples from 7 operations including 5 cow-calf operations from the South region, and 1 cow-calf operation each from the Midwest and West regions. Molecular analysis of the Giardia-positive samples identified assemblage E (or E-like) in 31.7% of all samples (260/819) and assemblage A in 1.2% (10/819). A mixed infection with assemblages A and E was observed in four calves from an operation in Midwest region. The potentially zoonotic assemblage A was detected in specimens from four operations in Midwest region. These findings indicate that most G. duodenalis found in weaned beef calves was assemblage E which represents no known zoonotic threat. However, the presence of assemblage A in a small number of animals poses a potential risk of infection to humans.     

Culling practices of Ontario cow-calf producers.

This study describes the distribution of herd culling rates for 123 Ontario cow-calf herds maintaining individual animal records. Associations between culling and factors at both the individual and herd level were examined. In addition, the relative importance of individual animal and herd level influences on culling were investigated. The following individual cow culling risk factors: nonpregnancy, age, weaning weight index, calf outcome, abortion, prolapsed vagina, prolapsed uterus, calving injury, lameness and mastitis or udder problems were significantly associated with culling (p less than 0.01). Two herd level factors were associated with increased culling rates: a higher than average proportion of heifers and a shorter than average calving season (p less than 0.01). The proportion of culling variation attributed to individual animal and herd level influences varied with model type. While simple models (one-way ANOVA) indicated that the herd variance component for culling was relatively minor, more complex models indicated larger herd-to-herd variability (mixed model ANOVA). Thus, it appeared that the probability of culling for a cow with a given set of risk factors depended to an important extent on manager decisions in the herd of origin.     

Reproductive performance of a cow-calf herd following a Neospora caninum-associated abortion epidemic

This study examines the long-term impact of a Neospora caninum-associated abortion outbreak in a large cow-calf herd in northern Alberta. Blood samples were collected 4 times from all bred females and heifer calves born during the spring before the outbreak: (1) at the time of the outbreak, (2) the following spring, (3) the subsequent fall, and, finally, (4) the second spring after the outbreak. The samples were analyzed using a commercially available enzyme-linked immunosorbent assay for N. caninum. Calves born immediately following the outbreak were also monitored. Individual calving or abortion records were available from all cows for 2 calving seasons. All cows and heifers were pregnancy tested after the 2 subsequent breeding seasons. At the time of the abortion outbreak in 1997, 81% of all bred females and 87% of the heifer calves were serologically positive. In spring 1998, 49% of the cows and 47% of the heifer calves remained positive. In fall 1998, 48% of the remaining cows and heifers were serologically positive. After the first breeding season following the outbreak (1998), 13.5% of the heifers and 22.2% of the cows were open (not pregnant). Animals that were serologically positive in the spring were more likely to be open in the fall (odds ratio, 2.0; 95% confidence interval, 1.1 to 3.7). No subsequent associations with increased risk of abortion, stillbirth, or nonpregnancy were identified.     

A seroepidemiological study of the importance in cow-calf pairs of respiratory and enteric viruses in beef operations from northwestern Quebec.

Serum antibody analyses for bovine herpesvirus type 1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine coronavirus (BCV), and bovine rotavirus (BRV) were performed on 527 randomly selected cows, before calving, and on 407 three-week-old calves. In cows and calves, BCV and BRV were the most seroprevalent viruses (80% to 100% according to virus and vaccination status). Bovine respiratory syncytial virus was the least seroprevalent in the cows, independent of the vaccination status. In nonvaccinated cows the seroprevalence to BRSV was 36.7%, and 53.5% in cows vaccinated less than two weeks prior to collecting blood, and 67.6% in cows vaccinated two weeks or more prior to blood collection. In their calves, BHV-1 was the least seroprevalent, independent of the vaccination status. The serological status and antibody titers in calves were generally associated with those of the dam. The occurrence of respiratory diseases in the calves was associated with cow and calf serological profiles (BHV-1, BRSV and BCV in the nonvaccinated group, BHV-1, BVDV and BCV in the vaccinated group). The occurrence of diarrhea was not associated with cow and calf serological profiles but was negatively associated with high level calf serum IgG in the nonvaccinated group (odds ratio = 0.73). Bovine coronavirus and BRV were shed by 1.4% and 4.9% of calves in the nonvaccinated group, and by 0% and 9.9% of calves in the vaccinated group, respectively. Bovine rotavirus shedding was associated with fecal diarrheic consistency at the moment of fecal sampling but not with previous occurrence of diarrhea.     

Effectiveness of current anthelmintic treatment programs on reducing fecal egg counts in United States cow-calf operations

During the United States Department of Agriculture (USDA) National Animal Health Monitoring System’s (NAHMS) 2007–2008 beef study, producers from 24 states were offered the opportunity to evaluate their animals for internal parasites and for overall responses to treatment with anthelmintics. A lapse of 45 d was required between initial sampling and any previous treatments. Choice of anthelmintic (oral benzimidazoles, and both injectable and pour-on endectocides) was at the discretion of the producer so as not to alter the local control programs. Fresh fecal samples were collected from 20 animals, or from the entire group if less than 20, then randomly assigned to 1 of 3 participating laboratories for examination. Analyses consisted of double centrifugation flotation followed by enumeration of strongyle, Nematodirus, and Trichuris eggs (the presence of coccidian oocysts and tapeworm eggs was also noted). Where strongyle eggs per gram (epg) exceeded 30, aliquots from 2 to 6 animals were pooled for egg isolation and polymerase chain reaction (PCR) analysis for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. Results from 72 producers (19 States) indicated that fecal egg count reductions were < 90% in 1/3 of the operations. All operations exhibiting less than a 90% reduction had used pour-on macrocyclic lactones as the anthelmintic treatment. While some of these less than expected reductions could have been the result of improper drug application, PCR analyses of the parasite populations surviving treatment, coupled with follow-up studies at a limited number of sites, indicated that less than expected reductions were most likely due to anthelmintic resistance in Cooperia spp. and possibly Haemonchus spp.     

Comparison of three weaning ages on cow-calf performance and steer carcass traits

An experiment was conducted to compare three weaning ages on cow-calf performance and steer carcass traits. Crossbred steers (n = 168; 1/2 Simmental x 1/4 Angus x 1/4 Hereford) were randomly assigned to three treatments with eight pens per treatment: groups were 1) weaned at an average of 90 d of age (90 +/- 13 d) and placed in the feedlot, 2) weaned at an average of 152 d of age (152 +/- 13 d) and placed in the feedlot, and 3) weaned at an average of 215 d of age (215 +/- 13 d) and placed in the feedlot. The number of days steers were finished decreased by 55 and 38 d (linear, P = .0001) as weaning age increased when slaughtered at a constant fat end point (.81 cm). Weaning at an average of 90 and 152 d of age improved overall ADG by .15 and .07 kg/d, respectively, over weaning at an average of 215 d of age (linear, P = .005). Over the entire finishing period, intake increased (linear, P = .0006) and efficiency was poorer (linear, P = .004) as weaning age increased. Owing to differences in finishing days and intake, total concentrate consumed increased (linear, P = .03) as weaning age decreased. No differences (P > .21) were observed for carcass weight, longissimus muscle area, or yield grade. No differences (P > .19) were observed in marbling score or percentage of steers grading greater than or equal to Choice or Average Choice. Cow body condition score improved (linear, P = .0001) as weaning age decreased. Pregnancy rate improved 12 percentage units (linear, P = .15) for cows on the 90-d weaning treatment. In this study, early weaning improved gain and feed efficiency, but it increased total concentrate consumed.     

Patterns of stillbirth and dystocia in Ontario cow-calf herds.

The association between a number of individual animal and herd level factors and calving problems in beef cows and heifers were examined. Data were from the 1987 calving season for a subset of 123 herds which maintained individual-animal records, from a sample of 180 randomly selected Ontario cow-calf herds. The median herd dystocia rate was 5.8% and 24.4% of herds had no dystocias. The median herd stillbirth rate was 2.8%, and 33.3% of herds had no stillbirths. Dystocias and stillbirths were much more common in heifers than in cows. Separate statistical models of dystocia and stillbirth for cows and heifers were created. Dystocia in cows was associated with calf sex, previous calving assistance and large breed type and birth weight. Variations in 1987 cow herd dystocia rates were associated with calving season, location and density, and the herd dystocia rate in 1986. Dystocia in heifers was associated with large breed type and calf birth weight. Herd-level management practices associated with increased heifer dystocia rates included breeding heifers to calve earlier than cows and rearing heifers together with the cow herd. Stillbirths for both cows and heifers were associated with calving assistance, particularly hard assistance. Herd-level management and other factors were unassociated with stillbirths.     

High prevalence of Cryptosporidium bovis and the deer-like genotype in calves compared to mature cows in beef cow-calf operations

Recent studies have identified the novel, host adapted Cryptosporidium bovis and the deer-like genotype in dairy cattle from farms in the United States, China, India and Europe. This novel species and genotype appear to be more prevalent in older, post-weaned dairy cattle than previously thought. However, little information is available on their prevalence in beef cow-calf operations. In the present study, we determined the prevalence of Cryptosporidium species in 98 calves (6-8 months old) and 114 cows (>2 years old) in seven beef cow-calf herds in western North Dakota. DNA was extracted from fecal samples and Cryptosporidium spp. were identified by amplification of the 18S rRNA gene followed by sequencing or RFLP analysis. All seven herds tested positive for Cryptosporidium. Overall, 43/212 (20.3%) animals were positive. Only five of these positives were from cows. C. bovis, the deer-like genotype and C. andersoni were identified in 9.4, 6.6 and 1.4% of animals sampled, respectively. C. parvum was not identified in any of the positive samples. C. bovis, the deer-like genotype and C. andersoni were detected in 6/7, 5/7 and 2/7 herds, respectively. C. bovis and the deer-like genotype were primarily detected in calves, while C. andersoni was only detected in cows. Six isolates could not be typed. These results show a relatively high prevalence of C. bovis and the deer-like genotype in 6-8-month-old beef calves compared to cows older than 2 years in the seven herds studied.     

Occurrence of Mycobacterium avium subspecies paratuberculosis and Neospora caninum in Alberta cow-calf operations

Mycobacterium avium subsp. paratuberculosis (MAP) and Neospora caninum (NC) are two pathogens causing important production limiting diseases in the cattle industry. Significant impacts of MAP and NC have been reported on dairy cattle herds, but little is known about the importance, risk factors and transmission patterns in western Canadian cow-calf herds. In this cross-sectional study, the prevalence of MAP and NC infection in southwest Alberta cow-calf herds was estimated, risk factors for NC were identified, and the reproductive impacts of the two pathogens were assessed.     

Biosecurity practices of beef cow-calf producers

OBJECTIVE: To evaluate biosecurity practices of cow-calf producers. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 2,713 cow-calf operations were used in phase 1 of the study, and 1,190 cow-calf operations were used in phase 2. PROCEDURE: Producers were contacted for a personal interview between Dec 30, 1996 and Feb 3, 1997 regarding their management practices. Noninstitutional operations with 1 or more beef cows were eligible to participate in the study. Producers who participated in the first phase of the study and who had > or = 5 beef cows were requested to continue in the study and were contacted by a veterinarian or animal health technician who administered further questionnaires. All contacts for the second phase of the study were made between Mar 3, 1997 and Apr 30, 1997. Additional data on use of various vaccines, testing of imported cattle for brucellosis, Mycobacterium paratuberculosis, bovine viral diarrhea, and tuberculosis as well as potential for feed contamination were collected during the second phase of the study. RESULTS: Producers commonly engaged in management practices that increased risk of introducing disease to their cattle such as importing cattle, failing to quarantine imported cattle, and communal grazing. Producers inconsistently adjusted for the increased risk of their management practices by increasing the types of vaccines given, increasing the quarantine time or proportion of imported animals quarantined, or increasing testing for various diseases in imported animals. CONCLUSIONS AND CLINICAL RELEVANCE: Cow-calf herds are at risk for disease exposure from outside sources when cattle are introduced to the herd, and producers do not always adjust management practices such as vaccination schedules and quarantine procedures appropriately to minimize this risk. Veterinary involvement in education of producers regarding biosecurity risks and development of rational and economical biosecurity plans is needed.     

A questionnaire on the health, management, and performance of cow-calf herds in Québec.

Questionnaires were mailed to 520 cow-calf producers in Québec in order to compare management practices and herd performance according to herd size (small: < 40 females, or large: > or = 40 females) and in 4 geographic areas for the 1995 calving season. Owners of large herds adopted management practice and preventive measures more often than did owners of small herds. Average calving and weaning rates were 95% and 87% respectively. Average perinatal and preweaning mortality rates were between 4.9% and 5.6%. A greater percentage of owners with large herds than owners of small herds reported diarrhea and pneumonia problems. Among large herds, the number of herds experiencing pneumonia and calf mortality associated with diarrhea tended to be higher in areas of the northwest. Calf mortality due to pneumonia was higher in the northeast. No regional variation was found among small herds. Further research is needed to identify diseases risk factors.     

Impact of trichomoniasis on the cow-calf producer's profitability

Using current knowledge of bovine trichomoniasis, a computer spreadsheet simulation model was developed to contribute to the understanding of the disease dynamics and the disease's impact on calf crop, weaner calf production, and revenue returns. Two disease prevalence simulations were generated with the model. In each simulation, 200 susceptible cows were confined with 5 fertile bulls. In simulation 1, one bull was infected with Tritrichomonas foetus (prevalence, 20%); in simulation 2, 2 bulls were infected (prevalence, 40%). The remaining bulls in these groups were designated noninfected. The disease simulation outcomes for breeding and calving variables were compared with a similar but noninfected model group, simulation 0. The disease model predicted a reduction of 14 to 50% in annual calf crop, a prolonged breeding season, a reduction of 5 to 12% in the suckling/growing period, a reduction of 4 to 10% in pounds of marketable calf crop at weaning, a reduction of 4 to 10% in monetary return per calf born, and a substantial reduction of 5 to 35% in the return per cow confined with a fertile bull.