Tail tip necrosis in Ontario beef feedlot cattle

Studies were performed to establish the prevalence and importance of tail tip necrosis in the southern Ontario beef feedlot industry and to characterize the gross appearance and histopathology of the condition. In a mail survey, 96% of 71 feedlots with slatted floors, but only 5% of 184 feedlots with solid floors, reported a problem with tail tip necrosis from 1982-1986. Treatments reported included antibiotics, amputation of the tail (therapeutic or preventive), and slaughter. Lameness was associated with tail tip necrosis.

A scoring system for severity of necrosis was developed. Repeated inspections revealed that mild lesions were unlikely to progress to more severe stages. Histological alterations such as perivascular edema and hemorrhage, dermal scarring, follicular atrophy, and paucity of leukocytes were compatible with cutaneous ischemia.

Of 441 tails inspected at slaughter plants, 34.5% were affected, with 3.4% involving skin lacerations and infection, and 4.3% amputated before slaughter.

     

Shiga toxin-producing Escherichia coli in the feces of Alberta feedlot cattle

Shiga toxin-producing Escherichia coli (STEC) are a public health concern. Bacterial culture techniques commonly used to detect E. coli O157:H7 will not detect other STEC serotypes. Feces from cattle and other animals are a source of O157:H7 and other pathogenic serotypes of STEC. The objective of this study was to estimate the pen-level prevalence of Shiga toxins and selected STEC serotypes in pre-slaughter feedlot cattle. Composite fecal samples were cultured and a polymerase chain reaction (PCR) was used to detect genes for Shiga toxins (stx1 and stx2) and genes for O157:H7, O111:H8, and O26:H11 serotypes. Evidence of Shiga toxins was found in 23 pens (92%), O157:H7 in 2 (8%), O111:H8 in 5 (20%), and O26:H11 in 20 (80%) of the 25 pens investigated. Although pen-level prevalence estimates for Shiga toxins and non-O157 serotypes seem high relative to O157:H7, further effort is required to determine the human health significance of non-O157 serotypes of STEC in feedlot cattle.     

Characterization of acute interstitial pneumonia in cattle in southern Alberta feedyards

Field data were collected over 2 consecutive years to characterize acute interstitial pneumonia (AIP) in feedyard cattle. Thirty-eight cattle with clinical symptoms of AIP were examined following emergency slaughter; 31 (all heifers) were confirmed to have AIP on the basis of gross and histological lung pathology. The 7 without AIP, plus 17 asymptomatic penmates, were used as contemporary controls. Plasma concentrations of 3-methylindole (3MI) metabolites were higher (P < 0.001) in heifers afflicted with AIP than in the control animals, and concentrations of 3MI mercapturates in the urine were lower (P < 0.007) in affected heifers. Concentrations of 3MI adducts in lung tissue and in microsomal protein did not differ (P > 0.05) between the 2 groups, and 3MI was not detected in ruminal fluid from either group. Total ruminal bacterial numbers and populations of lactobacilli and protozoa were similar (P > 0.05) between the AIP-positive and unafflicted groups, but fewer (P < 0.05) cellulolytic bacteria were present in the positive group. Bovine respiratory syncytial virus antigen was not found in lung tissue from any of the heifers confirmed to have AIP. To our knowledge, this study is the first to implicate 3MI metabolites as having a role in feedyard AIP. Further research is required to determine the factors responsible for the elevation in 3MI adducts in plasma and urine of feedyard cattle afflicted with AIP.     

The relationship of serology and nasal microbiology to pulmonary lesions in feedlot cattle.

A group of 62 beef calves, born and raised in an institutional herd, were transferred at nine months of age to a commercial feedlot where they remained until slaughter seven months later. Clinical, immunological and microbiological monitoring was carried out during this period. No serious clinical illness occurred. One hundred percent seroconversion to bovine virus diarrhea virus took place after introduction of the calves into the feedlot as well as almost complete (59/62) seroconversion to bovine herpesvirus 1, a proportion of which could be related to a single vaccination. Significant increases in recoveries of Mycoplasma spp. from nasal swabs also occurred in the feedlot. At slaughter, the lungs of all animals were recovered and examined for pathological lesions: 23 were completely normal and 39 showed minor histological changes chiefly characterized by areas of lobular to sublobular atelectasis. For this group of calves, no relationship was found between the presence of potential pathogens in nasal mucus and the occurrence of lesions in the lung. The serological results are discussed in terms of vaccinations and other known events that occurred during the study period.     

Prevalence of sucking and chewing lice on cattle entering feedlots in southern Alberta

Beef calves from 2 sources entering southern Alberta feedlots in the winters of 1997-98 and 1998-99, were surveyed for the presence of lice. A random sample of multiple source (MS), that is, auction market-derived, calves entering commercial feedlots and single source (SS) calves entering a backgrounding feedlot were examined for the presence of lice at entry to the feedlot. A standardized examination, which involved hair-part examination of 8 louse predilection sites, was conducted on each selected calf to determine prevalence and intensity of infestation. The long-nosed sucking louse, Linognathus vituli, was the most commonly encountered species. This species infested from 57.8% to 95.6% of the calves selected from both MS and SS calves during both winters. Louse index values, indicating intensity of infestation, for L. vituli ranged from 1 to 243 lice per animal. The chewing louse, Bovicola bovis, was present on MS and SS calves only in the winter of 1998-99. The louse index values for B. bovis ranged from 1 to 230 lice per animal. Mixed infestations of the L. vituli and B. bovis were common. The little blue cattle louse, Solenopotes capillatus, was present only on the SS calves in the winter of 1997-98. The short-nosed sucking louse, Haematopinus eurysternus, was present at very low intensities, 1-2 lice per animal, on 2.6% to 4.4% of the MS calves during both winters. Comparison of results from the current study with published literature suggests that efforts to determine the economic impact of louse infestations are confounded by the lack of a uniform method to assess louse population levels.     

Acute phase proteins in naturally occurring respiratory disease of feedlot cattle

The aim of this study was to evaluate three acute phase proteins (APP) [haptoglobin (HPT), lipopolysaccharide binding protein (LBP) and transferrin (Tf)] in feedlot cattle with naturally occurring respiratory disease diagnosed by a calf health scoring chart (CHSC). Seventy-seven beef calves were observed for signs of Bovine Respiratory Disease (BRD) during the first 28 days after arrival at the feedlot. Fourteen cases and pen matched controls were selected based on the CHSC. BRD cases were defined as a score of ≥5, while controls were defined as a score ≤4. The mean CHSC score in cases was 6.9 which was significantly greater than the controls 2.8 (P < 0.01). Mean plasma LBP and HPT concentrations were significantly greater in cases than controls (P < 0.01). Our study results show that measurement of HPT and LBP could be useful in detecting respiratory disease in feedlot conditions. Transferrin concentrations between the two groups were not statistically different.     

Clinical study of toe ulcer and necrosis of the apex of the distal phalanx in 53 cattle

Clinical signs, causative factors, radiographic findings, type and duration of treatment or reason for killing were evaluated in 53 cattle (mean age: 5.3 years) suffering from toe ulcer and/or apical pedal bone necrosis. A total of 78 claws were affected. Four cattle suffered from a toe ulcer in one claw, 35 cattle showed osteolysis of the apex of the distal phalanx in a single claw and 14 cattle in two or three claws per cow. Overtrimming by means of a grinding disc and/or perforation of the sole was diagnosed as the major cause in 27 cattle (49%), laminitis in 30.2% and traumatic injuries in 11.3%. Radiography revealed a varying degree of osteolysis involving up to two-thirds of the pedal bone. Twenty-one cattle (39.6%) showing multiple toe disorders or involvement of one single claw with concurrent internal diseases were destroyed. In 23 cattle, the osteolytic bone was resected using a bone curette or hammer and chisel. Of these, the treatment was successful in 20 animals. The healing period ranged from 16-60 days when one claw was affected and from 43-53 days when two claws were affected. In five cattle, the digit was amputated.     

Laminitis-like changes in the claws of feedlot cattle

The purpose of this study was to observe and quantitate changes in the claws of two groups of feedlot cattle (calves and backgrounded yearlings) fed diets that varied in energy (73.5 or 78.5% TDN) and crude protein (11, 13, 15, 16, 17, or 19%) content. At slaughter, the thickness of sole horn and the prevalence of toe and heel hemorrhages were greater in calves than in yearlings (p<0.02). Feeding the high-energy ration increased the prevalence of toe and heel hemorrhages in calves (p<0.02) and heel hemorrhages in yearlings (p<0.02). In yearlings, rotation of the distal phalanx and ridging of the dorsal wall of the claw were the most prominent pathological features. Osteopathy of the apex of the distal phalanx occurred more frequently in calves than in yearlings (p<0.01). This study suggests that intensive feeding of beef cattle before they reach 14 months of age has a deleterious effect on digital health.     

Determination of the seroprevalence of Neospora caninum in feedlot steers in Alberta

A study was conducted in Alberta to determine the seroprevalence of Neospora caninum in feedlot calves purchased from various auction markets throughout western Canada. Four feedlots (1 feedlot from each of the Airdrie and High River areas and 2 feedlots from the Strathmore area) were selected for sampling. At each feedlot, a random 10% sample of feedlot steer and bull calves entering the feedlot from September 2001 to December 2001 were enrolled in the study until there were a maximum of 500 animals enrolled per feedlot. Blood samples were collected from 1976 male animals at the time of entry to the 4 study feedlots. The animals represented 375 groups purchased from 70 sale points throughout British Columbia, Alberta, Saskatchewan, and Manitoba. Of the 1976 animals tested, 128 animals tested positive for antibodies to N. caninum. The prevalence and adjusted 95% confidence limits for N. caninum in beef calves on entrance to the feedlot in western Canada were 6.5% (95% CI, 5.1 to 8.2). There were no significant (P > or = 0.05) associations between the risk of treatment, the risk of designation as "chronic," and the risk of death and antibodies to N. caninum either before or after adjusting for feedlot, entry weight, entry date, and clustering of disease within lots at each feedlot. In addition, there was no significant (P > or = 0.05) association between serological status and feedlot entry weight or average daily gain. Note that there was no information available on feed conversion because the calves were mixed within existing commercial feedlot pens and the actual feed intake of each animal could not be determined. Adjustment for the concentration of antibodies to bovine viral diarrhea virus on arrival did not change any of the examined associations between N. caninum status and calf health or performance. The results of this study demonstrated that the prevalence of N. caninum in feedlot calves in western Canada was less than the prevalence reported in the United States. Additional studies are required to determine whether the inferior rate of gain and feed efficiency observed in the southern United States with animals testing positive for antibodies to N. caninum also occurs under the management conditions used in western Canada.     

The prevalence of methicillin-resistant Staphylococcus aureus colonization in feedlot cattle

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen and recent evidence has implicated food animals in the epidemiology of human infections in some regions. While the role of food in MRSA transmission and human health relevance are unclear, MRSA can be found in retail meat products internationally, including beef, yet there has been minimal investigation of MRSA in beef cattle. This study involved screening feedlot cattle for nasal and gastrointestinal colonization with MRSA shortly before the time of slaughter. Methicillin-resistant S. aureus was not isolated from any of 491 nasal swabs and 488 faecal samples. This finding is in contrast to studies that have isolated MRSA from retail beef in Canada, performed in the same laboratory using comparable culture techniques. The reason for this discrepancy is unclear but it demonstrates that further study of MRSA in livestock as well as slaughter, processing and retail environments is needed to elucidate the epidemiology of MRSA contamination of meat.     

Six novel gammaherpesviruses of Afrotheria provide insight into the early divergence of the Gammaherpesvirinae

The Afrotheria represent an early branching of placental mammals. Only two herpesviruses from Afrotheria have been previously identified, and the genus Proboscivirus in the subfamily Betaherpesvirinae has been proposed for them. Six novel gammaherpesviruses were identified in four species in the superorder Afrotheria by detection and analysis of their DNA polymerase genes. Elephantid herpesvirus 3 (ElHV3) and Elephantid herpesvirus 4 (ElHV4) were identified from conjunctival swabs from Asian elephants (Elephas maximus). ElHV3 was also found in a vaginal swab from one elephant with vaginitis. Elephantid herpesvirus 5 (ElHV5) was identified from vaginal swabs of two Asian elephants with vaginal plaques. Elephantid herpesvirus 6 was discovered in a conjunctival swab from an African elephant (Loxodonta africana). Procavid herpesvirus 1 (PrHV1) was found in spleen and conjunctival swabs of rock hyrax (Procavia capensis). Trichechid herpesvirus 1 (TrHV1) was identified from skin and buffy coats of Florida manatees (Trichechus manatus latirostris). ElHV3 and ElHV4 form a distinct cluster, and ElHV5, ElHV6, TrHV1, and PrHV1 form a second cluster. These viruses may have codiverged with their host species. Phylogenetic analysis of these novel herpesviruses suggests that two separate groups of gammaherpesviruses may have codiverged with the Afrotheria.     

Risk factors for lower respiratory tract disease in a cohort of feedlot cattle

Using data collected from company lot records, potential risk factors related to feedlot management, the cattle, and climate were determined. The risk factors were analyzed by use of weighted multiple regression techniques to determine their effects on the incidence of lower respiratory tract disease in a cohort of 95 lots containing 17,696 cattle. The gender of the cattle, the number of days that groups of cattle filled a lot, pregnancy checking of heifers, and the average temperature change in the first 14 days in which the cattle were on feed significantly influenced the incidence of lower respiratory disease. The incidence of lower respiratory tract disease was most influenced by risk factors in the first 30 days on feed.     

Double-yolked pheasant eggs provide an insight into the control of albumen secretion in bird eggs

1. The possible role of the presence of the yolk in stimulating secretion of albumen was investigated. 2. Double-yolked and single-yolked pheasant (Phasianus colchinus) eggs were opened to determine the masses of the shell, albumen and yolk(s). 3. In double-yolked eggs, the two yolk masses were not significantly different. Albumen mass was increased above that expected from an egg with a single-yolk of comparable size but below that expected from an egg having a mass of the combined yolks. The mass of shell per unit area reflected the mass of the initial mass of the egg irrespective of the number of yolks. 4. The additional mass of albumen is unrelated to yolk or initial egg mass. It is postulated that in double-yolked eggs the oviduct is mechanically stimulated by the presence of both yolks, which empties the stores of water-soluble albumen proteins in the magnum wall. Such stores are insufficient to provide the same amount of protein for the two yolks.     

Presence of non-O157 Shiga toxin-producing Escherichia coli in feces from feedlot cattle in Alberta and absence on corresponding beef carcasses.

The study objectives were to determine the prevalence and serotypes of non-O157 Shiga toxin-producing Escherichia coli (STEC) in pens of feedlot cattle and on corresponding beef carcasses. We collected 25 fecal samples from 84 pens in 21 Alberta feedlots and 40 carcass swabs from each preslaughter pen for analysis by culture and polymerase chain reaction (PCR). Non-O157 STEC were recovered from feces from 12 (14%) of the 84 pens and 12 (57%) of the 21 feedlots by examination of 1 E. coli isolate positive for 4-methylumbelliferyl-beta-beta-glucuronide per sample. Twelve non-O157 serotypes were detected, but 7 of the 15 STEC isolates lacked the accessory virulence genes eae and hlyA. Although 115 (7%) of the carcass broths were PCR-positive, no STEC isolates were recovered from the 1650 carcasses sampled. Our data indicate that multiple non-O157 STEC serotypes may be present in cattle feces, yet are unlikely to be recovered from the corresponding beef carcasses when 20 colonies per sample from PCR-positive broth cultures are analyzed.     

Incorporation of thymol into corncob granules for reduction of odor and pathogens in feedlot cattle waste

Confined animal feeding operations can be a source of odor emissions, global warming gases, water pollution, and food contamination. Laboratory studies have indicated that plant oils with antimicrobial activity can be used to control pathogens and odor emissions from cattle and swine wastes. However, these oils are aromatic and may volatilize when applied topically. Our objectives were to evaluate the volatility of thymol from a feedlot surface and the effectiveness of topically applying thyme oil (2.5% thymol), incorporated into corncob granules and added once per week, to control odor emissions and total coliforms in feedlot manure. In the first study, thymol either volatilized or was degraded within 28 d after topical application. In a second study, thyme oil (2.5% thymol) was incorporated into corncobs and applied to pen surfaces weekly. Manure samples from 6 locations in each pen were collected from 3 untreated and 3 thymol-corncob-treated pens (15 x 150 m; fifty 400-kg cattle/pen), 3 times per week for 8 wk. Samples were analyzed for thymol concentration, total VFA, branched-chain VFA, aromatic compounds, and the number of Escherichia coli and total coliform bacteria. Over the 8 wk, with the exception of wk 7, the desired thymol concentration of 15 to 20 micromol/g DM was maintained in the manure. Concentrations of VFA and branched chain-VFA increased over time in untreated and treated pens. However, the rate of VFA accumulation in treated pens (7.5 +/- 1.3 micromol.g DM(-1).wk(-1)) was less (P < 0.01) than the rate of accumulation in untreated pens (18.0 +/- 2.1 micromol.g DM(-1).wk(-1)). Likewise, the rate of branched-chain VFA accumulation in treated pens (0.31 +/- 0.04 micromol.g DM(-1).wk(-1)) was less (P < 0.01) than in untreated pens (0.55 +/- 0.06 micromol.g DM(-1).wk(1)). The concentrations of E. coli in treated pens (2.9 +/- 1.2 x 10(5) cfu.g DM(-1)) were 91% less (P < 0.04) than in untreated pens (31.1 +/- 4.0 x 10(5) cfu.g DM(-1)). Similarly, concentrations of coliforms in treated pens (3.7 +/- 1.3 x 10(5) cfu.g DM(-1)) were 89% less (P < 0.04) than those of untreated pens (35.3 +/- 4.2 x 10(5) cfu.g DM(-1)). These results indicate that odor emissions and total coliforms can be reduced in feedlot manure with a once per week application of thymol incorporated in a granular form. However, corncobs are bulky, and other granular carriers with a greater carrying capacity for thyme oil should be explored.