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PubMed2006

A nationwide survey on seroprevalence of Neospora caninum infection in beef cattle in Uruguay.

Bovine abortions due to Neospora caninum infection have been reported worldwide and its economic impact on the beef industry has been acknowledged as a problem. Uruguay has the largest export value of beef per acre in South America. However, no data on the prevalence of N. caninum infection have been available in this country. The objective of this study was to estimate the prevalence and distribution of N. caninum infection in beef cattle in Uruguay through a nationwide survey. A two stage sampling design was used with farms being selected in stage one and animals being selected in stage two. A brief questionnaire was administered on each farm. Seroprevalence of N. caninum in 4444 beef cattle from 229 farms in all the counties, except Montevideo, of Uruguay was determined by an ELISA. The data were then analyzed to identify associations between infection and variables such as type of animal (cow or heifer), herd size, use of veterinary advice, productivity of the soil in relation to the national average, use of improved grass, use of mineral salts, use of supplemental feed, and presence of a dog(s) on the farm. The estimated proportion of positive farms for all the beef cattle operations was 69.2% (95% confidence interval [CI], 53.7-84.7). The overall cattle seroprevalence was estimated as 13.9% (95% CI, 11.6-16.3). The prevalence estimation by animal category was 14.3% (95% CI, 11.4-17.2) for beef cows and 12.9% (95% CI, 10.0-15.8) for beef heifers. There was no significant difference in the estimated prevalence between the two animal types. There was no significant difference in the animal level prevalence of N. caninum infection among different herd sizes. None of the herd demographic or management variables was significantly associated with the seropositivity to N. caninum infection. In conclusion, these results show that N. caninum infection is common among beef herds across Uruguay. Since the beef industry is one of the key industries in Uruguay, the economic effect and risk factors of N. caninum infection among beef cattle in this country should be further evaluated in the near future.

Abortion, Veterinary↗
PubMed1998

Tuberculosis in adult beef cattle of Mexican origin shipped direct-to-slaughter into Texas.

OBJECTIVE: To evaluate differences in prevalence of tuberculosis (TB) in adult beef cattle that originated from different states in Mexico and were shipped direct-to-slaughter into Texas in 1995. DESIGN: Epidemiologic survey. ANIMALS: Approximately 65,000 adult beef cattle. PROCEDURES: Postmortem examinations of carcasses for detection of Mycobacterium bovis infection were conducted at slaughter plants in Texas. Specimens were collected from cattle with granulomatous lesions, stored in neutral-buffered 10% formalin or saturated sodium borate solution, and processed for histologic and bacteriologic diagnosis. Prevalence and 95% confidence intervals were estimated by state of origin. Difference between prevalences for different states was tested for significance (P < 0.05), using the proportion test. RESULTS: Overall prevalence of TB at slaughter in adult beef cattle that originated from Mexico was approximately 0.5/1,000 (34/65,233). Prevalence of TB in cattle that originated from Chihuahua (0.07) was significantly lower than that in cattle from Coahuila (0.80), Nuevo Leon (1.27), and Tamaulipas (1.81). CLINICAL IMPLICATIONS: Prevalence of M bovis infection in adult beef cattle may be significantly different between states in the northern border region of Mexico. On the basis of disease prevalence and numbers of exported cattle and provided safeguards such as TB testing are continued, cattle from Chihuahua may pose a lower risk of TB transmission to Texas cattle than do cattle from Coahuila, Nuevo Leon, and Tamaulipas. To allow interstate/international movement of cattle from northern border states of Mexico, TB testing requirements should be continued. In the context of international trade, southern border states of the United States should continue collaborating with northern border states of Mexico to control and eradicate this disease.

Abattoirs↗
PubMed2004

Quantification and prevalence of Salmonella in beef cattle presenting at slaughter.

AIMS: A survey to determine the prevalence and numbers of Salmonella in beef cattle presented for slaughter at abattoirs across Australia was conducted between September 2002 and January 2003. METHODS AND RESULTS: Automated immunomagnetic separation (AIMS) was used for detection and isolation of Salmonella enriched from cattle faeces. Salmonella were enumerated from positive samples using a combination of the Most Probable Number (MPN) technique and AIMS. A total of 310 faecal samples were tested, 155 were from lot-fed cattle and 155 from grass-fed cattle. Salmonella spp. were isolated from 21 (6.8%) of the cattle and the prevalence amongst grass-fed cattle (4.5%) was not significantly different to that found in lot-fed cattle (9%). Counts of Salmonella in positive faeces varied from <3 MPN g(-1) of faeces to 2.8 x 10(3) MPN g(-1) and 71% of positive samples had counts <10 MPN g(-1) faeces. There was no significant difference in the mean log10 number of Salmonella in faeces of cattle from each production system. CONCLUSION: Low numbers of beef cattle were found to shed Salmonella at the time of slaughter and the prevalence and the associated faecal concentrations did not vary significantly with the pre-slaughter production system (grass or lot feeding). The faecal concentration of Salmonella in the majority of faeces was low (<10 MPN g(-1)) with few high concentrations up to 3 x 10(3) MPN g(-1), suggesting there may be a low risk of carcase contamination. SIGNIFICANCE AND IMPACT OF THE STUDY: Beef cattle do not appear to be a major source of entry of Salmonella into the human food chain and the quantitative information contained in this study can be used in quantitative assessments of the associated risk of human salmonellosis.

Abattoirs↗
PubMed2006

Genome-wide linkage disequilibrium in two Japanese beef cattle breeds.

There is little knowledge about the degree of linkage disequilibrium (LD) in beef cattle. This study aims to perform a genome-wide search for LD in Japanese Black and Japanese Brown beef cattle and to compare the level of LD between these two breeds. Parameter D' (the LD coefficient) was used as a measure of LD, and LD was tested for significance of allelic associations between syntenic and between non-syntenic marker pairs. Effects of breed, chromosome, genetic map distance and their interactions with D' were tested based on least squares analyses. Both breeds showed high levels of LD, which ranged over several tens of cM and declined as the marker distance increased for syntenic marker pairs. A rapid decline of the D' value was observed between markers that were spaced 5 and 20 cM apart. LD was significant in most cases for marker pairs <40 cM apart but was not significant between non-syntenic loci. The pattern of LD found in these two breeds was similar to that previously published for dairy cattle. The D' value between breeds was not significantly different (P > 0.05), but the interaction between breed and chromosome was highly significant (P < 0.001). Genetic selection seems to have caused the heterogeneity of the D' values among chromosomes within breed. These results indicate that LD mapping is a useful tool for fine-mapping quantitative trait loci of economically important traits in Japanese beef cattle.

Alleles↗
PubMed2005

Enzyme immunoassay of progesterone in the feces from beef cattle to monitor the ovarian cycle.

The present study was undertaken to measure fecal progesterone concentration of beef cattle using antibody against authentic progesterone and to examine whether this method can monitor the ovarian cycle in beef cattle. Rectal fecal samples collected from 14 beef cattle were mixed with 6 ml of 100% methanol and shaken for 15 min. After centrifugation, supernatant was extracted with petroleum ether followed by an enzyme immunoassay (EIA) for progesterone. Specificity of the assay was examined by HPLC separation of fecal solution followed by the EIA in each fraction. The present assay identified only progesterone but not other metabolites in the feces sample that was extracted with petroleum ether. Sensitivity of the assay was estimated to be 0.0055 ng/ml (0.11 ng/g). Coefficient variations of intra- and inter-assay were 9.6-10.9% and 10.8-16.6%, respectively. Recovery rates ranged between 73 and 84%. Patterns in the fecal progesterone concentrations during the ovarian cycle were almost parallel to the plasma concentrations. A significant positive correlation was established between the fecal and plasma progesterone concentrations in individual animal (r=0.59-0.84, P<0.001, n=10) as well as pooled data (r=0.70, P<0.001, n=65). Fecal progesterone concentrations of day 0 (showing the nadir of concentration) of the ovarian cycle were less than 50 ng/g, which increased significantly toward day 9 (P<0.01). From days 14 to 18, there was significant reduction of fecal progesterone concentration (P<0.01). Ovarian cycles had at least 48 ng/g (mean=74 ng/g) of difference between minimum and maximum fecal progesterone concentrations. All cattle at days 9, 11 and 14 had higher fecal progesterone concentrations by more than 20 ng/g compared with day 0. These results suggest that the present EIA is suitable to measure the progesterone in cattle feces and can monitor ovarian cycle.

Animals↗
PubMed2006

Effect of low vitamin A status on fat deposition and fatty acid desaturation in beef cattle.

A group of Angus beef cattle was removed from temperate pastures and fed a very low beta-carotene cereal-based ration in a feedlot for over 300 d. Half the group was supplemented weekly with retinyl palmitate (at the rate of 60,000 IU vitamin A/100 live weight (LW)/day), sufficient to offset clinical vitamin A deficiency; the other half received no supplement. Blood was sampled from all animals at biweekly intervals to assess beta-carotene and vitamin A status. Adipose tissue was sampled by biopsy on three occasions throughout the experimental period and at slaughter to assess FA composition. Muscle was sampled at slaughter to determine the intramuscular fat content. The mean plasma concentration of beta-carotene of all animals fell from an initial value of 20.1 to 5.2 microg/mL at 14 d, to 1.4 microg/mL at 35 d, and to zero at 105 d. Mean vitamin A in plasma was not significantly different between the treatment groups initially. The values then rose to almost twice their initial values by 35 d, but subsequently fell to below initial values by day 119. Thereafter, plasma vitamin A of the supplemented group was significantly greater than that of the unsupplemented group (P < 0.05). Muscle samples at slaughter from supplemented animals contained significantly (P < 0.01) more intramuscular lipid (13.0 vs. 9.6%). Major changes occurred over time in FA composition in both groups. Saturated FA decreased as monounsaturated FA increased over the first 60 d. An index of desaturation of FA was significantly lower (P < 0.001) in the vitamin A-supplemented group than in the nonsupplemented group. M.P. of the adipose tissue of nonsupplemented animals was 32.3 degrees C, significantly less (P< 0.05) than that of supplemented animals (34.1 degrees C). Feeding vitamin A was associated with less intramuscular fat but with a less desirable (less unsaturated, more solid) FA profile.

Adipose Tissue↗
PubMed1988

Effect of prostaglandin F(2)alpha at insemination on sperm cell numbers and pregnancy rate in beef cattle.

Fourteen cycling, nonlactating, multiparous beef cows were artificially inseminated (AI) 10 to 12 h after the onset of natural estrus. One unit of frozen-thawed semen containing 100 x 10(6) total sperm cells was deposited into the body of the uterus. Immediately after AI, alternating cows were injected i.m. with either 25 mg (5 ml) of prostaglandin F(2)alpha (PGF) or 5 ml of 0.9% saline-benzyl alcohol control solution. Cows were slaughtered 16 +/- 1 h post AI, oviducts were retrieved, segmented into thirds (upper, middle and lower) and flushed with 1 ml of 0.2% gluteraldehyde in phosphate buffered saline. The number of sperm cells was counted using a phase contrast microscope. There were no right or left side effects (P=0.61) on the number of sperm cells recovered per oviduct within cow (389 vs 553; average SEM = 219). PGF had no effect (P=0.77) on the number of sperm cells recovered per oviduct (642 vs 300; average SEM = 231 for PGF and control females, respectively). More sperm cells were recovered from the lower third segment (P<0.05) compared with the middle and upper segments. Ovulation tended to affect (P=0.10) the number of sperm cells recovered per oviduct (742 vs 200; average SEM = 231). Additionally, 114 beef females (68 Angus x Hereford heifers and 46 Chianina crossbred postpartum suckled cows) were treated as described above following AI at natural estrus with 20 x 10(6) motile sperm cells. Pregnancy rates did not differ significantly in heifers (70.6 vs 58.8%) or in Chianina cows (34.8 vs 52.2%) for control and PGF-treated females, respectively. Overall, pregnancy rates were identical between control and PGF-treated females at 56.1%. In this study, PGF treatment immediately following AI in beef cattle had no effect on the number of sperm cells in the oviducts or on the pregnancy rate.

Journal Article↗
PubMed1998

Genetic parameters for sex-specific traits in beef cattle.

Data from 3,593 beef heifers and 4,079 of their steer paternal half-sibs were used to estimate genetic parameters of and among female growth and reproductive traits and male carcass traits. Estimates of heritability for adjusted 205-d weight, adjusted 365-d weight, age at puberty, calving rate, and calving difficulty measured on females were .16, .38, .47, .19, and .18, respectively; estimates for calving rate and calving difficulty were expressed on a normal scale. Estimates of heritability for hot carcass weight; retail product percentage; fat percentage; bone percentage; rib eye area; kidney, pelvic, and heart fat percentage; adjusted fat thickness; marbling score; Warner-Bratzler shear force; taste panel tenderness; taste panel juiciness; and taste panel flavor that were measured on steers at an average age of 447 d (weaning age = 185, days on feed = 262) were .50, .66, .58, .54, .61, .48, .66, .71, .26, .31, .00, and .04, respectively. Genetic correlations were positive for heifer weights with hot carcass weight, fat percentage, rib eye area, adjusted fat thickness, marbling score, and Warner-Bratzler shear force, and they were negative with retail product percentage and kidney, pelvic, and heart fat percentage of steers. Age at puberty was genetically correlated with taste panel tenderness but not with other carcass traits. Calving rate had positive genetic correlations with fat percentage, rib eye area, adjusted fat thickness, and taste panel flavor, and it had negative genetic correlations with retail product percentage; bone percentage; and kidney, pelvic, and heart fat percentage. Calving difficulty had favorable genetic correlations with hot carcass weight, retail product percentage, and measures of carcass tenderness, but it was unfavorably correlated with traits that involve carcass fatness. These results indicate that selection for some traits expressed in one sex of beef cattle may result in undesirable responses in traits expressed in the opposite sex.

Animals↗
PubMed1985

A serologic epidemiological study of parainfluenza 1, 2, and 3 viruses in beef cattle and calves in Illinois.

Beef cattle and calves in four Illinois populations were studied. Serum was tested by the hemagglutination-inhibition (HI) test for antibodies to parainfluenza viruses (PIV) 1, 2, and 3. In all but group 3 a low level of antibody to PIV-1 and 2 was demonstrated. The highest prevalence and incidence of HI-antibodies was found for PIV-3, followed by PIV-1. There may have been a cross-reaction between PIV-1 and -3 in Group 1 calves. The low level of HI antibodies to PIV-1 and 2 may have resulted from infections early in life or colostral antibodies that decreased with age.

Age Factors↗
PubMed1987

Isolation of leptospires from nephritic kidneys of beef cattle at slaughter.

Of 955 beef cattle slaughtered at an abattoir in Quebec from May to August 1985, 122 (13%) had lesions of focal interstitial nephritis. Nephritic kidneys were collected for leptospiral culture, and matching blood samples were examined serologically. Leptospires were isolated from the kidneys of 35 (29%) cattle. Antibodies to Leptospira interrogans serovar hardjo were found in 29 (24%) cattle and to pomona in 13 (10%).

Animals↗
PubMed2006

Temporal prevalence of antimicrobial resistance in Campylobacter spp. from beef cattle in Alberta feedlots.

Antimicrobial resistance (AMR) was temporally assessed in campylobacters isolated from beef cattle (7,738 fecal samples from 2,622 animals) in four commercial feedlots in Alberta. All calves were administered chlortetracycline and oxytetracycline in feed, and a majority of the animals (93%) were injected with long-acting oxytetracycline upon arrival at the feedlot. Fecal samples from individual animals were collected upon arrival (i.e., entry sample), 69 days (standard deviation [SD] = 3 days) after arrival (i.e., interim sample), and 189 days (SD = 33 days) after arrival (i.e., exit sample) at the feedlot. In total, 1,586 Campylobacter isolates consisting of Campylobacter coli (n = 154), Campylobacter fetus (n = 994), Campylobacter jejuni (n = 431), Campylobacter hyointestinalis (n = 4), and Campylobacter lanienae (n = 3) were recovered and characterized. The administration of antimicrobials did not decrease carriage rates of campylobacters, and minimal resistance (< or =4%) to azithromycin, ciprofloxacin, enrofloxacin, gentamicin, and meropenem was observed. In contrast, substantive increases in the prevalence of isolates resistant to tetracycline and doxycycline (56 to 89%) for C. coli, C. fetus, and C. jejuni, as well as in the number of animals (7 to 42%) from which resistant isolates were recovered, were observed during the feedlot period. Increased resistance to erythromycin (total isolates and carriages rates) was also observed in isolates of C. coli over the three isolation times. The majority of C. fetus isolates recovered were resistant to nalidixic acid, but this was independent of when they were isolated. A relatively limited number of multidrug-resistant isolates were recovered and consisted primarily of C. coli resistant to tetracyclines and erythromycin (10% of isolates). Over the course of the feedlot period, considerable increases in antimicrobial resistance were observed in C. coli, C. fetus, and C. jejuni, but with the exception of erythromycin resistance in C. coli, the administration of antimicrobial agents to beef cattle was found to have a minimal impact on resistance to macrolides and fluoroquinolones, the two classes of antimicrobials used to treat campylobacteriosis in humans. However, the widespread use of antimicrobial agents in beef production and the possible horizontal transfer of mobile genetic elements with antimicrobial resistance determinants among Campylobacter and other bacterial taxa emphasize the need to monitor AMR development in bacteria from beef cattle.

Alberta↗
PubMed1982

Genetic improvement of beef cattle in the United States: cattle, people and their interaction.

The purpose of this essay is to develop a historic perspective of the beef cattle population and the legion of people directing its genetic change so that future leadership can increase the rate of breeding technology assimilation. Use of cattle for beef to feed millions is relatively recent. The beef industry of the United States has a rich, romantic heritage that combined Spanish exploitation with British tradition. Spanish cattle became adapted as the Texas longhorn and the European cattle became indigenous. Breeds developed in Britain replaced both. The Zebu was introduced to produce cattle adapted to the Gulf Coast. Selection for early maturity in the British breeds promoted by livestock shows was ended by the dwarf gene. The Charolais breed demonstrated growth potential. Then in 1967, Continental European breeds were imported, given an array of biological types from which to select. Beef cattle breeding research expanded after the second world war through the three regional projects. Performance Registry International was the focal point for performance. The Beef Improvement Federation produced guidelines for recording beef performance including those for national sire evaluation. U.S. Meat Animal Research Center evaluated the several newly introduced breeds. To date, breeding researchers have developed breeding technology for the use by breeder. The major breed association are keeping and utilizing performance records. The genetic structure of the beef breeds is being altered by the use of AI such that genetic change can be made rapidly by the use of superior sires evaluated on their progeny in many herds.

Adaptation, Physiological↗
PubMed1995

Seedstock beef cattle: SPA.

The Standardized Performance Analysis (SPA) for seedstock beef cattle (SPA-SB) is a recommended set of production and financial performance analysis guidelines developed specifically for the seedstock cow-calf, replacement heifer, and the sale bull enterprises. These guidelines were developed by members of the National Cattlemen's Association (NCA) and the National Integrated Resource Management Coordinating Committee to provide beef cattle producers with a comprehensive, standardized means of measuring, analyzing, and reporting the performance and profitability of an operation. This article describes and illustrates through an example the performance measures chosen. NCA certifies software and education materials conforming to the Seedstock SPA Guidelines.

Accounting↗
PubMed2007

Genetic relationships among calving ease, calving interval, birth weight, and weaning weight in the Asturiana de los Valles beef cattle breed.

The aim of this paper was to estimate direct and maternal genetic parameters for calving ease (CE), birth weight (BrW), weaning weight (WW), and calving interval (CI) to assess the possibility of including this information in beef cattle improvement programs. Field data, including a total of 59,813 animals (1,390 sires and 1,147 maternal grand sires) from the Asturiana de los Valles beef cattle breed, were analyzed with a multivariate linear model. Estimates of heritability for direct genetic effects (CED, CID, BrWD, and WWD) were 0.191 +/- 0.019, 0.121 +/- 0.013, 0.390 +/- 0.030, and 0.453 +/- 0.035, respectively, whereas those for maternal genetic effects (CEM, BrWM, and WWM) were 0.140 +/- 0.015, 0.208 +/- 0.020, and 0.138 +/- 0.022, respectively. Genetic correlations between direct or maternal genetic effects across traits were, in general, positive and moderate to low. However, genetic correlation for the pair CED-BrWD was positive and high (0.604 +/- 0.064). Genetic correlations between the direct and maternal genetic effects within a trait were negative and moderate (-0.219 +/- 0.097 for CE, -0.337 +/- 0.080 for BrW, and -0.440 +/- 0.102 for WW). Genetic correlations for CED-BrWM and CED-WWM were -0.121 +/- 0.090 and -0.097 +/- 0.113, respectively. The genetic correlation for CEM-CID was unfavorable (0.485 +/- 0.078), and those for CEM-BrWD (-0.094 +/- 0.079) and CEM-WWD (-0.125 +/- 0.082) were low and negative. The genetic correlation between CID and WWM was favorable (-0.148 +/- 0.106). Overall, the data presented here support the hypothesis that maternal effects for CE and BrW are not the same and that the genetic relationships between CI and maternal effects for WW in beef cattle follow a similar pattern to that reported between CI and milk yield in dairy cattle. Moreover, the need to include direct and maternal breeding values in beef cattle selection programs is suggested.

Animals↗
PubMed2006

Reducing crude protein in beef cattle diet reduces ammonia emissions from artificial feedyard surfaces.

Concentrated animal feeding operations are major sources of ammonia to the atmosphere. Control methods to reduce emissions include acidifying amendments, urease inhibitors, and absorbents. For beef cattle, decreasing crude protein (CP) in diets may be the most practical and cost-effective method to reduce ammonia emissions. Our objective was to quantify the effect of reducing CP in beef cattle diet on ammonia emissions. Two groups of steers were fed diets with either 11.5 or 13.0% CP and all urine and feces were collected. Manures from the two diet treatments were applied in a replicated laboratory chamber experiment, and ammonia emission was quantified using acid gas washing. In four seasonal field trials, manures from the two diet treatments were applied to two 10-m-diameter, circular, artificial feedyard surfaces, and ammonia emission was quantified using the integrated horizontal flux method. Manure from steers fed 11.5% CP diet had less urine, less urinary N, and a lesser fraction of total N in urine, compared with the 13.0% CP diet. Decreasing crude protein in beef cattle diets from 13 to 11.5% significantly decreased ammonia emission by 44% (p < 0.01) in the closed chamber laboratory experiment, and decreased mean daily ammonia flux by 30% (p = 0.10), 52% (p = 0.08), and 29% (p < 0.01) in summer, autumn, and spring field trials, respectively. No difference was observed in winter. On an annual basis, decreasing crude protein reduced daily ammonia flux by 28%. Reducing crude protein in beef cattle diets may provide the most practical and cost-effective way to reduce ammonia emissions from feedyards.

Air Pollutants↗
PubMed1980

Effect of temperature and retention time on methane production from beef cattle waste.

The effect of temperature and retention time on the rate of methane production from waste of beef cattle fed a finishing diet was investigated by using continuously mixed 3-liter working volume anaerobic fermentors. The temperatures ranged from 30 to 65 degrees C with 5 degrees C increments between fermentors. The fermentors were fed once per day with 6% volatile solids (organic matter). Retention time for each temperature was varied from 18 to 2.5 days. After 3-volume turnovers, samples were obtained on 4 consecutive days. The highest methane production rate (liters/liter of fermentor per day) and methane yield at that rate (liters/gram of volatile solids) were 1.27 and 0.19 at 9 days and 30 degrees C, 1.60 and 0.16 at 6 days and 35 degrees C, 2.28 and 0.23 at 6 days and 40 degrees C, 2.42 and 0.24 at 6 days and 45 degrees C, 2.83 and 0.14 at 3 days and 50 degrees C, 2.75 and 0.14 at 3 days and 55 degrees C, 3.18 and 0.14 at 2.5 days and 60 degrees C, and 1.69 and 0.17 at 6 days and 65 degrees C. Volatile solids degradation at these retention times and temperatures was between 46 and 54%. The concentrations of volatile acids in the 30 to 55 degrees C fermentors were generally below 2,000 mg/liter, with the exception of the 3-day retention time. The 60 and 65 degrees C fermentors were usually above this level for all retention times. These studies indicate potential rates of methane production from the fermentation of untreated waste of beef cattle fed high-grain finishing diets. This information should serve as preliminary guidelines for various kinetic analyses and aid in economic evaluations of the potential feasibility of fermenting beef cattle waste to methane.

Journal Article↗
PubMed2004

Genetic diversity of Escherichia coli recovered from the oral cavity of beef cattle and their relatedness to faecal E. coli.

AIMS: To determine the genetic diversity of generic Escherichia coli recovered from the oral cavities of beef cattle and their relatedness to E. coli isolated from the faeces of cattle during pasture grazing and feedlot finishing. METHODS AND RESULTS: A total of 484 E. coli (248 oral and 236 faecal isolates) were obtained from eight beef cattle after 1 and 5 months of grazing on pasture and after 1 and 5 months in a feedlot. The random amplification of polymorphic DNA (RAPD) method was used to genetically characterize these isolates. The RAPD patterns showed that ca 60% of E. coli recovered from the oral cavities and faeces during pasture and feedlot shared a close genetic relatedness. A number of E. coli with unique RAPD types were also found either in the oral cavities or faeces. Most of the E. coli RAPD types recovered from the oral cavities were shared among animals, but there were also RAPD types which were unique to individual animals. The E. coli populations of the oral cavities were genetically diverse and changed over time. CONCLUSIONS: This study indicates that there are large numbers of E. coli carried in the oral cavities of beef cattle and those E. coli are closely related to strains found in the faeces. The oral cavities of cattle harbour a genetically diverse E. coli population. SIGNIFICANCE AND IMPACT OF THE STUDY: The oral cavity may be an important reservoir of enteric pathogens which may transfer to meat during carcass dressing. A better understanding of the molecular ecology of E. coli in cattle would assist the design of approaches to control pathogenic strains during beef production and processing.

Animals↗
PubMed2000

[Prediction and evaluation of heterosis of beef cattle and their application].

The genetic structure and genetic variation of eight beef cattle cross parents populations were analyzed by six microsatellite loci, and heterosis of beef cattle was predicted. On the basis of microsatellite analysis, the effect of 18 cross combinations was estimated by the method of individual animal model BLUP. A new method of molecular quantitative genetics that select best of all cross combination was submitted. The results showed that the combinations with Hereford Limousine and Charolais as paternal parent are better than others in Fengning and Longhua regions; the combinations with Limousine Angus and Hereford as paternal parent are better than others in Zanhuang regions; the combinations with Hereford Limousine and Piemontese as paternal parent are better than others in Funing regions. Effect of three breeds cross is better than two breeds.

Animals↗