Factors influencing calving difficulty in beef heifers

Records of 547, 2-yr-old heifers of three breed groups were used to evaluate the relative influence of dam's body and pelvic measurements, calf birth weight, sire birth weight and some relative measures (ratios) of calf birth weight and dam weight at calving on calving difficulty. The data were analyzed by regression and least squares procedures. The full model explained 32.5% of the variation in calving difficulty score. The linear effect of calf birth weight was the most important variable, accounting for 17.8% reduction in the coefficient of determination, and together with dam weight at calving and the quadratic effect of calf birth weight it accounted for 92% for all the variation explained by the full model. Dam weight at calving was negatively related to calving difficulty. Breed, year and sex of calf did not influence calving difficulty score, except when the calf birth weight or dam weight or both were excluded from the model. When calf birth weight was expressed as a ratio of the dam's weight at calving, hip height and pelvic measurements, the total model explained 34.8% of the variation in calving difficulty score. The ratio of calf birth weight to dam weight was the most important variable (R2 = 26.8%). Ratios of calf to dam weight at calving and calf weight to the vertical pelvic diameter (R2 = 29.3%) were the only significant factors when the effects of calf birth weight and dam weight were removed from the model. Pelvic measurements, on their own, did not influence calving difficulty score in this study (P greater than .1), but small pelvic dimensions tended to be associated with higher calving difficulty scores.     

Postmortem proteolysis in longissimus muscle from beef, lamb and pork carcasses

Postmortem proteolysis in skeletal muscle and factors affecting this process were examined in pork, lamb and beef longissimus muscles (LM) to determine the cause of differences in meat tenderness among these species. Fat thickness differed among species in the following order: pork greater than beef greater than lamb. The following patterns were observed for rate of temperature and pH decline: lamb greater than pork greater than beef and pork greater than beef greater than lamb, respectively. At 1 d postmortem, pork was the most tender, followed by beef and lamb, respectively. Between 1 and 14 d of postmortem storage, lamb LM was the most improved in tenderness, followed by beef and pork, respectively. Species did not differ (P greater than .05) in LM collagen solubility. Pork LM from fed pigs had the highest (P less than .05) level of cathepsins B + L and cystatin(s) activities, whereas no differences (P greater than .05) were observed among the species for cathepsin B activity. The lowest (P less than .01) Ca2(+)-dependent protease (CDP)-II and CDP inhibitor activities were observed in pork LM. Beef LM had the highest CDP inhibitor activity (P less than .05) but was intermediate in CDP-II activity. No differences were observed among species for CDP-I activity. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrils isolated at 0, 1 and 14 d postmortem indicated that by d 1, desmin hydrolysis was most extensive in pork muscle, followed by lamb and beef.(ABSTRACT TRUNCATED AT 250 WORDS)     

A HACCP-based approach to hygienic slaughter and dressing of lamb carcasses

AIMS: This paper compares changes in visible and microbiological contamination on lamb carcasses dressed using one system which includes process factors previously identified as potential critical control points for HACCP-based approaches to hygienic slaughter and dressing, and another system which excludes those factors. METHODS: Longitudinal changes in microbiological and visible contamination of lamb carcasses were quantified in two slaughterhouses, one utilising clean, shorn, unwashed lambs in an inverted dressing system, the other utilising dirty, woolly, washed lambs in a traditional dressing system. Excision samples (5 cm2 each) for microbiological analyses were taken from two sites on 25 carcasses per treatment group immediately after pelting, at the completion of dressing, after overnight chilling and after boning and packaging. Visible contamination on the surface of 300 carcasses per treatment group was assessed after pelting and after overnight chilling. RESULTS: Mean aerobic plate counts and Escherichia coli counts on the leg and loin in the inverted dressing system were low after pelting (log10/cm2 1.86 and 1.71; log10/cm2 0.13 and 0.05 respectively) but generally showed statistically significant increases through to final packaging. In the conventional dressing system, there were much higher counts on the leg and loin after pelting (log10/cm2 4.66 and 2.71; log10/cm2 2.21 and 0.24 respectively), but subsequent handling of the carcass by slaughter line workers had no measurable deleterious effects. The inverted dressing system resulted in final mean aerobic plate counts on meat at packaging that were 1.38% (leg) and 48.98% (loin) of those derived from the conventional dressing system. Mean E. coli counts from the inverted system were 21.37% (leg) and 67.61% (loin) of those from the conventional system. There was an inverse relationship between the prevalence of carcasses with visible faecal contamination and their microbiological status. CONCLUSION: Significant reductions in microbiological contamination of sheep carcasses can be brought about by HACCP-based systems. Possible critical control points are pre-slaughter presentation status (including avoidance of pre-slaughter washing), inverted dressing, handling by slaughter line workers and meat inspectors, and chilling. Use of levels of visual faecal contamination as an on-line monitoring parameter for slaughter hygiene can give erroneous results. Interactions between different process steps may alter the effectiveness of the HACCP plan, and successful design and application depends on a detailed knowledge of the specific process utilised in each slaughterhouse.     

Evaluation of the Hennessy grading probe to predict yields of lamb carcasses fabricated to multiple end points.

Lamb carcasses (n = 278) were selected immediately after slaughter and fat thickness was measured with the SP2 Hennessy grading probe (HP) at the interface of the 12th and 13th ribs, 3.8 cm from the backbone. After a 24-h chilling period, carcasses were graded by a USDA grader and probed with the HP to obtain a fat thickness measure on the chilled carcass. One hundred sixty-five carcasses were fabricated into wholesale cuts (.64 cm of external fat trim), and 113 carcasses were fabricated into tray-ready retail cuts (.25 cm of external fat trim). Carcass weight, fat thickness (metal probe), adjusted fat thickness, hot and chilled carcass HP fat measures, as well as kidney and pelvic fat percentage and USDA yield grade, were highly correlated to cutting yield for both fabrication methods. Regression models developed to predict wholesale cut yields using HP or grader-collected measures were similar with respect to predictive accuracy. Fat thickness explained most of the variation in wholesale and tray-ready cut yields among the variables collected by the grader. Kidney and pelvic fat accounted for more of the variation in yield of wholesale cuts during stepwise regression to determine HP equations, but for predicting tray-ready yields, fat thickness taken with the HP accounted for the largest amount of variation. Equations developed to predict tray-ready retail cut yields using the HP or USDA grader-collected carcass measures were similar in the amount of variation explained. Kidney and pelvic fat percentage must be included in equations to maximize predictive accuracy when this depot site is left in carcasses.     

Ultrasonic, needle, and carcass measurements for predicting chemical composition of lamb carcasses

Three groups (n = 147) of New Zealand mixed breed lambs averaging 170 d of age and 31.7 kg in weight were killed after a diet of pasture to determine whether the total depth of soft tissues over the 12th rib 11 cm from the dorsal midline (GR) could be measured in live lambs with sufficient accuracy to warrant its use as a selection tool for breeding flock replacements. Relationships among live and carcass measurements and carcass chemical composition also were determined. An ultrasonic measurement of GR in the live lambs was a more accurate predictor of carcass GR (r = .87) and percentage carcass fat (r = .80) than was a measurement of GR made with a needle (r = .80 and .67, respectively). Both measurements were sufficiently accurate to permit culling of over-fat lambs from breeding flock replacement prospects. The best single indicator of percentage carcass fat (r = .87) was a shoulder fat measurement, followed closely by carcass GR (r = .85). Both were superior to USDA yield grade for estimating carcass chemical composition in these young, lightweight lambs. These two measurements also were most highly related to percentage carcass protein (r = -.78 and r = -.77, respectively). These results indicate possibilities for improving the method of evaluating the composition of U. S. lamb carcasses.     

Yield grade and carcass weight effects on the cutability of lamb carcasses fabricated into innovative style subprimals.

Lamb carcass (n = 100) were selected from USDA yield grades (YG) 2, 3, and 4 and carcass weight (CW) groups 20.4 to 24.9, 25.0 to 29.5, and 29.6 to 34.0 kg. Lamb carcass were fabricated into semiboneless and boneless subprimals and trimmed to three s.c. fat trim levels: .64, .25, and .00 cm of fat remaining. Innovative subprimals were fabricated and yields were calculated for the subprimals and dissectible components (lean, bone, connective tissue, external fat, and seam fat) from each of the various subprimals. Carcass weight as a main effect in a two-way analysis of variance did not account for a significant amount of the variation in yield among trimmed subprimals or the percentage of the dissectible components, but USDA YG was a significant main effect in determining variation in yield for many of the subprimals or dissectible components. Muscle seaming of shoulders and legs and removal of excessive tails on the loin and rack resulted in a majority of the seam fat being removed from these cuts. Dissection data clearly showed that seam fat is a major component of rack and shoulder cuts and with increasing fatness or higher numerical yield grade there are clearly increased amounts of this depot. Increased trimming of external fat magnifies and draws more attention to the amount of seam fat remaining. Production of heavy, lean lambs would be more useful in an innovative type of program because of the larger-sized muscles. Heavy, fat lambs would not be as useful because of their decreased yields and excess seam fat located in cuts that cannot be muscled-seamed because of the loss of retail cut integrity. Seam fat was highly correlated to percentage of kidney and pelvic fat and to external fat thickness and with USDA yield grade but was not strongly correlated to carcass weight.     

The effect of different on-line dressing practices on microbiological and visible contamination of lamb carcasses

Three dressing practices were assessed in traditional lamb carcass dressing systems for their ability to improve control of microbiological and visible contamination. The routine removal of a piece of skin from the perineal area reduced total aerobic plate counts and Escherichia coli counts on carcasses derived from both woolly and shorn groups of lambs. Similar results were found when the "Y-cut" was delayed in the dressing sequence, but E. coli counts increased slightly in one group. The use of a wide-blow shear prior to the opening cut on the hindleg of carcasses derived from woolly lambs resulted in a slight increase in the microbiological contamination on the leg. The removal of a piece of skin from the perineal area reduced scores for faecal contamination despite a small increase in contamination with wool. Changes in visible contamination in response to the two other dressing procedures were principally effected through changes in levels of contamination with wool. Irrespective of dressing procedures, levels of microbiological and visible contamination were lower on carcasses derived from shorn compared with woolly lambs. These studies demonstrated that, although they are reasonable indicators, the use of parameters of visible contamination as a measure of carcass hygiene must be treated with caution. This is especially the case if a genuine HACCP-based system for the control of dressing hygiene for a particular class of slaughtered livestock is to be implemented.     

分析影响毛皮业发展的几点因素

目前,我国已经成为世界公认的毛皮生产大国.养殖业真正发腱起来是在近10年,由于各种经济成分,特别是民营企业走进市场,使养殖业的发展速度加快,奠定了毛皮行业整体发展的基础.     

Factors influencing the isolation of Mycobacterium avium subsp. paratuberculosis from bovine fecal samples.

A modified procedure was used for culture of Mycobacterium paratuberculosis (Mptb) from bovine feces. Bovine fecal samples were decontaminated with NaOH, exposed to a mixture of oxalic acid and malachite green, incubated in a mixture of neomycin and amphotericin B. Decontaminated specimens were inoculated onto modified L?wenstein-Jensen medium. Specimens processed by high-speed centrifugation showed growth earlier than specimens prepared by low-speed centrifugation. However, the overall number of positive cultures at 16 weeks was not different for the 2 methods. When infected dairy herds were sampled 4 times at 6-month intervals and culture-positive cows were culled, the prevalence of infected cattle declined over time. After selective culling, the cattle left in the herds shed low numbers of Mptb, which explains why it took longer for cultures to become positive. No heifers younger than 11 months were culture positive, but heifers 13-14 months of age were more frequently culture positive than were heifers of any other age. The 16-week culture period is needed with this method to detect cattle shedding low numbers of Mptb. High-speed centrifugation of samples does not increase the efficiency of identification of animals shedding Mptb.     

Factors influencing the international spread of equine diseases.

In an era of increasing globalization, the risk of spread of infectious diseases in humans and animals, including equids, has never been greater. International movement of equids and trade in semen are the most important factors responsible for the dissemination of various equine pathogens. Other factors that can or do have the potential to influence the global distribution of equine infectious diseases include: multinational trade agreements, emergent diseases, mutation of pathogens, climate related phenomena, migration of amplifying/reservoir hosts or vectors, availability of new vectors, vaccine contamination and agroterrorism. The relative importance of each of these factors is considered in relation to the spread of equine diseases.     

Evaluation of antimicrobial resistance of Campylobacter spp. isolated from broiler carcasses

1. The aim of the present study was to evaluate the antimicrobial resistance of Campylobacter strains (C. jejuni, C. coli and C. lari) isolated from broiler carcasses processed in the State of Paraná, Brazil.

2. Rates of microbial resistance and susceptibility were assessed by both Disk Diffusion (DD) and Etest (Minimum Inhibitory Concentration) techniques. Antibiotics were tested using DD (12 antibiotics) and/or MIC (7 antibiotics) methods.

3. A total of 95.8% of the strains were resistant to at least two agents. In terms of multidrug resistance, 75% of strains were resistant to three or more groups of antibiotics. The highest rates of resistance were detected for cefalotin, ciprofloxacin, tetracycline and nalidixic acid. A high rate of susceptibility of the strains to erythromycin (95.8%) was found confirming that this is considered the agent of choice for treating campylobacteriosis. Comparison of the microbial resistance and susceptibility, as determined simultaneously by the two methods, found the techniques to be statistically equivalent for 5 out of the 6 antibiotics tested.

4. The results of this study suggest the need for adopting measures to control the use of antibiotics in broiler production to prevent multidrug resistance of Campylobacter strains and reduce the risk of serious human diseases caused by the consumption of contaminated chicken meat.     

Factors influencing recovery from and duration of lameness in Michigan (USA) horses.

The objective of this study was to identify factors that may affect recovery from and duration of a case of lameness in a stratified random sample of Michigan horses. This was done using data from Phase-II of the Michigan equine monitoring system (MEMS Phase-II), the equine health-monitoring study [Kaneene et al., Prev. Vet. Med. 29 (1997b) 277-292; Ross and Kaneene, Prev. Vet. Med. 28 (1996a) 209-224; Ross and Kaneene, Prev. Vet. Med. 29 (1996b) 59-75; Ross et al., Am. J. Vet. Res. 59 (1997) 23-29]. In this study, statistical modelling was conducted to evaluate risk factors affecting recovery from and duration of lameness using multivariable logistic regression and Cox's proportional hazards regression, respectively. Of 357 incident lameness cases reported during MEMS Phase-II, 280 (78.6%) were reported to have recovered. The median duration of a lameness case was 18 days (1st quartile (Q): 1, maximum (Max): 360). A total of 296 of 357 (82.9%) incident lameness cases received some type of treatment. Of 619 total treatments used, 329 (53.2%) were administered, conducted or applied by a veterinarian. Horses experiencing other types of lameness were less likely to recover than those experiencing hoof lameness (odds ratio (OR) = 0.48; 95% CI: 0.25, 0.93). Horses that had participated in exercise-related activities during the study period and prior to the lameness were more likely to recover (OR = 1.91; 95% CI: 1.05, 3.50). Treatment of the lameness was associated with an increased likelihood of recovery (OR = 1.82; 95% CI: 0.97, 3.45). Cases with a veterinarian involved in the diagnosis were associated with a decreased risk of recovery (OR = 0.48; 95% CI: 0.27, 0.84) and a longer duration lameness (HR = 0.58; 95% CI: 0.45, 0.73)--which might indicate that these cases were more complex or severe. Although cases treated for lameness were more likely to recover (OR = 1.82; 95% CI: 1.05, 3.50), treatment was not associated with lameness duration (HR = 0.58; 95% CI: 0.45, 0.73).     

影响牛胚胎移植妊娠率因素的分析

关于影响牛鲜胚或冻胚移植妊娠率的因素在国内外已有很多的报道,但都是以单项因素研究居多.本试验对影响牛体内胚胎(以冷冻胚胎为主)移植妊娠率的多项因素如胚胎冷冻、解冻、胚龄、黄体质量、受体牛的生理状态等进行分析,以选择最佳的技术方案,为牛胚胎移植产业化服务.     

影响牧草生物量形成的因素

牧草生物量包括草地地上部分生物量和地下部分生物量。影响牧草生物量的因素较多，概括而言，可分为气候因素(光照、水分等)、土壤因素(土壤结构、土壤质地、土壤肥力等)、生物因素(牧草品种、草地杂草、病虫鼠害、化感作用)和管理因素(放牧、灌溉、杂草防除、施肥等)。     

影响青贮饲料质量的因素

青贮饲料是奶牛饲养中不可缺少的常规饲料，提高青贮质量是饲养高产奶牛的关键，也是降低成本的重要方面，影响青贮质量的因素很多，主要分为影响青贮原料的因素和影响青贮发酵条件的因素，本文对此作一简述。一、影响青贮原料的因素１．牧草作物与品种：作物或牧草在植物分类上科、属、种不同，其营养成分（干物质、蛋白质、脂肪、纤维、矿物质、无氮浸出物、能量等）含量也不同。在同一种中不同的栽培品种（四倍体与二倍体；早熟品种与晚熟品种）其营养成分含量亦不同，因此要选择适合本地区的优质饲料品种来制作青贮。２．生长期：品种确…