Relationships between liver element concentrations and age in perinatal lambs dying of natural causes in Michigan, USA

A study was designed to characterize potential relationships between liver concentration of nine specific elements and age in preweaned Michigan lambs. All lambs that died before weaning in 1986 from 33 Michigan sheep producers were submitted to the Michigan State University Animal Health Diagnostic Laboratory for necropsy. Inductively coupled argon plasma emission spectroscopy was used to measure liver concentrations of Ca, Cu, Fe, K, Mg, Na, Na, P, and Zn in 888 lambs. Linear and non-linear regression techniques were employed to evaluate the relationship between liver element concentration and age. The potentially confounding variables farm of origin and cause of death were significant (P<0.01) in all models. No linear relationship was found between any liver element concentration and lamb age. Significant (P<0.05) non-linear relationships were found between liver concentrations of Cu, Fe, K, Na, Mg, and Zn and lamb age. Because of the large sample size of lambs selected from non-experimental populations, these results should provide diagnosticians with a useful guide for the interpretation of similar data when investigating perinatal lamb mortality.     

Relationships between liver element concentration and cause of death in perinatal lambs in Michigan, USA

Relationships were characterized between liver concentration of Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn and cause of death in pre-weaned Michigan lambs. In 1986, the 888 lambs that died before weaning from 33 Michigan sheep producers were submitted to the Michigan State University Animal Health Diagnostic Laboratory for necropsy. Inductively coupled argon plasma emission spectroscopy was used to measure liver element concentrations. The five major causes of death discovered by gross necropsy were dystocia-stillborn, starvation-hypothermia, pneumonia, abortion and trauma. Each of the five causes of death had significant (P<0.05) associations with various liver element concentrations when evaluated with logistic regression. These results suggest that liver element concentrations in perinatal lambs dying of common production diseases can be expected to vary with the cause of death.     

Use of posterior predictive assessments to evaluate model fit in multilevel logistic regression

Assessing the fit of a model is an important final step in any statistical analysis, but this is not straightforward when complex discrete response models are used. Cross validation and posterior predictions have been suggested as methods to aid model criticism. In this paper a comparison is made between four methods of model predictive assessment in the context of a three level logistic regression model for clinical mastitis in dairy cattle; cross validation, a prediction using the full posterior predictive distribution and two “mixed” predictive methods that incorporate higher level random effects simulated from the underlying model distribution. Cross validation is considered a gold standard method but is computationally intensive and thus a comparison is made between posterior predictive assessments and cross validation. The analyses revealed that mixed prediction methods produced results close to cross validation whilst the full posterior predictive assessment gave predictions that were over-optimistic (closer to the observed disease rates) compared with cross validation. A mixed prediction method that simulated random effects from both higher levels was best at identifying the outlying level two (farm-year) units of interest. It is concluded that this mixed prediction method, simulating random effects from both higher levels, is straightforward and may be of value in model criticism of multilevel logistic regression, a technique commonly used for animal health data with a hierarchical structure.     

Use of a GnRH antagonist,antarelix, associated or not with hCG,to control ovulation in cyclic pony mares

The GnRH antagonist antarelix (Teverelix™) was administered to mares (0.01 mg/kg, i.v., twice a day) during the periovulatory period. In Experiment 1, 20 mares were divided into a treated (A3d−) and a control (Control−) group. A3d− mares received antarelix for 3 days from the day when the dominant follicle (F1) reached 32 mm (D0). In Experiment 2, 10 mares were divided into a treated (A6d+) and a control (Control+) group. A6d+ mares received antarelix for 6 days from D0 and hCG was injected in all animals (1600 IU, i.v.) on D1. Pregnancies were determined 13 days after ovulation. In both experiments, antarelix interrupted or totally abolished the LH surge. In Experiment 1, 5/10 of the A3d− mares (with maximum LH concentrations of 11.6 ng/ml at the beginning of treatment) ovulated at the same time as the Control− mares; the other five mares (with LH concentrations under 5.4 ng/ml) ovulated 13.4±0.6 days later. In Experiment 2, all the A6d+ mares ovulated at the same time as the Control+ mares. In treated mares which ovulated during the treatment, progesterone concentrations and fertility did not differ from control mares. These results demonstrate that in mares: (1) a small elevation of endogenous LH can induce ovulation, (2) ovulation can be postponed approximately 13 days after a 3-day antarelix treatment if initiated just before the preovulatory LH surge, (3) ovulation can be induced by hCG on depressed levels of endogenous LH, (4) the inhibition of the post ovulatory LH surge has no effect either on the corpus luteum or on fertility.     

Active use of coyotes (Canis latrans) to detect Bovine Tuberculosis in northeastern Michigan, USA

Seroconversion after early vaccination at four weeks against canine parvovirus (CPV) using a high antigen titre vaccine was evaluated in 121 puppies from three breeds of dogs housed in kennels representative of the private practitioner's environment. The trial included 52 German shepherd pups, 25 Rottweiler pups and 44 Boerboel pups. From each group 11, 4, and 18 puppies acted as control dogs, respectively. Depending on the different groups, puppies were vaccinated at 4, 6, 9 and 12 weeks. The experimental group differed from the control group in that they received the high titre vaccine at 4 weeks of age, whereas the control group was not vaccinated at 4 weeks. Blood was collected from all pups prior to vaccination to measure maternally derived colostral antibody. The results indicated that vaccination at 4 weeks of age in pups with high maternally derived antibody levels, results in seroconversion rates that may lead to a reduction in the window of susceptibility with respect to CPV infection. The implications of the findings with respect to dogs in heavily contaminated environments are discussed.     

Epidemiology of Mycobacterium bovis in free-ranging white-tailed deer,Michigan, USA, 1995-2000

An endemic area of bovine tuberculosis (TB) (Mycobacterium bovis) currently affecting wild white-tailed deer (Odocoileus virginianus) in northern lower Michigan, USA, constitutes the first self-sustaining outbreak of the infection in free-ranging North American cervids. Given this precedent, epidemiologic insights gained from the outbreak afford the opportunity to guide not only current surveillance and intervention but also control efforts for future outbreaks involving wildlife reservoirs. Our specific objectives were to evaluate retrospective data from field surveillance conducted from 1995 to 2000 to determine apparent prevalence, trends in apparent prevalence, and the effects of various factors on the odds of being M. bovis positive.Data were gathered from post-mortem examinations of 62,560 wild deer collected from all 83 Michigan counties. Records of survey method, sex, age, geographic area and infection status as determined by mycobacterial culture were subjected to trend analysis and multivariable logistic regression. Apparent prevalence for the period was 0.54% (336/62,560) statewide. Prevalence varied widely with geographic area, but significantly decreased since 1995 in the core area of the outbreak-which coincided with implementation of control strategies. Significant risk factors were geographic area, sex, age, and the sex-by-age interaction. The survey method by which deer were obtained for testing was not a predictor of infection.Our results to date suggest an outbreak characterized by broad areas of very low prevalence surrounding focal areas where prevalence is sometimes orders-of-magnitude higher (e.g., deer originating from the core area were up to 147 times more likely to be TB positive than deer from other areas). Our results also identify older male deer as most likely to be M. bovis positive (OR=11.3, 95% CI 3.2, 40.3 for bucks > or =5 years vs. does < or =1.5 years)-an observation consistent with the biology and behavior of the species. Synthesizing these results with those of other ongoing investigations, we hypothesize a two-stage model of disease transmission where TB is maintained at very low prevalence in matriarchal groups, with primary dissemination of the disease attributable to the dispersal and movements of bucks (as well as to the large aggregations of animals created by human activities).     

Use of lufenuron as a treatment for fungal endometritis in four mares

Lufenuron, a benzoylphenyl urea derivative, was evaluated as a treatment for endometrial fungal infections in 4 mares. Intrauterine lavage was performed with lufenuron suspended in sterile saline (0.9% NaCl) solution. Cytologic evaluation and fungal culture of the endometrium, as well as subsequent reproductive performance, were used to monitor efficacy of this treatment. Fungal endometritis in mares is associated with infertility. Treatment is often ineffective and costly, and recurrence following treatment is not uncommon. Intrauterine infusions of lufenuron were effective in eliminating fungal endometritis in the 4 mares of this report.     

Use of an intra-uterine glass ball protocol to extend luteal function in mares

A 25- or 35-mm diameter glass ball was placed in the uterus of mares to observe the effect on interovulatory interval, luteal function, estrous behavior, the endometrium, and subsequent fertility. The 25-mm glass ball was spontaneously expelled from the uterus of 6 of 12 mares (50%), whereas none of the 35-mm glass balls was expelled. Teasing results were consistent with the concentration of circulating progesterone. Luteal function was extended in 7 of 18 mares (39%) maintaining a glass ball, whereas an extended luteal period occurred in 4 of 32 mares (13%) observed as controls. Extended luteal function occurred in 7 of 62 diestrus periods (11%) among mares following ball placement, whereas 4 of 50 diestrus periods (8%) were extended in control cycles. The mean luteal life span in mares with a glass ball and extended luteal function was 87 days (range, 76 to 109 days); there were no significant differences in length of luteal function in both groups of mares that received the 2 different ball sizes. Endometrial changes observed between preplacement and postremoval samples were minimal. When mares were bred in the season subsequent to glass ball removal, 17 of 23 (74%) conceived. Placing an intrauterine glass ball in a mare may be an alternative to exogenous hormone therapy to prevent cycling in some mares. Luteal function was extended to nearly 90 days in approximately 40% of mares. The 35-mm diameter glass ball appeared to have an advantage for retention over the 25-mm size. Results of our study could not completely rule out idiopathic persistence of the corpus luteum as an explanation for the extended luteal function observed in mares with a glass ball. Readers are cautioned that many questions still exist about the use of intra-uterine glass balls in mares. Further work is required to confirm the efficacy of the use of an intra-uterine glass ball for prolonged luteal function in mares and to identify its mechanism of action.

Introduction

In recent years, there has been a debate among veterinary practitioners concerning the efficacy of various extra-label uses of progestin products (eg, cattle growth implants and human depo-progestin injectables) to modify behavior in mares. Clients who own horses are more frequently seeking means to suppress behavioral signs of estrus, expecting that with such suppression the mare will train or perform better. Requests for these progestin products by mare owners puts veterinary practitioners in the precarious situation of using pharmaceuticals, extra-label, without scientific evidence of efficacy, in mares.In reality, the only truly effective means of suppressing behavioral signs of estrus in most intact mares is to maintain sufficient concentrations of circulating progesterone or its equivalent. Today the only efficacious way to maintain a sufficient level of progesterone or its equivalent is for the mare to have a functional corpus luteum (CL), administer exogenous progesterone (eg, ≥50 mg in oil, intramuscularly, daily), or administer daily synthetic progestins (eg, altrenogest [Regumate], Hoechst Roussel Vet, Warren, NJ).^{1, 2 and 3}Recently, placement of a glass ball of 30-mm diameter in the uterus has been suggested as a reversible means of preventing mares from cycling and displaying behavioral signs of estrus (message to Equine Clinicians Network, Dr Randy J. T. de Greef, March 19, 2000). If this technique is effective, it would be of value to mare owners because it would eliminate the need for daily treatments over extended periods.We have been unable to find literature that would support or refute this idea in horses. However, the effects on ovarian function, body weight gain, and pregnancy rate in nulliparous heifers of a copper-bearing intrauterine device were studied.⁴ The researchers reported that the heifers receiving the intrauterine device had lower progesterone concentrations than did control subjects. Nevertheless, nearly all of the treated heifers had better weight gain, were anestrus, and did not become pregnant during the study; however, multiple ovarian follicular cysts developed in many of them. The idea of using an intrauterine device to suppress estrus is said to have originated centuries ago in the Middle East as a common means of keeping camels from cycling and becoming pregnant (personal communication, Dr Ahmed Tibary, College of Veterinary Medicine, Washington State University, Pullman, Wash, May 2000).To our knowledge, the efficacy and long-term effects of glass ball treatment have not been critically evaluated. Our objectives in this study were to observe the effect of placement of an intra-uterine glass ball on interovulatory interval, luteal function, estrous behavior, the endometrium, and subsequent fertility of mares.

Materials and methods

Animals

A total of 38 light-horse breed mares ranging in age from 3 to 20 years were used for this study. Mares were maintained in accordance with the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (1st revised edition, January 1999). All experimental procedures involving animals were approved by the Institutional Animal Care and Use Committee at Auburn University (IACUC Protocol No. 0308-R-2307).

Intra-uterine device

Two glass ball (www.glassmarbles.com) sizes, 25- and 35-mm diameters, were evaluated in this study (Fig 1).

Use of stapling instruments to aid in the removal of ovarian tumours in mares

Ovarian granulosa theca cell tumours were removed surgically in 10 mares. Stapling instruments were used to facilitate haemostasis of the ovarian pedicle in five out of 10 cases and as a sole method of haemostasis in the remaining five cases. Postoperative haemorrhage from the ovarian pedicle was suspected in only one case. All cases survived long term follow-up from six months to four years. Results from this series of cases indicate that stapling instruments provide a rapid, easy and efficient means of ligating ovarian pedicles when performing ovariectomy in the mare.     

The effect of subclinical Mycobacterium paratuberculosis infection on days open in Michigan, USA, dairy cows

A prospective cohort study design was used to evaluate the impact of subclinical Mycobacterium paratuberculosis infection on days open in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. Participating herds were tested and productivity and reproduction records were monitored for 18 months. All cows > or = 24 months old were tested for M. paratuberculosis infection using the ELISA and radiometric fecal-culture (RFC) techniques. Test-negative cows were re-tested at the conclusion of the monitoring period. Multivariable regression models were used. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8% (223/533 animals tested). Adjusting for diagnostic sensitivity and specificity, this resulted in a calculated sample true prevalence of 59.9%. ELISA-positive cows (on average) had a 28-day increase in days open when compared to ELISA-negative cows (p=0.02). The diagnostic method used to define a case altered the apparent association between paratuberculosis test status and days open. Fecal culture was a less-effective diagnostic tool for use in herds with a high prevalence of infected animals. The increase in days open in the ELISA-positive cows was an indication that perhaps reduced estrus expression or an increased post-partum anestrous period occurred in the subclinically infected ELISA-positive animals. This might have been due to a negative energy balance associated with M. paratuberculosis infection.     

Tissue and serum concentrations of amikacin after intramuscular and intrauterine administration to mares in estrus.

Concentrations of amikacin in endometrial tissue and plasma were studied in mares in estrus after intrauterine infusion of 1.0 or 2.0 g once a day for 3 consecutive d, and after 9.7 or 14.5 mg/kg body weight (BW) had been injected intramuscularly once a day for 3 consecutive d to determine concentrations of amikacin sulfate in plasma and endometrial tissues, and whether parenteral administration provides any advantages over intramuscular infusion. No amikacin was detected in serum at the 1.0 g dose. At the infusion dose of 2.0 g once a day, very low levels of serum amikacin were detected at 1 and 4 h postinfusion on the 1st treatment day. Amikacin was found to penetrate the endometrium after intramuscular injection; however, the levels attained were not as high as those achieved following intrauterine infusion. Based on the tissue and serum concentrations of amikacin, an intrauterine infusion at a dose of 4.4 mg/kg BW/d would appear to be an appropriate therapeutic regimen for the treatment of gram-negative endometritis.     

Use of oocyte transfer in a commercial breeding program for mares with reproductive abnormalities

In some mares with lesions of the reproductive tract, embryo collection and survival rates are low, or collection of embryos is not feasible. For these mares, oocyte transfer has been proposed as a method to induce pregnancies. In this report, a method for oocyte transfer in mares and results of oocyte transfer performed over 2 breeding seasons, using mares with long histories of subfertility and various reproductive lesions, are described. Human chorionic gonadotropin or an implant containing a gonadotropin-releasing hormone analog was used to initiate follicular and oocyte maturation. Oocytes were collected by means of transvaginal ultrasound-guided follicular aspiration. Following follicular aspiration, cumulus oocyte complexes were evaluated for cumulus expansion and signs of atresia; immature oocytes were cultured in vitro to allow maturation. The recipient's ovary and uterine tube (oviduct) were exposed through a flank laparotomy with the horse standing, and the oocyte was slowly deposited within the oviduct. Oocyte transfer was attempted in 38 mares between 9 and 30 years old during 2 successive breeding seasons. All mares had a history of reproductive failure while in breeding and embryo transfer programs. Twenty pregnancies were induced. Fourteen of the pregnant mares delivered live foals. Results suggest that oocyte transfer can be a successful method for inducing pregnancy in subfertile mares in a commercial setting.     

Effects of rice bran oil on plasma lipid concentrations, lipoprotein composition, and glucose dynamics in mares

Plasma lipid concentrations, lipoprotein composition, and glucose dynamics were measured and compared between mares fed diets containing added water, corn oil (CO), refined rice bran oil (RR), or crude rice bran oil (CR) to test the hypothesis that rice bran oil lowers plasma lipid concentrations, alters lipoprotein composition, and improves insulin sensitivity in mares. Eight healthy adult mares received a basal diet fed at 1.5 times the DE requirement for maintenance and each of the four treatments according to a repeated 4 x 4 Latin square design consisting of four 5-wk feeding periods. Blood samples were collected for lipid analysis after mares were deprived of feed overnight at 0 and 5 wk. Glucose dynamics were assessed at 0 and 4 wk in fed mares by combined intravenous glucose-insulin tolerance tests. Plasma glucose and insulin concentrations were measured, and estimated values of insulin sensitivity (SI), glucose effectiveness, and net insulin response were obtained using the minimal model. Mean BW increased (P = 0.014) by 29 kg (range = 10 to 50 kg) over 5 wk. Mean plasma concentrations of NEFA, triglyceride (TG), and very low-density lipoprotein (VLDL) decreased (P < 0.001) by 55, 30, and 39%, respectively, and plasma high-density lipoprotein and total cholesterol (TC) concentrations increased (P < 0.001) by 15 and 12%, respectively, over 5 wk. Changes in plasma NEFA (r = 0.58; P < 0.001) and TC (r = 0.44; P = 0.013) concentrations were positively correlated with weight gain over 5 wk. Lipid components of VLDL decreased (P < 0.001) in abundance over 5 wk, whereas the relative protein content of VLDL increased by 39% (P < 0.001). Addition of oil to the basal diet instead of water lowered plasma NEFA and TG concentrations further (P = 0.002 and 0.020, respectively) and increased plasma TC concentrations by a greater magnitude (P = 0.072). However, only plasma TG concentrations and VLDL free cholesterol content were affected (P = 0.024 and 0.009, respectively) by the type of oil added to the diet. Mean plasma TG concentration decreased by 14.2 mg/dL over 5 wk in the CR group, which was a larger (P < 0.05) decrease than the one (-5.3 mg/dL) detected in mares that received water. Consumption of experimental diets lowered S(I), but glucose dynamics were not affected by oil supplementation. Addition of oil to the diet altered blood lipid concentrations, and supplementation with CR instead of water specifically affected plasma TG concentrations and VLDL free cholesterol content.     

Spatial and temporal comparison of selected cancers in dogs and humans, Michigan, USA, 1964-1994

Our aim was to investigate the geographic and time distributions of some biologically similar neoplasms in dogs and humans living in Michigan, USA, between 1964 and 1994. Our objective was to describe and compare the patterns of cancer in the two species while assessing the strength and dependence of those patterns. In this retrospective, registry-based study, histologically confirmed incident human and canine cancer cases were mapped, and second-order (K function) spatial analysis and one-dimensional nearest neighbor temporal analysis were performed on residence addresses and dates of hospital discharge/diagnosis. Included in the study were all 528 incident cases of canine lymphosarcoma, mammary adenocarcinoma, melanoma and spindle-cell sarcomas diagnosed at a veterinary teaching hospital between 1964 and 1994 having residence addresses in Ingham, Oakland, and Wayne Counties; and a stratified random sample of 913 incident human cases of comparable cancers diagnosed during the same time period from the same counties. Results suggest that processes determining spatial aggregation of cases in dogs and humans were not independent of each other, did not act uniformly over different geographic areas, operated at spatial scales <2000 m regardless of species, and tend to act upon dogs more strongly at shorter distances than on humans. Little evidence of interspecies concurrence of temporal clustering was found.     

Detection of methicillin-resistant Staphylococcus aureus (MRSA) in backyard pigs and their owners, Michigan, USA

Methicillin-resistant Staphylococcus aureus (MRSA) have been reported in commercially raised pigs and their human handlers, raising concerns of zoonotic transmission. To determine whether MRSA in backyard-raised pigs is commonly transmitted to their human owners, a matched study of this type of pigs and their owners was conducted in selected counties in Michigan. Nasal swabs from matched owner-pig pairs (n = 50 pairs) with a few unmatched pig (n = 3) and human (n = 4) samples were collected and processed using standard isolation and identification protocols. No matched owner-pig pair was found; however, MRSA was isolated from 1/54 (1.9%) human samples and 2/53(3.8%) of the pigs. The single human isolate was not strain type USA100-1100 by pulsed-field gel electrophoresis (PFGE), was sequence type (ST) 8 by multilocus sequence typing (MLST), possessed SCCmec type IVb and agr I and was negative for the Panton-Valentine leukocidin (PVL) toxin gene. The two pig isolates were indistinguishable by PFGE (not USA100-1100), and both isolates were ST5 by MLST, possessed SCCmec type III and agr II and were negative for the PVL gene. Persons raising backyard swine from the selected Michigan counties had MRSA carriage rates similar to that of the general US population, suggesting that their avocational pig exposure did not increase their risk of MRSA.     

干奶期不同能量摄入对围产期乳牛血液葡萄糖胰高血糖素和胰岛素浓度的影响

将围产期健康乳牛30头随机分为3组，分别于产前第28d开始饲喂标准日粮（能量摄入i00％组）、标准日粮增加20％的日粮（能量摄入120％组）和标准日粮减少20％的日粮（能量摄入80％组），产后备组乳牛均饲喂标准泌乳日粮，至产后第56d结束，观察干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度的影响。结果表明，产前低能饲喂可以增加围产期乳牛血浆葡萄糖浓度，干奶期不同能量摄入水平对围产期健康乳牛血液葡萄糖、胰高血糖素和胰岛素浓度起重要调节作用。