Biomedical subjects

L D Warnick

Publications and source records attributed to L D Warnick.

At least 37 records · Page 2Linked to original sources

PubMed2001

Censoring in survival analysis: a simulation study of the effect of milk yield on conception.

Survival-analysis methods often are used to analyze data from dairy herds where the outcome of interest is the interval from calving to conception. The purpose of this study was to determine whether an association between milk yield and culling biases the estimation of the effect of milk yield on conception. This was done by simulating four different scenarios modeling dairy-cattle milk yield and reproductive performance with known relationships among study factors. Cox's proportional-hazards model was used to analyze the effect of milk yield on days open under the following four scenarios: (1) no association between milk yield and culling or between milk yield and conception; (2) association between milk yield and culling only; (3) association between milk yield and conception only; (4) associations between milk yield and both culling and conception. The analyses also were repeated for data sets with an association between milk yield and culling, but with probabilities of culling ranging from 0.01 to 0.4. An effect of milk production on culling appeared to cause a small increase in the parameter estimates for the association of milk yield and days open - particularly when the probability of culling was high. The effect of high milk production on median days open (as estimated by survival functions) changed by 2 to 4 days when an association between milk yield and culling was programmed in the simulated data sets.

Animals↗

PubMed2001

Teaching dairy herd health dynamics using a web-based program.

INTRODUCTION: This course teaches veterinary students basic principles of epidemiology. Dynamic relationships of dairy herd performance parameters are demonstrated. METHODOLOGY: Courseware combines lectures (both in-class and Web-based) and problem-based exercises using two computer simulation models. The format of this eight-week, one-credit course is a lecture followed by exercises in a computer laboratory working with simulation models. Currently, Cornell University and nine test sites use the courseware. CURRENT STATUS: The course has been taught for two years, with students and experts providing evaluations and critical feedback for courseware modification.

Animals↗

PubMed2001

The effect of lameness on milk production in dairy cows.

Data were collected prospectively for 1.5 yr on two New York dairy farms to investigate the effect of lameness on milk production. The numbers of study cows (percentages treated at least once for lameness) in each herd were 1796 (52%) and 724 (40%), respectively. Lame cows were identified and treated by farm employees or a professional hoof trimmer. Weekly averages of total milk production per day were recorded based on automated milk weight measurements at each milking. The effect of lameness on milk production was analyzed separately for each herd using repeated measures ANOVA. In both herds, milk production decreased significantly for cows diagnosed lame. Milk production was 1.5 kg/d lower > or = 2 wk after lameness compared with cows that had not yet been diagnosed lame in the current lactation in the larger herd. In the second herd, milk production of lame cows was 0.8 kg/d lower in the first and second wk after lameness and 0.5 kg/d lower > or = 3 wk after diagnosis. The decrease in milk production associated with lameness was larger for cows in second or greater lactation and for more severe cases. In one herd, the decrease in milk production was greater for cows with sole ulcers or foot abscesses than for foot rot or foot warts. Cows with abscesses or foot rot tended to have larger decreases in milk production in the other herd. The inconsistent results between farms may have resulted from differences in the relative frequencies of specific causes of lameness in the two herds and in the way lame cows were identified and defined for the study.

Analysis of Variance↗

PubMed2000

Antibiotic residues in milk following bulbar subconjunctival injection of procaine penicillin G in dairy cows.

OBJECTIVE: To determine whether, and at what time, penicillin enters milk at a concentration that is detectable following bulbar subconjunctival injection in lactating dairy cows. DESIGN: Randomized clinical trial. ANIMALS: 66 Holstein cows that were at least 2 weeks past calving and had not been treated with antibiotics in the preceding 30 days. PROCEDURE: Cows were randomly assigned to receive a treatment of 1 ml (300,000 units) procaine penicillin G by bulbar subconjunctival injection or remain untreated. Composite milk samples were collected immediately before treatment and 4, 10, 16, 22, 28, and 40 hours after treatment. Milk samples were tested by use of a commercial test for beta-lactam antibiotics. RESULTS: Among penicillin-treated cows, the first positive test results were observed 4 hours after treatment, and the last positive result was observed 22 hours after treatment. The percentages of positive test results before treatment and at 4, 10, 16, 22, 28, and 40 hours after treatment were 0, 9, 87, 42, 8, 0, and 0%, respectively. None of the untreated cows had positive test results for beta-lactam antibiotics at any sampling time. CONCLUSIONS AND CLINICAL RELEVANCE: Penicillin was detected in milk for up to 22 hours after a single subconjunctival injection of procaine penicillin G in cows. This result should be considered when recommending milk withholding periods following the administration of penicillin by this route in lactating dairy cows.

Animals↗

PubMed2000

Cross-sectional study of the association of abomasal displacement or volvulus with serum electrolyte and mineral concentrations in dairy cows.

The objective of this study was to evaluate serum mineral and electrolyte concentrations at the time of on-farm diagnosis of left displaced abomasum, right displaced abomasum, or abomasal volvulus in dairy cows. Data were collected from 104 affected cows and 96 control cows matched with cases, based on herd, parity, and stage of lactation. Cows with abomasal displacement or volvulus had significantly lower calcium, phosphorous, magnesium, potassium, and chloride concentrations and increased anion gap at the time of diagnosis compared with control cows from the same herds. The percentages of cases and controls with total serum calcium concentrations below the lower limit of the laboratory reference range (2.08 mmol/L [8.3 mg/dL]) were 70% and 23%, respectively. Based on the large percentage of cases with hypocalcemia, administering calcium salts at the time of treatment of field cases of abomasal displacement or volvulus may be beneficial.

Abomasum↗

PubMed1999

Use of a water hardness test kit to measure serum calcium concentration in cattle.

OBJECTIVE: To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows. DESIGN: Prospective study. ANIMALS: 30 dairy cows from 19 commercial herds. PROCEDURE: Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated. RESULTS: There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia. CLINICAL IMPLICATIONS: Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit.

Animals↗

PubMed1998

A toxicity study of eltenac, a nonsteroidal anti-inflammatory drug, in horses.

A double-blind study was performed, in horses, to determine the potential toxic effects of the nonsteroidal anti-inflammatory drug, eltenac(4-[(2,6-dichlorophenyl) amino]-3-thiopheneacetic acid). Four treatment groups of six horses were formed. The drug was injected intravenously, once daily, at a dose level of 0.5 mg/kg, 1.5 mg/kg or 2.5 mg/kg for 15 days. A control group was injected with sterile saline solution. Horses were monitored for changes in appetite, physical examinations, biochemical evaluations and gastroscopic examinations. Complete post-mortem examinations were also performed. A few glandular gastric ulcers, mild in severity, developed in seven animals during the treatment period. This occurred more often in horses treated with high doses of eltenac (P = 0.02). A dose-dependent change of white blood cell (WBC) count and neutrophil count was noted. Total protein, albumin and globulin levels had dose-dependent decreases. One horse in the high dose group (2.5 mg/kg) developed ventral ooedema as well as hypoproteinaemia. Gross post-mortem and histological examination did not reveal any signs of drug related gastrointestinal, renal or hepatic abnormalities. Toxic effects of eltenac given intravenously were greatest in horses treated with 2.5 mg/kg of the compound for 15 days compared to other groups.

Aniline Compounds↗

PubMed1998

Genetic analysis of clinical lameness in dairy cattle.

Scores for clinical lameness from two separate studies were combined, and genetic parameters were estimated based on linear and threshold models. Cows were from 24 herds in Minnesota, Wisconsin, and Virginia. To evaluate clinical lameness, cows were observed walking and were assigned a score between 0 and 4 (where 0 = no observable problems to 4 = inability to walk). Data included 1624 records on 1342 cows. The models included fixed effects of herd visit, parity, and stage of lactation. Random effects were additive genetics, permanent environment to account for repeated records, and residual. Estimates of heritability were 0.10 and 0.22 from the linear and threshold models, respectively. The correlation between ETA from linear and threshold models based on all animals was 0.974. Deregressed ETA of sires and REML were used to estimate genetic correlations between clinical lameness and conformation traits. Among the type traits, foot angle, rear legs (rear view), and rump width had strongest associations with clinical lameness; absolute values for genetic correlations between these traits and clinical lameness were approximately 0.65. Low foot angle, hocking in, and wide rumps were associated with increased clinical lameness. Correlations with strength and body depth ranged from 0.20 to 0.43, indicating that heavier cows were more prone to clinical lameness.

Animals↗

PubMed1998

Timing of insemination for dairy cows identified in estrus by a radiotelemetric estrus detection system.

The optimal time of artificial insemination (AI) was determined from data for 2661 AI in 17 herds utilizing a radiotelemetric system for estrus detection that has the potential for continuous 24-h surveillance to monitor behavioral events associated with estrus. The system consisted of pressure-sensitive radio frequency transmitters affixed over the sacrum region of cows. The activation of the sensor sent a radiotelemetric signal to a microcomputer via a fixed antenna. Cow identification, date, time, and duration of each standing event were recorded in the software program provided with the system. Each farm selected a 3-h interval to AI for cows that were identified in estrus during the previous 24 h. Pregnancy status was determined from data for return to estrus and palpation of the uterus 35 to 75 d following AI. Standing events during estrus averaged (+/- SD) 8.5 +/- 6.6 per cow, and the number of events per estrus across herds averaged from 6.2 +/- 5.1 to 12.8 +/- 9.9 per cow. The duration of estrus ranged from 5.1 +/- 3.8 to 10.6 +/- 6.8 h across herds; the mean was 7.1 +/- 5.4 h. The interval from the first standing event to AI affected the probability of pregnancy; the highest conception rates for AI occurred between 4 and 12 h after the onset of standing activity. The probability of pregnancy was higher for cows > 100 d in milk, exhibiting > 2 standing events during estrus, and inseminated during March, April or May.

Animals↗

PubMed1997

The relationship of calfhood morbidity with survival after calving in 25 New York Holstein herds.

The association of owner-diagnosed calfhood diseases with the length of herd life after calving was evaluated using data collected prospectively over a ten-year period in 25 New York Holstein dairy herds. Herds selected for the study were milking between 35 and 200 Holstein cows, used dairy herd improvement records, bred cows by artificial insemination unless they needed three or more services, and had regularly-scheduled herd health visits by clinicians from the Cornell University College of Veterinary Medicine. Owners recorded occurrences of dullness, respiratory disease, and scours from birth through 90 days of age for all heifer calves that lived at least 24 h and were to be kept as replacements. Milking herd life was measured as the difference between the age at first calving and the age at death or sale. Data on cows sold when the herd went out of business or still in the herd at the end of the study were censored observations. Cox's proportional hazards model was used for statistical analysis of the data. Controlling for age at first calving, study month of birth, and sire predicted difference for milk, there was no statistically significant association of calfhood morbidity with length of herd life. The estimated hazard rate ratios for leaving the milking herd and 95% confidence intervals for dullness, respiratory disease, and scours within 90 days of birth were 1.3 (0.9, 1.9), 0.9 (0.6, 1.3), and 1.0 (0.8, 1.3), respectively. Dullness was the only disease category with an estimated hazard rate ratio greater than 1, and although it was not statistically significant, may warrant evaluation in future studies of long term effects of calfhood morbidity.

Animals↗

PubMed1996

Calcium decreases and parathyroid hormone increases in serum of periparturient mares.

Changes in serum concentrations of Ca and parathyroid hormone (PTH) may develop in periparturient mares, may be influenced by dietary Ca, and may be associated with changes in Ca concentration of mammary secretion. Milk and blood samples were taken from eight mares on Farm A and eight on Farm B for 10 d before parturition and from four mares on each farm for 5 d postpartum. Milk Ca was measured by two commercial tests. Serum samples were analyzed for PTH and total Ca in 16 mares and for ionized Ca in six (Farm A). Parturition was induced in eight mares on Farm A and four on Farm B; no significant difference in serum Ca or PTH was found between mares with induced and spontaneous foaling. Mean serum total Ca decreased from 12.5 mg/dL to a nadir of 11 mg/dL on d 2 postpartum, and mean PTH increased from 46 pg/mL to a peak of 186 pg/mL on d 2 postpartum. Serum total Ca concentrations were lower and serum PTH concentrations were higher in Farm A mares than in Farm B mares, probably reflecting dietary Ca (.35% of DM on Farm A and .55% on Farm B). The serum PTH peak and Ca nadir occurred on d 2 postpartum, 1 d later than reported previously in dairy cows. Milk Ca concentration increased progressively from 7 d before parturition; this increase preceded, so was not dependent on, prepartal changes in serum Ca and PTH.

Animals↗

PubMed1995

The relationship of the interval from breeding to uterine palpation for pregnancy diagnosis with calving outcomes in holstein cows.

This study used data collected prospectively at 32 dairy herds to examine the effect of interval from breeding to uterine palpation for pregnancy diagnosis on calving interval and likelihood of calving. Multivariable statistical models were used to control for other factors that were significantly associated with the outcomes of interest. Cows diagnosed pregnant from 30 to 36 d post breeding had 2-wk longer calving intervals than cows palpated at later intervals. The interval from breeding until a cow was diagnosed open had a significant positive association with the calving interval. The interval to palpation was not associated with the probability of remaining in the herd to calve when controlling for the effects of herd, season of freshening, number of services, days to first service and mature equivalent milk production. Among cows diagnosed pregnant, 3.4% subsequently were bred and 1.5% were diagnosed open by palpation at a later date. About 5% of the cows diagnosed open calved at a time consistent with being pregnant when the diagnosis was made.

Journal Article↗

PubMed1995

Lack of association between calf morbidity and subsequent first lactation milk production in 25 New York Holstein herds.

The association of owner-diagnosed calfhood diseases with first lactation milk production was evaluated using data collected prospectively for 728 heifers from 25 New York dairy herds. Cows diagnosed with one or more occurrences of dullness, respiratory disease, or scours within 90 d of birth had first lactation milk production that was similar to that of unaffected herdmates. Estimates for the effects of dullness, respiratory disease, and scours on second test milk production were -1.0, 1.0, and .4 kg/d, respectively (adjusted for season and age at calving, times milked per day, study month on birth, sire PTA for milk production, and the other two calfhood diseases). Estimates for the effects on 305-day mature equivalent production were -139, 123, and 158 kg for dullness, respiratory disease, and scours, respectively (adjusted for study month of birth, sire PTA for milk production, and the other two calfhood diseases). These results were based on data of heifers that were selected as replacements and remained in the herd long enough to have milk production recorded. There was no significant detrimental effect of owner-diagnosed calfhood disease on first lactation milk production, but affected heifers had higher mortality before calving and were less likely to enter the milking herd.

Animals↗

PubMed1995

Effect of phenylbutazone and flunixin meglumine on acute toxic mastitis in dairy cows.

A double-blinded randomized prospective clinical trial was designed to evaluate the effectiveness of flunixin meglumine and phenylbutazone for treatment of acute toxic mastitis in dairy cows. All cows were treated 4 times at 12-hour intervals by intramammary infusion of gentamicin (150 mg). A total of 45 dairy cows with toxic mastitis were randomly assigned to 1 of 3 treatment groups: group 1 (control), saline solution, IV; group 2, 1 g of flunixin meglumine, IV; or group 3, 4 g of phenylbutazone, IV. Physical examination and udder variables were assessed at initial examination and 24 hours later. Milk production was recorded at regular intervals from 1 week before until 10 weeks after development of mastitis. Rear quarters (34/45) were more commonly affected than front quarters. Thirty-five cows returned to the herd, 9 cows were culled, and 1 cow died. There were no significant differences among treatment groups in the need for further treatment or outcome. Klebsiella spp (18/45) and Escherichia coli (16/45) were the most common pathogens isolated by culture of milk from affected quarters. The overall bacteriologic cure rate on days 7 and 14 was 64 and 75%, respectively. At the time of initial examination, cows of the control group had higher rectal temperature than did cows of the flunixin group. At the examination 24 hours later, the rectal temperature of cows in all treatment groups was lower than the temperature at initial examination; at that time (24 hours), however, there were no significant differences in temperature among the treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1994

Relationships between administration of GnRH, body condition score and fertility in Holstein dairy cattle.

The objective of this study was to determine the effect of GnRH treatment in dairy cows differing in body condition score. A total of 2437 primiparous and multiparous cows was allocated randomly to receive either GnRH (100 microg) or placebo at the post partum exam (25 to 35 d) and at the first breeding. Complete records were available from 1906 cows: Group 1 (n = 535) placebo and placebo; Group 2 (n = 489) GnRH and placebo; Group 3 (n = 438) placebo and GnRH; and Group 4 (n = 444) GnRH and GnRH. The change of body condition score during early lactation was determined on a 1 to 5 scale (1 = emaciated to 5 = obese). Cows with a high body condition score (> or =3.0) at the first breeding had 8.8 fewer days to first service and 6.4 fewer days open but more services per conception (0.16) than cows with low body condition score (<3.0). Conception rate improved when GnRH was administered at the first breeding to cows with a body condition score of <3.0 at the first breeding regardless of parity. The administration of GnRH at the post partum exam decreased the conception rate in first lactation cows but was beneficial for cows in second and greater lactations. Thus the efficacy of GnRH may not be consistent in all parities and body condition groups.

Journal Article↗

PubMed1992

Daily variability of equine fecal strongyle egg counts.

Fecal egg counts often are used for diagnosing equine strongyle infections and estimating the number of eggs shed in the feces. An individual egg count should be interpreted in view of the normal fluctuation of egg numbers in an individual horse. In this study, the daily variability of strongyle fecal egg counts from horses was investigated. The Cornell-McMaster egg-counting technique was used to estimate the eggs per gram of feces in repeated daily fecal samples from 39 horses. The variation of the daily egg counts across 4 days was greater than would be expected if a consistent number of eggs were produced and dispersed randomly in the feces. The means and variances of the daily counts from each horse had a logarithmic relationship. For practical purposes, however, the fluctuation of egg counts is low enough for the fecal egg count to be used to identify horses for treatment, to estimate pasture contamination, or to assess response to therapy.

Animals↗

PubMed1991

A case-control study of the association between blood selenium and cystic ovaries in lactating dairy cattle.

We carried out a case-control study to investigate the association between the risk of developing cystic ovaries and the concentrations of Se in the blood of dairy cows. Cows were from dairy herds in the vicinity of Ithaca, NY. One hundred and thirty-two cystic ovary cases were identified; a similar number of herdmates who did not have cystic ovaries were selected as controls. Whole blood samples were collected from cystic cows and controls in which Se concentrations were determined. Milk samples also were collected and analyzed for concentrations of progesterone. Multivariate logistic regression analysis was used to identify the role of Se in the risk of developing cystic ovaries while controlling for other possible risk factors. Mean Se in blood concentration for cows with cystic ovaries (141 ng/ml) was similar to that of control cows without cystic ovaries (136 ng/ml). The concentration of progesterone in milk was significantly higher in controls than in cows with cystic ovaries. In the multivariate logistic regression analysis, cows with concentrations of Se in blood greater than 169 ng/ml had twice the risk of developing cystic ovaries compared with cows that had Se levels less than 108 ng/ml.

Age Factors↗

PubMedDate not supplied

Efficacy of an epidural combination of morphine and detomidine in alleviating experimentally induced hindlimb lameness in horses.

Amphotericin B-induced synovitis of the left tarsocrural joint was used to create a grade 3 of 4 lameness in 11 horses. Caudal epidural catheters were placed and advanced to the lumbosacral region. Baseline heart and respiratory rates were recorded and horses were videotaped at a walk and trot. Morphine sulphate (0.2 mg/kg) and detomidine hydrochloride (30 micrograms/kg) were administered to treated horses (n = 8) through the epidural catheter; an equivalent volume of physiologic saline solution was administered to control horses (n = 3) through the catheter. At hourly intervals after epidural injection for a total of 6 hours, heart and respiratory rates were recorded, and horses were videotaped walking and trotting. At the end of the observation period, video recordings were scrambled onto a master videotape. Lamenesses were scored by three investigators unaware of group assignment or treatment time. Lameness scores, heart rates, and respiratory rates were compared between groups using repeated measures analysis of variance. There was a significant decrease in lameness score after treatment with epidural morphine and detomidine (P = .0003); average lameness scores of treated horses were less than grade 1 at each hourly observation for 6 hours after drug administration. Early in the observation period, heart rates significantly increased in control horses and decreased in treated horses (P = .03). A similar trend occurred for respiratory rates (P = .07). Results of this study demonstrate that epidural administration of a combination of morphine and detomidine is capable of providing profound hindlimb analgesia in horses.

Adrenergic alpha-Agonists↗