Y.T. Gröhn

Ecology and transmission of Listeria monocytogenes infecting ruminants and in the farm environment.

ABSTRACT A case-control study involving 24 case farms with at least one recent case of listeriosis and 28 matched control farms with no listeriosis cases was conducted to probe the transmission and ecology of Listeria monocytogenes on farms. A total of 528 fecal, 516 feed, and 1,012 environmental soil and water samples were cultured for L. monocytogenes. While the overall prevalence of L. monocytogenes in cattle case farms (24.4%) was similar to that in control farms (20.2%), small-ruminant (goat and sheep) farms showed a significantly (P < 0.0001) higher prevalence in case farms (32.9%) than in control farms (5.9%). EcoRI ribotyping of clinical (n = 17) and farm (n = 414) isolates differentiated 51 ribotypes. L. monocytogenes ribotypes isolated from clinical cases and fecal samples were more frequent in environmental than in feed samples, indicating that infected animals may contribute to L. monocytogenes dispersal into the farm environment. Ribotype DUP-1038B was significantly (P < 0.05) associated with fecal samples compared with farm environment and animal feedstuff samples. Ribotype DUP-1045A was significantly (P < 0.05) associated with soil compared to feces and with control farms compared to case farms. Our data indicate that (i) the epidemiology and transmission of L. monocytogenes differ between small-ruminant and cattle farms; (ii) cattle contribute to amplification and dispersal of L. monocytogenes into the farm environment, (iii) the bovine farm ecosystem maintains a high prevalence of L. monocytogenes, including subtypes linked to human listeriosis cases and outbreaks, and (iv) L. monocytogenes subtypes may differ in their abilities to infect animals and to survive in farm environments.

Epidemiology of reproductive performance in dairy cows

The objectives of this presentation are to review results of our previous and on-going research with respect to the risk factors and consequences of poor reproductive performance in dairy cows, and to develop an economic framework to optimize decisions related to dairy cow reproductive performance. To make profitable breeding and replacement decisions, the farmer must account for factors including age, production level, lactation stage, pregnancy status, and disease history of the cows in the herd. Establishing the interrelationships among disease, milk yield, reproduction, and herd management is necessary for developing a decision model for disease treatment, insemination, and replacement. The data for the studies reviewed in this presentation incorporate health, production, and management components from Holsteins in the Northeast USA and Ayrshires from Finland. Data were analyzed using the Cornell Theory Center Supercomputer. The effect of risk factors on reproductive disorders was modeled with logistic regression, and on conception, insemination, and culling with survival analysis. The effect of reproductive disorders on milk yield was analyzed with mixed models. Economic optimization of reproductive performance was done with dynamic programming (DP). High milk yield, high parity, and calving in winter were risk factors for several reproductive disorders. These disorders, in turn, delayed insemination and conception in dairy cows, and some of them increased the risk of culling. Dystocia, retained placenta, and early metritis led to a short-term drop in milk production. High milk yield was not a major factor in delaying conception, except in first parity cows. However, higher yielders were more likely to be inseminated, and less likely to be culled. Non-pregnant cows had a higher risk of being culled. Reproductive performance of dairy cows influenced a herds profitability, and good heat detection and conception rates provided opportunities for management control. It was not always economically advantageous to get cows pregnant as soon as possible, and there was no one optimal value for the calving interval length for all cows in a herd.

Epidemiology of reproductive disorders in dairy cattle: associations among host characteristics, disease and production

Logistic regression was used to investigate the effects of host characteristics, production and 23 veterinary diagnoses on the risks of 10 reproductive disorders. For each reproductive disease in each lactation record, all prior disease events in that lactation were examined as possible risk factors. To make an equal opportunity for risk-factor diseases to be counted as present in both cases and controls, a dummy days in milk (DIM) variable was assigned to control records. The assignment was random, but in proportion to the distribution of the DIM for the cases of that disease. The data set was based on 61 124 Finnish Ayrshire cows, from milk-recorded herds, who calved during 1983. Each cow was under observation for 2 days before calving to the following calving or to removal from the herd. Twenty percent of the cows were treated by a veterinarian for reproductive disorders. Lactational incidence rates (%) were: dystocia, 1.2; prolapsed uterus, 0.2; retained placenta, 4.4; early metritis, 2.3; silent heat, 4.9; cystic ovary, 6.8; prolapsed vagina, 0.1; late metritis, 1.1; other infertility, 2.1; abortion, 0.4. The risk of silent heat and other infertility decreased and the risk of dystocia (after the first calving), retained placenta and ovarian cyst increased with increased parity. Parity did not explain the incidences of the other reproductive disorders. The cows calving during September-February (the dark season) had higher risks of early metritis, silent heat, cyst and other infertility than those calving during the light season. Higher herd milk yield in the previous lactation increased the risks of retained placenta, early metritis and late metritis; higher herd yield in the current lactation increased risks of dystocia and of ovarian cyst. The risks of retained placenta, early metritis, silent heat, ovarian cyst, other fertility and abortion also increased with increased individual-cows milk yield. Most reproductive disorders were interrelated. Six non-reproductive disorders (non-parturient paresis, udder edema, indoor and outdoor hypomagnesemia, rumen acidosis and chronic mastitis) were not risk factors for any of the reproductive disorders. Of the other non-reproductive disorders, clinical parturient paresis was a risk factor for dystocia, prolapsed uterus, retained placenta, and early metritis; clinical ketosis was associated with silent heat, cystic ovary and other infertility; disorder of the abomasum, traumatic recticuloperitonitis, acute mastitis and foot or leg injury also contribited to early metritis. No disorders were protective.

The Cost of Generic Clinical Mastitis in Dairy Cows as Estimated by Using Dynamic Programming

The objective of this study was to estimate the cost of generic clinical mastitis (CM) in high-yielding dairy cows given optimal decisions concerning handling of CM cases. A specially structured optimization and simulation model that included a detailed representation of repeated episodes of CM was used to study the effects of various factors on the cost of CM. The basic scenario was based on data from 5 large herds in New York State. In the basic scenario, 92% of the CM cases were recommended to be treated. The average cost of CM per cow and year in these herds was

The cost of different types of lameness in dairy cows calculated by dynamic programming.

71. The average cost of a CM case was

Culling of dairy cows. Part I. Effects of diseases on culling in Finnish Ayrshire cows

179. It was composed of

The Effect of Calfhood Diseases on Growth of Female Dairy Calves During the First 3 Months of Life in New York State

115 because of milk yield losses,

The effect of maternally derived immunoglobulin G on the risk of respiratory disease in heifers during the first 3 months of life

14 because of increased mortality, and

Salmonella enterica Serotype 4,5,12:i:−, an Emerging Salmonella Serotype That Represents Multiple Distinct Clones

50 because of treatment-associated costs. The estimated cost of CM was highly dependent on cow traits: it was highest (

Effects of clinical mastitis caused by gram-positive and gram-negative bacteria and other organisms on the probability of conception in New York State Holstein dairy cows

403) in cows with high expected future net returns (e.g., young, high-milk-yielding cows), and was lowest (