Estimated prevalence of Mycobacterium avium subspecies paratuberculosis infection in herds of dairy goats in France.

A study of the prevalence of Mycobacterium avium subspecies paratuberculosis (MAP) infection in dairy goats was carried out in France, using a serological ELISA. One hundred and five herds were randomly selected in different regions, and all the goats aged six months or older (11,847 goats) were sampled. An estimation had previously been made of the accuracy of the ELISA, and the Rogan-Gladen estimator was used to convert apparent prevalence values into estimates of true prevalence values. Given that sensitivity and specificity at herd level are functions of sample size, and because the sizes of the herds varied considerably, the true prevalence of infection at herd level was estimated using a weighted average depending on the herd size stratum. At the level of the individual animal, the total true prevalence was estimated by applying a weighted average in accordance with the regional distribution of the animals in the target population. At herd level, apparent prevalence and estimated true prevalence were 55.2 and 62.9 per cent, respectively; at individual animal level they were 2.9 and 6.6 per cent, respectively. In herds that were seropositive for MAP, the average within-herd apparent prevalence was 5.9 per cent and the estimated average within-herd true prevalence was 11.1 per cent.

Effects of sire and dam genotype for complex vertebral malformation (CVM) on risk of return-to-service in Holstein dairy cows and heifers.

The emergence of a new hereditary disease, called "Complex vertebral malformation" (CVM), has been described in Holstein cattle population. This paper studied the incidence of mating concerning Holstein dairy cattle with CVM in Brittany and the possible influences of CVM status for sires and dams on return-to-service at different intervals post-service in cows and heifers. It was carried out based on a set of data for first and second inseminations between 1998 and 2001 in cows (n=530,538) and heifers (n=248,140). Incidence of matings between CVM gene carriers, between a carrier bull and a non-carrier cow and between a non-carrier bull and a carrier cow were estimated to be 1.4, 10.6 and 9%, respectively (1.1, 9.3 and 10.9%, respectively in heifers). Compared to CVM-free mating, the relative risk of return-to-service was increased when the sire was a CVM carrier and the dam was at risk of being a carrier, especially for late return (>25 days post-service). When the sire alone was a carrier, the relative risk was increased whenever the return occurred at a low but significant level. Following mating between a non-carrier bull and a dam at risk of being a carrier, the risk of return-to-service decreased at a low but significant level, whatever the interval in the heifers but only for 19-25 days intervals in the cows.

Effect of disease on reproduction in the dairy cow: a meta-analysis.

Effects on reproduction of dystocia, stillbirth, abortion, milk fever, retained placenta, metritis, cystic ovaries, anestrus, ketosis, displaced abomasum, locomotor disorders, and mastitis were reviewed. Papers were considered if they provided quantitative estimates of diseases on days to first estrus, days to first service, conception rate at first service, days from first service to conception, days to conception or days open, calving interval, conception rates at various days post partum (dpp), and number of services per conception or per cow. Only papers in English in peer-reviewed journals were selected for analysis of post 1960 data from intensive dairy regions. Seventy papers fulfilled the selection criteria. Summary estimates of disease effects were calculated according to meta-analysis methods, and study designs were described in detail to identify possible heterogeneity of the results. Stillbirth, milk fever, displaced abomasum and mastitis had no effect on reproduction. Clinical ketosis, dystocia and retained placenta were associated with 2 to 3 more days to first service and with a 4 to 10% lower conception rate at first service, resulting in 6 to 12 more days to conception. Locomotor disorders were associated with an average increase of 12 d to conception, with wide variation depending on lesions and stage of occurrence. Metritis was associated with 7 more days to first service, 20% lower conception rate at first service, resulting in 19 more days to conception. Cystic ovaries were associated with 6 to 11 more days to first service and with 20 to 30 more days to conception. Anestrus was associated with 26 more days to first service and with an 18% lower conception rate at first service, resulting in 41 more days to conception. Abortion was associated with 70 to 80 more days to conception.

High prolificacy in Belle-Ile sheep (Brittany, France): major effects of a putative single gene and the Awh colour gene on ovulation rate and litter size.

Ovulation rate (OR) and litter size (LS) were recorded in 72 ewes from a traditional sheep population native to Belle-Ile en Mer, France (BI) from 1986 to 1996. Mean, range and repeatability of OR were: 2.54 +/- 1.1 (n = 494), 1-8 and 0.8, respectively, whereas, for LS, they were: 2.23 +/- 1.0 (n = 146), 1-7 and 0.2, respectively. OR is significantly influenced by age, number of OR, maximum OR in the dam (< or = 3 versus > 3), sire and colour of the fleece (white versus black pattern). OR was also recorded in Charmoise ewes (CH), their F1 progenies with four BI rams and BI ram x F1 backcross ewes (BC). OR range and OR mean in CH ewes, four F1 progenies and BC ewes were: 1-2 and 1.2, 1-2 and 1.2, 1-2 and 1.3, 1-3 and 1.9, 1-4 and 2.3, 1-6 and 2.8, respectively. OR repeatability in CH, F1 and BC were 0.16, 0.45 and 0.71, respectively. The large variation in ovulation rate and litter size combined with high repeatabilities, the familial transmission of a high ovulation rate and the observations in F1 and BC support the hypothesis of a single gene with a large mean effect on ovulation rate and litter size segregating in the population.

A framework for animal health management.

In modern production systems, the most economically limiting diseases are multifactorial enzootic health disorders. Relevant decisions in health management have to be based on rational procedures. A first-level approach implies the use of quantitative information on the economic impact of the disease. A more relevant approach of decisions regarding health problems consists of evaluating the economic worth of the interventions in terms of cost-effectiveness. Decision analysis and decision support are of interest today, particularly for herd health control schemes regarding enzootic disorders.