Estimating genetic parameters for fertility in dairy cows from in-line milk progesterone profiles.

The aim of this study was to define endocrine fertility traits from in-line milk progesterone (P4) records and to estimate genetic parameters for these traits. Correlations of classical fertility (calving interval and calving to first service) and milk production traits with endocrine fertility traits were also estimated. In-line milk P4 records (n=160,952) collected from June 2009 through November 2013 for 2,273 lactations of 1,561 Holstein-Friesian cows in 12 commercial herds in the Netherlands were analyzed for (the log of) the number of days from calving till commencement of luteal activity (lnC-LA), proportion of samples between 25 and 60 d in milk with luteal activity (PLA), presence or absence of luteal activity for a cow between 25 and 60 d in milk, interval from commencement of luteal activity to first service (CLAFS), first luteal phase length, length of first interluteal interval, and length of first interovulatory interval. Milk P4 records were sampled, on average, every 2 d. Genetic parameters were estimated using a mixed linear animal model. Heritability estimates (±SE) of endocrine fertility traits were 0.12±0.05 for lnC-LA, 0.12±0.05 for PLA, and 0.11±0.06 for CLAFS, and their repeatability estimates were 0.29±0.04, 0.21±0.04, and 0.15±0.06, respectively. The genetic correlation of lnC-LA with PLA was -0.91±0.06 and with CLAFS was -0.56±0.25. The genetic correlations of lnC-LA were 0.26±0.33 with calving interval and 0.37±0.21 with calving to first service. Genetic correlations of the milk production traits with lnC-LA ranged from 0.04 to 0.18 and 0.07 to 0.65 with classical fertility traits. The phenotypic correlations of all endocrine fertility traits with milk production traits were close to zero (0.01 to 0.07). This study shows that in-line P4 records can be used to define and explore several heritable endocrine fertility traits in dairy cows and might help in selection for improved fertility.

Preventive strategies and risk factors for milk fever in Danish dairy herds: a questionnaire survey.

Milk fever is a commonly recognized production disease in dairy cows around parturition. The aim of this questionnaire survey was therefore to investigate milk fever preventive strategies used in Danish dairy herds during 1998, to explore the reasons for choosing a specific strategy, and finally to evaluate possible risk factors for milk fever occurrences. A random sample of 230 milk producers (MP) was drawn from the Danish Cattle Database. A telephone interview (TI) was used to collect data. A sub-sample of 25% MPs was chosen by systematic random sampling and interviewed a second time (TI(2)). Descriptive analysis of all answers was performed. The agreement between TI(1) and TI(2) was evaluated using Cohen's kappa coefficient and the overall intra-MP agreement. Risk factors (such as housing systems or use of milk fever preventive strategies) for differences in milk fever incidences between herds were evaluated using logistic regression. This investigation revealed that Danish MPs focused on a few well-described milk fever preventive principles and other management methods, such as reduced milking and management of body condition. There was no significant difference in risk of developing milk fever using different prevention strategies (p=0.80). Furthermore, the logistic regression did not indicate an association between reported milk fever cases and the assessments of this as a problem or not (p=0.09). Tie stalls increased the risk of milk fever compared to loose housing systems (p=0.019). There was a significant difference in risk of milk fever between parities. The overall milk fever incidence risk was 3.0%.

Milk fever control in Danish dairy herds.

The objective of the present study was to investigate the milk fever preventive strategies used by a representative group of Danish Milk Producers (MP). A telephone interview was performed in 1999. A total of 230 MPs were called and asked about how they prevented milk fever in the previous year. Three interviewers performed these interviews. The study was completed within 2 1/2 months. A total of 184 MP (80%) completed the telephone interview. Of these, 149 (81%) indicated to use an active effort to prevent milk fever. In the single animal, the preferred strategy was per oral drenching with calcium containing products around calving. The convenience of application of the product was the most decisive single factor. In groups of animals feeding strategies (preferably diets low in calcium) were prioritized. Management (for example preventing fat cows at calving) was used frequently as preventive tool against milk fever. The Danish MP uses internationally documented milk fever preventive strategies, but some empirical management factors seem to count as much as the scientific proven methods.

Milk fever and subclinical hypocalcaemia--an evaluation of parameters on incidence risk, diagnosis, risk factors and biological effects as input for a decision support system for disease control.

The present review analyses the documentation on incidence, diagnosis, risk factors and effects of milk fever and subclinical hypocalcaemia. It is hereby evaluated whether the existing documentation seems sufficient for further modelling in a decision support system for selection of a control strategy. Several studies have been carried out revealing an incidence of milk fever most often in the level of 5-10%. Few studies indicate that the incidence of subclinical hypocalcaemia is several times higher than milk fever. The diagnosis based on clinical or laboratory methods or based on presence of risk factors is outlined. The clinical symptoms of milk fever are highly specific and the disease level may thus be determined from recording of treatments. Diagnosis of subclinical hypocalcaemia needs to include laboratory examinations or it may be determined by multiplying the incidence of milk fever by a certain factor. From the documentation on risk factors, it is very complex to predict the incidence from the exposure level of the risk factors. Due to uncertainty, sensitivity analyses over a wide range of values for each parameter are needed. The documentation of cow characteristics, nutrition, environment and management as risk factors are described. Among cow characteristics, parity or age, body condition and production level were found to be important. Risk factors associated with nutrition included most importantly dietary cation-anion difference and calcium level whereas the importance of general feeding related factors like type of feed stuff and feeding level were less clear. Environment and management included season, climate, housing, pasturing, exercise, length of dry period and prepartum milking. Several of the parameters on environment and management were confounded among each other and therefore firm conclusions on the importance were difficult. The documentation of the effect of milk fever includes the downer cows, reproductive disorders, occurrence of other diseases and the effect on milk production, body weight and culling. The reproductive disorders included most importantly dystocia, uterine prolapse, retained placenta, metritis and repeat breeding, and occurrence of other diseases included ketosis, displaced abomasum and mastitis. The documentation was substantial and often quantifiable within certain limits. Overall it is concluded that the present documentation on milk fever concerning incidence, diagnosis, risk factors and effects seems sufficient for a systematic inclusion in a decision support system. A model on milk fever should take into consideration the variation in biological data and individual herd characteristics. The inclusion of subclinical hypocalcaemia would be more uncertain and probably should await further documentation on possibilities of determining the herd level incidence and also the effect of this condition on production.

Viral aetiology of enzootic pneumonia in Danish dairy herds: diagnostic tools and epidemiology.

Ten outbreaks of calf respiratory disease in Danish dairy herds were investigated by lung lavage, and in eight of the herds paired blood samples were tested serologically. In six of the 10 herds bovine respiratory syncytial virus (BRSV) antigen was detected in the lung lavage fluids. In only one calf was coronavirus and BRSV detected simultaneously. The paired blood samples confirmed that four of the herds were BRSV-infected, and in one herd the BRSV infection was diagnosed by the paired blood samples alone. Significant increases in antibody titres against coronavirus were observed in two herds, both in combination with other virological agents. No adenovirus antigen was detected in any of the lavage samples, but in two herds a significant increase in antibody titres against adenovirus was observed. Parainfluenza-3 (PI-3) virus was not detected in the lung lavage fluids, and in four of the herds, no antibodies to PI-3 were detected. In three herds no viral involvement could be found. The findings suggest that BRSV may be an important causative agent in calf respiratory disease in Denmark, even in very young calves.

Numbers of airborne bacteria and fungi in calf houses.

Counts of airborne bacteria colony forming particles (BCFP) and fungi were made at intervals throughout one year in three calf houses using a six stage Andersen Sampler. House 1 was insulated, mechanically ventilated and heated, House 2 was insulated and provided with a controlled natural ventilation system, while House 3 was uninsulated with natural ventilation. Each house contained 36 bought-in bull calves. Every six weeks the 12 oldest calves were removed and replaced by 12 four-week-old calves. The mean count of BCFP was highest in House 2 (101.6 X 10(3) m-3) and lower in House 3 (67.6 X 10(3) m-3). The mean count of aerial fungi was significantly lower in House 3 (40.5 X 10(3) m-3) than in Houses 1 and 2 (119.3 X 10(3) m-3 and 127.1 X 10(3) m-3, respectively). The count of aerial BCFP and fungi showed large seasonal fluctuations, but there was a general trend towards lower counts during the winter period. The mean incidence rate of respiratory disease among the experimental calves was 67.7%. The highest mean incidence rate was recorded in House 2, but differences between houses were not significant. The results are discussed in relation to the environmental requirements for raising of calves, and in the light of the current concept of air hygiene as a major predisposing factor in the web of causation of calf respiratory disease.

The relationship between serum immunoglobulin values and incidence of respiratory disease and enteritis in calves.

Serum immunoglobulin levels were tested in 193 neonatal calves by use of the glutaraldehyde coagulation test. Hypo- and agammaglobulinaemia was found in 26.4% of the calves. A close relationship was found between immunoglobulin levels and the incidence of enteritis and mortality, while the number of calves suffering from both enteritis and respiratory disease was higher in immunoglobulin-deficient calves. The application of specific preventive measures to immunoglobulin-deficient calves is discussed.