Herd Of Dairy Cows Research Articles

Amelioration of thermal stress impacts in dairy cows

Heat stress negatively impacts on a variety of animal production parameters. Advances in management strategies have alleviated some of the negative impacts of thermal stress on farm animals, but production continues to markedly decrease during heat events in summer, particularly in dairy cattle. In this paper we introduce a Dairy Risk Assessment Program (DRAP). The DRAP is a user-friendly software package designed to assist users in predicting heat loads in dairy cow herds. DRAP was developed over three Australian summers using climatic data (temperature, humidity, solar radiation and wind speed), cow production data (milk yield and milk quality), and physiological data (respiration rate and body temperature). The data were used to develop mathematical algorithms which can predict animal response to climatic variables. This software package is designed to be used by the dairy industry to better manage cows during times of elevated environmental temperatures by equipping producers, managers, and dairy industry personnel with Dairy Heat Load Index (DHLI) values which were calculated based upon site information, stock characteristics, management practices, and mitigation variables specific to their dairy production unit. When a heat event is imminent producers can then introduce management strategies such as providing shade or additional water troughs or implementation of nutritional strategies. Some of these nutritional strategies include dietary chromium picolinate, betaine and antioxidant supplementation or altering the rate of starch fermentation. These nutritional strategies are discussed at some length in this paper.

Trends in greenhouse gas emissions from consumption and production of animal food products – implications for long-term climate targets

To analyse trends in greenhouse gas (GHG) emissions from production and consumption of animal products in Sweden, life cycle emissions were calculated for the average production of pork, chicken meat, beef, dairy and eggs in 1990 and 2005. The calculated average emissions were used together with food consumption statistics and literature data on imported products to estimate trends in per capita emissions from animal food consumption. Total life cycle emissions from the Swedish livestock production were around 8.5 Mt carbon dioxide equivalents (CO2e) in 1990 and emissions decreased to 7.3 Mt CO2e in 2005 (14% reduction). Around two-thirds of the emission cut was explained by more efficient production (less GHG emission per product unit) and one-third was due to a reduced animal production. The average GHG emissions per product unit until the farm-gate were reduced by 20% for dairy, 15% for pork and 23% for chicken meat, unchanged for eggs and increased by 10% for beef. A larger share of the average beef was produced from suckler cows in cow–calf systems in 2005 due to the decreasing dairy cow herd, which explains the increased emissions for the average beef in 2005. The overall emission cuts from the livestock sector were a result of several measures taken in farm production, for example increased milk yield per cow, lowered use of synthetic nitrogen fertilisers in grasslands, reduced losses of ammonia from manure and a switch to biofuels for heating in chicken houses. In contrast to production, total GHG emissions from the Swedish consumption of animal products increased by around 22% between 1990 and 2005. This was explained by strong growth in meat consumption based mainly on imports, where growth in beef consumption especially was responsible for most emission increase over the 15-year period. Swedish GHG emissions caused by consumption of animal products reached around 1.1 t CO2e per capita in 2005. The emission cuts necessary for meeting a global temperature-increase target of 2° might imply a severe constraint on the long-term global consumption of animal food. Due to the relatively limited potential for reducing food-related emissions by higher productivity and technological means, structural changes in food consumption towards less emission-intensive food might be required for meeting the 2° target.

Study of animal welfare status in dairy cow herds in Hungary – looking for causes of lameness

In the last 20–30 years lameness in cattle was found to be third the most influential disease next to mastitis and reproduction disorders. Studies have been established to explore reasons for lameness and prevention. The problem with more robust prevention plans is that knowledge and research evidence is not strong enough to run an effective prevention plan. The aim of the research is to look for reasons of lameness by observing number of cows on 6 farms during 2 lactations. Performance data will be put together to body condition score (BCS) and lameness scores. Other examination is focused on monitoring of 40 farms. This part of the project is more related to extension, collecting and sharing solutions for decreasing lameness. Producers are advised what kind of measures are possible to reduce occurrence of lameness. Effectiveness of those actions will be measured at the end of the study. The first preliminary results show lack in almost all preventive measures needed to be taken in minimising lameness. Those areas are related to poor facilities, lack of straw, problems with labour and basic management.

Clinical endometritis in an Argentinean herd of dairy cows: Risk factors and reproductive efficiency

The objectives of this study were to assess the clinical and metabolic risk factors for clinical endometritis, the likelihood for having a normal vaginal discharge during postpartum, and the effects of endometritis on milk yield, reproductive efficiency, and metabolic status in Holstein cows. The study was conducted in a commercial dairy herd (Cordoba, Argentina) where 303 Holstein cows were enrolled. Cows were body condition scored (1 to 5) and tail bled on −14, 7, 21, 31, 41, and 50d relative to parturition. Cows having a vaginal discharge with presence of pus between 21 and 41d postpartum (dpp) were diagnosed as having clinical endometritis. Plasma blood samples were analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), and blood urea nitrogen using commercial kits and insulin-like growth factor 1, insulin, and leptin by RIA. Data were analyzed with PROC MIXED, PROC GENMOD, and PROC PHREG of SAS (SAS Institute Inc., Cary, NC). Abnormal calving and puerperal metritis increased the risk for endometritis [adjusted odds ratio (AOR)=2.21 for both]. High prepartum NEFA and high postpartum BHBA increased the risk for endometritis (AOR=1.003 and 1.001, respectively), whereas high prepartum blood urea nitrogen reduced it (AOR=0.853). Cut-offs of 456.6μM NEFA and 402.5μM BHBA had sensitivities of 0.69 and 0.58, and specificities of 0.88 and 0.86, respectively. The likelihood for having normal vaginal discharge increased with time (∼1% × dpp) and with normal calving. Cows with endometritis had higher milk yield than normal herdmates (27.8±0.9 vs. 25.7±0.4kg/d), lower risk for pregnancy by 100dpp (AOR=0.10), higher nonpregnancy risk by 200dpp (AOR=2.87), and higher risk for culling than normal cows (AOR=2.28). Cows with endometritis had a lower hazard rate (0.44) for pregnancy and had approximately 70d longer calving-to-conception intervals. Finally, endometritis had no effect on metabolic hormones. In conclusion, the risk for clinical endometritis increases with abnormal calving and puerperal metritis, as prepartum NEFA and postpartum BHBA concentrations increase. Prepartum NEFA and postpartum BHBA could be useful for the prediction of endometritis. Last, clinical endometritis has detrimental effects on reproductive efficiency, as affected cows take longer to get pregnant and are at higher risk for culling.

IDEXX Milk Pregnancy Test

Accurate and timely detection of pregnancy in dairy cows is an essential component of any bovine reproductive management program. Veterinarians and farmers use detection of non-pregnant (open) cows to make decisions regarding re-breeding of cattle and to manage calving intervals, thereby maximizing milk production and revenue for the farm. Increased profits result from many areas, including decreased average days-in-milk for the lactating herd, additional milk yield, less culling of cows due to reproductive failure, and less variation in lengths of lactation and dry period. Currently, pregnancy is determined by rectal palpation, transrectal ultrasound of the cow, or laboratory-based testing of blood samples. IDEXX has recently developed an enzyme-linked immunoassay (ELISA) for the detection of pregnancy-associated glycoproteins (PAGs) in milk samples to provide another laboratory-based method for the accurate detection of pregnancy, which could provide an important tool for the identification of open cows in dairy herds.

Integration into the dairy cow herd: Long-term effects of mother contact during the first twelve weeks of life

The objective of this study is to investigate the long-term effects of mother rearing on the ability to cope with the challenge of integration into the cow herd shortly before first parturition. Four groups of heifers with different levels of contact with their mothers during the first twelve weeks of life were compared. Two rearing groups were fed via an automatic milk feeder two (A2, n=5) or six times (A6, n=5) a day. The animals in these groups were compared to two treatment groups that were either kept separate from the cow herd and with limited contact with their mothers (M2, n=9) or permanent access to the herd and their mothers through selection gates (MP, n=7). At the age of 25±0.2months, heifers were integrated individually into the cow herd and observed for 33h. Social and other behaviour of each heifer was recorded by continuous behaviour sampling, and the identity of the nearest neighbour was determined by time sampling every 5min. Additionally, faecal samples were taken for measurement of adrenocortical activity. For statistical analysis ANOVA was performed with treatment and breed as fixed factors and herd size, except for social behaviour as covariate. For post hoc testing, heifers were allocated to groups according to contact with the mother (M2 and MP; mother) i.e. suckling by the mother compared to automatic feeding (A2 and A6; automat) and according to contact with the herd (MP; permanent suckling vs. M2, A2, A6; no herd). The treatment groups tended to differ in the frequency of self grooming (p=0.102), with mother-heifers tending to self-groom more often than automat-heifers (p=0.109). Permanent suckling-heifers performed self-grooming more often than no herd-heifers (p=0.048). Concerning social behaviour, the treatment groups tended to differ in submissive behaviour (p=0.062), with mother-heifers being submissive more often than automat-heifers (p=0.023) and permanent suckling-heifers more often than no herd-heifers (p=0.055). The increase in the concentration of faecal cortisol metabolites after the first two days of integration tended to be different between the treatment groups (p=0.088). In our nearest neighbour analysis, one MP-heifer and one M2-heifer could clearly identify their mothers in a herd of 50 cows after 2years of separation (p<0.05, over chance level). This suggests that rearing with contact with the mother in the first twelve weeks, even if very limited, may have an effect on later behaviour and may lead to possibly enhanced social skills in dairy heifers.

Bovine viral diarrhoea virus seroprevalence and vaccination usage in dairy and beef herds in the Republic of Ireland.

BackgroundBovine viral diarrhoea (BVD) is an infectious disease of cattle with a worldwide distribution. Herd-level prevalence varies among European Union (EU) member states, and prevalence information facilitates decision-making and monitoring of progress in control and eradication programmes. The primary objective of the present study was to address significant knowledge gaps regarding herd BVD seroprevalence (based on pooled sera) and control on Irish farms, including vaccine usage.MethodsPreliminary validation of an indirect BVD antibody ELISA test (Svanova, Biotech AB, Uppsala, Sweden) using pooled sera was a novel and important aspect of the present study. Serum pools were constructed from serum samples of known seropositivity and pools were analysed using the same test in laboratory replicates. The output from this indirect ELISA was expressed as a percentage positivity (PP) value. Results were used to guide selection of a proposed cut-off (PCO) PP. This indirect ELISA was applied to randomly constructed within-herd serum pools, in a cross-sectional study of a stratified random sample of 1,171 Irish dairy and beef cow herds in 2009, for which vaccination status was determined by telephone survey. The herd-level prevalence of BVD in Ireland (percentage positive herds) was estimated in non-vaccinating herds, where herds were classified positive when herd pool result exceeded PCO PP. Vaccinated herds were excluded because of the potential impact of vaccination on herd classification status. Comparison of herd-level classification was conducted in a subset of 111 non-vaccinating dairy herds using the same ELISA on bulk milk tank (BMT) samples. Associations between possible risk factors (herd size (quartiles)) and herd-level prevalence were determined using chi-squared analysis.ResultsReceiver Operating Characteristics Analysis of replicate results in the preliminary validation study yielded an optimal cut-off PP (Proposed Cut-off percentage positivity - PCO PP) of 7.58%. This PCO PP gave a relative sensitivity (Se) and specificity (Sp) of 98.57% and 100% respectively, relative to the use of the ELISA on individual sera, and was chosen as the optimal cut-off since it resulted in maximization of the prevalence independent Youden’s Index.The herd-level BVD prevalence in non-vaccinating herds was 98.7% (95% CI - 98.3-99.5%) in the cross-sectional study with no significant difference between dairy and beef herds (98.3% vs 98.8%, respectively, p = 0.595).An agreement of 95.4% was found on Kappa analysis of herd serological classification when bulk milk and serum pool results were compared in non-vaccinating herds. 19.2 percent of farmers used BVDV vaccine; 81% of vaccinated herds were dairy. A significant association was found between seroprevalence (quartiles) and herd size (quartiles) (p < 0.01), though no association was found between herd size (quartiles) and herd-level classification based on PCO (p = 0.548).ConclusionsThe results from this study indicate that the true herd-level seroprevalence to Bovine Virus Diarrhoea (BVD) virus in Ireland is approaching 100%. The results of the present study will assist with national policy development, particularly with respect to the national BVD eradication programme which commenced recently.

Cost-effectiveness of diagnostic strategies to identify Mycobacterium avium subspecies paratuberculosis super-shedder cows in a large dairy herd using antibody enzyme-linked immunosorbent assays, quantitative real-time polymerase chain reaction, and bacterial culture

Diagnostic strategies to detect Mycobacterium avium subsp. paratuberculosis (MAP) super-shedder cows in dairy herds have been minimally studied. The objective of the current study was to compare the cost-effectiveness of strategies for identification of MAP super-shedders on a California dairy herd of 3,577 cows housed in free-stall pens. Eleven strategies that included serum or milk enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qPCR) or culture of environmental samples, pooled or individual cow fecal samples, or combinations thereof were compared. Nineteen super-shedders (0.5%) were identified by qPCR and confirmed by culture as cows shedding ≥ 10,000 colony forming units (CFU)/g feces (median of 30,000 CFU/g feces). A stratified random sample of the study herd based on qPCR results of fecal pools was the most sensitive (74%) strategy and had the highest cost ($5,398/super-shedder). The reference strategy with the lowest cost ($1,230/super-shedder) and sensitivity (47%) included qPCR testing of fecal samples from ELISA-positive lactating (milk) and nonlactating (serum) cows housed in pens with the highest MAP bioburden. The most cost-effective alternative to the reference was to perform qPCR testing of fecal samples from ELISA-positive cows (milk and serum for milking and dry cows, respectively) for a sensitivity of 68% and cost of $2,226/super-shedder. In conclusion, diagnostic strategies varied in their cost-effectiveness depending on the tests, specimen type, and labor costs. Initial qPCR testing of environmental samples from free-stall pens to target cows in pens with the highest MAP bioburden for further testing can improve the cost-effectiveness of strategies for super-shedder identification.

Increase in the occurrence of abortions associated with exposure to the Bluetongue virus serotype 8 in naïve dairy herds

The transplacental transmission capacity demonstrated for Bluetongue virus serotype 8 (BTV-8) in cattle probably is associated with an increased occurrence of abortions. The objectives of this study were to quantify the effect of BTV-8 exposure on the occurrence of abortions in previously naive dairy cow herds under natural infection conditions, and to determine a possible risk period during pregnancy associated with this increase. Two criteria were considered in order to estimate the occurrence of abortion: late return-to-service after a first artificial insemination (AI), and short gestations. A late return-to-service was defined as a return taking place 90 to 200 days after a first AI. These criteria were compared between cows in herds exposed during the 2007 epizootic in France and cows in herds that were not exposed. To determine the risk period during a pregnancy, variations in the occurrence of abortions were quantified according to the stage of the pregnancy during which the exposure took place. Survival analyses were used to estimate the risk of increased occurrence of abortion associated with BTV-8 exposure, adjusted by the principal factors known to influence the risk of abortion. Exposure to the BTV-8 virus under natural conditions in previously naive dairy herds notified after clinical suspicion during the 2007 epizootic was associated with an increase in the occurrence of abortions, regardless of the stage of pregnancy. The at-risk gestation period depended on the criteria used to detect abortions. The mean effect of BTV-8 exposure in the ensemble of detected outbreaks corresponded to an increase of 6.7% in late return-to-service. BTV-8 exposure during the first 3 mo of gestation was associated with a 15% increase in late return-to-service for cows with no return-to-service at 90 days, while this increase was 6% for exposure starting from the third month of gestation (in outbreaks detected in September). BTV-8 exposure from the third month of gestation was associated with a 1.9% increase of short gestations. The effect of exposure was more pronounced for outbreaks detected early in the epizootic compared with those detected later.

Dynamics of Coxiella burnetii antibodies and seroconversion in a dairy cow herd with endemic infection and excreting high numbers of the bacterium in the bulk tank milk

Possible factors related to seropositivity and seroconversion to Coxiella burnetii were examined in a dairy herd with a high Coxiella-seroprevalence and high excretion levels of the bacterium in the bulk tank milk. Antibodies were detected by using a commercial ELISA test in 50.7% of 603 parous cows. The likelihood of C. burnetii seropositivity significantly increased by factors of 1.87 and 1.61 for cows in their first and second terms of pregnancy, respectively, compared to non-pregnant cows. In 478 cows tested twice 12months apart, the seroconversion rate was 5%. The likelihood of C. burnetii-seroconversion was 2.27 times lower in multiparous than in primiparous cows and 6.88 times higher in cows during their first 90days in milk than dry-off cows. Our findings indicated a higher seroprevalence in the first and second terms of pregnancy, and that seroconversion mainly occurred in primiparous cows during their first 90days in milk.

Changes in the level of selected haematological and biochemical parameters in the blood of dairy cows in central-eastern Poland

The study included 4 herds of dairy cows (C, D, E, F) from Central- Eastern Poland. The objective of the study was to evaluate and compare selected haematological and biochemical indicators in the blood of dry and lactating cows from the studied region. Blood was sampled twice from the external jugular vein at two dates: 10-14 days prior to calving and after the first month of lactation. Determination of the RBC (red blood cell) count, as well as haemoglobin concentration (HGB) was made in the samples of whole blood by means of haematological MS 4-5 VET analyser. Glucose and total protein levels, as well as enzyme activities (AST, ALT, ALP and GGT) in the sera were determined with Cormay diagnostic set. Measurements of selected haematological and biochemical indicators indicated a reduced glucose level and increased activity of alkaline phosphatase in lactating cows. A particularly high activity of AST was found in the examined animals.

Study of animal welfare status in dairy cow herds in Hungary

Animal welfare is a hot topic among consumers, producers and researches nowadays. The major welfare problems of dairy cows are mastitis, lameness, and any conditions which lead to impaired reproduction, inability to express normal behaviour, emergency physiological responses or injury. This paper summarizes preliminary results of project taken in 27 Hungarian dairy farms evaluating general animal welfare. The most important areas for improving animals? wellbeing are related to facilities and comfort of resting. Findings include slippery floors, cows struggling laying and standing in cubicles. Other measures include hair loss, hocks, neck rail injuries and number of thin cows (Body Condition Score 1 and 2). Mouldy silage and low quality of other feedstuff was also found. In conclusion, preliminary results confirm strong demand for monitoring farms and discussions with managers and farmers about welfare measures needed to be taken on farms immediately.

Study of animal welfare status in dairy cow herds in Hungary – looking for causes of lameness

In the last 20-30 years, lameness in cattle was found to be third the most influential disease next to mastitis and reproduction disorders. Studies have been established to explore reasons for lameness and prevention. The problem with more robust prevention plans is that knowledge and research evidence is not strong enough to run an effective prevention plan. The aim of the research is to look for reasons of lameness by observing number of cows on 6 farms during 2 lactations. Performance data will be put together to body condition score (BCS) and lameness scores. Other examination is focused on monitoring of 40 farms. This part of the project is more related to extension, collecting and sharing solutions for decreasing lameness. Producers are advised what kind of measures are possible to reduce occurrence of lameness. Effectiveness of those actions will be measured at the end of the study. The first preliminary results show lack in almost all preventive measures needed to be taken in minimizing lameness. Those areas are related to poor facilities, lack of straw, problems with labor and basic management.

Association between &amp;lt;i&amp;gt;IGF1/Tas&amp;lt;/i&amp;gt;I polymorphism and milk traits of Polish Holstein Friesian cows

Abstract. The study was carried out on 658 Polish Holstein Friesian cows. A transversion of A→C in the P1 promoter region of bovine IGF1 gene at position 977 bp upstream from the start codon in exon 1 was identified using ACRS-PCR method. Reverse primer introduced an artificial TasI restriction site. Three genotypes (AA, AC, CC) were found in the analysed herd of dairy cows occurred with a frequency of 0.766, 0.213 and 0.021, respectively. In the presented study, the statistically significant differences between individuals of different IGF1/TasI genotypes were found in milk, fat and protein yield. In the 2nd and 3rd lactations, the cows carrying the CC genotype produced more milk than the AA individuals (P≤0.05). In the case of protein and fat yield, similar tendencies were observed.

Management Factors Influencing Milk Somatic Cell Count and Udder Infection Rate in Smallholder Dairy Cow Herds in Southern Vietnam

Management Factors Influencing Milk Somatic Cell Count and Udder Infection Rate in Smallholder Dairy Cow Herds in Southern Vietnam

Paratuberculosis in breeding stock of red Holstein cows

This paper describes paratuberculosis in an isolated breeding herd of 25 high-yield dairy cows of the Red Holstein breed. The animals were examined clinically and then given the test for ldelayed type hypersensitivity and their blood serum was examined for the presence of specific antibodies against Mycobacterium avium subsp. paratuberculosis (Map). The clinical examination revealed that two cows exhibited symptoms of the disease that indicated an advanced stage of paratuberculosis. The following parameters were examined in the blood of the cows that showed clinical signs of the disease: leukocytes and erythrocytes count, concentrations of total proteins, albumin, iron, sodium, potassium, and activity of creatine kinase. The analysis of the red blood cell count revealed certain digressions that indicated the existence of hypochromic microcytic anaemia. The number of leukocytes was within the physiological values, but the neutrophil-lymphocyte ratio was disrupted and stood at almost 1:1. The results of the biochemical analyses of the blood serum of diseased cows indicated hypoproteinaemia, hypoalbuminaemia, hypoferremia, hyposodiumaemia, hypokalemia, and increased activities of creatine kinase enzymes. A suspect reaction on the site of application of avian tuberculin was determined in two animals. Animals with clinical signs of the disease reacted negative to the test of delayed type hypersensitivity. The presence of specific antibodies against the cause of paratuberculosis was proven in four animals (16%), including two animals with clinical signs of the disease and one that had a suspect reaction on the site of application of avian tuberculin. Furthermore, one animal that died exhibited macroscopic and microscopic changes regarding the intensity and distribution of lesions, the type of cellular infiltrate, and the number of present acidresistent bacteria, and the changes were characterized as diffuse changes of multibacillary type. The cause of bovine paratuberculosis was isolated from the altered organs.

Study of animal welfare status and heat stress measures applied in dairy cow herds in Hungary

The following material focuses on dairy production and climate related issues in Hungary. All the data was gathered during PhDproject: Study of animal welfare status in dairy cow herds in Hungary. Relations between animal welfare and climate changes expressed byincrease in temperature are described. Extremely hot weather creates hard conditions for milking cows when animal welfare is highlycompromised. From the preliminary results obtained one might formulate hypothesis that there are still areas on the farms where immediateactions should be taken to give a relief to cows in hot seasons. There was found significant number of farms with too many animals per onewater trough, dirty water troughs, limited access to water troughs and hazardous surface for cows in critical places where many animals aregathered. Calves with not sufficient amount of water in hot days and other parts of the year were reported. Silage exposure to the sun andmouldy food in a silage clump was also found to be an important factor in monitoring impact of warm weather. Half of the farms lettinganimals to spend time on the pasture or paddock did not provide shade for animals. Low conception rate of first insemination was predictedto be influenced by heat stress, what is proved by lack of heat decreasing measures taken on the farms.

Bacteriological and molecular investigation of B. melitensis in dairy cows in Iran

It is extremely important to investigate the presence of Brucella melitensis as a nonspecific and heterogeneous agent in dairy cows in Iran due to mixed populations of sheep, goats, and cattle. B. melitensis from infected sheep or goat herds may be introduced into the cattle population in this area. Hence, it is essential to obtain epidemiological data on the probable existence of B. melitensis as a different source of the infection or new exotic Brucella phenotypes development in dairy cow herds in Iran. The purpose of this study was to investigate the presence of B. melitensis infection in cows, using both traditional bacteriological tests and polymerase chain reaction (PCR)-based assay. Traditional biotyping and PCR results of 42 Brucella spp. isolates from Tehran and Fars (northern and southern) provinces of Iran identified five (11.9%) and 37 (88.1%) as B. melitensis (four biovar 1 and one biovar 2) and 37 (88.1%) Brucella abortus biovar 3. This study demonstrated that B. melitensis infection in dairy cows of Iran is still present at a low level. However, the Iranian Veterinary Organization should be careful to have dairy cow herds free of B. melitensis infection as a nonspecific agent of brucellosis, since this type of brucellosis may be extended and act as a potential source of severe infection in humans.

Peripheral white blood cell counts throughout pregnancy in non-aborting Neospora caninum-seronegative and seropositive high-producing dairy cows in a Holstein Friesian herd

Pregnancy is characterized by transient changes in the maternal immune system, also evident at peripheral level. The present study analyzes the kinetics and possible factors affecting peripheral white blood cell populations throughout pregnancy in a herd of high-producing dairy cows chronically infected or not with Neospora caninum. We examined 54 pregnant parous cows: 29 Neospora-seronegative and 25 Neospora-seropositive cows. Blood samples were collected on Days 90, 120, 150, 180 and 210 of gestation. General Linear Model (GLM) repeated measures analysis of variance showed that the interaction Neospora-seropositivity × parity significantly affected total leukocyte, neutrophil and monocyte counts with lower levels of total leukocytes, lower neutrophil and higher monocyte counts recorded in primiparous Neospora-seropositive cows. In addition, N. caninum-seropositive cows had significantly increased monocyte counts on Day 180 of gestation compared to seronegative ones. Other factors significantly associated with changes in total and/or differential leukocyte profiles were period of pregnancy, season, twin pregnancy and milk production. In conclusion, a parity-associated effect of chronic N. caninum infection was observed on peripheral blood cell profiles in dairy cattle during gestation.

Use of a stochastic simulation model to assess effects of diagnostic specificity of systems for detecting ovulating cows on herd reproductive performance in year-round calving dairy herds

Many automated systems for detecting ovulating cows in dairy herds require decisions when designing algorithms and selecting cutpoints that require a compromise between diagnostic sensitivity (probability of classifying an ovulating cow as ovulating) and diagnostic specificity [daily probability of not classifying a non-ovulating cow (whether open or pregnant but not yet diagnosed as pregnant) as ovulating]. Because sensitivity must be moderately high, this compromise often results in specificity below 100%. However, little is understood about the effects of reduced specificity on herd reproductive performance. A stochastic model was developed that simulates the reproductive process in a year-round calving dairy herd to assess effects of changes in specificity at various combinations of sensitivity and conception rate (proportion of inseminations resulting in pregnancy) on herd reproductive measures of economic importance. The model included effects of inseminations in pregnant cows on probability of conceptus loss, and variation in the interval from conceptus loss to next ovulation (i.e. the next opportunity to reconceive). Using moderate assumptions of the probability of conceptus loss following insemination in pregnant cows, reductions in specificity from 99.9 to 99.5, 99, 98 and 97%, resulted in decreases in mean 100 day in-calf rate (100DICR; the proportion of cows with a positive pregnancy diagnosis to an insemination on or before 100 days since calving) of 1.2, 3.3, 6.8 and 9.7 percentage points, respectively. These same reductions in Sp resulted in increases in mean 200 day not in-calf rate (200DNICR; the proportion of cows with negative pregnancy diagnosis results to all inseminations on or before 200 days since calving) of 0.5, 1.6, 3.6 and 6 percentage points, and increases in mean number of inseminations per calving (Insems/Calving; the total number of inseminations in the herd divided by the number of cows that recalved) by factors of 1.2, 1.5, 2.1 and 2.8, respectively. The relationship between specificity for detecting ovulating cows and the 100DICR, 200DNICR and Insems/Calving was sensitive to changes in the probability of conceptus loss following inseminations in pregnant cows. However, even with conservative assumptions, specificity still had important effects on 100DICR and 200DNICR. Varying parameters for the interval from conceptus loss to next ovulation had little effect on the relationships between specificity and these measures. These results demonstrate that specificity is an important consideration when designing algorithms and selecting cutpoints in automated systems for detecting ovulating cows. Low specificity not only increases Insems/Calving but also prolongs intervals from calving to the establishment of a sustained pregnancy resulting in substantial reductions in 100DICR and increases in 200DNICR. This model could assist when determining economically optimal combinations of ovulation detection sensitivity and specificity when developing automated systems for selecting ovulating cows in commercial herds.