Disease Occurrence and Risk Factor Analysis in Finnish Ayrshire Cows

Evaluation of some blood liver parameters in cows with subclinical and clinical ketosis

The purpose of the present study was to establish the changes in some blood liver parameters in cows in different physiological conditions with subclinical (SCK) and clinical ketosis (CK). The study was performed on 157 Holstein cows with annual milk yield of 9,000–11,000 L. The animals were divided into 3 groups: I group – pregnant cows (from day 15 to day 0 pre-calving); II group – recently calved (from day 0 to day 15 postpartum) and III group – lactating (from day 30 to 45 postpartum). Blood concentrations of β-hydroxybutyric acid (ВНВА) (mmol/L), glucose (mmol/L), total protein (g/L), albumin (g/L) and total bilirubin (μmol/L) were assayed in all cows. The animals were divided in groups with SCK and CK according to their blood BHBA levels. It was established, that the con-centrations of total bilirubin were statistically significantly elevated vs control groups, while blood glucose, total protein and albumin values decreased, reflecting the impaired liver function in cows with SCK and CK.

Invited review: Incidence, risk factors, and effects of clinical mastitis recurrence in dairy cows

Clinical mastitis (CM) is one of the most frequent and costly diseases in dairy cows. A frustrating aspect of CM is its recurrent nature. This review was conducted to synthesize knowledge on risk of repeated cases of CM, effects of recurrent CM cases, and risk factors for CM recurrence. A systematic review methodology was used to identify articles for this narrative review. Searches were performed to identify relevant scientific literature published after 1989 in English or French from 2 databases (PubMed and CAB Abstracts) and 1 search platform (Web of Science). Fifty-seven manuscripts were selected for qualitative synthesis according to the inclusion criteria. Among the 57 manuscripts selected in this review, a description of CM recurrence, its risk factors, and effects were investigated and reported in 33, 37, and 19 selected manuscripts, respectively. Meta-analysis and meta-regression analyses were used to compute risk ratio comparing risk of CM in cows that already had 1 CM event in the current lactation with risk of CM in healthy cows. For these analyses, 9 manuscripts that reported the total number of lactations followed and the number of lactations with ≤1 and ≤2 CM cases were used. When summarizing results from studies requiring ≥5 d between CM events to consider a CM event as a new case, we observed no significant change in CM susceptibility following a first CM case (risk ratio: 0.99; 95% confidence interval: 0.86-1.14). However, for studies using a more liberal CM recurrence definition (i.e., only 24 h between CM events to consider new CM cases), we observed a 1.54 times greater CM risk (95% confidence interval: 1.20-1.97) for cows that already had 1 CM event in the current lactation compared with healthy cows. The most important risk factors for CM recurrence were parity (i.e., higher risk in older cows), a higher milk production, pathogen species involved in the preceding case, and whether a bacteriological cure was observed following the preceding case. The most important effects of recurrent CM were the milk yield reduction following a recurrent CM case, which was reported to be similar to that of the first CM case, and the increased risk of culling and mortality, which were reported to surpass those of first CM cases.

Predicting hyperketonemia by logistic and linear regression using test-day milk and performance variables in early-lactation Holstein and Jersey cows

Although cowside testing strategies for diagnosing hyperketonemia (HYK) are available, many are labor intensive and costly, and some lack sufficient accuracy. Predicting milk ketone bodies by Fourier transform infrared spectrometry during routine milk sampling may offer a more practical monitoring strategy. The objectives of this study were to (1) develop linear and logistic regression models using all available test-day milk and performance variables for predicting HYK and (2) compare prediction methods (Fourier transform infrared milk ketone bodies, linear regression models, and logistic regression models) to determine which is the most predictive of HYK. Given the data available, a secondary objective was to evaluate differences in test-day milk and performance variables (continuous measurements) between Holsteins and Jerseys and between cows with or without HYK within breed. Blood samples were collected on the same day as milk sampling from 658 Holstein and 468 Jersey cows between 5 and 20 d in milk (DIM). Diagnosis of HYK was at a serum β-hydroxybutyrate (BHB) concentration ≥1.2 mmol/L. Concentrations of milk BHB and acetone were predicted by Fourier transform infrared spectrometry (Foss Analytical, Hillerød, Denmark). Thresholds of milk BHB and acetone were tested for diagnostic accuracy, and logistic models were built from continuous variables to predict HYK in primiparous and multiparous cows within breed. Linear models were constructed from continuous variables for primiparous and multiparous cows within breed that were 5 to 11 DIM or 12 to 20 DIM. Milk ketone body thresholds diagnosed HYK with 64.0 to 92.9% accuracy in Holsteins and 59.1 to 86.6% accuracy in Jerseys. Logistic models predicted HYK with 82.6 to 97.3% accuracy. Internally cross-validated multiple linear regression models diagnosed HYK of Holstein cows with 97.8% accuracy for primiparous and 83.3% accuracy for multiparous cows. Accuracy of Jersey models was 81.3% in primiparous and 83.4% in multiparous cows. These results suggest that predicting serum BHB from continuous test-day milk and performance variables could serve as a valuable diagnostic tool for monitoring HYK in Holstein and Jersey herds.

Evidence of no protection for a recurrent case of pathogen specific clinical mastitis from a previous case

The objective of this study was to determine whether the occurrence of a previous case of pathogen-specific clinical mastitis (CM) protects Holstein dairy cows against a recurrent case. Pathogens studied were Escherichia coli, Staphylococcus aureus, Staphylococcus spp., Streptococcus spp., Klebsiella spp., and Trueperella pyogenes. A total of 40 864 lactations (17,265 primiparous and 23,599 multiparous) from 19 835 cows from 5 large, high milk producing New York State dairy herds were analysed. We estimated the effects of parity, calving diseases, milk yield, current season and number of CM cases in the previous lactation on the risk of a first CM case using generalised linear mixed models with a log link and Poisson error distribution. The aforementioned risk factors and the occurrence of previous cases of pathogen-specific CM within the current lactation were evaluated as risks for second and third cases of pathogen-specific CM. Cows with more CM cases in the previous lactation were at greater risk of pathogen-specific CM in the current lactation. Multiparous cows were at greater risk of a second CM case if they had suffered from a first CM case that was caused by the same pathogen as the second case. In contrast, a second CM case generally put cows at greater risk of a third case, irrespective of whether the third case was caused by the same or a different pathogen. Our results showed that a previous case of pathogen specific CM does not generally protect against a recurrent case.

Costs of clinical mastitis with special reference to premature culling

Bovine mastitis is an economic and a welfare problem on dairy farms. The objective of this study was to estimate the costs of clinical mastitis (CM), having a special focus on the cost variation related to culling decisions. A dynamic optimization model was developed to determine an optimal replacement time of a mastitic cow and to estimate the costs of CM, taking into account the risk of premature culling and the uncertainty in CM prevalence. Six lactations were analyzed at monthly periods for Ayrshire and Holstein-Friesian breeds. The estimates reflect Finnish production conditions where mastitis is treated only by veterinarians. Biological parameters of the model were adapted from the literature and the Finnish dairy herd health recording system. Field data were used to produce the risk parameters of culling due to mastitis on commercial dairy farms. The model recommended treating the cows with CM and keeping them in most cases until their fifth lactation. A cheaper (-20%) heifer transferred the optimum to the previous lactation and a more expensive (+20%) heifer to the following lactation. Conditional on optimal replacements, the average cost of CM of an Ayrshire (Holstein-Friesian costs in parentheses) cow was €485 (€458), varying from €209 (€112) to €1,006 (€946). The costs were at the highest when the occurrence of CM was at a top yield phase. In the scenario where the risk of culling due to mastitis was included in the model, the average cost of CM was €596 (€623). Disposing of a young cow at the end of her first lactation month caused the highest costs. The costs converted to figures per cow-year were €121 (€147) with optimal cullings and €155 (€191) in the current Finnish conditions. Thus, the increase in the costs of CM due to premature cullings was 28% (30%.) The main cost sources were long-term production losses regardless of the culling decisions. Premature culling formed 20% (23%) of the total costs. To decrease the costs of CM, more emphasis should be given to hidden costs, especially the high cost of premature culling should be underlined.

Milk yield and somatic cell count during the following lactation after selective treatment of cows at dry-off

Selective dry cow therapy (SDCT) has received increasing attention in recent years owing to global concerns over agricultural use of antimicrobial drugs and development of antimicrobial resistance. The objective of this study was to evaluate the effect of SDCT on milk yield and somatic cell count (SCC) in dairy herds in the USA. Cows in four Ohio dairy herds were categorized into two groups (low-SCC and high-SCC) at dry-off based on their SCC and clinical mastitis (CM) history during the lactation preceding the dry-off. Low-SCC cows were randomly assigned to receive or not to receive intramammary antibiotics at dry-off. Milk yield and SCC of these cows during the following lactation were compared using linear mixed effects models, adjusting for parity, calving season, stage of lactation, previous lactation milk yield and herd. Milk yield of untreated and treated low-SCC cows at dry-off did not differ significantly during the following lactation. Overall, treated low-SCC cows had 16% lower SCC (approximately 35 000 cells/ml, P=0·0267) than the untreated cows during the following lactation; however, the effect was variable in different herds. Moreover the impact of treatment, or the lack thereof, on milk yield varied considerably between herds. The results suggested that in some herds treating all cows at dry-off may be beneficial while in other herds leaving healthy cows without antibiotic dry cow treatment has no negative impact on milk yield or milk quality (SCC), and in fact, may be beneficial. Further studies are needed to identify characteristics of herds where treating all cows routinely at dry-off may be needed for maintaining good udder health and where switching to selective treatment of cows at dry-off would be the optimal approach to achieve best results.

Effect of reproductive disorders and parity on repeat breeder status and culling of dairy cows in Quebec

This study quantified the effect of peripartum reproductive disorders and parity on repeat breeder status and involuntary culling of dairy cows. Reproductive data of 418 383 lactations were taken from a computerized databank of health records for dairy cows. A logistic regression model was used with dystocia, retained placenta (RP), metritis complex, and parity as fixed effect risk factors and herd entered as the random effect. Of the peripartum problems studied, dystocia had the greatest effect on future fertility. Dystocia increased the odds of a cow being a repeat breeder by 44% [odds ratio (OR): 1.44; confidence interval (CI): 1.37 to 1.51]. Compared to first-parity cows, cows in second, third, and fourth parities had significantly higher odds of being a repeat breeder: 18% (OR: 1.18; CI: 1.16 to 1.20); 24% (OR: 1.24; CI: 1.21 to 1.26); and 42% (OR: 1.42; CI: 1.39 to 1.45), respectively. The odds for second-, third-, or fourth-parity repeat breeders being culled were 24% (OR: 1.24; CI: 1.20 to 1.28); 39% (OR: 1.39; CI: 1.35 to 1.43); and 67% (OR: 1.67; CI: 1.62 to 1.71) respectively, while peripartum reproductive problems had less of an effect.

Using dairy herd improvement records and clinical mastitis history to identify subclinical mastitis infections at dry-off

Interest in selective dry cow therapy (SDCT) has been increasing owing to concerns over development of antimicrobial resistance. Implementation of SDCT, however, requires a quick and cost-effective on-farm method for identifying cows for treatment and cows that can be left without treatment. The objective of the present study was to evaluate the use of clinical mastitis (CM) history and somatic cell counts (SCC) from monthly Dairy Herd Improvement (DHI) records in identification of infected and uninfected cows at dry-off. A total of 647 Holstein cows were classified as uninfected or infected at dry-off based on CM history and varying number of monthly SCC records (with three different SCC cut-offs). Cows were considered uninfected based on the following criteria: (1) SCC <100 000 cells/ml and no CM during the lactation; (2) SCC <200 000 cells/ml and no CM during the lactation; (3) as criterion two, but additionally a cow was also considered uninfected if it experienced a case of CM during the first 3 months of the lactation and the SCC was <100 000 cells/ml for the rest of the lactation; (4) SCC <300 000 cells/ml and no CM during the lactation; otherwise they were considered infected. Infected and uninfected cows at dry-off were most efficiently identified using three months' SCC records with a threshold of 200 000 cells/ml for cows without CM during the lactation and a threshold of 100 000 cells/ml during the rest of lactation for cows with CM during the first 90 days in milk. Moreover, this criterion also most efficiently identified cows infected with major pathogens only at dry-off. The success of the criteria used for identifying infected and uninfected cows will, however, depend on herd characteristics, such as prevalence of infection and type of pathogens present in the herd.

Results and Evaluation of Thirty Years of Health Recordings in the Norwegian Dairy Cattle Population

The results are based on the Norwegian Cattle Health Recording System, which has been in place for the entire country since 1975. The dairy breeds in Norway consist of 94% Norwegian Red and 4% crossbreeds with Norwegian Red. No other breed consists of more than 0.5% of the total population. During the past 30 yr, there have been 11,563,692 dairy cows within the recording system, corresponding to 8,633,532 cow-years and 8,632,516 calvings. This population consisted of 3,038,675 first-calving cows. Altogether, 8,435,704 different diagnoses were recorded from 4,444,485 different cows each year. The general trend for all recordings was an increase in the incidence rate of all cases from 0.74 per 365 d at risk (cow-year) in 1976 to 1.36 in 1990, and then a decrease to 0.62 in 2002. The corresponding figures for cows treated per cow-year were 0.44 up to a maximum of 0.82, and then a decrease to 0.46 per cow-year in 2002. The most common diseases were acute (severe to moderate) clinical mastitis, chronic (mild) clinical mastitis, ketosis, milk fever, teat injuries, retained placenta, silent heat or anestrous, indigestion, cystic ovaries, and metritis. Clinical mastitis increased from 0.15 cows treated per cow-year in 1975 to 0.44 in 1994, and then decreased to 0.23 in 2002. Ketosis began at 0.10 in 1975, increased to 0.24 in 1985, and then decreased to 0.05 in 2005. For several of the most common diseases, there was a reduction of more than 50% from the 1990s to the years after 2000. Validation processes confirmed that this fluctuation reflected the general trend in the population. The disease recording system also reflected the known outbreaks of bovine respiratory syncytial virus during 1976, 1989 to 1990, and 1995. A marked increase in malformation diagnoses could be seen in 1986 and in 1989 and 1990. These could be related to the Chernobyl nuclear power plant accident in April 1986. The diagnosis that showed the most stability throughout these 30 yr was retained placenta. The 3 main reasons for the large fluctuation for many of the diseases could be the following: a breeding effect, an effect of preventive work, and an effect of changing the therapeutic attitude. Many of the actions taken to bring about improvements would not have been possible without a functioning and practical recording system. Our experience is that an organ-related diagnosis system with up to 60 or 70 different diagnoses will meet the needs of the dairy industry.

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%.

Incidence and economics of clinical mastitis in five Holstein herds in the Czech Republic

Data on clinical mastitis (CM) collected between 1996 and 2003 on five Holstein dairy farms in the Czech Republic were analyzed. Lactational incidences of CM, averaged across farms and calculated only from cows with complete lactations, were 0.35, 0.45 and 0.57 for the first, second and third plus subsequent lactations, respectively. The mean numbers of CM cases per cow and lactation were 0.63, 0.94 and 1.22, and the incidence of CM cases per cow-year at risk were 0.68, 1.00 and 1.27 for the first, second and third plus subsequent lactations, respectively. Longitudinal analysis of CM prevalence based on daily records showed the highest proportion of infected cows in the first 10 days of lactation. The within-farm incidence of CM cases per cow per year, averaged over lactations, ranged from 0.53 to 1.56 with a mean value of 0.94 in the whole data set. Direct financial losses from CM per cow per year within farm ranged from 43.63 to 84.84 euros. They included losses from discarded milk, cost for drugs, veterinary service, herdsman's time, cost for an extra milking machine and cost for antibiotic drying of cows. The economic value of CM incidence (change in direct losses per cow per year when increasing CM incidence by one case above the average value) ranged from 58.3 to 80.1 euros per CM case per cow per year with the mean value of 62.6 euros per CM case per cow per year in the total data set. Daily prevalence rate of CM was shown to be the best among various indicators of CM susceptibility, because it accounted for the censored character of the data and for repeated cases of CM within lactations. In order to reduce the incidence of clinical mastitis for dairy cattle in the Czech Republic, we recommend that it should be included as a goal in the breeding program.

The relationship between herd level disease incidence and a return over feed index in Ontario dairy herds

The objective of the current research was to examine the association of herd level disease incidence with the return over feed (ROF) (milk income minus feed cost) herd profit index offered through Canwest Dairy Herd Improvement. The lactational incidence risks (LIR) for displaced abomasum, retained placenta, clinical mastitis, milk fever, clinical ketosis, and lameness submitted by producers (n = 48) were similar to previous reports. However, there was no negative association of clinical disease LIR's with ROE Subclinical ketosis and subclinical mastitis cumulative incidence were determined during the early postpartum period by using a cow-side test for betahydroxybutyrate in milk and the California Mastitis Test, respectively. Subclinical mastitis was not associated with ROE However, a unit increase in the cumulative incidence of subclinical ketosis was associated with a decrease of dollars 0.015/cow/day in the ROE The results highlight the economic significance that subclinical ketosis may have in Ontario dairy herds.

Aetiology and pathogenesis of cystic ovarian follicles in dairy cattle: a review

Cystic ovarian follicles (COF) are an important ovarian dysfunction and a major cause of reproductive failure in dairy cattle. Due to the complexity of the disorder and the heterogeneity of the clinical signs, a clear definition is lacking. A follicle becomes cystic when it fails to ovulate and persists on the ovary. Despite an abundance of literature on the subject, the exact pathogenesis of COF is unclear. It is generally accepted that disruption of the hypothalamo-pituitary-gonadal axis, by endogenous and/or exogenous factors, causes cyst formation. Secretion of GnRH/LH from the hypothalamus-pituitary is aberrant, which is attributed to insensitivity of the hypothalamus-pituitary to the positive feedback effect of oestrogens. In addition, several factors can influence GnRH/LH release at the hypothalamo-pituitary level. At the ovarian level, cellular and molecular changes in the growing follicle may contribute to anovulation and cyst formation, but studying follicular changes prior to cyst formation remains extremely difficult. Differences in receptor expression between COF and dominant follicles may be an indication of the pathways involved in cyst formation. The genotypic and phenotypic link of COF with milk yield may be attributed to negative energy balance and the associated metabolic and hormonal adaptations. Altered metabolite and hormone concentrations may influence follicle growth and cyst development, both at the level of the hypothalamus-pituitary and the ovarian level.

A stochastic model simulating pathogen-specific mastitis control in a dairy herd

The objective of this study was to develop a model simulating mastitis control in dairy herds and to investigate how sensitive the model is when varying the effect parameters according to the uncertainty. The model simulates 9 pathogen-specific mastitis types, each of which can be subclinical or clinical. The clinical cases can be 1 of 4 severities defined according to the effect of the mastitis case: mild, moderate, severe, and permanent effect. The risk factors include lactation stage, parity, yield level, previous diseases, season, and contagious spread of the infection from herd mates. Occurrence of mastitis is modeled to have direct effects on feed intake, body weight, milk yield, somatic cell count in the milk, subsequent mastitis cases within the cow and in herd mates, voluntary and involuntary culling, mortality, and milk withdrawal. Thirty-five scenarios were simulated to study model behavior and model sensitivity. The consequences per cow/yr of mastitis in the default simulated herd included 0.42 clinical mastitis occurrences, 0.56 subclinical mastitis occurrences, loss of 385-kg milk yield, a 1.3% reduced feed intake, 61-kg milk withdrawal and 146 in reduced economic net return. Based on scenarios demonstrating model behavior and sensitivity analysis, the model appears to produce valid consequences of mastitis control strategies. Representation of the effect of subclinical mastitis and of variation in mastitis severity was concluded in this study to be important when modeling mastitis economics in a dairy herd. The model offers the opportunity to study the long-term herd specific effects of a wide range of control strategies against mastitis.

How to Improve Reproductive Efficacy from Now in Japan? Find out the Factors of Late Lactation to Predict Postpartum Reproductive Diseases

Reproductive efficiency and performance in dairy cattle has been declining over the last 20 years in Japan. Recently, this has resulted in serious problems in dairy herds. There have been changes in the animals themselves and in the animal's environment, e.g. the genetic potential for milk yield has improved, the herd size of dairy farms has been expanding, the housing system of dairy cattle has been changing from tie stall to free stall, and total mixed ratio (TMR) feeding systems have become widespread. It is not clear whether the animals have adapted adequately to these environmental changes. Up till now, reproductive management has been undertaken by monitoring animal performance and/or hormonal treatments, and this has resulted in acceptable reproductive performance. However, conception and pregnancy rates have continued to decline, and the calving to calving interval has continued to extend. Consequently, the average parity and the average age at culling in dairy cattle have been declining. The most common causes of culling in dairy cattle are reproductive disorders in Japan. Therefore, in future, prevention of reproductive disorders will be required for both reproductive efficiency and animal welfare. During late pregnancy and the transition from the pregnant, non-lactating state to the non-pregnant, lactating state, dramatic changes are occurring in the dam including an increase in the fetal-placental mass and calving. Thus, the demand for energy, protein and minerals by the conceptus increases, the space within the abdominal cavity and the rumen capacity decreases due to the increased volume of the conceptus, the local immunological relationship between the fetal and maternal placenta dramatically changes, and physiological homeostasis is activated to adapt to these changes. If cattle can't maintain homeostasis before calving, the incidence of reproductive diseases will be greatly increased. We have been examining reproductive, nutritional and immunological factors to predict the occurrence of reproductive disorders as early as possible and to develop strategies to prevent them. It is unlikely that all dairy farms in Japan will be able to improve reproductive performance with general advice, due to the wide variation in feeding systems and management in Japan. Therefore, specific advice needs to be tailored to each herd, based on management systems employed within each herd. We have proposed that it is important to identify common risk factors across herds, to use these factors as an index for disease control and reproductive management and finally to demonstrate the relationship between these factors and fundamental improvement of the reproductive efficiency. We propose this approach with the aim of providing a breakthrough in improving reproductive performance in dairy cattle in Japan. The focus of this review will be that such an approach is important for improvement of the reproductive efficiency in Japanese dairy cows.

Predicting Risk of Ketosis in Dairy Cows Using In-Line Measurements of β-Hydroxybutyrate: A Biological Model

Automated monitoring of individual cows to determine health status is a potentially valuable management tool, especially in large dairy herds. Herein is described the rationale, structure, and functionality of a biological model to predict risk of ketosis in individual cows using in-line measurements of the ketone body beta-hydroxybutyrate (BHBA) in milk. The model also uses acceleration in milk yield, body fatness at calving, diseases in current lactation, and incidences of ketosis in earlier lactations as additional risk factors for ketosis. However, the model is designed to function merely on the basis of milk BHBA in the absence of other data. Values of milk BHBA are smoothed using a state space model before these are used in calculations in the biological part of the model. The model is designed to be updated each time a new BHBA measurement or a disease occurrence is available and then uses previous and current data. Outputs of the model are the risk of ketosis (value between 0 and 1, where 0 = no risk and 1 = clinical ketosis) and how many days until the next milk sample should be taken and analyzed for BHBA. At higher risks for ketosis, more frequent milk sampling is the recommended output. Test examples from cows for which BHBA has been measured extensively were used to show the functionality of the model. The model performed equally well when reductions in sampling frequency were applied, and it was also relatively robust to the addition of up to +/- 2 residual SD of random noise in the BHBA values. This model has the potential to provide the basis for a useful disease monitoring and management tool. However, thorough validation awaits a much larger dataset and testing of the model under a variety of on-farm situations.

Comparison of the disease incidences of Finnish Ayrshire and Finnish Black and White dairy cows

Finnish Ayrshire and Finnish Black and White cows were compared regarding the incidences of early and late mastitis, parturient paresis, ketosis, ovarian disorders, metritis and the risk of having a test-day somatic-cell count >200,000 cells ml(-1) at any of the first three monthly test days in lactation. In a retrospective cohort study 101,793 cows from 5844 tie stalls and 11,811 cows from 437 loose-housing systems from all over Finland were followed from calving in 2000 until the end of lactation. The observed incidences of those cows were then analysed using generalised linear mixed models. Finnish Black and White cows had higher incidences of all diseases except ovarian disorders. Although the differences were statistically significant in all models except metritis and early mastitis in loose-housing systems, they were, in our view, only important on the national level (for the breeding organisations), and of little importance for the farmers.

Optimizing replacement of dairy cows: modeling the effects of diseases

We modified an existing dairy management decision model by including economically important dairy cattle diseases, and illustrated how their inclusion changed culling recommendations. Nine common diseases having treatment and veterinary costs, and affecting milk yield, fertility and survival, were considered important in the culling decision process. A sequence of stages was established during which diseases were considered significant: mastitis and lameness, any time during lactation; dystocia, milk fever and retained placenta, 0-4 days of lactation; displaced abomasum, 5-30 days; ketosis and metritis, 5-60 days; and cystic ovaries, 61-120 days. Some diseases were risk factors for others. Baseline incidences and disease effects were obtained from the literature. The effects of various disease combinations on milk yield, fertility, survival and economics were estimated. Adding diseases into the model did not increase voluntary or total culling rate. However, diseased animals were recommended for culling much more than healthy cows, regardless of parity or production level. Cows in the highest production level were not recommended for culling even if they contracted a disease. The annuity per cow decreased and herdlife increased when diseases were in the model. Higher replacement cost also increased herdlife and decreased when diseases were in the model. Higher replacement cost also increased herdlife and decreased the annuity and voluntary culling rate.

A stochastic model simulating milk fever in a dairy herd

A simulation model was developed to evaluate the long-term effect of control strategies against milk fever (MF); here, we present the base model and sensitivity analyses. The representation of the within-herd dynamics was based on the existing SimHerd II model. Because of the relationships between MF and other diseases, the new model (called "SimHerd III") includes diseases common in a dairy herd. The cow level risk factors modelled were: base risk in the herd, parity, milk-yield potential, lactational disease recurrence, disease interrelationships, body condition and season. The diseases include clinical cases of MF, dystocia, downer-cow syndrome, retained placenta, metritis, displaced abomasum, ketosis and mastitis. The effects of diseases were represented by daily milk yield, daily body weight, daily feed intake, risk of stillbirth, conception probability, decision on culling, death and immediate removal. Simulated technical results showed that the herd effects of reduced risk of MF differed according to the reproductive efficiency in the herd. These interactions between reproduction efficiency and the effect of reduced base risk of MF were related to differences in how the simulated herds reacted to the reduction in replacements caused by MF. In the sensitivity analysis, eight potential key parameters were changed to their lowest and highest expected values retrieved from the literature. When measuring the sensitivity on milk production in the herd (as the economically most important technical effect), the model seemed most sensitive to the uncertainty of effect of MF on death risk and MF-recurrence risk.

Investigation of mastitis problems on farms

The production of high-quality milk is a high-priority issue for dairy farmers and milk processors. The investigation of mastitis problems on dairy farms is an area of increasing demand and is an ideal way for veterinary practitioners to increase involvement in production medicine programs. Goals for the amount of clinical and subclinical mastitis should be predefined on dairy farms, and a herd investigation initiated when needed. The use of a structured approach to mastitis problems can identify risk factors for infection, result in rapid resolution of mastitis problems, and hasten the application of appropriate preventive practices.

Risk factors for metritis in Danish dairy cows

A retrospective longitudinal study of metritis was conducted in Denmark on data collected during 1993-1994. Data on herd size, breed, parity, and treatment of disease were obtained from the Danish Cattle Database. Management and production-facility data were collected using a questionnaire, conducted as a telephone interview in 1994. The study included 2144 herds from three regions in Denmark (102,060 cows). Herd-level variables included were: herd size, housing, flooring, grazing, calving measures, and calving supervision. Cow-level variables were: parity, breed, calving season and whether the cow had been treated by a veterinarian for dystocia or the diseases: retained placenta, reproductive disease, ketosis, milk fever, or dry cow mastitis. Marginal multivariable logistic-regression analyses were performed. The cow with highest odds of metritis was a first or greater than or equal to third parity cow, of large breed, that calved during November-April, in a zero-grazing herd. The cow had been treated for dystocia, retained placenta, and at least one other reproductive disease, but not for ketosis.

Comparison of the disease incidences of dairy cows kept in cold and warm loose-housing systems

Finland's cold loose-housing systems for dairy cows were compared with the more traditional warm loose-housing systems regarding the incidences of ketosis, mastitis, metritis, parturient paresis and ovarian disorders. Approximately 5000 calvings on 210 farms during the years 1996 and 1997 were modelled, using multilevel Poisson regression and multilevel logistic-regression in a retrospective observational cohort study. Cows in a cold loose-housing system were at lower odds for developing late mastitis (15-305 days in milk), and metritis (Friesian breed); of the same odds for ketosis and early mastitis (0-14 days in milk); but at higher odds for developing parturient paresis and metritis (Ayrshire breed). The estimated odds ratio for ovarian disorders depended on the definition for exposure. Although one of the differences was statistically significant and many of them of veterinary interest, none of them appear to be substantial for the economy of a median-sized dairy farm in Finland.

The relationship between milk yield and the incidence of some diseases in dairy cows

Logistic regression models were used to examine the relationship between milk yield and incidence of certain disorders. Lactations (n = 2197) of 1074 Holstein-Friesian cows from 10 dairies (25 to 146 cows per dairy) in Lower Saxony were studied. The 305-d yield from the previous and current lactations served as the standards for milk yield. Eight disorder complexes were considered: retained placenta, metritis, ovarian cysts, mastitis, claw diseases, milk fever, ketosis, and displaced abomasum. Each disorder complex was modeled separately. In addition to milk yield, the influences of the lactation number, the calving season and the other disorder complexes were examined with the "herd" factor taken into account. A correlation between retained placenta, mastitis, and milk fever to milk yield during the previous lactation was found to be probable and for ketosis and displaced abomasum such a correlation was found to be possible. A connection to the yield in the current lactation was shown for ovarian cysts, claw diseases, and milk fever. No relationship to milk yield existed for metritis. An influence of the lactation number was also demonstrated in various models. Single models allowed a demonstration of the influences of both milk yield and lactation number. Limitations of the model types are discussed.

Short communication: associations between blood calcium status at calving and milk yield in dairy cows

The purpose of the present study was to estimate the effect of total blood plasma calcium (TBPCC) concentration at calving on milk yield in dairy cows. Data originated from 153 dairy cows in 27 herds from a single veterinary practice. For each cow, data included calcium concentration in a blood sample taken within 12 h postpartum, monthly test-day milk yield until 300 d in milk, calving date, parity, breed, and herd. The TBPCC ranged from 0.69 to 2.73 mmol/L, with a mean value of 1.80 mmol/L. The statistical analysis adjusted for the fixed effects of parity and lactation stage, random effects of herd and cow, and the correlation between repeated measures of test-day milk yield. The results showed that TBPCC at calving was not significantly related to fat- and protein-corrected milk yield at any lactation period. The present study indicates that hypocalcemia (low TBPCC) at calving is not an important risk factor for decreased milk yield.

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 herd's 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.

A stochastic model simulating the feeding-health-production complex in a dairy herd

A dynamic, stochastic, and mechanistic Monte Carlo model, simulating a dairy herd with focus on the feeding-health-production complex is presented. By specifying biological parameters at cow level and a management strategy at herd level, the model can simulate the technical and economic consequences of scenarios at herd level. The representation of the feeding-health-production complex is aimed to be sufficiently detailed, to include relationships likely to cause significant herd effects, and to be sufficiently simple to enable a feasible parameterization of the model and interpretation of the results from the model. Consequently, diseases are defined as four disease types: two metabolic disease types, an udder disease type, and a reproductive disease type. Risk factors for the diseases were defined as parity, yield capacity, disease recurrence, disease interrelationships, lactation stage, and season. Direct effects of the diseases were defined according to milk yield, feed intake, feed utilization, conception, culling, involuntary removal, and death. Scenarios differing in base risks of milk fever and ketosis, heat detection rate, and culling strategy were simulated for describing the model behavior. Annual milk yield per cow was decreased by increased risk of ketosis and by increased risk of milk fever, even though no direct effect of milk fever on milk yield was modeled at the cow level. The indirect effect from milk fever is a consequence of increased replacement rate (relatively lower milk yield from younger cows). By ignoring the history of milk fever in insemination and replacement decisions, a significantly reduced net income per cow was found in some herds. We concluded that important benefits from using such a herd model are the capability of accounting for herd management factors and the advantage of avoiding to double count the indirect effects from disease, such as increased risk of other diseases, poorer reproduction results, and increased risk of culling and death.

Optimizing replacement decisions for Finnish dairy herds

The purposes of the study were to determine how "an optimal herd" would be structured with respect to its calving pattern, average herdlife and calving interval, and to evaluate how sensitive the optimal solution was to changes in input prices, which reflected the situation in Finland in 1998. The study used Finnish input values in an optimization model developed for dairy cow insemination and replacement decisions. The objective of the optimization model was to maximize the expected net present value from present and replacement cows over a given decision horizon. In the optimal solution, the average net revenues per cow were highest in December and lowest in July, due to seasonal milk pricing. Based on the expected net present value of a replacement heifer over the decision horizon, calving in September was optimal. In the optimal solution, an average calving interval was 363 days and average herdlife after first calving was 48.2 months (i.e., approximately 4 complete lactations). However, there was a marked seasonal variation in the length of a calving interval (it being longest in spring and early summer) that can be explained by the goal of having more cows calving in the fall. This, in turn, was due to seasonal milk pricing and higher production in the fall. In the optimal solution, total replacement percentage was 26, with the highest frequency of voluntary culling occurring at the end of the year. Seasonal patterns in calving and replacement frequencies by calendar month and variation in calving interval length or herdlife did not change meaningfully (< 1%-2% change in the output variables) with changes in calf, carcass or feed prices. When the price of a replacement heifer decreased, average herdlife was shorter and replacement percentage increased. When the price increased, the effect was the opposite.

Optimizing breeding decisions for Finnish dairy herds

The purpose of this study was to determine the effect of reproductive performance on profitability and optimal breeding decisions for Finnish dairy herds. We used a dynamic programming model to optimize dairy cow insemination and replacement decisions. This optimization model maximizes the expected net revenues from a given cow and her replacements over a decision horizon. Input values and prices reflecting the situation in 1998 in Finland were used in the study. Reproductive performance was reflected in the model by overall pregnancy rate, which was a function of heat detection and conception rate. Seasonality was included in conception rate. The base run had a pregnancy rate of 0.49 (both heat detection and conception rate of 0.7). Different scenarios were modeled by changing levels of conception rate, heat detection, and seasonality in fertility. Reproductive performance had a considerable impact on profitability of a herd; good heat detection and conception rates provided an opportunity for management control. When heat detection rate decreased from 0.7 to 0.5, and everything else was held constant, net revenues decreased approximately 2.6%. If the conception rate also decreased to 0.5 (resulting in a pregnancy rate of 0.25), net revenues were approximately 5% lower than with a pregnancy rate of 0.49. With lower fertility, replacement percentage was higher and the financial losses were mainly from higher replacement costs. Under Finnish conditions, it is not optimal to start breeding cows calving in spring and early summer immediately after the voluntary waiting period. Instead, it is preferable to allow the calving interval to lengthen for these cows so that their next calving is in the fall. However, cows calving in the fall should be bred immediately after the voluntary waiting period. Across all scenarios, optimal solutions predicted most calvings should occur in fall and the most profitable time to bring a replacement heifer into a herd was in the fall. It was economically justifiable to keep breeding high producing cows longer than low producing cows.

Mastitis in the first year postpartum

BACKGROUND

Limited information is available about the frequency and risk factors for lactation mastitis. The purpose of this study was to investigate frequency, risk factors, and outcome for lactation mastitis.

METHODS

We analyzed data from a cohort study of 350 mothers with healthy term infants, who were followed up for one year postpartum.

RESULTS

Eighty-three women (23.7% of the sample) reported one or more episodes of mastitis symptoms, and 61 (17.4%) women reported symptoms including fever. Fifty-six women (16%) received one or more courses of antibiotics for mastitis. Thirty women (8.5%) of the total cohort had recurrent episodes of mastitis symptoms. A total of 123 episodes of mastitis symptoms were reported. No cases of abscess were reported. Using multiple logistic regression, the adjusted risk ratio for mastitis symptoms associated with sore nipples in the first month was 2.07 (95% CI = 1.17, 3.66). A reduced risk of mastitis was associated with maternal smoking during pregnancy, with supplementation with water in the first month, and with the use of a pacifier on a daily basis within the first month. A history of mastitis symptoms was associated with a longer overall duration of breastfeeding.

CONCLUSIONS

Our results suggest that mastitis may be a marker for an ample milk supply. Mothers presenting with mastitis can be reassured that the outlook for continued successful lactation is good. Further research is needed to investigate the reasons for recurrence of mastitis and the etiology of episodes occurring late in lactation.

Culling of dairy cows. Part II. Effects of diseases and reproductive performance on culling in Finnish Ayrshire cows

The effects of 15 diseases and reproductive performance on culling were studied in 39727 Finnish Ayrshire cows that calved in 1993 and were followed until culling or next calving. Survival analysis, using the Cox proportional hazards model, was performed with diseases and pregnancy status as time-dependent covariates. Parity, calving season and herd were included as covariates in every model. The effect of the number of inseminations was also studied. The farmer's knowledge of the cow's pregnancy status had a significant effect on culling. It varied according to the stage of lactation a cow was in; the earlier the farmer knew a cow was pregnant, the smaller was the risk of culling. If a cow had not been inseminated at all, her risk of culling was 10 times higher than if she was inseminated once. If a cow was inseminated more than once, she had a slightly lower risk of being culled than a cow inseminated only once. The effect of parity decreased when pregnancy status and number of inseminations were added to the model, indicating that part of the parity effect was accounted for by reproductive performance. Including diseases in the model with pregnancy status and the number of inseminations did not change the effects of reproductive performance on culling. Mastitis, teat injuries and lameness had the greatest effect on culling (whether adjusted for reproductive performance or not), increasing the risk of culling, followed by anestrus, ovarian cysts and milk fever. In general, the effects of diseases decreased when reproductive performance was also accounted for in the model. When pregnancy status was included in the model, the effects of anestrus and ovarian cysts became slightly more protective, but when the number of inseminations was also considered, they became non-significant at the beginning of lactation and they increased the risk of culling at the end of lactation. Sensitivity analysis, which was run to evaluate the effects of our censoring mechanism on the results, indicated that the censoring times (i.e., the time of next calving) were not fully independent of the event (culling) times; the effects of the diseases and pregnancy status at the very end of the lactation changed slightly from the original model.

Culling of dairy cows. Part III. Effects of diseases, pregnancy status and milk yield on culling in Finnish Ayrshire cows

The effects of 15 diseases, pregnancy status and milk yield on culling were studied in 39727 Finnish Ayrshire cows that calved in 1993 and were followed until culling or next calving. Survival analysis, using the Cox proportional hazards model, was performed with diseases, pregnancy status and milk yield as time-dependent covariates. Effects of parity, calving season and herd were also accounted for. Pregnancy status was the single most influential factor affecting culling decisions, followed by milk yield. Several diseases also had a significant effect on culling, the most influential ones being mastitis, lameness, teat injuries, and milk fever. The effects of all of these factors varied according to the stage of lactation. Milk yield had a significant effect on culling decisions, depending on the stage of lactation. At the beginning of lactation, milk production did not have any effect on culling decisions, but later on, the highest producers were at the lowest risk of being culled and the lowest producers had the highest risk. Adjusting for milk yield modified the effects of parity, most diseases and also pregnancy status on culling. Effects of parity increased after including milk yield in the model, indicating that milk yield and parity are interrelated in their effects on culling. The effects of pregnancy status also increased towards the end of lactation when milk yield was accounted for in the model. The effects of mastitis, teat injuries and lameness decreased after adjusting for milk production. These diseases lower milk yield and thus, part of their effect on culling was mediated through milk production. The effects of anestrus and ovarian cysts were mainly modified by pregnancy status, but not by milk yield. The effects of milk fever on culling increased at the beginning of lactation after including milk yield in the model. This suggests that even though cows with milk fever tend to be higher producers, it is the disease as such that triggers the culling decision early in the lactation. The changes in the effects of other diseases after adjusting for milk yield varied, depending on the disease and the stage of lactation.

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

The effects of 15 diseases on time until culling were studied in 39,727 Finnish Ayrshire cows that calved during 1993 and were followed until the next calving or culling. The diseases studied were: dystocia, milk fever, retained placenta, displacement of the abomasum, metritis, non-parturient paresis, ketosis, rumen disorders, acute mastitis, hypomagnesemia, lameness, traumatic reticuloperitonitis, anestrus, ovarian cysts, and teat injuries. Survival analysis, using the Cox proportional hazards model, was performed and diseases were modeled as time-dependent covariates. Different stages of lactation when culling can occur were also considered. Parity, calving season and herd were included as covariates in every model. Parity had a significant effect on culling, the risk of culling being four times higher for a cow in her sixth or higher parity than for a first parity cow. The effects of diseases varied according to when the diseases occurred and when culling occurred. Mastitis, teat injuries and lameness had a significant effect on culling throughout the whole lactation. Anestrus and ovarian cysts had a protective effect against culling at the time when they were diagnosed. In general, diseases affected culling decisions mostly at the time of their occurrence. The effect seemed to decrease with time from the diagnosis of the disease. However, milk fever, dystocia and metritis also had a significant effect on culling at the end of the lactation.

Effects of clinical mastitis on milk yield in dairy cows

The effect of clinical mastitis on milk yield was studied in 24,276 Finnish Ayrshire cows that calved in 1993 and were followed for one lactation (i.e., until culling or the next calving). Cows that had only mastitis, but no other diseases, and cows that had no diseases (healthy cows) during the lactation were included in the study. Monthly test day milk yields were treated as repeated measurements within an animal in a mixed model analysis. Mastitis index categories were created to relate the timing of mastitis to the test day milk measures. Statistical models (a separate model for each parity) included fixed effects of calving season, stage of lactation, and mastitis index. An autoregressive correlation structure was used to model the association among the repeated measurements. The effect of mastitis occurring at different periods during the lactation was studied. The daily loss during the first 2 wk after the occurrence of mastitis varied from 1.0 to 2.5 kg, and the total loss over the entire lactation varied from 110 to 552 kg and depended on parity and the time of mastitis occurrence. Regardless of the time of occurrence during the lactation, mastitis had a long-lasting effect on milk yield; cows with mastitis did not reach their premastitis milk yields during the remainder of the lactation after onset of the disease.

Effects of milk fever, ketosis, and lameness on milk yield in dairy cows

The effects of milk fever, ketosis, and lameness were studied using data from 23,416 Finnish Ayrshire cows that calved in 1993 and were followed for one lactation (i.e., until culling or the next calving). Monthly test day milk yields were treated as repeated measurements within a cow in a mixed model analysis. Disease index variables were created to relate the timing of a disease to the measures of test day milk. Statistical models for each parity and disease included fixed effects of calving season, stage of lactation, and disease index. An autoregressive correlation structure was used to model the association among the repeated measurements. The milk yield of cows contracting milk fever was affected for a period of 4 to 6 wk after calving; the loss ranged from 1.1 to 2.9 kg/d, depending on parity and the time elapsed after milk fever diagnosis. Despite the loss, cows with milk fever produced 1.1 to 1.7 kg more milk/d than did healthy cows. Milk yield started to decline 2 to 4 wk before the diagnosis of ketosis and continued to decline for a varying time period after it. The daily milk loss was greatest within the 2 wk after the diagnosis, varying from 3.0 to 5.3 kg/d, depending on parity. Cows in parity 4 or higher were most severely affected by ketosis; the average total loss per cow was 353.4 kg. Lameness also affected milk yield; milk loss of cows diagnosed with foot and leg disorders varied between 1.5 and 2.8 kg/d during the first 2 wk after the diagnosis.

Effects of dystocia, retained placenta, and metritis on milk yield in diary cows

The effects of dystocia, retained placenta, and metritis on milk yield were studied in 37,776 Finnish Ayrshire cows that calved during 1993; cows were studied for one lactation. Monthly test day milk yields were treated as repeated measurements within a cow in a mixed models analysis. Index categories were created to relate the time of disease occurrence to the test dates and to capture the short-term effects of diseases on milk yield. Diseases other than dystocia, retained placenta, or metritis were categorized into two groups: diseases occurring within 42 d after calving or diseases occurring later than that. The statistical models for each parity included calving season, stage of lactation, and disease variables as fixed effects. For parities 2, 3, and 4 or higher, the cows were grouped into four categories based on previous lactation milk yield, and the disease effect was studied separately for each yield level. An autoregressive covariance structure was used to model the association among the repeated measurements. Models with a 305-d yield as the outcome were also run; the diseases were treated as binary covariates in these models. Dystocia, retained placenta, and early metritis significantly affected milk yield, as indicated by monthly test day milk yields. Late metritis was not associated with milk loss. The impact of the diseases differed across parities and also across different levels of milk yield. Using 305-d milk yield as the milk measure, no diseases were associated with reduced milk yield.

Clinical biochemistry, haematology and body weight in piglets

Reference ranges for clinical biochemical parameters commonly investigated in pigs were determined in one- (day 1), 21- and 35-day old piglets. The mean and standard deviation were also estimated for body weight, and haematological and clinical biochemical parameters at these ages. The piglets were divided into 2 investigation groups according to whether they had a haemoglobin concentration < or = 80 g/l ("anaemic group") or > 80 g/l ("normal group") on days 14, 21 and 28. The "anaemic group" was compared to the "normal group" on days 21 and 35. Many of the clinical biochemical parameters varied according to age. Some of the enzymes had high average values and wide reference ranges in piglets, especially on day 1, compared to the reference ranges for sows given in the literature. The reference ranges for some of the metabolic parameters were broader on day 1 than later in the preweaning period. The reference ranges for albumin, total iron-binding capacity and serum iron were, however, lower and more narrow on day 1. On days 21 and 35, relatively high values for phosphorus must be considered "normal" compared to the figures given in the literature for adult pigs. The other minerals seemed to be quite unaffected of age, but some were affected by anaemia. The anaemic piglets had lower average serum iron but higher total iron-binding capacity than the "normal" piglets on days 21 and 35. However, variation between piglets gave wide reference ranges, indicating that these parameters will only have limited usefulness in detecting iron deficiency anaemia in piglets. The electrolytes seemed also to be affected by the existence of anaemia. The body weight and leukocyte counts were significantly lower in the "anaemic group" than the "normal group" on day 35, while the greatest differences in clinical biochemical parameters between the groups were found on day 21, when the piglets in the "anaemic group" were most severely anaemic. Although these piglets suffered from severe iron-deficiency anaemia, only a few clinical biochemical parameters were affected, and the differences between groups were mostly small.