Assessing the repeatability and reproducibility of the Leg Score: a Dutch Claw Health Scoring System for dairy cattle.

The optimal moment for trimming the claws of all dairy cows in a herd was investigated by assessing the external rotation of the hind claws of individual cows relative to the spinal column. This leg score consisted of three independent descriptors: 1 (good/normal), 2 (moderately deviant), and 3 (severely deviant). This study assessed the repeatability and the reproducibility of the leg score system, and the consistency of the advice given subsequently about trimming of the hind claws of all cows in the herd. Repeatability was assessed for 52 cows that were scored twice on the same day by 11 observers; the kappa value ranged from 0.17 to 0.66 (mean: 0.36). The probability of the same result for both assessments ranged from 0.49 to 0.80 (mean: 0.61). Claw trimming was advised if at least 20% of the cows had a leg score of 3. On the basis of the scores, 3 observers consistently advised trimming of the hind claws of all the cows in the herd, and 6 observers consistently advised against the need for trimming in the short term; 2 observers had an inconsistent advice. The reproducibility of the scoring system was assessed in two dairy herds (62 and 50 cows). Eight observers evaluated the leg score of the cows of both herds on the same day. The mean kappa value of the leg score for all pairs of different observers (A-B, A-C etcetera) was 0.24 [-0.08-0.49]. In conclusion, the leg score is not a reliable method for determining the optimal moment for claw trimming in dairy cattle. The reasons for the inconsistent observations require further investigation.

Risk factors for interdigital dermatitis and heel erosion in dairy cows kept in cubicle houses in The Netherlands.

Risk factors concerning both the pasture and housing seasons for interdigital dermatitis and heel-horn erosion (IDHE) were studied in dairy cows in a cross-sectional study in The Netherlands. The study population included 2,326 cows (41 herds) and 2,751 cows (46 herds) for the pasture and housing seasons, respectively. Of these animals, 545 (23%) showed serious lesions of IDHE (stages 2 and 3) at the end of the pasture season and 1,269 (46%) during housing. Logistic regression of the pasture study indicated that increased parity, solid concrete floor, restricted grazing time, and herd trimming at long intervals were associated with an increased odds of IDHE, while dry cows and lactating cows within 30 days after calving as well as cows on a slatted floor with manure scraper, and grassland with mixed type of soil were associated with lower odds. In the housing study, odds of IDHE increased with parity, administering low- or medium-energy roughage, and introduction of dry cows into the lactating herd at >2 weeks before calving. The presence of long cubicles, knee-bumpers installed in cubicles as well as rearing calves and heifers within the dairy cows' accommodation decreased the odds of IDHE.

Risk factors for digital dermatitis in dairy cows kept in cubicle houses in The Netherlands.

The presence of digital dermatitis (DD) in dairy cows has increased considerably over the last 10 years in The Netherlands, resulting in a current prevalence of approximately 30% in cows kept in cubicle houses. Our objective was to evaluate a diversified sample of cow- and herd-related risk factors for DD in dairy cows housed in cubicle houses with different flooring systems. Associations were analysed in random-effects logistic-regression models using 2,134 cows (37 herds) and 2,892 cows (47 herds) in the pasture and housing studies, respectively. At cow-level, the odds of having DD were increased in the case of lower parity and lactation. Important risk factors at herd-level were: restricted grazing time, fast rise in concentrate amount after calving, feeding by-products, herd trimming only at long intervals, and introduction of dry cows into the lactating herd before calving. The odds for DD were lower if cows were housed on a slatted floor with manure scraper and provided long and wide cubicles, and if calves were reared in the dairy cows' accommodation.

Frictional forces required for unrestrained locomotion in dairy cattle.

Most free-stall housing systems in the Netherlands are equipped with slatted or solid concrete floors with manure scrapers. A slipping incident occurs when the required coefficient of friction (RCOF) exceeds the coefficient of friction (COF) at the claw-floor interface. An experiment was conducted to measure ground reaction forces (GRF) of dairy cows (n = 9) performing various locomotory behaviors on a nonslippery rubber-covered concrete floor. The RCOF was determined as the ratio of the horizontal and vertical components of the GRF. It was shown that during straight walking and walking-a-curve, the RCOF reached values up to the COF, whereas for sudden stop-and-start responses, the RCOF reached values beyond the maximum COF that concrete floors can provide. Our results indicate that concrete floors do not provide enough friction to allow natural locomotory behavior and suggest that tractional properties of floors should be main design criteria in the development of better flooring surfaces for cattle.

Development of claw traits and claw lesions in dairy cows kept on different floor systems.

Several claw shape measurements, horn hardness, and horn growth and wear were recorded monthly at 12 dairy farms to investigate the effect of floor type and changes in these traits over time. Herds were either housed on a slatted floor (SL), solid concrete floor (SC), grooved floor (GR), or on a straw yard (SY). Twenty cows per farm were selected and stratified by parity. Information on claw traits was recorded on right lateral hind claws between October 2002 and May 2003. In addition, lesion development of interdigital dermatitis and heel erosion (IDHE) and digital dermatitis (DD) was studied in both rear feet. No differences in claw traits were detected among groups on different floor types, with the exception of claw angle. Claw angles were smallest in cows on SY. Claws of cows on SC were steeper than those on SL and GR. The study provided no evidence that floor-related differences in claw lesions were related to differences in horn growth, wear, and resulting claw shape. Lesions of IDHE developed gradually over time and did not differ among flooring types. Cows in SY had the smallest lesion scores for DD, whereas cows on SL had significantly less DD than cows on SC and GR. Incidence of DD fluctuated over time. Development of different stages of DD was monitored in-depth. Both early and healed stages were rather changeable and often turned into other disease stages. Classical ulcerative lesions (stage M2) persisted for a long time, with 20% of the initially unaffected claws having active lesions of DD within 5 mo. The M2 lesions generally did not cure effectively after claw trimming, and frequent use of footbaths resulted in a poor prognosis for recovery.

The effect of preventive trimming on weight bearing and force balance on the claws of dairy cattle.

Claw disorders and lameness in dairy cattle are an increasing problem of the modern dairy industry. To prevent claw disorders from evolving from the subclinical to the clinical stage, trimming is the management practice most routinely applied. The goal of preventive trimming (Toussaint-Raven method) is to promote natural loading by increasing the weight-bearing contact area of the claws and improving the balance between the medial and lateral claw. The biomechanical effect of preventive claw trimming was investigated with the aid of pressure distribution and ground reaction force recordings of the standing cow sampled simultaneously at 250 Hz. It appeared that preventive trimming of the hind limbs (n = 10) brought the claws slightly more in balance. Before trimming, 80% of the total force is taken up by the lateral claw and 20% by the medial claw. After trimming, this becomes 70 to 30%, respectively. Thereby, a significant increase in the weight-bearing contact area from 27.5 to 40.0 cm2 was achieved, resulting in a significant decrease in average pressure. However, the claws remained subjected to unaltered, high maximum pressures after trimming. The suggestion was made that the main focus of claw trimming should not be force balance; instead, a reduction of local maximum pressures at the contact area should be targeted in such a way that the strongest parts of the claw capsule (i.e., the wall) will be subjected to the highest pressures.

Effects of milk production capacity and metabolic status on HPA function in early postpartum dairy cows.

Increasing milk yields in modern dairy cows cause concern that high yield may impair the cows' health and welfare, for example, via negative effects on metabolic status and hypothalamo-pituitary-adrenocortical (HPA) function. This study aims to investigate whether a high level of milk production, and the associated metabolic status, affects HPA function in dairy cows and changes their adaptive capacity. Additionally, it aims to establish whether possible effects of milk production level only show under challenging conditions. Holstein-Friesian cows, which produced on average 11,443 and 7727 kg of fat and protein-corrected milk (FPCM)/305 d in their previous lactation, were compared. During the dry period, the cows were fed to requirements or overfed. High milk yield and the concomitant large energy deficit were associated with 1) increased pituitary (re)activity, i.e., increased ACTH baseline concentrations and higher ACTH concentrations after corticotropin-releasing hormone (CRH) administration, and 2) decreased adrenocortical reactivity, i.e., lower cortisol responses after ACTH administration. Although significant, the effects of milk production level on HPA function were relatively small. Animals showed seemingly normal hormonal responses to CRH and ACTH administration. Also, cortisol baseline concentrations were unaffected. It seems, therefore, unlikely that the adaptive capacity of the high-producing cows was significantly impaired compared with their low-producing herdmates.

Bacterial growth during the early phase of infection determines the severity of experimental Escherichia coli mastitis in dairy cows.

The aim of this study was to investigate the importance of bacterial growth for the severity of experimental Escherichia coli mastitis, indirectly expressed as the area under the curve of bacterial counts in milk over time. The association of pre-infusion somatic cell count and post-infusion influx of inflammatory cells in milk with severity of infection was also examined. Bacterial growth was studied through culture in milk samples (in vitro) and through monitoring of bacterial counts in milk during the early phase of infection (in vivo) in 36 cows. Individual variation in bacterial counts was more than 2 x 10(2)-fold after 6 h of in vitro incubation, and more than 8 x 10(2)-fold 6 h after intramammary infusion. In vitro growth in milk was not associated with in vivo growth during the early phase of infection, nor with severity of E. coli mastitis. Somatic cell count before experimental E. coli mastitis was negatively associated with in vivo bacterial growth during the early phase of infection (R2 = 0.28), but was not associated with severity of E. coli mastitis (R2 = 0.06). In vivo bacterial growth during the early phase of infection (positive association; R2 = 0.41), together with influx of inflammatory cells in milk, expressed as mean hourly increase of somatic cell count between 6 and 12 h post-infusion (negative association; R2 = 0.11), are major determinants for the severity of experimental E. coli mastitis (R2 = 0.56).

The vertical ground reaction force and the pressure distribution on the claws of dairy cows while walking on a flat substrate.

The pressure distribution under the bovine claw while walking was measured to test the hypotheses that the vertical ground reaction force is unevenly distributed and makes some (regions of the) claws more prone to injuries due to overloading than others. Each limb of nine recently trimmed Holstein Friesian cows was measured five times while walking over a Footscan pressure plate firmly embedded on a Kistler force plate. The pressure plate had a spatial resolution of 2.6 sensors/cm2 and was sampled simultaneously with the force plate with a temporal resolution of 250 measurements/s. Five moments during the stance phase were selected on basis of the force plate recording for the analysis of the pressure distribution: heel strike, maximum braking, midstance, maximum propulsion, and push off. At the forelimbs, the vertical ground reaction force was equally distributed between medial and lateral claw. At the hind limbs at heel strike, the force was exerted almost completely to the lateral claw. During the rest of the stance phase the load shifted towards the medial claw, until, at push off, it was more or less equally divided between both claws. The average pressures determined were 50 to 80 N/cm2. Maximum pressures increased from 90 to 110 N/cm2 at heel strike to 180 to 200 N/cm2 at push off. It was concluded that at the hind limb these pressures constitute a major threat to overloading particularly for the softer parts of the lateral claw, e.g., the sole and bulb area.

Prevalence of claw disorders in Dutch dairy cows exposed to several floor systems.

Claw health was examined in an observational study on Dutch dairy farms with either a slatted floor (SL), slatted floor with manure scraper (SL-SCR), solid concrete floor (SCF), a straw yard (SY), or a zero-grazing feeding system (ZG). Hooves of cows' hind legs were examined for the presence and severity of claw disorders during hoof trimming events at the end of the pasture (P-study) and housing period (H-study). The number of cows in each study was 3078 (49 herds) and 3190 (47 herds), respectively. Due to a different hoof trimming strategy, data collected during both observation periods in SY herds (638 cows; 16 herds) were combined. Cows in straw yards (SY) had by far the lowest numbers of claw disorders. Over 80% of cows exposed to concrete flooring had at least one claw disorder at the time of observation, whereas on SY surfaces, this percentage was between 55 and 60. Cows on SL-SCR were less frequently affected by interdigital dermatitis/heel erosion (IDHE) and digital dermatitis (DD) than cows on SL (reference floor system). Little difference in claw health was found between SF and SL. The ZG cows were at higher risk (OR > 2) for most claw disorders in the P-study, whereas in the H-study, ZG cows showed less IDHE, sole hemorrhage, and sole ulcer. All herds on concrete flooring (SL, SL-SCR, SCF, ZG) were infected by DD, resulting in an average cow level prevalence of 30%. This indicates that the level of DD infection has increased considerably over the last 10 yr in The Netherlands.

In vitro growth of mastitis-inducing Escherichia coli in milk and milk fractions of dairy cows.

The outcome of E. coli mastitis in cows ranges from mild to severe in individual animals. This study explored the hypothesis that milk from individual cows differs in its growth medium properties for E. coli, and whether possible variation could be related to specific milk constituents. To mimic the early phase of intramammary E. coli infection, a low inoculum size and a short incubation period were used. Cell-reduced, cell- and fat-free (skim) and cell- and fat-free and protein-reduced (whey) fractions were prepared from whole milk samples (n=18). Ten ml of whole milk, milk fractions and brain heart infusion broth (BHI) were inoculated with approximately 100cfu E. coli. After 6h of incubation, bacterial counts were assessed by dilution plating in triplicate. Bacterial counts in whole milk differed up to a 100-fold between cows, which was not associated with SCC. Bacterial counts were significantly higher in whey fractions than in whole milk, cell-reduced and skim fractions and variation in whey was smaller, indicating that the acid-precipitable protein fraction contains the milk constituents of major relevance for inhibition of and variation in bacterial growth. The presence of fat and cells added to bacterial growth inhibition to a lesser extent. In conclusion, in vitro growth of E. coli in milk differs substantially between individual cows within an incubation period comparable with the early phase of intramammary infection. This suggests that the growth medium properties of milk could be of importance in the pathogenesis of E. coli mastitis and subsequent outcome of disease.

The pressure distribution under the bovine claw during square standing on a flat substrate.

The distribution pattern of pressure over the bovine claw was investigated to test the hypothesis that the ground reaction force is unevenly distributed and makes some regions of the claw more prone to overloading and injury than others. In eight recently trimmed Holstein Friesian cows, the distribution of vertical pressure was measured during square standing with a spatial resolution of 2.6 sensors/cm2 and a temporal resolution of 313 measurements/s. In each animal, the localization of maximum pressure per foot and per claw was determined during five trials. In the front limb, maximum pressures were normally found on the medial claw; in the hindlimb they were located on the lateral claw. In both claws, the highest pressures were found on the sole of the foot and not on the wall. In the front limbs, maximum pressures were located in the posterior portion of the sole; in the hind limb in the anterior portion. There was no difference in the location of the maximum pressure between the medial and lateral claw in either limb. The regions in which these maximum pressures occur are known to be relatively susceptible to injuries. This could indicate a causal relation between the location of pressure concentrations and claw diseases found in clinical observations.

[Biotechnology: hail to man and animal]. / Biotechnologie: tot heil van mens en dier.

There are two basic remarks that must be made about this series of articles on the theme 'Modern biotechnology: a blessing or concern?'. Firstly, it is difficult to define what 'biotechnology' is due to the diversity of techniques employed. Secondly, it is striking how biotechnological techniques may be employed for such a wide variety of goals. In this article, the ethics of using biotechnology within veterinary science and research will be discussed. Aside from its usefulness to humankind, an animal has its own value as a living creature; a fact that we should always take into account. Ethical issues such as the health, welfare and integrity of animals are discussed here in relation to developments in biotechnology. These ethical arguments reveal that biotechnology does not always have a positive impact on animals. This does not necessarily mean that biotechnology should be rejected out of hand, but that it is essential that the purpose for which the animals are being used be adequately justified. In this regard, the veterinarian may play a unique role as the guardian of both animal and human health. The veterinary profession, in all its diversity, is a participant in the development and (future) practical application of biotechnological techniques. Changes in the broader society and within the veterinary profession may continue to play a role in the societal discourse on biotechnology and its practical application, it must actively consider the ethical aspects and consequences of these scientific developments.

Hyperketonemia and the impairment of udder defense: a review.

The objective of this study was to review the possible relationships between hyperketonemia and the function of phagocytes with respect to the bovine udder defense mechanism. We hypothesize that an increased incidence of clinical mastitis in high-producing cows is caused by the impairment of the udder defense mechanism during hyperketonemia. First, we review the acute phase of udder defense mechanisms after intramammary infection. The physiological changes of cows in negative energy balance are subsequently discussed. Finally, possible relationships between udder defense and physiological changes during negative energy balance, especially hyperketonemia, are reviewed. The three stages of an acute phase of udder defense are: (1) immediately eliminating invading pathogens by phagocytes, (2) releasing inflammatory substances, especially chemoattractants, and (3) migration of polymorphonuclear leukocytes into the infected udder. Leukocytes from hyperketonemia subjects show a lower capacity of the phagocytic defense mechanism. In addition, the phagocytic and bactericidal capacities of neutrophils are reduced when these cells are acting in the presence of high concentrations of ketone bodies. Lower amounts of cytokine production after bacterial infection are observed in ketotic subjects. The chemotactic capacity of blood leukocytes is impaired in leukocytes obtained from ketotic cows. Lower numbers of blood leukocytes are observed in ketotic cows. In conclusion, the impairment of the udder defense mechanism in negative energy balance cows seems related to hyperketonemia.

Beta-hydroxybutyrate levels in peripheral blood and ketone bodies supplemented in culture media affect the in vitro chemotaxis of bovine leukocytes.

The role of ketone bodies on chemotactic capacities of leukocytes was characterized in two experiments. Experiment I was performed to investigate the association between serum beta-hydroxybutyrate concentrations (BHB) and in vitro chemotaxis of leukocytes. Cows were divided into low-BHB, medium-BHB, and high-BHB ones and classified according to their BHB. Leukocytes from high-BHB cows had a significantly lower chemotactic differential than leukocytes from low-BHB cows (p < 0.01). The effect of adding ketone bodies into in vitro chemotaxis cultures on leukocytes chemotaxis was studied in Experiment II. Either individual or a combination of commercial ketone bodies - sodium salts of BHB (BHBA), lithium salt of acetoacetate (ACAC), and acetone (Acetone) - were diluted in culture media and divided into eight concentrations corresponding to concentrations of bovine subclinical and clinical ketosis. For leukocytes from medium- and high-BHB cow, the chemotactic indexes of leukocytes were reduced by ACAC and Acetone. Chemotactic differentials of cultures with ACAC and acetone supplementation from both sources of leukocytes were significantly lower than that of the control culture (p < 0.05). For leukocytes from high-BHB cows, chemotactic indexes were suppressed in a ketone-body environment. In conclusion, leukocytes from naturally-occurring ketotic cows have lower chemotactic differentials than those from non-ketotic cows, and a chemotactic capacity indicated by a chemotactic differential is impaired when leukocytes migrate in an environment with ketone bodies in vitro.

Evaluation of the role of endotoxin and cortisol on modulation of CD18 adhesion receptors in cows with mastitis caused by Escherichia coli.

OBJECTIVE: To determine the effect of mastitis caused by Escherichia coli on expression of CD18 cell surface receptors and to evaluate the involvement and regulation of receptors by lipopolysaccharide (LPS) and cortisol. ANIMALS: 11 clinically normal lactating Holstein-Friesian cows. PROCEDURE: Binding of CD18 monoclonal antibodies to neutrophils was studied, using flow cytometry, before and after intramammary inoculation of E. coli organisms. Effect of LPS and cortisol on expression of adhesion receptors was investigated, using a whole-blood model. RESULTS: Expression of CD18 adhesion receptors on bovine neutrophils increased 35% by 12 hours after intramammary inoculation of E. coli. By 24 hours after inoculation, the number of receptors had returned to control values. High cortisol concentrations (100 nmol/L) were seen 12 to 18 hours after inoculation. Addition of LPS to blood induced a 30% increase in the number of CD18 receptors, and maximal number of receptors was expressed at an LPS concentration of 0.1 ng/ml. A decrease in the number of CD18 receptors was induced by incubation with cortisol or dexamethasone before challenge-exposure with LPS. CONCLUSIONS: An increase in the number of CD18 receptors on neutrophils is mediated by local production of LPS. Subsequent endogenous release of cortisol may prevent additional increases in the number of receptors. CLINICAL RELEVANCE: During acute mastitis caused by E. coli, there is an increase in the number of CD18 receptors on circulating neutrophils. Cortisol induces a decrease in the number of CD18 receptors, probably modulating the acute inflammatory response in mammary glands of lactating cows.