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Biomedical subjects

R A Laven

Publications and source records attributed to R A Laven.

At least 19 recordsLinked to original sources
PubMed2006

An evaluation of the effect of clotting on the relationship between copper and caeruloplasmin in bovine blood.

The ratio of caeruloplasmin activity to copper concentration (CP:Cu) has been suggested as a more accurate determinant of the requirement for additional copper than plasma or liver copper concentrations. Although this test has no peer-reviewed evidence of efficacy, it has been used by a large number of UK veterinarians. However, the available test uses a serum caeruloplasmin (sCP) activity to plasma copper (pCu) concentration ratio which, because of the preferential loss of caeruloplasmin during clotting, is likely to underestimate the true CP:Cu, although it has been suggested that the marginal range accounts for this. This study was undertaken to evaluate the effect of using serum copper (sCu) rather than pCu concentrations in calculating CP:Cu. Using sCu rather than pCu increased CP:Cu by more than was accounted for by the marginal range. Of 48 cattle which were reported as 'low' using sCP:pCu, 22 were 'normal' when sCu was used instead of pCu. All herds with 'marginal' or 'low' mean CP:Cu when the sCP:pCu concentration ratio was used had 'normal' ratios when sCu was used instead of pCu.

Animals↗
PubMed2006

The effect of pre-calving environment on the development of digital dermatitis in first lactation heifers.

Digital dermatitis is commonly reported to be most severe in first lactation heifers. It has been suggested that this initial infection is followed by the development of a limited immunity to the organisms which cause digital dermatitis. If this is the case then exposure to digital dermatitis prior to calving should reduce its severity after calving. A study was undertaken to examine whether such exposure significantly affected the development of digital dermatitis post-partum. Twelve weeks prior to calving, 60 Holstein heifers were blocked on the basis of their antibody titre to Borrelia burgdorferi and randomly allocated to one of three pre-calving environments: clean straw, used straw or cubicles. There was no significant effect of pre-calving environment on the development of digital dermatitis after calving indicating that "exposure" pre-calving did not reduce the development of digital dermatitis after calving. The most important factors determining the development of digital dermatitis after calving were presence of absence of visible lesions of digital dermatitis at Week-12 and at calving.

Animals↗
PubMed2006

Factors affecting the monetary return from programmes for synchronising oestrus in dairy cows with gonadotrophin-releasing hormone and prostaglandin F2alpha.

Synchronisation, using a combination of gonadotrophin-releasing hormone and prostaglandin F2alpha injections, is commonly used to control the reproductive cycle of dairy cows. A simple model that could predict the monetary return from synchronisation would be a valuable tool in determining whether it would be worthwhile. This study used data from three controlled clinical trials to investigate the effects of six factors (interval between calving and synchronisation, 21-day submission rate, number of cows synchronised, average age, pregnancy rate of non-synchronised cows and season) on the return from synchronisation. The results suggests that the herd's submission and pregnancy rates, the time between calving and synchronisation, and the number of cows synchronised can all significantly affect the return from synchronisation, but only time since calving significantly affected the return in all three trials. They also suggest that there is no simple linear relationship between these factors and the return from synchronisation.

Age Factors↗
PubMed2006

Treatment strategies for digital dermatitis for the UK.

Digital dermatitis is a worldwide disease causing lameness in cattle, especially when housed. Despite its widespread nature there are relatively few peer-reviewed articles providing experimental data concerning its treatment and control. At the risk of descending to anecdote, this review attempts to summarise the current state of knowledge. Three approaches to digital dermatitis treatment have been used: (1) systemic antibiotics, (2) individual topical treatment, and (3) mass topical therapy using a footbath. Systemic antibiotics have become a rare treatment because of their cost and perceived lack of efficacy. Individual topical treatment, mainly with antibiotic preparations, is the most commonly reported method. It is widely considered the treatment of choice by virtue of reliable information about efficacy, the advantage of precise targeting of antibiotic usage and the requirements of legislation. However, at least in the UK, mass treatment of digital dermatitis by foot bathing is commonly used on many farms. In some cases, for example with antibiotic footbath solutions, these treatments create legislative, health and safety and environmental difficulties. Despite the widespread use of many different treatments, there is a lack of good comparative data and the consequence is a very variable and somewhat anecdotal approach in the field. There is a pressing need for well-researched treatment strategies for different herd situations.

Administration, Topical↗
PubMed2006

An evaluation of the seasonality of veterinary treatments for lameness in UK dairy cattle.

Of the 4 main diseases causing lameness in UK dairy cattle, 2 (digital dermatitis and foul-in-the-foot, or interdigital necrobacillosis) are infectious diseases that are commonly associated with similar underfoot conditions, and 2 (sole ulcer and white-line disease) result from subclinical laminitis. Comparison of the seasonality of these 2 diseases can identify whether their own unique risk factors are more important than the risk factors they share. Using a database from 46 veterinarians distributed across the United Kingdom, the seasonality of treatments for these 4 diseases was evaluated. This analysis showed that the seasonality of lameness in UK dairy cattle was significantly reduced in comparison with previous reports from the 1980s. This was primarily due to 1) a reduction in the seasonality of digital dermatitis (outbreaks of which accounted for 6.7% of veterinary reports), with only 60% of reports during the winter as opposed to 72% in earlier studies, and 2) a change in the seasonality of white-line disease from a disease that was most commonly seen in the winter (55% of reports) to a disease that was most commonly reported in the late summer or early autumn, with significantly more reports in August and October than in February. Comparison of the seasonality of digital dermatitis and foul-in-the-foot showed a significant difference in the seasonality of the 2 diseases, with foul-in-the-foot being significantly more common compared with digital dermatitis in June and August. This implies that significant risk factors exist for digital dermatitis that are not as important for foul-in-the-foot. The difference in the seasonality of sole ulcer and white-line disease was even more marked, with white-line disease being significantly more common than sole ulcer from August to October, despite these diseases being more closely linked in the literature than digital dermatitis and foul-in-the-foot. This comparison shows that the seasonality of lameness has changed in the United Kingdom and that white-line disease has significantly different risk factors than sole ulcer.

Animals↗
PubMed2004

An evaluation of the effect of clotting and processing of blood samples on the recovery of copper from bovine blood.

The reference ranges for blood copper (Cu) concentration used by SAC and the UK Veterinary Laboratories Agency have been developed for use with plasma only. Copper sequestration into the clot, primarily in the form of caeruloplasmin, means that serum Cu concentrations are significantly lower than plasma Cu concentrations in the same animals. Serum Cu is commonly used as a surrogate for plasma Cu by applying a proportional conversion factor. However the results of these two studies, which involved a total of 104 pairs of serum and Cu samples from 84 Holstein cattle in one herd, suggest that serum Cu concentrations should not be used in this way. First, the reduction in Cu concentration during clotting was unrelated to initial plasma concentration (varying from 8-59%), which suggests that using a proportional conversion factor is incorrect. Secondly, the correlation between plasma and serum Cu concentration, while significant, was relatively low (r2 proportional 0.6), with the individual variation in Cu loss during clotting ranging from 1.5 to 10.8 micromol/L (mean 4.9 micromol/L). Although this study was undertaken using samples from normocupraemic lactating Holstein cattle in one herd, the data strongly suggest that plasma rather than serum Cu should be used to estimate Cu status unless the laboratory used has developed a reliable serum reference range. We also found that factors other than plasma Cu concentration had a significant effect on loss of Cu during the clotting process. However, no significant effect on the loss of Cu during clotting or by varying the incubation/storage time and temperature of bloods prior to clot removal was noted, nor was there any significant effect of age or Cu intake. Furthermore, when the loss of Cu during clotting was examined in the same heifers at two different timepoints, no correlation between the results was found. Further research is required to establish the factors that affect the loss of Cu during clotting.

Animal Nutritional Physiological Phenomena↗
PubMed2004

Relationship between acute phase proteins and hoof horn haemorrhages in postpartum first-lactation heifers.

As part of a study of the development of hoof horn haemorrhages in first-lactation heifers, measurements were made of acute phase reactants to investigate the link between the acute phase response and the development of the haemorrhages. Over a period of two years, blood samples were taken from two separate groups of heifers, weekly in the three weeks before they calved and then twice weekly until eight weeks after calving. Plasma total protein, albumin, fibrinogen, haptoglobin, seromucoid and serum iron and caeruloplasmin were measured and the relationships between the peak concentration (or activity) or the area under the curve of each acute phase reactant and the peak scores for sole or white line haemorrhages were assessed by linear regression. The results suggested that the development of the hoof horn haemorrhages observed in the study was not accompanied by an acute phase response, and the haemorrhages were therefore not primarily caused by endotoxicosis. The diets and husbandry systems used were typical of dairy farms in the UK and the results therefore suggest that a significant proportion of hoof horn haemorrhages observed in UK dairy cows may not be caused by endotoxicosis.

Acute-Phase Proteins↗
PubMed2004

The effect of a diet containing excess quickly degradable nitrogen (QDN) on reproductive and metabolic hormonal profiles of lactating dairy cows.

The objective of this experiment was to examine the effects of an excess intake of quickly degradable nitrogen (QDN) on metabolic and reproductive parameters in lactating dairy cows. Twenty-two lactating dairy cows were fed a total mixed ration once daily. The control diet was a typical ration for high producing cows in the UK (CP = 17.5%, ME = 11.8 MJ/kg DM). The cows were randomly divided into two groups, control diet (control; n = 12) and excess QDN diet (QDN; n = 10). The QDN group was fed an additional 250 g of urea per cow per day, from 10 days before insemination (day 0) until the end of the experiment, 17 days after the second insemination. Ten days before insemination, a synchronized oestrus was induced and the cows inseminated twice, 48 and 72 h after synchronization, with commercial frozen semen from a single sire. Ovaries were scanned using B-mode ultrasonography 10 days before insemination and then daily from 3 days before insemination. Eighteen of the cows (9 control and 9 QDN) were sampled more intensively to determine the pulsatile pattern of secretion of luteinizing hormone (LH) and growth hormone (GH). Cows were slaughtered 17 days after insemination, the reproductive tracts recovered and flushed to retrieve embryos. The excess QDN diet resulted in elevated (P < 0.05) plasma urea concentrations 3 days after starting urea feeding and these were maintained until the end of the experiment. However, the excess QDN diet did not significantly affect daily milk production or plasma concentrations of insulin and IGF-I. The QDN treatment did not significantly affect pulsatile patterns of secretion of LH and GH or the number of small (< 0.5 cm diameter) and medium to large follicles (> 0.5 cm diameter). Twenty cows ovulated following synchronization (control 11/12; QDN 9/10). There were no significant differences between the control and the QDN groups in the peak concentrations of oestradiol during the follicular phase or in the post-ovulatory pattern of plasma and milk progesterone secretion. Embryos and/or foetal membranes were recovered from 10 cows (5 control and 5 QDN). The results of the current study show that feeding excess QDN, as urea, for 27 days commencing 10 days before insemination had no effect on reproductive or metabolic hormonal parameters. Ovulation and the formation and function of the post-ovulatory corpus luteum were also unaffected by excess QDN. These data suggest that the harmful effects of excess intakes of QDN on fertility occur after 17 days following ovulation.

Animals↗
PubMed2004

The effect of feeding diets high in quickly degradable nitrogen on follicular development and embryo growth in lactating Holstein dairy cows.

This study investigated the effect on follicular and embryo development of increasing quickly degradable nitrogen (QDN) intake in lactating Holstein dairy cows. Forty mature post-partum cows were fed one of two diets for a minimum of 10 weeks, starting 10 days before first insemination. The Control diet was a high production dairy ration. The High QDN diet comprised the Control ration plus 250 g urea/head/day. Both diets were formulated to ensure that the energy requirements of the cows were satisfied. The High QDN treatment resulted in a significant increase in milk urea, plasma urea and plasma ammonia concentrations. The highest plasma urea (8.2 mmol/l) and ammonia concentrations (120 micromol/l) were recorded within 7 days of the urea supplement being added to the diet. There was no effect of diet on plasma progesterone or glucose concentration. There was also no significant effect of treatment on follicular development or embryo growth. The results from this study suggest that the lactating cow can adapt to increased intakes of QDN if the increase starts at least 10 days before insemination.

Ammonia↗
PubMed2004

The effect of housing and methionine intake on hoof horn hemorrhages in primiparous lactating Holstein cows.

This study investigated the effects of housing and nutrition on the development of hoof horn disease (as identified by the appearance of hoof horn hemorrhages) in primiparous lactating Holstein cows. The first objective was to investigate whether replacing butyl rubber mats in cubicles (free stalls) with thicker mattresses filled with chopped rubber would significantly reduce hoof horn hemorrhages, and if this reduction would so affect the level of hoof horn hemorrhages as to make it similar to that observed in primiparous cows in straw yards. The second objective was to investigate the effect of methionine supplementation for the first 13 wk of lactation on the development of such hemorrhages. This study confirmed that both sole and white line hemorrhages increase during early lactation in housed cows, although the pattern of development of white line hemorrhages is not identical to that of sole hemorrhages. Housing primiparous cows in straw yards after calving significantly reduced the development of hoof horn hemorrhages, but replacing cubicle mats with thicker mattresses had no significant effect. Providing 115% of calculated methionine requirements had no significant impact on the development of hoof horn hemorrhages.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Effect of concentrate composition and cubicle bedding on the development of hoof haemorrhages in Holstein heifers after calving.

Diseases of the hoof horn are the most common cause of lameness in the UK dairy herd, and diet, particularly starch intake, is commonly implicated in their development. This study assessed whether replacing starch carbohydrate with sugar beet pulp, in a diet containing 50 per cent of the dry matter as forage, would significantly reduce the development of hoof horn haemorrhages in dairy heifers after calving. It also investigated the effect of replacing wood shavings as cubicle bedding with chopped straw. The heifers fed the high-fibre diet had a significantly lower yield of milk protein and a significantly higher yield of milk fat than the heifers fed the high-starch diet, indicating that the change of diet had affected rumen fermentation. However, the change had no significant effect on the development of hoof horn haemorrhages. The change of bedding material also had no significant effect on the development of hoof horn haemorrhages.

Animal Feed↗