A field evaluation of a footbathing solution for the control of digital dermatitis in cattle

Footbathing is one of the most commonly used methods for controlling digital dermatitis (DD). A farm-based trial was undertaken using six dairy herds involving over 600 cubicle-housed Holstein-Friesian cattle. Split footbaths (length 2.2m) were used to compare the efficacy of two dips, namely, a positive control (5% copper sulphate) and a non-heavy metal-based proprietary dip. The dips were used from early January 2009 for a minimum of 103 days, bathing twice a day for 3 consecutive days every week, using one footbath (three herds) or two in line (three herds). The lesions of DD on the hind feet of cattle were scored by borescope while the animals were being milked, on three occasions (at approximately days 0, 55 and 110) and then compared both directly and by calculating the change in severity from the previous examination (when possible). Data from the 408 cows that had their feet examined for lesions on all three occasions were analysed separately. A reduction in lesion score was seen for both footbath products, but feet bathed in 5% copper sulphate improved more (OR=1.6, CI: 1.14-2.32; P<0.01), and, irrespective of solution, there was a significantly greater improvement in those herds where two footbaths were used (OR=3.39, CI: 2.07-5.19; P<0.001). Lesion improvement over time also increased with lactation number (OR=1.13, CI: 1.02-1.25; P<0.05).

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.

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.

Effects of type of forage fed to dairy heifers: Associations between claw characteristics, clinical lameness, environment and behaviour

Heifers were reared separately on wet fermented (WF) (grass silage based) or dry unfermented (DU) (straw based) diets. Clinical lameness was recorded and physical claw attributes were measured regularly, up to six months after calving at approximately two years of age. Two months before calving, some aspects of animal behaviour and the properties of slurry were studied. The incidence of lameness due to claw horn lesions was significantly higher (P < 0.01) in WF than in DU. WF suffered more serious heel erosion prior to calving (P < 0.05) and had softer claw horn at two (heel and axial sole) out of five sites throughout (P < 0.01 and P < 0.05). The slurry produced by WF had lower total solids content (P < 0.05) and viscosity (P < 0.001). WF spent longer standing and feeding (P < 0.001). It is proposed that standing for longer in less viscous slurry contributed to softer claw horn and more severe heel erosion, predisposing WF to claw horn lesions causing lameness. Reducing contact with low dry matter slurry is recommended for improving claw health.

Effect of forage type on claw horn lesion development in dairy heifers

In a continuous design study the claw health of 54 Holstein-Friesian heifer calves was recorded from three months of age until six months after first calving (30 months of age). Pre-calving heifers were either fed a wet, fermented grass silage-based diet (WF) or a dry, unfermented straw and concentrate based diet (DU), apart from grazing during their first summer. Approximately one month before calving both groups were fed a silage-based diet and afterwards all received a silage and concentrate lactation ration. Claws were examined four times during rearing, once pre-calving, and four times during lactation. Both white line and sole lesions were significantly worse for WF than DU both during rearing and throughout first lactation although the effect was not as consistent over time for white line lesions. It is concluded that for optimal claw health youngstock diets should not be heavily based on wet grass silage (less than 25% DM).

Effects of time of year and reproductive state on the proliferation and keratinisation of bovine hoof cells

Cell proliferation and protein synthesis (keratinisation) were measured in vitro in hoof biopsy samples taken from two groups of seven heifers, the first calving in the winter and the second in the summer. Both parameters were significantly higher in summer than in winter irrespective of the heifers' reproductive state. The mean (se) measure of the rate of protein synthesis was 199 (27) dpm/microg DNA/hour in summer and 4 (1) dpm/microg DNA/hour in winter, and the equivalent values for cell proliferation (measured as DNA synthesis) were 375 (56) dpm/microg DNA/hour and 17 (4) dpm/microg DNA/hour. Changes around parturition depended on the time of the year. In the winter-calving heifers, the rates of proliferation and keratinisation increased significantly after calving from 22.3 (7.2) to 70.4 (16.6) and from 2.1 (0.7) to 12.4 (2.8) dpm/microg DNA/hour, respectively. In the summer-calving heifers, proliferation decreased from 388.2 (91.0) to 66.7 (9.6) dpm/microg DNA/hour but the rate of keratinisation did not change. Lesion scores and locomotion scores deteriorated after parturition, especially in the winter-calving group. The hooves were harder in summer than winter but their hardness was not affected by the heifers' reproductive state.

A systematic compilation and classification of the literature on lameness in cattle

This paper presents the first systematic review of the literature on lameness in cattle. It identifies, tabulates and classifies relevant published work and was conducted using electronic reference databases (BIDS ISI, BIOSIS, MEDLINE and the CAB Abstracts CD-ROM). A total of 1373 unique references were obtained from 1981 to 2000, of which 914 were written in the English language. A written search protocol was designed to ensure transparency and repeatability. Pilot studies were undertaken to create search terms that minimised bias and ensured relevance. Electronic files of the search terms allow the database to be updated in future. A further 93 references were included from the most recent international conference on lameness giving a total of 1007 English language references. The systematic review process is described, including a method of classifying papers according to their study design and statistical analysis, and it is hoped that other veterinary researchers will conduct similar reviews in their fields. The compiled and classified references are available as a searchable database through the web-sitehttp://cattle-lameness.dhs.org/. The review may be used in several ways; to identify practical interventions to reduce lameness in dairy cows and to use the resultant web-site as the basis of a decision support system for farmers, veterinarians and advisors.

The effect of feeding grass silage in early pregnancy on claw health during first lactation

Two groups of eight Holstein-Friesian heifers were fed either a grass-silage-based diet (S) or one based on meadow hay supplemented with 1.8 kg/day barley concentrate mix (H) during cubicle housing as young stock (and in early pregnancy). Lameness and claw lesion development were monitored from approximately four weeks before until 20 weeks after first calving. No significant difference was found between S and H for claw conformation or horn growth and wear. Both groups showed net wear immediately after calving. The prevalence of poor locomotion and the extent of lesion development 20 weeks after calving (when they were highest) were significantly (P< 0.05) higher in S than H. It was concluded that feeding grass silage to young stock may deleteriously affect subsequent claw health and that this risk factor requires further study.

Correlations of measurements of subclinical claw horn lesions in dairy cattle

Measurements were made of the extent of sole and white line lesions on the claws of 115 Holstein-Friesian cows on at least three and at most 16 occasions, and some cows were followed up to their third lactation. All the measurements were made between 12 weeks before calving and 45 weeks after calving. In total, 1016 repeated observations were made. Correlations were calculated between pairs of claws, between types of lesion (sole and white line), and between pairs of the different measurements (number of lesions, proportion of the claw affected, maximum severity score and proportion of the claw affected weighted for severity). The outer hind claws had the greatest extent of lesions of both types. Spearman correlation coefficients and confidence intervals measured the strength of the association. All the associations between claws were positive, suggesting that the lesions did not occur in isolation. Sole and white line lesions were not associated at individual observation points. Lesions on the left and right claws were markedly similar, except for sole lesions on the two inner hind claws, and for white line lesions on the two outer hind claws.

Observations of lameness, hoof conformation and development of lesions in dairy cattle over four lactations

Lameness and lesions in the claws of 31 autumn-calving Holstein Friesian dairy cows were recorded from before their first-calving until their fifth lactation. The animals were managed by the same herdsman and housed adjacently in the same building in one of two herds grazed either on clover-rich pastures (herd 1) or on conventional ryegrass (herd 2). All four hooves were examined routinely four times during each lactation, and claw lesions were scored for severity and drawn on hoof maps. Heel erosion and infectious skin conditions of the hoof were also recorded, and hoof conformation, hardness, and growth and wear were measured. The animals' locomotion was scored weekly throughout the winter housing period and any observed to be lame were examined to determine the cause. The development of lesions was modelled by using hierarchic smoothing splines. There was no significant effect of herd except on the prevalence of lameness in lactation 2 when the incidence of (inter)digital dermatitis was higher in herd 2. Lesion and locomotion scores were significantly higher by lactation 4 (P<0.05). There were significant effects (P<0.05) of weeks postcalving on lesion formation, claw conformation, and heel erosion.

Efficacy of two non-antibiotic therapies, oxytocin and topical liniment, against bovine staphylococcal mastitis

Eight cows were challenged by a single quarter intramammary infusion of a relatively low-virulence strain of Staphylococcus aureus on four occasions five weeks apart and, after each challenge, each cow received one of four treatments, according to a duplicated Latin-square design. The treatments were massage alone (negative control), massage with a proprietary liniment, oxytocin, and a single course of a proprietary intramammary antibiotic. The massage treatments were applied at every milking for three weeks, oxytocin was given for one week, and the antibiotic was given after three successive milkings. Milk samples were collected immediately before and for three weeks after each challenge, and a scoring system was used to quantify the presence of bacteria during the whole of the period. None of the treatments completely eliminated bacteria from all the cows. Relative to the negative control, the liniment had no significant effect, but both oxytocin and the antibiotic reduced the numbers of bacteria significantly and did not differ significantly in efficacy.

An evaluation of mattresses and mats in two dairy units

In order to investigate the relative merits of mats and mattresses in terms of cow comfort, production and performance, 29 cows were housed on ethylethene vinyl acetate (EVA) mats and 29 on mattresses of loose rubber crumb with a polypropylene cover, at each of two similar dairy units (SAC Auchincruive and Myerscough). Both mats and mattresses were newly installed at the start of the trial. The cows were housed in the autumn after calving. Milk yield was recorded daily. Cows were weighed and scored for body condition, locomotion, dirtiness and hock and knee injury at fortnightly intervals. Feed offered was recorded daily and refusals were weighed weekly. Monthly milk records of milk yield, milk composition and somatic cell count data were available for both herds. In addition, 24 h behavioural observations of 15 core cows in each group were made at weeks 0, 2, 4, 6, 8, 16, and 32 post-housing. There was no difference between cows on mats and mattresses in milk yield, composition or quality; in feed intake; in weight loss or body condition score; in severe hock or knee injury, or in the incidence of lameness. Cows on mattresses tended to have slightly higher total dirtiness scores than those on mats (7.06 vs. 6.95, P=0.074) and had dirtier udders (mattress, 7.50 vs. mat, 6.52, P<0.05). However, over the whole housing period, cows on mattresses spent longer feeding, ruminating and lying and a greater proportion of their lying time was spent ruminating. They spent less time standing doing nothing (idling) than cows on mats and less time idling in cubicles. Cows on mattresses appeared to adapt to housing more quickly than those on mats. Overall, neither mat nor mattress gave advantages in terms of production or performance, cows were slightly cleaner on mats but behavioural indices suggest that cow comfort was greater on mattresses.

A comparison of hoof lesions and behaviour in pregnant and early lactation heifers at housing

Lameness, hoof lesion development and behaviour were compared for two groups of 10 heifers: one in early pregnancy (PH), the other in early lactation (LH). Both groups were housed in the summer in cubicles under identical conditions. Behavioural observations commenced immediately after housing, and then at 2, 4 and 6 weeks post-housing. Locomotion scores were assessed weekly, and feet were examined for lesions at approximately -1, 0, 1 and 2 months after housing. All four feet were photographed, lesions were scored subjectively for severity, and lesion size and position were estimated using image analysis techniques. LH already had greater total lesion scores before housing. More severe linear lesions in the LH group were associated with reduced lying, and less idling, increased standing in cubicles and more disturbed lying behaviour.

The economic impact of mastitis-control procedures used in Scottish dairy herds with high bulk-tank somatic-cell counts

We used multiple-regression analysis of field data to quantify the marginal impacts of various mastitis-control procedures on bulk-tank somatic-cell count (BTSCC). Estimates of milk-yield depression and the probability of herds paying a BTSCC penalty due to the presence of subclinical mastitis were made. An assessment of the economic efficiency of mastitis control by high BTSCC producers was also made using a loss-expenditure frontier. Significant interactions were detected between premilking udder-preparation methods (UP) and post-milking teat disinfection (PMTD), and also between the milking system of the herds and both the use of dry-cow therapy (DCT) and a regular milking-machine test (MMT). Udder preparation involving washing was associated with a higher SCC and had a detrimental effect on the efficacy of PMTD. Amongst herds facing a high-BTSCC problem (BTSCC >400,000 cells/ml), herds using PMTD without UP (regardless of the type of milking system), those using DCT (in parlour systems), and those with a parlour system having their milking machines tested obtained returns of Pound Sterling 1.4, Pound Sterling 3.9 and Pound Sterling 1.1, respectively, per Pound Sterling 1 investment in each of these procedures as a result of reductions in milk-yield losses and BTSCC penalties. The minimum total cost of disease within these herds was Pound Sterling 65.50/cow/year (due to Pound Sterling 41.40 revenue losses plus Pound Sterling 24.10 mastitis-control expenditure) attained by herds which had a parlour system and used DCT, MMT and PMTD (without UP). However, the average cost of subclinical mastitis for all high-BTSCC farms was Pound Sterling 100/cow/yr; hence, the difference (pound Sterling 34.50) could be saved by the more-efficient application of mastitis-control procedures.

Claw lesions in dairy cattle: methods for assessment of sole and white line lesions

Claw lesions are a major cause of lameness in dairy cattle. Analysis of the development of lesions is aided by numerical representation of their significance. Using data from observations on 31 heifers at 9 weeks post-calving, 5 lesion scoring method were compared. These were: (1) number of lesions; (2) severity; (3) adjusted severity; (4) size (measured by a novel technique involving image analysis of distal view photographs) and (5) size multiplied by adjusted severity (combined score). Relationships between scores for sole and white line lesions and between different claws within a cow were investigated. The small size but high clinical significance of severe lesions means that severity must be weighted if combined with size in a score. Sole and white line lesions showed a moderate but significant correlation in terms of severity but none in terms of size. The highest correlation between scores for a single claw (the right hind outer) and the remaining claws was found for adjusted severity of sole lesions.

Claw lesions in dairy cattle: development of sole and white line haemorrhages during the first lactation

The development of claw haemorrhages was monitored in first-calving dairy heifers from 4 weeks before calving to 32 weeks after calving. Before calving, lesions were few but the number, extent and severity of claw haemorrhages increased following simultaneous calving and housing. Lesions were most severe in the white line at 9 weeks, and in the sole at 14 weeks, but recovery began while the animals were still housed. That the increase in white line lesions after calving, and the subsequent recovery preceded that of the sole, suggests that the pathogenesis of the lesions may differ in these two anatomical regions. It is proposed that an initial insult to the corium primarily affects the laminar region and that corium damage increases with the resulting alteration in the physical forces on the sole.

A study of mastitis bacteria and herd management practices to identify their relationship to high somatic cell counts in bulk tank milk

Thirty dairy herds, selected to cover a wide range of bulk tank somatic cell count (BTSCC) values, were used to study the relationship between the levels of the principal species of mastitis-causing bacteria, herd management practices and the BTSCC. A good correlation was found between the number of mastitis streptococci (Streptococcus agalactiae, S. dysgalactiae and S. uberis) found in bulk tank milk and the BTSCC. Staphylococcus aureus was less significantly correlated to BTSCC, but was of increasing importance in borderline BTSCC herds, where lower excretion levels into milk were unlikely to trigger hygiene penalties and so alert producers to the presence of a significant mastitis problem. High BTSCC herds had significantly lower yields and were less likely to use a post-milking teat dip or to have a regular programme of milking machine maintenance or automatic cluster removal. These herds also tended to buy in replacements rather than breed their own. Overall the management of high BTSCC herds showed less commitment to implementing mastitis control procedures than herds with a consistently low BTSCC.

Ultrastructural observations of hoof horn from dairy cows: changes in the white line during the first lactation

Slivers of hoof horn were taken from the outer claw of the right hindfoot of 16 first calving dairy heifers one month before calving and one, 10 and 20 weeks after calving. The gross appearance of all four feet, and the presence and degree of solar haemorrhage were recorded. Ultra-thin sections of the white line were examined in the transmission electron microscope. Good quality horn showed good cellular structure and no amorphous or filamentous intercellular material. Horn of moderate quality showed areas of material in the intercellular spaces which caused the individual cells to separate and were accompanied by a loss of internal, cellular structure. Poor quality horn showed large areas of cellular destruction, red blood cells in intercellular spaces and a disruption of the pattern of keratinisation. The ultrastructural appearance of the white line was a sensitive indicator of the quality of the horn. At the start of the study all the heifers had good feet with minimal or no solar haemorrhage. Four of the eight heifers with poor quality horn one month before calving went on to develop severe solar haemorrhage 10 to 20 weeks after calving, two developed moderate (grade 3) haemorrhage and two developed slight haemorrhage. The eight heifers with good quality horn at the start of the study all showed little or only moderate solar haemorrhage by 20 weeks after calving.

Ultrastructural observations of hoof horn from dairy cows: the structure of the white line

The white line (zona alba) is the specialised region of the bovine claw capsule at the junction of the wall and the sole. It consists of two distinct components, both generated from epidermis overlying the laminar corium, and these were examined in the transmission electron microscope. One constituent of the white line is the laminar horn leaflet which was composed of fusiform squames. Within these squames the bundles of keratin fibres were orientated parallel to the laminar horn leaflets. The second components, the interdigitating horn, was composed of squames which were polyhedral in outline and contained tightly packed bundles of keratin fibres, orientated in various directions. These different ultrastructural appearances are thought to be associated with different mechanical properties for the two parts of the white line. No horn tubules were present in the interdigitating horn of the white line.

Evidence for the action of bovine follicular fluid factor(s) other than inhibin in suppressing follicular development and delaying oestrus in heifers

The aim of this study was to investigate the importance of inhibin in the delay in return to oestrus in heifers induced by steroid-stripped bovine follicular fluid (bFF). Oestrous activity was synchronized in 18 Hereford x Friesian heifers with two injections of prostaglandin (PG) 12 days apart. At the time of the second PG injection (time 0), the animals were assigned at random to one of three experimental groups and received i.v. injections of 20 ml saline (controls, n = 6), whole bFF (FF group, n = 6) or bFF in which the bioactive inhibin content had been reduced by > 95% by immunoaffinity chromatography (-INH group, n = 6; inhibin content approximately 0.8 ml whole bFF) every 8 h for 2 days. In a dose-response study, 2.5 ml whole bFF was insufficient to delay oestrus consistently following a similar synchronization regimen. Blood samples were taken every 8 h, initially before each injection and then subsequently for a further 9 days for hormone analysis. Animals were observed every 8 h throughout the experiment for signs of behavioural oestrus. The ovaries of all animals were examined using real-time ultrasonography about 30 h after the second PG injection. Treatment failed to suppress peripheral follicle-stimulating hormone (FSH) concentrations, although a significant increase was observed in both treatment groups after cessation of injections. Progesterone concentrations fell immediately after the second PG injection in all animals and remained below minimum detectable concentrations in all treated animals for the remainder of the experiment. In control animals, progesterone rose above minimum detectable concentrations by day 6 and continued to rise until the end of the experiment. Analysis of samples taken from treated animals several days after observed oestrus revealed that all had apparently ovulated. Mean daily luteinizing hormone (LH) concentrations did not differ between treatment groups before ovulation, but after ovulation, mean daily LH was significantly reduced in control animals as progesterone concentrations rose. Follicular development, as assessed by the mean antral diameter of the largest follicle on a pair of ovaries at ultrasound examination, was significantly suppressed in treated animals compared with controls (P < 0.01) and there was no significant difference (P = 0.397) between the two treatment groups. Control animals displayed oestrus 68 h (+/- 8 SEM) after the second PG injection, but oestrus was delayed in treated animals to 186h +/- 5 (FF group) and 191 h +/- 6 (-INH group).

A comparison of two techniques for the synchronisation of oestrus in dairy heifers

Seventy-four heifers in four separate breeding groups were allocated into two treatment groups for oestrus synchronisation. Group 1 was given a combination of an initial injection of norgestomet and oestradiol valerate together with a norgestomet ear implant left in place for nine days. Group 2 was given two injections of the synthetic prostaglandin luprostiol 10 days apart. The animals in group 1 were artificially inseminated once 48 hours after the removal of the implant and those in group 2 were inseminated once 72 hours after the second injection of luprostiol. Subsequently any returns were rebred by either AI or natural service. There was no significant difference between the numbers of animals in the two treatment groups which were diagnosed pregnant 33 to 35 days after insemination, although the implant treatment gave a higher overall proportion of pregnancies (70 per cent, 51 per cent). It also gave significantly smaller numbers of 'open' days over the whole of the breeding period. A study of individual animals by progesterone assay and investigation of ovarian structures by real-time ultrasound showed that some of them had unusual progesterone profiles but nevertheless became pregnant. It would appear that a corpus luteum may be responsive to prostaglandins even though it is secreting only a low level of progesterone.

Real-time ultrasonic scanning in sheep: the results of the first year of its application on farms in south-west Scotland

After a two-day period of instruction in the use of a linear real-time ultrasonic scanning machine the results obtained by three operators scanning a variety of types of ewe under different conditions were recorded and compared with the actual lambing results. In the first season an overall accuracy of 95 per cent was achieved for the diagnosis of barren ewes and ewes carrying either one or two or more lambs. However, monitoring the accuracy achieved for the diagnosis of zero, one, two, three or four lambs demonstrated an improvement in expertise with time, the accuracy increasing from below 70 per cent to over 90 per cent. A particular improvement was observed after a comparative session with an experienced operator. Analysis of the figures of accuracy for zero, one, two, three and four lambs highlighted the differences between operators which were less evident if only the results for zero, one or two or more lambs were analysed. These analyses showed that 'newly trained' operators were not at first able to scan successfully. However, after a period of acquaintance with the technique (approximately 500 ewes) and an 'appraisal session' with an expert the accuracy of the operators improved sufficiently to be of commercial value to hill flocks and possibly to low-ground flocks with limited housing.

Fertility of ewes following artificial insemination with semen frozen in pellets or straws, a preliminary report

In two trials involving the artificial insemination of 194 ewes, the fertility of ram semen was examined following freezing, either in pellet form or in straws, and after storage in a chilled state (15 degrees C) for up to 16 hours. Estrus was synchronized in ewes by intravaginal sponge (MAP) treatment for 14 days. At sponge removal 600 IU PMSG was injected and the ewes received two inseminations 50 and 60 hours later. Fertility was assessed at lambing. In trial 1, the mean lambing rate of 52% (16/31) for semen frozen in pellets was higher than 29% (9/31) for semen frozen in straws but this difference was not significant. In trial 2, ewes inseminated with chilled semen and semen frozen in pellets had lambing rates of 83% (44/53) and 55% (44/79) respectively (P<0.001).

Hormonal and histological studies in a 61XXY bull

A Friesian bull with bilateral testicular hypoplasia was diagnosed as having a pure 61XXY karyotype. The bull displayed normal sexual behaviour but was azoospermic. At 17 months, the animal's peripheral plasma androgen levels appeared to be lower than normal, and one testicle removed one month later showed small seminiferous tubules totally lacking in germ cells. The Leydig cell volume of this testis was well within the normal range but the tubule length was rather short. At 33 months of age an increase in peripheral plasma androgen levels was noted. In the remaining testis there had been both a considerable rise in Leydig cell volume and a fall in tubule length. These findings may be explained by the interaction of three factors; the effects of the abnormal karyotype, the increased maturity of the animal at 33 months and the reaction of the remaining testis to unilateral castration.

Tubule length and Leydig cell volume in the normal bull testis

Data are presented on the size, Leydig cell content and seminiferous tubule dimensions of the normal bull testis. A method of estimating total tubule length, requiring only the measurement of testis volume and the number of tubule cross-sections in a unit area is described, and its applicability to the bull established. The average bull testis contains about 5.2 km of tubules.

Meiosis and spermatogenesis in bulls heterozygous for a presumptive 1/29 Robertsonian translocation

Bulls heterozygous for the 1/29 Robertsonian translocation showed normal mating behaviour, semen quality and spermatogenesis. The karyotypes of 90 offspring of one heterozygous bull were consistent with a normal 1:1 segregation of the translocation. There was no difference in overall chiasma frequency at diakinesis between heterozygous and normal bulls, and while a trivalent was noted at diakinesis the chiasma position within the No. 1 arm of the trivalent did not appear to be altered when compared with that found in the normal No. 1 bivalent. An increased frequency of aneuploid secondary spermatocytes at the second meiotic division (M II) was found in the heterozygous bulls, the rate of non-disjuction based on the proportion of hypermodal cells being raised from 2.8% in the normal to 6.4% in the heterozygous animals.

Chromosome banding studies in cattle

A recent advance in the field of cytogenetics has been the ability to stain differentially specific areas or bands on the fixed chromosome. In terms of clinical and paraclinical work C- and G-bands have been of most value to date in allowing precise identification of chromosome homologues even in species such as cattle, where the vast majority of chromosomes are of a similar morphology. These methods have allowed at the gross level of the chromosome the precise identification of a number of Robertsonian translocations and certain aneuploids. In this study 1/29 Robertsonian translocations were found in three separate breeds. Also a 14/20 and a 6/16 Robertsonian translocation were identified as was a 61XXY sterile bull. In the future these techniques will allow the identification of as yet unidentified anomalies in cattle such as reciprocal translocations and paracentric inversions. Since many anomalies have been correlated with such clinical problems as early embryonic death, abortion, congenital anomalies and reduced reproductive efficiency in the mammalia, it is important to use cytogenetics as an additional laboratory aid in such investigations.

A 14/20 Robertsonian translocation in Swiss Simmental cattle

A chromosomal abnormality identified as a 14/20 Robertsonian translocation by measurement and banding studies has been found randomly in several Swiss Simmental cattle. These cases have all been traced back to one ancestral bull. The testicular function of three unselected male offspring, two heterozygotes and one normal was studied. All possessed apparently normal spermatogenesis. In a meiotic study no alteration of overall chiasma counts were found at diakinesis in the heterozygous bulls compared with the normal, while the presence of a trivalent confirmed the diagnosis of a Robertsonian translocation. Also in the heterozygotes a small number of secondary spermatocytes were identified but they were too few to draw any firm conclusions regarding alterations in non disjunction rate.

Arthrogryposis-palatoschisis and a 1/29 translocation in a Charolais herd

The congenital condition of arthrogryposis palatoschisis was found in two closely related Charolais calves and has subsequently been found in a number of other related animals. It would appear from this and earlier reports that the condition is inherited, possibly as an autosomal recessive. A 1/29 Robertsonian translocation was also found in one of the calves and this was inherited from its dam. It is considered that the two conditions are not directly related.