A survey of calf rearing practices in the south-west region of Western Australia

AIMS

To gather data on the calf management and rearing practices of a subset of dairy farmers in the south-west region of Western Australia.

METHODS

A 30-minute face-to-face survey was conducted with dairy cattle producers in the south-west region of Western Australia from April-June 2019 to determine pre-weaning calf rearing practices. Participation was voluntary, using a self-selected subset of dairy farmers registered with a regional extension group. The questionnaire assessed three broad categories: farm demographics, colostrum harvesting and management and calf rearing practices.

RESULTS

The study response rate was 34/140 (24%). The following key areas were identified where there were deviations from recognised best practice: Precalving: no transition diet was fed pre-calving on 4/34 (12%) of farms, and on a further 5/34 (15%) it was fed for less than 3 weeks; mixing of heifers and adult cows in the calving paddocks occurred in 24/34 (70%) of the farms, with 15% (5/34) of the farms using calving induction. During calving 14/34 (41%) of the farms did not disinfect navels of new-born calves in; although 23/34 farmers stated that they collected calves within 6 hours of birth, data on frequency of calf pick up (2/34 did not separate calves and dams and 19/34 picked up only once per day) indicated that on 21/34 farms (62%) the reality was that calves were picked up >12 hours after birth. Colostrum quality was not assessed appropriately on 18/34 (53%) of farms and farmers overestimated how soon after birth it was administered: 23/34 (68%) reported feeding it within 6 hours of calving, despite 62% picking up calves >12 hours after calving. Regarding calf rearing practices, no pain relief before or after dehorning was used by 20/34 (59%) of farms, calf bedding was removed infrequently (<weekly) on 26/35 (76%) of farms and appropriate isolation of sick calves was only reported by 14/34 (41%) of farmers.

CONCLUSION AND CLINICAL RELEVANCE

Although limited by the low response rate, this is the first survey of dairy calf rearing practices in the south-western region of Western Australia. We found evidence of at least one process inconsistent with industry best-practice on 34/140 (24%) of responding farms and all farms had more than one sub-optimal calf rearing practice. This highlights the need to improve calf rearing in this region and identifies key areas of deficiency for further study and extension to producers.

Prevalence of Tritrichomonas foetus in beef bulls slaughtered at two abattoirs in northern Australia

Bovine trichomoniasis, caused by the protozoal parasite Tritrichomonas foetus, is a highly contagious venereal disease characterised by early pregnancy loss, abortion and pyometra. Persistently infected bulls and cows are the primary reservoirs of infection in infected herds. This research investigated the prevalence of T. foetus infection in bulls from properties located across northern Australia and New South Wales. Preputial samples were collected from 606 bulls at slaughter and tested for T. foetus using the VetMAX‐Gold Trich Detection Kit (Thermo Fisher Scientific). The apparent prevalence of T. foetus infection varied between regions, with northern regions in the Northern Territory, Queensland and Western Australia showing a prevalence of 15.4%, 13.8% and 11.4%, respectively. There was some evidence of an association between infection and postcode (P = 0.06) and increasing bull age (P = 0.054). This study confirms that T. foetus infection is likely to be present in many beef breeding herds and contributing to lower than expected reproductive performance, particularly across northern Australia.

A descriptive retrospective study on mortality and involuntary culling in beef and dairy cattle production systems of Western Australia (1981-2018)

Identifying and quantifying the relative frequency of involuntary losses is an essential first step in developing fit-for-purpose herd health programmes. The objective of this study was to provide an estimate of the relative frequency of reasons for mortality among south-west Western Australian beef and dairy cattle, based on necropsy findings from a university-based veterinary pathology referral centre over 38 years. A total of 904 cattle were submitted for postmortem examination throughout the study period. Gastrointestinal, cardiopulmonary and reproductive conditions were the most common causes of mortality in cattle submitted for necropsy at Murdoch University for the period 1981-2018. In dairy cattle, the common problems were gastrointestinal (bloat, abomasal displacements) 18% (59/320), cardiovascular (traumatic reticulo-pericarditis) 9% (30/320) and respiratory conditions (pneumonia) 8% (27/320). In beef cattle, the most common conditions were gastrointestinal (bloat, rumen acidosis) 11% (39/358), reproductive (metritis) 11% (38/358), cardiovascular (traumatic reticulo-pericarditis) 7% (25/358), respiratory (pneumonia) 7% (24/358), lameness (fractures) 6%, (21/358) and hepatobiliary conditions (blue-green algae poisoning, hepatotoxicity) 6% (21/358). Selection bias and missing data were potential confounders in this study. Although necropsy investigations provide useful information on animal mortalities and avenues for future herd health programmes, there is a need to standardise data capture methods and disease definition criteria, and conduct more detailed recording of data both at the farm level and at necropsy diagnostic centres.

A Bayesian latent class model to estimate the accuracy of pregnancy diagnosis by transrectal ultrasonography and laboratory detection of pregnancy-associated glycoproteins in dairy cows

Accurate diagnosis of pregnancy is an essential component of an effective reproductive management plan for dairy cattle. Indirect methods of pregnancy detection can be performed soon after breeding and offer an advantage over traditional direct methods in not requiring an experienced veterinarian and having potential for automation. The objective of this study was to estimate the sensitivity and specificity of pregnancy-associated glycoprotein (PAG) detection ELISA and transrectal ultrasound (TRUS) in dairy cows of South Africa using a Bayesian latent class approach. Commercial dairy cattle from the five important dairy regions in South Africa were enrolled in a short-term prospective cohort study. Cattle were examined at 28-35days after artificial insemination (AI) and then followed up 14days later. At both sampling times, TRUS was performed to detect pregnancy and commercially available PAG detection ELISAs were performed on collected serum and milk. A total of 1236 cows were sampled and 1006 had complete test information for use in the Bayesian latent class model. The estimated sensitivity (95% probability interval) and specificity for PAG detection serum ELISA were 99.4% (98.5, 99.9) and 97.4% (94.7, 99.2), respectively. The estimated sensitivity and specificity for PAG detection milk ELISA were 99.2% (98.2, 99.8) and 93.4% (89.7, 96.1), respectively. Sensitivity of veterinarian performed TRUS at 28-35days post-AI varied between 77.8% and 90.5% and specificity varied between 94.7% and 99.8%. In summary, indirect detection of pregnancy using PAG ELISA is an accurate method for use in dairy cattle. The method is descriptively more sensitive than veterinarian-performed TRUS and therefore could be an economically viable addition to a reproductive management plan.

Herd-level risk factors for Campylobacter fetus infection, Brucella seropositivity and within-herd seroprevalence of brucellosis in cattle in northern Nigeria

Brucellosis and campylobacteriosis are economically important diseases affecting bovine reproductive efficiency in Nigeria. A questionnaire-based survey was conducted in 271 cattle herds in Adamawa, Kaduna and Kano states of northern Nigeria using multistage cluster sampling. Serum from 4745 mature animals was tested for Brucella antibodies using the Rose-Bengal plate test and positives were confirmed in series-testing protocol using competitive enzyme-linked immunosorbent assay. Preputial scrapings from 602 bulls were tested using culture and identification for Campylobacter fetus. For each disease, a herd was classified as positive if one or more animals tested positive. For each herd, information on potential managemental and environmental risk factors was collected through a questionnaire administered during an interview with the manager, owner or herdsman. Multiple logistic regression models were used to model the odds of herd infection for each disease. A zero-inflated Poisson model was used to model the count of Brucella-positive animals within herds, with the number tested as an exposure variable. The presence of small ruminants (sheep and/or goats) on the same farm, and buying-in of >3 new animals in the previous year or failure to practice quarantine were associated with increased odds of herd-level campylobacteriosis and brucellosis, as well as increased within-herd counts of Brucella-positive animals. In addition, high rainfall, initial acquisition of animals from markets, practice of gynaecological examination and failure to practice herd prophylactic measures were positively associated with the odds of C. fetus infection in the herd. Herd size of >15, pastoral management system and presence of handling facility on the farm were associated with increased odds, and gynaecological examination with reduced odds of herd-level Brucella seropositivity. Furthermore, the zero-inflated Poisson model showed that borrowing or sharing of bulls was associated with higher counts, and provision of mineral supplement with lower counts of Brucella-positive cattle within herds. Identification of risk factors for bovine campylobacteriosis and brucellosis can help to identify appropriate control measures, and the use of zero-inflated count model can provide more specific information on these risk factors.

Bull breeding soundness evaluation in Southern Africa

The motivation for and process leading up to the publication of a new bull breeding soundness certification standard endorsed by the South African Veterinary Association is described. The veterinary certificate of bull breeding soundness and explanatory notes and minimum standards are shown. The first component of the certificate is a declaration by the veterinarian that the bull complies with the minimum standards set for examinations for the selected purpose, these being for use as a natural service sire, as a donor of semen for distribution, and for insurance purposes. This is followed by the details of the bull and owner, and a list of the recommended examinations and tests for the bull with provision for which were performed. Certificates are available in book form with the explanatory notes and minimum standards on the reverse, and a carbon copy which remains in the book. The clarity and ease of completion of the document are regarded as being positive features. Bulls are either classified as breeding sound or not, with no actual parameters indicated on the document and no certificate issued for those which do not meet the set criteria. Contact details of the parties involved are shown on the certificate to allow for communication as a means of avoiding disputes.

Failure of luteolysis leads to prolonged gestation in a bitch: a case report

A healthy, 5-yr-old rough collie bitch exhibited prolonged gestation, characterized by intrauterine fetal death and plasma progesterone concentrations (PPC) above 6 nmol/L/d until Day 65 or 66 of cytologic diestrus, which then only dropped following treatment with dinoprost tromethamine. The bitch showed no signs of parturition prior to laparotomy and hysterotomy on Day 63, which revealed 5 corpora lutea (CL) on the left ovary and 1 on the right ovary; 5 full-term, dead conceptuses without obvious autolysis but with 4 of the 5 placentas detached; and a tightly closed cervix. All conceptuses were in the left uterine horn. Treatment with dinoprost tromethamine was initiated 1 d after hysterotomy and was continued for IO d (120 microg/kg twice daily for a total dose of 240 microg kg/d). The discharge of lochia through the cervix and lactation started 3 d after the onset of treatment. Plasma progesterone concentration was 14.4, 16.2 and 1.6 nmol/L/d on the day of hysterotomy and at 1 and 3 d after the onset of prostaglandin therapy, respectively. The reason for the failure of luteolysis to occur is not known.

Absence of lumpy skin disease virus in semen of vaccinated bulls following vaccination and subsequent experimental infection

Twelve serologically negative bulls were used, six were vaccinated with a modified live LSD vaccine and six unvaccinated. All were then experimentally infected with a virulent field strain of LSDV. No clinical abnormality was detected following vaccination, and mild clinical signs were seen in four vaccinated bulls following challenge. Virus was not found in semen of vaccinated bulls. Two of the unvaccinated bulls developed severe LSD and four showed mild symptoms, all excreted the virus in the semen following challenge. This study confirmed the ability of LSD vaccination to prevent the excretion of LSDV in semen of vaccinated bulls.

Elimination of toxicity and enhanced detection of lumpy skin disease virus on cell culture from experimentally infected bovine semen samples

Lumpy skin disease virus (LSDV), a poxvirus of the genus Capripoxvirus, is shed in the semen of infected bulls. The screening of semen for infectious virus requires a sensitive diagnostic method. The isolation of the virus on cell cultures and/or the polymerase chain reaction (PCR) are sensitive diagnostic tests which may be used to screen semen for LSD viral DNA prior to artificial insemination. Although cell culture detects infectious virus and is a sensitive method, there are major difficulties in using this method due to the toxic effect of semen on the cells. The aim of this study was to find a method that decreases the toxic effect of semen and enhances the isolation of LSDV on cell culture. Semen samples from LSDV sero-negative bulls were collected and infected with a field isolate of LSDV, strain V248/93, with a titre of 6.5 log TCID50. The semen samples were treated with one of four different methods: centrifugation, serial dilution, filtration and chemical treatment with kaolin. The samples subjected to centrifugation, serial dilution and filtration were supplemented with gentamycin. Semen toxicity on cell cultures was eliminated when supernatants of semen samples centrifuged at 2000 rpm for 1, 3 and 5 min and serially diluted were used to inoculate confluent monolayer bovine dermis cells. The toxicity recorded when the pellet fractions of semen samples centrifuged for 5 min at 2000 rpm was comparable to results obtained from serially diluted samples supplemented with gentamycin. Filtration and kaolin treatment of semen samples did not remove the toxic effect.

Excretion of lumpy skin disease virus in bull semen

This work was done to establish the incidence and duration of excretion of lumpy skin disease virus (LSDV) in semen of experimentally infected susceptible bulls. Six serologically negative bulls 11-20 months of age were experimentally infected with a virulent field isolate (strain V248/93) of LSDV. Animals were observed for the development of clinical signs, blood was collected until day 90 after infection, and semen was collected every second day until day 18, then twice a week till day 63 and twice a month until three consecutive samples were negative when tested for LSDV by polymerase chain reaction (PCR). An aliquot of each sample which tested positive using PCR was inoculated onto cell monolayers for the recovery of virus. Two bulls developed severe lumpy skin disease (LSD), two bulls showed mild signs and two bulls showed a transient fever only. Multiple samples were positive on PCR from both of the severely affected bulls and one of the mildly affected bulls; between days 10 and 159, days 8 and 132, and days 10 and 21 respectively. Only one sample from each of the other three bulls was positive on PCR. Virus was only isolated from two samples from one of the severely affected bulls and from five semen samples from the other. This study confirmed the excretion of LSDV in bovine semen for prolonged periods, even when obvious clinical signs of the disease were no longer apparent.

Collection of preputial material by scraping and aspiration for the diagnosis of Tritrichomonas foetus in bulls

Two trials were carried out to assess the diagnostic sensitivity and practicability of preputial scraping as a method of collecting preputial material from bulls infected with Tritrichomonas foetus. In the 1st trial, preputial material was collected by simultaneous scraping and aspiration from 3 infected and 1 uninfected bull 10 times over a 5-week period. In the 2nd trial, samples from 5 infected bulls were collected by both sheath washing and scraping on 6 occasions, while 8 uninfected animals were sampled 3 times. Samples were cultured using a modified Trichomonas culture medium (Oxoid). In the first trial, 29 of 30 samples from infected bulls were found to be positive. In the second trial, 83 % of samples collected by both methods tested positive. In neither trial were any samples from the control bulls found to be positive. Scraping was found to be quick and safe, and offered advantages over preputial washing in that urine contamination was easily avoided, samples were smaller and more concentrated and contamination was reduced. It may, however, be subject to greater operator variability than sheath washing. It is concluded that preputial scraping is as effective as washing and represents a suitable alternative for the collection of material for direct examination and culture of Tritrichomonas foetus.

Ultrasound-guided injection of contrast medium into the crus penis for diagnosis of erection failure in bulls

The objectives of this study were to demonstrate the ability to cannulate the crurae of the bull's penis under ultrasound guidance, to demonstrate contrast medium injected by this route in the distal penis, and to confirm the technique to be safe and repeatable. Five adult bulls with normal serving ability were used, one being subjected to the procedure twice. The procedure was performed with the bulls under general anesthesia and in lateral recumbency. A spinal needle was passed through the skin and into the crus penis under ultrasound guidance and two syringes containing an iodine-based contrast medium were connected to it. Stimulation using an electro-ejaculator with a rectal probe was initiated, and when the penis started developing an erection, 50-100 ml of contrast medium was injected. Lateral and ventro-dorsal radiographs were taken of the extended penis during, and at intervals after, injection. After a rest period of 5 min, clearance of the contrast medium was confinned and the procedure was repeated on the other crus penis. Each case therefore, contained two attempts. Successful cannulation of the crus penis was confirmed by observing indentation of its fibrous wall by the needle, free flow of blood, lack of resistance to the injection of air, which could be seen in the crus, and fluctuation of resistance to injection in synchrony with the pulsation of the electroejaculator. Contrast medium was demonstrated in the mid or distal portion of the penis in all six cases, or on 9 of the 12 attempts. Attainment of penile erection, a larger volume of contrast medium, and the order of cannulation all enhanced flow of contrast medium to the distal portion of the penis, with the first crus giving better results. On one occasion the needle worked out of the crus penis during stimulation, resulting in injection of contrast medium into the corpus spongiosum penis. All bulls recovered uneventfully and returned to normal serving ability. It is concluded that ultrasound-guided cannulation of the crus penis is a safe and successful method for the injection of contrast medium for contrast studies of the penis, and is less invasive than the surgical method.

Hysterotomy by a colpotomy approach for treatment of foetal mummification in a cow

A 7-year-old Brahman cow was diagnosed as suffering from chronic foetal mummification of unknown aetiology, concurrent cystic ovarian disease, prolapse of the 2nd cervical ring and chronic cervicitis. Repeated treatment with prostaglandin F2alpha and oestrogen failed to resolve the mummification. A hysterotomy was performed via an incision in the dorsolateral vaginal wall. Good exposure of the uterine horn was achieved and mild post-operative complications were observed. Colpotomy can be regarded as an alternative surgical approach to the moderately enlarged bovine uterus.