Myophosphorylase deficiency (glycogen storage disease Type V) in a herd of Charolais cattle in New Zealand: Confirmation by PCR-RFLP testing

AIM: To describe a disease of muscle in Charolais calves and confirm the putative diagnosis of inherited myophosphorylase deficiency.

METHODS: Variously stained paraffin sections of muscle prepared from affected calves were used to describe the lesions. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test was developed and applied to affected calves, their sires, dams and other individuals.

RESULTS: The lesions were those of rhabdomyolysis of skeletal muscles and sub-sarcolemmal spaces in normal fibres. The PCR-RFLP test confirmed the expected mutation for phosphorylase deficiency of Charolais cattle in two affected calves. In addition, sires, dams and other closely-related individuals of four affected calves tested as heterozygous for the mutation. Other apparently unrelated animals also tested as heterozygous.

CONCLUSIONS: The diagnosis of myophosphorylase deficiency was confirmed. The PCR-RFLP test is suitable for use in controlling this recessively-inherited disorder as it can diagnose heterozygous individuals that are otherwise clinically normal.     

Three cases of a presumptive atypical myopathy in New Zealand horses

CASE HISTORY: Three weanling Thoroughbred fillies were presented during autumn with depression, muscle rigidity and, in one case, colic symptoms and cardiovascular shock.

CLINICAL FINDINGS: All fillies had abnormal physical examinations that included elevated heart rates and respiratory rates coupled with muscle rigidity through the back and rump. Biochemistry revealed markedly elevated creatinine kinase and aspartate aminotransferase which indicated a myopathy.

DIAGNOSIS AND TREATMENT: All three horses were diagnosed with presumptive equine atypical myopathy. The horses received supportive therapy as per the literature available at the time regarding this condition; two responded to supportive therapy and survived, and one was euthanased due to a rapid deterioration in clinical status.

PATHOLOGICAL FINDINGS: Following post mortem of one case, histology of the trapezius muscle demonstrated an acute, severe myofibre degeneration.

CLINICAL RELEVANCE: Atypical myopathy and a very similar disorder termed seasonal pasture myopathy in North America are potentially fatal, pasture-related syndromes that have been described in Europe and America but have not been previously described in New Zealand. This report describes three presumptive cases of this unique syndrome in New Zealand for the first time; it outlines the characteristics of the condition; and includes recently published information regarding diagnosis and treatment.     

Treatment and outcome of chronic septic tenosynovitis in three horses

Three horses were presented for treatment of chronic infections of the digital flexor tendon sheath. Clinical signs included severe lameness, and heat, pain and swelling of the digital flexor tendon sheath. The horses were treated with surgical lavage of the tendon sheath, systemic and local antibiotics, and analgesics. In each case, resolution of the lameness occurred over weeks to months. Only one horse returned to athletic activity, while the other two became comfortable at pasture. Response to treatment in cases of chronic tenosynovitis may not be as rapid or complete as that reported for acute tendon sheath infections.     

Understanding foot-and-mouth disease virus transmission biology: identification of the indicators of infectiousness

The control of foot-and-mouth disease virus (FMDV) outbreaks in non-endemic countries relies on the rapid detection and removal of infected animals. In this paper we use the observed relationship between the onset of clinical signs and direct contact transmission of FMDV to identify predictors for the onset of clinical signs and identify possible approaches to preclinical screening in the field. Threshold levels for various virological and immunological variables were determined using Receiver Operating Characteristic (ROC) curve analysis and then tested using generalized linear mixed models to determine their ability to predict the onset of clinical signs. In addition, concordance statistics between qualitative real time PCR test results and virus isolation results were evaluated. For the majority of animals (71%), the onset of clinical signs occurred 3–4 days post infection. The onset of clinical signs was associated with high levels of virus in the blood, oropharyngeal fluid and nasal fluid. Virus is first detectable in the oropharyngeal fluid, but detection of virus in the blood and nasal fluid may also be good candidates for preclinical indicators. Detection of virus in the air was also significantly associated with transmission. This study is the first to identify statistically significant indicators of infectiousness for FMDV at defined time periods during disease progression in a natural host species. Identifying factors associated with infectiousness will advance our understanding of transmission mechanisms and refine intra-herd and inter-herd disease transmission models.     

Role of Luteinizing Hormone in Primiparous Sow Responses to Split Weaning

In 45 primiparous sows, we examined endocrine, ovarian and reproductive responses to split-weaning or five injections per day of 800 ng GnRH from 18 to 21 days of lactation. There was no effect of treatment on absolute or changes in sow weight or backfat depth during lactation. Average piglet growth rates were similar among treatments except that piglets suckling split-weaned sows grew faster (p < 0.05) during days 18–21. On day 18, mean plasma LH concentrations and LH pulse frequency remained relatively stable in conventionally weaned sows but increased (p < 0.01) in response to split-weaning and GnRH. Prior to weaning on day 21, mean plasma LH concentrations remained elevated in GnRH-treated sows but had returned to control levels in split weaned sows. There was no treatment effect on preweaning LH pulse frequency noted on day 21. Weaning was associated with an increase in plasma LH concentrations in all the treatment groups. Mean plasma IGF-I remained relatively constant in conventionally weaned and GnRH sows, decreased in response to split weaning on day 18 (p < 0.02), but were elevated (p < 0.03) in split wean sows on day 21. On the day after weaning, split wean sows had more (p < 0.04) ovarian follicles ≥3 mm than conventionally weaned sows, with GnRH sows being intermediate. The wean-to-oestrus interval was reduced in split-wean sows compared with those conventionally weaned (p < 0.01), with GnRH sows being intermediate. There was no effect of treatment on ovulation rates, numbers of embryos, or embryonic survival rates. These data indicate that split-weaning of litters results in a more rapid return to oestrus after weaning and that this effect is associated with a transient acute increase in circulating gonadotrophins and earlier resumption of ovarian follicular development.     

Validation of the acute electroencephalographic responses of calves to noxious stimulus with scoop dehorning

AIM: To validate use of the electroencephalogram (EEG) and a minimal anaesthesia model for assessment of noxious sensory input caused by scoop dehorning of calves. METHODS: Twenty Friesian heifers weighing 125-178 kg were maintained under light general anaesthesia using halothane and an established protocol (minimal anaesthesia model). They were then dehorned using a scoop dehorner either with (DH+LA) or without (DH) a lignocaine ring block, and changes in the EEG and electrocardiogram (ECG) recorded. Median frequency (F50), 95% spectral edge frequency (F95) and total power (Ptot) were derived from the EEG data. RESULTS: There were significant increases in the F50 (p<0.01) and F95 (p<0.01), and a decrease in Ptot (p<0.01) following dehorning in the DH group, but there were no changes in the DH+LA group. Transient bradycardia in the first 75 sec following dehorning was recorded in the DH group compared with both pre-treatment values in the same group and with the DH+LA group (p<0.001). Tachycardia was evident by 15 min after dehorning in the DH but not the DH+LA group. CONCLUSIONS: The results validate use of the EEG and a minimal anaesthesia model for assessment of noxious sensory inputs in cattle.     

Accelerated recurrent selection

In Accelerated Recurrent Selection (ARS) schemes, selection is based on the predicted performance of progeny families, estimated as the average of the parental families. These schemes can halve cycle time compared to simple recurrent selection methods. They also have a lower requirement for evaluation of families in yield trials, although they do require more seed production. ARS therefore provides options in cycle time, effective population size, response to selection and cost which have not been available before. Example schemes are compared by computer simulation with truncation selection and with optimal family selection, where contributions of families to the next generation are optimised to give the maximum response to selection at a specified effective population size. In many circumstances, ARS schemes compare favourably. Difficulties in combining estimates of selection intensity and of effective population size when comparing the merits of different breeding schemes are discussed. It is suggested that unless one is interested in response to selection over periods greater than 50 years, the weight given to effective population size in ranking different schemes should be small.