Epidemiological studies of bovine spumavirus

Bovine spumavirus (BSV) infection is shown to be endemic in some herds in north Queensland. The virus was readily isolated from leucocytes of the majority of mature cattle which were BSV antibody positive (BSV reactors) in the agar gel precipitin test (AGPT). Calves born to dams which were BSV reactors showed no BSV antibody or circulatory leucocyte-associated BSV (CLAB) at birth, but became BSV reactors following ingestion of colostrum, and maintained such evidence of passive immunity until 3-5 months of age. Experimental infection of dams with BSV at 5-7 months of gestation did not cause foetal infection. In groups of young animals at pasture, segregated by age and sex, no evidence of BSV infection occurred, following loss of passive immunity, until 18-24 months of age. At this time, occasional members of some groups (both male and female) became BSV reactors and showed CLAB. At approximately 24 months old, following mixing in groups with older cows, and single-sire mating, 34% of heifers became BSV reactors within 10 weeks. A herd survey indicated 85% of 2-3-year-old cows to be BSV reactors; thereafter, the percentage of reactors declined gradually with increasing age. Using BSV grown in cell culture, transmission of infection by throat spray was the most successful route, 7 of 7 (100%) of susceptible cattle becoming BSV reactors within 8 weeks of spraying. Using the intravenous route, only 2 of 5 (40%) susceptible cattle became BSV reactors, and swabbing of cell culture virus into the prepuce or vagina did not result in infection of 4 BSV-susceptible animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Cattle temperaments in extensive beef herds in northern Queensland. 2. Effect of temperament on carcass and meat quality

The effects on carcass bruising and muscle properties of the temperament scores of 170 bullocks and 240 cows (Brahman cross and Shorthorn) from 2 properties in northern Queensland were studied. Temperaments were scored by rating their behaviours when the cattle were handled in a crush and pound. High scores indicate poor temperaments. The bullocks and cows were respectively transported 740 and 1155 km to abattoirs and slaughtered 5-7 days after mustering. In both experiments, the estimated bruise trim per carcass increased by approximately 0.3 kg per unit increase in movement score for both temperament tests. Cattle with high temperament scores had more bruising along the back and around the tuber coxae and tuber ischii. Muscle samples from cattle with higher temperament scores tended to have higher mean initial yield and peak force shear values, thus indicating that their meat may have been less tender. Neither ultimate pH nor sarcomere length was related to temperament score.

The prevalence of epitheliogenesis imperfecta in Sahiwal cattle and their crosses in a north Queensland beef herd

Epitheliogenesis imperfecta (EI) has been diagnosed in calves on a north Queensland beef cattle research station. There are five Bos indicus cross, inter se mated breed groups on the station: 1/2 Brahman, 3/4 Brahman, 1/2 Sahiwal, 3/4 Sahiwal and High Grade Sahiwal. The disease was confined to the three Sahiwal breed groups and caused calf losses over seven years from 1978 of 0.2%, 3.4% and 1.0% in the 1/2, 3/4 and High Grade groups respectively. The Sahiwal breed was identified as the origin of the gene responsible for the disease. The source of the gene within the Sahiwal breed was investigated, and several ancestors were identified as almost certainly being heterozygotes. Analyses of relationships of affected and non-affected calves to the 10 Sahiwals that were originally imported into Australia identified the one that was most likely the source of the El gene.

Temperament and bruising of Bos indicus cross cattle

This experiment investigated the temperaments of 232 Bos indicus cross steers and the relationship between temperament and bruising in bovine carcasses. The temperament of each animal was assessed while held in a race by rating the vigour of movement and the degree of audible respiration when handled about the head and shoulders. These scores and scores for other behaviours were combined to form a temperament score for each animal. The five groups of steers used varied significantly in temperament (P< 0.01); this was considered to be primarily a function of their previous handling experience. There was a significant negative correlation between temperament score and liveweight (P < 0.01). In this group of relatively quiet steers no significant relationship between temperament and carcass bruising at slaughter was found.