Acorn calves, calves displaying a clinical syndrome of skeletal abnormalities including misshapen heads that often give a domed appearance, spinal abnormalities such as kyphosis and shortened and deformed front legs, have been reported sporadically in spring calving herds in south eastern Australia since 1965.
In 2003, 2004, and 2005 there was an extended outbreak that allowed the condition to be investigated by survey, herd tests and histopathology.
This investigation involved district veterinarians in several districts, NSW Department of Primary Industry (as it was then) veterinarians, Victorian Department of Primary Industry Veterinarians and Sydney University pathologists. It was supported by NSW Farmers and State Council. The Acorn Calf Project is an example of cross departmental cooperation that drew on varied expertise across the field of Animal Health.
It resulted in a paper 'An extended outbreak of congenital chondrodysplasia in calves in South East Australia' (JG Cave, PJMcLaren, SJ Whittaker, L Rast, A Stephens and EM Parker AVJ Vol 86 No4 2008) and an ongoing PhD investigation at Sydney University.
Our Board has an ongoing interest in these chondrodysplastic calves and actively monitors calf abnormalities that are reported to us.
In September 2009 a producer reported an Acorn calf from a spring calving herd of 40 hereford cows 5-8 years old in the Wantigong Valley near Holbrook. He believed that he had had another born dead a week previously and was now 2 weeks into his calving period.
I visited the property to assess the calf for the characteristic deformities of an acorn calf and collect some history if it fitted the clinical syndrome. We had not had acorn calves reported from this property or that area previously.
The Wantigong Valley is one of the better and more reliable pastoral areas in the Board.
The mob was one of several 40 head cow mobs that were run separately year round on the property. Bulls were used across several mobs, genetic aetiology seemed less likely. No other mobs reported deformed calves.
The mobs were run on improved pasture across the property and the affected mob had been set stocked since joining on a paddock that had not recovered from silage being cut in 2008. The silage was cut from the paddock then the Spring failed and the pasture did not recover. The paddock remained less productive than the other pastures used by the other mobs.
The paddock had had 125kg/ha single super applied in 2008 and 300kg/ha single super applied in 2009.The mob had only been moved off this paddock to calve in August 2009.
The calf was able to stand and nurse but was not very mobile although able to walk. It showed the typical slightly domed head, shortened and bowed front legs and an arched spine.
The calf died 2 weeks later but was not autopsied. No other acorn calves were reported from this property.
This case was a little unusual in that it occurred on flatter improved country. Consistent findings in acorn calf cases are that the dams have experienced hot dry seasonal conditions early in pregnancy and often have also run in poorer hill country. These cows did experience a poor season and were run under nutritional stress throughout much of pregnancy compared to other mobs on the same property.
At present Acorn calves are classified on the basis of a clinical syndrome of the presence of common chondrodystrophic skeletal abnormalities with varying degrees of severity and a common history. As long as the aetiology remains obscure there will be a risk that some calves are classed as Acorns that had resulted from differing causes during pregnancy.