CASE NOTES
WET PASTURE AND FAILURE OF RUMEN DEVELOPMENT
Matt Ball, Senior District Veterinarian Lismore
Posted Flock & Herd July 2012
Introduction
In the summer of 2012 a number of Tweed-Lismore beef producers contacted the Lismore District Veterinarian of the North Coast Livestock Health and Pest Authority (LHPA) about 'poor doing' calves.
This case study summarises the findings from investigations that occurred on properties reporting similar disease signs and highlights the ability of the LHPA system to identify local syndromes and changes to the pattern of disease in its local area.
HISTORY AND CLINICAL EXAMINATION
Between January and February 2012 owners of three independent beef herds; one at Caniaba, one at Larnook and one at Rosebank; all reported 'poor doing' beef calves. The farms were all breeding herds with enterprises that involved suckling calves being sold directly off their mothers before weaning. Typically no feed supplementation was given to the calves. In each herd about 2-3% of calves were reported to be growing poorly. Consistent history and clinical findings from the three farms included:
Calves between 4 months-8 months of age were smaller than their peers. They had poor growth, despite mothers seeming to have adequate milk production. Farmers expressed surprise that calves were doing badly in such a 'good season'. There was an intermittent swollen appearance to the calves, mainly on left hand side of the abdomen. Some of the calves had a light coloured mild scour. All had been given preventative treatments against internal parasites. No fever or other sign of disease was observed in two examined calves. On one farm it was reported that when an affected calf was locked into the yards for a day the swelling in the abdomen was noticeably decreased.
LABORATORY TESTING
Three calves from two different properties were tested for pestivirus. All were negative for pestivirus antigen on hair testing. One scouring calf was tested for internal parasites and infectious causes of diarrhoea. This calf had a low worm and coccidia egg count. An 'in house' calf scour test kit was negative for E.coli, rotavirus, coronavirus and cryptococcus. The calf also had negative cultures for Yersinia and Salmonellosis.
NECROPSY
A necropsy was performed on two calves approximately six months in age and both from different properties. The necropsies had similar findings: poor body condition and small in size, ascites, scant numbers of haemonchus visible in abomasums, no evidence of milk ingestion in abomasums, rumen filled with large quantity of heavy wet grass, much of which was undigested, papillae of rumen mucosa not developed, no other significant findings.
Discussion
The farms that were investigated all had experienced a high quantity of lush wet pasture for a number of months. It is assumed that the signs of disease occurred due to the following series of events:
Affected calves had taken to ingesting significant quantities of wet pasture from a young age. This may have been because their mother's milk was inadequate or simply from natural curiosity and the abundance of easy to eat moist feed. Once they began ingesting green feed they suckled less and less to a point of 'self weaning'. The moist nature of the pasture did not stimulate early rumen development as occurs in orphaned beef calves in a drier environment. The calves became stuck in a weaned state but were unable to harness adequate energy or protein from the feed they were ingesting.
Preventative advice given to the farmers was to identify calves that may be affected as early as possible and offer them dry feed of high particle size to stimulate rumen development. A decision would need to be made as to whether it would be justified to keep these calves on a concentrate supplementary feeding plan. Alternatively, various forms of creep feeding were discussed to consider implementation to the whole herd.
Feedback from one farm in late March 2012 suggested that the feeding of dry feed in addition to the calves staying on wet pasture had helped affected younger calves and prevented further cases of ill-thrift. Older affected calves have stayed small and are unable to meet the targets that their peers will reach.
NSW district veterinarians are able to monitor the changes in disease in their region between seasons and years. This local knowledge is invaluable to an effective surveillance system.