How herd fertility checks revealed venereal disease
How herd fertility checks revealed venereal disease
By Marianne Curtis
TO the casual observer, Hereford x Friesian suckler cows appeared healthy on Compton Farm, near Pewsey. But Bruce Waight was disappointed with a conception rate of 80%, which was later found to be caused by campylobacter.
Mr Waight runs 280 suckler cows on the 680ha (1700 acre) mixed unit on the northern edge of Salisbury Plain. Cropped with 400ha (1000 acres) of cereals and 280ha (700 acres) of permanent grazing, the farm is rented from the Army. Grazing of some areas is occasionally restricted, when military exercises are underway and to comply with wildlife conservation requirements.
The herd calves in two blocks – 160 cows in spring and the remaining 120 in autumn. All calves are sold as stores at eight months old.
Keith Cutler, of Salisbury-based Endell Vet Group, became involved with the herd four years ago. "Although I had visited previously for emergencies, it was not until this point I took over routine work. Each farm is different, so it is important to fully understand a unit and its objectives before recommending disease prevention and treatment strategies.
"For this herd, I began by taking blood samples from a number of cows to check for diseases linked with infertility. Results showed campylobacter was present in the herd and the presence of bovine viral diarrhoea antibodies indicated cattle had also been exposed to this disease."
Aware of the high cost of tackling both diseases at the same time, Mr Cutler prioritised. "Campy-lobacter can be a devastating disease, particularly when it enters a naïve herd or group of animals, such as bulling heifers, which have not developed any resistance to it. In one herd I treated on a different farm, a group of naïve cows put to an infected bull had a conception rate of only 17%, compared with 85% for uninfected cows.
"So we decided to tackle campylobacter first because it was likely to be having the biggest impact on Mr Waights herd fertility."
Mr Cutler suggested three ways of dealing with the disease, which he estimates is present in 25-30% of suckler herds and on the increase.
The first option was to live with campylobacter. "Cows will develop immunity to it, following a disease challenge, but this is unreliable. In this herd, fertility was poorer than hoped so this route was not taken."
As campylobacter is a venereal disease – transmitted during service from either bull to cow or cow to bull, but not between cows – option two involved using AI for 2-3 years. However, Mr Waight was not enthusiastic about this. "We aim for a relatively low labour system and I wasnt keen on the idea of having to watch for bullers."
The final option, which suited his system best, was to change natural service management, explains Mr Cutler. "Hired bulls are a particular risk and were being used in Mr Waights herd."
But now Mr Waight only buys virgin bulls. As an extra precaution, when a new bull enters the farm, Mr Cutler gives its sheath an antibiotic wash to remove any infection.
Cows were also split into two separate groups before service – a clean group and dirty group. Initially, the clean group consisted of virgin bulling heifers. All older cows formed the dirty group, because they could have potentially been exposed to the disease from hired bulls, says Mr Cutler.
"Four years on, as clean replacements have come into the herd, 70 cows remain in the dirty group. In a year or two these will disappear as culls, leaving the whole herd clean," according to Mr Waight.
Yellow button
Although dirty and clean cows may be grouped together at calving for convenience, it is critical they are allocated to groups before bulling, explains Mr Waight. "Clean cows are identified with a yellow button tag and conventional ear tag numbers provide an additional check. Cows are separated after calving."
The system would break down if dirty cows escaped into clean cow grazing areas during bulling, so the two herds are managed on different parts of the farm during this period, says Mr Cutler. "It is also vital to keep neighbours cattle out of fields, as they may pose an infection risk."
Careful management of cows during the bulling period has improved conception rates from 80% to 94% and there have been other advantages, says Mr Waight. "Calves are usually sold for £300/head, so more calves means a higher return. We also have fewer empty cows slipping into the next calving block."
With campylobacter under control, attentions are now turning to BVD, he adds. "Currently, heifers entering the herd are vaccinated twice. Then cows receive an annual booster." *
Advice from vet Keith Cutler (right) on campylobacter management has improved conception rates in Bruce Waights suckler herd.
CAMPYLOBACTER
• Venereal disease.
• 25-30% of beef herds infected.
• Poor fertility in naive animals.