THE DIFFERENCE between conception rates when mineral status is right or wrong could be as much as 40%, believes Dave Morgan, who runs 140 sucklers in Herefordshire.
He has seen the effect that poor mineral status can have with cows showing signs of anoestrous and returning to service at Pennlan Farms, Peterchurch.
“Hereford is historically known for being low in cobalt, copper and selenium and when left untreated this can reduce conception rates to as low as 50%,” he explains. But when cows are receiving adequate minerals conception should be nearer 90%.
The 405ha (1000-acre) holding is spread over a 15-mile radius and some areas farmed are worse affected than others. “We’ve mineral tested for some years now, as there are hotspots on the farm which can be particularly problematic.”
The herd is run on an autumn and spring calving system. Two-thirds of the herd calve in the autumn, a time which Mr Morgan believes fertility is particularly affected by mineral status. “As days become shorter, it’s also harder to spot those not served by the bull or those who return.
“Furthermore, cows at this time of year are under greater pressure to get back in calf because they rely on their own reserves more than in spring.” This can be particularly hard for Continental-type cows, which can struggle to keep flesh on, he adds.
The herd has supplemented with selenium injections for many years, but last year Mr Morgan and vet Matthew Pugh, of Belmont Vet Centre, tested for copper deficiency. “Cows were still returning to service, so we tested calving cows whose body condition was poor and were not performing as well as they should be,” says Mr Pugh.
“Average readings for copper should be between 9 and 19, but these cows were coming back with readings of 4.17.” Cows were simply mobilising too much body fat, he explains.
As well as showing incredibly low samples of copper, energy status was low as a result of variable quality silage. “Silage was offered at all times, but intakes were not high, indicating poor palatability,” adds Mr Pugh.
To combat poor forage quality, Mr Morgan has since ceased pit silage and returned to big bale silage, which he believes results in a more energy dense, palatable ration.
Regarding the best possible treatment method for copper deficiency, Mr Morgan felt feeding general purpose minerals would not be the best route to take. It’s hard to ensure adequate intakes when offering minerals ad-lib. Mr Pugh adds that in this instance it would take too long for copper levels to return to a required level from general purpose mineral licks.
Boluses were an option, but these would have to be repeated every six months and Mr Morgan felt this would not be an easy option for the herd. Although boluses have been successful on many farms, Mr Pugh adds that copper from them can become bound up with other minerals. “There is also the issue of possible regurgitation to consider.”
It was decided a yearly injection of copper substance would be given to provide immediate availability to stock, he explains. When copper samples are low, two injections are normally advised, but this can lead to poisoning. Re-sampling a month later determined this would not be necessary.
At 10/cow for injections and 6/cow for testing, copper deficiency treatment is expensive. But Mr Morgan reckons the cost is justified when considering possible losses in conception rates through poor mineral status.
The herd is now being tested annually to check for mineral status, says Mr Morgan. “Normally six fat ones and six thin ones are sampled in different areas of the farm to give an accurate indication across the herd.”
Autumn calving cows are then injected with copper at housing and spring calvers are injected at turnout. Replacement heifers are also injected with copper and selenium prior to bulling, adds Mr Pugh.
The farm also carries 500 Lleyn-cross ewes which also receive routine surveillance checks for mineral status. For the past two years, Mr Morgan has found it necessary to give his rams selenium injections before tupping. Lambs are also given cobalt boluses.