Anna Martyn, Veterinarian BVSc, MACVSc, King Country Vets
There are two rather sneaky phenomena going on now for herds, the true impact of which could be hard to see until they hit the bottom of the cliff.
Firstly, many farmers, particularly those who have managed to have a tight calving pattern, will be starting to feel a real crunch point.
While this season has been kind with regards to metabolic diseases, many farmers are feeling a squeeze with poor pasture growth, tight second-round grazing and impact on body condition scores.
How this dilemma is handled will have a significant impact on both six-weeks-in calf rates and ultimately not-in-calf rates. Obviously, there are plenty of pressures at play this season, many of which are external, but how are you going to handle this?
If cows lose a full body condition score after calving (even if they make it up closer to mating), have significantly reduced reproductive performance. This will vary per herd but now is the time to get at least 70 cows individually body condition scored and entered into MINDA by an accredited assessor.
By doing this, it allows the true impact to be demonstrated for your herd. In clients that performed this last season, there was significant difference between cows that remained at 4.5 or 5 BCS versus those at 4, translated to a difference of 9% versus 25% empty rates respectively. So, do what is possible right now within your farming system to keep that body condition stable.
The second issue rearing its ugly head is affecting the younger members of the herd. We are seeing calves as young as three weeks old being affected by coccidia, a disease that is usually associated with calves around weaning and up to six months of age. This devious disease can be affecting far more animals than the clinical diarrhoea signs of green or bloody faeces, intestinal mucosa plugs, fever, abdominal pain and reduced appetite may reveal.
Subclinical calves don’t have the diarrhoea, but this parasite will be affecting their gut lining and consequently growth rates. Studies have shown that these reduced growth rates can result in up to a 27-kilogram difference in heifers’ weight at one year old. We know this difference does have significant impact on puberty and heifer pregnancy rates.
Generally, the signs are seen two-to-four weeks after exposure. This means, two-to-four weeks after calves go out on contaminated pastures.
The impact of the disease is exacerbated by any stressors such as change in diet, poor weather conditions, overcrowding and regrouping of calves.
Most meals and some milk powder have a coccidiastat in them. These are a group of products that help minimise the lifecycle of coccidia, but they do not kill the parasite and the impact depends on how well the calves are eating the product that contains it.
In some studies, they have not significantly reduced the number of oocytes shed into the environment and once removed from the diet, calves can go backwards.
The alternative is using a coccidicide. They work by rupturing the coccidia and allow the calf to start to develop an immunity against this disease. However, they only work if the parasite is present, so testing to confirm this is important to ensure bang for your buck.
For the calves, trying to time treatment for 14-21 days after initial exposure, should limit potential gut damage, reduce contamination of the environment and improve weight gains. However, not all coccidiacides are equal, so best to talk about what is needed for your specific circumstances.
