Weighing heifers vital as grass quality takes toll

This season’s reduced grazing quality has taken its toll on heifer growth rates meaning that regular weighing and appropriate supplementation will be a must this autumn to keep heifers on track.

Recent heifer weight data from one of AHDB Dairy’s Calf to Calving (C2C) host farms in Dorset, shows a sample of 11-13 month old, grazed heifers are about 50kg behind a target of 330kg.

In order to calve in at the most economic age of 24 months and hit 90% of mature weight at calving, they now need to gain 860g/day, which can only be achieved through supplementation. If this growth is not addressed, heifers may calve in later at a cost of £2.87 a head for every day over 24 months.

The drop in growth seen at Peter Hunt’s farm in Sherborne, mirrors that seen on a sample of seven farms involved in the C2C initiative. As part of the C2C initiative, the growth, health and nutrition of 10 heifers on each of 13 farms are being monitored every three months. Farmer meetings are also being run on the host farms with the aim of bringing the latest research and best practice to farmers, improving calf survival and increasing the number of heifers making it into first lactation.

Overall, 54% of heifers weighed on seven farms have been found to be below target weight following the last weighing. AHDB Dairy’s Technical Manager, Andy Dodd says this correlates with grazing quality.

“The heifers that have reduced growth rates are general the ones that have been grazing. That’s largely due to the fact grass ME is down by about half a point which obviously impacts on growth,” he explains.

Mid-summer fresh grass has generally analysed at around 11.5ME, versus a usual 12-12.5ME. Although ME is now picking up, declining grass dry matter may further add to heifer rationing challenges.

Andy says this highlights the need to weigh heifers to see if any lighter animals need to be split out and supplemented with quality silage or about 1.5-2kg of concentrate a head. Farmers can also take fresh grass samples or use the AHDB Dairy “Forage for Knowledge” website to look at grass quality on farms in their area to asses if there is a quality shortfall.

He also advises farmers to avoid “guessing” heifer weights and instead use weigh bars or a weigh band. This was highlighted at the recent Calf to Calving event at Blackmarsh Farm, where attending farmers were asked to guess the weight of the 10, 11-13 month old heifers. On average, the group over estimated by around 50kg.

Andy says monitoring helps determine if heifers are going to hit key milestones. “For example, for heifers to reach puberty they need to be 50% of their mature weight. This target needs to be reached around 12 months of age to allow them to have several cycles before being served to maximise first service conception rates,” he explains.

In preparation for the winter, Andy also advises farmers to think about milk feeding rates when ambient temperatures drops below the calf’s critical temperature.

“For calves up to three weeks of age, for every 5 degree drop below 15 degrees, you need to increase milk volume fed per head per day by 0.33 litres. When you’re doing it as a one off, it’s best to increase the volume rather than the concentration to avoid nutritional scours,” he adds.

Calf jackets also have a role to play in maintaining growth rates at the target 750-800g/day from birth to calving. By keeping calves warm in such a way, they can then partition energy towards growth.

However, Andy stresses that keeping calf jackets clean is a must so as to avoid transmission of bugs such as cryptosporidiosis which can cause watery, yellow scours.

The disease is caused by parasites, which can be spread in the environment, via other calves and from their dams. As a result, good hygiene practices are essential.

“Calf jackets can potentially harbour crypotosporidium eggs. These can only be destroyed if the jackets are disinfected with a licensed cryptosporidium disinfectant and then washed at 60C. The eggs are only destroyed at temperatures at or above 60°C. It is important to allow the jackets to dry completely before re-using them,” he says.

Not all disinfectants will kill crypto and not all calf jackets are suitable for washing at 60C, so farmers are advised to check data sheet and product information.

At the same time, particular attention should be paid to colostrum feeding and managing the environment.

Andy adds: “In the calf sheds and calving pens, applying heat through using a steam clean is as important as the hot wash for the calf jackets. You need the heat to kill the eggs that haven’t hatched. Ideally, muck out, steam clean and disinfect between calving and calves. Allow pens to dry as cryptosporidium does not like dry conditions and the eggs will not survive being dried out.”