The importance of regularly weighing young stock has been further underlined following results from AHDB Dairy’s two-year Calf to Calving project, which identified huge variation in growth rates within batches of heifers.
The UK-wide initiative started in the autumn 2015, with the aim of helping producers to improve calf survival and increase the number of heifers making it into first lactation.
Twelve dairy farms were enrolled in the project and acted as hosts for a series of farm meetings on best practice heifer management during the two-year project. Six farms were autumn block calving and six had a spring-calving. The growth, health and nutrition of 10 heifers from each farm were monitored every three months.
This growth data highlighted the inconsistencies in growth rates within groups of heifers on individual farms and the fact many heifers fail to hit the target growth rates required to calve at 24 months old. Some of the key targets set included reaching 50% of mature body weight at 12 months old, 60% at 14 months old, and 85% post calving.
AHDB Dairy’s Andy Dodd, who led the initiative, says that 72% of all heifers failed to achieve the target of doubling birth weight by weaning and half were not on target at each three-monthly weigh point. “There was also huge variability within groups. On one unit, for example, heifers were achieving between zero and 2kg of daily live weight gain at six to nine months of age.”
On some units, heifers between 12 and 15 months old were also only achieving 0.1kg of liveweight gain per day – well below the rate required to hit the ideal weight to calve at 24 months.
Regular weighing essential
“The results from the 12 units show that it’s impossible to estimate weights by eye or to spot variation in growth within a group by simply looking at animals in a pen. Regularly weighing animals and managing heifers in weight groups is essential to make sure that they stay on track in terms of growth rates.”
The need to continue to weigh animals at grass was also highlighted by the fact the biggest variability in growth rate was seen at the end of the summer across all heifers. This correlated with declining grass quality and insufficient supplementation.
Housed versus grazing young stock
“One unit’s heifers were really consistent when housed inside on the same diet and as soon as they went out to grass, growth dropped off in some animals. Some were 450kg and others were 350kg,” says Mr Dodd.
However, declining growth rate is not inevitable when grazing young stock, with some units achieving good consistency in growth rates while at grass.
Weighing at turn out
“If you turn heifers out to grass, weigh them at turn out and then weigh 10% of them between two and three weeks later to see if they’ve grown. Split heifers according to weight at grass and supplement those that need it. There is a marked spread in performance within groups, so producers need to target management better to ensure consistencies in growth.”