The first step is to get the heifers checked by a vet, discuss a health plan and prioritise their feeding.
Most heifers return to the milking platform around May 1 and for a July 15 planned start of calving, a five to six week window enables liveweight gains – no gains should be expected in the last four weeks of pregnancy.
To put on 1kg liveweight, a heifer requires approximately 4kg DM above maintenance on quality pasture.
For every kg of liveweight below target, milk production is estimated to be negatively impacted by 0.25-0.4/kg MS. So for an additional 4kg DM, expect a return of $1.25 to $2 (at a $5/kgMS milk price). This equates to 30-50c/kg DM.
In-calf rates benefit
In addition to milk production benefits, heifers at near-target liveweight will have a better chance of getting back in-calf and be healthier than those well below target liveweight.
Allocating priority feeding to this group of animals shows a high return and warrants purchasing additional feed if required.
Despite best efforts to capture liveweight gains in the first six weeks after returning to the milking platform, some other management options should be considered to reduce the impact on reproductive performance and confine damage to the first lactation.
The options include managing the heifers as a separate mob; once-a-day milking to lessen the degree of negative energy balance in early lactation; or recording pre-mating heats and being ready to intervene with non-cycling treatments, if necessary.
Preventing added cost
Although these actions may reduce the negative impact of underweight heifers on health problems and in-calf rates, they all bear costs – including increased labour, increased farm working expenses and decreased milk production.
So it is much more desirable to prevent it occurring. So what should be done to prevent underweight heifers?
Review your heifer rearing management policy, be proactive with monitoring heifer weights and respond quickly when growth targets are not being achieved.
These animals form the basis for the future herd and a small amount of effort and attention to detail now can ensure they meet their lifetime production potential.
Heifer rearing focus farms
Five focus farms have been set up to help graziers grow heifers better and strengthen relationships with dairy farmers.
The farms – in Northland, King Country, North Otago and Manawatu – create an opportunity for dairy farmers and graziers to interact, and provide access to the same information for managing young stock.
As part of a Heifer Grazing Project, the focus farms are helping address statistics for six week in-calf rates and underweight heifers (a LIC study found 73 percent were more than 5 percent underweight at 22 months old).
Regular field days will be held at each focus farm.
This article was originally published in Inside Dairy March 2015