Focus on body condition for 22-month in-calf heifers
A large amount of dairy replacement stock has been housed or shifted onto crops over the past few weeks. Dosing for parasites such as liver fluke, lice, stomach and lung worms has been common practice over recent weeks, especially where milk, blood or dung samples have been analysed and have confirmed a significant parasite burden on the herd.
There are many farmers who have found liver fluke to be a significant issue this year, are dosing cattle upon housing and have a plan to dose cattle again at the start of the new year.
However, there are others where treatment for liver fluke will be omitted or limited to a single dose around eight weeks after housing. This is an appropriate decision if milk samples have been taken and have indicated a negative or low incidence of liver fluke, which has been cross-checked with dung samples. A suitable parasite control plan is an important element of achieving a high status of animal health but, like a lot of issues, it is specific to an individual farm.
Animals generally have to be handled through some form of race or crush for dosing, depending on the product being used, and it can provide a great opportunity to weigh animals and record the liveweight of youngstock at the start of the housing period. You may not feel there is benefit in this exercise and assign the difference in weights to the fact that the later born heifers are the smallest and always will be.
However, calf and heifer management on many farms is a limiting factor to herd reproductive performance. A few small heifers have a large impact on fertility as low weights delay puberty. This delays calving and the interval from calving to the next conception.
In contrast, well-grown heifers will produce more milk in their first lactation, compete better with mature cows and survive longer in the milking herd. Therefore, one flippant thought may be costing you a lot of money. The reality is that late-born heifers must achieve the same liveweight targets as their earlier-born counterparts by the start of mating. To achieve this, they must grow faster; the easiest way to achieve this is by preferential feeding.
Making sure heifers calve on time and at the right size takes planning. Setting targets and measuring heifer weights every three months will promote management changes to achieve these targets. Target heifer liveweights are shown in the table (below).
At housing, for a spring calving herd we are considering weanlings which should be at the nine-month target and in-calf heifers at the 22-month target. Weigh them at a similar time of day, preferably in the morning, or let them stand in the yard for two hours to minimise the effect of changes in gut fill. Handle heifers quietly and avoid forcing them through.
A piece of rubber mat or carpet to cover the platform of the scales can be useful to reduce noise stress. In-calf heifers weighed at 22 months should relate to heifers two months before calving and before the foetus, foetal fluid and membranes increase in weight.
Essentially, the 22-month liveweight target is the final goal that you are aiming to achieve. At this stage, achieving the correct body condition score is the priority for a 22-month in-calf heifer. However, management over the winter will significantly influence the liveweight gain of the weanling heifer. Remember especially that the first 12 months are the most critical for skeletal and muscle development.
Weanlings require a high quality diet, and where silage or pasture quality is poor, a quality supplement with at least 11.5MJ ME/kgDM and 16pc crude protein will be needed to meet this nine-month target. Remember, this corresponds to nine months from the start of calving for all weanlings (including late-born calves). Feeding groups of heifers according to their size and weight can help ensure that smaller, lighter heifers reach their target weight at mating.
Dr Mary Kinston is a farm consultant based in Kerry. Email: firstname.lastname@example.org
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