Dairy Heifer Calves
A dairy cow’s life does not start when she produces milk, it starts on day one as a newborn dairy heifer calf. It is imperative dairy heifer calves receive adequate amounts of quality colostrum soon after birth to provide them with immunity, which will help to prevent scour and potentially life threatening illness. Diverting energy into fighting disease will reduce growth rates and decrease the likelihood of the young dairy heifer joining the herd at 24 months or younger.
Maiden Dairy Heifers
Besides disease, stress and poor nutrition can limit dairy heifer growth rates, this delays puberty and increases the age at which you can first serve her. Provided that heifer calves are not in an excessive body condition, you should be aiming to serve maiden dairy heifers at around 15 months of age although frame and weight is a better indicator than age alone. Target weight for first service is around 60% of their mature weight so for Holstein-Friesian heifers this is around 420kg, whilst for smaller Jersey heifers this is around 265kg. This means yearling heifers need to gain an average of around 0.7-0.8kg/day from birth to reach their target. Commercial cross-bred ‘Kiwi’ style Jersey X holstein heifers can be expected to have a middle ground target weight.
What bull is best for dairy herd genetics?
Deciding what bull to use on maiden dairy heifers is also tricky. If you are breeding to improve your dairy herds genetics, replacement heifers should be genetically superior animals compared to their dams. Therefore, heifer calves out of heifers would accelerate your dairy herds rate of genetic gain. However, allowing dairy heifers to calve larger purebred calves may be undesirable especially in smaller heifers. Therefore, a compromise might be to artificially inseminate your best grown heifers with sexed semen; this should return around 90%+ superior replacement heifer calves, whilst using easy-calving beef bulls such as the Aberdeen Angus on the smaller heifers. Alternatively, some farms prefer to artificially inseminate their whole batch of maiden heifers with sexed semen, and then run them with a sweeper beef bull or AI to standard semen. This can increase fertility in the herd as dairy heifers which hold to first service are likely to naturally be more fertile.
In-Calf Dairy Heifers
Once served, in-calf dairy heifers require careful diet management to ensure they continue growing throughout pregnancy without gaining excessive condition, which could lead to a difficult calving. Ideally, heifers should be managed separately to cows, in order to reduce mixing stress and reduce the competition with adult cows at feed barriers.If this isn’t an option, mixing in-calf heifers with dry cows in the run up to calving may be a good solution. This will reduce stress and the associated milk drop, which usually occurs when mixing heifers with in-milk cows. Dairy heifers should also be given extra space in order to distance themselves from adult cows, so spare cubicles and more space at feeding troughs helps to reduce conflict. Additionally, prior to calving, heifers should be introduced to the parlour and milking routine to aid their smooth transition into the main herd.