When weaned dairy calves are released from the calf barn and put into replacement heifer pens, there are different ways of feeding them.
Some post-weaned heifers are not well fed and poor nutrition is almost guaranteed to make them struggle throughout their first lactation. Other replacement heifers are fed too well. As a result, they become fat, which is proven to affect lifetime health and production. Somewhere in the middle of extremes is well-balanced heifer nutrition. With a little homework, we can feed them properly, so they can become profitable dairy cows.
As a dairy nutritionist, I would love to visit a dairy farm and have immediate proof that any of their dairy heifers are eating with vigour a well-balanced post-weaning diet that achieves 2.5 per cent of their body weight/dry matter intake (BW/DMI).
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This proof would show in black and white; making them grow ideally at about 1.8-2.2 lbs. per day until they are bred at 13-15 months. Unfortunately, most people don’t keep these kinds of records. Most of the time, I usually catch producers at the busiest time of the day and they tell me to go look at the replacement heifers and see what I think.
Recently, seeing a pen of young unbred heifers, I took into account their health status and body condition. I also looked at what kind of feed was in their feed bunk. I judged that these heifers were in excellent health and most had a body condition score of around 3.0-3.5 (re: one = emaciated, five = obese). It was my understanding that grass hay was just put down as their second feeding, which followed a morning TMR of ensiled and dried forage, some grain and a mineral-vitamin premix.
On a footnote, I feared that one or two of these heifers might be borderline over-conditioned, which university research demonstrates that such dairy heifers will still lay down a lot of frame and lean tissue compared to those heifers on a more growth-controlled program. But, many often become fat and thus ruin their chances to become good milkers. Unfortunately, once a heifer becomes over-conditioned, there is really no way to reverse it.
Recommended requirements
Therefore, I recommend diets formulated with matching nutrient requirements of unbred replacement heifers that support recommended growth rates and optimum body condition scores. These are: an energy level of 66-68 per cent TDN (total digestible nutrients), 14-16 per cent protein and a complement of essential minerals and vitamins. Then once they are bred, relax both energy and protein intakes by 10-15 per cent, depending on their current BCS status.
Dairy producers can usually provide such well-balanced diets for their growing replacement dairy heifers. It has been my experience that these diets usually fall in three different categories:
- Simple hay and grain rations: One producer I know runs about a 150-cow dairy and segregates his heifers in three pens: unbred two to five months, unbred five to 15 months and then bred heifers. He feeds an alfalfa-grass mix free-choice in the bunk and an 18 per cent heifer grower pellet medicated with rumensin in self-feeders. The bred heifers have their forage mixed 75:25 with straw.
- Straightforward TMR diets: Another producer who runs a 200-cow dairy segregates his bred animals from his six- to 15-month unbred heifers. He makes up a bred-group TMR diet consisting of corn silage, alfalfa hay, straw, no grain and a min-vit premix. He dilutes this diet with about 25 per cent second-cut alfalfa hay plus 1.0 kg of grain corn for his six- to 15-month unbred heifers. His two to six-month-old heifers are housed at the other end of his farm and they are fed high-quality timothy hay and 2.0 kg of a 16 per cent texturized heifer grain diet.
- Low-cost diets: South Dakota University mixed low-quality-high fibre corn stalks supplemented with wet distillers grains to match the energy and protein requirements of growing dairy heifers. Weight gains on this diet were slightly lower than traditional heifer diets, but cost of gain was cut in half.
By feeding any of these practical diets, dairy producers should be able to match their young replacement heifers’ nutrient requirements for good growth and development. Most of the time, we don’t need written records to see if young replacement heifers are growing well. All we need to do is walk the feed bunk and assess their current body conditions, which tells us if they are on the right dietary track – up until they become good first-lactation milk cows.
