We’ve all heard good-growing dairy heifers are the future of our milkline, yet once they leave the calf barn, many are put out with dry cows, and if they are housed alone may be fed leftover feed from the milk cows. Such supervision by convenience is not a particularly good idea. Rather, dairy heifers require our best efforts to assure their special nutrition and management needs are met, which should pay off handsomely when they become profitable milk cows.
It’s no secret, no matter how well they are growing, replacement dairy heifers cost money in feed, housing, yardage and other non-feed related expenses until they enter the milkline. So it is important to accept two major rules when raising good quality dairy heifers: (1) the most profitable ones calve at 24 months of age, and (2) avoid over-conditioning (getting them fat) heifers before puberty.
These two basic guidelines are backed by many years of research and the premise behind a recommended optimum growth rate for pre-pubescent heifers of 1.8 to 2.0 lbs. per day and of 1.8 to 2.2 lbs. per day after they reach puberty.
We’ll want this growth rate to be steady bodyweight gain, which tends to promote a consistent body condition score of 3.0 to 3.5 (re: 1 = thin, 5 = obese). Subsequently, when replacement heifers are 14 to 15 months old, they will show consistent strong “heats” and are ready to breed at about 800 to 850 lbs. If all goes according to plan, they should freshen at 24 months of age and have a post-calving weight of 1,225 to 1,250 lbs.
To attain these modest growth rates (2.0 lb./head/day); the University of Wisconsin’s animal science department advise young replacement dairy heifers should consume a palatable diet containing a dietary energy level of about 65 to 69 per cent TDN. These energy values are based upon above freezing temperatures, when no metabolic energy is expended by growing heifers to keep warm.
Consequently, university and extension research has come up with additional cold weather rules of thumb for feeding dairy cattle (including replacement heifers) as follows: for every 1 C drop in temperature below 0 C, in most cattle TDN energy maintenance requirements increase by about two per cent.
Although, this is only an estimate based upon effective air temperatures, we can also use windchill temperatures without adjustments in order to calculate new heifer energy requirements. For example, an early morning windchill temperature of 20 C means there is an increase of about 40 per cent in the heifers’ (housed with little shelter) above basic dietary energy needs.
Regardless of winter conditions and dietary energy fed, protein levels in the replacement heifer rations are often standardized as follows: three-to six-month old animals need a diet of about 16 to 18 per cent protein, while older animals from six months to breeding age need a 15 to 16 per cent diet. When dairy heifers are bred at 14 to 15 months of age, these protein levels can be dropped to 13 to 14 per cent. About three weeks before replacement heifers calve, switch to a well-balanced 16 to 17 per cent protein transition diet with a similar modest energy level.
Transition or close-up rations for replacement heifers are important. They introduce pre-fresh replacement heifers to a little higher level of grain feeding they may not have received before. And there are many other advantages to feeding first-calf heifers a close-up diet — prepares the rumen for lactation diets, encourages feed intake, and reduces the incidence of displaced abomasums and other related metabolic problems after calving.
Supplemental mineral and vitamins complementary to forages should also be supplied to assure respective mineral and vitamin nutritional requirements (based on NRC recommendations) are achieved. A clean, good supply of water should always be provided, as well.
Subsequent diets for dairy heifers do not have to be complex. It could mean providing a good quality alfalfa hay and a 16 per cent heifer grain ration fed to younger calves, or providing a TMR (total mixed ration) containing limited amounts of high energy barley or corn silage, complimented with a grassy hay, mixed it with barley and a supplemental protein source.
It could also mean innovative, cost-effective heifer rations. For example, researchers at the South Dakota University (SDSU) mixed low-quality high-fibre corn stalks supplemented with wet distillers grains to meet the energy and protein requirements of growing dairy heifers. They compared this simple diet to a more traditional mix of corn silage, haylage and hay. The results showed although heifer gains were somewhat lower on the corn stalk/corn distiller’s diet, performance was still acceptable with an overall 40 per cent cost savings.
Remember no matter what diet is fed to dairy heifers, it is just as critical on the “where’s” and “how’s” these rations are put down in front of them. The golden rules of dairy-heifer bunk management are:
Segregate heifers according to weight and size. Avoid feeding small younger animals with older heavier animals. As pregnant heifers get closer (re: three weeks before) to calving, they need their own pen and own specialized “transition” ration.
Check feed bunks before the next feeding. You do not want a slick bunk or one with lots of refused feed. Heifers tend to sort feed; what feedstuffs were not eaten?
Watch your heifers for harmful animal competition; which ones are coming up to the bunk and which ones are being left behind to go hunger?
Provide enough bunk space. As the dairy heifers get older, they will require more eating area.
Get rid of old stale feed. And avoid feeding lactation leftovers. It may not be nutritional balanced for dairy heifers.
In colder weather, provide appropriate shelter and windbreaks, so replacement heifers can get out of the wind. For example, if calves are put in a pen, where the windchill factor is decreased by only 5 C, that translates into a 10 per cent savings in additional dietary energy spent on staying warm. Likewise, extra clean bedding put down on a frequent basis adds insulation against the cold and also saves on extra energy requirements.
PeterVittiisanindependentlivestock nutritionistandconsultantbasedinWinnipeg. Toreachhimcall204-254-7497orbyemailat [email protected]