Dairy records show no reduction in milk production for those heifers that calved earlier when compared to heifers calving at 24 months or greater.
By Robert B Corbett DVM, PAS, Dipl. ACAN
The majority of the dairies in the U.S. have a specific age at which they begin to breed their heifers. A much smaller percentage may also include requirements on height and/or weight that the heifers must reach before receiving their first insemination. Those dairies that are using height and/or weight, soon realize that not all heifers are ready to be bred at the same age. Others are afraid to breed heifers that reach the height and/or weight goals if they are younger than a certain age.
Puberty of the dairy heifer depends on size and not on age. Animals will reach puberty at different ages since their genetics and rates of growth vary. Heifers that are on a higher plane of nutrition will reach puberty at an earlier age because of improved feed efficiency and growth rates. Intensive feeding programs have become much more popular in recent years because of the numerous studies that have been published proving that heifers raised on these programs will produce a significantly higher volume of milk than heifers raised on more traditional programs. Heifers on intensive feeding programs also have reduced morbidity and mortality rates, lower culling rates, increased longevity in the milking herd, and higher return on investment.
Heifers are commonly fed rations that are lower in protein than what they require. The main reason for this is that protein is more expensive than energy and the dairy is trying to reduce feed costs for the heifers. Rations that are higher in protein and successfully meet the protein requirements of the growing heifer will result in improved feed efficiency and reduced cost per pound of gain. When assessing feed costs, the dairy owner will most often look at the cost per head per day or cost per ton of feed fed to the heifers. However, the most important number is the cost per pound of gain. Poultry, swine and beef cattle producers all recognize the fact that their profit lies in improving feed efficiency and reducing the cost per pound of gain. The same is true for dairy heifers, but this number is seldom calculated. The main reason for not knowing the cost per pound of gain is the lack of obtaining weights on the heifers at various stages of growth.
Most of the heifer-management software programs have the ability to record multiple weights of heifers during their development. The following times are recommended for recording heifer weights: birth, weaning, five to six months, pre-breeding, and pre-calving. Dairies that have done this for some time can show that there is a direct correlation between the heifers that gain the most per day and an increased level of milk production. Recording heifer weights also helps the dairy to know if their nutrition program is yielding the desired results, and if changes made in the program are successful in improving weight gains and reducing cost per pound of gain.
During a five year study that I conducted on a client’s dairy, I received the highest and most efficient gains when the crude protein level was between 16 and 16.5% starting at nine months of age. The potential gain from Metabolizable Energy was formulated at 400 to 450 grams less per day than the potential gain from Metabolizable Protein. This allowed the heifers to grow in stature and muscle deposition without becoming over-conditioned.
It has been recommended that heifers should be approximately 55% of the average adult weight in the herd when inseminated for the first time. As an example, if the average weight of the adult cow in the herd is 1,500 pounds, then the heifer should weigh around 825 lbs. at first insemination. There are some older papers that have been published that suggest that breeding heifers at a younger age will result in lower milk production when they calve. However, these heifers were not the correct size or weight at the time they were inseminated. If the criteria of 55% of average adult weight is used, and a height of 51 inches or 130 centimeters at the withers is used for the first insemination of Holstein heifers, approximately 28% will reach these goals by 10 months of age, another 60% by 11 months of age, and the final 12% by 12 months of age.
Many have expressed concerns that breeding heifers this young will lead to problems with dystocia, reduced milk production, lack of maturity, and increased culling rates. I have clients who have been on this intensive program for close to 20 years and they have experienced just the opposite. Following is a graph from a dairy that shows the 305 ME on first calf heifers by the age at first calving:
As you can see from the graph, there was no reduction in milk production for those heifers that calved earlier when compared to heifers calving at 24 months or greater. We have also noticed that the longevity in the herd is greater because these heifers are producing more milk and as a result, are less likely to be culled. Since these animals are all of sufficient size and weight at breeding, there is no issue with not being able to compete with other animals at the feed bunk after calving.
An intensive heifer feeding program is another way to improve efficiency and profitability on the dairy by reducing costs per pound of gain, decreasing morbidity and mortality rates, and increasing milk production in first-lactation animals, as well as subsequent lactations. It is important that body condition be monitored at all stages to ensure that the rations are formulated correctly to maximize frame growth and muscle deposition without becoming over-conditioned. Most dairies have an excellent genetics program in place and carefully select the bulls they want to use to improve the genetic base in their herd. However, the only way to reap the full benefits of the genetics program is to allow each animal the opportunity and ability to reach their full genetic potential through proper management and nutrition.
A well-designed growing diet can help heifers reach puberty and first breeding at younger ages, with benefits including better health, longevity and return on investment.