In the last 10 years there has been a tremendous amount of research centered on the transition period of the dairy cow. The dairy industry is well aware of the importance of a good transition-cow program and its effects on decreasing infectious and metabolic disease of the fresh cow and maximizing milk production during that lactation. The dairy calf also goes through a very critical “transition period” from being milk-fed to relying only on grain and forage to satisfy its nutrient requirements for maintenance and growth.
In order to “transition” the calf, the weaning process has to be in synch with rumen development. There are pictures on the Internet showing a fairly well-developed rumen at 4 weeks of age. However, these calves were not receiving 20 percent of their bodyweight in milk per day, which is the amount they would normally consume if they were left on their mother, and were forced to look elsewhere for the nutrients needed to survive. Early consumption of large amounts of calf starter is a sign that the calf is not receiving enough nutrients in its milk to satisfy its requirements for growth and maintenance. Since the rumen is not well developed at the time that the calf starts to consume calf starter, a very small portion of it is actually digested and utilized by the calf. Therefore, the calf is not receiving enough nutrients from the limited amount of milk and starter to reach its genetic potential for growth. Even though the rumen is developed in this case at 4 weeks, the calf is still not growing well, and its immune system is not receiving enough nutrients to function properly.
If the calf receives 15 percent of its bodyweight at birth for the first week of life and then 20 percent of its body birthweight per day from the second week of life, and continues to receive this amount, the consumption of calf starter gradually increases as the calf grows and gains weight. Once it reaches the weight where it needs more nutrients, calf starter consumption increases accordingly. It will usually take seven to 10 weeks for the calf to increase consumption of calf starter to reach the goal of 4 pounds of 18-percent-protein starter or 2 pounds of 24- to 25-percentprotein starter.
This gradual increase in the consumption of calf starter allows the rumen to develop at a consistent pace without large amounts of starch entering the rumen at once, thus decreasing the chances of rumen acidosis. This is enough time for the rumen to develop sufficiently to digest or ferment the feeds that enter the rumen. It is best to feed only calf starter for at least seven to 14 days after weaning, to further develop the rumen from starch fermentation and the production of butyric acid. Calves should be left in the hutch or individual pens during this time in order to observe the amount of starter consumption.
Traditional weaning programs will have a goal of weaning the calf at a specific age. In order to accomplish this, the amount of milk being fed is reduced at a certain age in order to force the calf to consume more starter. The calf usually only has about one week at this reduced amount of milk before being weaned. The problem with this system is that the rumen does not have sufficient time to develop prior to the calf being weaned. The calf is forced to consume more starter to try and satisfy its appetite and nutrient requirements but does not have a sufficiently developed rumen to ferment the feed in the rumen efficiently. These calves will often develop rumen acidosis and “matting” of the rumen papillae.
Calves can be successfully weaned on this type of program if they have been consuming a significant amount of calf starter for at least three weeks prior to weaning. However, if they are consuming a lot of starter earlyon, like this system requires, they are definitely not receiving enough nutrients through the milk to achieve their genetic potential for growth and fuel their immune systems. They also are much more likely to have issues with rumen acidosis because they are consuming larger amounts of starter before the rumen papillae are developed well enough to absorb volatile fatty acids produced from starch fermentation. This resulting acidosis can have an adverse effect on the rumen for the rest of the life of that animal.
A successful transition program for the dairy calf must include the presence of a rumen that is sufficiently developed to efficiently ferment dry feed. It must also be designed to provide the necessary nutrients to allow the calf to gain weight and increase in size according to its own genetic potential, at all times. Traditional programs of feeding the calf at a rate of only 10 percent of its birthweight per day are borderline starvation diets and, in times of cold weather or heat stress, often result in weight loss and increase in infectious disease.
A reachable goal is to double the birthweight of the calf at 8 weeks of age. More intensive programs with increased milk solids can result in the tripling of the birthweight at 10 weeks of age. Designing a transition program with these thoughts in mind will result in a tremendous increase in the rate of gain without excessive fat deposition, a much healthier calf with lower morbidity and mortality rates, a heifer that reaches the appropriate breeding size much earlier, and a first-lactation heifer that enters the herd at a younger age and with the ability to produce much more milk. As long as a high plane of nutrition is maintained during the entire growing period of the heifer prior to the first calving, the longevity of these heifers is improved as well as lifetime milk production. Successfully transitioning the dairy heifer calf is an important investment in the future productivity and profitability of the dairy operation.