There is increased interest in having a single diet for dry cows rather than separate diets for far-off and close-up cows. Jim Drackley, professor of nutrition in the department of animal sciences at the University of Illinois, addresses three possible strategies for accomplishing this. The following answer is adapted from a paper he presented at the American Association of Bovine Practitioners conference in September.
Q: With a single dry period diet, how do I control for energy intake?
A: In light of the apparent desirability of feeding to allow cows to meet but not greatly exceed their requirements for energy during the dry period, there are at least three approaches that could be implemented to achieve this goal. The first is to feed cows only poor-quality roughages and other dietary ingredients that would minimize the potential for excessive energy intake. This is the concept that was the default management option on many farms several decades ago. However, the dangers are that excessive variation of ingredient quality may promote inconsistent intake of nutrients, the ration may provide imbalanced nutrient profiles, and such feeds may be contaminated with molds or toxins. This is not a desirable mind-set or approach and it will not be considered further here.
Two better approaches are:
- Limit-feeding: Formulating a diet of moderate energy density (1.50–1.60 Mcal NEL/kg DM) and limit-feeding it in amounts of dry matter (DM) that would meet the average Holstein cow or heifer requirement of 14–15 Mcal daily. Note that we are not advocating limiting cows below their requirements as we have done in some of our experiments (Dann et al., 2005, 2006; Douglas et al., 2006), although those cows almost always has the most favorable metabolic profile after calving. One study that implemented limit-feeding to requirements found favorable results (Holcumb et al., 2001), whereas a more recent study showed little difference between limit-feeding or ad libitum feeding (Winklemen et al., 2008). It should be noted in the latter study, however, that cow numbers were limited and three of nine cows assigned to the ad libitum (overconsumption) group developed health problems at calving and so did not contribute postpartum data to the evaluation.
Conceptually, limit-feeding is a workable method for controlling energy intake. In practice, however, it requires a high level of management to implement successfully. Limit feeding works only where cows are housed individually (rare) or where group-feeding systems allow an abundance of feeding space. Feed must be delivered over bunk space that is adequate to allow all cows access to feed. Implementation requires that dairy producers become as adept at managing feed bunks as beef producers are. The goal is to formulate rations for target DM intakes that would take cows at least 18 h/d to consume. In other words, dry cows should be fed to a clean bunk shortly before the next feeding. Given the dynamic nature of cows moving in and out of single-group dry cow pens or close-up pens, and perhaps variable total numbers of cows, management of limit-feeding often is more challenging on dairy farms that in beef feedlots.
- High-bulk, low energy diets: Formulating rations of relatively low energy density (1.30–1.38 Mcal NEL/kg DM) that cows can consume free-choice without greatly exceeding their daily energy requirements. The principle is to feed cows a diet of sufficient fiber (bulk) content that cows will only meet their requirements consuming all the DM they can eat. The target intake thus allows neither too much nor too little energy, but rather just the right amount to match requirements.
To accomplish the goal of controlled energy intake requires that some ingredient or ingredients of lower-energy density be incorporated into diets containing higher-energy ingredients such as corn silage, good-quality grass or legume silage, or high-quality hay. Cereal straws, particularly wheat straw, are well-suited to dilute the energy density of these higher-energy feeds, especially when corn silage is the predom