Any nutritionist will tell you that optimizing dry matter intake (DMI) is one of the most important factors in achieving target milk production.
DMI is a measure of moisture-corrected pounds of nutrients consumed by the cow. One pound of DMI can support 2 pounds of milk, but achieving this can be influenced by a number of factors and can get quite complicated. “Optimal” DMI may refer to greater intakes for high-producing cows to achieve greater milk yields or reducing intakes in order to increase feed conversion efficiency for lower-producing cows.
The amount of feed a cow consumes can impact her performance throughout lactation. Cows are dependent on feed to support their requirements for maintenance, growth, reproduction and milk production. Otherwise, they will mobilize their own body stores (fat, muscle, etc.) to support those requirements. When feed intake drops, a cow must continue to meet these energy demands, and usually, milk production is the first to decline if demands are not met.
The ability of an animal to consume adequate energy for maximum milk production is the major limitation of high-producing dairy cows and is determined by the energy density of the diet and how much she eats. The size of meal consumed by the cow, and how often she eats, is influenced by animal and dietary factors affecting hunger and satiety.
DMI fluctuates throughout lactation and needs to be carefully managed, especially during delicate phases, such as the fresh period. Slow or sluggish intakes in fresh cows can lead to conditions such as ketosis or displaced abomasum and ultimately impact productivity throughout lactation. The peak in DMI comes after peak milk production, yet at the same time, this is when bodyweight is at its lowest (Figure 1). Achieving the right synchrony between DMI, milk production and bodyweight can be a challenging feat in itself but is the key to optimal efficiency and production.
How much a cow eats can vary drastically depending on her stage of lactation. There are many factors that may impact intake, but three main factors usually dictate why a cow may stop eating:
1. Metabolic reasons: This can be due to acidosis, dietary fat level or high propionic acid. The theory that propionate or other oxidized fuels may impact intake is known as the hepatic oxidation theory.
The hepatic oxidation theory centers around DMI being partly controlled by oxidation of fuels within the liver, which can signal satiety and stop eating. These fuels are propionate produced within the rumen and the oxidation of dietary or mobilized fatty acids. It is impossible to completely control the oxidation of these fuels within the liver on a commercial dairy farm, but there are ways that dietary management can help, such as controlling body condition score and limiting feeds with rapidly fermented starch in transition cows.
2. Physical factors: Rumen fill constraints due to feeding low-quality forages.
Feeding low-quality forage can result in a limited intake due to the “filling factor.” If you are feeding a high-fiber diet that is low in neutral detergent fiber digestibility (NDFd), for example, intake can be restricted by the fiber filling the rumen, as well as the feed staying in the rumen longer due to the poor digestibility.
3. Non-nutrient reasons: environment, heat, feed availability, temperature, lameness, etc.
It’s important to identify which one (or more) of these factors may be limiting your goal of achieving optimal DMI and ultimately production and feed efficiency. Transition cows can be the most sensitive with regards to their intakes, which makes it imperative to maintain proper condition through the dry period so cows do not lose more than one unit of body condition score during the fresh period. A well-formulated pre-fresh diet and fresh diet post-calving can reduce the amount of body fat mobilization. As a cow progresses towards peak milk, feed intake is limited by gut fill, and subsequently, a diet high in fermentability, but also consisting of high-quality forage, should be offered.
Management practices can further improve intake, as well as lead to better components, overall health, reproduction, etc. Daily evaluations of the following should be conducted:
- Pen capacity and bunk space (are the number of cows in a pen limiting eating time?)
- Adequate number of stalls, cleanliness of stalls and waterers, accessibility of water sources
- Lameness or metabolic problems
- Heat stress (are cows being cooled properly?)
- Fresh feed available with adequate push-ups
- Check total mixed ration (TMR) mixer scales and knives periodically
Management factors such as crowding, cow comfort, perching, abrupt dietary changes or water availability can also impact how much a cow eats. Pinpointing how much your cows are eating is key in identifying major farm metrics, such as feed efficiency and income-over-feed costs. Talk with your nutritionist to develop a plan for helping your herd reach their potential.
References omitted but are available upon request by sending an email to the editor.
