The transition period of dairy cows is characterized by changes in behavior, hormonal patterns, and increased metabolic and nutrient demands. Cows in late gestation (2-3 weeks to calving) undergo changes in metabolism and a mismatch between dry matter intake/nutrient uptake and their requirements, which prompts the mobilization of body stores, mainly fat from adipose tissue and glycogen from the liver.
These changes also predispose to metabolic disorders such as ketosis, acidosis, and displaced abomasum. Research has shown that feeding lower dietary energy including more fiber in the diet, promotes intake after calving, and results in less body fat mobilization. It has also been suggested that moderate energy intake pre-calving may positively impact cows’ fertility.
Which is the most suitable diet for dry cows?
Today’s suggestions are to feed dry cows low energy diets [1.30 to 1.39 Mcal of net energy for lactation (NEL)/kg of dry matter (DM)] during the entire dry period. One limitation is that high straw diets result in rumen filling at a stage of the pregnancy where the fetus is already occupying more space, and that they may also increase the risk of feed sorting.
Recent research however has also suggested that high fiber:starch ratios inhibit the expression of the genes regulating rumen papillae growth. The challenge is to feed fibrous roughages while promoting the development of an adequate rumen papillae surface needed to absorb the sudden increase in volatile fatty-acids resulting from the highly digestible feeds available in early lactation.