Feeding Higher Forage Diets before Calving Improves Dairy Cow Metabolic Health
Dairy cows are frequently afflicted with metabolic diseases after calving. The high incidence of disease is thought to be related to the prolonged periods of negative energy balance that commonly occur postpartum. The dietary energy requirements of dairy cows are at their highest levels at calving and immediately postpartum and in most cases, a cow cannot physically eat enough feed to meet her energy needs. For an unknown reason, this period is also characterized by a drop in dry matter intake. Therefore, during this time, the cow is in a state of negative energy balance (NEB).
In an effort to reduce NEB, many dairy producers will feed cows an energy dense diet beginning three weeks before calving. However, this practice may lead to overconsumption of energy, which is subsequently stored as triglycerides (fat stores) in adipose tissue. During times of NEB, triglycerides are broken down into non-esterified fatty acids (NEFA) that are used for energy. NEFA are transported in the blood to the liver where they are transformed into ketone bodies. Beta hydroxybutyrate (BHB) is the most common ketone body in dairy cows. While BHB is a highly available energy source, excess levels can lead to subclinical or clinical ketosis. Subclinical ketosis can decrease milk production and affect reproductive performance. In addition, surplus NEFA are repackaged into triglycerides in the liver, which accumulate, and thus, increase the risk of fatty liver. Metritis, retained fetal membranes, mastitis, milk fever, and displaced abomasum have been associated with fatty liver syndrome in dairy cows. Interestingly enough, cows that consume excess energy and are over-conditioned prior to calving tend to experience more extreme NEB postpartum and have higher concentrations of BHB than cows that were fed prepartum diets that met energy requirements.