PD Poll Question
Most read Herd Health articles
|Dairy basics - Herd Health|
|Written by Ralph Bruno|
|Tuesday, 05 April 2011 12:56|
Texas A&M's Ralph Bruno explained the causes and symptoms of the metabolic disease ketosis in this 2011 article. Click here to jump to the article.
Ketosis is a metabolic disease very often observed in high producing herds. It is associated with poor management of the transition period resulting in decreased dry matter intake and increased BCS loss (fat mobilization) therefore, increasing blood circulating levels of ketone bodies.
Many dairy producers focus their ketosis prevention strategy on the postpartum period missing several factors observed prior to calving (transition period) that are associated with ketosis. Some common strategies used by producers for ketosis prevention include dietary supplementation of glucose precursors on fresh cow diets, reduction of the stress factors in the fresh cow pens, daily monitoring of animal health after calving etc. However, only few dairy producers would extend their strategy over the entire transition period.
Since ketosis is a disease that is associated with management of the prepartum period, not monitoring the transition period (far off and close up pens), producers can miss several factors that have been associated with ketosis in their herds.
A complete strategy to prevent or to reduce the incidence of ketosis in dairy cattle includes good nutritional and management practices from dry off to postpartum . Good practices include feeding good quality forage and balanced diets, supplementation of glucose precursors, minimizing stress, monitoring BCS at dry off and calving (avoiding over weight cows at calving and prevent big changes in BCS over this period) and eliminating any factor that can reduce dry matter intake. All of these practices must be implemented not only postpartum but during the entire transition period. Monitoring the health of fresh cows and also the health of cows in close up pens is an important practice for the success of the herd ketosis prevention strategy.
Ketosis is one metabolic disease frequently observed in high-producing herds.
Ketosis usually occurs within a few days to a few weeks after calving. It is characterized by low blood glucose, excess ketone bodies in blood and urine, lack of appetite, either lethargy or excitability, weight loss, depressed milk production and occasionally, in cases of severe ketosis, incoordination and neurologic signs.
Based on various reports, the incidence of clinical ketosis can range from 2 to 15 percent and subclinical ketosis from 9 to 34 percent.
Any factor resulting in a reduction of dry matter intake (DMI) increases the risk for ketosis. Around calving, lactating dairy cows naturally decrease DMI due to the advanced stage of gestation, as well as metabolic changes which occur in this period.
This decrease in DMI typically leads to NEB. During the last week of fetal development, the fetus uses approximately 46 percent of maternal glucose. The onset of milk production makes this energy shortage even more remarkable.
When lactation starts, the mammary gland requires a large amount of glucose for lactose milk synthesis. It is estimated that the mammary gland consumes 60 to 70 percent of the whole body glucose, mainly for lactose synthesis. In this case, a cow producing 66 pounds of milk per day uses at least 3.3 pounds of blood glucose to synthesize milk lactose.
The high energy demand during this period of glucose shortage triggers a compensatory process of nutrient partitioning and fat mobilization. During this period of glucose shortage, fat is mobilized as an alternative source of energy.
It is used as a fuel for basic cell functions in addition to providing energy to maintain milk production. In the process, ketone bodies are produced and the excess is eliminated in the urine and milk.
Several studies have described deleterious effects of ketosis on animal health and reproduction. Clinical ketosis is associated with an increase of two to three days to first service and a 4 to 10 percent reduction in pregnancies per A.I. at first service.
Other researchers have identified an association between ketosis and an increased incidence of ovarian cysts. Body condition score (BCS) has been linked to metabolic changes during the postpartum period. An elevated BCS at calving is a major risk factor for ketosis.
Cows with elevated BCS at calving (BCS ≥ 4.0) had elevated levels of circulating ketone bodies in plasma. They were at the highest risk of developing clinical and subclinical ketosis compared to cows classified as either a moderate or thin BCS prior to calving.
Ketosis is a disease with a severe impact on animal performance and consequently on the economic well-being of dairies. Prevention usually is less costly than treatment associated with production losses. Due to the increased energy demand required before calving, strategies to prevent metabolic diseases must focus on the nutritional management of the dry and transition cow.
The goals of these diets are to provide all required nutrients and to adapt the rumen for future diet changes as cows advance through these lactation stages. To prevent metabolic disorders, diets must be properly formulated to accomplish this goal and to minimize DMI reduction.
Managing BCS towards the end of the previous lactation is an important management practice to minimize ketosis and other postpartum metabolic diseases. PD
References omitted due to space but are available upon request.
to email an editor.