- Jin Gan
Feeding High Yield Milk Cows While Maintaining Milk Yield And Fertility
In recent times, the main priority for dairy farmers is to increase the milk yield for cows. With that being said, high milk yielding cows can be associated with poor fertility, increased disease incidence or more lameness. These problems however, are not inevitable. The challenge is to meet the nutritional needs of the cows.
Nutritional needs of high yielding cows
They require high energy and nutrient intake
A very high energy diet fed as much and as often as desired
A well balanced diet to avoid any excesses or deficiencies
How much does a cow eat? There are normally a few factors that will affect the dry matter intake (DMI) of the cow. These include physiological, environmental, management and dietary factors. In general, dairy cows will consume around 1.4% to 4.0% of their body weight daily depending on the quality of feed.
Physiological factors affecting feed intake
The size of the cow as well as the body fat are important factors when trying to predict the feed intake of a cow. Other factors such as sex, age and if the animal is dry or lactating. A lactating cow will eat 40-60% more than a dry cow. The age of the animal also affects the intake. Generally, older cows tend to eat more compared to younger cows.
Environmental factors affecting feed intake
The environment temperature has a big impact on the feed intake for cows. Feed intake can increase up to 30% in colder temperatures or decrease up to 30% under hotter temperatures. Adverse weather conditions such as snowing could also decrease the feed intake by 15%.
Management and dietary factors affecting feed intake.
Nutrient deficiencies can decrease the feed intake up to 10-20%. Growth promoting implants are able to help increase the feed intake.
Before peak, the cow is in "negative balance". They return to positive balance after peak, allowing them to start ovulating and returning body reserves. "Negative energy balance" is defined as the amount of energy that the diet is lacking compared to the need of energy that is required for milk production. In the figure below, the grey shaded area between milk energy and maintenance and feed energy represents the amount of "negative energy balance".
Body Condition Score (BCS)
First, let us define what is body condition scoring (BCS). BCS is a method of evaluating fatness of thinness in cows according to a 5 point scale. The score can be used to fine-tuned dairy herd nutrition and health. Body condition plays a big role in the productivity, reproduction, health and longevity of dairy cows. By observing the thinness and fatness of a cow, we are able to tell if there is any sort of nutritional deficiencies, health problems or improper herd management. BCS is a good way to troubleshoot problems and improve the health, longevity and the productivity of the dairy herd.
For example, if the cow is fat, this may be due to poor nutrition or reproduction management. A fat cow is also more susceptible to metabolic problems and infections and therefore will have more difficulty at and after calving. Usually, over-conditioning occurs during the last 3 - 4 months of the lactation cycle when the milk production level has decreased, but the dietary energy and total nutrient levels have not been reduced accordingly.
When the cow is too thin on the other hand, this will cause lower production and milk fat levels. This is primarily due to insufficient energy and protein reserves to maintain the milk production level. Thin cows usually do not show heat or conceive until they start to regain, or at least maintain their body weight. Special care must be taken when feeding these animals in order to maintain production while increasing the body reserves.
As a summary for energy balance as well as BCS, prolonged periods of severe negative balance must be avoided. Also, the main factor affecting the loss of body condition is BCS at calving and not nutrition. Modern Holstein dairy cows are genetically thinner. Hence, cows with BCS of 3 or more at calving will generally lose 1 or more BCS units and would be at risk from poor health and fertility.