Many dairy producers have experienced this situation at some point. A particular cow comes into early lactation with a lot of potential for good milk production. She may have come into the barn in a little thin, but starts literarily pouring out milk. Within a couple of weeks, she starts to falter in milk production and health, but after given some intravenous therapy seems to snap out of it.
Months later, the producer is forced to dry her up before she completes an entire lactation cycle. There is a good chance that she is a victim of metabolic disease. It is a trap many promising dairy cows can avoid with sound changes to their feeding programs, even before they calve and began milking.
Early-lactation dairy cows are more susceptible than modest-producing and later-lactation herdmates to metabolic diseases such as ketosis and related conditions from a week to months after calving. Not all energy requirements for their high milk production can be secured solely from the dairy diet. These cows are drawn into a period of severe “negative energy balance” for about six weeks after calving.
In itself, the roads to most ketosis affecting severely energy-short dairy cows relates back to a complex chemical imbalance that occurs when dairy cows cannot get enough of a basic energy block called glucose. It is the simplest sugar in cattle metabolism but it essentially drives all maintenance and production activities requiring energy in the dairy cow.
When feed carbohydrates are in short supply, the dairy cow will burn her own body fats in which non-esterified fatty acids (NEFAs) are formed. They can be reconfigured into glucose.
In less demanding times, NEFAs are commonly used to support liver functions and to provide fatty acid chains for milkfat production. However, when the intake of carbohydrate-derived energy is so limited, the cow may suffer from rapid body fat mobilization and weight loss.
Too many NEFAs are produced for glucose transformation and a good portion of these NEFAs end up as poisonous ketone bodies. It is these circulating ketone bodies that lead to a toxicity associated with both clinical and sub-clinical ketosis in early lactating dairy cows.
Research shows that the natural incidence of overall ketosis in a well-managed dairy herd is less than two per cent, while problematic herds exhibit about six per cent actual clinical ketosis, and upwards to 60 per cent hidden or subclinical ketosis.
It is most prevalent at the start of lactation and traditionally has been observed in obese animals (BCS > 4.5), but also can be present in animals of modest body condition as well (BCS of 3.5). These cows tend to demonstrate a strong correlation between rapid loss of weight after calving and the presentation of ketosis often triggered in the post-partum period by poor dry matter intake, inadequate dietary energy, poor feed digestibility, digestive upsets (sub-clinical acidosis) or a hormonal imbalance affecting energy metabolism in the cow. Some studies on ketosis suggest that a general energy deficit/rapid fat mobilization may occur in dairy cows even prior to calving.
NEED TRANSITION DIET
In an attempt to prevent ketosis, producers should implement a proper transition diet (three weeks before cows calve and three weeks post-partum) in order to promote good dry matter intake and a body condition score of three to 3.5 in susceptible dairy cows.
Early lactation rations should be formulated to maintain good rumen function (re: effective forage fibre) and yet carry enough available dietary energy to support the demands of increasing milk production. The goal is to build up dry matter intake in early lactation cows to about 3.5 to four per cent of their bodyweight at about nine to 10 weeks after calving.
Built on a DMI foundation of 11 to 13 kg, the transitional energy and protein levels are denser than faraway dry cow diets, but do not quite match the early lactation diets. A typical close-up ration should contain about 0.70 Mcal Nel/kg, 14 to15 per cent protein, and balanced for the recommended levels of macro-minerals (watch out for potassium that causes milk fever) and trace minerals plus vitamins (particularly selenium and vitamin E).
The actual ration should contain no more than 2.5 to 3.5 kg/head/d of grain such as barley or corn. It might also have at least 2.5 kg to four kg of long-stem grassy-type hay. Some producers may also incorporate three to five kg (DM basis) of the early lactation TMR diet. It also cannot be overemphasized that any feedstuff fed to these cows should be highly palatable, digestible and free of moulds and mycotoxins. Clean water should also be always available.
PROPER BUNK MANAGEMENT
Tying it together is good bunk management for all good feeding programs set up for both the close-up- and early-lactation dairy cows. This means each cow should have enough bunk space and adequate time to eat. A properly mixed ration should be put in front of the cows, pushed up frequently and old feed removed. It is a matter of implementing any practice that will get dairy cows, before and after calving, to eat that extra kilo of feed to achieve her essential energy requirements.
The importance of energy in all aspects of dairy nutrition, especially for early-lactation cows cannot be overstated. We tend to forget that energy is the single largest requirement for high milk producing dairy cows. Failure of providing enough dietary energy often leads to metabolic disease such as ketosis in post-partum cows, and although treatable, some of the most afflicted cows seem to disappear from the herd. On the other hand, prevention with good transition diets and assurance of good energy status in the dairy herd throughout the year underlies healthy cows and their production of consistent, large volumes and profitable milk. †