Source: Ontario Ministry of Agriculture, Food and Rural Affairs
Fact Sheet written by:R. Parker – Dairy Cattle Specialist/OMAFRA
There are six key times during the yearly cycle when each cow should have her condition evaluated. These occur: midway through the dry period, at calving, and at approximately 45, 90, 180 and 270 days into lactation. The timing of the checks coincides with the time for making important decisions about the future feeding, breeding and health management of the cow. The following describes specific goals with regard to body condition for each stage of the lactation cycle.
The goal for ideal body condition score for the dry cow is 3.5. To achieve satisfactory health and performance early in the subsequent lactation condition score must fall between a minimum of 3 and a maximum of 4.
It is a well accepted fact that cattle, replenish body fat reserves more efficiently while lactating than during the dry period. Occasionally a cow must be dried off before an acceptable condition score is reached. It will pay the manager to continue to feed underconditioned dry cows for gain, to achieve a desirable body condition score. Obviously, a well managed feeding program combined with frequent observation is required to achieve condition gain without overfattening the dry cow.
Average quality, long stemmed grass hay has proven to be the ideal forage for the dry cow. Higher quality (energy and protein) forages, such as corn silage and alfalfa haylage, must be limit fed to prevent excessive condition gain. With correct forage quality and quantity, a low-energy high-fiber supplement, containing appropriate protein, mineral and vitamin levels, could be fed in controlled amounts to achieve the desired amount of gain.
Removing excess fat from overconditioned cows by limiting energy intake during the dry period does not appear to seriously impair subsequent performance.
The cow should be evaluated frequently during early lactation. It is then that body condition, as it reflects energy reserve, has its greatest impact on the health, production and fertility of the dairy cow.
The cow freshening overweight, with a condition score of more than 4, is at greater risk of fat cow syndrome problems such as difficult calving, retained placenta, metritis, mastitis, displaced abomasum, ketosis and milk fever. Her immune response is usually inadequate to combat the stress of calving and appetite is less than ready to meet the demands of early lactation.
Another situation occurs when the cow starts lactation without enough energy reserve, having a condition score of less than 3.
This cow may experience fewer health problems at calving but her later productive and reproductive performance will be less than expected.
As shown in Figure 1, the average cow commonly peaks in milk production at 4 to 6 weeks into lactation. Her feed (dry matter) intake lags behind, normally peaking at about 9 to 11 weeks. This situation puts the cow in a negative energy balance for several months in early lactation. This means that feed energy intake is less than milk energy output. The cow uses available body fat (tissue energy) reserves to cover the shortfall.
Figure 1. Typical Energy Curves for the Lactating Dairy Cow.
The cow starting lactation in thin condition lacks adequate energy reserve and she will peak at a lower milk yield. Peak milk yield is directly related to total lactation yield with mature cows. For each additional kilogram of milk at peak there will be approximately 200 more kilograms of milk over the whole lactation. Undercondition at calving is also a cause of low milk fat test. In early lactation, a high proportion of milk butterfat precursors originate from body fat stores.
The average mature cow calving in desired body condition, with a score of 3.5 (4 maximum), and in good health, can be expected to lose between one-half and one kilogram of body tissue per day during the first 60 to 80 days in milk.
One kilogram of body tissue (mostly fat) can supply 4.92 megacalories of energy (NEL) . At 3.5% butterfat, milk contains about .69 megacalories of energy (NEL) per kilogram. Therefore, one kilogram of body tissue can provide the energy to produce 7.1 kilograms of milk. The loss of 70 kilograms of fat by the average mature cow translates into the production of nearly 500 kilograms of milk – over than supported by feed energy intake.
During the first two months in milk the average mature cow will drop between 1/2 and 1 full point in condition score, stabilizing at a score near 3 by the 10th week and beginning to regain lost condition by the 90th day. At this time, rising feed energy intake can satisfy the declining milk energy demand. This coincides with the optimum period for observation of regular estrous activity, breeding and conception.
Experience and research have shown that cows gaining weight (in positive energy balance) at the time of service have a higher conception rate than cows losing weight. A condition score between 2.5 and 3.5 would indicate adequate condition for good reproductive efficiency.
Very high producing cows may drop to a score near 2.5 before stabilizing, having lost up to 1.5 kilograms of tissue per day. They may be into the 4th month of lactation when this occurs. The expression of estrus and fertility may be suppressed in these cattle, resulting in delayed conception. Cows with good production that demonstrate no or little condition loss in early lactation are most likely very efficient feed converters. Cows that gain condition at this stage are probably poor producers.
Low energy intake in early lactation can lead to excessively high rates of fat mobilization of greater than 1.5 to 2.0 kilograms per day. This increases the risk of the accumulation of fat in the cow’s liver, and can lead to ketosis, increased susceptibility to disease, a delayed return to estrus and reduced fertility.
The feeding program for cows in early lactation must therefore be carefully managed to achieve maximum dry matter intake and ration digestibility. Adequate amounts of protein are critical to stimulate intake and provide nutrients (amino acids) for milk production. The cow has limited body protein reserves to draw from.
Cows in early lactation will consume about 10% less dry matter than cows at the same level of production in mid-lactation. Therefore, providing enough protein to meet the requirement for peak milk means that the ration protein content will be in the range of 18 to 20% of the dry matter. Ideally, 40% of the protein should bypass rumen degradation and provide the amino acids that are limiting to milk production.
A compromise must be met between providing the fresh cow with large amounts of highly digestible and rapidly fermented grain starch for energy and providing adequate forage fiber to maintain rumen function and butter-fat synthesis.
The ration should be formulated to provide 72 to 75% Total Digestible Nutrients (TDN) or 1.61 to 1.67 megacalories per kilogram of Net Energy for lactation (NEL) . Total ration fiber levels should be between 19 and 21% acid detergent fiber (ADF) and between 25 and 28% neutral detergent fiber (NDF). A minimum of 21% of the total ration dry matter should come from forage NDF. Ideally some of the forage should be in the form of hay to provide stimulation for optimum rumen function.
Mineral and vitamin levels in the ration should be balanced to currently recommended standards.
Following recommended feeding management practices will also help maximize dry matter intake, eliminate the risk of cows going off-feed, and reduce the cow’s dependence on body fat reserves.
These practices include:
- lead feeding grain to the dry cow for 2 weeks, increasing to a maximum of 1% of body weight at calving,
- challenge feeding grain and protein supplement to the fresh cow, increasing gradually to the recommended maximum advised by ration formulation, by three weeks into lactation,
- feeding concentrates in meals of less than 4 kilograms, more frequently (i.e. 4 times) per day,
- feeding the highest quality forages available,
- following the feeding sequence of forage before grain and grain before protein supplement, ideally with some time delay between, for optimum ration digestibility,
- feeding more often when rapid feed spoilage is a problem,
- keeping mangers and water bowls clean and free of hazards,
- chopping forages to maintain adequate particle size (greater than 1 cm) and processing concentrates as coarsely in texture as possible to stimulate rumen function and feed consumption,
- using molasses to improve the intake of unpalatable or dusty feeds,
- using buffers, such as sodium bicarbonate at .75 to 1.0% of total dry matter intake, to improve the digestibility and intake of high concentrate rations,
- adding .5 to .75 kilograms/day of rumen protected fat to the cow’s ration to increase the energy density while reducing the need to rely on starch as the primary source of dietary energy. When adding fat to the ration, calcium and magnesium levels need to be raised to 1.0% and .3%, respectively, and attention must be given to providing adequate bypass protein and functional fiber in the ration.
Adding 6 to 12 grams of niacin to the ration during the lead feeding and throughout the early lactation period will help high producing cows that freshen in desired or heavy body condition to use dietary fat and body fat stores more efficiently.
At about 180 days in milk, a body condition appraisal should confirm that cows are replenishing body fat reserves that were lost in early lactation. By this stage of lactation, condition scores should be approaching 3 for the highest producing cows in the herd and between 3 and 3.5 for the average producing cows. Below average cows may have already exceeded a condition score of 3.5 and will need to be fed carefully to prevent fattening. All cows being rebred should be confirmed pregnant by mid-lactation.
The condition score check done at approximately 270 days in lactation should show the average cow approaching a score of 3.5. During this period, low producing cows tend to become over-conditioned, showing scores at or above 4. This occurs more often where large amounts of corn silage are fed and where attention is not paid to limiting access to concentrates. Cattle fed grain in milking parlors should be allowed sufficient time to clean their share, leaving none behind for the next cow that occupies the stall. In tie-stall barns, manger dividers may be needed to prevent cows from stealing unneeded grain from immediate neighbors.
Overconditioning also happens in free-stall herds fed total mixed rations where the cattle are not adequately grouped according to production. At least 4 and perhaps 5 lactation groups; early, mid, late, first-calf, and dry may be needed to prevent overconditioning.
In herds where extended calving intervals prolong the period of low production and/or the dry period, many cows will become overfat. In this situation the breeding management needs to improve.
Very high producing and persistent cows, like first-calf heifers, with normal calving intervals, may be difficult to get to the goal of 3.5 in condition score while still milking. With these cows, it may be necessary to continue to feed for gain during the dry period to frilly recharge their energy reserves.
The ideal condition score for the heifer calving for the first time is about 3.0. Heifers freshening with condition scores in excess of 3.5 have experienced more calving difficulty.
First-calf heifers need to be managed somewhat differently from their older herdmates. They will calve with 100 to 150 kilograms less body weight than the older cows in the herd. Their daily concentrate amount must be adjusted accordingly to maintain correct forage-to-concentrate ratios to prevent problems related to digestive system malfunction.
The lactation curve of a first calver does not show the early high peak that higher lactation number cows demonstrate. Therefore, the negative energy balance occurring in early lactation will not be as demanding on body fat reserves as it can be for older cows.
First-calf heifers do show greater persistency of lactation than older herdmates. The first calver will show an average drop of 4% per month in mid-lactation compared to 8% in older cows. In late-lactation, the first calver will fall in milk at 6 to 8% monthly while the higher lactation number cows are declining at 10 to 14%. This greater persistency means that the heifer cannot route as high a proportion of energy intake as can her older herdmates toward the replenishment of body fat stores.
First and second-calf heifers also have a major additional need for energy – for growth – throughout mid-and late-lactation and the dry period. These cattle must gain 50 to 75 kilograms during each of the first two lactations to reach mature body weights.
To ensure that the additional nutrients needed for growth are provided, the standard recommendation has been to feed more concentrates to these cattle. During the mid-and late-lactation phase the first calver should get 10% and the second calver 5% more concentrates than required for milk and body condition gain.
Failure to provide these extra nutrients may be the cause of heifer “burn-out”. Today’s genetically superior cattle can produce large volumes of milk, even during their first lactation. If special care is not provided, they will begin the second lactation stunted and/or lacking adequate energy reserve.
With the mature lactation curve, typical of second lactations, adequate tissue energy reserves are critical to achieving desirable peak milk yields as well as satisfactory butterfat synthesis. Body size is a major factor influencing dry matter intake. Lack of sufficient growth will limit the improvement in feed intake needed to support higher milk yields.
As a result of inadequate management the genetically superior heifer could demonstrate poor second lactation performance or burn-out, and may be wrongly culled.
Correct management of energy balance throughout the lactation and reproduction cycles of the dairy cow can significantly improve her capacity to generate profit.
OMAFRA Factsheet Body Condition Scoring Of Dairy Cattle, Agdex 414/10 provides illustrations of specific conditions scores.