Department of Dairy Science, Virginia Tech, Blacksburg, VA 24061-0315 U.S.A.

For successful transition from the dry period to lactation it is important to maintain nutrient intake pre- and post-calving by using digestible rations that are palatable and nutritionally balanced. Control of potassium and sodium intake is important in preventing metabolic disorders. Use feed additives selectively to stimulate intake and/or digestion, prevent fall of blood calcium, and maintain a strong immune system.

Dairy animals go through many transitions during their lifetime. Birth, weaning, and calving would be considered to be the more stressful events encountered. Certainly birth and the introduction of the first feed (colostrum) is important for the survival of the calf. Transition from liquid to solid feed is the next major transition and is usually associated with going from separation to grouping with other animals. Change in feed and grouping should not be done at the same time with younger animals. Calving is the time of major transition for cows. This period is defined as a couple of weeks before calving to two to four weeks post-calving.

Goff and Horst (4) state that three basic physiological functions must be maintained around calving to avoid metabolic and infectious diseases. These are:

1. Adaptation of rumen to rations high in energy.
2. Maintenance of blood calcium.
3. Maintenance of a strong immune system.

Most feeding programs now attempt to adapt the rumen to feeds that are high in starch and energy by having a steam-up or close-up group of dry cows that receive some of the feeds that are fed after calving. These usually are fed for approximately two weeks before calving. Goff and Horst (4) suggest this may not be adequate time for rumen papillae to be transformed and five weeks may be needed to gain increased papillae size in order to increase VFA absorption and prevent decline in rumen pH after calving. Maintenance of blood calcium is difficult at calving because of the large drain of calcium into milk. Feeding strategies have been developed to minimize this condition and certain feed additives such as anionic salts may help. Also nutrients such as vitamin E and selenium have been implicated in maintaining a strong immune response and increased resistance to mastitis.

Maintaining intake at calving is important in preventing problems from developing. Bertics et al. (1) prevented the feed intake depression at calving by placing feed manually into the rumen. The result was increased milk fat percent and a tendency for increased milk production. Feeding an energy dense, more digestible ration might be desirable. A study currently being conducted by French and James (3) addresses this issue. The table below contains observations on intake prior to and immediately after calving for Holstein and Jersey cows.

The National Research Council (7) gives only one set of guidelines for dry cows and no consideration to those close to calving. Early lactation is considered independent of level of milk production. Nutritional consultants and dairymen have been modifying these recommendations and many have established nutrient guidelines for close-up dry cows. In table 2 I have the NRC suggestions for dry and early lactation cows as well as what six high producing (9,950 to 13,994 kg/lactation) Wisconsin herds are doing (5).

Wisconsin herds were feeding more net energy, protein, calcium, and potassium than the dry cow diet NRC would recommend, probably trying to replenish body condition and accommodate high milk production. Also the Wisconsin herds were feeding more energy, protein, and calcium to the close-up dry cows (within 2 weeks of calving) than to far-off dry cows. They all had a transition ration for cows before calving and nutrient concentrations are intermediate between what they fed the far-off cows and early lactation NRC. All herds used anionic salts in their transition ration and this is the reason the calcium is elevated in the transition diets. Without anionic salts this much calcium would be undesirable. Also the herds were able to keep potassium levels down to acceptable levels, a problem with many dry cow diets.

The nutrient levels in rations for the Wisconsin herds are not used to indicate right or wrong, only that some ration modification is being made to accommodate transition cows. This is not unlike what I see in many Virginia dairy herds. Also looking at the ranges suggest that not all are doing the same degree of modification. However, they are feeding more energy and protein to both far-off and close-up cows than the NRC suggests. A new NRC is currently being studied and will most likely take transition cows into consideration.

Recent research and observations have indicated that potassium can be a concern when feeding dry cows, especially close-up dry cows. Forages are frequently high in potassium and manure application can contribute to these high potassium levels. Forages with greater than 3% potassium should be avoided as the primary feed for dry cows. Grass pastures and hays can fall into this range. Feeding other feeds such as corn or soft dough barley silage might be helpful because grain (corn or barley) is lower in potassium than the leaf or stem.

It is possible to calculate the cation-anion difference for feeds. Below is an example of the calculations for a grass hay.

Table 3 has values for other feeds.

 Remember that as the level of potassium increases so does the CAD as long as the other minerals stay constant. A grass with 3% potassium would have 14 more milliequivalents than the grass used above. When forages with high potassium levels are used it becomes difficult to add enough anionic salts to be effective because the salts are unpalatable. Dilution of the high potassium forage with feeds containing less potassium becomes necessary. The Wisconsin herds used in table 2 were able to do this and had potassium of 1.36% in the close-up and 1.78% in the far-off group. They did this by using feeds such as corn silage for both far-off and close-up groups and limiting grass hays and silages. Also, grains were used in most close-up groups.

As discussed, certain feed additives have the potential to be of assistance during different phases of the transition period. However, they should be targeted to address a specific concern. Many are expensive and add significantly to ration cost. In Table 4 I have listed several feed additives that may have potential of improving performance. They are not for use in all cases or in all situations. I have attempted to give an idea of where these additives could be used.

Propionate is used by the cow to produce glucose and can be in short supply during transition periods. Since glucose is needed to produce energy less fat might be mobilized, a desirable condition. A recent study (9) found that cows fed calcium, zinc, and copper propionic salt three weeks before calving to three weeks after calving consumed more dry matter and mobilized less fat. No increase in milk production was observed, however. More research is needed to determine the best feeding sequence (pre- and post-calving or only post calving) and the relative economics.

Fat generally is not added to dry cow diets. However, many cows are switched after calving to rations that have added fat. This is acceptable but may not be ideal. Cows tend to reduce intake with added fat to maintain a constant energy intake. This may delay cows from reaching maximum dry matter intake and optimal rumen function. Some larger dairy herds have a post-calving ration to be fed for 10 to 14 days. This ration is high in protein, minerals, and vitamins, but contains no added fat. The goal is to get cows eating with a nutrient dense ration and then switch them to one with fat. Smaller herds probably can not justify this extra group.

Propylene glycol has been used as a drench for early lactation cows to increase blood glucose and reduce ketone production. Shaver (8) indicates that it can be used in the grain mix at 3 to 6% without feed intake depression. There is no indication it is effective if given before calving.

Protected amino acids and/or rumen resistant protein are similar because the logic is to supply a limiting amino acid to the dairy cow without it being degraded in the rumen. Protected amino acids are relatively expensive, but Shaver (8) indicates they may be more economical if used during the transition phase rather than throughout lactation. Indications are it would cost $.20 to .40 per cow per day to feed during the transition phase, both pre- and post-calving. Because of this cost some nutritionists have attempted to supply amino acids via natural ingredients. It is not clear if there is a consistent response to rumen resistant protein if fed during the dry period.

Sodium bicarbonate and sesquicarbonate are rumen buffers that are effective when used on high grain diets with a lot of starch and fermentable carbohydrates. In other words fresh and high producing cow rations. Cost is usually less than $.10 per cow per day. Do not feed to dry cows, especially close-up dry cows. Sodium is similar to potassium and might lead to increased milk fevers. Certainly we would not want to use with anionic salts. Salt or sodium chloride contains both a cation (Na) and an anion (Cl) and would not have the same effect. Some salt to dry cows is acceptable as long as intake is controlled.

Yeast has been a benefit in transition rations in some trials and not others. A recent study by McCoy et al. (6) found that yeast culture started at two weeks before calving resulted in increased dry matter intake before and after calving. Also milk production was higher and weight loss less. If yeast does stimulate dry matter consumption of transition cows it would be a desirable compound to include. Cost is usually less than $.10 per cow per day.

Microminerals and vitamins are not listed in Table 4. These certainly are needed to supply nutrients in many pre- and post-calving rations. Rations should be balanced and supplemented according to needs and feeds available.