by Carl E. Coppock, B.S., M.S., Ph.D., P.A.S.

HEAT and especially HUMIDITY are major depressants to high yields

Recall this analogy from Dennis Armstrong: "A cow is a little furnace". The greater the feed intake, the hotter the furnace. As body temperatures increase, cows respond by reducing their feed intake, probably a protective mechanism. Lower feed intake is the primary reason for the decline in milk production in hot weather.

In summer, the modern dairy cow does not belong in the sun anywhere across the southern US. So shade is the first priority, followed by fans and sprinklers, the more the better in most cases.

During summer, cows will produce about as much milk as the heat stress management allows them to produce. Dairy cows are bred to be heat-generating animals, metabolic thoroughbreds that punish themselves with elevated body temperatures and sharply increased respiration rates in order to sustain the high yields they were bred to produce.

If continuing increases in yields are to be sustained, producers must assist cows to avoid the high radiant heat of summer and to dissipate the large amount of heat they produce.

The TRANSITION COW

Defined as the time interval 3 weeks before and 3 weeks after parturition, this period is the most critical time in the lactation cycle of the dairy cow.

It may be a difficult management problem, but a close-up dry cow group is worth the effort, because of the special needs of the cow at this time and the positive influence which good care will have on the events at parturtion and for future lactation.

With respect to the use of anion salts for this prepartum time, use of low potassium ingredients will reduce the amount of salts needed. Corn silage and wet brewers grains are examples of low potassium ingredients, although use of feeds similar to those the cow will receive postpartum is also important.

Even in the absence of a problem with milk fever, the use of anion salts can be justified.

Careful thought should be given to reducing all types of stress on the near partum cow. These include many forms of environmental stress, as well as social stress.

BYPRODUCTS/COPRODUCTS

The cow converts many byproducts from the food industry to nutritious milk and meat. Nine byproducts used in California provided at least 31% of the energy and protein for the milk produced there in 1992. It is probable that nearly all dairy cows receive at least one byproduct in their rations.

Some byproducts have special value; for example, citrus pulp with about 25% pectin is especially useful in rations based on corn, because pectin does not lower pH or result in additional lactic acid production in the rumen.

The 2 best forage substitutes are whole cottonseed and cottonseed hulls.

The big challenge for nutritionists is to determine the most appropriate net energy value to assign to the various byproducts.

MILK ADULTERATION

Several cases of milk adulteration at the farm level have occurred within the past 5 years in the U.S. which clearly indicate the importance of this problem to the dairy industry. Indictments have been handed down to dairy producers, truck drivers and in at least one case, to a milk plant employee. For many years the cryoscope has been used to detect added water, but when salt is included with the added water, the cryoscope is no longer useful for its intended purpose. Therefore, all milk receiving plants need to develop a very careful plan to detect adulterated milk and to identify those responsible. More extensive analyses will be necessary, but the tools are available to detect increasingly sophisticated forms of milk adulteration.