Total mixed rations (TMR) continue to expand in use on dairy farms. A 1993 Hoard's Dairy survey reported that 29.2 percent of surveyed U.S. dairy farms had adapted this system of feeding dairy cows.

Lactating cows spend 10 or more hours per day chewing. Chewing is accompanied by secretion of saliva which helps buffer ruminal fermentation. Chewing is also responsible for most of the particle size reduction required before digesta passes from the rumen. Maintaining stable fermentation in the rumen is needed to optimize dry matter intake, milk production, and milk composition.

During the past decade, Americans have become increasingly health conscious. Reports in the media have highlighted recommendations from the medical community and government agencies that people decrease their intake of saturated fatty acids because of the purported relationship of saturated fatty acids with atherosclerosis. In particular the saturated fatty acids myristic and palmitic acids may increase plasma cholesterol in humans; however, the saturated fatty acid stearic acid may not affect plasma cholesterol.

Milk is a source of nutrition which provides amino acids, carbohydrate, fat, vitamins and minerals. Milk also contains a number of enzyme activities which may act upon these components and alter the biological nature of milk. One group of enzymes found in milk is the proteinases which breakdown proteins into smaller fragments.

The use of BST (bovine somatotropin) to stimulate milk production by the dairy producer has gained increasing acceptance since its availability in February, 1994. Considerable amount of research has been reported showing increased milk production when BST was injected at 14 day intervals in lactating Holstein cows.

Dairy cattle breeding has changed tremendously during the past century. What may be some of the changes during the next 25 years? Twenty-five years is not much time in terms of generation interval in dairy cattle.

Dairy production in New Zealand is recognized as one of the most efficient in the world. It has to be efficient because it is neither subsidized by tax-payers nor undergirded by governmental price supports.

The key management strategy in producing high quality alfalfa forage for lactating dairy cows is to select the optimum harvest date for the first cutting. Second and successive cuttings should then be harvested every 28 to 30 days thereafter.

Prilled saturated fatty acids and calcium-salts of long-chain fatty acids (Ca-LCFA) have been shown to be effective ruminally inert fat supplements for high producing dairy cows. Recently, hydrogenated palm fatty acid distillate (HPFAD) has become available in this country.

In situ fermentation studies are routinely used to evaluate ruminant feeds. Hydration is known to be necessary for enzymatic digestion and to affect microbial growth. For alfalfa, corn cobs, orchardgrass, and wheat straw, hydration has been shown to be the least rate-limiting step of digestion.

Jersey producers in areas of cold winters have expressed concern about poor growth and survival of young Jersey calves housed in hutches during the winter. Cold temperatures alter digestive processes and increase energy needs for maintaining body temperature, resulting in increased nutrient requirements of calves.

Despite substantial progress, birth-to-death identification, including birth date and sire, continue to be problems for genetic evaluation of dairy cattle. Meinert and Norman reported that the percent of official DHIA records that were usable for genetic evaluations was 43.9% in 1968, 49.9% in 1979, and 63.8% in 1990.

There has been much discussion recently on the competitiveness of dairying in the Midwest. Attention is usually focused on producing milk at the lowest possible cost. Profit-conscious dairy managers should know what it costs to produce a hundred pounds of milk.

As production of milk and milk protein by dairy cows increases, research has focused on increasing the supply of amino acids to high producing dairy cows. Methionine has been identified as one of the most limiting amino acids for the synthesis of milk and milk protein by dairy cows.

High producing dairy cows have a tremendous requirement for energy that must be met if the cows are to attain and maintain milk production equivalent to their genetic potential. To meet these energy demands, many dairy nutritionists include supplemental fat in the diets fed to high producing cows.

Profitability can be defined as the difference between income minus expenses. Income over feed costs focuses on milk yield (income) and feed costs (expenses). Maximum milk yield is not always most profitable, but nutrient costs for maintenance are the same if cows produce 20 or 40 kg of milk.

Illinois dairy managers have had BST (bovine somatotropin) available since February of 1994 as a tool to manage the milk lactation curve and improve the profitability of their herds. BST technology has been extensively researched and studied which has provided valuable knowledge to producers.

The dairy industry continues to face challenges and uncertainty. The number of Illinois dairy farms is declining every year. Between May, 1993, and May, 1994, there were 201 fewer dairy operations, representing an 8 percent decrease.

Through the use of genetic engineering it has become possible to consider making substantial changes in the composition of milk utilizing transgenic animals. In this report we discuss the development of DNA vectors that will cause the production of modified versions of bovine ß-casein in the milk of transgenic mammals.

Milk production per cow continues to increase 2 to 3 percent annually. Genetic improvement accounts for 33 to 40 percent of this increase while feeding and management contributes the remaining 60 to 67 percent.

Dairy production methods are undergoing some major changes in the Upper Midwest. One end of the changes is an increase in herd confinement, with expansion of herds from 100 to 400-500 cows.

Adding fat to the diet of high producing dairy cows has become a common practice for most high producing herds (Table 1). Energy demands exceed energy intake for 80 to 100 days postpartum.

The use of electrolyte solutions is a popular and successful method to provide oral rehydration therapy for scouring calves. Some recently developed products include soluble and insoluble fibers and gelling agents in their formulations.