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Feeding, Health and Reproduction

Gordon King, Animal & Poultry Science, University of Guelph

Feeding Dairy Cattle

Forages

Dairy cattle consume a wide variety of forages in the form of grasses, legumes, corn and other green plants. These may be ingested as pasture, green chop, silage, haylage, hay or crop residues (straw, stover). High quality forages, determined by the nutrient content, digestibility and palatability of the plants, can improve productivity through reducing feed expenses and promoting efficient rumen function. When plants reach advanced stages of maturity, much of the hemicellulose-cellulose forming the cell walls is converted to lignin. This substance is almost totally indigestible by most organisms so mature plant yield considerably fewer nutrients than young, actively growing plants. Poor forage quality can be compensated for by feeding more cereal grains and protein supplements. However, excessive grain feeding is expensive and, if carried to extremes, may produce digestive disturbances.

Government supported or privately operated forage analysis laboratories function wherever intensive dairying occurs so the precise chemical composition and digestibility of feed ingredients can be determined. Farmers must be cautious, however, since proximate analysis, the most common form available, provides values on composition of the material tested but these do not usually indicate how much the consuming animal obtains when the material is fed. Accurate information on palatability and digestibility is essential before intake can be estimated and rations balanced.

Forage feeding methods range from grazing through traditional hand dispensing in older tie-stall barns to sophisticated, automated systems for those willing to invest in the latest technology.

The recent increase in cost for energy and concentrate feeds creates a need for better utilization of forages and a renewed interest in pasture-based dairying. Considerable information about pasture-based dairying is available on the Internet.

Concentrates

These ingredients represent relatively concentrated sources of energy or protein. Some additional processing such as rolling or grinding of cereals is often necessary to improve digestibility. Proper amounts of concentrate can only be determined after forage quality is known. Stage of lactation or growth must also be considered to calculate and dispense sufficient nutrients for maintenance and production (a generalization for early to mid lactation animals might be about 0.4 kg of concentrate per kg of milk).

A substantial proportion of the high biological efficiency obtained currently with dairy cows results from feeding by-pass nutrients. If concentrate prices increase dramatically, it will be necessary to use feeding system that satisfy requirements and promote productivity through maximizing rumen function.

The forage and concentrate components must be combined in appropriate amounts and fortified with appropriate vitamins and minerals to provide the balanced ration. Provision of potable water to meet needs is also vital.

Vitamins and Minerals

Dairy cattle need proper vitamins and minerals to satisfy the many demands of production-reproduction. With the exception of salt which is often feed free-choice, vitamins and minerals are usually provided as a premix added to the basic diet. Since calves, growing and pregnant heifers, lactating cows and dry cows all have somewhat different requirements, it is best to prepare individual rations for each group. Producers mixing their own rations must be careful to insure any small quantities such as vitamin-mineral premixes that are added get blended thoroughly with the other ingredients. They should also be aware that some vitamins may deteriorate quickly after mixing so the most stable forms should be used.

Water

Water is a vital nutrient for all animals. Provision of ample, potable water is essential for proper operation of any dairy unit. Any water source should be free of contamination and available ad libitum.

Feeding Systems

Many options exist. In general, types of forages grown, housing system and operator preference govern the choice. Many dairy cows obtain their roughage from grazing for at least some part of the year and stored forages for the remainder. Pasture quality can vary so extra feeding may be necessary when animals graze. The most common options for feeding confined animals on dairy farms are summarized as follows:

1. Hay, Silage and Concentrate Fed Separately

2. Single Forage and Concentrate Feed Separately

3. Feeding Part of the Concentrate with Forage

4. Total Mixed Rations

Dairy Cattle Nutrition

Calves. Newborn calves have little resistance to distress so care provided during the first few hours after birth is crucial for subsequent survival. No prenatal antibody transfer occurs in species such as cattle that have an epitheliochorial placenta. Thus, calves should ingest colostrum very soon after birth to acquire their initial immunity. Time and sanitation affect the success of antibody transfer. The potential for absorption of protein through the intestinal mucosa is high at birth and remains for up to 24 h if contamination by microorganisms is low. In contrast, if substantial numbers of bacteria are ingested before or with the first colostrum, this stimulates early gut closure and impairs subsequent absorption. Calves should be up and nursing within 0.5 h of birth and, unless the cow has been pre-milked or subjected to a short dry period, will ingest substantial immunoglobulins within the first few hours of post-natal life. The dam and calf should be separated within 24 h to reduce coliform exposure and suppress maternal instincts.

Perhaps the best way to feed newborn calves is by milking colostrum from the cow for administration by bottle, open pail, nipple pail, or one of the more complex feeding systems that are available. Any of these methods prove satisfactory provided the equipment is cleaned thoroughly between each use. Colostrum should be fed during the first three days with intake regulated to approximately 8% of body weight per day. Under feeding limits growth while overfeeding may produce gastroenteritis.

Occasionally, fresh colostrum is not available so alternate sources should be maintained. Surpluses can be stored frozen for prolonged periods or colostrum can be allowed to ferment, yielding a product that is stable for one month. Fermented (sour) colostrum should be buffered with sodium bicarbonate prior to feeding. Calves should continue to receive whole milk, milk replacer or colostrum until they reach 2 or 3 mo. Hay and calf starter should be provided during the second week with amounts gradually increased to encourage consumption. As the daily intake of solid feeds goes up, the amount of milk or replacer can be reduced so calves are weaned by 3 mo. Post-weaning rations must balance forages and concentrates to promote normal growth but to prevent obesity.

Heifers. Yearling heifers can satisfy most of their nutrient requirements from lush, actively growing pasture. Later in the season, however, when plants are mature and growth is slight, supplemental feed should be provided. If heifers are neglected at this time they may begin to lose weight and become acyclic. Provided the general nutrition program is adequate, this is perhaps the major factor contributing to delayed first calving. The Department of Animal Science at Purdue University provides a comprehensive guide for "Raising Dairy Replacement Heifers From Birth to Breeding."

Fresh Cows. Once lactation commences the nutrient demand in high producing animals increase substantially so the first two months after calving are the most difficult period for meeting requirements. For proper nutrition it is imperative that maintenance and production requirements are calculated for each individual. Healthy fresh cows should be introduced to the milking herd by 3 to 5 days postpartum. Concentrates must be increased gradually (0.5 to 0.7 kg/day) until the appropriate intake is reached. Special provisions are necessary during early lactation with all feeding systems to bring fresh cows up to full feed. Milk production rises rapidly for 6 to 8 weeks while voluntary feed intake increases gradually and usually peaks around 12 to 14 weeks. The lag in feed intake behind high milk production results in negative energy balance so maximum lactation is achieved and maintained at the expense of nutrients already stored in the body. This initial depletion creates the need for adequate replenishment of reserves in late lactation and the dry period.

After 10 or 12 weeks voluntary intake is usually adequate to fulfill requirements if a balanced and palatable ration is provided. Substantial concentrate should be fed during the first third of lactation to minimize the time when cows are losing weight and facilitate re-breeding. In the later stages of lactation more nutrients can be consumed than are required for reproduction (lactation and gestation) so positive balance ensues and weight can be regained. Some energy reduction may be necessary in late lactation to prevent obesity.

See "Guidelines for Feeding Dairy Cows" available through OMAFRA for comprehensive details on nutrition of dry and lactating cows. The Dairy Science Department at the University of Florida also has an extension publication covering "Nutrient Requirements of Dairy Cattle" available on the Internet through the Florida Agricultural Information Retrieval System (FAIRS). This latter link contains considerable information on the composition of common and not so common feedstuffs.

First lactation animals should receive an additional 20% and second lactation animals 10% over maintenance-production requirements to allow for the fact that they are still growing.

Feeding in the Early Dry Period. From termination of lactation until 2 or 3 weeks prepartum most cows can satisfy nutrient requirements from good quality roughage fortified with appropriate mineral-vitamin mixture. Thin cows should be provided with some extra energy supplement to allow recovery of body condition but gross overfeeding and associated obesity must be avoided. Small amounts of the concentrate or total-mixed-ration should be given in the last 2 or 3 weeks before freshening to allow adjustment to the postpartum ration. Comprehensive information on "Dry Cow Feeding and Management" is also available from FAIRS and the OMAFRA publication "Guidelines for Feeding Dairy Cows".

Body Condition Scoring in Dairy Herd Management. Body condition scoring of dairy cattle provides an excellent method for monitoring condition and adjusting nutrient intake to meet changing requirements throughout lactation and the dry period. OMAFRA provides an introduction into "Body Condition of Dairy Cattle" and instructions on "Using Body Condition Scoring in Dairy Herd Management" through their Internet site. A body condition scoring chart is also available from the School of Veterinary medicine at the University of Pennsylvania, with a further link to another series of instructions for implementation of a body condition scoring program in dairy herds.

Why keep dairy cows?

The main goal of any dairy herd is to produce milk as conveniently and economically as possible. Since the bovine gestation period is nine months long and cows require a postpartum recovery period of several months before initiating another pregnancy, it is convenient to plan around a yearly calving interval. Ideally, cows would lactate for about ten months followed by a two month dry period, as illustrated in the accompanying figure. They should be remated successfully during the first third of lactation, progress through another gestation and calve again to initiate another lactation. However, even with reasonable management, a substantial number of animals fail to conceive as anticipated so calving intervals exceed twelve months. Failure to achieve a twelve-month calving interval is not disastrous since almost all improved dairy cows produce reasonable quantities of milk for longer than ten months. Thus, although daily yields are considerably below peak amounts, they still return something over feed and maintenance costs. The actual calving interval for most herds with reasonable standards of management will usually range between 12.5 and 15 mo. Once the interval extends beyond this duration, most cows in the herd spend too much time in the lower portions of the lactation curve where the margin over feed costs is minimal or even negative. Also, in such instances, the average milk and offspring production per day of herd life is lower.

Dairy farmers seek consistently for methods to improve production efficiency (milk per unit of feed or per hectare of land cultivated) since, with high efficiency, the nutrients used for maintenance constitute a smaller proportion of the total intake. This requires close attention to the composition of diet for each production group, plus the method and frequency of feeding. Various procedures exist to enhance milk production but each must be evaluated for convenience, cost effectiveness and effect on animals and animal attendants before any are adopted.
 
Procedure
% change in yield
Proper prestimulation, 40 to 60" 5 - 10
Stripping 6 - 9
Three times milking 12 - 20
Four times milking 15 - 25
Extended lighting 5 - 10
rbST 5 - 20
Rumensin 5 - 10
Dairy producers should establish an operational plan for each phase that, if exercised properly, provides a reasonable chance of achieving the production goals. This involves:

  1. assigning specific responsibilities to individuals for each key area and insuring the people understand their duties and that they will be held accountable for performance.
  2. formulating a set of minimally acceptable standards
  3. initiating a performance monitoring system
  4. deciding how frequently the performance will be evaluated
  5. generating a mechanism for initiating corrective action as necessary
Suggestions for minimally acceptable standards (herd goals):
Production: Milking: Health: work with DVM with particular attention to Reproduction:

Dairy Herd Health

In the past veterinarians were like firemen, waiting for calls to come in and then rushing out to try overcoming disaster. This approach is no longer adequate whenever producers invest the considerable amounts of capital necessary to build and equip. intensive dairy facilities. Fortunately, new discoveries, particularly in the area of disease prevention, now enable the veterinarian and other specialists to work with the livestock producer to form a team that keeps animals healthy. Such programs should include, in addition to the routine immunizations and other clinical-surgical procedures, regular management consultations and provision of advice on nutrition, reproduction and udder health. To be effective, the practitioner must make regular visits and producers must be willing to compensate them for time invested rather than just on a fee-for-service basis. The actual frequency would depend on herd size, perhaps monthly as a minimum for small herds up to at least weekly for large units. Sufficient time should always be available after conclusion of the clinical activities for such things as an environmental assessment, reviewing the body condition scoring procedures, etc. and for discussing specific concerns, performance and targets, feed analysis results, and perhaps any anticipated problems or contemplated changes in management routine.

Udder Health

Mastitis, undoubtedly the most common and costly disease of dairy cows all over the world, is almost always the result of infection by pathogenic microorganisms that produce inflammation in the mammary gland. No dairy herd is ever likely to be completely free of mastitis but good operators should be able to keep its incidence down to the point where it is almost undetectable.

Milking usually occurs at the cow's regular location in tie-stall barns or in milking parlors for free-stall animals. Regardless of the type, it must provide an environment where cows can be milked quickly and comfortably under hygienic conditions. Since this is where the major dairy output is harvested, the milking area and routine are extremely important. The milking equipment functions during two or even more periods each day. This adds up to more hours each year than for all other equipment combined. Thus, a thorough understanding of proper operation, frequent maintenance and periodic updating are necessary.

Requirements for good udder health

  1. The designing and building of an effective milking facility (OMAFRA Factsheet).
  2. Since dairy cows are creatures of habit, a proper milking routine is essential.
  3. Monitoring udder health with the California or Wisconsin mastitis test for rapid screening of suspect quarters, by routine bulk tank and individual cow somatic cell counting (OMAFRA Factsheet) and laboratory cultures to identify the specific microorganisms involved whenever this is necessary.
  4. The elimination of existing infections through treating cows during lactation or when dry and by culling chronically infected animals.
  5. The prevention of new infections by providing an hygienic environment (OMAFRA Factsheet) ensuring that equipment functions properly, establishing a sound milking routine and with use of appropriate dry cow therapy.

Reproduction

Successful livestock farming requires animals with ability to convert basic ingredients into marketable commodities worth more than the total cost of production. Since all consumable products, including milk, are obtained through exploitation of reproductive processes, having animals that give birth regularly is extremely important. Under intensive production conditions in industrialized countries, most dairy farmers use highly specialized breeds housed under controlled environmental conditions. With good reproductive efficiency, the biological efficiency of such monoproduct units is often high, approaching limits established by the animals' genetic potential. Maximum reproductive rates are perhaps less important in regions where animals are kept for dual and even triple purposes, but regular birth of replacements is necessary for continued production even under these conditions. Whenever specialized, intensive practices are adopted, however, satisfactory pregnancy rates must be obtained or commercial dairy farming cannot be profitable.

A suitable goal for intensive units might be to develop breeding management systems that maximize reproductive efficiency to the extent this can be justified economically. Herd reproductive activities should be critically evaluated at frequent intervals to assess performance and prospects for improvement. In some instances the cost of additional inputs in relation to what might be achieved dictate that less than maximum efficiency must be accepted. In all cases, successful farmers are those with ability to identify problems and apply practical solutions quickly so they continuously apply methods that work well in their facility. One of the first steps in establishing a sound breeding management program is selecting challenging but achievable targets. Unfortunately, some livestock owners, particularly if they do not assume responsibility for or participate in the daily management of their reproducing animals, frequently have unrealistic expectations.

Reproductive Efficiency in Dairy Farms.

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In determining total lifetime productivity of dairy cows, total milk yield should be equated against all expenses for housing, feeding and caring for animals during growth from birth to first calving and the dry period between successive calvings, as well as during lactations. Thus, the "Precalving Interval" from birth to first parturition, as well as all the subsequent "Intercalving Intervals" between successive calvings, as shown in the accompanying figure, combined with the number of times the pregnancy cycle is successfully completed, affect lifetime reproductive performance.

Management of calves and yearling heifers governs length of the "Precalving Interval." Similarly, nutritional status, disease prevention program and estrous detection-management procedures, plus the fertilization rate and embryo-fetal survival, influence the associated "Intercalving Intervals". Optimum reproductive efficiency involves keeping these intervals as short as is practical and economical.

All operations with breeding livestock will have some infertility so even the most competent dairy farmers must accept that reproductive problems will occur. Even in herds with apparently similar genotypes, feeding practices and housing, variation ranges from minor and infrequent delays to situations in which almost all of the cows have greatly prolonged days open and associated "Intercalving intervals," with substantial proportions culled for infertility. Various measures of reproductive performance are available to assist competent managers recognize breeding abnormalities quickly and initiate corrective actions to treat or eliminate affected animals before the situation becomes critical. Unfortunately, many herd operators do not possess this ability so even serious management deficiencies affecting herd performance is often overlooked. The general causes of reproductive failure are summarized in the previous section on Animal Reproduction

Poor reproductive function in dairy herds has many possible causes, some of which are listed in the accompanying figure. Areas for a more detailed investigation whenever performance is considered to be unacceptable are also suggested.

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Numerous studies indicate poor estrus (heat) detection is the most common cause of prolonged intercalving intervals in dairy cattle so herd managers must insure that animal attendants responsible for this are competent. An estrus detection efficiency of 75 % would represent outstanding performance, a standard achieved in very few herds. Even 60 % efficiency would be somewhat above average with perhaps a 45 % detection rate representing about the average for commercial dairy farms. Many herds, however, realize only 20 to 30 % efficiency, a rate that results in far to many days open. This poor detection efficiency results in greatly prolonged intercalving intervals and high involuntary culling for reproductive failure. Unfortunately, this latter situation is encountered on many dairy farms all over the world. Details on estrus and its detection are available if you wish to review them.

Modern Dairy Breeding

WWW Virtual Library for Dairy Production

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