Animal and Herd Productivity in Dairy Cattle

In most dairy herds, nutritional management is the most important determinant of herd productivity and profitability. The relationship between nutrition and productivity begins at birth. The feeding system must deliver the necessary nutrients to each animal at the correct stage of growth and lactation to maintain optimal productivity, and these requirements are based on mature cow body weights of the herd.

Research has shown the importance of the ration fed to cows in the transition during the 2–3 weeks before calving (1, 2). Dry cows are fed a diet relatively low in carbohydrates and protein and high in fiber, reflecting the lower nutrient demands of nonlactating cows. The transition-period ration must allow the rumen to adapt to the lower-forage, more nutrient-dense lactating ration. In addition, the stresses associated with moving animals to the transition pen and with calving itself tend to decrease feed consumption at this critical time.

Decreased feed intake in the transition period is associated with excessive weight loss; decreased peak milk production; and increased incidence of postpartum diseases such as metritis, retained placenta, ketosis, displaced abomasum, and fatty liver. One method for proactive detection of ketosis in postpartum cattle is to measure blood concentrations of beta-hydroxybutyric acid, one of the ketone bodies, in the first week after calving.

Rations for lactating cows must be balanced between providing high levels of energy and protein to support high milk production and maintaining optimal rumen health and motility.

Subacute ruminal acidosis (SARA) is a common condition resulting from an excess of fermentable carbohydrates, a deficiency of fiber of adequate length, or a combination of the two. Health effects of SARA include digestive upset and diarrhea, decreased feed consumption and milk production, decreased milk butterfat, rumen epithelial ulceration, liver abscessation, and foot problems related to subclinical laminitis.

The choice of a feeding system depends on herd size and production level. Three general types of feeding systems are used currently by dairy farmers: total mixed ration (TMR), component feeding, and management-intensive grazing. Each of these systems, when implemented correctly, can deliver adequate nutrients for a highly productive dairy herd. Each system has its own inherent challenges in achieving optimal productivity.

The use of TMR feeding systems has increased as more dairy operations have adopted free-stall or dry-lot housing for their herds. TMR diets have several advantages: cows consume the desired proportion of forages, risk of digestive upset is decreased, feed efficiency is increased, by-product feeds may be used, diet formulation is more accurate, and labor needs are decreased.

However, the performance of herds fed TMR diets can be adversely affected by errors in ration formulation and feed delivery. The challenges of TMR feeding are often summed up like this: There are three rations for a dairy herd—the ration on paper as formulated by the nutritionist, the ration delivered to the cows, and the ration the cows actually consume.

Some common formulation or delivery errors with TMR diets include the following:

• inadequate or nonexistent laboratory forage testing

• infrequently evaluated forage dry matter

• variation in dry matter intake

• overmixing of diets that decreases effective fiber length

• errors or imprecision in mixing of the ration

• incorrect mature cow body weights

• poor mixing due to overfilling the load capacity of the TMR mixer

• overfeeding or underfeeding energy to late-lactation cattle

With TMR diets, feeding mistakes are often spread across the entire group or herd. Health management programs of herds that are fed TMR diets should include systems to monitor the adequacy of the ration formulation and delivery. Such monitoring includes evaluating particle size of the ration using a particle separator box and conducting TMR audits that systematically evaluate mixer functionality and management practices, including component wear, auger timing and speed, mixer box level, hay and straw processing, loading position and size, ingredient mixing order, liquid ingredient placement, forage restriction settings, and adequate mixing time.

Component-fed herds receive grain and forage separately. Advocates of component feeding emphasize the ability to meet the production and metabolic needs of individual cows throughout their production cycle. The primary disadvantage of component feeding systems is that the cows receive concentrates separate from forages, enabling ingestion of these concentrates in a single feeding, which can increase the risk of ruminal acidosis and indigestion.

Management-intensive grazing systems can be used to meet the needs of modern dairy cows:

• In some regions of the world (eg, New Zealand and Australia), pasture-based systems are the predominant method of feeding dairy cattle. In these truly pastoral systems, nutrition frequently limits productivity because of substantial annual variation in growing conditions. However, the economic model in such systems emphasizes low production costs rather than maximal productivity.

• In other areas, such as Britain and the northeastern US, rotational grazing is used to provide the forage requirements of lactating cattle during spring and summer, and supplemental concentrates and corn silage are fed to achieve high milk production.

In both situations, seasonal calving is practiced to match rainy- or spring-season pasture conditions with the energy needs of early-lactation cows. Attention to reproductive management is therefore critical for dairy producers attempting to breed all cows in a herd within a defined period.

Production management programs for herds in management-intensive grazing systems must include measures to control bloat, hypomagnesemia, and copper and selenium deficiency. Pastured cattle might walk considerable distances to feed on forages. Therefore, a system to monitor and minimize lameness must be included in the health delivery system.

Also see Management of Reproduction: Cattle.

Artificial insemination (AI) using semen from genetically superior sires is the most important factor leading to increased productivity in the dairy industry, and the rate of genetic gain in registered US Holsteins has reached approximately 109 kg/year since genomic selection was introduced (3). Even today, the genetic potential for milk production greatly exceeds the actual milk yield achieved on most farms, highlighting the importance of management to enable the full expression of genetic potential.

In conventional dairy herds in which calving occurs throughout the year, suboptimal reproductive management leads to the failure of cows to conceive in a timely fashion, or at all. Reproductive disorders are the most common and costly reason for premature culling of dairy cows, and cows remaining nonpregnant (open) decrease productivity in the following ways:

• Open cows spend more time in late lactation, with lower milk production.

• Cows taking longer to conceive might dry off sooner, leading to longer dry periods and increased risk of overconditioning, and predisposing animals to metabolic disorders in the subsequent lactation.

• The risk of culling increases greatly in cows remaining open > 300 days after calving.

• Fewer replacement heifers are available.

• Higher labor and treatment costs are associated with prolonged efforts to synchronize and breed open cows.

Successful AI requires inseminating cows during estrus within a tightly defined window of optimal fertility, as well as thawing the semen properly, transporting it quickly to the cow, and depositing it in the appropriate part of the reproductive tract.

One of the most important factors affecting the success of an AI program is the detection of estrus. Data indicate that < 60% of estrus periods are successfully detected by visual observation in lactating dairy cattle (4). Efforts to improve heat detection using estrus synchronization and pressure-based detection aids (tailhead-mounted markers that release dye when an animal is mounted, signaling standing heat) might be constrained by the shorter, less intense estrus expression of modern US Holsteins, as well as the greater difficulty in observing estrus on larger farms.

Many farms use hormone synchronization protocolsinstead of estrus synchronization, which enable timed insemination to be performed with acceptable conception rates. These programs have been widely adopted and have enabled dairy herds to dramatically increase the number of pregnant cows throughout defined time periods.

In addition, hormone synchronization protocols enable the scheduling of many injections and inseminations on a weekly basis, leading to more efficient use of labor. These timed insemination programs have led to a resurgence in the use of AI and are markedly increasing the genetic milk production potential of dairy cows.

Although the use of natural service sires is much less common, some dairy managers have returned to this practice to ensure that cows conceive promptly. In these herds, breeding soundness examinations of bulls, bull libido assessments, and bull management programs should be part of routine management practices to ensure continued herd productivity.

The problems associated with natural service for dairy herds include decreased genetic improvement of offspring; costs associated with the purchase, raising, and feeding of bulls; damage to facilities; and danger to humans.

The widespread adoption of aggressive, timed insemination programs has emphasized the importance of early and accurate pregnancy diagnosis. Cattle found to be nonpregnant (open) at pregnancy diagnosis can be resynchronized to minimize the amount of time they remain open.

Accuracy in pregnancy diagnosis is essential because a pregnant cow mistakenly called open will be given prostaglandin F2alpha as part of the synchronization program and, as a result, will abort the embryo.

Veterinarians are increasingly adopting transrectal ultrasonography over rectal palpation for routine pregnancy diagnosis, because ultrasonography is simple, reliable, and safe, and enables earlier pregnancy diagnosis.

Another option for early pregnancy diagnosis in cattle is the use of blood tests to identify the presence of pregnancy-associated glycoproteins. These tests are inexpensive and are highly specific and sensitive. In herds whose veterinarians cannot visit frequently enough, herd managers can collect blood samples from cows bred at least 30 days before and ship them to laboratories to perform the tests.

Because there is an expected 7–13% rate of embryonic loss between 30 and 60 days after conception (5), early pregnancy detection by any method should be followed by manual confirmation after day 60 of gestation. In addition, some automated milking system (AMS) platforms incorporate progesterone monitoring for pregnancy diagnosis.

Dairy herd productivity can be profoundly affected by the success of the replacement program. The cost of raising heifers is a substantial proportion of the overall cost of production, accounting for approximately 20% of total annual milk production costs (6, 7).

A replacement cow does not begin to earn a profit until midway through her second lactation. Two developments have dramatically increased the number and genetic potential of female dairy replacements: use of sex-selected semen and genomic testing of AI sires and replacement females.

Sex selection of bovine semen was validated at Colorado State University in the 1990s and early 2000s (8), and the technology has been licensed to virtually all major bovine semen companies. The use of female-selected semen increases the likelihood of a female calf to 85–90% (9), dramatically increasing the number of female replacements available on a dairy farm.

In the initial iterations of sex selection technology, a straw of sex-selected semen typically contained fewer sperm because of the amount of time required to sort sperm; as a result, the fertility of a dose of semen was decreased. Therefore, it has been recommended that the use of sex-selected semen be limited to virgin replacement heifers whose fertility is naturally higher than that of older, multiparous cows (10, 11). More recent developments have greatly increased the speed and accuracy of sorting, and the fertility of the current sex-selected semen straws is closer to that of conventional semen (12).

To manage herd inventories, many producers who use sexed female semen to generate replacement heifers often also use beef semen on older or lower-genetic-merit cows. This approach limits excess heifer production, because calves from beef-on-dairy crosses are not intended to be retained, and it avoids propagating less desirable genetics. However, the sharp increase in the value of nonreplacement calves, particularly beef-on-dairy crosses, has made these matings a meaningful revenue stream, shifting many dairies from a heifer surplus to a potential shortfall in future replacement supply.

The genome sequence of a Hereford cow was first published in 2009, and regions of the genome corresponding to various beneficial traits, such as milk production and overall health and wellness, have been identified (13). Tests for these traits are now readily available and reasonably priced, and male and female cattle can be tested at any time after birth.

Semen companies can use the tests to identify potential sires that carry beneficial traits, saving years of time and expense in the process of selecting AI sires. Dairy herds can test their adult cows to identify high-genetic-merit dams of replacement heifers. Female calves can be tested for future milk production potential, and high-genetic-merit individuals can be identified. Given the surplus of replacement heifers on many farms because of the use of female sex-selected semen, heifers with lower genetic merit can be sold for beef.

A wide range of mortality rates is reported for replacement animals (14). The highest morbidity and mortality rates on dairy farms generally occur before weaning, and digestive disorders and respiratory disease account for the majority of recorded disease cases and deaths. These disorders can be effectively controlled through well-designed health management protocols that address the following factors:

• dam care and housing during the periparturient period

• appropriate calving management

• timely feeding of adequate volumes of high-quality colostrum

• implementation of preventive measures, optimal nutrition, and proper ventilation

Calves should receive an initial colostrum feeding equivalent to 8.5–10% of body weight (15), and providing multiple colostrum feedings is associated with improved transfer of passive immunity (16). In addition, when considering the nutritional management of calves, it is important to assess whether the total amount of solids that calves receive daily (whether from whole milk or from milk replacer) meets farm management goals.

Historically, restricted milk feeding was intended to stimulate early solid feed intake; however, calves offered < 8 L (< 2 gallons) of milk per day exhibit signs of hunger (17) likely, in part, because of the lower efficiency of metabolizable energy use from calf starter compared with milk components (18).

Environmental and housing conditions also play a critical role in shaping calf health and performance outcomes. Providing adequate space (≥ 3.3 m² [35 square feet]; [19]) and minimizing age variation within shared air spaces are associated with decreased rates of mortality, diarrhea, and respiratory disease (20). In addition, clean, dry bedding; proper drainage; and effective ventilation are essential to decrease environmental stressors and support overall calf health and performance.

Elevated concentrations of fine particulate matter (≤ 1 mcg/m³), as measured by air quality sensors, are associated with increased odds of lung consolidation and detection of respiratory pathogens. Adequate air exchange rates should be maintained to help mitigate particulate accumulation (21).

Delayed age at first calving decreases dairy productivity by increasing rearing costs because of prolonged feeding of animals in a nonproductive state. Heifers should be 22–24 months old at first calving, which means they should conceive when 13–15 months old. Adequate nutrition is important to ensure that heifers are fertile and cycling at this target age and that they continue to grow, so that they are large enough at calving to limit dystocia and maximize mammary development and lactation. Specifically, heifers should be 55–60% of mature cow body weight at the time of insemination (18). Ensuring that heifers do not become overconditioned is also an important consideration when managing dystocia risk.

There is a well-demonstrated relationship between productivity, profitability, and herd size. A number of factors are involved:

• Larger operations are more willing to adopt production-enhancing technologies and can take advantage of economies of scale when purchasing feed and other consumables.

• Government policies can substantially influence herd size. Countries with supply management systems limit the amount of milk a farm can sell in an effort to decrease the oversupply of milk and support the price per volume of milk sold.

• The amount and productivity of pasture can influence the size of herds that use grazing to supply some or all of the nutrient needs of the herd. In these herds, productivity is determined by balancing the ability of the pasture to produce nutrients against the ability of the cows to produce milk. The size of both grazing and confinement herds is increasingly affected by competing demands for land.

The proportion of the herd that produces milk versus the nonproductive stock (dry cows, calves, heifers, and bulls) has an effect on total herd profitability. Herd composition is the result of a number of interrelated management decisions, such as culling policy, rate of reproductive success, rate of disease, replacement management, and long-term goals regarding herd size.

For instance, older cattle within a herd might need to be culled because of chronic disease problems or because of low conception rates. If plenty of replacement heifers are available, the milking herd demographics might shift toward younger animals to approach 50% first-lactation cattle. Because genetic gain accumulates with each successive generation through selective breeding, younger animals are, on average, genetically superior to the older cows they replace. However, these younger animals will not achieve their full production potential until the third or fourth lactation. As a result, a herd weighted toward younger animals will show lower overall production in the short term, despite carrying higher genetic merit.

With the adoption of timed insemination programs for both first and subsequent services, pregnancy outcomes in older dairy cows have improved, with conceptions occurring more reliably and earlier in lactation. As a result, not as many replacement heifers are needed, and herd demographics shift to favor older, more productive cows. In such a situation, herd managers might choose to perform genomic testing of the female youngstock and sell animals with lower genetic merit.

In countries such as the US, where herd production is not limited, long-term plans regarding expansion often influence herd composition. In growing or start-up herds, nulliparous pregnant cattle are often purchased to meet expansion needs; as a result, these herds tend to have a high proportion of first-lactation animals and lower overall initial production.

Even in optimal housing situations, dairy herd productivity can be affected by environmental conditions. High-producing cows have higher dry matter intake, generate more internal heat, and are less tolerant of high ambient temperature. Weather conditions that combine high ambient temperature and high humidity without periods of cooling generally depress dry matter intake and decrease milk yield.

The temperature-humidity index (THI) is commonly used to assess heat stress risk in cattle; values ≥ 72 indicate the onset of heat stress. At the animal level, respiration rate provides a direct indicator; rates > 60 breaths per minute indicate some degree of heat stress (22).

The increased concentration of dairy farming in regions that experience considerable periods of high temperatures (eg, the southwestern US) has resulted in more seasonal variation in milk output.

Dairy farmers have adopted a variety of systems to combat heat stress. New facilities are constructed with large, open sides and ends (often > 4.3 m high) to take advantage of natural ventilation and use fans and sprinkler systems to keep cows comfortable. Older, enclosed facilities can be retrofitted with tunnel ventilation to provide adequate air movement.

Minimum air velocity to achieve adequate cooling is 200 feet/minute (23), and common fan options include panel fans and high-volume low-speed fans. Air speeds can be assessed using anemometers, which are inexpensive and accessible tools that can enhance the effectiveness of veterinary consultations.

Dairy cattle are remarkably cold tolerant, provided they can remain dry and are sheltered from wind and precipitation. However, substantial die-offs have occurred in regions of the US that normally experience mild winters. In these areas, housing might consist of open dirt corrals and a central milking parlor.

Freak blizzards have led to losses of hundreds of dairy cattle in dry-lot dairies in New Mexico, Texas, and Kansas. Cattle in open or dry-lot dairies should always be provided shelter from wind, as well as shade from summer sun.

Risk factors for most postpartum diseases in dairy cows arise during the dry period; however, clinical signs typically become evident after calving. Such prepartum risk factors include insufficient or excessive energy intake, inadequate regulation of calcium intake and absorption, wet and feces-contaminated pen conditions, and overcrowding, which can lead to diseases such as hypocalcemia (milk fever), hypomagnesemia, udder edema, ketosis, displaced abomasum, lameness, and mastitis.

Dairy health management programs must focus on preventive practices such as vaccination, hoof care, pen hygiene and maintenance, and nutritional monitoring, especially during the dry period, and must monitor the herd for occurrence of these diseases.

Milk yield at dry-off and strict adherence to hygienic protocols during the administration of intramammary treatments are critical factors in decreasing the risk of new intramammary infections during the dry period. To prevent mastitis, NMC: The Global Milk Quality Organization (formerly the National Mastitis Council) recommends a target milk yield of < 15 kg/day at dry-off. This target can be partially achieved by transitioning cows from the lactating ration to a lower-energy (far-off) dry cow diet before dry-off.

The length of the dry period influences milk yield in the cow's subsequent lactation. The general recommended dry period is 6–8 weeks (24, 25, 26). Shortening the dry period to < 40 days is associated with decreased milk yield in the following lactation (25, 26). Dry periods that are too long can lead to excessive weight gain and decreased production efficiency (26).

Both short and long dry periods are most common when breeding dates are uncertain, either because cows are bull-bred or because reproductive records are inaccurate or missing. Long dry periods also arise when cows take a long time to conceive. These cows decline in yield as a normal part of the lactation curve but are dried off early for low production well before calving approaches.

During the dry period, cows often undergo vaccinations and pen changes. Common vaccines include those to protect against neonatal calf diarrhea and clinical mastitis. The timing of vaccination and pen movements has consequences that are important to consider (27):

• In general, shorter intervals between vaccination and calving are associated with lower colostral IgG concentrations at calving, so producers should administer vaccines as far in advance of parturition as label guidelines permit.

• Vaccinating 1 week before a pen change, compared with vaccinating at the same time as a pen change, can help improve the IgG concentration of colostrum.

• National Mastitis Council. Dry Cow Therapy. Revised 2006.

• Dairy Farmers of Canada. Drying Off Cull Dairy Cattle at High Production and in Emergency Situations. Revised August 2020.

• Urie NJ, Lombard JE, Shivley CB, et al. Preweaned heifer management on US dairy operations: Part V. Factors associated with morbidity and mortality in preweaned dairy heifer calves. J Dairy Sci. 2018;101(10):9229-9244.

• FARM Animal Care. Farmers Assuring Responsible Management.

• Code of Practice for the Care and Handling of Dairy Cattle. National Farm Animal Care Council (Canada). 2023.

• Dairy Reproduction Protocols. Dairy Cattle Reproduction Council.

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