Dairy Cattle Feeding and Nutrition management

03/02/2023

04/12/2022

The productivity of an individual cow is the sum of the value of the milk she produces, the value of her offspring, and her individual market value when she leaves the herd. Many factors influence individual cow productivity, which is also based on longevity and the proportion of the cow’s lifetime spent producing milk. Nonproductive periods include the period from birth until first parturition and dry periods before subsequent calvings. Heifers must be managed to reach appropriate breeding size by 13–15 months of age to maximize lifetime production.
Milk yield is related to stage of lactation. Milk yield increases rapidly after calving, reaches a plateau 40–60 days after calving, and then declines at a rate of 5%–10%/month. The rate of decline is lower in first-parity animals than in older cows. Good reproductive management ensures that the largest proportion of a cow’s total lifetime production is spent during early high-producing stages of lactation rather than late, lower-producing periods. Milk yield increases with age and parity until about the sixth lactation; these cows may produce up to 25% more milk volume than first lactation cows. Health disorders or other management problems that reduce longevity have a negative impact on productivity.

Nutritional Management
In most dairy herds, nutritional management is the most important determinant of herd productivity. The relationship between nutrition and productivity begins at birth. The feeding system must deliver the necessary nutrients to each cow at the correct stage of growth and lactation to maintain optimal productivity.
Research has documented the importance of the ration fed to cows in the transition during the 2–3 weeks before calving. Dry cows are fed a diet relatively low in carbohydrates and protein and high in fiber, reflecting the low nutrient demands of the nonlactating cow. The transition period ration must allow the rumen to adapt to the lower-forage, more nutrient-dense lactating ration. Further, the stresses associated with moving animals to the transition pen and of calving itself tend to reduce feed consumption at this critical time. Reduced feed intake in the transition period is associated with excessive weight loss; reduced peak milk production; and an increased incidence of postpartum diseases such as metritis, retained placenta, ketosis, displaced abomasum, and fatty liver. Research has documented the benefits of monitoring postpartum cattle for excessive energy mobilization by measuring blood levels of beta-hydroxybutyric acid, one of the ketone bodies.

Rations for lactating cows must strike a balance 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 excessive fermentable carbohydrates, inadequate fiber of adequate length, or a combination of the two. Health effects of SARA include digestive upsets and diarrhea, reduced feed consumption and milk production, reduced butterfat content of milk, ulceration of rumen epithelium, liver abscessation, and a series of foot problems related to subclinical laminitis.
The choice of a feeding system is associated with 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 herds have adopted free-stall or dry-lot housing. TMR diets have several advantages: cows consume the desired proportion of forages, risk of digestive upset is reduced, feed efficiency is increased, byproduct feeds may be used, accuracy of diet formulation is higher, and labor needs are reduced.

However, the performance of herds using TMR diets can be adversely affected by errors in ration formulation and feed delivery. An oft-quoted statement illustrates the challenges of TMR feeding. There are 3 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 include:
inadequate or nonexistent forage testing
variation in forage dry matter
variation in dry-matter intakes
overmixing of diets that reduces effective fiber length
errors or imprecision in the mixing of the ration
overfeeding or underfeeding energy to late-lactation cattle
When TMR diets are fed, feeding mistakes are often spread across the entire group or herd. Health management programs of herds that receive TMR diets should include systems to monitor the adequacy of the ration formulation and delivery.

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 cow receives concentrates separate from forages, enabling ingestion of these concentrates in a single feeding, leading to rumen 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 significant annual variation in growing conditions. However, the economic model in such a system emphasizes low costs of production rather than maximal productivity. In other areas, such as Britain and the northeastern USA, rotational grazing is used to provide for the forage requirements of lactating cattle during the spring and summer months, 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 herds in which there is an attempt to breed all cows within a defined period.

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

Reproductive Management
Artificial insemination (AI) using semen from genetically superior sires is the most important factor leading to increased productivity in the dairy industry, accounting for at least 150 kg increased annual production since its inception. Even today, the genetic potential for milk production greatly exceeds the actual milk yield achieved on most farms. Reproductive disorders are the most common and costly reasons for premature culling of dairy cows.

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. Cows remaining nonpregnant (open) reduce productivity in the following ways:

Open cows spend more time in late lactation, with lower milk production
Cows taking longer to conceive may dry off sooner, leading to longer dry periods
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 that cows be inseminated during estrus in a narrow range of optimal fertility, and that the semen be thawed properly, transported quickly to the cow, and deposited in the appropriate area of the reproductive tract.

The most important factor affecting the success of an AI program is the detection of estrus: US data indicate that < 40% of estrus periods were detected in lactating dairy cattle. Efforts to improve heat detection using estrus synchronization and artificial detection aids have been largely unsuccessful and are hampered by the reduced duration and intensity of estrus exhibited by modern US Holsteins, and by the greater difficulty in observing estrus on larger farms.
Because estrus detection rates are so low, some dairy managers have returned to extensive use of natural service sires to ensure that cows conceive promptly. In these herds, breeding soundness examinations and bull management programs should be part of routine management practices to ensure continued herd productivity. However, the problems associated with natural service include reduced genetic improvement of offspring; costs associated with purchase, raising, and feeding bulls; damage to facilities; and danger to people.

Researchers in Wisconsin and Florida have developed hormonal synchronization protocols that allow timed insemination to be performed with acceptable conception rates. These programs have been widely adopted and have enabled herds to dramatically increase the number of pregnant cows throughout defined time periods. Many of the injections and the inseminations can be scheduled 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 significantly increasing the genetic milk production potential of the dairy cow.

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 30–35 days after breeding can be resynchronized immediately to minimize the time they remain open. Accuracy is essential, because a pregnant cow mistakenly called open will be given prostaglandin F2alpha as part of the synchronization program and will abort the embryo. Veterinarians are increasingly adopting transrectal ultrasonography for routine pregnancy diagnosis, because pregnancy diagnosis at 32 days using ultrasound is simple, reliable, and safe.

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 30 days or more and ship them to laboratories performing the tests. Because there is an expected 5%–10% embryonic loss between 32 and 60 days after conception, early pregnancy detection by any method should be followed by manual confirmation after day 60 of gestation.

21/09/2022

Dairy Cattle Nutrition of Milking and Dry Dairy Cows
Feed costs for the dairy cattle herd represent 50 to 60% of the total cost associated with the production of milk. In addition, properly implemented dairy cattle nutrition programs can improve milk production, health, and reproductive performance of dairy cows for both the milking herd and dry cows. In this section, articles on various aspects of dairy cow nutrition and feeding and dairy feeding management are provided. Articles pertaining to acidosis and lameness in dairy cattle, feed additives, the use of by-products in dairy cattle diets, fats, water quality, protein nutrition, minerals and vitamins, feeding management, troubleshooting nutritional problems, and forage information

21/09/2022

Lactating cows should be managed to maximize intake rapidly after calving to minimize the severity and duration of negative energy balance experienced. Milk production and associated energy requirements generally peak at ~6–10 weeks into lactation, whereas DMI usually does not peak until 8–12 weeks into lactation. Postpartum negative energy balance severity will negatively impact body condition, resulting in greater risk for postpartum disease and reproductive inefficiency. Dietary starch content influences intake capacity immediately after calving, while dietary NDF content ( See table: Impact of Forage NDF on Forage Intake Capacity) is the primary factor at peak milk production. Dietary NDF provides a physical fill factor influencing intake, which depends on rate of passage and NDF digestibility. Intake capacity of NDF varies with physiologic state, ranging from 0.6% to 1.2% of body weight. Lowest intake capacity occurs in late pregnant heifers (0.6%) followed by late pregnant cows (0.8%). Intake following peak milk production should be monitored to prevent excess body condition accumulation (body condition score >3.5 on a 5-point scale).
Impact of Forage NDF on Forage Intake Capacity
Carbohydrates
Dietary carbohydrates comprise a wide range of compounds from simple sugars to complex polysaccharides. They account for 60%–80% of dietary dry matter for dairy cows. Carbohydrate fractions are segregated based on chemical measures and nutritional impacts (see Plant carbohydrate fractions ). Complex polysaccharides associated with the plant cell wall and resistant to microbial fermentation are quantified by measures of neutral detergent fiber (NDF) and its subset of acid detergent fiber (ADF). These structural carbohydrates will limit intake but stimulate chewing and rumination, which helps maintain rumen buffering and health and can increase milk butterfat composition.
In general, fiber in the diet supports rumen health. Fiber in the rumen, especially fiber from forage sources that have not been finely chopped or ground, maintains rumen distention, which stimulates motility, cud chewing, and salivary flow. These actions affect the rumen environment favorably by stimulating the endogenous production of salivary buffers and a high rate of fluid movement through the rumen. Salivary buffers maintain rumen pH in a desirable range, while high fluid flow rates increase the efficiency of microbial energy and protein yield. Fiber, however, delivers less dietary energy than nonfiber carbohydrates (NFCs). Fiber is generally less fermentable in the rumen than NFC, and rumen fermentation is the major mechanism by which energy is provided, both for the animal and the rumen microbes. Therefore, diets with high NDF concentrations promote rumen health but provide relatively less energy than diets high
Nonfiber carbohydrate (NFC) proportions are calculated by subtracting the proportions (as dry matter) of NDF, crude protein, fat, and ash from 100%. Nonfiber carbohydrates primarily consist of organic acids, sugars and starch, and neutral detergent soluble fiber (NDSF). In fermented feeds, fermentation acids also contribute to the NFC fraction. The sum of sugars and starch is referred to as nonstructural carbohydrates (NSCs), which should not be confused with NFCs. Fiber compounds associated with the secondary plant cell wall that are not digestible by mammalian enzymes but that are solubilized by neutral detergent are defined as NDSF. Although pectins, beta-glucans, and galactans are associated with the secondary plant cell wall, they are highly fermentable and provide good sources of energy in the ruminant diet.
Balancing fiber and NFC fractions to optimize energy intake and rumen health is a challenging aspect of dairy nutrition. To increase the energy supply, dietary NDF concentrations are usually reduced by adding starch and other sources of NFCs. This increases the rate and extent of rumen fermentation, which leads to greater energy availability. Increased ruminal fermentation also leads to the increased production of volatile fatty acids, which tends to lower rumen pH. At rumen pH 1.71–1.76 Mcal/kg do not contain adequate fiber to support good rumen health and function. Thus, dairy cows in early lactation typically cannot meet their energy requirements and are expected to lose weight.
Fats
Ruminant diets typically are low in total fat content due to the negative effects that fatty acids, especially polyunsaturated fatty acids, have on microbial fiber fermentation. Dietary fat can come from three sources:
Endogenous fats: forage lipids that include glycolipids, pigments, cutins, and waxes
Vegetable fats: polyunsaturated fats from oilseeds such as soybean, corn, canola, sunflower, and flaxseed
Rumen inert fats: saturated animal fats, calcium soaps, and prilled fats
Typically, each type of fat source can be supplied in the diet at 2%–3% of dry matter up to a total of 8%–9% total fat. Fats in ruminant diets can induce undesirable metabolic effects, both within the rumen microbial population and within the animal. Ramifications of these effects include reduced fiber digestion, indigestion and poor rumen health, and suppression of milk fat concentration.
Another method of evaluating dietary fat and potential impacts on rumen microbes or cow is quantifying rumen unsaturated fatty acid load (RUFAL). Unsaturated fatty acids are biohydrogenated by rumen microbes to generate saturated fatty acids. An intermediate in this biohydrogenation process, especially under lower rumen pH conditions, are alternative conjugated linoleic acids (CLA) that can inhibit mammary de novo fat synthesis, resulting in milk fat depression. The trans-10 CLA compound has been primarily associated with milk fat depression.
Supplemental fat can provide additional concentrated energy to meet lactating cow energy needs. Adding fat within the first 3 weeks of lactation has shown a negative effect on intake; thus, it is not recommended. The addition of fat after this period may improve milk fat content, milk production, or reproductive efficiency; however, response to dietary fat supplementation is not consistently predictable. The amount of total fat consumed from all three sources should be limited to the amount of fat produced (milk production × fat percentage).
Protein
Protein requirements of lactating dairy cows are based on amino acids required for maintenance and milk protein synthesis. Ruminant animals derive most of their amino acids to support body metabolism from microbial protein. Microbial protein is of high biological value and highly digestible. Mixed microbes contain between 45% and 60% crude protein. Therefore, dietary formulations are directed to ensure optimum microbial growth to minimize the need for expensive dietary protein supplements.
Dietary protein not used by rumen microbes can be potentially digested in the abomasum and resultant amino acids absorbed in the small intestine. This fraction of dietary protein is termed rumen undegradable protein (RUP), in contrast to the dietary protein fraction degraded in the rumen (rumen degradable protein [RDP]) and used by the microbes. To their advantage, ruminants are able to use low-quality protein or nonprotein nitrogen sources to generate microbial protein to meet their amino acid requirements.
Two systems of describing the dietary protein supply and requirements for dairy cows are in general use:
Crude protein system: based on dietary nitrogen converted to protein equivalent using 6.25 multiplier factor (assumes protein is 16% nitrogen); does not account for differences in availability to rumen or cow
Metabolizable protein system: based on a model predicting dietary nitrogen and carbohydrates availability to rumen microflora and predicted microbial protein flow and dietary rumen undegraded protein fraction and its digestibility to account for total protein available and absorbed
The crude protein system is relatively simple to use and has provided a traditional means of formulating dairy cow rations. The table Recommended Minimum Dietary Protein Concentrations for Dairy Cows at Various Levels of Production provides general guidelines for the required crude protein concentration of diets for large- and small-breed dairy cattle at various levels of production. It can be used for general evaluations of the protein adequacy of dairy diets. The metabolizable protein (MP) system is more complex than the crude protein system. It was developed in recognition of the need to provide dietary nitrogen to support microbial growth (RDP) in addition to dietary RUP to collectively meet cow amino acid needs. Unlike crude protein, MP cannot be directly measured in a feed ingredient via laboratory analysis.
Recommended Minimum Dietary Protein Concentrations for Dairy Cows at Various Levels of Production
The efficiency with which RDP is recovered as microbial protein depends on the growth rate of the rumen microbes, which in turn depends on the supply of fermentable energy sources in the rumen. Thus, diets with sufficient RDP and relatively high energy concentrations will result in high yields of microbial protein, which will become available for intestinal digestion and absorption as MP. Calculations that balance dairy diets for MP must consider the complex interrelations among fermentable energy sources, RDP, and RUP. In general, specialized software, commercially available, is necessary to formulate dairy diets using the MP system. Even with such software, many variables must be estimated with uncertainty. Therefore, calculations of MP supply must be recognized to be approximations.
Relationship of dietary protein intake to metabolizable protein supply
Relationship of dietary protein intake to metabolizable protein supply
Diagram showing the relationship of dietary protein intake to metabolizable protein supply. The two branch points (indicated by 1 and 2) constitute the major variables relating the dietary crude protein supply to the metabolizable protein supply. The first branch point represents the proportion of protein that is degraded in the rumen. This branch point is influenced by inherent properties of the protein and the rate of ingesta passage through the rumen. The second branch point represents the proportion of nitrogen from degraded protein that is recaptured as microbial protein. This is influenced by the microbial growth rate, which depends on the supply of rumen available energy. Nitrogen that is not recaptured as microbial protein is absorbed from the rumen as ammonia and converted to urea by the liver. Some urea is recycled back to the rumen; however, a large portion is excreted in urine.
RUP, rumen undegraded protein; RDP, rumen degraded protein; N, nitrogen; MCP, metabolizable crude protein; MP, metabolizable protein.
Dietary ingredients vary in their proportion of RDP and RUP. In general, feeds with high moisture and high protein concentrations (eg, legume silages) will have a high proportion of RDP. In contrast, feeds that have been processed and especially those that have undergone drying will have relatively high proportions of RUP. The proportions of RUP and RDP in diets and individual ingredients are not fixed but can vary somewhat depending on intake rate.
At high rates of feed intake, the rate of feed passage through the rumen is high; thus, there is less opportunity for rumen protein degradation than with the same feeds at lower intake rates. Therefore, on the same diet, RUP proportions are higher in animals with high rates of feed intake than in those with low rates of feed intake. Animals most likely to benefit from supplements selected for high RUP proportions are those with relatively high protein requirements and relatively low rates of feed intake.
The specific amino acid requirements of dairy cows are not as well understood as those of swine or poultry. Most research has focused on methionine and lysine as first limiting amino acids in typical dairy cattle diets, especially during early lactation. These amino acids can be supplemented by feeding targeted RUP ingredients high in these amino acids or rumen-protected forms of these amino acids. Software is available that estimates the amino acid supply for dairy cows on different diets. With typical feedstuffs, if the MP requirement is met and the dietary lysine-to-methionine ratio is ~3:1, then the amino acid requirements for milk production are likely being optimized.
Water
The availability of high-quality water for ad libitum consumption is critical. Insufficient water intake leads immediately to reduced feed intake and milk production. Water requirements of dairy cows are related to milk production, DMI, ration dry-matter concentration, salt or sodium intake, and ambient temperature. Various formulas have been devised to predict water requirements. Two formulas to estimate water consumption of lactating dairy cows are as follows:
equation
where FWI is free water intake (water consumed by drinking rather than in feed), DMI is in kg/day, milk is in kg/day, Na is sodium intake in g/day, and temperature is in °C. Water consumed as part of the diet contributes to the total water requirements; thus, diets with higher moisture concentrations result in lower FWI.
Providing adequate access to water is critical to encourage maximal water intake. Water should be placed near feed sources and in milking parlor return alleys because most water is consumed in association with feeding or after milking. For water troughs, a minimum of 5 cm of length per cow at a height of 90 cm is recommended. One water cup per 10 cows is recommended when cows are housed in groups and given water via drinking cups or fountains. Every cow group should have a minimum of two watering stations to prevent a high social order cow from blocking a single water source.
Individual cow water intake rates are 4–15 L/min. Many cows may drink simultaneously, especially right after milking, so trough volumes and drinking cup flow rates should be great enough that water availability is not limited during times of peak demand. Water troughs and drinking cups should be cleaned frequently and positioned to avoid f***l contamination.
Poor water quality may result in reduced water consumption, with resultant decreases in feed consumption and milk production. Water can be evaluated by its organoleptic properties (color, taste, and smell) or quantification of dissolved or suspended contents. Factors affecting water quality include the following:
pH: A wide pH range from 5 to 9 seems acceptable to cattle; extremes of the pH range may be of concern for palatability.
Microbiological contamination: Bacterial counts that may cause digestive issues in ruminants have not been well documented. No correlation has been found between bacterial contamination level and cow performance; however, if bacteria are present, it is reasonable to clean watering units more frequently.
Total dissolved solids (TDS): Also referred to as total soluble salts, TDS is a major factor that refers to the total amount of inorganic solute in the water. TDS is generally expressed in units of mg/L or parts per million (ppm), which are numerically equivalent values ( see Table: Guidelines for Total Soluble Salts (Total Dissolved Solids) in Drinking Water for Cattle).
Hardness: A measure of calcium and magnesium content in water; not equivalent to TDS; generally not shown to affect cow performance, although calcium may add to the amount in the diet.
Mineral content: Water can contain a range of mineral elements that are both essential nutrients as well as toxic elements; the table Concentrations of Potentially Toxic Nutrients and Contaminants in Drinking Water Generally Considered Safe for Cattle lists potential elemental contaminants of drinking water with upper-limit guidelines.
Inorganic contaminants: Beyond mineral elements, other inorganic contaminates of concern for ruminants include nitrates, nitrite, and sulfates. Concentrations of nitrate (expressed as nitrate nitrogen) 20 mg/L, cattle may be at risk, especially if nitrate concentrations in the feed are high. Water with nitrate concentrations >40 mg/L should be avoided. General recommendations for sulfate concentrations in drinking water are