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In almost all biological systems, it is important that pH not deviate much from a fixed value. For example, for blood to carry oxygen from the lungs to tissue, pH must be maintained very close to 7.4. When rumen pH is either too high or too low, microbial fermentation and absorption of end products of that fermentation are less than optimal. Buffers, and other compounds, are added to rations for ruminant animals to aid in maintaining both blood and rumen pH in the desired ranges.

What is pH?

Maintenance of blood pH, in terms of animal survival, is extremely important. Supplying oxygen to tissues and temperature regulation are the only functions that take precedence over maintenance of proper acid-base balance. While it is extremely important to recognize this fact, the first part of this article will focus on the role of buffers in the digestive tract.

The term pH is commonly used to describe the acidity or alkalinity of solutions. In regards to this discussion, the item of interest, however, is not pH, but what it represents, which is the concentration of hydrogen ions. Use of the term pH to describe acidity may be slightly confusing as it is not a numeric scale but a logarithmic scale. A change in rumen pH from 6.0 to 6.5 may appear to be slight, only 8 percent, but represents a 316 percent reduction in hydrogen ion (acid) concentration.

What are buffers?

Buffers are defined as compounds that resist change in the pH of a system. While rumen pH can vary dramatically, the normal range may be considered to be from 5.7 to 6.7. In this range, bicarbonate is the primary buffering system in the rumen, although there are other minor buffers as well.

Bicarbonate, as a buffer, is most effective at a pH of 6.37 and is effective at a range of from 4.67 to 8.07. Commonly used compounds (such as sodium sesquicarbonate, potassium carbonate, sodium carbonate, magnesium oxide, calcium and magnesium carbonates) are more properly termed alkalizing agents based on their mode of action. Practically speaking however, this distinction only applies to magnesium oxide as all other compounds mentioned add to the rumen bicarbonate pool.

A byproduct: Volatile fatty acids

Volatile fatty acids formed during rumen fermentation are waste products produced by bacteria. Rumen fermentation is an anaerobic process and, as a result, conversion of carbohydrates in feed to microbial cells is greatly exceeded by the amount of these various waste products. When these waste products are absorbed and utilized by the host animal, the amount of energy to provide for cell maintenance and growth greatly exceeds that available to rumen bacteria. Most common among the volatile fatty acids produced during fermentation are acetic acid, propionic acid and butyric acid. It has been estimated that if the rumen were not buffered, the pH may drop to approximately 3.0.

Dissociation constants vary for common volatile fatty acids. This means that not all acids produced during rumen fermentation produce the same level of acidity. If propionic acid has a relative rank of 1.0, then butyric acid and acetic acid are 1.09 and 1.30, respectively. Lactic acid, found in silage and produced in relatively large quantities when animals are not well adapted to high-grain rations, is much more acidic than the volatile fatty acids. Lactic acid is 10.3 times more acidic than propionic acid, which can lead to problems when animals consume large amounts of silage. None of these organic acids can compare to hydrochloric acid, which is more than 70,000 times as strong an acid as propionate.

Neutralizing acid

Buffers also vary in their ability to neutralize or completely consume acid. Based solely on chemistry, one can rank buffers on a scale of from one to 10, 10 being the best. Table 1 shows a comparison of theoretical acid-consuming capacity and measured acid-consuming capacity. It should be noted that while magnesium and calcium compounds rank higher than sodium and potassium compounds, there is much more variability in quality for the former. Some calcium and magnesium buffers and alkalizing agents are relatively poor acid consumers, while others are quite good. Generally speaking, these are unrefined products and can vary based on the particular deposit from which they are mined. Potassium and sodium buffers and alkalizing agents are usually refined products and, as such, are more consistent in performance. Unrefined trona ore, predominantly sodium sesquicarbonate, tends to be less variable in performance than mined calcium or magnesium products. In general, products should be chosen based on consistency of measured results.

Quantities of buffers added to rations depends on a number of factors: rate and extent of rumen carbohydrate fermentation, quality and quantity of fermented feeds (such as corn silage) and passage rate are some of the most important. It is possible to calculate the amount of buffering required if ration composition and kinetics of rumen degradation are known.

Plant cell walls and starch are carbohydrates varying dramatically in rate and extent of rumen degradation. If one assumes rumen losses of plant cell walls are 40 percent, then for a cow consuming 50 pounds of dry matter (DM) with 28 percent plant cell walls, theoretical production of acetic acid, propionic acid and butyric acid from cell wall fermentation are 2.0, .90 and .80 pounds, respectively. Bacterial waste, as volatile fatty acids, are 3.7 pounds and .65 pounds of microbial cells are produced from 14 pounds of cell walls. If the same ration contained 35 percent starch and that starch was 90 percent fermented in the rumen, theoretical production from that portion of the feed yields 10.5 pounds of volatile fatty acid and about 2.0 pounds of microbial cells.

Rations higher in fiber require less acid neutralization partly because of higher salivary secretions and lower rates of acid production. Feed fiber, especially that found in legumes, can remove acid much in the same way a water softener removes calcium from water (ion exchange). Total ion exchange capacity of most rations is limited; the equivalent of a fraction of an ounce of sodium bicarbonate. Amounts of buffers added to the ration can be calculated based on ruminal acid production, salivary bicarbonate production and feed pH. Excessive acid neutralization can be as deleterious as insufficient buffering, as dissociated volatile fatty acids are not absorbed as well as undissociated volatile fatty acids. When rumen pH rises too high, absorption of volatile fatty acids across the rumen wall ceases, as will rumen fermentation. At a pH of 6.0, approximately 95 percent of acetic acid is dissociated, as are 93 percent of both propionic and butyric acids. It is interesting to note that volatile fatty acid absorption across the rumen wall is more rapid shortly after a meal, before salivary secretion increases.

Since estimates regarding production of volatile fatty acids and microbial cells have been made, a brief (unrelated to buffers) yet important discussion follows. Plant cell walls are important in overall rumen function; however, the role of rumen fermentable starch cannot be overemphasized. As can be seen from the previous example, the contribution of starch fermentation to microbial cell growth is much greater than plant cell wall fermentation. At amounts that might be found in a typical dairy ration, starch has the potential to grow three times the amount of microbes and nearly five times the amount of propionic acid as plant cell walls. The implications of this, as regards milk production, are clear.

Regulating blood pH

While rumen pH can vary over a broad range, blood pH does not. Under conditions commonly found in the rumen, acid content, as measured by pH, can vary 10 fold. Blood acid content is highly regulated and varies by no more than 10 percent from the average. Normal blood pH is 7.4; animals are alkalotic when pH is greater than 7.45 and acidotic when pH is less than 7.35. Metabolism must be altered to correct either condition as blood pH outside the range of from 6.8 to 7.8 results in death.

Regulation of blood pH is not as simple as the situation in the rumen. Hydrogen ions (acid) in blood are positively charged and in order to maintain a zero charge, one of two events must occur. Introduction of acid (positively charged) must be accompanied by the addition of a negatively charged ion (anion) such as chloride or bicarbonate, or the loss of positively charged ions (cations), such as sodium or potassium. Potassium, sodium and chloride are classified as dietary fixed ions; they are quantitatively absorbed from the gut, are not metabolized and excesses are excreted in urine.

Combustion of feed indicates effects on acid-base balance; ash from cereal grains is acid, while that from forages is alkaline. Cattle are much more tolerant of alkalosis than acidosis and, as such, require a slight dietary excess of positively charged fixed ions. The magnitude of this excess is determined by a number of factors including metabolic state.

Growth is a state when animals are in a negative acid balance; while catabolic states, such as starvation, represent a positive acid state. Acid-base imbalance affects multiple metabolic processes; among these are impaired glucose metabolism and transport of compounds across cell membranes. Ultimately, under prolonged conditions of acid-base imbalance, animal health and efficiency are reduced.

Modern management practices increase energy density to improve production, primarily with increased intake of cereal grains. Until recently, no attention was paid to acid-base balance in cattle. It has been suggested that benefits resulting from the addition of buffers, such as sodium bicarbonate, relate as much to fixed ion addition (sodium) as to acid neutralization.

Sodium, potassium, chloride, phosphorus, sulfur, calcium and magnesium are commonly included in equations describing dietary acid-base status. Phosphorus, sulfur, calcium and magnesium may warrant inclusion occasionally, but these are typically added to rations to satisfy requirements. Unlike sodium, potassium and chloride, absorption of phosphorus, sulfur, calcium and magnesium is variable and often low. Sulfur is a constituent of several amino acids, and as such, metabolic state influences the contribution of sulfur to acid-base balance. Equations describing dietary fixed ion differences must be predictive of acid-base balance across all metabolic states. In addition, the simplest equation describing a system is to be used in preference to a more complex one that does not increase accuracy of prediction.

Summary

Regulation of acid-base balance in ruminants is a more complex system than that in non-ruminants. To meet the demands of high production, feeds are included in rations that can disrupt ruminal and metabolic processes. Buffers are added to rations to mitigate negative effects of acids produced during fermentation on rumen health and function. Additionally, buffers allow blood pH to remain in a range that maximizes performance and animal health. PD

References omitted but are available upon request at

After several years of relatively cheap grain prices, corn and soybean prices have increased significantly. The increase is primarily due to greater demand for corn and soybeans to produce ethanol and biodiesel. Most economists suggest that these higher prices will be with us for the foreseeable future. Since other feedstuffs are typically priced to reflect the corn and soybean market, the cost of almost all feed ingredients has increased.

Since feed is the largest single cost in producing milk, most producers review their feeding program to see if there are ways to reduce these costs. Any changes made to rations should only occur after a thorough review of the feeding program and must take into account the impact a change could have on other aspects of the overall operation. This [article] will review factors that affect feed cost, methods for determining the value of byproduct feeds, review issues related to using byproduct feeds and provide some suggestions for dealing with feed cost over the long haul.

Factors that affect feed cost

Rations are formulated based on animal requirements and the quality of feeds available. In regards to animal requirements, higher-producing cows have lower feed cost per cwt. This is because maintenance requirements, the amount of feed required to maintain basic body functions, are diluted by higher levels of milk production. Because of this, it is still more profitable to feed for high levels of milk production even when feed costs are high. The key is to use a realistic level of production for formulating rations.

Forage quality is one of the biggest factors affecting total feed cost. As forage quality increases, less concentrate is required to provide the additional nutrients needed to support maintenance, milk production, reproduction and health. Considerable advances have been made by seed companies as they work to identify hybrids that not only yield well but are more digestible, so that the cow can obtain more metabolizable energy in support of milk production.

We also have a better understanding of the importance of timely harvest and forage processing to get the most out of our forage. Research has also demonstrated the importance of managing the forage during storage and feeding to prevent secondary fermentation of silage or deterioration of hay once it has been baled.

The factor most producers watch and talk about most is the cost of supplements, especially corn and soybean meal, as they are used to establish the price for most ingredients. Fortunately, there are a variety of feedstuffs available that can supply energy and protein in rations for dairy cows besides corn grain and soybean meal. The list of possibilities includes traditional grains and protein supplements as well as numerous byproducts from the production of food, fiber or fuel. There are also other unusual byproducts available in some areas that can be fed if the producer is set up to handle those ingredients. The initial attraction of byproduct feeds is their lower cost, but there are other factors to consider in addition to cost.

Most producers feed one or more additives which increase feed cost. Several additives have research data to validate their usefulness and document their potential to improve production or health. These additives when used according to directions provide a good return on investment and should be continued. However, there are additives on the market that do not have unbiased information to support their potential usefulness. Often these products are included in the ration because they may help solve a problem. The use of these additives should be critically reviewed as to their need and usefulness since they add to the cost of production and may not provide any return. No product, with or without research documentation, should be used as a Band-aid for poor management.

The same is true for certain ingredients as well. Remember:

•There are no magic bullets.

•If it sounds too good to be true, it probably is.

•No product can change the laws of science.

Determining the cost of feed ingredients

There are several methods for comparing the prices of byproduct feeds. Many ration formulation programs calculate the value of each feed ingredient based on the nutrient requirements of the diet and the nutrients available from ingredients offered. This method provides specific information for that particular situation, but most producers do not have the software to perform these calculations.

More commonly, producers use programs specifically designed to compare the value of several feeds compared to a reference feed such as corn and soybean meal. One program commonly used is the FEEDVAL program available from the University of Wisconsin (http://www.wisc.edu/dysci/uwex/nutritn/spreadsheets/FEEDVAL-Comparative.xls). This program calculates the value (price/ton) based on the dry matter (DM), crude protein (CP), total digestible nutrients (TDN), calcium (Ca), and phosphorus (P) contents of each feed compared with the test feeds (shelled corn, 48 percent CP, soybean meal, limestone and dicalcium phosphate).

The nutrient composition of the feeds can be changed to match the products available in your area as well as the percentage feed loss. The values for forages are expressed on a dry-matter basis whereas all other ingredient values are expressed on an as-fed basis. A second version of this program (FEEDVAL4) is available that calculates the value of feeds based on undegradable and degradable protein, TDN, fat, Ca and P content using blood meal, urea, tallow, shelled corn, limestone and dicalcium phosphate as reference feeds.

Both programs allow the user to compare a wide variety of feedstuffs based on their primary nutrient content. The program can also be used to determine the feeding value of home-grown feedstuffs. There are other similar programs available as well as similar functions in many of the ration formulation programs available today.

Producers should compare similar types of ingredients when selecting those they will ultimately use. If you are not sure how a particular ingredient would fit into your ration, be sure and consult your nutritionist before you purchase any new ingredient. Most nutritionists keep up with ingredient cost and can provide a considerable amount of help when looking at any new ingredient.

There are several listings of ingredient prices that can be accessed by the internet including the University of Missouri site (http://agebb.missouri.edu/dairy/byprod/). These sites are good for information, but you will need to contact a broker to get a delivered price to your farm.

The true cost of a feed ingredient may be different from what we initially paid. There are additional delivery costs for byproduct feeds that may not be included in the initial quote. If you must receive a semitrailer load of feed that will be fed over an extended time, you should include an interest cost on the money tied up in inventory. Shrinkage varies from 3 to 7 percent for dry ingredients and 15 to 35 percent for wet ingredients. Sometimes special storage or handling is required, compared to using a complete feed, and these costs should be taken into account. The major cost in this analysis is typically shrinkage and delivery cost when the feed is used in a normal time frame.

Nutrient form and balance

Most feedstuffs provide a combination of nutrients but are classified according to the primary nutrient provided. In most situations, it is desirable to include a mix of feedstuffs in the ration to help provide a more desirable balance of nutrients to optimize ruminal fermentation and health. For example, high-fiber energy supplements are useful for reducing the starch concentration of rations based on corn silage and supplemented ground corn.

For diets containing high-quality legume silage or high protein grass silage, protein supplements that contain rapidly degraded protein would not be desirable. However, there are other situations in which the use of urea or another source of degradable protein should be fed even though it may not be the least expensive protein source compared with soybean meal.

When byproducts are included in rations, we must be aware of the amount of phosphorus these ingredients add to the ration. With greater attention on nutrient runoff and its negative effect on the environment, we must consider the impact of overfeeding phosphorus and other nutrients on the long-term aspects of whole farm nutrient balance. Several byproducts have relative high levels of phosphorus, which is one of the primary concerns. If multiple feeds with higher-than- average concentrations of phosphorus are fed, the phosphorus content of the ration will be well above National Research Council (NRC 2001) recommendations. The long-term impact may be a limitation in the amount of manure that can be applied to your land – which could reduce any future expansion plans with the purchase of additional land.

Nutrient variation

When producers make the decision to use a byproduct, they also assume responsibility for quality control of that ingredient. Variations in the nutrient contents of byproduct feeds occurs because of differences in the variety of grain used for processing, fertility of soil the crop was grown on, processing method used by the plant to extract the primary products, blending of multiple byproducts together by the manufacturing plant and storage conditions.

The expected variation for some byproducts is greater because of the different types of processing in the industry. The variation in nutrient content in a byproduct is typically much higher for the industry compared with that from a single source. Processing methods used by manufacturers have changed greatly during the last decade. These changes allow the processor to more effectively remove the primary product (starch, oil, etc.) producing byproducts that have a different nutrient profile than that listed in many references.

For example, the processing methods used to produce ethanol have changed greatly which produce distillers – dried grains with solubles (DDGS) – with a different nutrient content than previously available. Part of this variation is due to a new generation of plants that have come on-line in the past few years that produce DDGS that are reported to have higher nutrient value than DDGS produced by older, more traditional ethanol plants.

Processing technology is constantly being refined to improve the extraction of primary ingredients. Researchers are also looking at ways to decrease the amount of nutrients such as phosphorus in byproducts, so that their use in animal feeds will improve whole farm nutrient balance and maintain water quality. Some processing technology being developed will allow the production of custom byproducts for feeding in the near future, which will be advantageous for dairy producers. For these reasons, producers should sample feedstuffs on a regular schedule to keep track of the variation and any change in nutrient content that may impact the nutrient content of the diet.

Quality issues

Another aspect of quality control is safeguarding against potential contaminants in the byproduct feeds. Normally, the raw materials used for manufacturing food are screened for mycotoxins and other potentially harmful contaminants before use, and the byproducts are safe for animal consumption as long as they are handled properly after they leave the plant. There have been a limited number of cases in the past where byproducts from non-food industry sources were contaminated, resulting in either the death of numerous animals or condemnation of the animals. Producers should ask about the quality control measures used by the manufacturer to safeguard against contamination of the byproduct with mycotoxins or other harmful compounds. As the production of biofuels increases, there may be situations where treated seed or fermentation products from other industries are used to make ethanol or biodiesel. The byproducts from these products could potentially be fatal to the animals consuming them.

Occasionally, there are unusual byproducts that may become available for use. Some examples include: candy, cocoa byproduct, fruit pomace, fresh vegetables or fruits, vegetable residues or other products that are not typically fed. In some cases, there isn’t any information available on the nutrient content of these feeds and the producer must run analyses before they can be included in a ration. Many of these products have handling issues (ex, individually wrapped pieces of candy), but other products may have some compounds (either natural or added during processing) that would limit their use. In these cases, the producer should seek the assistance of a nutritionist with experience in this area.

Energy supplements other than corn grain

Either you have already looked at replacing some or all of the corn in the diet or you will in the near future. Corn is fed primarily as a source of fermentable energy. The energy is primarily in the form of starch which is digested at varying rates depending on how finely it has been ground or how it has been processed. There are several byproducts that can be used to partially replace corn grain in the diet. Some of the primary byproducts to consider include: hominy feed, soybean hulls, bakery byproduct, citrus pulp, molasses, wheat middlings, brewers grain, corn gluten feed or distillers grain. The energy in many of these byproducts is primarily in the form of digestible fiber, but some byproducts contain processed carbohydrates or sugar in the case of bakery byproduct and molasses, which should be handled differently in the ration.

Another source of energy is to feed more fat from sources such as whole cottonseed, whole soybeans, tallow, animal-vegetable blends or inert fat supplements. When multiple products that contain higher concentrations of fat are fed, the total amount of fat in the diet must be limited to avoid any negative effects on fiber digestion, animal health and milk fat depression. Considerable research has been conducted on each of these and each has advantages and disadvantages. The amount of corn that can be replaced by one or more of these byproducts depends on the quality and type of forage fed, production level and feeding system constraints.

Distillers grains have received a lot of press recently because this is the primary byproduct from the production of ethanol. As pointed out previously, there is a good deal of variation in the nutrient content of distillers grains. Some plants have taken extra steps to produce a more consistent product and typically collect a premium for their distillers grains. Research has demonstrated that distillers grains can provide up to 40 percent of the total ration DM, but this is not practical for most dairies.

Besides containing relatively high concentrations of fat, distillers grains also contain high levels of phosphorus. Like other byproduct feeds that contain higher concentrations of phosphorus, high feed rates increase the amount of phosphorus in the manure which builds up in the soil. The long- term implications include lower application rates of manure to land and limitations on herd expansion without purchasing additional land.

Suggestions for dealing with higher feed cost

It is important to review all aspects of your feeding program from time to time, independent of feed prices. This review should address several questions including: what are the primary weaknesses of the current feeding program? Often the primary weakness is related to forage quality, feed bunk management or some other aspect that is preventing your cows from being as productive as possible rather than the ration formulation.

If cow comfort is not as good as it should be, the cows will not respond completely to any change in the feeding program. The same is true for all of the little things that should be done to make sure each cow has feed when she is ready to eat, cows have plenty of bunk space, unrestricted access to water, water is cleaned each week and there is a good preventative health program in place.

The DM content of any wet feeds (silage or wet byproducts) should be measured routinely and rations adjusted as needed. This will reduce some of the variation in the nutrient content of the final ration and keep cows on a more consistent diet. Sample forages and other home-grown feed and have them analyzed. Use the analysis to fine-tune your rations. Home-grown forages commonly have greater variation than purchased feeds, so it is very important to sample and analyze frequently. Fine-tuning the ration can make a difference not only in milk production but also the amount of purchased feed needed and total feed cost.

Review mixing procedures and information used for mixing rations with the feeder to make sure that the rations mixed are the same as those formulated. A misplaced decimal or transposed number can be very costly in both feed cost and lost production. Too often the feeder doesn’t understand (or forgets) the importance of adding the correct amount of each ingredient and the impact of a mistake on cow health and production on the bottom line.

Manage feedbunks to optimize intake. Old feed should be removed each day to prevent spoilage of new feed and encourage consumption. Feed should be pushed up several times a day so cows have access at all times. Provide adequate bunk space for each cow. Normal recommendations are for a minimum of 2 linear feet per cow and more for fresh cows. Adjust feeding amounts to minimize refusals. Normal recommendations are for 3 to 5 percent depending on how well you can time feed delivery. If feed refusals are primarily the fractions that are sorted out by the cow, the amount of feed offered probably should be increased, and there are opportunities for improving feed mixing and processing.

Dairy efficiency, the pounds of milk produced for each pound of DM consumed, is a good tool to help evaluate the effectiveness of a ration and economics. High-producing cows should have a dairy efficiency greater than 1.6, whereas the majority of the herd should average 1.5. Dairy efficiency is lower for late-lactation cows and during heat stress. Supplemental cooling should be optimized to maintain production and dairy efficiency.

Establishing production groups, when possible, allows different rations to be formulated according to need, reducing total feed cost. It may be enlightening to determine the value of the milk produced by each cow, either current daily milk or lactation average, and compare that with the current feed cost to see which cows are profitable.

Summary

As we look for ways of controlling feed cost in light of increasing corn and feed prices, it is important to remember the basic factors that contribute to total feed cost. A careful analysis of the total feeding program that includes forage quality, availability and cost of byproduct feeds, feeding management and cow comfort should be conducted routinely to determine where cost can be trimmed and feed utilization can be improved. Given the current push for developing alternative fuels from corn and soybeans, producers must fine-tune their feeding management to maintain profitability. PD

References omitted but are available upon request at

—Excerpts from 2007 Kentucky Dairy Conference Proceedings

Cows cool themselves primarily by evaporating water from their body surface and their respiratory tract during hot weather. The body evaporation process in cattle is in a vapor form emanating from pore-like structures. The cow can sweat only to a limited degree, primarily in the brisket area. As heat stress increases, cows increase their respiration rate to the point of panting to help increase evaporation from the respiratory tract. As the air temperature surrounding the cow approaches body temperature, sensible heat (body warms the air) loss becomes minimal.

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Improving milk quality often consists of managing a complex system that includes people, cows, machines and the environment. Surveys of veterinarians and other professionals working with dairy producers indicate that barriers to improvement of milk quality are primarily related to motivation and implementation rather than lack of technical knowledge or skills.

In a survey of 165 Wisconsin dairy professionals, the existence of too many other problems (55 percent) and few incentives for production of high-quality milk (48 percent) were the predominant reasons cited for failure of farms to improve milk quality. Only a few responders indicated they felt the need for additional on-farm training programs (24 percent).

During the summer of 2006, farmers that had completed the Milk Money program were asked an open-ended question that stated, “What is your greatest challenge in maintaining production of high-quality milk?” The most common responses were related to employee management (mentioned by 26 percent of responders), followed by management of the environment of the cow (mentioned by 14 percent of responders) and maintaining consistency in the milking process (mentioned by 11 percent of responders).

It is no mystery why employee management is mentioned so often, because 51 percent of farms responding to a post-Milk Money survey indicated that they employed Spanish-speaking employees, yet only 15 percent indicated they had any ability to speak or understand Spanish and 40 percent had never employed an interpreter.

These communication challenges are a fundamental reason why producing high-quality milk continues to be a challenge for many farmers. The ability to implement recommended management practices is an essential aspect of quality milk production. Implementation is dependent on the ability to clearly communicate the value of these practices and to motivate farm personnel to consistently apply them. PD

References omitted but are available upon request at

—From University of Wisconsin Milk Quality Resource website

“Gate to plate” and “farm to fork” are two common phrases that illustrate how during recent years the demands by consumers for greater food safety and animal welfare standards have brought increased attention on all stages of the animal-based food production continuum. The vital link within the food system of feed manufacturers producing safe and wholesome animal feed has not been exempt from this attention.

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The proportion of lactating dairy cows on commercial farms that become pregnant at the first insemination has decreased over the last 25 to 30 years.

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