Milk by Products and There Effects on Growth in Poultry

Poultry

Milk from the cow is one of the most versatile and important substances in the human diet as well as in the diets of many animals and in particular in the diet of poultry that are being raised as layers, broilers or for other purposes. The fact that this milk can be processed into many different forms adds to its versatility and provides a wide array of by-products from which specialized uses can be determined. Understanding the basic array of materials that can be obtained from processing milk is the first step in understanding how those products can be used in the diets of poultry. The next step of understanding the relationship between dairy by-products and the benefits they can provide to poultry comes through examining the nutritional content of those by-products for the feeding and development of poultry. As these two explanations are provided it becomes evident in which ways poultry diets can be supplemented with the milk by-products and to examine further benefits to poultry health that can be achieved through medicinal application of milk products.

The major goals of this paper are designed to explore and examine the relationship of milk processing for the formation of cheese and other by-products to the diets of poultry. To accomplish the goals it will be useful to analyze several different concepts that are interrelated and in many ways interdependent. The first goal is to provide a comprehensive overview of milk by-products that are derived primarily from the production of cheese. In addition, it is necessary to identify the general nutrient contents of milk by-products specifically as it relates to those ingredients most beneficial to poultry development. Third, the manner in which these by-products can be utilized as feedstuff or as supplements for poultry diets is included in the analysis. As a function of this analysis it will be clear which components of the milk by-products can be applied in poultry diets for health maintenance and promotion. Ultimately, the goal of the paper is to provide a complete overview of milk by-products and their use in poultry diets.

Poultry Development

Prior to engaging in any analysis of milk processing and the resulting by-products that are produced it is useful to describe nutritional considerations related to developing poultry. "The ability to convert nutrients to the final products depends on a variety of external and internal factors, such as age, sex, genetic background and housing system." (Pishnamazi et al. 163) These factors are important to keep in mind especially considering that the vast majority of developmental problems that occur among farm animals happen in the poultry area and can therefore be influenced by many things. One reason for developmental problems in poultry has to do with nutritional deficiencies that occur out of ignorance, illness or neglect. Thus, the study of nutritional needs and the corresponding nutrient makeup of poultry foodstuffs should be of major importance to anyone involved in raising these types of birds.

Poultry development requires a significant amount of energy and the correct nutrients to progress properly. For example, Zinc is an important micronutrient that can cause growth retardation when lacking in quantities. Like many nutritional substances, zinc has a relationship to the overall health of the birds and quantities required may vary based on other dietary inputs. Another example of critical nutritional components for the proper development of poultry is protein. Protein is essential because of its role in providing structure and form to virtually every cell. Protein is the foundation of good health and is used in a variety of bodily functions. Providing proper amounts and types of protein are of paramount importance for the quality of the poultry that is developed. Some of the other important nutrients that poultrymen are concerned with assuring are present and in the correct quantity are calcium, phosphorus and cholecalciferol. Each of these nutrients must be provided in the proper ratio to assure proper health and development.

Milk By-Products

Because of milk's amazing ability to meet the nutritional needs of animals it has become extremely attractive to use as feed. However, because of the costs involved relative to other sources of feed, milk is often reserved for only the youngest animals. In addition, fresh milk products are often unwieldy and extremely difficult to easily distribute which, when considering how quickly they deteriorate during transport makes them even less attractive as a long-term food source. There are also nutrition considerations that must be taken into account when considering milk and milk by-products as feed. Milk is low in iron and copper making the animals that rely on it as their primary or only food source susceptible to many illnesses and/or deficiencies. One such deficiency that can be caused by the absence of important minerals is anemia which is manifested by the colorless nature of what is often referred to as white veal. When this condition is present, it is often the result of calves that have been fed almost entirely on milk that has not been fortified with the necessary micronutrients. Nevertheless, fresh milk and milk by-products can be used in a number of ways in the raising of broilers, layers and turkeys because of the many benefits that they provide. This section of the paper includes some of the processes by which milk by-products are generated during the production of cheese and provides a brief description of each by-product discussed.

Milk Preparation Precedes Cheese Manufacturing

Depending on the type of cheese being produced as well as the other by-products that are being sought by the manufacturer, the milk is separated into whole milk, semi-skimmed milk and skimmed milk. This is accomplished by placing the milk in a centrifugal separator which divides lighter fatty phase materials from the non-fat matter. Once the milk is prepared at the level of fat content that the manufacturer desires, the milk is homogenized to prevent the material from separating into its constituent parts.

Prior to processing milk into cheese there are a number of steps that must be taken to assure that the milk being used is pure and free of contaminants. To assure that milk is adequately prepared for cheese manufacturing the product must be heat treated. Heat treatments include pasteurization, sterilization and ultra heat treatment or UHT. Milk pasteurization is done to kill bacteria by heating the liquid at 74°C for fifteen seconds. This level of pasteurization is commonly called low temperature pasteurization and while it kills harmful organisms the process also inactivates some enzymes but allows other enzymes to remain active. High temperature pasteurization and ultra high temperature (UHT) pasteurization heat at 90°C for fifteen seconds and 145°C for fifteen seconds respectively and sterilizes the milk completely but also causes progressive deactivation of more enzymes. Once the milk has been sterilized, it is ready for further processing.

Several milk products and by-products are produced as a function of processing whole milk. Some of these components are extremely useful to include in poultry feed as will be discussed below. The major components in milk are water, lactose, fat, protein, minerals and other components that are particularly important in relation to helping maintain proper health for the animals. Lactose is the major sugar or carbohydrate in milk and is composed of glucose and galactose. The fat in milk is for the most part triglicerides and is a powerful source of energy which meat birds demand in order to develop appropriately. There are different types of proteins available in milk and are referred to as whey or casein. These proteins contain important amino acids that are building blocks for the physical material of the birds and must be a part of the diet whether milk by-products are used or other feedstuff is provided. Milk has a significant amount of calcium and phosphorus that are important for skeletal formations as well as many physiological functions. These and other compounds found in milk by-products are very attractive for use in a developing animal but understanding how to get to the separate components requires a look at the cheese manufacturing process.

Cheese Manufacturing and Milk By-Product Production

Cheese manufacturing can be divided into four main steps. It is possible to organize the work done under different headings and into slightly different components but for the purpose of this explanation the process has been divided into coagulating, draining, salting and ripening. Prior to the actual manufacturing process and during the process, various milk by-products can be derived.

'Cheesemaking begins with the application of proteolytic enzymes that coagulate milk to form curds." (Burrington) Coagulation of milk is allowed to begin the process of converting milk into cheese. Coagulation is another word for clotting and describes the physical and chemical changes that take place in the milk which causes the separation of the milk or what is referred to as the curd from the liquid component or what is referred to as whey. The coagulation process also includes the introduction of a bacterial component. The bacteria that are used are not harmful to humans or to the birds.

Milk curd possesses the vast majority of the fat and protein, while virtually all of the lactose and some of the vitamins and minerals as well as some of the protein reside in the whey. As this separation process takes place it is encouraged by the cooking of the curd which facilitates the removal of whey even further. It is helpful to note that the coagulation process is managed carefully to assure that the proper amounts of nutrients are divided in accordance with the needs of the manufacturer. For example, the whey by-product is an exceptionally valuable commodity that has a wide range of applications including its use as a feed supplement. The separated whey is often concentrated to make it more useful as animal feed.

The draining, salting and ripening phases are used to create various forms of cheeses as desired by the manufacturer. However, these phases are not directly relevant to the creation of milk by-products but should be mentioned in at least a cursory fashion. Clearly, the efforts used in these phases help determine the texture, flavor and nature of the cheeses produced and are determined by additional ingredients, adjusted humidity and duration of ripening allowed. However, it is prior to and during the coagulation phase that the relevant milk by-products used in feed are collected.

Skim Milk

As noted previously, the introduction of whole milk into a centrifugal separator removes the fat from the milk. When milk has had most of the fat removed it is commonly referred to as "skim milk." One of the unique factors of skim milk is that during the process of removing the fat, the protein is left in the finished product making it a significant source of the building blocks that all life requires for form and structure. Aside from the relatively high protein content that is available in skim milk is that this by-product also retains a considerable number of water soluble vitamins such as vitamin C Vitamin C is helpful in developing connective tissue and in facilitating important physiological functions so it is of value to avian as well as mammalian life forms. When the fat is taken out the fat soluble vitamins A and D. are also removed. The result is a product that is very digestible and very low in fat but also low in two very important vitamins.

Buttermilk

When whole milk has been churned to manufacture butter, the liquid material that remains is commonly referred to as buttermilk. Unlike skim milk, butter milk retains the fat soluble vitamins that are present in whole milk. Clearly, the fat content of buttermilk is significantly higher than skim milk but the protein content is roughly the same. Buttermilk has a more acidic pH than skim milk and it can serve as a natural laxative. Buttermilk can be maintained in its liquid form or it can be dried to make it easier to transport and include in feedstuffs.

Additional By-Products

There are other by-products that can be produced from milk such as dried skim milk and milk permeate which can have a number of different uses. However, for the purpose of this paper it is of benefit to more closely examine the particular nutritional components that are frequently extracted for use on their own or as a supplement in feed products. In particular, it is beneficial to look at the composition and impact on poultry diets of vitamins, minerals, whey and casein. As these materials are scrutinized it is more evident how they can be used to benefit poultry diets.

Vitamins and Minerals

Milk and milk by-products are significant sources of various vitamins and minerals. Calcium and phosphorous in particular are available in substantial quantities in many milk by-products. These minerals provide significant benefit to developing chicks and are important in increasing bone density allowing for larger growth which supports the production of more meat for broilers and turkeys. However, the amounts of calcium and phosphorus vary with the differing milk by-products that are being considered. For example, whey has relatively little Ca and P. As compared with whole milk so that fact should not be overlooked. Similarly, milk fat contains fat soluble vitamins that are not available in milk by-products in which the majority of milk fat has been removed as was mentioned regarding skim milk.

Whey

Whey protein is the liquid by-product that remains after cheese production. Whey is either fresh or acidified depending on how long it has been allowed to ferment and produce acid. Fresh whey is highly perishable and unstable so it has a very short life meaning it must be consumed relatively quickly. On the other hand, acidified whey that has been allowed to ferment causes the pH level to be lowered somewhat and thus the material is stabilized allowing for longer life of the material. The problem with acidified whey is that it is less palatable so it is less attractive as a feed product unless the flavor can be masked. Whey protein has had most of the fat and casein removed during the process whereby cheese has been manufactured. The process also results in whey being relatively high in lactose with a considerable concentration of important minerals. Whey can be dehydrated resulting in a powdered form enabling it to be transported easily and cheaply. Whey is also a significant source of protein. There are three primary forms of protein in whey as well as a number of enzymes, disease fighting components and hormones.

One of the most significant proteins in whey is immunoglobulin, an antibody-like substance that stimulates and supports the immune function of the animals. Baily et al. point out that this is an increasingly important issue because the overuse of antibiotics has made many strains of bacteria such as E. coli resistant to antibiotics. Whey protein is therefore an excellent feed supplement to give poultry for which disease resistance is an important concern. Whey protein contains many different serum globulins that can play different roles in the developing and growing bird. For example, whey protein contains alpha-globulin, beta-globulin, gamma-globulin and immunoglobulin which are the primary immune-system-stimulating features of whey. The globulins function together to help develop disease resistance and promote good health.

Whey protein is available in different concentrations that are referred to differently so as to note the distinction. Two of the main variations of whey protein are whey protein concentrate (WPC) and whey protein isolate (WPI).

'Whey protein ingredients generally are identified by their protein level and often vary from supplier to supplier. For example, the protein concentration in dry whey ranges from 2 to 13%, whereas whey protein concentrate (WPC) ranges from 34 to 80% whey proteins. The most common form of WPC is 80% WPC, and is typically used as a standard among suppliers. An even more concentrated source of whey protein, whey protein isolate, contains at least 90% whey proteins." (Gorski)

WPI is of significant value in animal feeds although it can be somewhat expensive. The cost is one of the reasons that it is often reserved for feeding during the starter phase of the animal.

Casein

"Intact casein is a fundamental constituent in process cheese because it has important emulsifying properties that significantly affect the texture, stability and melt characteristics of the final product." (Lee et al. 538) Casein is another form of protein that is common to milk and milk by-products. There are three subclasses of casein - alpha-s-casein, beta-casein, and kappa-casein. The casein varieties are distinct molecules with similar structures. Like all proteins, casein is fundamentally a series of amino acids some of which are particularly beneficial for poultry development. Some of the amino acids that are particularly important for the proper growth of poultry such as valine, leucine and methionine are in significant concentrations in casein making it ideally suited for developing animals. "There is no question that breast meat yield, representing a major portion of the protein synthesis in the body, is sensitive to amino acid status of the diet." (Jianlin et al. 60)