Dairy By-Products in Poultry Nutrition: A Complete Guide

Introduction

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 raised as layers, broilers, or for other purposes. The fact that 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 poultry diets. The next step in 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 birds. As these two explanations are provided, it becomes evident in which ways poultry diets can be supplemented with milk by-products, and further benefits to poultry health achievable through medicinal application of milk products can also be explored.

The major goals of this paper are to explore and examine the relationship of milk processing — specifically the formation of cheese and other by-products — to the diets of poultry. To accomplish these goals it is useful to analyze several interrelated and, in many ways, interdependent concepts. The first goal is to provide a comprehensive overview of milk by-products derived primarily from the production of cheese. In addition, it is necessary to identify the general nutrient contents of milk by-products, specifically as they relate to 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.

Prior to engaging in any analysis of milk processing and the resulting by-products it is useful to describe the 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 occurring among farm animals happen in the poultry sector and can therefore be influenced by many variables. 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 feedstuffs should be of major importance to anyone involved in raising these birds.

Poultry Development and Nutritional Requirements

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

Because of milk's remarkable ability to meet the nutritional needs of animals, it has become extremely attractive as feed. However, because of the costs involved relative to other feed sources, milk is often reserved for only the youngest animals. In addition, fresh milk products are often unwieldy and extremely difficult to distribute, and when considering how quickly they deteriorate during transport, they become even less attractive as a long-term food source. There are also nutritional considerations that must be taken into account when using milk and milk by-products as feed. Milk is low in iron and copper, making animals that rely on it as their primary or only food source susceptible to various illnesses or deficiencies. One such deficiency caused by the absence of important minerals is anemia, 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 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 they provide.

Depending on the type of cheese being produced as well as the other by-products being sought by the manufacturer, 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 desired fat content, it is homogenized to prevent the material from separating into its constituent parts.

Milk By-Products: Overview and Cheese Manufacturing

Prior to processing milk into cheese, a number of steps must be taken to ensure that the milk is pure and free of contaminants. To adequately prepare milk for cheese manufacturing, the product must be heat treated. Heat treatments include pasteurization, sterilization, and ultra-heat treatment (UHT). Milk pasteurization is performed to kill bacteria by heating the liquid at 74°C for fifteen seconds. This level of pasteurization is commonly called low-temperature pasteurization; while it kills harmful organisms, the process also inactivates some enzymes while allowing others to remain active. High-temperature pasteurization and ultra-high-temperature (UHT) pasteurization heat at 90°C and 145°C for fifteen seconds respectively, sterilizing the milk completely but also causing 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 discussed below. The major components in milk are water, lactose, fat, protein, minerals, and other compounds that are particularly important in maintaining proper animal health. 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 triglycerides and is a powerful source of energy that meat birds require in order to develop appropriately. Different types of proteins available in milk are referred to as whey or casein. These proteins contain important amino acids that serve as building blocks for the physical material of the birds and must be part of the diet whether milk by-products or other feedstuffs are provided. Milk contains significant amounts of calcium and phosphorus that are important for skeletal formation as well as many physiological functions. These and other compounds found in milk by-products are very attractive for use in developing animals, but understanding how to access the separate components requires a closer look at the cheese manufacturing process.

Cheese manufacturing can be divided into four main steps: coagulating, draining, salting, and ripening. Prior to and during the manufacturing process, various milk by-products can be derived.

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

Milk curd possesses the vast majority of the fat and protein, while virtually all of the lactose and some of the vitamins, minerals, and protein reside in the whey. As this separation process takes place, it is encouraged by the cooking of the curd, which facilitates further whey removal. It is helpful to note that the coagulation process is managed carefully to ensure that the proper amounts of nutrients are divided in accordance with the manufacturer's needs. For example, the whey by-product is an exceptionally valuable commodity with 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 cheese as desired by the manufacturer. These phases help determine the texture, flavor, and nature of the cheeses produced and are governed by additional ingredients, adjusted humidity, and the duration of ripening. However, it is prior to and during the coagulation phase that the relevant milk by-products used in feed are collected.

Conclusion

The use of milk by-products in the feed of poultry is an exciting subject with far-reaching implications. Milk by-products are considered by many to be substantially better than bone meal or blood meal, which are frequently used as sources of protein in poultry feed. With the substantial amount of milk production combined with growing concerns over the purity and safety of feedstuffs, it may be that milk by-products become even more popular in coming years. Considering that these materials include high-quality protein in addition to certain vitamins and minerals, milk by-products — though sometimes more expensive — may ultimately be determined to be worth the investment.