the functions of feeds

8/12/2019 The Functions of Feeds

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THE FUNCTIONS OF FEEDS

The feed consumed by animals is used for a numberof different purposes, the exact usage varying somewhatwith the class, age, and productivity of the animal.With all animals, a certain part of the feed is usedfor he maintenance of bodily functions aside from anyuseful production. This is known as the maintenancerequirement. In addition, the various classes ofanimals use feed to take care of the functions forwhich they are kept. Thus, young, growing animals neednutrient suitable for building muscle tissue and bone;finishing animals need a surplus of energy feeds forthe formation of fat; breeding females require feed forthe development of their fetuses, and, followingparturition, for the production of milk; whereas workor running! animals use feed to supply energy for

productive work. "till other classes of animals requirefeed for the production of eggs and wool. #ach of theseneeds will be discussed separately.

Maintenance$n animal differs from an engine in that the

latter has no fuel requirement when idle; whereas ananimal requires fuel every second of the day, whetherit is idle or not.

The maintenance requirement may be defined as a

ration which is adequate to prevent any loss or gainof tissue in the body when there is no production.$lthough these requirements are relatively simple, theyare essential for life itself. $ mature animal musthave heat to maintain body temperature, sufficientenergy to cover the internal work of the body and theminimum movement of the animal, and a small amount ofproteins, vitamins, and minerals for he repair of bodytissues.

%o matter how quietly an animal may be lying in

the stall, it still requires a certain amount of fuel,and the least amount on which it can exist is calledits basal maintenance requirement. The animal man,cattle, and sheep, but not horses! requires about ninepercent more fuel when standing than when lying andstill more for any movement it may make. This explainswhy it is desirable for economic reasons that finishinganimals should eat and then lie down as much aspossible. #ven under the best of conditions, about one&half of all the feed consumed by animals is used inmeeting the maintenance requirements.

GrowthGrowth may be defined as the increase in size of

the muscles, bones, internal organs, and other partsof the body. %aturally, the growth requirements becomeincreasingly acute when animals are forced for earlyusage, such as the training and racing of a two& orthree&year&old horse.


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'rowth has been referred to as the foundation ofanimal production. (oung cattle, sheep, and swine willnot make the most economical finishing gains unlessthey have been raised to be thrifty and vigorous.)ikewise, breeding females may have their productionability seriously impaired if they have been raisedimproperly. %or can one expect the most satisfactoryyields of milk from dairy cows or eggs from layers,unless they were well developed when young. Workhorsesand mules cannot perform the maximum amount of work,and running horses do not possess the desired speed andendurance, if their growth has been stunted or if theirskeletons have been in*ured by inadequate rationsduring the growth period.

Finishing (or Show-ring Fitting)This is the laying on of fat, especially in the

tissues of the abdominal cavity and in the connectivetissues *ust under the skin and between the muscles.

The composition of a ration for fitting may be thesame as for maintenance, but it must be supplied inlarger quantities.

In practical fitting rations, higher condition inmature animals is usually obtained through increasingthe allowance of feeds high in carbohydrates and fats a more liberal allowance of grains. $ny surplus ofprotein may also serve for the production of fat, butusually such feeds are more expensive and are not usedfor economy reasons. In fitting mature animals, verylittle more proteins, minerals, and vitamins arerequired than for maintenance. In fitting young,growing animals, however, it is essential that inaddition to supplying more carbohydrates and fats ample proteins, minerals, and vitamins be provided.

In general, the more feed a growing or finishing

animal consumes, the more economical will be its gains.+or example, it may be assumed that a calf requires lb of feed daily to maintain itself, when making nogain. With an additional - lb of feed, or a dailyration of lb, it gains / lb daily in weight. If theration is increased by another - lb, bringing the dailyallowance to /0 lb, it gains 0 lb daily in weight.Thus, each - lb of feed over and above the maintenancerequirement lb per day for maintenance! produces again of / lb in liveweight. 1n the basis of total feedconsumed, however, the first pound of gain requires a

total of lb of feed the first lb for maintenanceand an additional - lb for gain!, whereas the nextpound of gain only requires an additional - lb of feed.These facts, as illustrated in this oversimplified way,are the basis for the statement that for economicalfinishing the feeder should get every possible ounce offeed 2under their hides.3 The chief difference between


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good and poor feeders is in the amount of feed abovethe maintenance requirement that they are able toconsume. This also shows why it is necessary to haveanimals with ample feed capacity.

Repro !ction (Eggs) an "actation4egular and normal reproduction is the basis for

profit on any farm or ranch. 5espite this undeniablefact, it has been estimated that from 06 to 768 of allmatings are infertile, that 078 of all cows culled fromdairy herds are removed because of reproductiveinefficiency, that the overall average 9." calf crop ofall cattle beef and dairy combined! is only ::8, that78 of all ewes are sterile, that only 768 of all maresbred actually produce foals, and that /78 of all sowsbred fail to produce litters. With birds, thedevelopment of the egg is the chief part ofreproduction. ertainly, there are many causes ofreproductive failure, but most scientists are agreedthat inadequate nutrition is a ma*or one.

With all species, most of the growth of the fetusoccurs during the last third of pregnancy, thus makingthe reproductive requirements most critical during thisperiod. The ration of the pregnant female should supplysufficient amounts of protein, minerals, and vitamins.

With females of all species, the nutritive

requirements for moderate to heavy milk production aremuch more rigorous than the pregnancy requirements.There is special need for a rather liberal protein,mineral, and vitamin allowance.

In case of young, growing, pregnant females,additional protein, minerals, and vitamins, above theordinary requirements, must be provided; otherwise, thefetus will not develop properly or milk will beproduced at the expense of the tissues of the dam.

It is also known that the ration exerts a powerfuleffect on sperm production and semen quality. Too fat acondition can even lead to temporary or permanentsterility.


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be supplied in the form of additional grain.Theoretically, the protein is not drawn upon so long asthe other nutrients are present in adequate amounts.+rom a practical standpoint, however, it is usuallydesirable to feed more proteins than the maintenancerequirement, merely to ensure that the animal can makeefficient use of the remainder of the nutrients on theration. When a ration too low in protein is fed, morefeed is required because the animal is unable toutili=e the ration efficiently. +or work animals, themineral and vitamin requirements are practically thesame as for comparable idle animals except for thegreater need for salt because of increasedperspiration.

#oo%Wool is a high&protein product. Thus, a shortage

of protein in the ration will lessen wool production,even though the total amount of the ration is adequate.It is also known that both the quality and quantity offiber may be materially lowered if the animals aresub*ected to unfavorable thrift or health. If suchperiods are of relatively short duration, tender spotsweak spots! appear in the growth of the fiber.

the functions of feeds

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