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Production systems

Dairy cattle can be reared in ways that vary depending on the resources available to the farmer. Farmers in East Africa practise three main systems: intensive, extensive and semi- intensive.

Intensive system

In the intensive system, dairy cattle are enclosed in zero-grazing units (see design of zero-grazing unit in Appendix 8), where they are provided with all their requirements for feed and water. This method is mainly practised where grazing land is scarce. In Kenya it is mainly practised in high-potential areas of central Kenya and also by urban and peri- urban farmers; in Tanzania it is practised on the slopes of Mt Kilimanjaro and in Uganda around Kagada. The forage can be grown on farm or purchased.
This system has its advantages and disadvantages.
Advantages

• The cow does not waste energy walking in search of pasture.
• It avoids diseases associated with communal grazing.
• It allows dairy farmers with no grazing land to produce milk and make money.
• The manure can be accumulated for improving soil fertility or used to generate biogas for domestic energy use.

Disadvantages

• The method is labour intensive as feeding and cleaning the unit must be done daily.
• The initial cost of putting up a zero-grazing unit is high.
• It may be difficult to detect when a cow is on heat, especially a singly housed cow. This is because when cows are housed in a group they mount each other and when in the open they show signs of restlessness by moving around.
  

  

  Extensive system

In the extensive system, the cattle are reared on pasture. It is practised where grazing land is available. In East Africa the grazing land mainly comprises natural unimproved grass. In Kenya it is practised in most parts of the Rift Valley, where farmers own large tracts of land.
Advantages

• It is cheaper than the intensive system.
• It is not labour intensive.

Disadvantages

• It requires dedicating much more land to grazing.
• Cows waste a lot of energy by walking while grazing in the field.
• It is difficult to accumulate manure for improving soil fertility in crop fields.

Natural grasses can be improved by oversowing with herbaceous legumes (e.g. Trifolium)
or planting grasses (e.g. Rhodes grass). Oversowing is the method of choice.
Semi-intensive system
In the semi-intensive system, the cattle graze for some time during the day and in the afternoon or evening they are supplemented with other forages like Napier grass. This method is a compromise between intensive and extensive systems, whereby land is not limiting as in the intensive system but on the other hand is not enough to allow free grazing throughout the day.
Due to population pressure leading to subdivision of land, this system tends towards the intensive system.
Other systems
Other methods include ‘roadside grazing’ and ‘tethering’. Roadside grazing involves herding cattle on the roadside where they graze on natural unimproved pastures. It is popular in areas with land shortage. Tethering restricts the cow to a grazing area by tying it with a rope to a peg. This can also be done on the roadside or any other public land. However, in either of these systems the animals may not get enough to satisfy their requirements.

Pasture management
Efficient pasture management results in high yields of good-quality pasture that can be fed to dairy cattle for high milk production. Key activities to be considered include weed control, grazing management and fertility management.
Weed control
Weeds can reduce the productivity of the sown pastures, particularly during the establishment year, and should be controlled during the first year by either hand weeding or using herbicide (2-4D amine at the rate of 2.5 litres per hectare [ha]). In subsequent years fields are kept clean by slashing, hand pulling or mowing the weeds.

Grazing management

The following should be observed:

• In the establishment year grasses reach the early flowering stage 3–4 months after planting. At this stage the plant is not firmly anchored in the soil and therefore it is usually advisable to make hay rather than graze the pastures to avoid the risk of the cattle pulling out the young shoots.
• If the pasture must be grazed during the establishment year, grazing should be light enough (use calves) to allow the plants to establish firmly in the soil.
• For maximum benefit, use the pasture not later than the start of the flowering stage. Graze or cut at intervals of 4 to 6 weeks, leaving stubble at 5 cm height.
• Graze animals when the grass is at the early flowering stage by moving animals from paddock to paddock.
• One animal will need 1–2 acres of improved pasture per year in areas receiving over 900 mm rainfall.
• Conserve excess pasture in the form of hay for dry-season feeding.
  

  Fertility management

To attain maximum production from pasture, the grass requires additional nutrients from inorganic fertilizer or farmyard manure.

• During the establishment year, soil nitrogen is adequate for grass productivity.
• In subsequent seasons, topdress grass with 5–7 bags of calcium ammonium nitrate (CAN) or ammonium sulphate nitrate (ASN) per hectare per year in three splits during the rainy season or 5–10 tonnes of farmyard manure.
• In areas with phosphate deficiencies topdress with 2 bags of single superphosphate (SSP) or 1 bag of triple superphosphate (TSP) per hectare per year after the establishment year. This is in addition to nitrogen fertilizer.
• Nitrogen fertilizer may be applied on 1 or 2 months before the dry season to increase yields during the dry season.

Stocking rates for different grasses

Stocking rate is the number of animals (animal unit) for which a grassland unit (hectare) can provide adequate dry-matter forage for a specified length of time. Stocking rate influences animal performance, pasture recovery, long-term pasture production and long-term pasture species composition.
Stocking rates should represent a balance between grazing pressure (pasture demand) and carrying capacity (pasture supply). The ultimate goal should be to optimize both animal and pasture production over the long term, as opposed to maximizing only one or the other. In general, improved pastures can support higher stocking rates than native
or unimproved pastures. Table 3.1 gives examples of recommended stocking rates for different improved pastures. Yields of commonly used grasses and legumes are in Table 3.2.
Table 3.1. Recommended stocking rates

Grass type	Stocking rate (MLU/acre per year)
Cenchrus ciliaris (blue buffalo grass)	0.4–1.2
Panicum maximum (white buffalo grass)	1.2–2.4
Chloris gayana (Rhodes grass)	1.6
Pennisetum clandestinum (Kikuyu grass)	1.2–3.2

MLU – matured livestock unit, equivalent to 500 kg non-lactating bovine
Table 3.2. Yields of different types of fodder at different agroecological zones (AEZs)

Fodder type	AEZ	Dry matter yield (kg/acre per year)	Mature dairy cow supported (no. days)*
FODDER GRASSES
Napier grass	LH1, LH2	4000–12,000	333–1000
Fodder sorghum (E6518)	LH 3	6800–8800	567–733
Boma Rhodes	LH 3, LH 4	4868	406
Elmba Rhodes	LH 3, LH 4	3944	329
Star grass	LH 3, LH 4	2988	249
Guinea grass	LH 3, LH 4	2564	214
Masaba Rhodes	LH4	4560	380
Guatemala grass	LH4	4080	340
Mbarara Rhodes	UM1	5640	470
Giant setaria	UH2–3	4000	333
Giant panicum	UM4	4720	393
Oat	UM4	2680	223
FODDER LEGUMES
Silverleaf desmodium	LH2	3448
Greenleaf desmodium	LH2	3060
Sesbania sesban	LH4	10880
Leucaena	LH4	5300
Starleafed sweet potato	LH4	3868
Purple-leafed sweet potato	LH4	3116
Broadleafed sweet potato	LH4	2880
Vetch	LH4	1480

LH – lower highland, UH – upper highland, UM – upper midland
* A mature dairy cow weighing about 400 kg consumes about 12 kg dry matter per day

Nutrients are substances obtained from food and used in the body to promote growth, maintenance, reproduction and production. Feedstuffs contain the nutrients animals require to perform normal body functions (such as breathing, pumping blood, fighting diseases, growing, gaining weight, reproducing) and to produce milk. The feedstuff must be digestible and the products (nutrients) absorbed if the feed is to be useful to the animal.
Some components of a feedstuff have no nutritive value because they are indigestible and not absorbable (e.g. some woody plants) and pass out through faeces. In addition, some plants contain compounds that are toxic to the animal.
The essential nutrients are energy, proteins, minerals, vitamins and water.

1.Energy

The energy portion of the feed fuels all body functions, enabling the animal to undertake various activities including milk synthesis. This is the major nutrient (in terms of quantity) that dairy cows require.

Functions

Maintenance: Simply to maintain itself, an animal requires energy. The body weight does not increase or decrease, the animal does not produce; this energy is only for survival and the amount is affected by body size and the environmental temperature.
Growth and weight gain: Gain is especially important for young animals, who need to attain the recommended weight for a particular age.
Reproduction: A cow requires more energy during pregnancy for the foetus to grow and develop normally.
Milk production: The energy requirement of a lactating cow increases with increase in milk production and butter fat content of the milk.

Sources

Energy can be obtained from several types of feedstuffs that contain either carbohydrates or lipids (fats and oils).
Carbohydrates are the major source of energy in the diet of dairy cows. They are found in the staple foods consumed by humans (e.g. rice, maize, wheat, potatoes). Carbohydrates constitute between 50% and 80% of the dry matter in forages and grains.
Feeds contain three major types of carbohydrates:

• Sugars: Sugars are soluble in water, making them readily available to the animal.

Sources are molasses, sugar beets and sugar cane.

• Starch: Starch is the main form of carbohydrate stored in plants. It is the main component of cereal grains and some roots (potato tubers).
• Fibre: Forming the structural part of plants, fibre is present in large quantities in roughages. The fibre is broken down by microorganisms in the rumen (microbial enzymes) into products that the animal can use. It is also important in maintaining high levels of milk fat. Sources include grasses, fodder crops and crop residues.

Lipids (fats) contain about 2.25 times more energy than carbohydrates per unit weight. Generally, plants are good sources of oils while animal products contain fats. Most plant seeds contain a small amount of lipids. The exception is oilseed plants, which may contain as much as 20% lipids (cotton, sunflower and soybean seeds) and are better sources of lipids than animal fats.

Consequences of energy deficiency

The most obvious sign of energy deficiency is poor body condition due to excessive weight loss. Lactating cows are unable to reach peak milk production in early lactation resulting in low lactation yields.

Consequences of excessive amounts of energy

Cows consuming too much energy become too fat, resulting in low conception rates. They are prone to difficult calving, retained placenta, and higher incidence of milk fever and ketosis.
In early lactation, feeding too much energy, especially in the form of grain, may lead to too much acid in the rumen (acidosis), increased risk of displaced abomasum, depressed feed intake and low milk fat percentage.

Special considerations

Usually forages are high in fibre and low in energy, and concentrates are low in fibre and high in energy. Therefore there is need to balance the two, as too much forage limits the intake of energy while too much concentrate results in milk fat depression, rumen acidosis and other health problems.

2. Protein

Protein is quantitatively the second most important nutrient in feeding the dairy cow. Proteins are made up of building blocks referred to as amino acids.

 Functions

Proteins provide the building material for all body cells and tissues (e.g. blood, skin, organs and muscles). Proteins are also major components of products such as milk and meat. Lack of protein therefore adversely affects milk production.

Sources

Good sources of protein for dairy cows include:

• Oilseeds and oilseed cakes: Residues after the oil is removed from oilseeds, e.g. cottonseed meal or cake, whole cottonseed, whole soybeans (cracked) or meal and sunflower meal or cake.
• Products of animal origin: Such as fish meal, blood meal, meat and bone meal, feather meal and by-products from milk processing (e.g. skim milk and whey).
• Herbaceous legumes: Such as lucerne, desmodium and fodder trees (e.g. calliandra and sesbania).
• Non-protein nitrogen: Cows can obtain protein from sources that do not contain true proteins, such as urea and poultry waste (contains uric acid). These sources are referred to as non-protein nitrogen sources. Microorganisms in the rumen use the nitrogen in urea to synthesize protein for their own growth.

Consequences of protein deficiency

For lactating cows, there is a sudden drop in milk production if the amount of protein in the diet is suddenly reduced. Severe deficiency may cause excessive weight loss in lactating cows, reduced growth rate in calves and heifers, and result in underweight calves being born.
Consequences of feeding excess protein
Protein is an expensive nutrient and feeding excess is a waste of money as protein is not stored in the body but is broken down by microorganisms in the rumen and excreted in the form of urea.

Protein and rumen microbes

Most of the protein in feed is broken down by microorganisms in the rumen (rumen- degradable protein) and re-synthesized into bacterial protein. Bypass proteins are proteins resistant to microbial breakdown in the rumen (undegradable protein), and pass intact to the small intestines where they are digested and absorbed directly into the body.

Protein and milk production

Milk contains approximately 3.2–3.5% protein. Thus a cow producing 25 kg milk per day secretes 800–900 g protein daily. Cows have little ability to store protein in the body
and so it must be supplied in the diet daily to maintain the milk yield. Protein should be 15–18% of the total ration of a dairy cow depending on milk yield.

3. Minerals

Minerals are nutrients required in small amounts in the feed. They are required for the body to function properly, i.e. remain healthy, reproduce and produce milk (Table 2.1). Some minerals are required in large quantities in the ration dry matter (macro-minerals) while others are required in small quantities (microminerals). Some minerals are stored in the body (e.g. iron in the liver and calcium in bones) while others are not (e.g. sodium, potassium) and have to be supplied in the diet all the time.
Table 2.1. Minerals required in ruminant diet

Macrominerals	Microminerals
Calcium	Cobalt
Chlorine	Copper
Magnesium	Iodine
Phosphorus	Iron
Potassium	Manganese
Sodium	Molybdenum
Sulphur	Selenium
	Zinc

Functions

Specific minerals may have different functions in the body but the minerals are generally required for

• bone formation
• formation of components of enzymes, vitamins and red blood cells
• production of hormones that control body functions
• control of water balance in the body
• milk synthesis

Requirement for minerals is affected by several factors:

• Age: Mineral requirements for young growing animals are higher.
• Physiological status: Pregnant animals require more.
• Level of production: High-producing cows require large quantities of calcium; deficiency is more likely to occur in early lactation rather than late.
  

  Sources

Although roughages and concentrates contain minerals, the types and amounts vary widely and hence may not meet the requirements. During ration formulation, macro- minerals calcium, phosphorus and magnesium are taken into account. Roughages will supply adequate amounts of potassium and common salt can adequately provide sodium.
Some ingredients (supplements) are added to supply a specific mineral (e.g. limestone, salt, magnesium oxide).
Consequences of mineral deficiency
Signs of mineral deficiency may not be obvious but they include

• poor fertility: lack of heat signs and low conception rate
• low milk production
• poorly developed bones in young animals (rickets)
• health disorders, for example, milk fever
• poor body condition, which may be accompanied by a change in coat colour
  

  4. Vitamins

Vitamins are nutrients in the feed required by the body in tiny amounts for normal functioning of the body, through their involvement in many body processes. Some are synthesized by rumen microbes and/or stored in the body of the animal while others must be supplied in the diet. The vitamins that must be supplied in the diet include A, D and E; those that are produced in the body include B complex, C and K.

Functions

Important functions of vitamins include

• maintenance of healthy protective tissues such as skin, stomach, intestinal and cell linings (vitamin A)
• improvement of appetite, hence feed intake (vitamin B)
• production of red blood cells, hence preventing anaemia (e.g. vitamins B6 and B12)
• enhanced calcium and phosphorus utilization, hence play a role in bone forma- tion and growth (vitamin D)

•enhancing immunity (vitamin E)
help in blood clotting (vitamin K)

Consequences of vitamin deficiency

Vitamin requirements of dairy cows are normally met through diet, rumen microbial synthesis or tissue synthesis. Deficiencies are rare under normal conditions but may occur under certain conditions, shown in Table 2.2.
Table 2.2. Situations in which vitamins may become deficient in dairy cattle

Situation	Affected		vitamins
	A	B	D	E
Feeding poor quality roughage (overgrown), frost- damaged maize silage or long-term stored forage, heat- damaged forage; periods of prolonged drought	X
Very high grain-to-forage ratio	X		X	X
Cattle kept indoors throughout			X
Feeding of milk or milk replacer rations alone	X		X	X
Crop residues as a major component of diet	X		X
Prolonged stress period or disease	X	X	X	X
Very young calves (rumen not functional)		X
Deficiency of cobalt		X

Adapted from Wattiaux MA. 1999. Dairy essentials. Babcock Institute for International Dairy Research and Development, Madison, Wisconsin, USA.
Consequences of feeding excess vitamins
There is no important health consequence of excess vitamins as the body is able to get rid of the excess. However, vitamin supplements are expensive and hence feeding too much is an economic loss to the farmer.
5. Water
Water, though not classified as a nutrient, is essential for life in all animals. Water accounts for 74% of the calf’s weight at birth and 59% of that of a mature cow. Every 100 kg of milk contains up to 87 kg of water.
The amount of water consumed at free will is influenced by several factors:

• moisture content of feed. When the diet has a large proportion of dry feeds,
• e.g. hay and grains, the cow drinks more water than when the diet has a larger proportion of young or succulent feeds, e.g. young grass and legumes
• amount of dry matter consumed
• milk yield
• environmental temperature
• salt intake

An increase in any of the factors above increases the water requirement for lactating cows. The amount of water consumed will also depend on the quality and quantity of water provided (Table 2.3).
Table 2.3. Estimated water requirement by calves, heifers and lactating dairy cattle

Dairy cattle type	Level of milk production (kg milk/day)	Water requirement, average range (litres /day)
Dairy calves (1–4 months)		5–15
Dairy heifers (5–24 months)		15–40
Milking cows	14	65–85
Milking cows	23	85–105
Milking cows	36	115–140
Milking cows	45	130–155
Dry cows		35–50

Adapted from McKague K. 2007. Fact sheet on water requirements of livestock. Ontario Ministry of Agriculture, Food & Rural Affairs, Toronto, Canada.

6. Concept of dry matter

Dry matter is what remains of a feed when all the water has been removed and it contains the nutrients described above (Figure 2.1). This dry matter portion can be divided into organic matter comprising energy, protein and vitamins, and inorganic matter comprising minerals. Animals must consume enough dry matter to obtain the required nutrients to keep them healthy and to let them grow, reproduce and produce milk.
Dry matter is expressed as a percentage of fresh feed; hence a feed comprising 40% dry matter means that for every 100 kg of the feed, only 40 kg is dry matter. It is from the 40 kg that the animal will obtain its nutrient requirements. If the same feed contains 10% crude protein, the amount supplied by the feed will be 10% of 40 kg, which is 4 kg. Banana stem containing 10% dry matter means that if you feed 100 kg of fresh stems, the cow will have only 10 kg dry matter and 90 kg water.

1. Importance of dairy cattle

Dairy cattle make a major contribution to both national and household economies as well as provide milk, which contains essential nutrients. Milk contributes significantly to meeting the human requirements for animal protein and is especially important in the diet of children and the sick.
Regionally, dairy cattle farming contributes to employment on the farm (production), during value addition (processing) and marketing. The farming also supports a large service sector that offers specialized services in nutrition and health.
Increase in human population has resulted in pressure on arable land leading to deterioration of soil fertility and deforestation. Manure from dairy cattle plays a major role in improving soil fertility and it is a source of energy (biogas) for the household.

2. Qualities of a good dairy cow

Though milk production may not be 100% related to the external appearance of a dairy cow, some physical features are related to milk yield and the longevity (length of time animal is productive) of the animal in the herd. These features (Figure 1.1, Table 1.1) are commonly used in judging the goodness of a dairy cow from its external appearance. These characteristics should be considered by dairy farmers while buying, selling or culling dairy animals.

Figure 1.1. Parts of the dairy cow.
Table 1.1. Characteristics used in judging dairy cattle

Physiology	Character	Description	Desired
Size	Size	Stature (height in cm at rump or withers)	Jersey = 120, Guernsey = 125, Ayrshire = 130, Friesian = 135
	Chest width	Distance between the front legs	Should be large to give room for the heart and lungs
	Rump width	Distance between the pin bones	Should be big to ease calving and allow wide rear udder attachment
Dairy character	Angularity Body frame Dairy type	Reflects the appearance that the cow has the will to milk	Rib structure: ribs wide apart, rib bones wide, flat, long and free from excess flesh Neck: long, lean and blending smoothly into shoulders Barrel: width tending to increase towards rear
	Rump angle (pelvic angle)	Angle from hooks to pins	Pins should be slightly lower than hooks (about 2.5 cm). Improper angle can hinder reproductive performance and mobility
	Topline	Level of backbone from shoulders to pelvis	Should be strong and level
Udder	Fore udder attachment	Attachment to trunk	Attachment of fore udder to trunk should be almost level
	Udder depth	Distance between bottom of udder and ground in relation to height	Should be shallow and above the hock. Deep udder is prone to injury. Consider age and stage of lactation
	Rear udder height	Distance between vulva and udder fold	Should be attached high
	Udder suspension	Udder cleft—suspensory ligament	Should be clearly visible and continue upwards. Should be strong to keep udder firm and prevent teats from pointing outwards
	Teat placement	Direction of teats	Should point straight down or slightly inwards (for ease of milking)
	Teat length		5 cm ideal for machine milking; slightly longer for hand milking
Legs and feet	Rear leg set	Angle at hock viewed from side should not be straight	Ideally, pin bone, hock and dew claw should be in one line. Should be straight from the rear
	Hoof diagonal	Distance between point of toe and top of heel	Intermediate desirable

3. Basic needs of a cow for optimum production

The aim of keeping a dairy cow is to obtain the maximum amount of milk. A cow will perform at its best only if its basic needs are met. These include:

• freedom from hunger and thirst (good feed and clean water)
• freedom from pain, injury and diseases (good health)
• freedom from discomfort (comfortable environment, e.g. temperature, clean floor)
• freedom from fear and distress (friendly, loving, gentle and caring handler)

To exploit the cow’s full genetic potential, there is need to have a good nutrition program and meet all other needs.

4. The ruminant digestive system

Ruminants are various cud-chewing hoofed mammals having a stomach divided into four compartments (rumen, reticulum, omasum and abomasum), each one with a specific role to play. The most important is the rumen. Cattle, sheep and goats are ruminants. All ruminants ‘chew the cud’. This means that the food they consumed earlier is returned to the mouth for a second thorough chewing before it is re-swallowed.
The rumen is full of tiny microorganisms (bacteria and protozoa) that digest fibrous feed, such as fresh grass and hay, foodstuffs that humans and most other animals cannot digest. After digesting the fibre, the animal makes use of the end products for growth and milk production. The microorganisms can also convert non-protein nitrogen-containing ingredients (e.g. urea) into protein that the animal can use.
These microorganisms also manufacture some vitamins, such as the vitamin B group.

5. The cow as a milk factory

A dairy cow can be thought of as a milk manufacturing factory. Into any manufacturing factory go raw materials, which are processed, and out of the factory comes a new product. The quality and quantity of the product are a combination of both the quality and the quantity of the raw materials and the efficiency of the factory.
The raw materials that go into milk manufacturing are the nutrients. The quantity and quality of these nutrients depend on the feed consumed by the cow. If the cow is fed on poor-quality feed in large quantities or high-quality feed in small quantities, little milk will be manufactured. The size of the factory can be compared to the size of the cow—where a large factory will hold more raw materials, so will a large cow have a larger rumen.
The machinery that converts raw materials into milk constitutes the digestive system (stomachs and intestines) and the udder (mammary gland). All cows can be assumed to have a similar digestive system but the capacity of the udder will vary depending on the number of milk-making units (alveolar cells), which is determined by the genetics of the cow.
These cells are housed within the cow, which provides a conducive environment for them to function (the cow must be comfortable and free from pain). In a factory, this can be equated to the workers (their number and their comfort).
The factory concept is diagrammatically illustrated in Figure 1.2:
 

Nutrients are substances obtained from food and used in the body to promote growth, maintenance, reproduction and production. Feedstuffs contain the nutrients animals require to perform normal body functions (such as breathing, pumping blood, fighting diseases, growing, gaining weight, reproducing) and to produce milk. The feedstuff must be digestible and the products (nutrients) absorbed if the feed is to be useful to the animal.
Some components of a feedstuff have no nutritive value because they are indigestible and not absorbable (e.g. some woody plants) and pass out through faeces. In addition, some plants contain compounds that are toxic to the animal.
The essential nutrients are energy, proteins, minerals, vitamins and water.

• Energy

 
The energy portion of the feed fuels all body functions, enabling the animal to undertake various activities including milk synthesis. This is the major nutrient (in terms of quantity) that dairy cows require.
 

• Functions

 
Maintenance: Simply to maintain itself, an animal requires energy. The body weight does not increase or decrease, the animal does not produce; this energy is only for survival and the amount is affected by body size and the environmental temperature.
Growth and weight gain: Gain is especially important for young animals, who need to attain the recommended weight for a particular age.
Reproduction: A cow requires more energy during pregnancy for the foetus to grow and develop normally.
Milk production: The energy requirement of a lactating cow increases with increase in milk production and butter fat content of the milk.
 

• Sources

 
Energy can be obtained from several types of feedstuffs that contain either carbohydrates or lipids (fats and oils).
Carbohydrates are the major source of energy in the diet of dairy cows. They are found in the staple foods consumed by humans (e.g. rice, maize, wheat, potatoes). Carbohydrates constitute between 50% and 80% of the dry matter in forages and grains.
 
Feeds contain three major types of carbohydrates:

• Sugars: Sugars are soluble in water, making them readily available to the animal.

Sources are molasses, sugar beets and sugar cane.

• Starch: Starch is the main form of carbohydrate stored in plants. It is the main component of cereal grains and some roots (potato tubers).
• Fibre: Forming the structural part of plants, fibre is present in large quantities in roughages. The fibre is broken down by microorganisms in the rumen (microbial enzymes) into products that the animal can use. It is also important in maintaining high levels of milk fat. Sources include grasses, fodder crops and crop residues.

Lipids (fats) contain about 2.25 times more energy than carbohydrates per unit weight. Generally, plants are good sources of oils while animal products contain fats. Most plant seeds contain a small amount of lipids. The exception is oilseed plants, which may contain as much as 20% lipids (cotton, sunflower and soybean seeds) and are better sources of lipids than animal fats.
 

• Consequences of energy deficiency

 
The most obvious sign of energy deficiency is poor body condition due to excessive weight loss. Lactating cows are unable to reach peak milk production in early lactation resulting in low lactation yields.
 

• Consequences of excessive amounts of energy

 
Cows consuming too much energy become too fat, resulting in low conception rates. They are prone to difficult calving, retained placenta, and higher incidence of milk fever and ketosis.
In early lactation, feeding too much energy, especially in the form of grain, may lead to too much acid in the rumen (acidosis), increased risk of displaced abomasum, depressed feed intake and low milk fat percentage.
 

• Special considerations

 
Usually forages are high in fibre and low in energy, and concentrates are low in fibre and high in energy. Therefore there is need to balance the two, as too much forage limits the intake of energy while too much concentrate results in milk fat depression, rumen acidosis and other health problems.

• Protein

 
Protein is quantitatively the second most important nutrient in feeding the dairy cow. Proteins are made up of building blocks referred to as amino acids.
 

• Functions

 
Proteins provide the building material for all body cells and tissues (e.g. blood, skin, organs and muscles). Proteins are also major components of products such as milk and meat. Lack of protein therefore adversely affects milk production.
 

• Sources

 
Good sources of protein for dairy cows include:

• Oilseeds and oilseed cakes: Residues after the oil is removed from oilseeds, e.g. cottonseed meal or cake, whole cottonseed, whole soybeans (cracked) or meal and sunflower meal or cake.
• Products of animal origin: Such as fish meal, blood meal, meat and bone meal, feather meal and by-products from milk processing (e.g. skim milk and whey).
• Herbaceous legumes: Such as lucerne, desmodium and fodder trees (e.g. calliandra and sesbania).
• Non-protein nitrogen: Cows can obtain protein from sources that do not contain true proteins, such as urea and poultry waste (contains uric acid). These sources are referred to as non-protein nitrogen sources. Microorganisms in the rumen use the nitrogen in urea to synthesize protein for their own growth.

 

• Consequences of protein deficiency

 
For lactating cows, there is a sudden drop in milk production if the amount of protein in the diet is suddenly reduced. Severe deficiency may cause excessive weight loss in lactating cows, reduced growth rate in calves and heifers, and result in underweight calves being born.
 

• Consequences of feeding excess protein

 
Protein is an expensive nutrient and feeding excess is a waste of money as protein is not stored in the body but is broken down by microorganisms in the rumen and excreted in the form of urea.

• Protein and rumen microbes

 
Most of the protein in feed is broken down by microorganisms in the rumen (rumen- degradable protein) and re-synthesized into bacterial protein. Bypass proteins are proteins resistant to microbial breakdown in the rumen (undegradable protein), and pass intact to the small intestines where they are digested and absorbed directly into the body.
 

• Protein and milk production

 
Milk contains approximately 3.2–3.5% protein. Thus a cow producing 25 kg milk per day secretes 800–900 g protein daily. Cows have little ability to store protein in the body
and so it must be supplied in the diet daily to maintain the milk yield. Protein should be 15–18% of the total ration of a dairy cow depending on milk yield.
 

• Minerals

 
Minerals are nutrients required in small amounts in the feed. They are required for the body to function properly, i.e. remain healthy, reproduce and produce milk (Table 2.1). Some minerals are required in large quantities in the ration dry matter (macro-minerals) while others are required in small quantities (microminerals). Some minerals are stored in the body (e.g. iron in the liver and calcium in bones) while others are not (e.g. sodium, potassium) and have to be supplied in the diet all the time.
 
Table 2.1. Minerals required in ruminant diet
 

Macrominerals	Microminerals
Calcium	Cobalt
Chlorine	Copper
Magnesium	Iodine
Phosphorus	Iron
Potassium	Manganese
Sodium	Molybdenum
Sulphur	Selenium
	Zinc

 
 

• Functions

 
Specific minerals may have different functions in the body but the minerals are generally required for

• bone formation
• formation of components of enzymes, vitamins and red blood cells
• production of hormones that control body functions
• control of water balance in the body
• milk synthesis

Requirement for minerals is affected by several factors:

• Age: Mineral requirements for young growing animals are higher.
• Physiological status: Pregnant animals require more.
• Level of production: High-producing cows require large quantities of calcium; deficiency is more likely to occur in early lactation rather than late.

 

• Sources

 
Although roughages and concentrates contain minerals, the types and amounts vary widely and hence may not meet the requirements. During ration formulation, macro- minerals calcium, phosphorus and magnesium are taken into account. Roughages will supply adequate amounts of potassium and common salt can adequately provide sodium.
Some ingredients (supplements) are added to supply a specific mineral (e.g. limestone, salt, magnesium oxide).

• Consequences of mineral deficiency

 
Signs of mineral deficiency may not be obvious but they include

• poor fertility: lack of heat signs and low conception rate
• low milk production
• poorly developed bones in young animals (rickets)
• health disorders, for example, milk fever
• poor body condition, which may be accompanied by a change in coat colour

• Vitamins

 
Vitamins are nutrients in the feed required by the body in tiny amounts for normal functioning of the body, through their involvement in many body processes. Some are synthesized by rumen microbes and/or stored in the body of the animal while others must be supplied in the diet. The vitamins that must be supplied in the diet include A, D and E; those that are produced in the body include B complex, C and K.

• Functions

 
Important functions of vitamins include

• maintenance of healthy protective tissues such as skin, stomach, intestinal and cell linings (vitamin A)
• improvement of appetite, hence feed intake (vitamin B)
• production of red blood cells, hence preventing anaemia (e.g. vitamins B6 and B12)
• enhanced calcium and phosphorus utilization, hence play a role in bone forma- tion and growth (vitamin D)
• enhancing immunity (vitamin E)
• help in blood clotting (vitamin K)

• Consequences of vitamin deficiency

 
Vitamin requirements of dairy cows are normally met through diet, rumen microbial synthesis or tissue synthesis. Deficiencies are rare under normal conditions but may occur under certain conditions, shown in Table 2.2.
Table 2.2. Situations in which vitamins may become deficient in dairy cattle
 

Situation	Affected		vitamins
	A	B	D	E
Feeding poor quality roughage (overgrown), frost- damaged maize silage or long-term stored forage, heat- damaged forage; periods of prolonged drought	X
Very high grain-to-forage ratio	X		X	X
Cattle kept indoors throughout			X
Feeding of milk or milk replacer rations alone	X		X	X
Crop residues as a major component of diet	X		X
Prolonged stress period or disease	X	X	X	X
Very young calves (rumen not functional)		X
Deficiency of cobalt		X

 
Adapted from Wattiaux MA. 1999. Dairy essentials. Babcock Institute for International Dairy Research and Development, Madison, Wisconsin, USA.

• Consequences of feeding excess vitamins

 
There is no important health consequence of excess vitamins as the body is able to get rid of the excess. However, vitamin supplements are expensive and hence feeding too much is an economic loss to the farmer

• Water

Water, though not classified as a nutrient, is essential for life in all animals. Water accounts for 74% of the calf’s weight at birth and 59% of that of a mature cow. Every 100 kg of milk contains up to 87 kg of water.
The amount of water consumed at free will is influenced by several factors:

• moisture content of feed. When the diet has a large proportion of dry feeds,

• e.g. hay and grains, the cow drinks more water than when the diet has a larger proportion of young or succulent feeds, e.g. young grass and legumes
• amount of dry matter consumed
• milk yield
• environmental temperature
• salt intake

An increase in any of the factors above increases the water requirement for lactating cows. The amount of water consumed will also depend on the quality and quantity of water provided (Table 2.3).
Table 2.3. Estimated water requirement by calves, heifers and lactating dairy cattle

Dairy cattle type	Level of milk production (kg milk/day)	Water requirement, average range (litres /day)
Dairy calves (1–4 months)		5–15
Dairy heifers (5–24 months)		15–40
Milking cows	14	65–85
Milking cows	23	85–105
Milking cows	36	115–140
Milking cows	45	130–155
Dry cows		35–50

 
Adapted from McKague K. 2007. Fact sheet on water requirements of livestock. Ontario Ministry of Agriculture, Food & Rural Affairs, Toronto, Canada.

• Concept of dry matter

Dry matter is what remains of a feed when all the water has been removed and it contains the nutrients described above (Figure 2.1). This dry matter portion can be divided into organic matter comprising energy, protein and vitamins, and inorganic matter comprising minerals. Animals must consume enough dry matter to obtain the required nutrients to keep them healthy and to let them grow, reproduce and produce milk.
Dry matter is expressed as a percentage of fresh feed; hence a feed comprising 40% dry matter means that for every 100 kg of the feed, only 40 kg is dry matter. It is from the 40 kg that the animal will obtain its nutrient requirements. If the same feed contains 10% crude protein, the amount supplied by the feed will be 10% of 40 kg, which is 4 kg. Banana stem containing 10% dry matter means that if you feed 100 kg of fresh stems, the cow will have only 10 kg dry matter and 90 kg water.

Figure 2.1. Difference in bulk of feeds before and after water is removed.