The Dairy Farming Handbook Chapter 1: General Introduction to Dairy Farming
Compiled by Dr C.J.C. Muller
The Dairy Farming Handbook Launch
The Dairy Farming Handbook by the Western Cape Department of Agriculture with the support of SAMilco was launched at the 2017 Agri-Expo Livestock. The comprehensive handbook aims to support dairy farmers with problem-focused information based on scientific research. “We trust that this handbook, compiled by experts in their particular fields, will be the roadmap to sustainable milk production for both commercial and smallholder farmers,” said Dr Ilse Trautmann, Chief director of Research and Technology Development Services at the Western Cape Department of Agriculture (WCDA), during the launch. The handbook was compiled by Dr Carel Muller together with a host of expert writers including Marliné Burger, Dr Johan Labuschagne, Piet Lombard, Dr Robin Meeske, Dr Ansie Scholtz, Janke van der Colf, Dr Pieter Swanepoel, Dr Philip Botha, Carinne van Zyl, Dr Alfred Kidd, Rykie Visser and more.
The handbook, comprising of 57 chapters, focuses on dairy cattle nutrition and feeding, housing for dairy cattle, reproduction management in dairy herds, dairy cattle breeding, milk production
and quality and health, and biosecurity.
Introduction
The number of dairy farms in South Africa has, over the past 30 years, decreased, while the number cows in dairy herds has more than doubled. Milking parlours have increased in size and throughput doubled making it easier to milk large numbers of cows on a daily basis. Currently, in rotary parlours with 50 milking clusters, 300 cows per hour can be milked by employing only four to five workers. Together with this, computer programmes are available to collect large numbers of records, such as the milk yield at each milking event, live weight of cows, activity of cows between milking sessions, and the conductivity of milk. All this information can be used to improve the management of dairy cows. However, in spite of all these developments, basic principles in the way cows function and how they are managed, are important aspects of which farmers should always be well aware of.
Components of a dairy herd
Dairy cows are the production units of a dairy herd. Because milk is the main source of income for a dairy farm, herds should consist of mostly lactating cows. Cows have only two production cycles, namely being in milk (lactating) or being dry (non-lactating). At least 82% of all the cows in the herd should be in milk at all times. This proportion increases when cows are longer in milk than the standard 300- day lactation period, while it decreases when cows have long dry periods. When a small proportion of the cows in the herd are in milk, the total milk yield of the herd would be low.
To start a lactation period or milk production cycle, cows must calve down. From this, bull or heifer calves are born. Bull calves are usually culled early in life for veal or beef production, except for breeders raising bull calves to be marketed for natural service or the artificial insemination (AI) industry. Heifers, on the other
hand, are reared to eventually replace culled cows from the herd. Cows are culled for a number of reasons, mostly because of mastitis, or not becoming pregnant, or because of low milk yields, injuries, disease, and death. When
the cull rate of cows is low, fewer heifers have to be raised to maintain the herd size. The extra heifers born in the herd then creates an additional income source for the dairy farm, as heifers can be sold to other farmers suffering
from high cull rates or wanting to expand their herds. The management style in a dairy herd has a major effect on the number of cows that are culled from a dairy farm.
When cows are dry, they should be in the last two months of the reproduction cycle before their next calving down (or due) date. After calving, cows are usually in milk for about 300
days, after which they are dried off to prepare for the next lactation. When it is difficult to get cows to become pregnant, they may be in milk for longer than 300 days. Although cows may be milked for a longer lactation period,
they should be dried off at least 60 days, although not less than 50 days, before the next expected calving date.
Heifer growth rates
Other non-producing animals other than dry cows in a dairy herd include heifers in various age groups. Dairy cows start their lives as a heifer calf after which they grow at breedspecific growth rates, i.e. gaining live weight and increasing body size, to calve down for the first time at about two years of age. Heifer calves, at birth, weigh approximately 6 to 7% of the live weight of the mother. As Jersey cows weigh about 380 to 420 kg, their heifer calves would be about 24 to 28 kg at birth. Holstein cows, on the other hand, weigh about 560 to 620 kg which means that their heifer calves would be about 35 to 41 kg at birth. The live weight gain of Jersey and Holstein heifers should be approximately 0.45 – 0.50 and 0.70 – 0.75 kg per day, respectively. The live weight of dairy cows varies to a great extent as it is affected by their age or the lactation number of cows. For this reason, the growth rates of individual heifers would vary considerably. It is therefore important that heifers are weighed on a regular basis, usually monthly, to record their gain in live weight. Heifers reach sexual maturity at about eight to nine months of age, but they are usually only inseminated for the first time at about 12 to 13 months of age when they have reached minimum target live weights. For Jersey heifers this is about 200 to 215 kg, while it is 300 to 325 kg for Holstein heifers.
The lactation curve
After first calving, a heifer becomes a cow and after that, the age of a cow is indicated by the number of times she had calved down, i.e. a first, second, or third lactation (also referred to as parity) cow. Farmers sometimes refer, incorrectly, to a small, not well grown-out first lactation cow, as a first lactation heifer. The daily milk yield of cows follows a distinct pattern throughout the lactation period. After calving, the daily milk yield of cows increases quickly and reaches a peak at about 6 to 8 weeks after calving. After this, the daily milk yield of cows may be maintained at this high level after which it usually slowly declines at about 0.3 to 0.6% per week with advancing stages of lactation, i.e. increasing number of days in milk. The rate at which milk yield drops after peak is an indication of the persistency of milk production. This trait varies among cows, although it is also affected by the feeding programme. The total amount of milk produced during the lactation is therefore a combined effect of peak milk yield and persistency of milk production after peak.
Sire selection
The genetic merit of cows, together with their feeding level and feeding management, affect the peak production and persistency during the lactation period. Low genetic merit cows will, at the same feeding level, always produce less milk than high genetic merit cows. Dairy farmers should keep in mind that the result of the selection of a sire or a group of sires made today will only be observed fully in five to eight years from now. The current dairy herd therefore consists of decisions on sire selection that were made five to 10 years ago. Current low milk yields of some cows could be attributed to low genetic merit bulls that were used in the past. It is therefore important that bulls with above average breeding values for production traits be used in the dairy herd on an ongoing basis.
Dairy cows are ruminants
Dairy cows, being ruminants, have a unique digestive system and can utilise forages, like hays, silages, pastures and straw, as well as concentrated feeds, such as grains (maize, wheat, barley and oats), and protein sources, like fish meal, cottonseed-oil cake meal, soybean meal. Because cows are ruminants, they can utilise feed not generally used
by people. The ruminant stomach consists of four compartments, i.e. the reticulum, rumen, omasum and abomasum. These four compartments function as a single unit. The rumen makes up about 80% of the ruminant stomach and has a content of about 160 litres. It is in fact a large fermentation vat containing vast amounts of anaerobic (meaning living in the absence of oxygen) bacteria, protozoa, and other organisms that live in symbiosis with the dairy cow. These organisms in the rumen are responsible for the digestion of feeds in the rumen. It is only in the abomasum that enzymes are produced to digest feeds and semidigested material that flows from the reticulorumen.
Cows must ruminate to maintain a healthy rumen. When cows eat, they chew feed into smaller pieces before swallowing it. Long coarse feed particles create a mat in the top part of the rumen with smaller pieces lower down. Because of regular, rhythmic movements of the rumen, the longer feed articles are pushed into the reticulum from where it is regurgitated back into the mouth where this feed is chewed for a second time. Including sufficient amounts of roughage in the total diet, should ensure that cows ruminate for at least eight to nine hours per day. Saliva is produced during this rumination process, also known as chewing the cud, and mixed with the feed. Saliva contains sodium bicarbonate (NaHCO3), which is a natural buffer neutralising the acidity in the rumen fluid. The rumen mat disappears when the diet contains too little roughage or when the roughage component is too finely ground. This slows down the rumination process, resulting in cows producing less natural buffer causing an increase in the acidity levels of the rumen fluid. This is observed as a decrease in the pH-level of rumen fluid. This may result in a metabolic condition known as acidosis. At pH-levels below 5.5, cellulytic digesting microorganisms are killed, resulting in less acetic acid being produced. This results in cows producing milk containing less butterfat. Moreover, when the acidity in the rumen reaches very high levels, the movements of the rumen may stop causing rumenstasis. Continuing high acidity levels may even affect the rumen papillae causing abscesses on the rumen wall. To maintain a healthy rumen, the roughage component of the diet should not be less than 35%. When high levels of concentrates are fed during the early part of the lactation, a buffer should be included in the diet to reduce the acidity in the rumen. Alternatively, high levels of concentrates should be fed in smaller amounts at more regular intervals, i.e. more than twice a day. The amount of concentrate cows receive is dependent on the quality of the roughage
being fed. Higher quality roughages with regards to crude protein and energy content require less concentrates to sustain high milk yield levels.
Feeding of cows
Cows consume a large amount of feed on a daily basis while also drinking large amounts of water, i.e. about 80 to 120 litres, depending on the weather conditions and feed consumed. Cows drink more water when it is hot, while their water intake is less when high moisture feeds are fed.
All feeds contain moisture and dry matter (DM). Even dry feeds, like hay or straw, contain about eight to 10% moisture. Silages and pastures contain about 65% and 85% moisture, respectively. The DM content of feeds contains the crude protein, energy, minerals, and vitamins that cows will utilise to produce milk. The daily feed intake of Jersey cows is about 14 to 16 kg DM, while Holstein cows consume about 24 to 28 kg DM per day. Higher producing cows usually have higher feed intakes. This increase in feed intake is, however, not linear and is actually determined by rumen capacity.
Feed troughs for dairy cows must be large enough to hold the bulky feed that cows are fed on a daily basis. The feed trough width should not exceed 850 mm, unless cows have to feed from both sides. In that case the feed trough should be at least 1.2 m wide. This will ensure sufficient head space for cows to feed from both sides. It is easier for cows to eat from a feed trough when the feed trough floor is about 10 cm higher than the surface they are standing on. A neck rail should be provided at the front of the feed trough to prevent cows from walking through the feed trough and to reduce the head movement of cows while eating. This is especially required when cows have to consume coarse, unmilled low grade roughages like straw. The neck rail of the feed trough should be about 650 – 700 mm above the throat rail. A lower neck rail reduces the head movement of cows, although it may also cause injuries to cows, especially when they have to reach far forward for feed. The forward horizontal pressure on the neck rail is reduced when it is attached about 15 to 20 cm forward above the throat rail. The upright poles that the throat and neck rail are attached to should be spaced in such a way that sufficient feeding space is available for cows. Holstein and Jersey cows require at least 700 – 750 and 550 – 650 mm per cow, respectively. The uprights must therefore be put up with these linear requirements in mind.
Most types of roughages on their own do not contain sufficient feedstuffs to maintain high milk yield levels or growth. For this reason, concentrated feeds, such as grains and protein sources like cottonseed or soy bean meal, should be fed to cows as well. Concentrates could be mixed and fed separately to cows or they can be mixed together with the available roughage in a total mixed ration (TMR). The amount of concentrates that are fed to cows depends on the daily milk yield level and the quality of the available roughage. On good quality grass-clover pasture 4 – 6 kg per cow per day of a 10 – 12% crude protein (CP) content concentrate would be sufficient for Jersey cows, while for Holstein cows 8 – 12 kg per day of a similar concentrate would be required. Cows being fed roughages, like oat hay or wheat straw, would require a considerably higher level and quality of concentrate than for cows on grass pastures. For this reason, diets containing poor quality roughages are generally more expensive requiring higher milk yields to break-even. Cows are usually fed twice a day, preferable after milking. Total mixed rations for dairy cows should be correctly formulated and mixed to prevent digestive upsets.
The production of milk
Cows produce milk on an ongoing basis until the udder is full. They are usually milked twice a day, i.e. early in the morning and late afternoon. When cows are milked more often during the day, milk production is stimulated as the milk is removed and space is available for more milk to be produced. Low producing cows can be milked once a day, especially when the available feed is limited or of a poor quality. The initiation of the milk let-down process is caused by the hormone oxytocin. The release of oxytocin is prevented by the hormone adrenaline that is produced when cows are under stress or given a fright. For this reason, the milking process should always be conducted in a stress-free environment, as cows can lose their milk by being frightened suddenly. Before milking, the teats of cows should be washed with running water and afterwards dried with a paper towel. The first milk from the teat is milked by hand onto a sieve to check for mastitis after which the milking cluster is attached to the teats. Cows showing mastitis should be treated immediately after milking. These cows should be identified and when the problem occurs regularly, the reason for this should be identified. Mastitis has a major financial implication as contaminated milk has to be discarded after treatment. Sub-clinical mastitis also has a large negative impact on the milk yield of cows, while reducing the quality of milk in the bulk tank.
Milking of the cow
In closing
The feeding of cows can be simple, although for profitable milk production, diets should be correctly formulated, mixed and fed. In this manual, some basic information on principles and practices of dairy farming is provided to improve the knowledge and skills of existing and new dairy farmers. The same principles apply whether 30 or 3000 cows are being milked on a dairy farm. Dairy farmers should have some basic knowledge of the way the rumen of cows function. They must be aware of the impact of the environment, genetic merit, and management principles on the production performance of dairy cows. It is important that dairy farmers continually seek new information to apply to their existing operations. Worldwide research is ongoing towards improving feeding programmes, estimating genetic merit of dairy cows and bulls, while facilities are being improved to reduce the every-day labour inputs in order to simultaneously improve the welfare of animals and workers.
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