The management practices in a herd of dairy cows can be split into 4 periods. After first calving, a dairy cow at any one time will be in the following periods:
- Reproductive: Service period (calving to conception) or Gestation period (conception to calving) = Calving Interval
- Productive: Lactation period (calving to drying) or Dry period (from drying to next calving) = Calving Interval
Some management practices are period specific while some are performed during all the periods. There is an overlap in some of the periods: a lactating cow can be pregnant or not pregnant and a pregnant animal can be lactating or dry.
The different periods of the dairy cow cycle.
Service period: From calving to successful conception
This period is expected to last between 45 and 90days. During this period, the cow is expected to come and heat and be bred. The main management practices are therefore heat detection and successful mating (natural or artificial).
This is an extremely important exercise as a missed heat translates into a wasted 21 days while efficient heat detection makes it possible to serve the animal at the right time. The average heat interval is 21 days with a range of 18 to 24 days. Duration of heat is 24 to 36 hours in exotic and crossbred cows.
Several methods are used to detect heat. The most commonly used by farmers are behavioral signs and physical changes.
• Mounting other cows
• Swollen vulva
• Licking other cows
• Sniffing other cows and being sniffed
• Reduced feed intake•
Early signs: Watch the cow closely
• Standing to be mounted
• Clear mucus discharge
• Sharp decline in milk production
• Tail bent away from the vulva
• The animal may stop eating
Best signs: Take the cow
• Dried mucus on the tail
• The animal refuses to be mounted
• Streaks of saliva or signs of leaking on her flanks
Late signs: Keep record
Behavioral signs of heat in cows.
(a) Standing to be mounted: The (b) Licking: Both cows may be in heat positive sign of heat is standing to be mounted.
The cow in heat stands to
be mounted and does not move away
(c) Mounting head to head: The cow mounting is in heat
Aids to oestrus detection:
- Vasectomised or teaser bulls – These are surgically prepared bulls which are intact but will not impregnate the cow (teaser bulls have their penis deviated such that they will mount but cannot deposit semen in the cow). Animal with nutritional deficiencies (e.g. Calcium and Phosphorous mainly during the dry season) may exhibit silent heat (no behavioral signs), which can be detected by vasectomised bulls.
- Records – can be used to predict date of expected heat.
- Pressure sensitive (commercially available) mount detectors. They are glued to the rump (back) of the cow suspected to be on heat and are activated by pressure of mounting of the cow by others.
- Detection of ovarian changes: Use commercial kits to detect fall in progesterone levels in milk.
Note: Heat should be checked three times a day.
Numerous studies indicate poor oestrus (heat) detection is the most common cause of prolonged inter-calving intervals in dairy cattle so herd managers must insure that animal attendants responsible for this are competent. An oestrus detection efficiency of 75 % would represent outstanding performance, a standard achieved in very few herds. Even 60 % efficiency would be somewhat above average with perhaps a 45 % detection rate representing about the average for commercial dairy farms.
Many herds, however, realize only 20 to 30 % efficiency, a rate that results in far too many days open. This poor detection efficiency results in greatly prolonged inter calving intervals and high involuntary culling for reproductive failure. Unfortunately, this latter situation is encountered on many dairy farms all over the world.
Once heat has been detected, cows should be mated.
When to serve:
Present the cow for insemination at the right time to increase the chances of conception. Below is a guide as to the best time to present the cow for insemination
AM – PM Rule:
Standing heat observed Present for insemination
Before 9 am Late afternoon or evening
Late evening the same day Early next morning
EARLY HEAT STANDING HEAT LATE HEAT
0 hrs 27hrs 3 hrs 6 hrs 21 hrs 24hrs
Poor poor Fair Good Excellent Good Fair
First observation of standing heat
How to improve breeding performance
- Serve cows 50 to 75 days after calving.
- After insemination, check 19 to 21 days later for any heat signs.
- Carry out pregnancy diagnosis six to eight weeks after the last insemination.
- Maintain good nutrition with balanced rations and adequate mineral supplementation for good fertility.
Breeding can be achieved through natural service or artificial insemination, and irrespective of the method, the aim should be to achieve increased chances of conception.
This is where the cow is taken to a bull and left for some time for the bull to serve.
The advantages of this method are:
- The cow has an opportunity to be served more than once; this increase the chance of conception.
- The semen is fresh and of good quality since there is no handling.
- Where the farmer does not own a bull, cost of service is lower compared to A.I.
Natural service has the following disadvantages:
- Rearing a bull is not economical especially to a small holder farmer
- There is risk of spreading breeding diseases.
- There is risk of inbreeding if the bull is not changed frequently
- There is no opportunity to select the type of bull the farmer wants.
- Increasing the chances of conception through natural service:
- Take the cow to the bull as soon as it is detected to be in heat and leave it for at least twelve hours.
- Young inexperienced heifers should be mated with old experienced bulls.
- Young inexperienced bulls should be given to old experienced cows.
- The bull should be kept fit and in good health particularly the legs and feet.
Natural mating can be done in two ways:
- Free/pasture mating – This method of mating is practiced by farmers who own bulls which run full time with the cows. One bull can serve 20-25 cows.
It has the advantage no no heat detection required and disadvantage of lack of accurate records and possibility of transmission of reproductive diseases e.g. brucellosis.
- Hand mating- The bull is enclosed in its pen and the cows are brought in when they show signs of heat. Most small-scale farmers will practice this method since bulls are owned by few farmers and others bring their cows for service at an agreed fee.
The advantage is keeping accurate records while the disadvantage is the farmer has to detect heat.
Artificial Insemination popularly referred to as AI is one of the breeding methods that has contributed to the development of the dairy sector in the last sixty years in East Africa and also worldwide. The process of artificial insemination starts with a healthy bull, that is disease free and producing ample quantities of high quality semen. The fertility of the cow is also important, the competency of the inseminator and a clean environment. Farmers are encouraged to use semen from proven bulls which is obtained from AI centers and registered service providers.
Benefits of Artificial Insemination
- Prevention of venereal diseases
- Indefinite preservation of genetic materials of low cost enabling wide testing and selection of bulls
- Enhances genetic progress as best bulls are used widely nationally and internationally
- Small scale farmers through AI can access good bulls cheaply
- One is able to select the bull of interest.
- When handled properly, there is no chance of spread of breeding diseases.
- It is easy to control inbreeding.
- A.I. is the best method of improving the genetic make-up of local breeds because it enables semen from the very best bulls to be widely available.
- It is cost effective since the farmer does not have to rear a bull.
Disadvantages of AI
- It requires very accurate heat detection and proper timing of insemination for greater chances of conception.
- The inseminator must be trained on the technique.
- It requires high investment in equipment.
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Factors affecting rate of conception:
The fertility chain
Successful conception is dependent on several factors, which form a fertility chain.
The concept of the chain is that it is only as strong as the weakest link. Therefore all the links in the chain should be strong enough to strengthen the whole chain, as one weak link results in no conception.
The fertility chain
Heat detection and time of service
This depends on whether natural service or artificial insemination is used. A cow in ‘standing heat’ stands for mounting by bull or another cow.
In practice, a cow showing heat in the morning should be inseminated in the afternoon, while those showing heat in the evening should be inseminated the next morning.
Semen quality and handling
To maintain a good dairy herd, the farmer must use semen of proven bulls all the time. The semen must be obtained from agents or service providers registered by the veterinary department.
Hours from beginning of standing heat
AI can spread disease if attention is not paid to the health status of the bull. All bulls at approved AI centers are constantly being screened for any disease to ensure that semen collected from them is safe and disease free.
The spermatozoa should be fertile, of good concentration, high motility and of normal morphology (structure).
Farmers should only use registered inseminators who are competent and know how to handle semen and apply proper AI techniques. Handling semen involves retrieving semen from the tank without damaging what remains in the tank, thawing and loading an AI gun and successfully inseminating the cow with semen that is still alive and viable.
Nutrition is the single most important factor that affects cow fertility than any other factor. Low protein and low energy intake causes delayed puberty, silent heat and infertile ovary. Vitamin A and D are heavily involved in reproduction and their deficiency affects conception and pregnancy. Overfeeding results in fatty ovaries, low hormonal secretion hence low conception rate.
Note that today’s fertility is a reflection of the cow’s environment and management during the previous two or three months. Also decisions made today can affect a cow’s fertility for several months to come.
Normal health of female genital tract.
The cow should be maintained in good health condition. Any disease of the female reproductive tract affects conception rate. The uterus should be treated before insemination if it is suspected to be diseased.
Indicators of infertility
Fertility problems are manifested through the very long calving intervals as a result of a prolonged service period. Some of the conditions that may indicate a fertility problem include:
- Abnormal oestrus: Absence of heat, irregular heat, silent heat, constant heat (nymphomania)
- Embryonic or foetal death: Abortions, mummified foetus (foetus dying in uterus and becoming mummified)
- Outbreak of reproductive diseases e.g. brucellosis or trichomoniasis
To gauge whether the farm is successful in fertility management of the herd, the following indices can be used.
- a) Calving interval:
An efficient breeding program influences the productivity of a cow in that it determines the number of calves born and the total milk produced throughout its lifetime. A good indicator of successful breeding is a calving interval of one year.
- b) Conception rate (number of animals conceiving as percent of number served)
70% after 1st service
80% after 2nd service
>90% after 3rd service
Animals not conceiving after 3 inseminations should be culled if all the factors in the fertility chain have been considered.
- c) Desired herd composition
Cows in milk 45%
Dry cows 9%
Pregnant heifers 8%
Heifers (weaning to first service) 14%
Heifers (birth to weaning) 24%
Sometimes for ease of management, it is desirable for a group of animals to calve at the same time necessitating that animals come on heat at the same time. To achieve this, the animals are synchronized/ using hormones.
Synchronization is dependent on manipulation of hormonal events occurring during normal oestrous cycle. It is achieved via premature leuteolysis using prostaglandins
(PG) or simulation of corpus leuteum (CL) functions by administering progesterone followed by abrupt withdrawal.
This is a process through which an embryo is harvested from one cow and transferred to another cow to complete the pregnancy.
The process involves super-ovulation of the donor genetically superior cow (cow injected with hormone to stimulate development of many eggs), insemination of cow with high quality semen, synchronization of oestrous cycle of donor and recipient cows, flushing out the embryos from donor cow and transfer of embryo to recipient cow.
Gestation period (from successful conception to calving (280 ±10days))
During early pregnancy the fetal growth is slow and accelerates towards the end.
Regeneration of mammary glands occurs towards the end of gestation in preparation of lactation.
During the first two months of gestation, growth of embryo is minimal but during the last three months there is marked growth of foetus which is dependent on nutritional level of dam, breed of animal and health of dam.
Therefore, during the last few weeks of pregnancy, cows should be fed enough to cater for the rapid growth of foetus and build up body reserves in readiness for the next lactation. This feeding is referred to as ‘steaming’ and coincides with the dry period (refer to feeding during dry period).
Lactation period: (calving to when the cow is dried: 305 days)
This period is variable due to variation in the service period but should be approximately 305days. Milk production peaks at around the 8th week depending on the feeding regime. Cows that are not well fed do not peak.
Management during this period should aim at getting as much milk from the cow as she can produce and as hygienically as possible for human consumption.
Factors affecting milk production
Milk production is not constant but varies from farm to farm and animal to animal. This variation allows for the manipulation to improve milk yield.
- Breed – Capacity for milk production decreases as follows – Friesian, Ayrshire, Guernsey, Jersey, Sahiwal, Boran and Zebu. This is attributable to the genetic makeup of the animal.
- Parity (age)- Mature cows (>6 yrs) produce 25% more milk than young cows. First lactation yields 25% less than 4th lactation. After peak yield there is a decline, as cow grows old. As milk yield increases with age, the herd should have both young animals (for genetic improvement) and old cows for higher milk production
- Stage of lactation- Milk production increases during the first two months following calving (peak production), then declines gradually thereafter.
- Oestrus -Milk production drops the day the cow is on heat or day following heat.
- Pregnancy- By the 4th to 5th month of pregnancy, total milk production of gestating cows declines faster than that of non- pregnant cows.
- Size- Bigger cows will produce more milk than smaller cows of similar breed.
- Feed – Nutrition is the most important determinant and a deficiency of nutrients, especially protein or energy will lower milk yield.
- Length of dry period – A short dry period (<60d) usually results in lower milk production.
- Conditions of cow at calving – Excessively thin or fat cows produce less milk.
- Frequency of milking – Cows milked 3 times produce 10-25% more milk than those milked twice. Cows milked 4 times produced 5-15% more milk than those milked thrice. Though there is increased milk yield with more than twice a day milking, there is extra labour and materials which has to be considered.
More than twice a day milking is only recommended if economical (the extra milk pays for the extra cost of milking), for high yielding cows and for mastitis cases.
- Farm layout – The relationship of watering points, pasture paddocks and the milking parlour is important. Animals walking long distances will utilize a lot of energy, which should go to milk synthesis.
- Disease- Diseases like mastitis, ketosis, milk fever and others affect milk production.
- Change of milker and milking routine will lower milk yield.
- Climate -high temperatures reduce milk yield more drastically than low temperatures (affect animal comfort and feed intake). Exotic breeds are affected more affected by temperature than local breeds.
Dry period (drying to calving: 60days)
The dry period should last for about 60 days irrespective of whether the cow is still producing a lot of milk. Attempts should be made to minimize stress to the cow during the drying especially for high yielders.
Ways of drying cows:
- The feed intake should be reduced to maintenance level by withdrawing the concentrate and for high yielder, feed on low quality forages (eg straw) to reduce milk synthesis.
- For low yielding cows, just stop milking. Pressure builds up in udder and milk production is cut off.
- If cow is a high yielder, practice intermittent milking i.e. skip some milking times (milk only in mornings) so as to reduce milk synthesis due to pressure build up in udder while reducing feed intake.
- Water can be temporarily withdrawn for very high yielders to reduce milk synthesis.
- After cessation of milking, treat (infuse) all the quarters with long acting antibiotics to prevent development of mastitis.
Reasons of drying
There are several reasons that necessitate the drying of the cow:
- Build up body reserves to meet next production – if a cow is not dried in time, it affects the milk production during the next lactation.
- Allow animal to regenerate alveolar tissue (milk synthesizing tissue) which might have atrophied during the lactation period.
- Save nutrients for the fast growing foetus. During the last phase of pregnancy, the calf grows at a fast rate and drying saves nutrients for its growth.
Steaming up of the cows is commencement to feeding extra ration, especially of concentrates, to late pregnant cows in an attempt to promote maximum milk production from the very beginning of the next lactation.
Some of the advantages of steaming up is provision of the extra nutrient required for the accelerated fetal growth, under regeneration and for cow to improve its body condition.
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