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The hair on her back, the pelvic area and the tail head is ruffled and sometimes bare.
? The lips of the vulva are coloured red and somewhat swollen.
? Discharge of clear thin mucus from the vulva, which may be attached to the tail.
? Often, milk production is less than normal and the cow behaves differently.
? After heat there may be a bit of bloody mucus discharge on the hindquarters and the tail.
A: Early heat, sniffing at other cows B: Full heat, stand to be mounted C: After heat, still sniffing at other cows Heifers after puberty and non-pregnant cows should come in heat every 3 weeks or 18 to 23 days. So when records are kept of heats detected it is easier to keep an eye on the animal 18 to 23 days later to see if it comes in heat again. If she was inseminated and does not come in heat, it may be assumed that she is pregnant.
Heat detection procedures Normal heat lasts about 8 to 12 hours. It is therefore advisable to observe cows at least three times a day for some 10 to 20 minutes for signs of heat. A bull will never fail to detect a cow in heat, but mostly bulls are kept apart from the cows, so the farmer has to recognise the heat signs. When cows are grazing in a herd recognising an animal in heat is not difficult, as other cows will mount her. It will be less easy 46 Dairy cattle husbandry to detect if cows are housed, but if the animals can walk around, they can still mount one another. Most difficult is when cows are tied in a stable. Then the farmer must be more watchful to detect other signs like restlessness, bellowing and a drop in milk production and check whether the vulva is swollen and red.
Complications in heat detection Under conditions with high ambient temperatures, cows often show signs of heat during the cooler hours of the day, especially at night. In hot climates, heat is of a shorter duration, 6 to 8 hours, making detection more difficult. Frequent observations, particularly during early morning and late evening will help.
Cows that are not healthy will not come in heat or will not exhibit clear heat signs. The same applies to cows in a poor condition or loosing body weight because of inadequate feeding, high milk production in the period after calving, or disease.
6.2 Breeding Once the animal has been identified as being in heat she may be taken to the bull for service or to be inseminated. If there is a bull among the cows he will take care of the service, but the farmer should record this to establish the dates for drying off and the next calving.
If an artificial insemination (A.I.) programme is available, you may wish to make use of this service for your cows in heat. Be aware that insemination should take place during the second half of the heat, preferably between 6 to 12 hrs after the first heat signs. For natural service, the animal in heat should be presented to the bull during standing heat. As a general rule, cows detected in heat in the morning should be serviced that same afternoon and those that came in heat in the afternoon should be serviced early next morning.
If a cow has to wait for A.I. service, she should preferably be kept in the shade and given water to avoid an increase in body temperature.
Reproduction Care should be taken to avoid (heat) stress as this reduces the conception rate. To obtain genetic improvement, it is important to carefully select the proper bull or semen. In high potential areas under good management conditions, crossbreeding the local cattle with a dairy bull may be considered. In the hot tropics, crossbreeding with milking zebu breeds like the Sahiwal and Red Sindhi is an option. The choice of bull should be made with care, also within the breeds, taking into account the desired cow to be bred and the specific conditions on the farm. Seeking advice from local specialists is most advisable.
Cows can be served from the second heat after calving onwards, thus after some 45 to 50 days. The first heat is the last part of recovery of the uterus after calving; chances of conception are low at this point in time. If after a service the cow comes back in heat some 3 weeks later, she has obviously not conceived and needs another service
6.3 Calving Interval The calving interval is the period between a cow’s two consecutive calvings. The ideal calving interval is one year (12 months). This period can be divided into the open period, which is the period between calving and conception, and the pregnancy period. As the length of the pregnancy is fixed at 9 months, the calving interval depends entirely on the open period.
The open period should be about 3 months, indicating that a healthy cow coming in heat 50 days after calving should be served then. The open period on many farms is much longer because cows do not come in heat, heat is not detected or the servicing is not successful. The result is a prolonged calving interval, often 15 months or even more.
The shorter the calving interval, the higher the lifetime production of the animal. In any case, calving intervals shorter than 15 months or 450 days should be aimed for. This coincides with a calving percentage of 80 % or higher.
Traditionally, the calving % is expressed as a part of a full year or 365 days. A 100 % calving result means that all cows do calf at a year’s interval on average. A calving % of 80 implies a calving interval of (365:80) x 100 = 456 days (about 15 months). An average calving interval of 425 days gives a calving percentage of 365 x 100/425 = 86 % Dry period Ideally, lactation lasts for 305 days. Combined with the 60-day dry period, this provides an ideal calving interval of one year. Many people believe that a new pregnancy will negatively affect the daily production of the cow. This is not the case until about the 6th month of pregnancy.
The shorter the calving interval the more lactations the cow will have in her lifetime. Moreover, if a cow has a longer dry period she may become too fat. This will have a negative carry-over effect on the next lactation, so she will produce less milk. Best is a short calving interval and a standard dry period of 2 months. Moreover a cow producing milk, even a small amount, is more efficient in her feed intake and digestion than a dry cow. Therefore, continue milking her right up to 2 months before calving. This benefits both animal and farmer.
Reproduction If a cow lives for 6 years after first calving, variations in calving interval will have big consequences for her lifetime production. Meanwhile feed requirements of such cows and other costs vary very little. This shows that calving interval and lactation length are of the utmost importance for the profitability of dairy animals. See table 10.
Table 10: Cows living 6 productive years after first calving and an average yield of 2000kg/lactation
Lactation A normal lactation curve of a healthy well-fed cow reaches its peak at about 6 to 8 weeks after calving. Thereafter, milk yield per day levels off and slowly declines until drying off at 60 days before the expected next calving.
It often happens that a lactation curve follows the normal pattern towards the peak, but then milk production sharply declines and after some time rises a bit again (see Figure 15). This is mainly due to inadequate feeding. During peak production, the cow has exhausted her feed and body reserves, gets very thin and her milk production decreases. Once recovered from this feed deficiency, she will again increase production somewhat but far below her capacity, consequently a lot of potential milk is lost. It takes much longer before such a cow conceives again, so she will have a very long calving interval. Therefore it is very important to provide good roughage and liberal amounts of concentrates to cows in early lactation. This will prevent the sharp decline in milk production after peak yield.
50 Dairy cattle husbandry Figure 15: Lactation curves: A = potential lactation, B = lactation of a cow inadequately fed during early lactation.
6.4 Young Animals Heifers may reach puberty at a very young age of around 12 to 15 months. However, they should have attained at least 70% of their mature weight at the moment of first service. For well-reared heifers this is at an age of around 20 months. Under very intensive conditions this can be achieved at an age of 15 months. On the other hand, when heifers are older than 20 months their live weight at service should be much more because their growth after calving will be much less.
A pregnancy of underdeveloped heifers will hamper their future milk production, so an age of two and a half years at first calving is best on many small farms. As an indication, a Holstein heifer should weigh some 350 kg, a crossbred around 300 and a light breed some 250 kg at the moment of serving at the age of 20 months.
6.5 Partial suckling Cows that are (partly) suckled by their calves generally do not come in heat during that period. So suckling might increase the calving interval. By restricting suckling, for example, to 15 minutes and only twice
6.6 Bulls Young bulls can be used for controlled mating from the age of 1 to 1.5 years onwards. If mated cows come back in heat frequently, the bull might have a fertility problem. Care should be taken to avoid the spread of contagious diseases, like trichomoniasis, vibriosis and abortion (Brucellosis). Cows for service should be healthy, have calved normally and show no discharge from the vulva. If in doubt contact the veterinarian.
The calf of today is the dairy cow of tomorrow.
The newborn female calf should become a milk-producing cow in about 2.5 year’s time. However, calves may die and this mortality means a loss of money. Far worse is morbidity, the chronic disease status of calves resulting in stunted animals. Morbidity affects all aspects of the animal during its entire life: its growth, the age of first calving, milk production and calving interval.
Proper young stock rearing preventing mortality and morbidity is extremely important for the economic situation of the farm. This starts with the care of the cow around calving. The next step is to help the calf – a monogastric animal at birth – to become a ruminant. A ruminant has four functioning stomachs, while in the recently born calf only the real one, the abomasum, is developed. The other three stomachs, especially the rumen, develop when the young animal eats roughage. This process takes about 8 to 10 months.
7.1 Calving A pregnant cow will give birth to her calf 9 months after the last successful service. The unborn calf grows fast in the last two months and the milk producing tissues in the udder are renewed. It is why the cow has to be dried off 2 months before the expected calving date.
The cow should be observed regularly a few days before calving and, if possible, be separated from the herd, preferably in a clean, roofed place with dry bedding and without obstacles that might cause injury.
At the start of delivery the animal becomes restless, lies down and stands up again, and attempts to urinate. The uterus starts contracting which is not yet visible. The appearance of the water bladder is the first real sign. In a normal delivery the calf’s front legs and mouth appear first. Once the head is born the rest of the body will follow, only the hipbones may cause some delay. If it takes too long, pull on the front legs, but only when the cow herself is pushing.
It is best to keep an eye on the cow but let her do the job. If assistance at calving is really unavoidable, make sure that your hands are washed and clean and wash the vulva of the cow before starting. In case of doubt or lack of experience, call the vet or an experienced person.
The afterbirth or placenta should be expelled within 3 to 4 hours. If this does not happen within 12 hours, call for expert help. Do not pull or put a weight on the afterbirth, this may damage the cow’s uterus 54 Dairy cattle husbandry and cause serious problems. Allowing the calf to suckle directly after birth stimulates the expulsion of the placenta. See Chapter 5.9.
7.2 Calf rearing A newborn calf needs milk for about 3 to 4 months. After weaning, the calf can do without milk but it still needs high quality feed to stimulate its growth and development. The period after weaning is often the most difficult, especially if high quality feed is not available or is considered too expensive. Calf mortality, however, is highest during the first 3 to 4 months.
The first days Right after birth the umbilical cord should be disinfected with a solution of iodine. A newborn calf does not have any resistance against diseases or parasites, so it needs good care, proper housing and adequate nutrition to prevent it from becoming ill. Newborn calves should be housed in an individual calf pen. Assure a dry floor with bedding or a slatted floor and no draught of cold air. After 3 weeks, calves can be housed in a group.
The newborn calf needs colostrum as soon and as much as possible, preferably within half an hour but at least within 2 hours after birth.
‘Colostrum’ is the milk the dam produces during the first 3 days after calving. Colostrum contains a lot of antibodies and it gives the calf socalled ‘maternal immunity’. Some farmers allow the calf to stay with its dam for 2 or 3 days to get the maximum amount of colostrum. The problem is that it may be difficult to teach the calf to drink from a bucket thereafter. Other farmers milk the cow 3 to 5 times a day and feed the colostrum immediately to the calf, about 0.75 to 1 kg each time. This is important for building up immunity as soon as possible.
Maternal immunity lasts for some 2 to 3 months and within this period the calf has to build up its own immunity. Best is to allow the calf some exposure to pathogenic organisms and parasites. Caution: make sure it is only a light exposure!
Calf and young stock rearingFigure 17: Individual calf pen