By-Ajeet Sharan, TVO, Gomo, Dhanbad.
Introduction
Dry cow therapy (DCT) is the treatment of cows at the end of lactation with a long acting antibiotic preparation with or without a teat sealant. This is to treat for any intra-mammary infections (IMI) contracted during lactation and provides protection against new infections during the dry period.
Why a dry period for cows and management tips
The mammary gland of the dairy cow requires a non-lactating (dry) period prior to an impending parturition to optimize milk production in the subsequent lactation. This period is called the dry period, and it includes the time between halting of milk removal (milk stasis) and the subsequent calving. Generally, 50 to 60 days is recommended. If the dry period is less than 40 days, then the milk yield in the next lactation is likely to decrease.
The dry period is necessary to allow the mammary gland to go through a normal period of involution and to ensure that the mammary cell numbers continue to proliferate normally during early lactation. A short or absent dry period greatly reduces the number of secretory cells in the mammary gland.
The amount of milk produced during a cow’s lactation can be influenced by the length of her dry period. Many studies have shown that cows dry for 60 days give approximately 113 kg more milk the following lactation, compared to cows dry fewer than 40 days, which produce around 225 kg less milk the following lactation. Dry periods longer than 60 days show only a moderate decline in milk production compared to those cows dry 60 days. The reason for keeping dry periods close to 60 days short dry periods do not allow enough time for mammary gland involution while long dry period results in excess body condition.
In field conditions, the dry period of the cow represents one of the most neglected. The early dry period and the close up dry period are times of increased susceptibility to new infections.
During the dry period, the risk of new infection by contagious mastitis pathogens is greatest during the first two weeks. Teat end exposure to environmental pathogens is constant throughout the dry period. 50 – 60% of all new infections during lactation are caused by environmental pathogen exposure during the dry period. Over 50% of clinical coliform mastitis cases occur within the first 70 days of freshening as a result of dry period infection (20% within first week).
As the milk demand is increasing, it has put immense pressure on the dairy farming practices and demands on early lactation cows. The stressful period can have a negative effect on a cow’s health, feed intake, and milk production.
Dairy cows are at a vulnerable state when they’re between lactations. This is why a rest period is required in between, primarily because they will be more prone to nutritional issues at this time. The rest period is an important process in a cow’s lactations because this helps to prevent health problems that may give serious problems to the cow’s milk production and future lactations.
It is important to go through the proper drying-off procedure to prevent the emergence of diseases and infections such as mastitis and intra-mammary infections. It is generally recommended to first withdraw concentrates from the cow’s ration for one to two weeks, and then afterwards to gradually stop milking.
As drying-off goes, when the cow isn’t milked for 18 hours or more, the milk glands will stop producing droplets of milk. This will reduce the size of the udder and will start the cow’s dry period of 60 days. Be reminded that during this period the cow should be placed in clean and dry pens and is separated from the lactating cows.
During the dairy cow’s dry period, we should take care to check for diseases and infections that the cows may develop. Three important things to check would be mastitis prevention, vitamin supplementation, and the cow’s body condition. (blog dated April 21, 2010).
Management factors can help alleviate some of the stress at this time , however, it takes a strong dry period program to make a successful and profitable transition from a dry to lactating cow. Management of the fresh cow also begins during the dry period. It is important to feed dry cows a balanced ration (including vitamins and minerals) and they should not lose body condition during this time. Losing body condition during the dry period can lead to metabolic disorders, such as fatty liver and ketosis, which can reduce milk production in the next lactation.
Vitamin supplementation is probably most vital for cows in late pregnancy, as it needs large amounts of vitamins, particularly vitamins A, D, E and selenium. Vitamin A helps in preventing premature and stillborn calves and retained placenta, while vitamin E and selenium helps to enhance the body’s defenses from infectious agents. A balanced vitamin supplemented diet is needed during the cow’s dry period.
Pregnancy and lactation, reproduction and milk production, takes a considerable toll on the cows. They also have a reduced dry matter intake for the first two months of lactation. This is why the cows must have stored body fat as a source of reserve energy, especially during this period.
Lactating cows usually use about 1 kg of stored fat each day to produce 7 kg of milk. If the cow uses up more than 1 kg, especially in the first 14 days of lactation, ketosis may occur because of the fat that is accumulating in the liver. The interval to the conception will be longer than normal in this case.
The normal procedure to dry off a cow is to withdraw all grain (concentrate) and reduce the water supply two weeks prior to the start of the dry period. This drastically reduces the milk production during that time. Then milking is halted abruptly about 45 to 50 days before expected date of parturition. Intermittent milking along with a decrease in the energy concentration of the ration can be used as a method to achieve the target yield. Cows should be observed closely for the first two weeks after drying off to ensure that udders are involuting properly. Udders with swollen quarters should be examined for mastitis.
Infusion of the udder with antibiotics can help prevent infections that may occur in early involution. After milking is stopped intra-mammary pressure increases, milk products accumulate in the gland, and further milk secretion is inhibited.
Infusion Procedures:
The teats must be cleaned and sanitized carefully before any infusion. Without proper preparation, organisms present on the teat end may be forced into the udder and result in a severe infection especially if Gram-negative bacteria are introduced.
a. Clean and dry teats.
b. Dip teats in an effective germicidal product. Allow 30 seconds contact time before wiping teats with an individual disposable towel.
c. Thoroughly clean and disinfect each teat end, paying particular care to the teat orifice, by scrubbing with a cotton swab soaked in 70% alcohol. Use a separate piece of cotton for each teat.
d. Prepare teats on the far side of the udder first, followed by teats on the near side. (Teats may be cleaned and infused individually, if necessary.)
e. Treat quarters in reverse order; near side first, far side last.
f. Insert only the tip of the cannula into the teat end and express all of the contents. Do not allow the sterile cannula to touch anything prior to infusion.
g. Do not massage the teats to disperse the product.
h. Dip teats in an effective germicidal product after treatment.
i. Identify treated cows and remove them from the milking herd to prevent antibiotics from entering the milk supply.
Sometimes if the udder becomes extremely congested, it may need to be re-milked. However, this practice stimulates further milk synthesis because intra-mammary pressure is reduced and pituitary hormones (oxytocin and prolactin) are released. Perhaps more importantly re-milking removes the leukocytes from the udder at a time when many are needed to prevent infection. It usually is unnecessary to re-milk if production is reduced below about 22 kg per day before milking is stopped. This is as per US standards, when the average milk per lactation is 10760 kg, which on a 305 days basis would be 35 kg/day. With that said, if the milk production drops to 60%, then milking can be stopped to dry the cow.
Hence it is important to keep in mind the production level at which the cows should be dried off at, which depending on a cow’s production, may result in a dry period longer or shorter than 60 days. The production level for drying off a cow generally is defined as the daily milk yield at which the return from milk is equal to the labor cost for milking plus the cost of additional feed above maintenance and pregnancy levels. Both the current and subsequent lactation periods must be taken into consideration when making this decision.
Summary:
The dry cow period must be of adequate length and should not be a time when cows are left to fend for themselves.
* Maintain 50-60 days dry period for first calf heifers as there is little benefit fpr dry period after first lactation of less than 50 days.
* A 30-40 day dry period after second and later lactations is beneficial to lifetime performance and can be done without any detriment to lifetime yield, if proper measures are taken.
* Dry period of less than 35 days and more than 70 days should ne avoided
Balanced rations should be fed in both the close-up and the far-off dry cow program to help minimize metabolic disorders. Dry matter intake should be stimulated two weeks before calving and during the first month after calving to maximize milk production in these highly stressed cows.
Dry Cow Management Considerations:
* Dry treat all quarters
* Barrier dips/teat sealants
* Mastitis vaccination program
* Nutritional supplementation
* Separate from milking herd
* Clean dry environment
* Quarter SCC at dry off and freshening
Milk production and somatic cell count are inversely related; as somatic cell decreases, milk production will increase
• Guidelines for drying off pregnant cows
• The raising of milk can be achieved by ensuring a calf a year from each cow. A cow is made pregnant between 60 and 90 days post-calving. The pregnant cow carries the double burden of producing large quantities of milk and carrying her next calf. It becomes imperative to give her rest by ceasing to milk her in the last months of pregnancy. This period during which the pregnant cow is not milked is called the “dry period”.
• During the past few weeks before birth, the growth of the unborn calf is greatest with evident heaviest demands on the cow. More nutrients are secreted in the milk than which can be absorbed from the daily intake of food in the first few months of lactation. Dry period is, thus, the optimum period when rest can be given to the milk secretory organs and the nutrients in the feed and fodder can be utilised for much-needed weight gain of the cow and proper development of the foetus instead of milk production. This is the period to clear up chronic ailments, allow the cow to build up a reserve of body flesh before calving and replenish in her body the depleted stores of minerals. When the active production of milk ceases, the alveoli and smaller ductlets in the udder involutes, but as the calving approaches, their proliferation occurs in the preparation for the start of next lactation. The secretory tissue if damaged in the previous lactation has every chance of being repaired at this stage. The resumption of reduced milk yield in previous lactation after a spell of dry period and calving is usually possible, provided bacterial invasion is not there in the udder.
• Length of the dry period
• The length of dry period is determined by the milk production and fleshiness of the cows to be dried. In high milk yielder, the nutrients are seriously depleted and as such longer dry period is required to replenish the losses of nutrients and to store adequate reserve for the next lactation. The cow should have sufficient flesh at the time of calving. To make the thin drying cow more fleshy, longer dry period is required. It becomes clear that cows yielding less milk and are fleshy, require less dry period, while high yielder and thin cows need longer period. On the perusal of the above facts and the age-old observations of dairy men, 30 to 40 days’ dry period for fleshy and low yielder and 60 to 70 days’ dry period for high yielder thin cows is suggested.
• Methods of drying off
• It is reasonable to assess as to which method for drying off is safer and convenient. There are two known methods for drying off the cows which do not naturally cease to produce milk.
• These methods are:
• 1. Stop milking
• 2. Intermittent or incomplete milking.
• Stop milking method
• This is the instant method of drying off the cows yielding moderate quantity of milk. Milk is discontinued abruptly. Udder fills to create pressure enough to stop further secretion inside the udder. The milk is gradually reabsorbed from the mammary gland to render it completely dried up. Milking at this stage will release pressure and then drying up may become a problem. The dairy owners do not elect to take up this practice because in dairy herds where mastitis is common, the incidence of infection during the dry period is higher. The stop method may cause severe swelling and encourage the development of mastitis in cows yielding more than 10 kg of milk. As such it is advisable to restrict the diet at drying off manoeuvres.
• Intermittent or incomplete milking
• All cows cannot be successfully dried up by simply stopping milking. High yielder are best dried off by withholding ingredient of feed concentrates which were found suitable for increased milk from the daily ration until production has been substantially reduced. Then the milking can be reduced to once a day or every other day and by gradually increasing the interval. Finally milking will be stopped altogether. The milk is gradually reabsorbed as lactation ceases. Heavy thick milk at this stage is no cause for worry. Since the infection of the udder in the dry period is more detrimental, the udder must be checked every day. In case of any painful swelling on udder, antibiotic and other supportive treatment must be provided immediately.
• Care of the dry cow
• From their age-old experiences, the dairymen claim that the cow’s next production record is determined by her care in the dry period. Many new infections can crop up during this period due to flare-ups of infections not apparent during lactation and which were taken care by the bacteriostatic and bacteriocidal properties of the milk. Dipping of teats on several occasions during drying off, in glycerin-iodine preparations helps in reducing the chances of infections. The intramammary infusions in all the four teats after the concluding milking can effectively seal the quarters to check further bacterial invasions of the udder.
• Good feeding, keeping free from parasites, guarding against injuries, moderate exercise, access to good pasture and daily vigil of udder (for injury or swelling) are the management practices deserve attention during dry period by dairymen.
Reference-Source-AGRICULTURE TRIBUNE
