FEEDING MANAGEMENT & STRATEGIES OF DAIRY COWS DURING DRY/TRANSITION PERIOD( 60 DAYS BEFORE CALVING)
The dry period of a dairy cow’s lactation cycle is often viewed as only a rest period to enable the cow to respond well at freshening and produce the maximum amount of milk the next lactation. Because these cattle are not contributing to the milk check and do not have the energy demands and stress of milking, they are often given the lowest quality feed on the dairy. They are not as intensively managed, and little attention is given to their well-being until they approach calving.
The time right around calving, however, is the period where cattle experience the most susceptibility to metabolic and infectious disease. The large growing fetus, the stress of calving, the drop in dry matter intake, and the change to new more energy dense feeds of the milking ration can all lead to familiar problems on dairies. These problems include milk fever, dystocia, displaced abomasum, mastitis, retained placenta, fatty liver, ketosis, acidosis, laminitis, udder edema, and uterine infections.
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These problems are not only costly in and of themselves, but they lead to other drains on the dairy producer’s cash flow. Loss of milk production is the biggest one. When a cow experiences any of the above conditions related to calving, her milk production for the following lactation is severely lowered. In addition to that, her ability to get pregnant again is compromised. Her overall health and longevity are diminished, and she is at greater risk of becoming a cull.
Recent studies have shown that the majority of cows culled from a dairy herd are culled within the first 30 days of calving. The majority of these are called for reasons directly related to calving.
With good nutrition in the dry period, there is potential to prevent or minimize the metabolic and infectious problems associated with calving.
Goals of the dry period should be the following:-
- Prepare the mammary gland for colostrum production and lactation.
- Allow for fetal growth while maintaining the cow’s body condition.
- Allow time for the cow’s digestive system to adapt or transition to the higher energy, more energy dense lactating ration.
- Help the body respond to the calcium demand during and following calving.
5. Help maintain a healthy and responsive immune system.
- Meet the energy, protein, mineral, and vitamin requirements of the cow.
- Meeting these goals is mainly accomplished through management and nutrition. Although this discussion deals mainly with the concept of nutrition, some of the most important management strategies will be mentioned. When these goals are achieved, each cow will come close to reaching her full potential of milk production. She will not be limited in her ability to get pregnant, and she will maintain good health and longevity.
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Stages of the Dry Period:-
Ideally, the dry period should be around 60 days. This number has been studied a great deal and seems to be the length of time that gives the maximum return on performance the next lactation. Cows that get less than 45 days in the dry period have significant reductions in production. Cows with over 60 days dry will show greater production the longer they are dry but will bring diminishing returns because of the length of time the cow is out of the milking herd. Sixty days seems to be the ideal length for the dry period.
The importance of the length of the dry period suggests one important management item. Accurate pregnancy diagnosis is critical to ensuring adequate time in the dry period. Only with a regular pregnancy check, usually performed by a veterinarian, will the herd manager be able to calculate a dry-off date to provide a consistent 60-day dry period for each cow?
The dry period is divided into two stages. The first stage, or far-off period, begins at dry off and extends up until 3 weeks before calving. The second stage is called the close-up (sometimes called transition, steam-up, or lead-feed) period and encompasses the 21 days before calving.
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The Far-off Dry Period: –
The main goal of the far-off dry period is to be a period of rest from lactation and allow the mammary gland to involute or shrink. The ration of the cow is changed from the energy dense lactation ration to a dry, high-forage, low-energy ration that will greatly limit milk production.
This is necessary to prevent engorgement of the mammary gland which may lead to mastitis. The ration is also balanced to meet the energy, protein, carbohydrate, mineral, and vitamin needs of the cow, as well as the developing fetus. The cow at this time is well into her third trimester of pregnancy. Ideally, the cattle in the far-off dry period are divided into three groups.
- Springing heifers 60 days from calving.
- First-calf heifers (ready to have their second calf) and thin cows.
- Fat cows.
It may not be possible, especially on smaller dairies, to have 3 pens of far-off dry cows, but there are advantages to having these 3 groups. Springing heifers are young and timid and will often have limited time at the feed bunk and watering trough if penned with larger adult cows.
This can be very detrimental to the heifer. Penning the fat cows separate from the rest of the adult cows is an important management tool that may help prevent serious health problems in the over-conditioned cows.
The Transition Dry Period:-
The main goal of the transition dry period is to prepare the cow for parturition (calving) and lactation.
This is accomplished in 4 ways: —-
The first is to provide a half-way step in transition between the feed of the far-off dry cow ration and the feed of the lactating ration. The digestive system of the cow is complex. The main stomach of the cow is a large fermentation vat with a sensitive and adaptive population of bacteria, yeast, and protozoa that will respond to changes in feed. It takes 2-3 weeks for adaptive changes to occur, and the transition dry period provides an ideal opportunity to adapt the rumen to the feed and increased energy of the lactating ration.
The second is to prepare the body for the huge demand of calcium that will occur at parturition and early lactation. It is estimated that a moderate to heavy producing cow will draw more calcium from the bloodstream than what is typically present. If the mechanism which the body uses to stabilize calcium in the blood is not in place or prepared to respond to this calcium demand at calving, calcium is rapidly depleted from the blood and the effects of hypocalcemia will be seen. Hypocalcemia (low blood calcium) is directly related to the conditions of milk fever, dystocia (difficult calving), displaced abomasum, and retained placenta.
The third way is to maximize dry matter intakes of the close-up cows right up until the time of calving. The dry matter intakes of cattle decline sharply 24-48 hours prior to calving. The day they calve they actually eat very little. This puts these high-producing, lactating animals in a negative energy balance. This means that they do not take in enough nutrients to meet their energy needs. The faster cows can begin eating after calving, the faster they can get to a point where they meet their energy needs. This will mean a stronger immune system, a stronger ability to conceive, and fewer chances of developing an infectious or metabolic disease.
The fourth and final way is to prepare the cow for the stress and trauma of calving. This can be done by making sure all nutrient requirements are being met in the diet. Adequate energy and protein are vital to a healthy immune system. Vitamins and minerals are involved as co-factors in many of the body’s important functions. There are also many management factors that are critical at this important stage in the cow’s lactation cycle. Cleanliness in the calving area, appropriate vaccinations, appropriate stocking density, comfortable pen and stall design, and the way animals are grouped all will play a big part in the health of this pre-fresh cow.
Feeding the Far-off Dry Cow – The Rest Period:-
The following table, taken from Nutrient Requirements of Dairy Cattle, National Research Council (NRC 2001), outlines the nutrient requirements for the far-off and the transition dry cow:
Nutrient Far-Off Dry Cow Transition Dry Cow
Dry Matter Intake 31.7 lbs 30.1 lbs
Energy 0.53 Mcal/lb NEL 0.72 Mcal/lb NEL
Protein 6.0 % Metabolizable Protein 6.6% Metabolizable Protein
Calcium 0.44 % ration 0.45 % ration
Phosphorus 0.22 % ration 0.23 % ration
Magnesium 0.11 % ration 0.12 % ration
Vitamin E 1168 IU/day 1202 IU/day
Selenium 0.14 mg/lb body weight 0.14 mg/lb body weight
Neutral Detergent Fiber 33 % ration minimum 33 % ration minimum
Acid Detergent Fiber 21 % ration minimum 21 % ration minimum
Non-Fiber Carbohydrates 42 % ration maximum 42 % ration maximum
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Far-off dry cows should be fed to meet the requirements in order to maintain their own body and to allow for growth of the developing fetus.
It is not healthy or desirable to feed cattle in this period of their lactation in a way to gain or lose weight. The majority of the ration should be made up of one or more rough forages. The sudden change of diet from the milking ration, which is high in energy and protein, to the dry cow ration which is low in energy and protein, but high in fiber, will enable the cow to dry up. For the remainder of the cow’s time in this period, this ration should help the cow neither gain or lose, but maintain body condition.
Cows in the far-off dry pen should be monitored on a regular basis for body condition, signs of making up (preparing for calving and lactation), and cow comfort. Many dairy producers like to feed push-out or weigh-back (the feed picked over and left uneaten) from the lactating cows to the far-off dry cows. Often all that remains from the diet of the lactating cows is stems and fibrous sorted material. However, the stems and fibers from the good quality hay or silage in the milking cow ration may still provide more than enough nutrition for the far-off dry cow and may lead her to gain weight. This should be monitored very closely when push-out or weigh-back is fed.
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Feeding the Transition Dry Cow:-
The requirements for feeding the transition dry cow are listed in the previous table from the 2001 National Research Council’s Nutrient Requirements of Dairy Cattle.
Achieving the first goal of a transition ration involves exposing and adapting the cow’s digestive system to the increased energy and protein she will consume after she calves. This is done by:-
- Using forages:- Components or ingredients that are identical or similar to those fed in the milking cow ration should be used to formulate the transition ration. For example, if there is cottonseed in the milking cow ration, there should be some cottonseed in the close-up or transition ration.
- Increasing the energy (primarily carbohydrate in the form of grain) and protein in the ration to be approximately a half-way step between the far-off dry cow ration and the milking ration. If the non-fiber carbohydrates (NFC) of the far-off dry cow ration is 26% and the NFC of the lactating ration is 40%, the transition ration should generally be about 32-33%. Protein is not quite as critical, but usually, the protein of the far-off ration is about 13-14%. A milking ration is about 18%. A good value for the close-up or transition ration is 15-16%.
- The second goal of the transition ration is to prepare the cow to respond to the sudden demand for calcium that occurs at calving. This is done by preparing the cow’s system for balancing calcium to respond when the demand occurs. The mineralized bone mass of the cow is the great storage area the cow has for calcium. Specialized cells called osteoclasts can remove calcium from the bone and balance calcium levels in the blood. During the far-off dry period there is little calcium demand and so these cells become dormant, and some die off. When a huge demand for calcium presents itself, these cells, which have been dormant, take some time to respond and reproduce. This period of time may be long enough to lead to hypocalcemia (low blood calcium) and the metabolic diseases or conditions associated with it. There is also a system in place to enhance or improve calcium absorption from the gut. Again, there is a response time associated, and the sudden demand at calving may result in a lag period where the body just cannot absorb or find enough calcium. There are several ways that feeding practices can help prepare both systems to immediately respond to the calcium demand.
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These include the following:-
- Dietary Calcium Restriction. This method restricts dietary calcium during the transition period. The cow is fed forages and components that limit the calcium intake to less than 20 grams/day. The low intake of dietary calcium keeps the gut absorption system and the bone resorption system active and thus makes the cow able to respond to the sudden demand for calcium at calving.
This method of transition cow feeding can drastically reduce the cases of milk fever and another calcium-related metabolic disease. Calcium restriction does have, however, some disadvantages. The low calcium intake can, despite the body’s best efforts, predispose cows to sub-clinical (or undetectable) hypocalcemia (low blood calcium). Secondly, the low-level calcium feed can be hard to find. Alfalfa hay, a primary staple in most dairy cow rations, is usually very high in calcium.
Balancing Dietary Cation-Anion Difference (DCAD) Using Diet Acidifiers (anionic salts):-
A more recent and more effective way to prepare the cow for the calcium demand at the onset of lactation is to add dietary acidifiers. It has been shown that how acidic or how alkaline a diet has more effect on calcium responsiveness and controlling the metabolic disease associated with low blood calcium than manipulating the amount of calcium in the diet. Anions are basic mineral elements that are negatively charged. When fed in the correct balance they are dietary acidifiers. The minerals chloride, sulfur, and phosphorus are dietary anions. Cations are basic mineral elements that are positively charged. They are used as dietary alkalinizers. The minerals calcium, potassium, sodium, and magnesium are important dietary cations.
By feeding a transition ration balanced to favor a majority of anions in the mix, the diet will be acidified. As the cow eats the ration, her body accumulates acid in its blood. The cow’s body, however, likes to remain a neutral pH, and so it has a mechanism in place to buffer the acidic condition. It does this with the calcium ion which is a strong cation that can buffer the excess of anions.
The body begins to mobilize calcium from the bone and from the gut, and thus the body is prepared to meet the demand for calcium. Acidified diets also have been shown to increase the production of Vitamin D. Vitamin D helps the efficiency with which the body can absorb calcium from the gut and mobilize calcium from the bone.
The formula which helps to create the difference between the cations and the anions is called the Dietary Cation-Anion Difference (DCAD). There are actually several formulas used to calculate DCAD, but the most common and the simplest uses just the strongest anions and cations.
It is represented as: DCAD = (sodium + potassium) – (chloride + sulfur). By increasing the amount of chloride ion and sulfur ion in the ration, it is possible to create a negative DCAD and thus acidify the diet and make it favorable to help prevent metabolic disease associated with hypocalcemia (low blood calcium).
When the diet of the transition cow is eating is acidified, her body has a very efficient mechanism to keep blood pH neutral. Movement of calcium from the bone and excretion of minerals in the urine help the body maintain a constant pH. It is so efficient that rarely can you test the blood and detect any difference in blood pH. However, in acidified diets, the urine pH is acidified, and this actually becomes an important tool in monitoring the effectiveness of a transition ration.
By sampling and testing urine from cows on a transition ration using a negative DCAD balance, one can assess the effectiveness of the acidification of the diet. A cow on a lactating ration will have a urine pH around 8.0. A cow on an acidified transition ration may have a urine pH of 6.0 or less. The pH range of 6.0 – 6.5 seems to be the ideal urine pH to produce the dietary effect needed to prevent low blood calcium.
Products used to create a negative DCAD:-
- Anionic salts are compounds that contain the strong ions (chloride or sulfur). Some examples of these are calcium chloride, ammonium chloride, magnesium sulfate, magnesium chloride, ammonium sulfate, and calcium sulfate. It is best to have someone with experience balance the DCAD in transition rations using anionic salts because there is some potential for toxicity and decreased palatability of rations made with these salts. It is best to use a mixture of salts when making transition rations, because the use of only a single salt may exceed the maximum tolerable level of the cation associated with the salt. Some of the salts are very unpalatable and an excess of these in the ration may lead to severe problems due to decrease intakes in the cows. The sulfates seem to be more palatable than the chlorides, but the chlorides are better dietary acidifiers. Because of the unpalatable nature of the anionic salts and the risk for toxicity, it is always best to feed these salts mixed in a total mixed ration (TMR).
- Anionic salts are not the only products used to help create the negative DCAD necessary to help prevent calcium related problems at calving. Recently, some new and innovative products have been developed that have attached chloride ions, a powerful dietary acidifier, to a highly palatable protein source. By combining chloride to protein in this manner, this product is able to acidify the diet without the toxic or decrease in ration palatability side effects seen with anionic salts. Two examples of products on the market with these capabilities are BiochlorR and SoychlorR.
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Supplementing Calcium Orally around Calving Time:-
This practice began many years ago as dairymen found that milk fever could be prevented by administering calcium orally to cattle around calving time. Many dairymen are able to target highly susceptible animals at risk of developing milk fever and prevent that condition by this practice. Cows on their 3rd lactation or greater, seem to be at greatest risk for developing hypocalcemia, and these cows are those that would benefit most from this preventative treatment. Since the practice started, many new products, including calcium gels and drenches, have been developed.
Many of these calcium products also contain other minerals, vitamins, and energy for the freshening cow. Most of these products contain calcium chloride as the calcium source because of its high availability and rapid absorption of calcium into the blood. However, calcium chloride is very irritating to tissues, and if aspirated will cause a very severe pneumonia. When administering drenches that contain calcium chloride, great care must be used to ensure that no fluid gets into the lungs. Much of the risk of aspiration of oral products have been eliminated by the production of calcium gel products. The calcium and other products are contained within a thick gel which the cow must swallow. This greatly reduces the risk of aspiration.
When administering products that contain calcium chloride, be careful not to injure the mouth or throat. Inflammation, abscessation, and severe infection can occur when the damaged tissue comes in contact with calcium chloride. It is also a good practice to avoid administering oral products to cows down with milk fever. The muscle function of the throat and esophagus can be severely hindered by the low blood calcium which will decrease the cow’s ability to swallow. Cows with clinical milk fever should be treated with intravenous or subcutaneous calcium administration.
- The third goal of the transition ration is to help prepare the cow for the stress and trauma of calving, prepare the udder for production, and to produce a healthy and vigorous calf. Although the preparations of the cow for lactation in the transition period is related to management, there are many things nutritionally that can aid in preparing for calving and lactation.
- One is vitamin E supplementation. Vitamin E has been shown to significantly enhance the immune function of the cow. When fed or injected in the cow just before calving, it can reduce the incidence of new infections of mastitis up to 50%. Vaccinations are frequently given in the dry period and vitamin E may improve response to these vaccinations. Colostrum is the first milk produced and is essential for the protection of the newborn calf for the first few months. Vitamin E supplementation of the transition dry cow will also directly benefit the calf as it passes via the colostrum.
- Supplementation with vitamin A and certain trace minerals (selenium, copper, and zinc) have also been credited with enhancing immune function.
- Feeding management also plays a role in enhancing preparation for calving. How a cow is fed during this critical period may be as important as what the cow is fed. Most of these principles will be discussed in the next goal of the transition ration, maximizing dry matter intakes.
- The fourth and final goal of the transition ration is to maximize dry matter intakes. The adult dairy cow’s intake of feed drops dramatically at calving. Failure to respond quickly after calving by increasing her dietary intake results in many of the metabolic problems seen in early lactation.
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Ways to maximize dietary intakes in the transition period include the following:-
- Provide access to clean fresh water.
- Offer high-quality, well-preserved feed, free of mold, spoilage or toxins.
- Feed a well-mixed TMR to avoid selection and sorting.
- Feed ad lib with about 5-10% refusal. Never feed to an empty bunk.
- Clean feed bunks regularly.
- Group animals appropriately to avoid competition and dominance at the bunk.
- Find ways to minimize heat stress.
- Avoid overcrowding.
- Maintain a clean, comfortable environment for eating and lying down.
- Provide adequate vaccination to prevent disease.
- Handle and move cattle calmly and quietly.
- Avoid leaving cattle in head-locking stanchions for too long.
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Milk fever is a term used to describe clinical hypocalcemia (low blood calcium). It is generally characterized by weakness, inability to rise, cold extremities and a generalized loss of muscle function. Cows that experience milk fever will produce approximately 14% less milk during their lactation. They are 8 times more likely to develop a case of mastitis, and 24 times more likely to develop ketosis. Milk fever cows are also more likely to have a retained placenta, uterine infection, uterine prolapse, and displaced abomasum. One study estimated that a case of milk fever may reduce the cow’s productive life by 3.4 years. Therefore, it is much better to prevent milk fever than to treat milk fever.
Following are some suggestions on how to prevent this condition:-
1. Balance dry cow transition rations to help the cow’s system prepare for the calcium demand at calving using one of the three methods that were discussed earlier. These include the following:
(a.) Calcium restriction prior to calving.
(b.) Dietary acidification by balancing the DCAD (dietary cation: anion difference).
(c.) Oral calcium supplementation at calving.
2. Beware of feeds, especially forages, with high levels of potassium. Potassium is a strong cation and feeds high in this mineral have been implicated in many outbreaks of milk fever.
3. Feed adequate calcium in the transition dry period. More calcium may be needed if feeding anionic products.
4. Supplement with adequate vitamin D. Vitamin D helps the body absorb calcium from the gut and mobilize it from the bone. Vitamin D injections are notorious for causing reactions, and so feed supplementation is usually the best.
5. Maximize dry matter intakes by feeding high quality, palatable feed. Again, beware of unpalatable products such as anionic salts.
Calcium requirements of lactating dairy cows are high relative to other species or to nonlactating cows because of the high calcium concentration in milk. Thus, inorganic sources of calcium, such as calcium carbonate or dicalcium phosphate, must be added to the rations of lactating dairy cows. For the first 6–8 wk of lactation, most dairy cows are in negative calcium balance, ie, calcium is mobilized from bone to meet the demand for milk production.
This period of negative calcium balance does not appear to be detrimental so long as there is sufficient dietary calcium such that bone reserves can be replenished in later lactation. The availability of dietary calcium for absorption varies with dietary source. Dietary calcium from inorganic sources is generally absorbed with greater efficiency than that from organic sources. Furthermore, cows in negative calcium balance absorb calcium more efficiently than cows in positive calcium balance.
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