The Window of Opportunity
The transition phase of the adult dairy cow is usually defined as the last three weeks of the dry period and the first seven to ten days of lactation. Proper care and nutrition of the dairy cow during this period will improve the health and increase the production potential during the entire lactation. At no other time in the life of the dairy cow, can nutritional intervention have such a dramatic effect on production potential, in such a short period of time.
As the pregnant cow approaches the end of the dry period, or pregnant heifers approach the end of their first pregnancy, their nutritional requirements increase considerably. The foetus is growing more rapidly during this time period than at any other point in gestation. The mammary gland is preparing for the ensuing lactation by increasing in size and starting production of mammary gland secretions. However, at the same time, the dry matter intake of the close-up dry cow gradually decreases as she approaches parturition. Since the nutritional requirements increase and dry matter intake decreases, ration changes must be made to increase the energy and protein density of the ration in order to fulfil these requirements. Failure to do so will result in negative energy balance and subsequent weight loss in the close-up dry pen. The Net Energy for lactation (NEI) should be between 0.68 and 0.72 Mcal/Ib. of dry matter and the crude protein should be a minimum of 16% on a dry matter basis.
Every effort must be made to maximise the dry matter intake of the close-up dry cow. High quality, palatable forages should be utilised along with smaller proportions of the same commodities utilised in the lactating ration. Exposing the rumen micro-organisms to the same feeds used in the lactating ration promotes the development of the populations needed for maximum utilisation of these feeds once the cow is introduced to the lactating ration. This allows the fresh cow to go on feed faster, increase dry matter intake, have fewer digestive upsets and increase production earlier in lactation. Cleaning the feed bunks on a regular basis will prevent the build-up of spoiled feed in the bottom, also resulting in improved dry matter intake. Keeping the feed pushed up to the cows is important if flat cement slabs are used for feed bunks. Overcrowding the close-up pen and/or insufficient bunk space for the number of cows in the pen should be avoided. Older, more dominant cows may push first calf heifers away from the feed bunk. These animals may need to be separated if this problem exists.
The dry matter intakes of the close-up dry cows and heifers should be closely monitored to ensure that the needed nutrients are being consumed. Even though the energy and protein density of the ration has been increased, the close-ups must consume so many pounds of the ration in order to fulfil their nutritional requirements. This information is essential to the nutritionist in his efforts to decrease metabolic disease around the time of freshening.
When the lactating cow is dried up, she is usually taken off of a ration that contains a substantial amount of concentrate and put on a ration of mostly lower quality forages. The rumen papillae (the finger like projections that protrude inwardly from the lining of the rumen thai are involved in absorption of nutrients from the rumen) shrink in size when this ration change takes place. This process is considered necessary to provide the lining of the rumen a chance to rest and regenerate. However, if the rumen papillae are not stimulated to lengthen out before the cow is placed back on the lactating ration consisting of more concentrates, severe digestive upsets and acidosis may occur. The rumen papillae are stimulated to lengthen out by the presence of volatile fatty acids in the rumen. Volatile fatty acids are produced as a result of the fermentation of grains in the rumen. Therefore, the close-up ration must contain enough starch from grains to produce the volatile fatty acids necessary to stimulate the development of the rumen papillae. This process takes approximately 5 weeks to complete, so it is important to utilise the last 3 weeks of the dry period to get this process well on its way.
Development of the rumen papillae is just as if not more important to the springer heifer since she has been on a high forage ration for close to a year before she freshens. A large percentage of dairies do not keep track of breeding dates on heifers or do not utilise the computer to generate a list of heifers ready to be moved to the close-up pen. It is fairly common practice to visually observe heifers on a weekly basis to determine which ones should be moved to the close-up pen. Heifers are much more difficult to determine the approximate calving date by visual observation than are cows. As a result, some heifers are not moved to the close-up pen soon enough, and do not receive the benefits of the close-up ration for the necessary amount of time. Both the heifers and cows should have the date written down or entered into the computer when they are moved into the close-up pen. The days in the close-up pen should be recorded for each animal when it calves. Close-up rations are often blamed for metabolic disease at freshening, when the reason is insufficient time in the close-up pen.
Probably the most common metabolic disease observed by the dairyman around the time of calving is periparturient hypocalcemia or milk fever. This problem also needs to be addressed in the formulation of the close-up dry cow ration. Research has shown that by altering the ratio of the positively charged ions (cations) such as Sodium (Na+) and Potassium (K+) to the negatively charged ions (anions) such as Chloride (CI ) and Sulphur (S ), the metabolism of the dairy cow can be altered so that more calcium is absorbed from the diet and also from the bones. This is commonly referred to as the DCAD (dietary cation anion difference) ratio. A negative DCAD, which would indicate more anions than cations, greatly improves the ability of the dairy cow to increase calcium absorption from the diet and its bones.
Probably the most common way to change this DCAD ratio is to add “anionic salts” to the ration of the close-up dry cow. These anionic salts such as ammonium chloride, calcium chloride, calcium sulphate and magnesium sulphate contribute chloride and sulphur anions to decrease the DCAD ratio. If the cow ingests a sufficient quantity of these anionic salts, calcium absorption is greatly improved and the signs associated with low blood calcium levels at calving are significantly decreased. However, the major drawback of anionic salts is the fact they are not very palatable. If anionic salts are added to the ration, the dry matter intake of the close-up cows is usually decreased. It is very common for the forages being fed to the close-up dry cows to be high in potassium. If this problem exists, more anionic salts have to be added to receive a negative DCAD ratio. Therefore, it becomes very difficult to add the appropriate amount of anionic salts to counteract the high potassium forages, and still maintain the desired level of dry matter intake. If dry matter intake decreases, the animal enters into a state of negative energy balance and also will most likely not be able to consume enough of the anionic salts to improve calcium absorption. If forage inventories permit, utilising low potassium forages in the close-up ration greatly enhances the success rate of feeding anionic salts.
Potassium is usually higher in forages that are harvested from fields that are heavily fertilised with manure. Reserving some fields for forages utilised in close-up rations that are not fertilised with manure is extremely helpful. Also, the first cutting of alfalfa is usually much higher in potassium than are subsequent cuttings, especially if the fields were fertilised with manure during the winter months. Molasses and whey are also quite high in potassium and their use should be kept to a minimum.
In the past, high calcium levels have received the blame for causing milk fever. As a result, rations have been formulated that are extremely low in calcium to try and prevent milk fever. The theory was that low calcium levels would stimulate the animal to initiate the process of reabsorbing calcium from its bones so it would already have this process in place at the time of calving. The animal could then draw from its own calcium reserves in its bones to compensate for the high level of calcium secreted into the colostrum. This approach was often successful at reducing the incidence of clinical milk fever, but many other problems associated with low blood calcium levels still persisted.
Calcium is necessary for all muscle contraction. Animals that have low blood calcium levels but not low enough to exhibit signs of milk fever, have a multitude of problems related to a decreased muscle contraction in the body. This syndrome referred to as subclinical hypocalcemia results in problems such as retained placenta, increased incidence of uterine infections, digestive upsets and decreased dry matter intake due to poor contraction of the rumen musculature and displaced abomasum. Even though the theory of feeding low levels of calcium to the close-up dry cows seemed effective in decreasing the incidence of milk fever, these other problems previously mentioned still had severe effects on the overall health and productivity of the lactating cows.
The ideal approach would be to increase the ability of the cow to absorb more calcium from its digestive tract and bones and at the same time supply extra calcium in the diet. When anionic salts are fed, additional calcium is usually added to the ration in an effort to accomplish this. However, because of the prevalence of high potassium forages and the poor palatability of anionic salts, problems with milk fever and subclinical hypocalcemia often occur sporadically in herds feeding anionic salts. If anionic salts could be fed and at the same time increase the dry matter intake of the close-up dry cow, the incidence of metabolic disease around the time of freshening would be greatly decreased. One product is available that contributes a high level of the chloride anion and at the same time is very palatable’. University studies have also shown that rumen microbial yield and dry matter intake are increased in close-up dry cows that consume this product.
In review, the following things must be accomplished in the close-up dry cow ration in order to maximise the health and productivity of the fresh cow:
- Increase the energy and protein density
- Improve palatability and dry matter intake
- Stimulate the development of the rumen papillae
- Increase the absorption of calcium from the diet and increase calcium resorption from the bones
- Adapt the rumen microflora to the feeds found in the lactating ration.
The fresh cow ration also needs to be formulated to increase the potential profitability and decrease the incidence of nutritionally related disease so often seen around the time of freshening. It was mentioned that it takes approximately 5 weeks for the rumen papillae to lengthen out once exposed to the volatile fatty acids produced from starch fermentation. If this process is initiated in the close-up ration, it still takes approximately two more weeks after freshening for the process to be completed. The fresh cow ration should contain a level of non structural carbohydrates (starch, sugar, pectin, etc.) that is intermediate between the close-up ration and the high production ration. This permits the continued maturation of the rumen papillae without the danger of rumen acidosis developing.
Exposing the rumen of the fresh cow to high levels of NSC results in the production of large amounts of volatile fatty acids. Shorter rumen papillae have less surface area available for the absorption of these volatile fatty acids. This results in a build-up of acid in the rumen and an ensuing rumen acidosis. Severe rumen acidosis results in inflammation of the rumen lining and permits bacteria to penetrate the rumen wall and enter the bloodstream. These bacteria often end up in the liver and cause the development of liver abscesses. Some of the rumen wall may be sloughed which compromises the ability of the rumen to absorb volatile fatty acids even more. If they survive, these animals usually have to be culled because of poor productivity.
Milder cases of rumen acidosis result in laminitis and other foot problems associated with laminitis such as sole abscesses, sole ulcers, uneven growth of the hoof wall and white line disease. Diarrhoea and butterfat suppression are other signs of rumen acidosis. Decreased dry matter intake and poor utilisation of the ration are also signs of rumen acidosis.
Displaced abomasum is another common problem seen in fresh cows. Lower levels of NSC and higher fibre levels have been shown to decrease the incidence of displaced abomasum. Length of the fibre in the fresh cow ration is especially important in maintaining rumen health and preventing displaced abomasum. However, if a total mixed ration contains a large amount of long course fibre, it is easy for the cow to sort through the longer fibre and eat more of the concentrate fraction of the ration, thus increasing the chances of rumen acidosis and displaced abomasum.
Higher levels of protein in the fresh cow ration have been shown to increase dry matter intake and increase peak milk yield. Crude protein levels should be in the 18 to 20% range on a dry matter basis. Therefore, forages that contain high levels of protein such as alfalfa, are ideal for inclusion in the fresh cow ration.
Fresh cow rations that contain an intermediate level of NSC and high levels of protein and fibre will naturally be lower in energy. For this reason, the fresh cow should only be on this ration for 7 10 days. This allows ample opportunity for the rumen papillae to mature and decreases the chances for rumen acidosis and displaced abomasum. It also provides the necessary time for further adjustment to the lactating ration and increases in dry matter intake without affecting rumen health. However, since the ration will be lower in energy, cows should not be fed this ration for much more than ten days.
The following parameters should be used when formulating the fresh cow ration:
- Higher levels of longer length fibre
- High quality forages that are high in protein
- Intermediate level of NSC between the close-up ration and the lactating ration
- Consist of the same ingredients as the lactating ration
- Only fed for the first 7 10 days of lactation.
The benefits from a well managed transition cow program far outweigh the costs and labour to implement and manage it. Studies have shown that 8 to 10% of all lactations begin with milk fever. Cows that experience milk fever will produce approximately 14% less milk during their lactation. A 100 cow dairy with a rolling herd average of 20,000 lbs. and a rate of 10% milk fever would lose approximately 280,000 lbs. Of milk per year. At $12.00 per hundred weight, that amounts to $33,600 loss. This loss is strictly due to the milk fever episode and does not take into consideration all the other problems that may accompany milk fever. If these other losses are taken into consideration, a conservative estimate would $40,000 per 100 cows in the example just mentioned.
Cows with milk fever have been shown to be up to 8 times more likely to develop a case of mastitis, especially coliform mastitis. One study showed that milk fever cows are 24 times more likely to develop ketosis than non milk fever cows. Milk fever also increases the incidence of retained placenta, uterine infections, uterine prolapse, calving problems, displaced abomasum and digestive upsets. Another study indicated that a case of milk fever may reduce the cow’s productive life by 3.4 years.
Ketosis is a metabolic disease that exists to some extent in all dairy herds. The major underlying cause of both ketosis and fatty liver syndrome is decreased dry matter intake both in the close-up pen and in the fresh cows, resulting in a negative energy balance. Cows with ketosis often have a decreased appetite and are sluggish in appearance. A very high percentage of cows with ketosis go undiagnosed and untreated. This greatly limits their production potential during lactation. Fat cows are more prone to ketosis and fatty liver because they have lower dry matter intakes than cows that are not overconditioned. However, a good transition program that consists of a well balanced highly palatable ration decreases the incidence of ketosis and fatty liver by improving dry matter intake.
Cows that have twins have gained a well deserved reputation of falling apart after calving. Recent work has shown that the dry matter intake of cows with twins drops off approximately 2 weeks before cows with single pregnancies toward the end of the dry period. If a cow is diagnosed with twins at the time of pregnancy check, she should be moved into the close-up pen 5 weeks prior to calving. With a good transition program, and more time in the close-up pen, cows with twins can calve with relatively few problems, experience less weight loss and have a more productive lactation.
The exact cause or causes of udder edema in first calf heifers has not been completely determined. However, high potassium forages and close-up rations with positive DCAD ratios seem to predispose heifers to more severe udder edema. The majority of heifers on a close-up ration with a correctly calculated DCAD ratio will experience much less udder edema. Excessive udder edema is costly by increasing the number of heifers with broken down udders, increased incidence of mastitis and decreased milk production.
Regular reproductive programs have been in place on dairies for many years. Yet even with the same veterinarian and the same type of program, the reproductive efficiency varies greatly among dairies. When poor conception rates are a problem, it is most likely blamed on infertile bulls, poor quality frozen semen, improper techniques by the AI technician, breeding cows that are not in heat and poor heat detection. First service conception rates are a good way to evaluate the success of the transition cow program. In every case I’ve observed, where there was a major improvement in the management and nutrition of the transition cows, there was a dramatic improvement in the first service conception rate, especially in first calf heifers.
Research from North Carolina indicated that it takes approximately 60 days for an egg to ovulate from the ovary once it has been stimulated to mature. The voluntary wait period to first breeding for the average dairy is usually around 60 days. If the cow is in a negative energy balance at the time the egg is stimulated to mature, the fertility of this egg is extremely low 60 days later when it ovulates. The greatest time of negative energy balance is usually around the time of parturition. Therefore, probably the worst time to breed a cow would be 60days after calving. Herds that have a good transition cow program in place have extended their voluntary wait period to 80 90 days without an increase in average days open. At the same time, they have increased their first service conception rates and reduced their semen costs.
The most dramatic change observed in herds that improve their transition cow program is their dry matter intakes around the time of freshening and how fast the fresh cows come to their milk. It is not uncommon to see cows with over 100 lbs. Of milk within 14 days of calving. Monitoring the milk weights of the early fresh cows is an excellent way to evaluate the success of the transition cow program. Also, the number of cows in the herd that are over 100 lbs. and less than 60 days fresh along with the total number of cows in the herd over 100 lbs. Of milk are valuable figures. Herds with a good genetic base that are milking 3 times a day should be able to reach a goal of 15 to 20% of the herd over 100 lbs. Of milk. Likewise, herds milking 2 times a day should be able to have 10 to 15% of their herd over 100 lbs. Of milk. With a good lactating cow nutrition program, these cows will peak much higher than before and remain more persistent during their lactation, resulting in a much more profitable dairy operation.
Good transition cow programs are essential in maximising the response to BST. Cows that are in a more positive energy balance, have higher dry matter intakes and are not suffering from metabolic disease around the time of freshening have a much greater response to BST. Increased milk production must be compensated for by increased dry matter intakes. Excellent response to BST can be seen without a resulting weight loss when dry matter intakes are improved through good transition cow nutrition, a comfortable environment and a well balanced lactating cow ration.
If the cows in transition are managed intensively with proper nutrition and cow comfort, the dairyman will receive dividends throughout the entire lactation.
These dividends will be received in the following ways:
- Higher milk yields earlier in lactation
- Higher peak milk yields
- Greater persistency throughout lactation
- Less metabolic disease around the time of freshening (milk fever, ketosis, etc.)
- Decreased retained placenta and uterine infections
- Improved reproductive efficiency
- Decreased udder edema
- Improved dry matter intakes before and after freshening
- Improved colostrum quality
- Decreased incidence of displaced abomasum
- Increased response to BST
- Decreased death loss and cull rates, especially in fresh cows.
This narrow window of time, called the transition period, has more effect on the profitability of the dairy operation than any other time in the lactation cycle. Focusing management efforts on this period will yield results rapidly and easily monitored.