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Training the dry period final MSD Salud Animal Salud Lechera
- 1. The dry period The basics
- 3. What is the dry period? Lactation Dry Period Halting of milk removal Calving Non- lactating period Lactation Calving Lactating period To ensure milk production, cows must calve regularly
- 4. Why do we need a dry period? Lactation To ensure high milk production Milk Production Dry Period Halting of milk removal Calving Non- lactating period Calving Lactating period Pregnant; No dry period Not Pregnant; No dry period
- 5. This is a lactation curve Milk yield declines during lactation
- 6. The Udder - Anatomy
- 7. Epithelial cells in the udder need renewal Number of mammary epithelial cells and their secretory activity determine shape of lactation curve Number or activity of mammary secretory cells Milk yield Number or activity of mammary secretory cells Milk yield
- 8. Epithelial cells continuously die and renew Apoptosis (cell death) New cell Capuco and Akers, 1999 10 cells 10-2+1 9 cells (1 new) Decreased milk yield due to: Declining cell numbers Decreasing secretory capacity
- 9. We need a dry period Capuco et al., 2003
- 10. The dry period Three stages Apoptosis (cell death) Cell renewal Cell renewal New cells start secreting Colostrum Formation Steady State Involution
- 11. Physiological cycle of lactation Lactation 300-400 days Involution Steady state Colostrum formation Old cells New cells
- 12. More milk after a 60 day dry period Bachman and Schairer, 2003
- 13. A 60 day dry period is ideal Optimal length to ensure high milk production Kuhn et al., 2006
- 14. Heifers need a 60 day dry period Pezeshki et al., 2009 * * * * Significant difference 56d and 35 d (p<0.05)
- 17. The dry period Good management is essential success factor for high production in late lactation Cow comfort Hygiene Feeding
- 18. Udder health The key for prevention lies in the dry period 0 20 40 60 80 100 120 140 -10 -5 0 5 10 15 20 25 30 Days relative to calving Cases per 10.000 cow-days at risk Heifers Cows
- 19. Recharge of udder health Cure and prevention of blanket antimicrobial DCT vs no DCT Cure averages 71-85% (Halasa et al., 2009a) Prevention averages 39% (Halasa et al., 2009b)
Notas do Editor
- Welcome to the training module on the basics of the dry period. My name is Jantijn Swinkels. I am the Global Technical Director of Udder Health.
- In this training module, we will to address the basics of the dry period, including the following topics of discussion: What is a dry period? Why do we need a dry period? Physiology of lactation Ideal length of the dry period Dry period management Udder health
- Biologically, cows produce milk essentially for their own calf. So to ensure milk production, cows need to calve regularly. In nature, cows would stop producing milk when they are close to calving. This is probably because the fast growth of the calf costs too much energy and the udder needs to prepare for the next lactation. Modern high producing cows, produce so much milk that they do not dry off automatically, but the farmer has to simply stop milking them. This cessation of milking is called drying off and is the beginning of the dry period. So, the dry period is the period between the halting of milk removal and calving. The dry period is also sometimes called the non lactating period.
- Why do we need a dry period? A dry period prior to parturition in dairy cows is mainly important for optimal milk production during the subsequent lactation. If a dry period is omitted in pregnant cows, milk production may be reduced by 20% or more after calving. If a dry period is omitted in non pregnant cows and we just continuously milk them, milk production would slowly but surely decline as well. Such cows would have to become pregnant and calve to ensure high milk production in the future. Therefore, both calving in combination with a dry period are essential to ensure high milk production.
- This is a schematic lactation curve. A lactation curve is the amount of milk that cows give plotted against the days of lactation. We typically see an increase of production after calving, a peak at 7-8 weeks and then a gradual decline. An important question is; why do we see this gradual decline?
- To answer the question why we have a decline in milk production after peak production, let’s first look at the basic mammary gland anatomy and physiology. A bovine udder has 4 quarters. The interior of each quarter is composed of a teat cistern, gland cistern, milk ducts, and glandular tissue. The glandular tissue or secretory portion contains millions of microscopic sacs called alveoli. Each alveolus is lined with milk-producing epithelial cells and is surrounded by muscle cells that contract and squeeze milk from the alveolus during milking. Blood vessels bring nutrients to each alveolus where epithelial cells convert them into milk. Between milkings, milk accumulates in the alveolar spaces, milk ducts, and cisterns. During milking, the accumulated fluid is removed through the teat ducts.
- Why is the lactation curve as it is? It is the number of mammary epithelial cells and their secretory activity that determine the shape of the lactation curve. Depending on the species, increases in the number or activity of mammary secretory cells account for increased milk yield to peak lactation. Conversely, declining mammary cell number or secretory activity accounts for declining milk yield after peak. Management and disease can potentially impact the proliferation or loss of cells during lactation. Knowledge about mammary cells that are capable of cell proliferation and of pathways that regulate proliferation cell death may provide means to alter persistency of lactation.
- Epithelial cells continuously die and new cells are formed. Here you can see a representation of this process. Open circles represent the initial populations of cells; cross-hatched circles depict new cells formed by cell proliferation; and cells that die during this period are depicted by black circles. This picture schematically shows that 2 epithelial cells are dying and 1 new epithelial cell is being formed. This is how cows are undergoing net regression of the number of epithelial cells after peak lactation. Independent of pregnancy, after peak lactation, decreased milk yield with advancing lactation is primarily the result of declining cell numbers. However during late lactation, when cows become pregnant, the secretory activity per cell declines also. It is likely that a decline in secretory capacity per mammary cell accompanies advanced pregnancy due to conflicting metabolic demands of gestation and lactation.
- To know the exact mechanisms behind this decline, cell turnover is important. If we can stop this gradual decline, we could simply continuously milk cows. Furthermore, if we do not need for the cow to have a calf in order to produce more milk, we could relieve the cow from the burden of pregnancy and the health risks and pain of calving. However, we do not completely understand the complicated mechanisms behind cell turnover, so declining milk production after the peak is still a reality we have to live with. We know that BST injection, increasing milking frequency, and giving cows more hours of light are ways to increase persistency. However, even then milk production declines. It may be at a slower rate but it declines. So, finally, milk production will decrease. So, there is no discussion – in order to ensure high milk production, cows must calve and have a dry period. Do we need a dry period to improve the cows nutritional status? Some people believe that a dry period is necessary in order to fill the cow’s fat reserves, but this is not the case. Although the data are not definitive, they strongly suggest that a dry period is necessary for reasons that center on the mammary gland rather than on the nutritional status of the animal.
- The recharge of milk production in the dry period can be divided in three stages Involution, steady state and colostrum formation. In the involution stage, cell death or apoptosis prevails while the balance shifts towards cell renewal in the steady state. The cell renewal continues in a slower rate during colostrum formation, but in this phase the existing new cells start secreting milk and the cow is ready for calving
- The recharge of milk production is cyclic and thus a continuous process as depicted schematically here. The circles represent the epithelia cell layer, dark blue represents the growth of more new epithelial cells, grey is more apoptosis. The physiological cycle contains 4 phases. Lactation is normally somewhere between 300-400 days and as discussed milk production shows a gradual decline after peak. After lactation we have the dry period. The dry period starts with involution, then the steady state and finally the colostrum formation period. In the involution period, cell death is dominant. In the steady state, the cell renewal starts and continues during the colostrum formation when these new cells start secreting as well. Each dry period stage needs a sufficient amount of time to be completed for optimal milk production after calving.
- This slide shows the results of 6 different publications that compare the relative milk production of long dry periods, represented here by the blue bars and put at 100% compared to short dry period, represented here by the pink bars. All these papers show that cows give more milk after a 60 day dry period compared to a shorter 30-40 days dry period. Apparently the dry period, needs a certain amount of time to ensure a high milk production afterwards
- The results of a study by Kuhn et al., from 2006 are shown here. They looked at the milk production of two adjacent lactations, lactation 1-2, 2-3 and 3-4 and the length of the dry period in between. So the milk of a whole lactation before and after calving was included and the effect of the length of the dry period on the milk production of the two adjacent lactations was calculated. The 60 day dry period is set at 0 and the milk production loss when we shorten or lengthen the dry period is shown on this picture. The conclusion is that a 56-65 day dry period is optimal from a milk production point of view. A second conclusion is that in heifers, the impact of a somewhat longer dry period is different than in older cows.
- This graph compares the milk production of heifers after a 35, 42 and 56 day dry period. The milk production is significantly higher after a 56 day dry period. This is confirmed by a lot of other research that shows that heifers need a longer, 60 day dry period to have a productive next lactation. It has been hypothesized that their need for a long dry period is due to their young age; they need sufficient time for mammary growth to be fulfilled
- A short dry period can be an option in some circumstances on some farms. The advantages of a short dry period are that it can improve the negative energy balance after calving, which is probably an indirect consequence of lower milk production It can be a solution on farms that have to deal with older over-conditioned cows because they are more sensitive to a negative energy balance. Also on farms where only high energy silage is available for the dry cows, a short dry period can be beneficial because cows get less time to grow fat. Disadvantages of a short dry period are less milk after calving, especially in heifers. However, this loss may be compensated by more milk before calving. If we would plan for a 60 day dry period in heifers and shorter dry period for older cows, this might look ideal on some farms, but would be complex and therefore not convenient for a majority of farmers. Also appointing different dry period lengths to different cows in the herd is a system that is prone to errors, which could have costly consequences such as for example antibiotic residues in the bulk milk tank. Another disadvantage of a short dry period is the risk that is involved.
- Short dry periods are risky. Let me explain why. The average gestation length of a Holstein Fresian dairy cow is approximately 280 days. If farmers aim for a dry period of, for example, 60 days, cows should be dried off at 220 days (280-60) after the last insemination date, if pregnancy is confirmed. Despite careful planning, the dry period length remains difficult to predict. The dry period can be shortened unexpectedly due to natural variation, disease or mistakes. Firstly, in real life the exact moment of calving has a margin of accuracy of +/- 3 days in adult cows, so calving 3 days earlier than expected is normal. Secondly, 3-5% of pregnant cows carry twins and they tend to calve 7-13 days earlier than their single calf-carrying herd mates. What’s more, cows can abort and as a result calve a month earlier than planned. Thirdly, even in well managed herds it happens that the cow is not pregnant from the last insemination but from an earlier insemination. If cows are pregnant from an earlier insemination, some cows, around 5% still show heat signs. The ovarian cycle of a cow is 21 days, so it is well possible that some cows are mistakenly inseminated again 21 days later. If this happens, the farmer assumes the cow is pregnant from the last insemination while in reality it is not. This cow can then calve 21 days earlier than expected, thereby unexepectedly shortening the dry period with 21 days So, the dry period can be shortened unexpectedly due to natural variation, twins, disease or mistakes. Therefore, planning a dry period length that is long enough, provides the necessary safety margin. Then, if a cow calves earlier than planned, she still has a chance for a reasonable dry period length, allowing enough epithelial cells to replicate to ensure milk production after calving. So, planning for a short dry period of 30-40 days is risky. For the reasons indicated above, some cows will unexepectedly have a very short or no dry period depriving the epithelial cells the time needed to replicate; this results in a very low or no milk production after calving. This frequently leads to culling of the animal. For these reasons, a short dry period can be a disappointing and costly exercise.
- Cell renewal can be impacted by disease. And disease can be impacted by farm management. However, too often it appears that farmers are drying off their cows routinely without taking into account the targets they want to reach through deliberate dry cow management. Dry cows often are kept in poor housing, with poor climate and feeding routines. This observation has led some people to qualify dry cows as “the forgotten group”. The dry period should be managed with just as much attention and dedication as any other stage of lactation. But successfully managing dry cows on a daily basis is a challenge, requiring knowledge, understanding, concentration, motivation and organisation. A dry and clean environment, minimising stress for the cows through cow comfort and ensuring that every cow eats the calculated ration every day, are critical success factors for a healthy transition period, steering clear of problems such as milk fever, ketosis, metritis and more. Good management is an essential success factor for high production in the next lactation.
- This picture shows when clinical mastitis occurs relative to calving It is clear that the majority of clinical mastitis cases both in heifers and in older cows, occur in the first month after calving. Many clinical mastitis cases in recently calved cows are flare-ups from new infections originating from the dry period. So, preventing these new infections in the dry period would lead to less mastitis after calving. Therefore, the dry period is very important for udder health
- Especially in high somatic cell count herds, but even also in low somatic cell count herds, many cows have an existing subclinical mastitis in 1 or more quarters at dry off. In addition, the healthy, non infected animals are very sensitive for new intramammary infections both just after dry off and around calving. Just after dry off, the teat canal is still open. Due to the pressure on the udder, cows can leak milk and also it takes a while before a natural teat plug is formed. This is the reason for new infections just after dry off. Just before calving the immune system for cows is suppressed and the teat canal can already be opened due to milk leaking. This combination make cows sensitive for new infections around calving. Blanket dry cow antibiotic treatment can contribute to both the cure and the prevention of new infections in the dry period. What can we expect from a dry cow treatment? We can expect a high cure, averaging from 70 to 85% of existing subclinical infections, at dry off, when compared to no dry cow treatment. The prevention of new infections through dry cow treatment averages around 40% compared to no dry cow treatment. Internal teat sealants do a good job as well in preventing new infections in the dry period, but they do not cure existing infections Curing 70-85% of existing infections and preventing 40% of new infections is a significant contribution to udder health. It is therefore no surprise that the majority of farmers have adopted routine blanket dry cow treatment.
- In this training module, we tried to address the basics of the dry period. We defined the dry period as the period between the halting of milk removal and calving We have tried to address the reasons why we need a dry period, we need it to ensure high milk production in the following lactation We have discussed the physiology of lactation, through udder anatomy and the cycle of epithelial cell renewal We have concluded that for the majority of farms the ideal length of the dry period is around 60 days, although on some farms a shorter dry period might be more appropriate We identified that dry cow management is crucial to recharge the milk production capacity. The Dry period is an essential period for udder health because cows are very sensitive for new infections during this period. Curing and preventing such infections is crucial in the control of udder health.
- You will now be presented with a course assessment. This assessment consists of 10 questions which will test your knowledge of the topics covered in this module. Please note that more than one answer can be right. You must receive a score of 80% or higher to pass the test and successfully complete the course. If you do not pass on the first attempt, you can review the content of the course and take the assessment again. After answering each question, click the “Submit” button to submit your answer. You will receive immediate feedback so you will know if you answered correctly or incorrectly. Please note that if you exit the assessment in the middle, either by navigating to a slide in the course or by closing the course, you will have to start the assessment again from the beginning. At the end of the assessment, your cumulative score will be displayed. Good luck!