Changes

'''Insufficient long fibre in the diet''': It is essential that the diet contains adequate fibre of 2-5cm in length, as it stimulates rumination and forms the rumen mat, where much fermentation occurs. Insufficient long dietary fibre can therefore be detrimental to rumen health. If sufficient fibre of the wrong length is contained within the ration, rumen function will also be suboptimal rumen function. Fibre that is chopped too short will not stimulate rumination, and fibre greater than 10cm in length can be selectively sorted out of the diet by the cows themselves. Because the difficult of feeding dairy cattle lies in providing sufficient metabolisable energy, there is a tendency for farmers to focus on making highly digestible (and therefore high ME) silage rather than that of good fibre quality; this contributes to a lack of sufficient long fibre in the feed.

'''Insufficient long fibre in the diet''': It is essential that the diet contains adequate fibre of 2-5cm in length, as it stimulates rumination and forms the rumen mat, where much fermentation occurs. Insufficient long dietary fibre can therefore be detrimental to rumen health. If sufficient fibre of the wrong length is contained within the ration, rumen function will also be suboptimal rumen function. Fibre that is chopped too short will not stimulate rumination, and fibre greater than 10cm in length can be selectively sorted out of the diet by the cows themselves. Because the difficult of feeding dairy cattle lies in providing sufficient metabolisable energy, there is a tendency for farmers to focus on making highly digestible (and therefore high ME) silage rather than that of good fibre quality; this contributes to a lack of sufficient long fibre in the feed.

[[Image:Cows Eating TMR.jpg|thumb|200px|right|Cows eating a total mixed ration. Source: Wikimedia Commons; Author: Tractorboy60 (2007)]]

[[Image:Cows Eating TMR.jpg|thumb|200px|right|Cows eating a total mixed ration. Source: Wikimedia Commons; Author: Tractorboy60 (2007)]]

'''Overmixing the total mixed ration''': If the total mixed ration is mixed too much in the mixer wagon, the long fibre will be broken into shorter pieces and hence become less effective. This can be overcome by adding the forage into the mixer wagon last, ensuring minimal degradation.

'''Overmixing the total mixed ration''': If the total mixed ration is mixed too much in the mixer wagon, the long fibre will be broken into shorter pieces and hence become less effective. This can be overcome by adding the forage into the mixer wagon last, ensuring minimal degradation.

'''High proportions of starches and sugars in the diet''': Dairy farmers often include large amounts of rapidly fermentable carbohydrates in the diet in order to meet energy requirements and maintain body condition score and milk production. These carbohydrates can take the form of grain, concentrates or maize silage. However, rapid fermentation leads to over-production of volatile fatty acids, and thus subacute rumenal acidosis. This actually makes digestion less effective, so the cattle do not benefit as much as the should do from the extra sources of metabolisable energy. A vicious cycle can ensue of poorer performance and supplementary feeding of concentrates.

'''Sorting of long fibre''': When the fibre in a total mixed ration is longer than 10cm, cows tend to sift through the diet and consume smaller, more palatable particles and the pieces of forage too small to sort out. This alters the concentrate-to-forage dry matter ratio which is actually eaten by the cow (even if it is correct in the diet presented to the animals), which increases the risk of developing subacute rumenal acidosis. There is the additional problem in this situation that animals lower down the hierarchy, such as heifers, will eat the remainder of the sorted diet and thus not receive tbe energy they require. Both groups of animals are then likely to be in negative energy balance, but for different reasons.

'''Inadequate dry cow diet''': the diet fed immediately before calving (the transitional cow diet) should be formulated to stimulate the development of rumen papillae and the acquisition of an appropriate colony of microflora. This should ensure that cattle can adequately ferment the post-calving diet and effectively absorb the nutrients it provides. Therefore, if the dry cow diet does not encourage these processes, volatile fatty acids can accumulate in the rumen when the lactation diet is introduced, leading to SARA. This is a particularly common problem, since dry cows are "non-milkers" and so tend to be the forgotten members of a herd.

'''Overestimation of forage dry matter content''': The dry matter of forage must be estimated in order to calculate how much of ir should be included in the diet. The cut of for healthy rumen function is a concentrate-to-forage dry matter ration of 60:40; if this is exceeded then SARA can develop. Therefore, if the dry matter content of forage is overestimated, a relatively smaller quantity of the fodder will be included in the diet, tilting the ratio to potentially detrimental proportions.

'''Post-calving nutrition''': The "transitional period" for a dairy cow is defined as the period four weeks pre-calving, to four weeks-post calving. Often, farmers will provide a transition diet before calving, but introduce the lactating cow diet immediately afterwards. In the first four weeks after calving, the rumen cannot properly handle diets that are dense in energy: the ration fed in this period ideally should contain 10% more energy than the transition diet fed before calving. the rationale to this is that dry matter intake will be increased, and will then remain at high levels throughout lactation. Animals do not achieve their peak milk yield in the first few weeks post-calving, and so optimising dry matter intake rather than maximising the energy consumed should not cause problems.

'''High proportions of starches and sugars in the diet''': Dairy farmers often include large amounts of rapidly fermentable carbohydrates in the diet in order to meet energy requirements and maintain body condition score and milk production. These carbohydrates can take the form of grain, concentrates or maize silage. However, rapid fermentation leads to over-production of volatile fatty acids, and thus subacute rumenal acidosis. This actually makes digestion less effective, so the cattle do not benefit as much as the should do from the extra sources of metabolisable energy. A vicious cycle can ensue of poorer performance and supplementary feeding of concentrates.

 

'''Sorting of long fibre''': When the fibre in a total mixed ration is longer than 10cm, cows tend to sift through the diet and consume smaller, more palatable particles and the pieces of forage too small to sort out. This alters the concentrate-to-forage dry matter ratio which is actually eaten by the cow (even if it is correct in the diet presented to the animals), which increases the risk of developing subacute rumenal acidosis. There is the additional problem in this situation that animals lower down the hierarchy, such as heifers, will eat the remainder of the sorted diet and thus not receive tbe energy they require. Both groups of animals are then likely to be in negative energy balance, but for different reasons.

'''Slug-feeding of concentrates in the milking parlour''': If relatively large quantities of concentrates are supplied over a short period of time, rapid fermentation occurs and the rumen pH fluctuates more widely than if a less carbohydrate-rich diet is consumed more steadily. The pH also remains low for longer. ubstitution effects may also take place as the consumption of more concentrate can lower the subsequent forage intake. These factors combined can lead to the development of SARA.  

'''Slug-feeding of concentrates in the milking parlour''': If relatively large quantities of concentrates are supplied over a short period of time, rapid fermentation occurs and the rumen pH fluctuates more widely than if a less carbohydrate-rich diet is consumed more steadily. The pH also remains low for longer. ubstitution effects may also take place as the consumption of more concentrate can lower the subsequent forage intake. These factors combined can lead to the development of SARA.  

'''Food deprivation and irregular feeding''': Food should always be available to a dairy cow, and it is recommended that slight over-feeding, with 5-10% of the ration left over at the time of the next feed, can be implemented to achieve this. If a cow goes without food for any period of time, the population of microbes in the rumen can be disrupted and the animal is likely to gorge when next presented with the ration. Both of these factors encourage subacute rumenal acidosis.

'''Inadequate dry cow diet''': the diet fed immediately before calving (the transitional cow diet) should be formulated to stimulate the development of rumen papillae and the acquisition of an appropriate colony of microflora. This should ensure that cattle can adequately ferment the post-calving diet and effectively absorb the nutrients it provides. Therefore, if the dry cow diet does not encourage these processes, volatile fatty acids can accumulate in the rumen when the lactation diet is introduced, leading to SARA. This is a particularly common problem, since dry cows are "non-milkers" and so tend to be the forgotten members of a herd.

 

'''Post-calving nutrition''': The "transitional period" for a dairy cow is defined as the period four weeks pre-calving, to four weeks-post calving. Often, farmers will provide a transition diet before calving, but introduce the lactating cow diet immediately afterwards. In the first four weeks after calving, the rumen cannot properly handle diets that are dense in energy: the ration fed in this period ideally should contain 10% more energy than the transition diet fed before calving. the rationale to this is that dry matter intake will be increased, and will then remain at high levels throughout lactation. Animals do not achieve their peak milk yield in the first few weeks post-calving, and so optimising dry matter intake rather than maximising the energy consumed should not cause problems.

'''Poor cow comfort''': The optimum daily routine of a dairy cow includes 12-14 hours lying down and 10 hours of rumination. If cow comfort is poor, the time spent performing these activities will be reduced, and less saliva will be produced to buffer the pH of the rumen.

'''Poor cow comfort''': The optimum daily routine of a dairy cow includes 12-14 hours lying down and 10 hours of rumination. If cow comfort is poor, the time spent performing these activities will be reduced, and less saliva will be produced to buffer the pH of the rumen.