The NDS program has various methods of evaluating the risk of rumen acidosis. The end game is an acidosis risk index calculation and time per day below rumen pH 5.8 as influenced by peNDF, rumen degradable starch, DMI, inclusion of rumen buffer, etc. Recently I have been focusing on the index and find that ingredients in the recipe that are classified as “buffers” have a strong influence on the calculations. My ah ha moment came when looking at a very low cow diet that was about 70% forage, high peNDF, only 24% starch and the risk of acidosis was very high! This diet had 0.0 bicarb and that drove the calcs toward high risk for SARA. Not really believing we had SARA in this pen I inquired to the owner about free choice bicarb consumption. To our surprise it was very high…0.90 ppcpd!
This takes me to my questions. How much bicarb do you typically include in diets and do you also offer free choice bicarb and/or salt? Why do we offer free choice bicarb and salt on some farm and not on others? Does it make a difference or is it because it makes everyone feel better knowing a cow can choose, if she wants, to lick at the salt/bicarb?
I did not comment on the question you had about the NDS acidosis level since Buzz had done a good job doing that and it was complete. Not sure what cows are looking for is it DCAD and sodium or “buffering” which may lead to many questions if that occurs with the amounts of bicarb we feed in cows. Many users of NDS are abusing the equation and indexes by changing the classification of many products that might be “alkalizers” in acid base situations and calling them rumen buffers. Looking at the inputs to the equation helps to understand what the responses that might be seen are and then explainable. Buffering or DCAD or maybe little of both?
Since I scrubbed off my C&D tattoo and sold all my stock in rations that I work on the sodium needs to be above the chloride, and would like to have the chloride as low as possible( .40%). Have started minimizing the salt and using KCL so can get K as high as needed with minimal DCAD Plus. Buffer levels either SQ810 (which has higher sodium-but is not as white and pretty as bicarb) or bicarb at least at .35 to .5. Sodium in some rations as high as .55%. DCAD at 30 to 40 if we can get them that high. Bigger herds looking for any $ saving are using some sodium bentonite. For some binding and extra sodium. Feeding little more salt or sodium and chloride level if herd is talking about dirt eating and urine/floor water drinking.
Free choice leaving SQ810 or even SQ/bentonite out and salt block on fresh and high pens only. Fill sodium source twice a week. Headache to take up feed bunk space and clean around. Lactating cows probably don’t need much more chloride?
If a cow is licking dirt or urine could she be lacking potassium?
If you free choice sodium bicarb, I think cows go after it more often then not just because its available because feed isn’t available to them??
I guess I’m ambivalent about free-choice buffer or salt, more so the former. I think someone, years ago, suggested putting out bicarb as an alert if cows started consuming a lot maybe the ration changed whereby cows were dealing with a bit of SARA. I’m not endorsing that idea. As in Dr Fry’s post, cows were consuming 0.90 lb phpd while presumably consuming a low risk diet. I think there might be some risk of cows consuming that much freechoice – knowing that’s the mean phpd consumption – some individuals might actually have consumed quite a bit more – and maybe in a short period of time. Higher Na content in rumen would increase osmotic pressure (as well as rumen alkalinity) and outflow of liquid potentially causing some downstream issues with abomasal pH (just conjecture). So my bottom line in general is to put the amount of buffer in the diet you think you need and don’t free choice. I’ve gone as high as 0.75-0.80 lb phpd of bicarb or S-carb, especially in summer, maybe as much to drive DCAD as for moderating rumen pH.