Hey to all!
Hope this message finds you doing well. I'm writing to ask you about the correct time of blood sampling to recognize how DCAD diets work? As it is believed "nearly all cows will experience some degree of hypocalcemia at the onset of lactation (Goff, 2014)". So, when should we draw blood to assay this problem? How many percent of cows should have normal Ca concentration (> 8.5 mg/dl)? New data from Cornell University also show that more than 55% of cows are hypocalcemic on d 1 after calving even on DCAD diets. I could not find any answer to this question. Could you please advice me on this issue?
Regards,
Ehsan
Hi Ehsan,
The most reliable methods to ensure your DCAD adjustment is working is the measurement of urinary pH and calcium concentration. Urine pH should be acidic and calcium must have increased if the calcium recruitment has worked.
Also one important point to consider is that DCAD is to keep calcium recruitment system active and this system definitely has a limit, particularly after parturition. Therefore, seeing transient subclinical hypocalcemia for a few days after parturition (at least for the first few hours) is no surprise; until the calcium homeostasis system catches up with the increased demand (that would also depend on the age of the cows too). Considering the above, with a DCAD balanced diet, I would expect that a cow is capable of returning its serum calcium concentrations to normal range in 24-72 hours postpartum (again depending on multiple factors including the cow's age).
One interesting thing that I found working on about 15000 cattle is that you do not have to adjust DCAD to -100 to prevent hypocalcemia; and adjusting it at mildly negative values sufficed this purpose.
Hope the above helps you.
Dear Ebrahim,
Thanks for your comprehensive explanation. Yes, you are completely right and I'm aware of all what you said; but, I'm looking for an alarm level at the right time. For instance, having 30% hypocalcemic cows (Ca < 8.5 mg/dl) at d 2 after calving would be normal or not? What about 40% of cows? Is not there any alarm level for blood Ca as there is for NEFA or BHBA?
As for adjusting dietary DCAD, I completely agree with you, but we must make sure about DCAD numbers by urine pH samples. I meant, only looking at the DCAD number on ration software is not enough so that you might have negative DCAD (even more than -100) but urine pH is still fluctuating around 6.7. In this regard, as you may know, Cornell researchers are recommending to have urine pH of 5.5-6 for a perfect transition program!
Once again, thanks for your answer.
Ehsan
Hi Ehsan,
Hypocalcemia typically occurs within 72 hrs of calving so it would be useful to sample at least on the day of calving and day +3 in my opinion.
Hi Emily,
Day of calving is not a good option but I think 3 DIM would be great. What about the alarm level? DO you have any idea?
Ehsan
I meant how many percent of cows should have blood Ca less than 2mM to say we have hypocalcemia problem?
OK,
Lets talk evidence based and not based on personal opinions. Of top of my head , it takes about 7-10 days for the osteoclasts to be recruitted and start resorbing bone; and a 2-3 weeks of anionic salt treatment should suffice this purpose. The only obstacle would be activation of the hormonal system, to switch osteclastic activity plus calcium absorption mechanisms (from intestines and kidneys).
Considering that PTH, and 1,25 VitD (but not 2VitD) and other hormones have circadian rhythms, and once again "assuming" two cycles being enough for reasonable activation of the calcium recruitment after parturition, I would suggest measuring calcium 48-72 hours after parturition.
However, as you know the biology works on a bell-shaped curve and there will be slow and fast cows, but the average and 2 standard deviation (SD, or 95% CI) should fall into this time-frame if our assumption is correct.
I am strongly against inducing severe metabolic acidosis that leads to such low urine pH values (5.5-6). It is insane to think that hypocalcaemia is the only problem of the postparturient cattle, and induce such as severe acidosis. This could impact the 3D structure of most hormones and receptors that are NOT involved in calcium metabolism, but are a key factor in normal postpartum homeostasis. Sacrificing other systems to prevent hypocalcaemia is not recommendable, and regarding the fact that based on my observations on such a huge populations adjusting DCAD to just under-neutral resolved the hypocalcaemia issue in herds is further testimony to this.
Good luck with your endeavour!
Ebrahim,
Thanks a lot for your adding up. I just found an alarm level of 30% recommended by Dr. Oetzel. But, it is for the blood samples drawn on the calving day. Considering what you said and other papers, I think 48-72 h is great to take blood samples and if more than 30% of cows are hypocalcemic, we should re-look at our DCAD program. Let me know what you think.
Cheers,
Ehsan
Dear peers.
This is really a potential topic to debate and of practical importance also. For me the status can be monotored in the first 24 to 76 hours of parturations. But the homeostasis also depend on many factors like condition of animal pariety and also no of offsprings born. Depending on these there may be hypocalcemia in the first day itself.
To adress the issue, as per me blood analysis should be done for calcium at early hours post Parturation at definite interval . For instance at partum then 6h, 12h, 24h and 36 and 48h. Dcad diets cabn be provided in negative to initiate the calcium mobilisation prepartum
Looking forword for some new updates.
Regards
Partha
Dear Partha,
Your suggestion is the excellent practice, however very labour and money intensive if you wanna repeat it in a big farm as the ration changes. However, could be considered a best practice target.
Cheers,
Eb
Thank u sir..
In a well organised farm doing once or twicw will give us a representative picture. Which can be firmulated as a standard for all. And takibg the risk into consideration, if possible in small farms we can analyse each animal and the status can be monitored in best possible way.
Regards
Partha
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