Bone metabolism in poultry - Doug Korver

Topic: Egg Quality
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September 18, 2018

Yes, I would like to discuss about this topic in poultry.

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September 18, 2018

I totally agree with the comments from Dr. Doug Korver. We need to maximize the reserve of calcium by strong structural bone during the rearing period and later on during all the lay period but especially during the start of lay period, trying to maximize the use of calcium from feed in order to protect the reserves of structural bone as long as possible. Recently I published an article in Avinews magazine about the same topic.

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September 18, 2018
Do you agree to increase the Ca/pnpP-ratio with advancing age of the laying hen?
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September 24, 2018

Hello gerard huyghebaert :

Yes, I agree with this approach, but I think that we need to re-evaluate the absolute levels of Ca and aP that we feed to layers. We recently completed a long-term study (to 74 weeks of age), and found that our negative control diet, with a moderate reduction in ca and aP from the management guide recommendations, actually had greater structural bone reserves at the end of the study than the positive control diet. Also, we typically do not see a phytase response (multiple studies, multiple products) when our negative control diets have the Ca and aP reduced by the matrix value of the phytase. Phytases are effective when re further reduce the Ca and aP levels, so it is a matter of the PC diets providing well in excess of what the birds require. Richard Miles did some nice work in the past showing that excess aP in layer diets reduces shell quality, so as we look at an industry shifting to longer and longer production cycles, we will see more stress placed on the skeletal system and subsequently on shell quality. I think that for these reasons, we need to re-evaluate the recommended levels of Ca and aP in the diets of layers, to better address what the birds actually require, because of the consequences of excess Ca and aP, and to more effectively use phytase.

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Venugopal Sathyanarayan Venugopal Sathyanarayan
MVSc , PhD in poultry science. (specialized in breeding)
September 18, 2018

Yes, I do agree with Dr. Korver, the logic is convincing and calcium supply needs to be increased in older birds.

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September 19, 2018

I agree with Dr. Korver, calcium is one of essential nutrients in the diet of laying birds. Calcium is necessary for egg formation. Eggshell is made up of 97% calcium carbonate.

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Sayed Mohammad Mortazavi Sayed Mohammad Mortazavi
Doctor of veterinary medicine ,DVM,VPH,
September 19, 2018

Hello Mr. Dr Korver
Thank you for your lecture, Would you please explain, how we can maximize the bone calcium resource, especially during the rearing period? Although we know excessive calcium carbonate in the ration is harmful. I look forward to hearing from you.
Regards,
Sayed Mortazavi.

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September 24, 2018

Hello Sayed Mohammad Mortazavi :

There are several approaches that should be used. First, body weight management is critical. Birds that enter lay at too light a weight will necessarily have smaller frames, and therefore less calcium reserves. Body weight should be kept on target throughout the rearing phase, rather than trying to get the birds to gain a lot of weight close to the onset of lay - -this can result in birds that still have small frames, but have more body fat. If pullets are under weight at the desired age of photostimulation, it is better for long-term productivity to delay photostimulation until birds reach target weight. Feeding appropriate amounts of Ca and aP during the pullet phase is also critical. although the primary breeder management guide recommendations for these minerals are, in my opinion, higher than is necessary, the recommendations for pullets are generally fairly good. A pre-lay diet may be used, but only to prepare the bird for lay -- not as a last-ditch effort to add body weight. Once the flock starts to lay, the hens NEED additional Ca, and must be switched to a start-lay type diet. Excessive amounts of time on a pre-lay diet after the flock starts production will force the birds to mobilize excessive bone reserves early in lay. Good flock uniformity and management will ensure that the entire flock starts to lay at very close to the smae time, and dietary changes can be managed to reflect the needs of each individual bird in the flock as closely as possible.

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Zahed Abbasi Zahed Abbasi
VETRINARIAN
September 23, 2018

I agree because "all hens require a specific amount of nutrients to maintain production and skeletal structure. The skeleton and dietary requirements of hens are unique relative to the level of calcium consumed and the amount of bone that is constantly being built and resorbed".
Hence, rearing period is important to make a strong structural bone and management of sexual maturity to built a high medulary bone capacity, and managing feed preparation, distribution in the day, especially in laying period, is also important.

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Hiren Pancholi Hiren Pancholi
Graduation in commerce
September 23, 2018

Dr. Doug Korver,

Is there any role of Trace Minerals and Vitamins for skeletal formation in rearing period of Laying Birds and in the Old age birds?

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September 24, 2018

Hello Hiren Pancholi:

Certainly. Several trace minerals are essential in the formation of the organic matrix of bone, particularly during the rearing phase. Vitamin D activity is also extremely important in bone formation. As the hens progress through the laying cycle, structural bone can be mobilized, but is no longer formed. However, there is a daily turnover (mobilzation, formation) of medullary bone as long as the hens are in lay.

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September 25, 2018

Hello Hiren Pancholi :

Eggshell is mainly inorganic minerals (95%) and about 95% of these minerals are calcium carbonate crystals. Trace elements are also involved in the eggshell in minor values, while their roles also may be important for enzymes activity and shell gland mucosal homeostasis. the less than 5% organic proteins involved in the eggshell also may require trace minerals for their conformation and thus normal eggshell biomineralization.
Adding zinc oxide in normal and nano forms enhanced eggshell quality in aged hens. Also vit D supplementation enhances eggshell quality and important for calcium mobilization as Dr. Doug Korver mentioned, 50% of eggshell calcium is derived from feed, and other half from medullary bones. This may be due to the importance of vit D for the expression of intestinal and uterine calbindin protein, which is related to the ability of tissues to capture calcium, also vit D is important for mucosal innate immunity and homeostasis which may be affected by aging or stress as we experienced in our studies.

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Fred Hoerr
Fred Hoerr
DVM, PhD, Diplomate ACVP, ACPV
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