Hello hello! Welcome to the Research Digest #5.
Today, as I was scanning through the Advance Articles on Poultry Science, a paper immediately caught my eye --- it is titled 'Calcium affects sternal mass by effects on osteoclast differentiation and function in meat ducks fed low nutrient density diets'
Why? Because first of all, it is a DUCK paper! Hooray! Also, among the authors, there are two of my favorite people --- Prof. Keying Zhang (my dear mom) and Dr. Todd Applegate (my dear Ph.D. advisor). Naturally, it is really really hard to miss a paper like this. 😄
And it is a really interesting paper! I can't wait to share it with you.
This is a work from my mom's lab at Sichuan Agricultural University, China, in collaboration with Dr. Applegate. The paper just came out yesterday (June 25) on Poultry Science as an Advance Article.
Today's super fast growth of modern meat ducks can lead to inadequate bone mineralization of the sternum (breastbone) because bone mineralization doesn't occur until later in life. This may result in several health issues in the field such as pulmonary diseases or ascites.
High nutrient density of today's feed is one reason that leads to this fast growth (besides genetic selection); meanwhile, different dietary Ca has been shown to impact bone mineral contents & modulate osteoblast/osteoclast activity in poultry in earlier studies.
So...perhaps feeding a low-nutrient-density diet combined with optimal Ca can help promote sternal bone quality in Pekin ducks (by slowing down weight gain, promote bone mineralization, and modify osteoblast/osteoclast activity)?
This is exactly the question asked by the authors.
What was done?
The experiment design was quite straightforward --- below is an illustration of what was done.
(A LOT of measurements were taken in this study at 4 different time points )
What was found?
- Growth Performance
Yes, LND indeed slowed down growth (comparison was made between PC and LND+0.9% Ca because of similar Ca%). Among the LND groups, higher Ca% improved performance during the finisher period (35-56 d).
- Sternal Bone Characteristics
Compared with PC, LND+0.9% Ca increased the Sternal bone mass, Trabecular number, Trabecular bone volume/tissue volume, and Sternal Ca content (as shown below by the "*" sign)
✅ So, slowing down growth combined with higher Ca is indeed good for sternal bone.
Among the LND groups, ≥ 0.7% Ca increased the mineral content (Ca and P), bone density, trabecular bone volume/tissue volume, and trabecular number at day 49 (as shown below by the superscripts)
✅ So, 0.5% Ca is too low. 0.7 and 0.9% are good, not necessary to go any higher.
- Osteocytes...Osteoblasts...Osteoclasts...Okay...I will try not to confuse you. I know I was when I first started reading these results. 😝
So...Osteoblasts are bone cells that mature into osteocytes; Osteocytes are mature, permanent bone cells; Osteoclasts are cells that resorb osteocytes.
Basically, in this case, we may consider that osteocyte and osteoblasts are good, osteoclasts are bad (not really though, to be precise - osteoclasts are important in regulating skeletal homeostasis).
In this study, when compared to PC, ducks fed LND+0.7% Ca had significantly:
- Increased Osteocyte-specific markers (DMP1 and Sclerostin), meaning more osteocytes. Good ✅
- Reduced Osteoclast Number, meaning less bone resorption. Good ✅
- Decreased Cathepsin K expression, which is an osteoclast-specific marker, again meaning less osteoclast. Good ✅
- Decreased Serum TRAP (tartrate-resistant acid phosphatase, a marker for bone resorption), again meaning less bone resorption. Good ✅
- Increased Osteoprotegerin (OPG) expression, meaning suppressed osteoclast production. Good ✅ (Because "OPG acts as a decoy receptor by blocking the interaction of RANKL with its functional receptor RANK, an increase in OPG production by osteoblast will suppress osteoblast-induced osteoclast development (Yamamoto et al., 2006)")
Yeah, All good!
(These are some key results...there are more in the paper if you are interested)
So going back to the initial question, we can see that all the data point to the same story that LND diet combined with 0.7% or 0.9% Ca can be used to promote sternal bone quality in meat ducks by slowing down growth, improving bone mineralization, and inhibiting osteoclast activities.
Take home message
Low-Nutrient-Density diet with 0.7% or 0.9% Ca is good for your ducks' bones!
(Although growth will be slowed down compared to the typical High-nutrient-density diet).
So faster growth or better bones? It is a trade-off and it really depends on what the market and consumers want (In the Southwest region of China where the research lab is located, consumers strongly prefer slow-growing ducks and hard sternum for cuisine like the famous "old duck soup")
Full article access 👇
Related Reading 👇
1. Another set of results from likely the same trial suggest that LND diets with ≥ 0.7 % Ca decreased bone turnover, which subsequently increased tibia quality for 35-d-old meat ducks.
📍Effect of graded calcium supplementation in low-nutrient density feed on tibia composition and bone turnover in meat ducks
2. Earlier work done by the same group found that higher vitamin levels improved growth performance and sternum calcification in meat ducks.
📍Effects of commercial premix vitamin level on sternum growth, calcification and carcass traits in meat duck
3. Another work done by the same group showed that ossification of the sternum of the meat duck is incomplete during the seven-week growth period, and rapid mineralization occurs from 42-49 days of age.
Zhang, H. Y., Q. F. Zeng., S. P. Bai., J. P. Wang., X. M. Ding., Y. Xuan., Z. W. Su., T. J. Applegate., and K. Y. Zhang. 2019. Calcium affects sternal mass by effects on osteoclast differentiation and function in meat ducks fed low nutrient density diets. Poultry Science. 0:1-14
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