Given the importance of good hatching rates to the poultry industry in general I thought it would be pretty easy to find lots of more recent studies on the effect of turning on hatching rates than the ancient one mentioned in the Country Stock Journal article.
So I did a quick
Google Scholar search and found some articles right away, although I only got the abstracts.
Developmental patterns of O2 consumption, heart rate and O2 pulse in unturned eggs
"The effects of failure to turn eggs on the developmental patterns of oxygen consumption, heart rate and O2 pulse during the second half of incubation of individual chicken eggs were examined. The O2 of unturned eggs increased at a significantly lower rate than the control toward the end of prenatal incubation, and the plateau O2 between day 17 and 19 was significantly lower than the control. Lack of turning also resulted in significant changes in the developmental patterns of and O2 pulse. It is suggested that the effects of lack of egg-turning on the developmental patterns of ImageO2 may be attributable to lower embryonic growth rate in addition to impairment of gas exchange through the chorioallantoic gas exchanger. "
Adverse effect of failure to turn the avian egg on the embryo oxygen exchange.
"Fertile chicken eggs belonging to the same flock of hens were divided into two groups and incubated for 16 days. During incubation, group 1 eggs were turned twice a day and group 2 eggs were left unturned. Blood sampled from the allantoic vein or artery was analyzed for gas tensions (PO2 and PCO2), pH and Hct. These values were compared by unmpaired t-test for significance differences between the two groups. While the differences of PCO2 and pH were found insignificant, failure to turn the eggs caused a pronounced fall in the arterialized PO2 which was accompanied with an increase in Hct. In addition, the embryo weight was reduced in unturned eggs. Lack of turning retarded the absorption of albumen. The unabsorbed albumen interposed between the chorioallantoic membrane and inner shell membrane, impeding the blood oxygenation through the chorioallantois. Little change in PCO2 might be attributed to a large diffusive conductance of the chorioallantois for CO2. The present results suggest that the eggs must be turned periodically during incubation to prevent the distortion of normal oxygen exchange especially for the study of egg respiration."
Failure to turn eggs during incubation: effects on embryo weight, development of the chorioallantois and absorption of albumen.
"Turning eggs during incubation is essential for good hatchability. In the present paper additional effects on the development of the chorioallantois, absorption of albumen and growth of the embryo are recorded. The ability of an unturned egg to hatch was not affected by egg weight, egg shell porosity or water loss during incubation. The ability of the chorioallantois to spread around the inner surface of the inner shell membrane and the degree of absorption of the residual albumen affected the growth of the embryo and its ability to hatch. Unturned eggs hatched later than eggs which were turned throughout incubation."
A quick search of Google Scholar using different keywords will turn up lots. Generally if a something is economically important to an agricultural industry it will have been studied to death, and hatching rates are important to every aspect of producing poultry products economically. I would imagine that not turning also works a lot of the time, because chickens are so resilient, having been selected over human history to survive in so many different types of artificial environments over the years
.
