The strength of guinea fowl (Numida meleagris) egg shells

The relationship between thickness and snapping strength in egg shells

“…Petersen and Tyler (1966) have reported a similar finding for the guinea-fowl shell, but Brooks (i960) found that hardness in these shells, as in the domestic hen egg shells, increased towards the outside, although the gradient of hardness was not linear but decreased over the outer half of the shell thickness. Clearly this complicates the relationship between hardness and snapping strength and underlines the need for further work.…”

“…This finding may be of some taxonomic interest for already Petersen and Tyler (1966) have reported that the guinea fowl shell had stronger layers on the inside compared with the outside.…”

“…Of course, the two situations may be different because, with the domestic hen, different eggs have been used for each reading, but more probably the answer is that the range of T values for domestic hen egg shells is so relatively small that using T instead of T 2 does not distort the straight line sufficiently to give an obvious curve. Indeed, using a different method of breakage, Brooks (i960) found that T 2 gave as good a relationship with breaking load as did T. Recently, Petersen and Tyler (1966) reported on the strength versus thickness relationship for guinea fowl eggs and mentioned that a few eggs with very thick shells did not fit the straight line relationship too well. It is now clear that if S had been plotted against T 2 a much better straight line relationship would have been obtained.…”

“…In general it is agreed that, with a mixed batch of eggs, there is a significant correlation between the two factors but that variations in shell thickness only account for about half the variation in strength and hence there must be additional factors which affect the strength of the shell. However, as far as the author knows, apart from a little preliminary work by Petersen and Tyler (1966), no attempt has been made to measure the strength of pieces of shell from the same egg, namely, pieces where variations in other factors are at a minimum, after these pieces have been deliberately thinned by filing, or by some other process, and thus to seek a relationship between thickness and strength by using a new procedure. In addition, it was felt that this method might reveal whether or not different layers of the shell have different strengths.…”

Eggshell of the domestic guinea fowl

“…The relative shell mass at 14-1% (Table 1) is higher than in the domestic fowl (10%; Sauveur, 1988). The mean shell thickness (486 /mi) is also (45%) greater than in Downloaded by [New York University] at 18:53 18 February 2015 the domestic fowl egg (320 to 350 /ttn; Petersen and Tyler, 1967). The density of the mammillary knobs on the internal face of the shell is 275/mm 2 (Simons, 1971) against 200/mm 2 in the domestic fowl (Simons, 1971).…”