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2
*
Animal Sciences Department and
Department of Food Microbiology and Toxicology, University of Wisconsin-Madison, Madison, Wisconsin 53706
2To whom correspondence should be addressed at 260 Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison, Madison, WI 53706-1284. E-mail: mcook{at}facstaff.wisc.edu
Dietary conjugated linoleic acid (CLA) decreases yolk 18:1(n-9),
induces chick embryonic mortality and alters egg quality. A study was
conducted to determine whether olive oil would prevent these adverse
effects of CLA. Hens (15 per treatment) were fed diets containing
0.5 g corn oil/100 g (CO), 0.5 g CLA/100 g (CLA), 0.5 g
corn oil plus 10 g olive oil/100 g (CO + OO) or 0.5 g CLA
plus 10 g olive oil/100 g (CLA + OO). After 74 d of feeding,
hens were placed on CO for 10 d. Hens were artificially
inseminated weekly. For hatchability studies, fertile eggs were
collected daily, stored at 15°C for 24 h and then incubated.
After 6 d of feeding, embryonic mortality rates were 15, 100, 8
and 16% in the CO, CLA, CO + OO and CLA + OO groups, respectively.
When CLA-fed hens were fed the CO diet, hatchability improved to
that of the CO group within 7 d. For fatty acid analysis, three
eggs were obtained at the 7 d of feeding. Relative CLA levels of
yolk from CO-, CLA-, CO + OO and CLA + OOfed hens were 0.11 ± 0.01, 1.91 ± 0.16, 0.08 ± 0.04 and 0.69 ± 0.07 g/100
g fatty acids, respectively. The ratios of 16:0/16:1(n-7) and
18:0/18:1(n-9) of yolk from CLA-fed hens were
1- and
1.5-fold
greater, respectively, compared with those fed CO. OO prevented
CLA-induced increases in 16:0 and 18:0 and the decrease in
18:1(n-9) in yolk. Fertile eggs were stored at 4°C for 2 or 10 wk and
analyzed for pH or mineral levels. Dietary CLA caused abnormal pH
changes of albumen and yolk when eggs were stored at 4°C. The pH of
yolk and albumen from CO-fed hens after 10 wk of storage was 6.12
± 0.12 and 9.06 ± 0.03, respectively, versus 7.89 ± 0.25 and 8.32 ± 0.16, respectively, in eggs from CLA-fed
hens. OO prevented CLA-induced abnormal changes in the pH of
albumen and yolks. Eggs from CLA-fed hens had greater iron, calcium
and zinc concentrations and lower magnesium, sodium and chloride
concentrations in albumen relative to those from hens fed CO. OO
prevented CLA-induced mineral exchange between yolk and albumen,
presumably by reducing the yolk saturated fatty acids, which are
believed to disrupt the vitelline membrane during cold storage. This
study suggests that the adverse effects of CLA may be due to the
increased level of saturated fatty acids. However, because the addition
of olive oil also lowered egg CLA content, the direct role of egg CLA
on egg hatchability and quality cannot be ruled out.
KEY WORDS: chickens conjugated linoleic acid conjugated linoleic acid egg quality embryonic mortality
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