This experiment was conducted to study the effects of zinc supplemental level on performance and eggshell quality of laying hens. Two hundred and eighty eight Hy-Line laying hens aged 52 weeks were randomly divided into 4 groups with 6 replicates per group and 12 hens per replicate. During the first 7 weeks (pre-feeding period), all hens were fed a corn-soybean basal diet containing 24.10 mg/kg zinc. Experimental diets were introduced at the end of week 7 and were fed for a total of 4 weeks, and these diets consisted of the basal diet supplemented with 0, 35.00, 70.00, 115.00 mg/kg zinc. The results showed as follows: 1) the supplementation of zinc did not significantly affect the egg production rate, average daily feed intake, average egg weight and the ratio of feed to egg (P>0.05); 2) the supplementation of zinc significantly increased eggshell weight (P<0.05), eggshell index (P<0.01), eggshell thickness (P<0.01) and eggshell percentage (P<0.05), and the effects of 70.00 and 115.00 mg/kg groups were better; 3) the supplementation of zinc significantly increased carbonic anhydrase activity both in blood and eggshell gland (P<0.01), and crystal microstructure of eggshell was improved, the bonding among crystals was more tightened, the size of crystals was more even and almost all the crystals showed vertical growth to the cuticle. In conclusion, the supplementation of zinc in the diet for late laying hens does not significantly affect their performance, but tends to increase the eggshell quality by improving carbonic anhydrase activity of blood and eggshell gland, and crystal microstructure of eggshell. The optimal level of zinc is 70.00 to 104.00 mg/kg in the present study.
ZHANG Yanan
,
WU Shugeng
,
ZHANG Haijun
,
YUE Hongyuan
,
QI Guanghai
. Effects of Zinc Supplemental Level on Performance and Eggshell Quality of Laying Hens[J]. Chinese Journal of Animal Nutrition, 2013
, 25(5)
: 1093
-1098
.
DOI: 10.3969/j.issn.1006-267x.2013.05.026
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