The degradation of egg shell quality from birds over 50 weeks of age leads to loss of collected eggs and an increase in downgraded eggs.
This phenomenon is generally attributed to the reduced capacity for absorption and mobilization of body calcium in the aged birds. A second limiting factor is involved: the advanced age of the animals causes a reduction in the capacity to synthesize components of the egg’s internal membrane. This experimental study, conducted as part of a thesis, compares the influence of a source of calcium carbonate (oyster shell at 3 grams/layer/day) with calcium pidolate (incorporated at 300 ppm). The treatments are repeated four times on 12 Lohmann White hens (55 weeks old): egg production, egg shell quality and feed conversion ratio (FCR) were studied over 8 weeks of production. In the calcium pidolate group, production was significantly increased by 5% (p <0.05) and the number of downgraded eggs due to shell quality problems was reduced by 25% (p <0.05). The egg weight was also improved. The combination of these improvements led to a decrease in FCR of 10%.
The incorporation of calcium pidolate, which is involved in calcium metabolism and synthesis of components of the egg shell internal membrane, allows maintenance of egg shell quality and higher production parameters when compared with the addition of oyster shell- a CaCO3 source considered to be more bioavailable than limestone.
From 50 weeks of age, reductions in eggshell quality cause a loss in collected eggs and an increase in downgraded eggs (less valued). This phenomenon is generally attributed to a dysfunction of calcium metabolism (reduced capacity for absorption and mobilization of body calcium). A second limiting factor may be involved: the advanced age of the animals causes a reduction in the capacity of synthesis of components of the egg’s internal membrane.
This experimental study, conducted as part of a thesis, at the Research Department on Animal Production of the University of Santiago in Chile, compares the influence of a soluble source of calcium carbonate (oyster shell at 3 grams/layer/day) with calcium pidolate (incorporated at 300 ppm), in the feed of layers between 56 and 63 weeks old. This work focused on quantitative parameters (weekly egg production, egg weight, feed conversion ratio (kg of feed / kg of eggs) and qualitative (% downgraded eggs, % downgraded eggs due to egg shell problems).
56 week old layer birds (Lohmann® white) were used in the trials. There were two dietary treatments and each treatment had 48 layers (12 layers x 4 replicates). The basal diet was formulated according to Lohmann® white specification but without phytase. Calcium carbonate (limestone) was incorporated in the basal diet at 60% grit and 40% powder. Treatment 1 consisted of addition to the basal diet of 300 g/ton of calcium pidolate (PIDOLIN® P Ca)-an organic calcium salt patented by Dietaxion. Treatment 2 consisted of birds on control diet and given additional 3 g/hen/day of oyster shells with diameter above 2mm. Both diets had a minimum calcium level of 4%.
The layer birds were housed in a naturally ventilated shed in cages of 4 hens each. The feed was available ad libitum. Daily egg collection was at 1pm. The egg count included total eggs collected, broken eggs, soft eggs, dirty eggs, blood stained eggs and small eggs. All eggs collected on Fridays were weighed.
The study compared the average of production parameters over a period of 8 weeks. The equality of variances of the data was checked with the F-TEST and the averages using a Student T-test.
Table 1 below shows that calcium pidolate incorporation provokes a significant increase on egg production of 4 points (p < 0.05) during the total period (an increase of more than 5 % production/hen/week) in comparison with the results of the group, which received oyster shell. The improvement is partly due to the direct effect of calcium pidolate and could also be attributed to the dilution effect on the diet due to the incorporation of oyster shell at 2.5%.
The percentage of total downgraded eggs of calcium pidolate group was different from the oyster shell group (p=0.05). It appears that this parameter only differs in the second phase of treatment (from week 60). The incidence of downgraded eggs represents the sum of broken and soft-shelled eggs divided by the total number of eggs collected. The type of defect is not identified. The calcium pidolate group had a lower proportion of eggs downgraded due to shell quality. There is a difference of 4 points compared with oyster shell, which relates to 25% lower (p < 0.05). Average eggs weight shows a positive effect of the use of calcium pidolate: higher effect on average of 4% compared to oyster shell (p = 0.08). FCR of calcium Pidolate group is significantly improved by 10% compared to oyster shell group (p = 0.05).
The production is enhanced significantly but egg weight was not significantly higher for the calcium pidolate group, as compared with the oyster shell group.
Lower incidence of broken and soft eggs was found in the calcium pidolate group and feed conversion ratio was also significantly improved.
This study shows that calcium pidolate use is clearly preferable to an addition of oyster shell for improving production parameters and shell quality.