Investigating the Effects of Trace Mineral

Chelate on Egg Quality for Late-Cycle Laying Hens 

Poor egg quality is a major concern for egg producers and the total number of uncollectable eggs is thought to be the largest problem associated with egg shell quality.1 Calcium metabolism and shell formation is dependant upon enzyme systems, and various trace minerals are required as co-enzymes in these enzyme systems.

Zinc-dependant carbonic anhydrase is required for the formation of carbonate ions from carbon dioxide and water. Carbonate ions are required in the shell gland fluid to form calcium carbonate, which is required for eggshell formation.2  Zinc is also required for the synthesis of keratin, which is the primary protein of the shell membranes. 3

If trace minerals in layer diets were more readily absorbed (ie. more bioavailable), this may improve eggshell quality.4 Mineral chelates may greatly enhance the absorption of a trace mineral by preventing its conversion to an insoluble form in the intestinal tract.5

To investigate the effect of a mineral chelate on eggshell quality, 360  White Leghorn (Babcock B 300) late cycle (55 weeks of age) laying hens housed in 60 cages were fed either a control diet or a diet supplemented with Bioplex Poultry® (BP). BP is a blend of mineral chelates for poultry and is manufactured by Alltech.

Isocaloric and isonitrogenous diets (Table 1) were formulated for two periods of production. Each cage was randomly assigned one of five treatments: control (C), BP 55 weeks (BP55), BP 59 weeks (BP59), BP 63 weeks (BP63) and BP 67 weeks (BP67) of age. The weeks represented for each treatment indicate the timing of introduction of the BP® to the diet.

Feed consumption, body weights and hen-day production were measured every 28-d and egg quality data (specific gravity, egg weight and albumen height) was measured every 14-d.

Calcium balance  was determined for the hens at 75 weeks of age using 30 cages of hens. The analyzed calcium content of the control diet was 4.02 per cent and the analyzed value of the BP®-supplemented diet was 4.19 per cent.

One-way analysis of variance was completed in a completely randomized design with dietary treatment as the main factor. Response variables were subjected to analysis of variance using the Proc Mixed Procedure of the Statistical Analysis Systems Inc. For repeated measures analysis, the factor of age was added. If significant (P<0.05) main effects or interactions were found, the tukey option was used to compare differences among the least square means.

Results of Incorporating Mineral Chelates
BP® was found to have no effect (P>0.05) on hen-day production (Table 2), egg specific gravity (Table 3), egg weight (Table 3), or albumen height (Table 3) or per cent egg shell (Figure 1). Initial specific gravity of the eggs at 55 weeks of age was comparable to production objectives for this strain of birds. The decrease (P<0.05) in specific gravity observed as the birds aged was expected.
However, the grams of calcium retained (Figure 2) by the bird at 75 weeks of age was affected (P<0.05) by BP® supplementation. Birds fed the diet supplemented with BP® at 55, 59 and 63 weeks of age retained more calcium then those fed the control.

Each dietary treatment was able to maintain a positive calcium balance (Figure 2) at 75 weeks of age.

However, birds supplemented with BP® at 55, 59, and 63 weeks of age maintained a higher (P<0.05) calcium balance than the control diet. Supplementing the diet with BP® after 63 weeks of age did not improve (P>0.05) calcium balance.

Production expectations for Babcock B 300 hens predict a specific gravity value of 1.077 at 80 weeks of age. Although there were no improvements observed in eggshell quality, improvements in calcium balance may have been beneficial for later eggshell quality if the length of the current trial was extended beyond 75 weeks of age.

Medullary bone acts as a labile source of calcium during eggshell formation. The higher calcium retention and balance values observed at 75 weeks of age for the birds supplemented with Bioplex Poultry® at 55, 59, and 63 weeks of age compared to the control diet may suggest that the Bioplex Poultry® could have improved calcium metabolism placing less of a demand on the medullary bone. Since birds at the end of their laying cycle often suffer bone breakage during catching and removal from battery cages and during transportation, an improvement in bone strength may enable the birds to withstand trauma incurred at the end of their laying cycle.6 Further research is required to evaluate the effect of Bioplex Poultry® on bone characteristics of laying hens, especially during the latter stages of their laying cycle.

References:

1 Roland, D.A., Sr. 1988. Research note: egg shell problems: estimates of incidence and economic impact. Poultry Sci. 67: 1801-1803.
2 Austic, R.E., and Nesheim, M.C. 1990. Poultry Production. 13th ed. Lea & Febiger, Philadelphia, PA.
3 Siske, V., Zeman, L., and Klecker, D. 2000. The egg shell: a case study in improving quality by altering mineral metabolism -naturally. Mendel University of Agriculture and Forestry. Brno, Czech Republic.
4 Gomez-Basauri, J. 1997. Eggshell quality and economic losses: The potential for improvement with dietary trace mineral proteinates. In Biotechnology in the Feed Industry. Proceedings of Alltech’s 13th Annual Symposium, eds. T.P. Lyons and K.A. Jacques, Nottingham University Press, Loughborough, Leics, UK. pp. 381-388.
5 Scott, M.L., Nesheim, M.C., and Young, R.J. 1982. Nutrition of the Chicken. 3rd ed. ML Scott and Associates, Cornell University, New York, USA.
6 Knowles, T.G., and Wilkins, L.J. 1998. The problems of broken bones during handling of laying hens – a review. Poultry Sci. 77: 1798-1802.