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Introduction
At the Institute of Animal Science (ICA), the evaluation of natural zeolites for the feeding of avian species began in the 1980s. The aim of this research was to evaluate and further study substances that could potentially be used as diluents for the concentration of nutrients in feed for broilers and laying hens, and thus reduce feed costs (Acosta et al. 2005). The work carried out on monogastrics (Lon-Wo et al. 1987, Castro 2014, and Llanes et al. 2022) considered the particle size provided by the mineral, commercially known as ZOAD, with ground particles less than 1 mm. The results achieved in laying hens suggested the use of this mineral between 1 and 10 % in diets (Berrios et al. 1983, Lon-Wo and Cárdenas 1996 and Lon-Wo et al. 2010), allowing improvements in productive behavior, health, and hygienic-sanitary conditions of agricultural facilities.
Recently, the Cuban Mining Company of the West has been micronizing natural zeolite with smaller particles (0.045 mm), to achieve higher quality and biosecurity for its use in different products. In animal production, the fact that it has a smaller particle size could modify the productive results (Pérez-Bonilla et al. 2011). The reduction of the particle size can facilitate the contact between nutrients and endogenous enzymes, thus improving the digestibility of nutrients (Parsons et al. 2006). However, fine particles often have a negative impact on the development of the gizzard and gastrointestinal tract, which could affect productive performance (González-Alvarado et al. 2007). Hence, the importance of evaluating zeolite in its new form.
In poultry farming, there is a tendency to keep laying hens for more than 100 weeks, given the cost of layer replacements and the technological flow that allows eggs to be kept on the market (Martínez et al. 2021). It is known that, at this stage, the egg tends to reach a larger size (Hervo et al. 2022) and with it, the quality of the shell decreases (Wistedt et al. 2019). Previous studies reported improvements in eggshell quality when feeding laying hens with natural zeolite (Roland et al. 1985 and Keshavarz and McCormick 1991). However, contradictory results are known in this regard, thus the present work aims to determine the effect of micronized zeolite as an additive for the production and egg quality in laying hens at 89 weeks old.
Materials and methods
The study was carried out in the poultry unit of the Institute of Animal Science. 240 White Leghorn L33 hens were used, distributed in four treatments, according to a completely randomized design, with 10 replications and six hens each, for 10 weeks.
The birds were housed in metal cages of 40 x 40 cm, with two nipples/cage for the ad libitum water supply and a linear feeder to supply the feed in a restricted manner, at a rate of 110 g/bird/day. The treatments consisted of adding zeolite to the control diet (corn-soybean) (table 1) in the following proportions: T1) control diet without addition of micronized zeolite, T2) control diet + 1 % addition of micronized zeolite, T3) control diet + 1.5 % addition of micronized zeolite and T4) control diet + 2 % addition of micronized zeolite. Micronized zeolite, with the commercial name ZEOBLANK, is processed in the Empresa Minera de Occidente with an average particle size of 6.68 µm, from the San Ignacio deposit, Mayabeque province, Cuba.
Table 1 Experimental control diet for feeding laying hens
| Ingredients, % | Control |
|---|---|
| Cornmeal | 62.30 |
| Soymeal (45 % PB) | 25.00 |
| Vegetable oil | 0.89 |
| Monocalcium phosphate | 1.16 |
| Calcium carbonate | 9.80 |
| Common salt | 0.30 |
| DL methionine | 0.12 |
| Choline | 0.10 |
| Vitamin and mineral premix1 | 0.30 |
| Crude protein | 15.99 |
| Metabolizable energy, MJ/kg of DM-1 | 11.50 |
| Crude fiber | 2.40 |
| Total calcium | 4.00 |
| Available phosphorus | 0.35 |
| Methionine + digestible cystine | 0.62 |
| Digestible lysine | 0.80 |
1Mineral premix per kg of feed: selenium (0.1 mg), iron (40 mg), copper (12 mg), zinc (120 mg), magnesium (100 mg), iodine (2.5 mg), and cobalt (0.75 mg), and Vitamin premix per kg of feed: vitamin A (10,000 IU), vitamin D3 (2,000 IU), vitamin E (10 mg), vitamin K3 (2 mg), vitamin B1 (thiamine, 1 mg), vitamin B2 (riboflavin, 5 mg), vitamin B6 (pyridoxine, 2 mg), vitamin B12 (15.4 mg), nicotinic acid (125 mg), calcium pantothenate (10 mg), folic acid (0.25 mg) and biotin (0.02 mg)
The evaluation of the effect of micronized zeolite on growth performance of laying hens was determined by the following indicators: final body weight, feed and mass conversion, number of eggs per bird and laying intensity. For egg quality, in the morning, 15 eggs per treatment were randomly selected at week 96 old. Using two automatic devices, Egg Force Reader and EggAnalyzer® (ORKA brand), the eggshell breaking strength, yolk color, egg weight, albumen height and Hauhg units were determined.
For statistical processing of the data, variance analysis was performed according to a completely randomized design for the indicators egg weight, feed conversion, mass conversion, breaking strength and albumen height. The comparison between the means was performed using the Duncan (1955) test. The theoretical assumptions of the analysis of variance, normality of errors by the Shapiro and Wilk test (1965) and homogeneity of variance by Levene (1960) were tested for the variables laying intensity, eggs per bird per week, yolk color, and Hauhg units. These variables did not meet these assumptions, thus a nonparametric simple classification analysis of variance by Kruskal and Wallis (1952) was performed, and the Conover test (1999) was applied for p<0.05. The statistical packages Infostat (Di Rienzo et al. 2012) and StatSoft (2003) were applied.
Results and Discussion
The addition of micronized zeolite in the diet did not modify the body weight of the hens, the feed conversion and the albumen height (table 2). The mass conversion was better with 2 % and is closely related to the increase in egg weight at this level, thus the hen used less feed to produce a kilogram of egg. Similar results were reported by Elsherbeni et al. (2024), when adding 20 g/kg of zeolite in the diet for Silver Montazah hens.
Table 2 Effect on productive and egg quality in 89-week-old laying hens with the addition of micronized zeolite to the diet
| Productive indicators | Micronized Zeolite, % | SE ± | p-value | |||
|---|---|---|---|---|---|---|
| 0 | 1 | 1.5 | 2 | |||
| Initial body weight, g/bird | 1714 | 1719 | 1731 | 1711 | 13.04 | 0.7288 |
| Final body weight, g/bird | 1777 | 1785 | 1792 | 1789 | 11.57 | 0.7963 |
| Feed conversion, kg/kg | 1.35 | 1.36 | 1.33 | 1.26 | 0.03 | 0.0874 |
| Mass conversion, kg/kg | 1.86a | 1.89a | 1.84a | 1.70b | 0.04 | 0.0223 |
| Egg weight, g | 66.89a | 67.15a | 68.56ab | 68.95b | 0.57 | 0.0343 |
| Breaking strength, N* | 34.26a | 37.99b | 38.78b | 37.92b | 0.86 | 0.0022 |
| Albumen height, mm | 5.36 | 5.47 | 5.69 | 5.61 | 0.19 | 0.6165 |
a,bDifferent letters in the row differ for p≤0.05 *Newton
Previous studies have shown that Cuban zeolite is capable of increasing the efficiency of nutrient utilization (Berrios et al. 1983, Lon Wo et al. 1987 and Acosta et al. 2005). According to Macháček et al. (2010), this improvement can be attributed to zeolite due to its positive effect on the intestinal microflora and the digestion mechanism (Prasai et al. 2016). This is supported by the properties of this mineral, which participates in biochemical processes that include high cation exchange capacity, absorption, catalysis and rehydration-dehydration processes. The works of Emam et al. (2019) and Elsherbeni et al. (2024) also reported improved egg weight and mass conversion with the inclusion of zeolite in the diet.
The breaking strength of the egg (table 2), regardless of the level of zeolite used, increased by 1.13 times compared to the control. In this regard, Roland et al. (1985) stated that the beneficial effect of zeolite on eggshell quality corresponds to the high affinity with calcium and ion exchange capacity. Similarly, Watkins and Southern (1991) support that it may be associated with the content of elements such as silicon (Si), aluminum (Al), and sodium (Na) in the zeolite, which intervene in calcium metabolism. In a recent work, Yglesia et al. (2022) indicated that the micronized zeolite used in this study is of the calcium-sodium type, with a Si02/Al203 molar ratio ranging between 6.0 and 8.0 %, a characteristic aspect of these silica-rich minerals with a cation exchange capacity of 126.31 meq/100 g. These characteristics could favor calcium absorption in hens, an aspect that should be further investigated in subsequent studies due to its importance in egg quality and production.
The laying intensity, eggs per bird per week, yolk color, and Haugh units (table 3) were not modified with the addition of micronized zeolite. However, with 2 % of this mineral, a numerical increase was found in the laying intensity and the number of eggs per bird per week (5.9 % compared to the control). Similarly, Amad (2021) did not find modifications in these indicators when using natural zeolite at levels of 0.5 and 1 %. According to Vieira et al. (2023), the contradictions in the results obtained when using zeolite in the diet of laying hens are related to some factors such as the type and origin of the mineral, breed, age, technological level in the breeding systems, among others. According to Kermanshahi et al. (2011), the expected effect of zeolite in animal experiments may vary, due to the source, concentration, particle size, aluminum and silicon content in the zeolite, as well as the calcium and phosphorus content in the diet.
Table 3 Effect on laying intensity, eggs per bird, Haugh units and egg yolk color of 89-week-old laying hens with the addition of micronized zeolite in the diet
| Productive indicators | Micronized Zeolite, % | p-value | |||
|---|---|---|---|---|---|
| 0 | 1 | 1.5 | 2 | ||
| Laying intensity, % | 19.20 (82.10) SD =8.39 | 15.45 (80.90) SD =4.14 | 19.10 (82.74) SD =4.49 | 28,25 (87.26) SD =4.36 | 0.0881 |
| Eggs/bird/week, u | 19,20 (5.75) SD =0.59 | 15.45 (5.66) SD =0.29 | 19.10 (5.79) SD =0.31 | 28.25 (6.11) SD =0.31 | 0.0881 |
| Yolk color | 36.50 (3.53) SD =0.52 | 24.50 (3.13) SD =0.35 | 34.50 (3.47) SD =0.52 | 26.50 (3.20) SD =0.41 | 0.0533 |
| Haugh units | 26.67 (73.92) SD =8.50 | 28.20 (73.93) SD =5.19 | 33.00 (75.13) SD =4.21 | 34.13 (75.37) SD =4.41 | 0.5850 |
() Means of original data without transformation SD: desviación estándar
Conclusions
It is concluded that the micronized zeolite did not affect animal performance, thus it is suggested to use 2 % micronized zeolite as an additive in the diet of 89-week-old laying hens, allowing for higher egg weight and better mass conversion. It is necessary to delve deeper into aspects related to the internal and external egg quality, as well as blood biochemistry and nutrient digestibility, thus that the results can be confirmed and the possible mechanisms of action established.
