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Nutrition of layer hens and its impact on egg quality

Escrito por: FEDNA
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Conteúdo disponível em: Español (Spanish)

When it comes to medium-sized layers, the key nutritional factors to consider are Met + Cys levels, ALA (linoleic acid), added fat, and feed energy content. When egg size is a priority, it’s best to increase Met + Cys in the starter feed by 2-3% in relation to that indicated in Table 1. An increase in Met (sulfurized AA) to increase egg size must be accompanied by an increase in the rest of the essential AAs.

For practical purposes, the factor that most influences the size of the egg is the weight of the chicken at the end of rearing. Pérez-Bonilla et al. showed that for every 100 g of extra live weight, egg weight increased by 1.0-1.1 g.

In Spain, XL eggs (> 73g) are still undervalued, so there is interest in increasing egg size in the initial stages of lay.
Table 1.- Nutritional recommendations for layers in battery cages.
1. Nutritional strategy to prepare the bird for long laying cycles. In the traditional system, laying starts with the next feed. 2. It could be convenient to use crumbs to boost consumption. 3. Estimated consumptions of 108 g at the beginning and 115 g at the end of the phase. In case of lower intakes, it is recommended to proportionally increase the level of amino acids and minerals. 4.Includes the added fat in raw materials such as whole bean, fatty germs and sunflower seeds. 5.Use 60-70% coarse limestone (≥ 3 mm) to facilitate the fluidity of the feed and improve the digestibility of Ca and the quality of the shell. 6.The total Ca can be reduced by 0.08%, the P disp. by 0.15% and the P dig. 0.12% in the case of using new generation phytases. 7.Reduce 10% in case of problems of wet stool. Raise levels 10-15% in hot situations. Use bicarbonate if necessary to reduce Cl- and meet the minimum Na. 8.Reduce the maximum to 0.85% (if possible) in case of wet stool. 9. Maximum levels could be applicable in case of shell quality problems. 10. Higher levels could be recommended in situations of heat stress.

Increase in egg size with age is due to the increasing size of the yolk, which is also accompanied by more albumen (Grobas et al.)

A reduced level (<1.1-1.2%) of C18:2 (linoleic acid) affects the size of the yolk. Given the little existing knowledge about the actual C18:2 content of DDGS and whole soybeans and the existing variability in relation to their true fat content (and therefore ALA), a practical minimum of 1.35% is recommended.

The inclusion of 3% fat in feed that meets this minimum of C18: 2, improves the size of the egg by approximately 0.6 g.
Supplementary fat is more beneficial in poultry destined for shell-egg production than poultry for egg products industry. This is because albumen is mainly water and therefore has a lower energy and economic value.

High energy levels tend to slightly improve egg size (Pérez-Bonilla et al., 2012; Bouvarel et al., 2010). This is either due to higher levels of added fat in the feed or to higher live weight of the hens. In the case of organic productions, the inclusion of broad beans (Vicia faba) reduces egg size, due to their high content in the glycosides vicin and convicin (Mateos and Puchal, 1982; Lessire et al. , 2017)

Due to the prohibition of molting and in order to amortize the initial cost of pullets, the trend now is to increase the length of laying cycles. In case of long cycles (≥ 80-90 wk) and in order to minimize layer weariness, it’s convenient to avoid excessive egg sizes by reducing the level of Met (and the rest of essential AAs) and controlling the percentage of added fats.

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