Over the past 10-15 years, there has been a further increase in the performance of layers as a result of genetic selection. Today, layers are able to achieve a laying rate above 90 % for more than 60 weeks with higher persistency without the need for moulting with an increased feed efficiency, and improvements in the rate of saleable eggs. These are indicators of these genetic advancements.
However, genetic progress alone is not sufficient to achieve the expected productivity, sustainability and profitability. It is essential to ensure both good nutrition and flock management, simultaneously, to reach the genetic targets, and only then, success and profitability will follow. In addition to these challenges, egg producers also face other difficulties such as increased in-house temperatures due to global warming, compliance with new requirements concerning animal welfare and emission of potential contaminants.
Precise nutrition using high quality feed is one of the most important criteria for achieving genetic goals. However, sourcing and using consistently high-quality and digestible raw materials can be challenging at times. Moreover, antinutritional factors must be minimized while maintaining gut health and integrity to ensure optimal digestion. In order to address these problems, feed additives are often used by nutritionists because of their advantages in maintaining gut health and integrity and ensuring optimal digestion.
REARING PERIOD
During the first half of the 16-week pullet rearing period, the aim is to achieve rapid growth potential and obtain highest body weight with a good body composition. The feeding program should focus on providing digestible amino acids and minerals to ensure the fundamental development of internal organs, muscles, and the skeleton in this early stage of life. This is the first step that needs to be taken for ensuring success throughout the entire laying period. The digestive system of chicks is not yet fully developed in this early stage, it is important to use raw materials with high digestibility. In addition, development of intestinal epithelial tissue, villus heights, and crypt depths occurs during this period, the cost of supporting butyrate is relatively cheaper compared to other feed additives and therefore preferred. Butyric acid has well documented anti-inflammatory effects and has been shown to strengthen the gut mucosal barrier through the stimulation of tighter junctions between the cells of the gut epithelium (Richard Ducatelle, 2015. The benefits of butyrate have been demonstrated in many in vivo and in vitro studies, as shown in table 1 and 2. This feed additive is important especially during the initial phase as it can contribute to optimal live weight development. On the other hand, an emulsifier that enhances the digestion of additional fats can be preferred during the first 5 weeks of the process.
Table 1 – Duodenal morphology and weight gain from 21-27 day following challenge with coccidial oocyst
| Treatments | Weight gain | Duedoneum nm Villus lenght | Duedoneum nm Crypt depth |
|---|---|---|---|
| Control | 252 b | 1.428 | 270 a |
| 0.2% butyric acid | 316 a | 1.562 | 266a |
Table 2. Histomorphological parameters of the ileum (μm) according to Alicja Sobczak and K. Kozłowski 2016
| Items | Group T1 | Group T2 | Group T3 | p |
|---|---|---|---|---|
| Thickness of glandular layer | 701a ± 177 | 862a ± 54 | 624b ± 109 | 0.003 |
| Villus height | 701a ± 177 | 729a ± 47 | 529b ± 91 | 0.003 |
| Crypt depth | 124a ± 28 | 133a ± 22 | 97b ± 29 | 0.023 |
| Villus height: crypt depth ratio | 5.76 ± 208 | 5.60a ± 0.89 | 5.62 ± 0.95 | 0.931 |
T1: control group fed on a basal diet; T2: basal diet supplemented with an encapsulated source of butyric acid at 500 g/t feed; T3: basal diet supplemented with protected sodium butyrate at 700 g/t feed.
The goal of the second half of the pullet rearing period is to increase the pullets’ feed intake capacity. Increasing feed intake capacity is crucial for achieving maximum peak of laying rate and persistency during the whole laying period. During this period, it is important to include feed formulations with lower density raw materials that have a higher crude fibre content as the demand for protein and amino acids decreases. If suitable raw materials are available, reaching a crude fibre content of up to 5-6% in the diet formulation at this feeding stage may be recommended.
TRANSITION PERIOD
At the end of the pullet phase, just before the onset of egg production, the transition is made from the pullet stage to the laying stage, which means that almost all metabolic processes change significantly. Due to hormonal regulation, the development of medullary bones is initiated, and all metabolic processes progress towards egg production. Meanwhile, at the beginning of production, flocks should show increased weight gain. To support medullary bone formation and the development of certain reproductive parts, pre-lay feed should be given before the start of egg production. Using pre-lay feed in the correct amount and timing is important for the success peak production.
PRODUCTION PERIOD
First phase of production period is a time when laying hens reach their highest laying rate, and consequently, exhibit maximum performance. During this period, a good feed quality, optimal digestion with a good feed granulometry plays an important role alongside precise nutrition. Phytase and NSP enzymes are used from rearing and production period to increase digestion of feed and decrease nutrient content in the manure. It is crucial that the enzymes used in feeds do not lose their effectiveness in different pH conditions and during heat treatment.
Another crucial factor throughout the life of the bird is feed hygiene. When mycotoxin levels exceed acceptable limits, it is necessary to reduce their absorption and contact with the gut, thus, anti-mycotoxin products are an important aid. On the other hand, the use of appropriate organic acids added to feeds is necessary to reduce unwanted mould and bacterial loads in the feed. Attaining optimal feed hygiene not only maintains performance but also enhances the absorption of nutrients and minerals. Furthermore, using feed additives with antioxidant properties that can reduce the oxidation of added fats also supports gut integrity.
Increasing digestion of nutrients and minerals is also related to good gut health. There are feed additives containing natural active ingredients with mode of actions similar to antibiotics that protect gut health. These active substances mainly include organic acids, plant extracts, essential oils, probiotics, and prebiotics. They are generally referred to as natural feed additives. The impact of these substances on the gut health and performance of laying hens has been proven through in vitro and in vivo trials. Nutritionists prefer to use these products in feeds to reach the maximum genetic potential, according to the current conditions. Beside this, after the peaking period, usually after 50 weeks and depending on the conditions, the addition of metabolites of vit D and/or chelates forms of minerals such as Zn, Mn, and Cu to feeds can protect bones and improve eggshell quality and improve performance .
Figure 1: Effects of different feed additives on laying hen productivity
Phytogenic blends (PBl), thymol (THY), carvacrol (CV), cinnamaldehyde (CN), sodium butyrate (SB), xylo-oligosaccharides (XOS), fructooligosaccharides (FOS) and mannooligosaccharides (MOS). The bars indicate the average difference against a control group: for hen day% is expressed in percent, for FCR in points (kg/kg), the oxidative stress biomarkers are expressed as weighted mean differences (WMD) for serum superoxide dismutase (SOD) and malondialdehyde (MDA). (Based on: Orzuna-Orzuna & Lara-Bueno, 2023; Miao et al., 2021; Zhang et al., 2022; Adli et al., 2023, *indicate significant differences against a non-supplemented control)
Figure 1 shows the performance improvements obtained with some of feed additives obtained by meta-analysis in average the trials start at 35 weeks of age and have a 2-weeks duration. These can provide nutritionists some insights that can help to take decision for their strategies. Phytogenics enhances performance by improving gut health having antioxidant and anti-inflammatory properties, keeping a healthy barrier and reducing the resources used for unnecessary inflammatory reactions, thus improving performance. Other reported effects of phytogenics are the improvement of the antioxidant status of eggs of internal and external egg quality. Oligosaccharides, such as MOS, FOS and XOS act as prebiotics, they can modulate the intestinal microbiome, enhancing the population of beneficial bacteria and increasing its products, such as butyric acid. They can also suppress potentially pathogenic gram-negative bacteria. The overall effect provides better intestinal integrity and nutrient absorption, enhancing performance. Sodium butyrate, has anti-inflammatory and antioxidant effects, reducing oxidative stress and pathogenic microbiota in the intestine, for gut health and performance.
CONCLUSION
As a conclusion, producing well-balanced and good quality diets is increasingly challenging due to limited raw materials, digestibility of raw materials, antinutritional factors found in their structure, and presence of unwanted bacteria and fungi. In this light, natural feed additives help reduce risks by contributing to the production of optimal and cost-effective feed rations which also aid in improving laying hen performance and help reach their maximum genetic potential. In addition, challenging conditions such as low biosecurity, poor flock health status, and unfavourable farm management conditions can further enhance the benefits and profitability of these feed additives. Local nutrition experts can add the most suitable feed additives at the right time to their feeds according to the current quality of raw materials and environmental conditions, enabling the layers to reach maximum genetic potential.
