Calcium (Ca) and phosphorus (P) are two essential macrominerals in poultry production, for both broilers and layers, and both require mandatory supplementation.

Meat and bone meal is widely used because it is cheap and adds protein and essential amino acids to the formulation, and it is also a sustainable ingredient. However, it carries a high biosecurity risk, as it is the main source of pathogens such as Salmonella and Clostridium. For this reason, it is not used in breeder diets or where a higher sanitary standard is required in production, as in some export destination countries.

In addition, meat and bone meal is widely used in pet food and aquaculture, which tends to drive its cost up. As a result, dicalcium phosphate is increasingly used as the main source of P in animal production.

Dicalcium phosphate is a finite, unsustainable ingredient in high demand from agriculture, with rising costs and a growing risk of scarcity. Reducing the use of P sources is a central topic in modern ESG management, which covers environmental, social and governance issues.

Two points must be considered in order to reduce the use of Ca and P sources. One concerns the nutritional requirements of each animal category for each element (Liu et al. 2017). The other concerns the digestibility of each source, whether grains, animal-origin meals or mineral ingredients.

It is worth noting that in animal trials, the study of one aspect is always closely tied to the other (Adedokun and Adeola, 2013; Proszkowiec-Weglarz and Angel, 2013).

The study of how well poultry digest these minerals is a recent concern. Despite its importance, it is quite difficult to measure the digestibility of each mineral accurately. Several factors act at the same time, such as the pH of each part of the digestive tract, the presence of other ions, the Ca to P ratio, vitamin D, hydration, particle size, etc. (Adedokun et al. 2014; Rodehutsford et al. 2017; Van Horn et al. 2017).

If each of these factors is not carefully controlled in the experiments, discrepant results will be obtained, including negative digestibility. This happens because endogenous Ca and P are also excreted along the digestive tract, making it hard to measure how much of each mineral from an exogenous source was retained in the body (Yixin, 2021).

Given these difficulties, the levels used in formulations often include a safety margin, which ensures that the available level of each mineral does not limit maximum performance. As already mentioned, P has a high economic and environmental cost. Ca, on the other hand, is cheap and still abundant in nature.

However, there is growing evidence that excess Ca interferes negatively with several body functions, including P absorption itself. In light of this, the goal is to work with ever lower and more precise levels of each mineral (Li et al. 2017).

The efficacy of microbial phytases in releasing phytic P from plant-based raw materials such as grains and meals is widely known. The exact amount of P and Ca that animals will actually use, on the other hand, still leaves room for discussion, precisely because of the interference of several other factors.

This fact, combined with the variable digestibility of ingredients, allows us to conclude that there is room to improve Ca and P absorption and retention in poultry, reducing formulation costs as well as the environmental impact of their excretion.

With this goal in mind, GFS’s patented technology (Poligrow®) has been under study. It is a long-chain fatty acid with hydroxyl groups replacing hydrogen. It has strong emulsifying action but also acts as a carrier of Ca and P.

Once ionized by the low pH of the proventriculus and gizzard and released from inositol by phytases, phosphate and Ca ions form complexes with this technology, either through ionic bonding between the phosphate and the hydroxyl group or through a saponification reaction with the terminal carboxyl group.

In this form of Ca soaps and phospholipids, the ions are absorbed through the lipid absorption pathway, in micelles containing bile salts, steroids, mono- and diglycerides and fat-soluble vitamins. Its emulsifying action even improves the formation of these micelles, increasing dietary lipid absorption and, with it, the metabolizable energy of the diet.

To validate the technology’s emulsifying and ion-carrying action and quantify its activity, a broiler trial was carried out at Granja Santa Lívia, RS. A total of 770 broilers were distributed among 5 treatments, each with 7 replicates of 22 birds.

A control treatment was formulated at the levels recommended by the genetic line, in a typical Brazilian diet based on corn, soybean meal and soybean oil, and containing 2 commonly used exogenous enzymes, phytase and carbohydrase. Phytase was used at 1,000 FTU, with a matrix value of 0.15% Ca and 0.15% P, along with a xylanase-based carbohydrase with a value of 50 kcal/kg of metabolizable energy.

Dicalcium phosphate and calcitic limestone were used as the P and Ca sources. Three other treatments were run, with gradual reductions in metabolizable energy (-20, -40 and -60 kcal/kg) and equal reductions in available Ca and P of 150% (0.15%). Poligrow® was added to the diet with the lowest energy level (-60 kcal). All other rearing conditions were the same for all treatments, in a completely randomized design.

The cumulative results for weight gain and feed conversion showed that adding Poligrow® to the feed with the lowest nutritional levels gave performance statistically equal to an intermediate diet between the -20 and -40 kcal levels, validating the expected matrix of 36,000 kcal per kg of the preparation containing 20% of the technology.

Dry matter and ash content of the tibias from animals fed the diet with reduced Ca and P plus Poligrow® were equal to those of the control diet, while the other treatments were statistically inferior to the positive control, validating the matrix of 150% available Ca and 150% available P.

In addition to these results, the amount of Ca and P deposited in the tibias of treated animals was higher than in the other treatments. This is probably because the greater availability of P allowed more hydroxyapatite to form, versus Ca carbonate. This formation is particularly important for broilers, for bone strength, especially in the long leg bones (Leeson, 2012).

In laying birds (layers and breeders), greater deposition in medullary bone, which is needed for eggshell formation, will mean fewer shell quality defects and longer production life.

These results lead us to conclude that use of this emulsifier, together with normal doses of exogenous phytase, allows lower levels of Ca and P sources in the diets of production birds (broilers and heavy breeders), in line with the proposed matrix of 36,000 kcal ME, 150% available Ca and 150% available P per kilogram of a preparation containing 20% Poligrow®.

Authors:

José Luciano Andriguetto, Veterinarian, Ph.D. in Animal Nutrition, Professor in the Department of Animal Science at UFPR

André Favero, Animal Scientist, Postdoctoral Fellow in Animal Science, Administrator and Coordinator of Granja Santa Lívia Produção e Pesquisa Agropecuária Ltda