The study has many evidence and usefull result about benefit of seawead in animal feed

 Nowaday, as you know,using the natural forms of vitamins and minerals instead of the synthetically produced ones. Both micro- and macroalgae have potential as mineral additives to replace the inorganic mineral salts that are most commonly used in the animal feed industry. It has been suggested that the natural forms are more bio-available to the animal than the synthetic forms and can be even altered or manipulated via the process of bio-absorption.

Mineral rich seaweed has been incorporated in commercial salmon feeds at 15 % in lieu of manufactured vitamin and mineral pre-mixes (Kraan, Mair 2010). Final tests suggested that salmon fed the “seaweed” feeds appeared to be healthier, more active; flavour and texture were improved which may have been due to the bromophenolic compounds found in seaweeds. Elsewhere, Enteromorpha prolifera and Cladophora sp., when added to the feeds of laying hens, positively influenced egg weight and egg shell thickness (Michalak et al. 2010).

The vitamin content of algal biomass can vary significantly among species. Ascorbic acid shows the greatest variability according to Brown and Miller (1992), although this may have been due to differences in processing, drying and storage of algae, as ascorbic acid is very sensitive to heat. This highlights the drawback of supplying essential micronutrients via natural sources, i.e. there is too much variability arising from the combined effects of different algal species, growing season, culture conditions, and processing methods to reliably supply the required micronutrients in a pre-determined fashion. Accordingly, algal biomass mainly offers a supplementary source rather than a complete replacement for manufactured minerals or vitamins in animal feeds.

In both aquaculture and agriculture, producers commonly rely on formulated feeds to ensure optimal growth, health and quality of the farmed animal. Given the economic importance of feeds and feeding, nutritionists therefore need to develop nutritionally balanced diets using commonly available raw ingredients. Once there is reliable data on the nutrient and energy requirements of the target species for a given production performance, specific feeds can be formulated and feeding regimen established.

Typical compositions of feed and feed/gain ratio are summarised in table 2 for several farmed terrestrial and aquatic animal species. This table just provides an overview, as different feed formulations are used depending on the production stage of the target species. Since protein is generally one of the most expensive feed ingredients, targeted rations are used and the amounts of protein in the diet are reduced as the animals grow. As can be seen, feeds for aquatic animals are more energy and nutrient dense than those for terrestrial animals. Due to this, fish need to be fed less to support each unit of growth, as is indicated by the lower feed conversion ratio (FCR).

Table 2: Typical composition of formulated feeds for livestock and several species of commercial fish (on as fed basis) and feed/gain ratio

	% Crude Protein	% Crude Lipid	% Crude Carbohydrate	Metabolisable Energy MJ/kg	FCR*
Poultry	21.0	5.0	60	13.0	2.2
Pigs	16.0	5.0	60	12.5	3.0
Cattle	12.0	4.0	65	10.1	5.8
Salmon	37.0	32.0	15	21.0	1.0
Sea bream	45.0	20.0	20	19.1	1.6
Tilapia	35.0	6.0	40	13.5	1.5
Shrimp	35.0	6.0	40	13.5	2.0

* Feed conversion ratio = feed consumed (dry) / live weight gain

Traditionally, fish meal and fish oil have been a substantial component of feeds at least in aquaculture, however this source is finite. With fish meal and fish oil prices increasing, there has been a growing interest in partial or complete replacement of fish meal by alternative protein sources of either animal or plant origin. Raw materials other than fish meal are selected for their nutritive value, balance of amino acids, digestibility of proteins, lipids and quality of fatty acids, absence of anti-nutritional factors, availability and cost and lipid rich algae biomass is being considered as one of the alternative ingredients of the future (Lupatsch 2009).

To help in assessing algae as a potential source of protein and energy in the form of carbohydrates and lipids, table 3 compares the typical nutritional profiles of commercially available animal feed ingredients with some selected micro- and macroalgae.

Typical composition of commercially available feed ingredients and algae species (per dry matter)

	% Crude Protein	% Crude Lipid	% Crude Carbohydrate*	% Ash	Gross Energy MJ/kg
Fish meal	63.0	11.0	-	15.8	20.1
Poultry meal	58.0	11.3	-	18.9	19.1
Corn-gluten	62.0	5.0	18.5	4.8	21.3
Soybean	44.0	2.2	39.0	6.1	18.2
Wheat meal	12.2	2.9	69.0	1.6	16.8
Spirulina	58.0	11.6	10.8	13.4	20.1
Chlorella	52.0	7.5	24.3	8.2	19.3
Tetraselmis	27.2	14.0	45.4	11.5	18.0
Gracilaria sp1	34.0	1.5	37.1	26.9	13.4
Gracilaria sp2	10.0	0.9	50.1	34.0	11.2
Ulva lactuca1	37.4	2.8	42.2	17.4	15.7
Ulva lactuca2	12.5	1.0	57.0	24.5	11.2
Schizochytrium3	12.5	40.2	38.9	8.4	25.6

* Carbohydrates calculated as the difference % DM – (% protein + % lipid + % ash)
¹ Cultured in effluent of fish tanks
² Collected from natural habitat
³ Commercial product, Martek Biosciences

As noted above, the costs of fish meal and fish oil are steadily increasing. Thus, if a source of protein-rich or lipid-rich algal meal came onto the market at an affordable price, the animal feed industry would certainly consider using it based on existing evidence of the nutritional value of algal biomass.

All these things to show that the real benefit of seaweed ( ulva lactuca, sargassum , gracilaria…, others red algae) for animal feed (especially in aquaculture) .That study you can search deeper informations and figures on https://www.tatup-journal.de/english/tatup121_shlu12a.php

So, now we can see the nutrional value and the necessary  with reasonable and affordable cost, Should all of animal feed manufactures consider these ingredient in final complete mix pellets products?

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