Protein hydrolysates

Protein hydrolysates from poultry by-product and swine liver as an alternative dietary protein source for the Pacific white shrimp

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In shrimp feeds, a protein source with an adequate balance of amino acids is required to provide good growth performance. Recent results showed that up to 25% of dietary protein replacement with protein hydrolysates from poultry by-product and swine liver, as an alternative dietary protein source for the Pacific white shrimp can improve its growth.

In 2017, the world’s production of Pacific white shrimp (Litopenaeus vannamei) was 4,456,603 tons, representing 80% of total shrimp production by aquaculture (FAO, 2018).

One of the major obstacles against the growth of shrimp farming is the reconciliation between intensification and the supply of good quality feed, mainly in terms of protein value and cost, in particular, because feed is essential for successful intensive farming systems (Tacon and Metian, 2008).

“In shrimp feeds, a protein source with an adequate balance in amino acids is required to provide good growth performance. Animal by-products from the rendering industry have been increasingly used as dietary protein ingredients for animal production.”

Such residues have high nutritional value, and as such, they can be used as assets to generate biotechnological solutions for the feed industries. For this reason, the production of protein hydrolysates from agroindustrial waste presents an opportunity to optimize their use as a supply of animal protein for feed production.

In aquaculture, studies have reported positive results for the use of protein hydrolysates as a protein source or feed additive relative to growth performance and the health of shrimp and fish.

“Protein hydrolysates from poultry and swine by-product have emerged to aid in the formulation of more effective diets.”

To improve the performance of shrimp feeds, a protein hydrolysate was produced from the combination of poultry and swine liver in a way that improves the balance of essential amino acids. Besides improving nutritional value, such a combination increases consumption owing to the synergy between peptides present in the different protein sources.

Designing a combination of several protein sources subjected to enzymatic hydrolysis becomes an attractive process by which to improve the performance of the ingredients and identify optimal protein mixing formulations with specific characteristics.

“To date, no study has evaluated the use of protein hydrolysates from poultry by-product and swine liver in the diet of L. vannamei.”

Therefore, the objective of this article is to present a study placed to determine the apparent digestibility coefficient of the protein hydrolysates of poultry by-product and the combination of poultry and swine liver by-product in the diet of Pacific shrimp and to evaluate their effects on attractiveness and zootechnical performance of the species.

Materials and methods

The specie used was the Pacific white shrimp Litopenaeus vannamei of a high health lineage, SPEEDLINE HB12, purchased from Aquatec Ltd. (Canguaretama, Rio Grande do Norte State, Brazil).

The post-larvae were acquired with 4 mg and raised in a biofloc system at the Marine Shrimp Laboratory, Federal University of Santa Catarina (Florianópolis, SC, Brazil), until reaching the weight required to begin each trial.

“Protein hydrolysate from poultry by-product and swine liver was manufactured and made available by BRF S.A. and is marketed as “aminEAU shrimp” (Curitiba, PR, Brazil).”

Two protein hydrolysates were used in the digestibility and attractiveness assay (Table 1), a protein hydrolysate of poultry by-products (chicken viscera, giblets, meat, and antioxidant) and a protein hydrolysate combining protein hydrolysate of poultry by-products and swine liver developed to meet the nutritional requirements in amino acids of marine shrimp.

Protein hydrolysates

The combination of protein hydrolysates shows a better balance of total essential amino acids and a smaller amount of free amino acids, due to the hydrolysis process performed on raw materials (Table 1).

For the growth performance assay in clear water, only the combination of the protein hydrolysates for shrimp was used. The molecular weight of the protein fractions of salmon by-products meal and protein hydrolysate of poultry by-product and swine liver was determined using the Nuclear Magnetic Resonance (NMR) technique.

“The apparent digestibility coefficient (ADC) of dry matter, protein, amino acids, and energy of both protein hydrolysates was determined using the indirect method. The preparation of the diets was started by weighing the ingredients; then the macro and micro-ingredients were dry-blended.”

Initially, shrimp were kept in three 6000-L tanks (one tank for each treatment, n = 3) for seven days as an acclimation period for the experimental diets.

Subsequently, groups of ten shrimp with a mean weight of 8.69 ± 0.73 g (intermolt) were transferred to twelve rectangular glass aquaria (60 L) connected to a seawater distribution system (collected from Barra da Lagoa Beach, Florianópolis, SC, Brazil), aeration system (O2 > 5 mg L-1), and constant heating (28 ± 1 °C).

The attractiveness of four dietary protein sources was evaluated according to the methodology described by Nunes et al. (2006), using the Y-maze.

Protein hydrolysate from poultry by-product, protein hydrolysate from poultry by-product and swine liver, soybean meal, and salmon by-product meal were evaluated. Soybean meal and salmon byproduct meal were evaluated because they are widely used ingredients in commercial diets.

“Only two diets were compared per test, and all diets were compared to each other. For each comparison, a total of 10 tests were performed, using one shrimp specimen per test.”

The total duration of each test was 7 min, and in case no shrimp was detected by the time limit, the specimen was changed.

For the protein replacement feeding trial five diets containing 32% digestible protein, approximately 36% crude protein (CP), with 0, 25, 50, 75, and 100% substitution of the salmon by-product meal protein (71.71% CP) by protein hydrolysates from poultry by-product and swine liver (72.05% CP), the main protein source tested, were evaluated.

A total of fifteen 50-L circular tanks were used, three replicates per treatment, with an aeration system (O2 > 5 mg L−1) and constant water heating (28.49 ± 0.18 °C). All tanks were filled with saline water.

Each tank was stocked with 30 shrimp with an average weight of 3.57 ± 0.04 g. The dietary treatments were distributed entirely at random among the tanks. Shrimp were fed six times a day, using feeding trays (area = 0.03 m2 ) made out of polyethylene material.

“Feed was initially supplied in a daily quantity equivalent to 6% tank biomass and was adjusted weekly according to weight gain, survival, and feed conversion.”

During the six experimental weeks, dissolved oxygen and temperature were monitored twice a day, but salinity, pH, ammonia, and nitrite were measured once a week. Water was exchanged once daily, until all organic matter content (feed waste, feces and, molting) was removed from the water, replacing about 80% of the total volume of water.

Ten shrimp per tank were sampled weekly, and their mean weight was adopted as the weekly weight per tank. At the beginning and end of the growth assay, ten animals from each tank were collected for N (nitrogenous) and P (phosphorus) analysis.

At the end of the six weeks, the following growth parameters were evaluated: total weight gain, weekly weight gain, feed conversion, survival, and N or P retention.

Results

Digestibility assay

The ADC of dry matter and energy of the protein hydrolysate from poultry by-product and swine liver (PHP-PL) was higher than that presented by the Protein Hydrolysate of Poultry by-product (CPH), but no difference (p ≥ 0.05) was observed for ADC of protein between both ingredients (Table 2).

Protein hydrolysates

The ADCs of the amino acids of protein hydrolysates ranged from 82.17–96.95%. Among the essential amino acid ADCs, only tryptophan ADC showed lower digestibility for CPH when compared to PHPPL (p < 0.05). Based on the nutritional composition of the protein hydrolysates (Table 1) and the ADCs, values of digestible energy and nutrients for the Pacific white shrimp were calculated (Table 2).

Attractiveness assay

White shrimp showed no significant preference or rejection among the tested ingredients (CPH, PHPPL, soybean meal, and salmon meal).

Growth assay

For the growth assay, only PHPPL was used since it presented the best ADC in the digestibility assay.

Survival was not significantly different among shrimp fed the experimental diets. Regarding the parameters of growth as final weight, weekly weight gain, and total weight gain, we observed an increase in shrimp growth with 25% protein replacement of salmon by-product meal by the protein hydrolysates of poultry and swine liver, with total weight gain presenting a peak at 24% replacement (4.8% actual inclusion rate in diet).

Diet with 50% protein replacement remained similar to the control diet (salmon by-product meal) with a subsequent decline in shrimp growth up to 100% protein replacement (Figure 1).

Protein hydrolysates

Following the same trend as that shown by growth results, a decrease in shrimp feed conversion was observed at 25% protein replacement with a similar result between control and 50% replacement and subsequent increase for the protein replacement up to 100% (Figure 1).

The minimum was reached with 22.1% replacement. Nitrogen and phosphorus retention followed the same trend. The higher retention rates were found for the control diet and the replacement level of 25%, after which a decline was observed until the 100% replacement level.

Nevertheless, all protein replacement levels promoted satisfactory growth for the species studied (Table 3).

Protein hydrolysates

Discussion

The enzymatic hydrolysis process proved to be highly efficient, modifying the nutritional characteristics of the raw material used and making more nutrients available, generating an ingredient of high protein quality.

“The diet with a 25% protein replacement level presented more favorable results relative to the other dietary treatments, including a 10% increase in growth when compared to the control diet.”

Still, the best-estimated ED: PD ratio based on growth was 1,015 Kcal. g-1 for a diet containing 3,290 kcal kg-1 and 324 g.kg-1. However, a reduction in growth was observed when salmon by-product meal protein replacement by PHPPL was above 50%.

Therefore, the presence of a large amount of low molecular weight peptides (< 1.2 kDa) in the hydrolyzed protein seems to have limited their absorption by sea shrimp, even though they are more available in the tested ingredient.

“As reported in the literature, improvements were also observed in shrimp growth based on performance trials where lower concentrations of protein hydrolysates were used in diets for peneid shrimp (CórdovaMurueta and García-Carreño, 2002; Hernández et al., 2011).”

In fish, growth improvement was reported for different species when fed diets containing low concentrations of protein hydrolysates (Lewandowski et al., 2013; Khosravi et al., 2015; Sary et al., 2017), corroborating the results obtained in our study.

Conclusion

Protein hydrolysate from poultry by-product and swine liver can be used as a dietary protein source for L. vannamei based on the high digestibility and good profile of essential amino acids, similar to fishmeal, which is commonly used as the main protein source in shrimp diets.

These ingredients can be included at lower concentrations in the diet to favor better growth performance. The maximum dietary inclusion for better growth of shrimp is 24% salmon by-product meal protein replacement, i.e., 4.8% inclusion of the protein hydrolysates of poultry by-product and swine liver in the diet.

This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “PROTEIN HYDROLYSATES FROM POULTRY BY-PRODUCT AND SWINE LIVER AS AN ALTERNATIVE DIETARY PROTEIN SOURCE FOR THE PACIFIC WHITE SHRIMP” developed by MARIANA SOARES – Aquaculture Department, Federal University of Santa Catarina; PRISCILA COSTA REZENDE – Aquaculture Department, Federal University of Santa Catarina; NICOLE MACHADO CORRÊA Aquaculture Department, Federal University of Santa Catarina; JAMILLY SOUSA ROCHA – Aquaculture Department, Federal University of Santa Catarina; MATEUS ARANA MARTINS – Aquaculture Department, Federal University of Santa Catarina; THAÍS COSTA ANDRADE – R & D Animal Nutrition, BRF S.A.; DÉBORA MACHADO FRACALOSS – Aquaculture Department, Federal University of Santa Catarina; FELIPE DO NASCIMENTOVIEIRA – Aquaculture Department, Federal University of Santa Catarina.
The original article was published in Aquaculture Reports, in Abril 2020.
The full version, including tables and figures, can be accessed online through this link https://doi.org/10.1016/j.aqrep.2020.100344

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