Intake, growth performance and nutrient digestibility of broiler chicken fed diets containing black soldier fly larvae meal

Adam N R¹, Adjorlolo L K², Obese F Y¹, Osae M³, Ayizanga R A¹, Osei-Amponsah R¹ and Nagetey A³

¹ Department of Animal Science, School of Agriculture, University of Ghana, Legon, Ghana
lkadjorlolo@ug.edu.gh
² Livestock and Poultry Research Centre, University of Ghana, Legon
³ Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Agency, Accra, Ghana

Abstract

The effects substitution of soya bean meal with black soldier fly larvae meal (BSFLM) in iso-nitrogenous diets on the growth performance, apparent ileal nutrient digestibility of broiler chickens were investigated in this study. Black soldier fly larvae produced on fruit and vegetable wastes were harvested on the 14^th day. The larvae were oven-dried and milled into a meal. The insect meal was included at 0%, 10%, 20% and 30% in broiler chicken starter diets and 0%, 10%, 20% and 27% in broiler chicken finisher diets. A total of 204 broiler chicks (Cobb-500 strain) were randomly selected and divided into four treatment groups of 51 birds. Each treatment group was further divided into three replicates of 17 birds in a completely randomised design. From the age of 8 to 49 days, the birds were fed with the experimental diets. Feed and water were given ad libitum. Feed intake, digestibility and body weight gains were measured Data collected were subjected to one-way analysis of variance and significant differences among means separated using the Student-Newman Keuls (SNK) test. The results showed that the inclusion of black soldier fly larvae meal up 20% did not have any adverse effects on feed intake, growth performance and profitability of broiler chickens. However, the inclusion of more than 20% black soldier fly larvae meal resulted in poor apparent ileal digestibility of dry matter, crude protein and ether extract. It was concluded that black soldier fly larvae meal can be included in broiler chicken diets up to 20% without any adverse effects on growth performance and nutrient digestibility.

Key words: poultry, insect meal, dietary protein, nutrient digestibility

Introduction

The Ghanaian poultry industry relies mostly on imports for its protein concentrates (fishmeal and soybean meal (SBM) for producing feed for chickens (Anankware et al 2018). These ingredients are expensive on the market leading to high chicken production cost. There is therefore the need to find more available, cost effective and high-quality alternative protein sources for chicken feed.

The use of insects for human and animal feed is receiving increasing attention in recent times. The larvae of black soldier fly (Hermetia illucens), a non-pest fly in tropical and temperate areas (Maglangit and Alosbanos 2021), are a promising source of dietary protein in broiler chickens (Anankware et al 2018; Facey et al 2023; Heita et al 2023). Black soldier fly larvae meal (BSFLM) has high metabolisable energy (2,567–5,745 kcal/kg) and crude protein (38-65%) and contain good amino acid profiles (Schiavone et al 2017; Chobanova et al 2023; Nandhirabrata et al 2023). It has been reported to be 90% digestible and has been suggested to be a good substitute for SBM (Schiavone et al 2017; Onsongo et al 2018; Shumo et al 2019b).

In some studies, substituting up to 25% of SBM or fishmeal with BSFLM in broiler diets improved growth performance (Facey et al 2023; Fruci et al 2023), but inclusion beyond this rate adversely affected growth performance due to the high chitin content in BSFLM which reduced digestibility of crude protein (Cutrignelli et al 2018) in the diet. In these studies, more mature larvae (harvested at the latter stage of development) were used in formulating the diets.

There is limited information on the effects of dietary inclusion of BSFLM from early on harvested larvae growth performance and digestibility of nutrients in broilers on iso-nitrogenous diets. In this study therefore the effects of BSFLM-based diets from larvae harvested at earlier stage of development on feed intake, growth performance and ileal digestibility of nutrients were evaluated. The profitability of replacing SBM with BSFLM in broiler chicken diets was also assessed.

Materials and methods

Location of study

The study was conducted at the Livestock and Poultry Research Centre (LIPREC) of the University of Ghana. LIPREC lies within the Coastal Savannah zone of Ghana on latitude 05⁰ 40’ N and longitude 00 ⁰ 16’ W (Ampong et al 2019). It experiences bimodal rainfall with an average of 881 mm (Adjorlolo et al 2014) and varying temperatures between 24.3^OC and 32.9^OC (Sarkwa et al 2020).

Source of experimental material

The black soldier fly larvae were raised on fruit and vegetable wastes at the Biotechnology and Nuclear Agriculture Research Institute (BNARI) of the Ghana Atomic Energy Commission. The 4^th instar larvae were harvested and cleaned by soaking in bubbling water at 84⁰C for 40 seconds. The cleaned larvae were then oven-dried at 65^oC for 48 hours. A hammer mill was used to grind the weighed dried larvae together with weighed dried maize into a meal.

Dietary Treatments

The BSFLM was utilised as a source of protein at varying inclusion levels of 10, 20, and 30% in broiler starter diets, and 10, 20, and 27.2% in broiler finisher diet to meet the crude protein and energy requirements of broiler chickens. A two-phase feeding regime consisting of starter diet and finisher diet were used. For both feeding phases, the four diets were formulated to be iso-nitrogenous and iso-caloric, with SBM in the control diet replaced by BSFLM, as indicated in Table 1. The compounded diets were formulated to meet the nutrient requirements of poultry according to NRC (1994): starter diets of 3000 kcal/kg ME and 22 – 23% CP (Table 2), and finisher diets of 3100-3200 kcal/kg ME and 18 – 19% CP (Table 3). The experimental starter diets were given to the birds from days 8 to 28, and the finisher diets from days 29 to 49. Feed and water were supplied ad libitum throughout the trial.

Experimental birds and their management

A total of 204 unsexed Cobb-500 birds that were 7 days old were used in the experiment. For a period of 7 days, all the chicks were raised together in the brooder house and were offered a commercial starter diet and water ad libitum (freely available). On the 8th day, the chicks were relocated to an open-sided poultry house, where they remained until the end of the feeding trial, which lasted for 42 days. To raise the birds, a total of 12 deep litter pens, each measuring 2.5m x 3.0m, were used. Wood shavings was used as bedding material. The birds were weighed and allocated at random to 4 dietary treatment groups each with 3 replicates there were 17 birds per replicate in a completely randomised design. The birds were given routine medications and supplements (vitamins and minerals) through drinking water. On days 7 and 21, as well as on days 14 and 28, they received oral vaccinations against Infectious bursal disease and Newcastle disease, respectively.

Determination of chemical composition of feed ingredients and compunded diets

Samples of BSFLM, SBM, and the formulated diets were ground to pass through a 1 mm screen for chemical analysis. The prepared samples were analysed for dry matter (DM), crude protein (CP), crude fibre (CF), ether extract (EE), and ash according to AOAC (2005). The metabolizable energy (ME) concentrations of the experimental diets were determined using the formula given by Wiseman (1987) as:

ME (kcal/kg DM) = 3951 + 54.4 EE - 88.7 CF - 40.8 ash.

Determination of feed intake and growth performance parameters

Body weights (g) were measured at the beginning of the experiment and then once at weekly intervals. The amount of feed that was supplied each time was recorded, and the amount that was refused was weighed weekly on a pen basis. The data were used to determine average daily feed intake (ADFI) and average daily weight gain (ADG). Feed conversion ratio (FCR) was computed for each phase by dividing feed intake by body weight gain (feed/gain). Protein efficiency ratio (PER) was calculated by dividing the weight gain by protein consumed The energy efficiency ratio (EER), was calculated as a percentage of weight increase relative to total ME intake. The feed intake (FI) and unit price of feed (P) were multiplied to determine the feed cost (FC).

Determination of apparent ileal digestibility of nutrients

On days 27 and 48 of the trial, the birds were starved of feed overnight and fed for 4 hours in the morning of days 28 and 49 prior to their sacrifice to ensure that the gut was full.

On days 28 and 49 of the experiment, two birds were randomly chosen from each replicate (a total of 6 birds per treatment) were sacrificed and the small intestine separated. The ileal contents were collected from the Meckel’s diverticulum up to about 2 cm before the ileo-caecal intersection. The ileal digesta samples from the same treatment were pooled and frozen. The collected samples were transported to the laboratory and dried in an oven at 60^OC. The dried samples were ground using a laboratory mill equipped with a 1 mm sieve. All samples were analysed for DM, CP, ME, CF, EE, and ash according to standard methods (AOAC 2005).

The apparent ileal digestibility (AID) was calculated using the net disappearance of ingested dietary CP from the proximal ileum. The following formula adopted from Kong et al. (2014) was used to determine the AID of CP, as well as apparent retention of nutrients.

Data analysis

All data collected were subjected to a one-way analysis of variance (ANOVA) in a completely randomized design, using GENSTAT Statistical Software 12th Edition (2009). A 5% significance level were employed for the statistical testing, and significant differences among means was separated using the Student-Newman Keuls (SNK) test.

Results

Chemical composition of feed ingredients

Table 4 shows the chemical compositions of the BSFLM and SBM. Although both feed ingredients had comparable crude protein, crude fibre, and ash contents, the BSFLM had higher ether extract than SBM.

Effects of BSFLM on intake and growth performance of broiler chickens

Table 5 shows growth performance of birds in the starter and finisher phases, and the overall. Birds on dietary treatment T0 (Control; 0% BSFLM), T1 (10% BSFLM), and T2 (20% BSFLM) had higher (p<0.05) ADG, total weight gain and better FCR than those on T3 (30%BSFLM) during the starter phase. The PER, and ERR were higher (p<0.05) for birds on T0, and T2 than those on T3 during this phase. Birds on dietary treatment T2 had better (p<0.05) FCR, and higher PER, and ERR than those on T3 during the finisher phase. Overall, birds on diet T1 had higher (p<0.05) ADG than those on T3. Also, birds on T0, T1, and T2 had higher (p<0.05) final bodyweight, and better FCR than those on T3.

Apparent ileal digestibility of nutritional component of diets

Table 6 details the impact of BSFLM on nutrient digestibility in broiler chicken diets during starter and finisher phases of the feeding trial. During the starter phase, birds on T3 had lower (p<0.05) ileal DM, CP, EE, ash, and CF digestibility compared to the other treatments. During the finisher phase, birds on T3 had lower (p<0.05) ileal DM, EE, ash, and CF digestibility than those on T0, T1, and T2. Ileal crude protein digestibility was lower (p<0.05) in birds on T0 and T3 than those on T1.

Discussion

Effects of BSFLM on growth performance of broiler chickens

The study found that feeding birds 30% BSFLM reduced ADG by 14.21% during the starter phase, leading to poorer FCR. The poor final body weight of birds on T3 may be due to their reduced ADG and also accounted for their poor FCR during the finisher phase. The results in the current study agree with previous studies showing that higher BSFLM levels reduced ADG and resulted in poor FCR (Facey et al 2023; Fruci et al 2023). According to Cutrignelli et al (2018), the high chitin concentration of the feed due to the high inclusion of BSFLM interferes with protein digestion, reducing growth performance. However, (Kirimi et al (2023) in a recent study reported that BSFLM can be included in broiler diets up to 25% (100% substitution of SBM) without adverse effects on growth performance. Their study revealed that while ADFI decreased with increased BSFLM inclusion level, ADG improved.

In the current study, high levels of BSFLM reduced overall growth performance (ADG, FCR, and final body weight) probably due to reduced nutrient digestibility and utilization as seen in Table 6. The decreased CP and EE utilisation efficiency might be linked to the chitin content of BSFLM-based diets. Chitin is an anti-nutritional factor present in the exoskeleton of black soldier fly larvae (Facey et al 2023; Nampijja et al 2023) and is known for inhibiting the processes of nutrient digestibility, utilisation, and feed efficiency in broiler chickens fed diets containing BSFLM (Chobanova et al 2023). Along with chitin, the high ether extract content of feeds containing BSFLM may impact the performance, digestion, and absorption of nutrients (Kirimi et al 2023).

Effects of BSFLM on apparent ileal digestibility of nutrients

The lower digestibility in poor FCR, lower PER, EER, and body weight gain resulting from feeding 30% BSFLM may be due to the presence of chitin which is known for interfering with digestibility of nutrients. The study collaborates Hartinger et al (2021) findings that 30% defatted BSFLM in broiler chicken diets reduces protein digestibility, while Nampijja et al (2023) found reduced ileal digestibility of CP and EE when BSFLM completely replaced fishmeal in broiler starter diets. In the current study apparent ileal digestibility of DM, CP, and EE in BSFLM-based diets were higher than values reported by Nampijja et al (2023). The age at harvesting of the larvae and processing methods could have also improved the digestibility of the nutrients, making them more readily available to the birds and resulting in better utilisation.

Conclusion

· Feeding up to 20% (that is, about 60% and 85% replacement of SBM in starter and finisher diets, respectively) led to similar ileal digestibility, growth and body weight at slaughter compared with the control of 100% SBM. However, total replacement of SBM with BSFLM led to decreased performance.

Acknowledgement

The authors would like thank management and staff of LIPREC of the University of Ghana and Biotechnology and Nuclear Agricultural Research Institute of the Ghana Atomic Energy Commission. The research was supported by the A.G. Leventis Foundation Scholarship for graduate students.

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