Partial replacement of soybean oil by insect oil in broiler diets
Wageningen Livestock Research, in collaboration with PHW Group’s daughter company Esbro, feed producer ForFarmers and insect ingredient producer Protix, conducted a broiler field study in which 1% of soybean oil was replaced by Black Soldier oil. This study was carried out within the Public Private Partnership ‘Enrichment of the diet with insect-based feed ingredients for 1 Star Better Life labelled broilers.
The world population is expected to reach 9.7 billion by 2050, leading to an increasing demand for food and feed. The broiler production sector plays an important role in meeting the increasing global demand for animal proteins. However, there are environmental and societal concerns about the intensive farming system and soybean meal as the most common protein source in broiler feed. Recent innovations address these concerns, including the use of novel and more sustainable ingredients in broiler feed and the use of slow-growing strains/breeds in alternative production systems. Insect products are considered valuable and more sustainable alternative ingredients, because of their high nutritional value and their contribution to circularity.
Since the end of 2023, Dutch supermarkets have sold only fresh chicken meat produced according to the Better-Life 1-star label. This novel concept is based on the use of a slow-growing breed, kept at a lower stocking density, where the animals are given environmental enrichment such as straw bales and daylight in the houses and the animals can go to a covered outdoor run. Incorporating insect products as local ingredients in the slow-growing broiler production system, such as Better Life 1-star, may increase the sustainability of this type of chicken meat production.
Pilot: Substituting BSF oil for soybean oil
Therefore, Wageningen Livestock Research, in collaboration with PHW Group’s daughter company Esbro, feed producer ForFarmers and insect ingredient producer Protix, conducted a pilot in which different inclusion levels of Black Soldier Fly (BSF) meal (0, 1, 5%), BSF meal with extra chitin (0, 1 and 5%), and BSF oil (0, 1, and 2.5%) were tested. Based on the results of this pilot study, a field study was conducted in which 1% soybean oil was replaced by 1% BSF oil. We have selected 1% inclusion as a first step to be tested in the field study as the most interesting option with respect to current economic feasibility, expecting that this will change with further upscaling of the insect industry. This article describes the results of the field study in which 1% insect oil was included in the diet.
Field study
The field study was conducted over two consecutive flocks on six commercial broiler farms varying in size, each having at least two poultry houses. In one house, Hubbard JA757 broilers were fed the standard farm feeding regimen (Control), while in the other house, the same feed was provided, except that 1% soybean oil was substituted for 1% BSF oil (Test). In the second round, the treatments were reversed between houses to mitigate any possible house effect. The farmers provided the performance data such as total feed use, delivered weight to slaughterhouse, and mortality per house per flock. Based on the data provided, the performance results were calculated. The broiler performance was comparable between broilers that received the control diet and the test diet, as can be seen in Table 1.
Slaughter quality and yields
In addition to the growth performance results, carcass quality and yield assessments were conducted at the slaughterhouse. Carcass quality was assessed using the standardised system for broilers at the slaughter line, which is a key component of the Dutch IKB Chicken certification scheme (IKB Kip, 2017). Authorised veterinarians assessed carcass quality parameters and expressed them as a percentage of the total number of assessed birds. At the slaughterhouse, dead on arrival (DOA), total rejections, overall quality score and footpad lesion score were determined. Dead-on-arrival chickens (DOAs) are chickens that are delivered dead to the slaughterhouse. Total rejections include the following chick abnormalities: abnormal colour/odour/taste, polyserositis, arthritis/synovitis, hepatitis, ornithobacterium rhinotracheale (ORT) infection signs, back muscle inflammation, pericarditis, ascites syndrome, subcutaneous inflammation, wooden breast, condemned parts, and other abnormalities. The quality score was calculated based on the incidence of scabby hips, skin scratches, ammonia burns and leg/wing/breast bruising/hematomas. This score is slaughterhouse-specific. The lower the score, the better the slaughter quality of the flock.
In order to calculate the footpad score (FPS), the automatic system evaluated the condition of the birds’ feet according to the Swedish 3-point scale for dermatitis. This scale includes category 0 (no or hardly any evidence of dermatitis), category 1 (mild to moderate lesions), and category 2 (severe footpad lesions). After assessing the feet, the flock FPS was calculated as follows: [% category 1]*0.5 + [% category 2]*2. The FPS can range from 0 (all birds having no lesions) to 200 (all birds having a score of 2). Slaughter quality was comparable between broilers fed the test diet and those fed the control diet (Table 2). Also, footpad scores were comparable between the treatments, indicating that partial replacement of soybean oil with BSF oil is possible without affecting the incidence and severity of footpad lesions. Carcass yields such as carcass, breast cap, wing and saddle were comparable between the treatment groups (Table 3).
Welfare measurements
Due to the visitor ban caused by Avian Influenza, it was not possible to conduct welfare observations in the first flocks. The welfare observations were conducted just before delivering the flock to the slaughterhouse. For this purpose, around 150 broilers per house were randomly collected in a catching pen at six randomly selected locations in the house for individual gait scoring assessment according to Welfare Quality (2009) scale, from 0 (perfect locomotion) to 5 (unable to walk). Subsequently, a total of 125-150 broilers were randomly collected in a catching pen at five randomly selected locations per house and assessed for footpad lesions, hock burns, cleanliness and injuries (scratches and wounds). Footpad lesions and hock burns were scored on a scale from 0 (no lesions) to 4 (severe lesions on the foot or hock). Cleanliness was scored by inspection of the belly on a scale between 0 (clean) and 3 (very dirty). Injuries were scored on a 3-point scale (0: no injuries or a maximum of 3 scratches; 1: single lesion smaller than 2 cm2 or more than 3 scratches; 2: at least one lesion larger than 2 cm2). All scores were conducted by one trained and experienced observer. Besides welfare observations, litter quality was scored by a trained observer through visual inspection and classified on a scale between 0 (completely dry and loose) and 4 (very wet or completely capped with a crust).
Overall, visual litter quality, gait, cleanliness, footpad lesions, hock burns and injuries were similar between the treatment groups, indicating that partial replacement of soybean oil with BSF oil does not affect the litter quality and the scored welfare parameters (Table 4). A diet effect was found on one farm only, and on this farm, scores for gait, footpad lesions, hock burns and cleanliness were lower (better) on the test diet. For litter quality, there was a farm effect, meaning that litter quality differed between farms independent from the diets used.
Divert from soybean oil
Replacement of 1% soybean oil with 1% BSF oil resulted in similar growth performance, litter quality, welfare, slaughter yields and slaughter quality compared to a commercial diet for Better Life 1-star broilers under practical field conditions. Substitution of 1% soybean oil by 1% BSF oil is possible based on performance results and provides an opportunity to divert from soybean oil but its application has to be supported by sufficient incentives.
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