Analysis of losses and edible and inedible by-products generated during harvesting, slaughtering and processing stages of broiler chickens under industrial conditions

Food losses, as major sustainability obstacles, have raised enormous concerns in recent years due to their contribution not only to significant resource, climate, and environmental impacts but also to huge economic and nutritional impacts. While various studies have indicated that reducing food loss and waste could benefit food security and environmental sustainability, the extent of such benefits depends on the level of reduction and thus requires a good benchmark of the current loss and waste throughout the agri-food supply chain. Food losses occur at various points in the poultry supply chain, from production and harvest to distribution and consumption. A large proportion of unintentional food losses occurs during the ante-mortem phases. At the end of the growing phase, birds are caught, loaded into cages or coops, and transported to a processing plant that may be located either close to or far from the farm. Many problems may occur at these stages that potentially increase the rate of mortality, liveweight losses, and carcass downgrading. Before birds are caught and crated, feed is removed to allow time for the evacuation of intestinal contents. This reduces the incidence of faecal contamination of the carcass, which may occur during slaughtering. However, the length of fasting is important because it affects liveweight losses, which can impair carcass weight and yield. In the first 4–6 hours, weight loss in birds is mainly due to emptying of the gut, so carcass yield is not negatively influenced. After 6 hours, there are also losses in moisture and nutrients from body tissues, which reduce carcass weight and yield. During catching and crating operations, a certain level of trauma, such as haemorrhages, bruises, and broken bones, occurs and originates food losses at the slaughter plant, as these parts must be trimmed and discarded as by-products, and the remaining parts are downgraded and used as raw materials for further processing. In addition, trauma occurring during harvesting at the farm exacerbates pre-slaughter mortality. Indeed, birds that are dead on arrival (DOA) at the plant represent a complete loss of economic value. The birds may be exposed to a variety of potential stressors during transit, including the thermal demands of the transport microenvironment, acceleration, vibration, motion, impacts, fasting, withdrawal of water, social disruption, and noise. These factors cause adverse effects on the birds that may range from mild discomfort to death. Environmental conditions during transport and lairage of poultry have also been shown to affect live shrink and processing yield, especially because birds respond to the increased temperature by increasing panting, which alters water intake and body moisture loss profiles. At the time of slaughter, a certain percentage of broiler carcasses and parts are condemned by veterinary inspectors due to signs of pre-existing disease, severe injury, abnormality, or contamination, making the products unfit for human consumption.