In 2022, poultry meat accounted for nearly 40 percent of global meat production, with Asia as the largest poultry meat region, contributing over 38 percent of the global output (FAO, 2022). In the Philippines, chicken production reached 1.437 million MT in 2022, making it the primary source of protein, followed by pork and beef. However, the broiler chicken industry faces challenges related to increasing feed costs, which constitute a significant portion of production expenses. Factors such as inflation, supply chain disruptions, grain shortages, and adverse weather conditions contribute to the financial difficulties experienced by poultry producers (Aho, 2023). To address these economic pressures, the search for locally available and affordable feed ingredients that do not compete with human consumption becomes vital. Consequently, there is growing interest in utilizing agro-industrial by-products as alternatives to traditional feed ingredients (Vastolo et al., 2022).
Devi and Diarra (2021) highlighted that agro-industrial by-products, including discarded roots, leaves, peels, and pulp, are often wasted or dumped in landfills in various developing regions. Nevertheless, these by-products have the potential to serve as replacements for costly feed ingredients in livestock feeding. Notably, among various agro-industrial crops, cassava (Manihot esculenta Crantz) and its by-products emerge as a standout option due to their regional abundance and rich nutritional composition (Omede, 2017). Recognizing the benefits, Ogbuewu and Mbajiorgu (2022) proposed that incorporating cassava into chicken diets would not only curtail post-harvest wastage but also reduce the soaring costs of poultry feed. Therefore, utilizing cassava and its by-products as broiler feed offers a promising and sustainable solution that is accessible to the industry.
Cassava is the world's third-largest carbohydrate source and the sixth-most important food crop globally (Omondi, 2020). It has intrinsic agricultural advantages and shows tremendous potential in addressing the nutritional needs of rapidly rising populations, given its adaptability as a food source for both people and animals (Waisundara, 2018). Introduced to Asia during the late eighteenth century, cassava has since gained remarkable popularity, particularly in upland environments, with Cambodia, Indonesia, Thailand, and Vietnam emerging as prominent global producers and exporters (Aye, 2017). In the Philippines, locally known as "kamoteng kahoy", cassava thrives under challenging soil conditions, displaying the ability to yield substantial harvests with minimal or no farm inputs (Onsay, 2021). Notably, in the last quarter of 2022, cassava claimed the highest production volume among other root crops in the country, reaching 805.11 thousand metric tons (PSA, 2022). While the primary focus of cassava cultivation lies in its underground starchy tuberous roots, the full potential of its by-products remains largely unexplored, presenting an untapped nutritional resource for supplementing livestock and poultry feeds in the Philippines.
Chang'a et al. (2020) conducted a study demonstrating the feasibility of utilizing cassava as a replacement for corn as a feed ingredient at low levels (< 50%), without compromising growth performance in animals. Additionally, recent literature has explored the utilization of various cassava by-products such as cassava tuber (Anyaegbu et al., 2021), cassava stem (Ojo et al., 2022), cassava pulp (Okrathok & Khempaka, 2020; Sugiharto et al., 2019), cassava peel (Dayal et al., 2018; Ehebha & Eguaoje, 2018), cassava roots (Yadav et al., 2019; Egbune et al., 2023), and cassava distillers' waste (Anyachor, 2020). Other than these by-products, the use of cassava leaves as a feed additive in broiler diets has also been explored. However, recommendations regarding its optimal utilization have been variable.
Cassava leaves, similar to other dark green leaves, possess high nutritional value, being a rich source of protein (140–400 g/kg DM), minerals, vitamins B1, B2, C, and carotenes, and containing all essential amino acids except methionine and tryptophan (Chauynarong et al., 2009; Sudarman et al., 2017). Using cassava leaf silage as an additive in ruminant feed, particularly for sheep, has demonstrated promising results (Marjuki et al., 2008). It has been observed to elevate the intake of digestible crude protein, bolster nitrogen retention, and foster daily weight increments between 41.4 to 50.0 grams per head each day. This underscores the potential advantages of integrating cassava leaf silage into livestock feeding programs.
However, it is essential to note that cassava leaves carry hydrocyanic acid (HCN), a compound recognized as an anti-nutrient (Cereda & Mattos, 1996). Fresh cassava leaves typically have an average HCN content of 1436 mg/kg, but this content significantly decreases to 173 mg/kg when the leaves are dried in the sun (Ravindran et al., 1987). Sun-drying is a widely practiced and effective method for reducing the cyanide content of cassava leaves, as it allows for prolonged contact between the cyanide and linamarase, leading to the breakdown of cyanide compounds (Padmaja & Steinkraus, 1995). In addition, a previous study has shown that extended sun-drying can remove approximately 90% of the initial cyanide content in cassava leaves (Eruvbetine et al., 2003).
Furthermore, Iheukwumere et al. (2008) researched to investigate the impact of sun-dried cassava leaf meal (CLM) on the growth performance of broiler chickens. The chemical composition analysis of CLM showed the following percentages: 25.30% dry matter, 25.10% crude protein, 11.40% crude fiber, 12.70% ether extract, 46.10% NFE (nitrogen-free extract), 9.10% ash, 4.50% gross energy kcal/kg, 1.40% calcium, and 0.30% phosphorus percentage. The study suggests incorporating a 5% proportion of cassava leaf meal into broiler finisher diets, as it does not lead to any detrimental outcomes. These findings suggest that CLM has potential as a supplemental ingredient in poultry feed due to its relatively high protein content, moderate fiber content, and the presence of essential nutrients such as calcium and phosphorus.
In relation to this, Lyayi & Okhanhkuele (2004) conducted a study showing that including cassava leaf meal (CLM) up to a 5% level in broiler diets led to significant improvements in feed intake and body weight gain, with no impact on blood hematological parameters. Furthermore, CLM supplementation resulted in reduced feed costs and weekly feed costs per unit weight of the birds. Conversely, higher levels of CLM were found to have negative effects, including decreased weight and feed intake, average daily weight gain, and a less-than-optimal feed conversion ratio. There is a clear need for additional investigation to identify the precise proportion of CLM to be used as a supplementary feed, intending to balance both economic viability and effective growth results in broiler chickens.
In the context of broiler production in the Philippines, there exists a research gap that needs to be addressed: the need to update and validate previous literature. Previous research conducted by Bengson et al. (1986) demonstrated that feeding broilers in the finisher stage with 5–10% inclusion of cassava leaves did not negatively impact broiler weight while reducing feed costs compared to the control group. However, this study was outdated and needed validation. To date, according to the extent of existing published literature, there has not been any research that takes into account the use of cassava leaf meal (CLM) as a supplementary feed for broiler chickens in the country. The importance of this study lies in determining the appropriate levels of cassava leaf meal (CLM) in broiler feeds, with the aim of reducing agro-industrial waste and minimizing feed costs. Therefore, the primary objective of this study is to investigate the impact of different levels of cassava leaf meal as a supplemental feed on broiler growth parameters, as well as carcass quality and cut-up yield.