Environmental and Nutritional Value of Fruit and Vegetable Peels as Animal Feed: A Comprehensive Review
Funding: The authors received no specific funding for this work.
ABSTRACT
Fruit and vegetable peels are often regarded as waste, leading to their disposal in landfills. As a result, methane gas emissions during the decomposition of waste lead to the loss of potentially valuable resources. Nonetheless, these peels are an abundant source of nutrients, minerals, and vitamins such as dietary fiber, anthocyanins, ascorbic acid, and phenolic compounds, which can enhance animal health and productivity and, as a result, increase the milk and meat production of livestock as well as the drawing power of draught animals. From an environmental perspective, the utilization of peels for animal feed can significantly reduce organic waste accumulation, decrease greenhouse gas emissions associated with waste decomposition, and lower the dependency on conventional feed ingredients such as grains, which are often produced through resource-intensive agricultural practices. To date, no comprehensive review has been found on the nutritional and environmental impact of fruit and vegetable peels as animal feed. This paper aims to explore the nutritional and environmental impact of various kinds of fruit and vegetable peels.
1 Introduction
Fruit and vegetable peels with their environmental and nutritional qualities of being animal feeds are being considered under the systems of sustainable livestock farming. The rising demand for animal protein (50%) has resulted in an intensification of livestock production worldwide, which has, in turn, resulted in an increase in the cost of fodder as well as a depletion of natural resources [1-3]. The utilization of alternative feed sources for livestock has gained attention as a strategy that is both sustainable and effective in addressing these issues [4, 5]. The antioxidant-rich fruits, such as mango, citrus, pineapple, apple, pomegranate, watermelon, grapes, banana, litchi, etc., and vegetables, such as radish, potato, onion, peas, carrot, brinjal, pumpkin, cassava, bottle gourd, etc., are valuable not only for their nutritional properties but also for the potential use of their peels in animal feed. Because of their high nutritive value and abundant availability, they have been suggested as possible sources of food for animals [6-8]. Moreover, the municipal solid waste can also be managed, which is a major challenge in Pakistan, as approximately 36 million tons of food waste is produced per year in the country, which is predicted to increase by 30 times in the forthcoming years. The objective of this review is to overview the nutritional importance of fruit and vegetable peels as a feed source for domestic animals while still achieving sustainable nutrition.
2 Nutritional and Functional Benefits of Fruit and Vegetable Peels in Animal Feed
The peels of fruits and vegetables are rich in fiber, carbohydrates, proteins, antioxidants, nutrients, vitamins, and minerals (Figure 1) and are essential for animal growth and health [9, 10]. These peels have varying nutritional value considering the type of fruit or vegetable, maturity stage or the processing techniques used. For instance, apple peels contain relatively higher dietary fiber, vitamin C, as well as antioxidants, than the pulp [11]. Similarly, orange peels have been found to have higher contents of fiber, carotenoids, and flavonoids [12]. Pineapple peels contain a good amount of fiber, protein, and carbohydrates, thus an excellent source of feed for ruminants [13]. Numerous studies have shown that citrus and grape peel of about 150 g kg−1 dry weight (DW), were added into animal diets [14, 15]. However, the astringency incorporated by proanthocyanidins, through their interaction with salivary proteins, the feed becomes less palatable. Additionally, such feed contains high fiber content resulting in the reduced intake of dry matter [16]. Recent studies point out that feeding ruminant at levels less than 150 g kg−1 DW of citrus and winery peels have the ability to increase the dry matter intake because of the improvements in flavor, odor and taste [14, 17-20]. Earlier research studies stated that feeding lactating holstein cows with ensiled apple peel at the rate of 15% had detrimental effect on the performance [21]. Fang et al. [22] suggested that the inclusion level of apple pomace should be restricted at 44 g kg−1. Tomato waste can be used fresh, ensiled, or sun-dried, though its high moisture content necessitates mixing with wheat, rice, or corn stovers at a 70:30 ratio for ensiling. Supplementation of dried tomato peel up to 32.5% in the concentrate mixtures of multiparous dairy cows feed resulted in better growth and milk production [23]. For sheep diets, it was observed that the inclusion levels of tomato pomace should not exceed 40% [19]. The nutrient content in the peels of various fruits is presented in Table 1 and vegetables in Table 2.
Utilization of fruit and vegetable peels as sustainable animal feed offers a multifaceted solution to enhance livestock nutrition while promoting environmental sustainability.
| No. | Fruit | Nutrient | Concentration (100 g−1 DW) | References |
|---|---|---|---|---|
| 1. | Apple | Fiber | 35–40 g | [9, 24] |
| Vitamin C | 4.6–10.3 mg | |||
| Total antioxidants | 60% | |||
| 2. | Orange | Fiber | 4–6 g | [25, 26] |
| Flavonoids | 6.4–49.1 mg | |||
| Carotenoids | 42–168 μg | |||
| 3. | Pineapple | Fiber | 40–45 g | [27] |
| Protein | 3.2–3.9 g | |||
| Carbohydrates | 13.0 g | |||
| 4. | Banana | Fiber | 50–55 g | [28, 29] |
| Potassium | 271–400 mg | |||
| Magnesium | 16–30 mg | |||
| 5. | Lemon | Fiber | 15 g | [30] |
| Vitamin C | 53.0 mg | |||
| Flavonoids | 0.7–1.0 g | |||
| 6. | Grapefruit | Fiber | 1.5 g | [31] |
| Vitamin C | 38.4 mg | |||
| Flavonoids | 1.5–2.0 g | |||
| 7. | Watermelon | Fiber | 20–25 g | [32, 33] |
| Vitamin C | 7.8–8.1 mg | |||
| Lycopene | 5.6–6.5 mg | |||
| 8. | Mango | Calcium | 0.11 g | [34, 35] |
| Protein | 9.68 g | |||
| Fiber | 15–20 g | |||
| 9. | Pomegranate | Fiber | 3–4 g | [36] |
| Potassium | 200–250 mg | |||
| Vitamin C | 10–12 mg | |||
| 10. | Litchi | Potassium | 170–180 mg | [37] |
| Vitamin C | 70–85 mg | |||
| Copper | 0.14–0.16 mg | |||
| 11. | Persimmon | Potassium | 160–200 mg | [38] |
| Vitamin C | 7–16 mg | |||
| Vitamin A | 80–120 µg |
- Abbreviation: DW = dry weight.
| No. | Vegetable | Nutrient | Concentration (100 g−1 DW) | References |
|---|---|---|---|---|
| 1. | Potato | Starch | 15–20 g | [39] |
| Fiber | 19.7 mg | |||
| Potassium | 421 mg | |||
| 2. | Sweet potato | Fiber | 3 g | [40, 41] |
| Vitamin C | 29.8 mg | |||
| Beta-carotene | 8500 μg | |||
| 3. | Radish | Fiber | 1.6 g | [35] |
| Potassium | 233 mg | |||
| Calcium | 58 mg | |||
| 4. | Pea | Protein | 5.6 g | [42] |
| Fiber | 4.3 g | |||
| Vitamin C | 40 mg | |||
| 5. | Carrot | Fiber | 2.8 g | [43, 44] |
| Beta-carotene | 8000–8500 µg | |||
| Vitamin K | 13.2 µg | |||
| 6. | Brinjal | Fiber | 3.5 g | [33] |
| Potassium | 217 mg | |||
| Vitamin C | 2.2 mg | |||
| 7. | Bottle gourd | Potassium | 160–180 mg | [45, 46] |
| Vitamin C | 10 mg | |||
| Riboflavin | 0.1–0.2 mg | |||
| 8. | Pumpkin | Fiber | 1.0–1.5 g | [47] |
| Beta-carotene | 3000–3500 µg | |||
| Vitamin A | 400–450 µg | |||
| 9. | Bitter gourd | Potassium | 296 mg | [48] |
| Vitamin C | 80–90 mg | |||
| Iron | 2.0–2.5 mg | |||
| 10. | Cassava | Starch | 34–35 g | [49] |
| Fiber | 1.5–2.0 g | |||
| Vitamin C | 20.6 mg | |||
| 11. | Onion | Fiber | 1.7–2.0 g | [50] |
| Potassium | 140–150 mg | |||
| Vitamin C | 7–12 mg |
- Abbreviation: DW = dry weight.
The peels of fruits and vegetables can be used for feeding different kinds of animals, such as poultry, fish, ruminants, and nonruminants. The utilization of these peels as animal feed has several advantages, including nutritional benefits such as carbohydrates, fiber, vitamins, minerals, proteins, antioxidants and fats, and functional benefits such as flavor enhancement, variety, environmental and economic value, reduction of waste, conservation of resources, and sustainability (Figure 1) [51-60].
2.1 Nutritional Benefits
2.1.1 Carbohydrates and Fiber
Fruits and vegetable peels are abundant in carbohydrates, particularly in the form of dietary fiber [61]. This fiber plays a crucial role in digestive health, especially for ruminant animals, by promoting healthy gut bacteria and improving digestion [62]. For nonruminants, fiber aids in maintaining gastrointestinal motility [63]. The high fiber content in peels like those from apples, citrus fruits, and potatoes helps in controlling glucose levels and can support energy balance in animals [64]. Potato peels are known for their high carbohydrate content, making them a source of energy for animals [65]. Orange peels, on the other hand, contain pectin, a soluble fiber that can enhance gut health [61].
2.1.2 Vitamins and Minerals
Fruit and vegetable peels are rich in vitamins, particularly vitamins C, E, and various B-complex [66]. These vitamins are critical for the overall well-being of animals, supporting immune function, skin health, and reproduction [67]. Citrus fruit peels such as oranges and lemons are excellent sources of vitamin C, which enhances immune function and acts as an antioxidant in animals [68]. Vitamin E is present in peels such as those from carrots and sweet potatoes [44]. It supports skin health and reproductive efficiency and acts as a natural antioxidant [69]. Vitamin B-complex is found in banana and potato peels and is vital for energy metabolism, nervous system function, and growth in animals [70].
Minerals such as calcium, potassium, magnesium, and phosphorus are often present in fruit and vegetable peels [69]. These minerals are crucial for bone health, muscle function, and metabolic processes in animals [71, 72]. The peels from bananas and citrus fruits are particularly high in potassium, supporting heart health and muscle function [73]. Similarly, peels such as those from carrots and apples contain calcium, contributing to the bone strength of livestock [74]. Magnesium and phosphorus are abundant in potato and tomato peels, aiding in energy production, DNA synthesis, and skeletal development in animals [71].
2.1.3 Proteins and Antioxidants
While fruit peels are generally low in protein compared to traditional animal feed sources, they still contain a moderate amount of essential amino acids [6]. Peels from vegetables such as peas, beans, and certain legumes can provide a higher protein content, beneficial for growth and muscle development in livestock and poultry [75]. Citrus and banana peels contain smaller amounts of proteins that contribute to the overall dietary requirements of animals when combined with other feeds [76].
Fruits and vegetable peels are often rich in antioxidants such as flavonoids, polyphenols, and carotenoids [77]. These compounds help protect animals from oxidative stress, which can damage cells and lead to various health problems [78]. Antioxidants improve the overall health of animals by reducing inflammation, enhancing immune responses, and promoting longevity [79]. Apple and citrus peels contain high levels of polyphenols, whereas carrot and sweet potato peels are rich in beta-carotene, a precursor to vitamin A, which supports vision and immune health in animals [80].
2.1.4 Fats
Some fruit and vegetable peels also contain small amounts of essential fatty acids, particularly in peels such as avocado and coconut [81]. These fatty acids, including omega-3 and omega-6, are vital for maintaining skin and coat health in animals and can improve reproductive health and reduce inflammation [82]. Avocado peels contain beneficial fatty acids that can support coat health in livestock and poultry, although their use should be moderated due to potential toxicity in large quantities [83].
2.2 Functional Benefits
2.2.1 Flavor Enhancement
Fruit and vegetable peels are rich in natural flavor compounds, such as essential oils, phenolic compounds, and organic acids, that can contribute to the overall taste and aroma of feed [84]. For example, citrus peels contain limonene, a natural flavor enhancer with a refreshing citrus scent [85], whereas apple peels are high in quercetin, a flavonoid known to impart a mild sweetness [86]. These compounds not only enhance the sensory experience for animals but may also contribute to their overall health and well-being.
Peels release aromatic compounds, which improve the smell of feed [87]. This is particularly important for animals with a strong sense of smell, such as cattle. Furthermore, the natural sugars and organic acids in peels can balance the flavors in the feed, making it more palatable [27]. For example, the sweetness from fruit peels can offset the bitterness of certain high-protein feeds. The fibrous nature of some peels, such as potato or carrot peels, can add a desirable texture to the feed, enhancing the chewing experience for animals and promoting saliva production, which aids digestion [51-60, 88].
The addition of peels to the feed not only enhances the flavor, but animals also benefit from the micronutrients and phytochemicals present in these natural sources [75]. For instance, citrus peels provide vitamin C, whereas carrot peels are rich in beta-carotene. Moreover, the animals waste less feed when it is more palatable, leading to more efficient feeding practices and reducing the cost of feed inputs. The phenolic compounds and antioxidants found in many fruit and vegetable peels not only improve flavor but also contribute to animal health [89]. These compounds, such as quercetin, hesperidin, naringin, ellagic acid, proanthocyanidins, anthocyanins, chlorogenic acid, luteolin, catechins, ferulic acid, and caffeic acid, may have antiinflammatory, antimicrobial, and immune-boosting properties [90].
As the flavor enhancement using fruit and vegetable peels is beneficial, certain factors must be considered. Some peels, such as those from potatoes, may contain compounds, such as solanine, which are harmful in large quantities [91]. Proper processing is required to remove or neutralize such compounds. Not all animals respond to flavor enhancement in the same way [92]. Although some livestock species may benefit from the added flavors, others may not show a significant change in feed consumption. The seasonal availability of certain fruit and vegetable peels may affect the consistency of flavor enhancement in feed formulations [93].
2.2.2 Variety
Fruit and vegetable peels come in a wide variety, each providing unique nutrients, flavors, and health benefits to different types of animals. For instance, citrus peels (orange, lemon, and grapefruit) are rich in vitamin C, flavonoids, and fiber [30, 94]. They are highly palatable and are known for their antioxidant properties [95]. They are particularly beneficial in enhancing the immune systems of animals, and their natural sugars make them appealing in feed formulations [9, 12, 30, 31, 68, 96-98]. Potato peels are high in starch and provide energy-dense feed options for livestock, particularly for cattle [39]. These peels are also a good source of vitamins, such as B6 and C, and minerals, such as potassium. Carrot peels are known for their high beta-carotene content. They are useful in improving the nutritional profile of feed, especially for animals that require carotenoids for their skin and coat health [39]. Carrot peels are often incorporated into the diets of horses and small ruminants. Apple peels contain high levels of dietary fiber, natural sugars, and antioxidants such as quercetin. These enhance the flavor of feed while contributing essential nutrients [9, 24]. They are commonly fed to horses, cattle, and goats, improving digestive health and energy intake. Tomato peels have a distinct umami flavor and are rich in lycopene, a potent antioxidant [99]. These peels are a valuable addition to the diet of meat-producing animals, as they contribute to better health outcomes and may improve meat quality [100].
Fruit and vegetable peels can serve as an excellent supplement for dairy cattle and goats, offering not only energy but also improving milk production [101]. The high fiber content from peels such as citrus or apple helps improve digestion, whereas the antioxidant properties support overall health, leading to enhanced milk yield and quality [9, 24-26, 30, 31]. The energy-rich and nutrient-dense nature of certain peels, such as potato and carrot, makes them ideal for meat-producing livestock, such as cattle and poultry [39, 43, 44]. These peels improve weight gain, feed conversion efficiency, and overall meat quality, offering a cost-effective alternative to conventional feed ingredients. Animals used for labor, such as horses and oxen, require a well-balanced diet that provides both energy and strength. Peels from carrots and potatoes provide the necessary carbohydrates and fiber to sustain energy levels during prolonged physical work. Additionally, the vitamins and minerals in these peels support muscle function and endurance [51-60].
2.2.3 Environmental and Economic Value
The use of fruit and vegetable peels as animal feed contributes significantly to environmental safety by reducing waste, conserving natural resources, and promoting sustainable agricultural practices [27]. In a world where environmental degradation and resource depletion are major concerns, utilizing these agricultural by-products offers an eco-friendly solution that benefits both the environment and livestock production systems [102, 103]. One of the most pressing environmental issues is food waste, and fruit and vegetable peels represent a significant portion of this waste [104, 105]. Disposing of peels in landfills leads to the release of harmful greenhouse gases, such as methane, which contribute to climate change [106]. By repurposing these peels as animal feed, the volume of organic waste sent to landfills is reduced, directly lowering methane emissions and helping mitigate global warming [107]. This practice transforms a potential environmental hazard into a valuable resource.
Moreover, the production of traditional animal feeds, particularly grain-based feeds, demands large amounts of land, water, and energy [108]. Growing crops such as maize and soybeans for livestock feed often leads to deforestation, habitat destruction, and soil degradation [109]. Substituting part of these conventional feeds with fruit and vegetable peels helps reduce the environmental footprint of livestock farming [110, 111]. The peel-based feed option requires fewer inputs, conserving water and reducing the need for extensive farmland, and thus alleviating the pressure on natural ecosystems. In addition to conserving resources, feeding livestock with fruit and vegetable peels promotes soil health. Manure from animals fed on nutrient-rich peels tends to contain higher levels of organic matter, which improves soil fertility when applied as natural fertilizer [112]. This reduces the need for synthetic fertilizers, which are known to contribute to soil and water pollution through chemical runoff. By enhancing soil quality, this practice helps maintain a balanced ecosystem, ensuring that agricultural lands remain productive and sustainable for future generations.
Water conservation is another important environmental benefit. Conventional feed production requires significant irrigation, leading to water depletion in many regions [113]. In contrast, fruit and vegetable peels often have high moisture content, which not only hydrates livestock but also reduces the reliance on external water sources for feed processing [114]. This helps preserve water resources and supports the sustainability of farming operations, especially in areas facing water scarcity.
Biodiversity also benefits from the integration of fruit and vegetable peels into animal feed [95, 115]. The reduction in the demand for monoculture crops used for animal feed lessens the strain on ecosystems and encourages more diverse agricultural landscapes [116]. This biodiversity is essential for maintaining resilient ecosystems that can adapt to climate change and other environmental stressors [117]. Furthermore, by decreasing the need for synthetic inputs and large-scale crop production, the environmental risks associated with pesticide and herbicide use are minimized, contributing to cleaner air and water.
Fruit and vegetable peels are often considered waste and are discarded [105]. Utilizing these peels as animal feed offers significant cost-effectiveness for sustainable livestock nutrition [118]. Rich in fiber, vitamins, and bioactive compounds, fruit and vegetable peels can enhance the nutritional profile of animal diets, contributing to improved health and productivity [93, 119]. Moreover, sourcing peels locally or from food processing industries reduces transportation costs, further enhancing the economic viability of using them as feed [95]. This cost-effective approach supports circular economies in agriculture by recycling waste into valuable nutritional inputs, fostering both environmental and financial sustainability [120]. Fruit and vegetable peels may contain anti-nutritional factors such as tannins, phytates, and oxalates, which can interfere with nutrients [121]. Due to the presence of a high concentration of anti-nutrients, it can bind nutrients, consequently inhibiting their digestion and availability index [122]. Nonetheless, it is evident that the right proportion of antinutrients to nutrients may reduce the negative impact on digestibility besides having health benefits [123]. However, proper processing and evaluation of peel digestibility and safety are crucial to ensure optimal benefits and prevent potential antinutritional effects [98].
2.2.4 Reduction of Waste
When peels are used as animal feed, it increases the utilization of the whole fruit or vegetable [27]. After human consumption, the peels of fruits and vegetables are typically thrown away as waste, so recycling them as livestock feed is a great way to cut down the amount of garbage produced [76]. Fruit and vegetable peels are often discarded in landfills, where they contribute to methane emissions and take up valuable space [124, 125]. By using peels as animal feed, they are diverted from the waste stream and put to a productive use [96, 97, 126]. Additionally, fruit and vegetable peels take up valuable space in landfills, which can lead to a shortage of available land for waste disposal [94, 104, 127]. By finding alternative uses for fruit and vegetable peels, we can reduce the amount of waste generated and promote more responsible consumption and production practices [128, 129].
2.2.5 Conservation of Resources
Traditional animal feed is often produced from crops such as soy and corn, which require large amounts of water, land, and other resources to grow [130]. By using fruit and vegetable peels as animal feed, we can reduce our reliance on these crops and lessen the environmental impact of animal agriculture [110, 131]. Using peels as animal feed can increase soil health, as the peels contain nutrients that can be recycled back into the soil through animal manure [81, 132, 133]. This conserves soil health by reducing the need for synthetic fertilizers and other soil amendments [134].
2.2.5.1 Sustainability
The use of fruit and vegetable peels as animal feed aligns with the global push toward sustainable agricultural practices, addressing both environmental and economic challenges [107]. As food systems continue to evolve to meet the demands of a growing population, the need to reduce waste and improve resource efficiency is critical [135]. Incorporating these by-products into animal feed not only contributes to the circular economy but also enhances the sustainability of livestock production systems.
Incorporating fruit and vegetable peels into animal feed embodies the principles of the circular economy, where waste from one process becomes a resource for another [107]. This approach promotes the efficient use of raw materials, extending the lifecycle of food resources and reducing the need for external inputs such as traditional feed grains [136]. Instead of relying solely on grain-based feeds, which require vast land, water, and energy resources, fruit and vegetable peels offer an alternative that conserves these resources [137].
Fruit and vegetable peels are often available at little to no cost, making them a highly economical alternative to conventional animal feed. Farmers can reduce their dependency on expensive feed ingredients such as grains and protein concentrates, which often come with high environmental costs in terms of land use, water consumption, and energy inputs for cultivation and transportation [130]. This shift toward peel-based feeds helps reduce the overall resource burden on the environment.
The production of conventional animal feed, especially grains, often requires large-scale monoculture farming, which can have negative impacts on soil health, biodiversity, and ecosystems [138]. By replacing or supplementing these feeds with fruit and vegetable peels, farmers can reduce the demand for monoculture crops, promoting more diverse and sustainable agricultural landscapes [139]. Furthermore, by using peels as feed, fewer crops need to be grown exclusively for animal consumption, allowing more land to be dedicated to biodiversity conservation, reforestation, or regenerative farming practices [140]. This can improve soil health by reducing over-reliance on synthetic fertilizers and pesticides, ultimately supporting more resilient ecosystems.
The carbon footprint of livestock farming is a significant concern, particularly due to the emissions associated with feed production, transportation, and animal waste management [141]. By utilizing locally sourced fruit and vegetable peels, farmers can reduce the carbon footprint of their operations. Peels, often available near food processing facilities, reduce the need for long-distance transportation, thereby lowering fuel consumption and emissions. Moreover, the production and processing of conventional feeds such as soy and maize are associated with deforestation, habitat destruction, and high energy use [142]. By replacing a portion of these feeds with peels, farmers can mitigate the negative environmental impacts associated with conventional feed production.
Fruit and vegetable peels are rich in nutrients, such as fiber, vitamins, and minerals, which not only benefit livestock but also contribute to nutrient cycling in agricultural ecosystems [95, 110]. Animals that consume peel-based feeds excrete manure that is often higher in organic matter and beneficial nutrients, improving soil fertility when used as a natural fertilizer [112]. This nutrient recycling closes the loop in food production, reducing the need for synthetic fertilizers and enhancing the sustainability of both livestock and crop farming.
3 Impact of Fruits and Vegetables Peels on Performance of Animals
The incorporation of fruit and vegetable peels into the diets of dairy, meat, and draught animals has shown tremendous potential in enhancing their performance.
3.1 Drawing Power
The drawing power of draught animals refers to their capacity to perform work, such as pulling carts, plowing fields, or transporting goods [143]. This ability is influenced by several factors, including the animal's breed, size, health, training, and the quality of its diet [144]. Feeding draught animals with nutritious feed, particularly fruit and vegetable peels, can significantly enhance their drawing power and overall performance [145].
One of the primary determinants of drawing power is the animal's muscle strength and endurance, which can be greatly influenced by its nutritional intake. Incorporating fruit and vegetable peels into their diet provides essential nutrients, such as carbohydrates, proteins, vitamins, and minerals, which contribute to muscle development and energy production [146]. For instance, the high carbohydrate content in certain peels can supply the energy needed for sustained work, allowing draught animals to perform more efficiently and effectively.
Moreover, the fiber present in fruit and vegetable peels aids digestion and promotes gut health [147]. A healthy digestive system ensures that animals can efficiently convert feed into energy, thereby enhancing their overall performance [148]. Animals with improved digestive health are less likely to experience fatigue and other health issues, which can detract from their working capacity [149]. Furthermore, the inclusion of peels in their diet can bolster the immune system, reducing the incidence of diseases that may hinder performance and drawing power [150].
The psychological aspect of an animal's ability to work should not be overlooked either. A well-nourished animal tends to exhibit better temperament and stamina, which are crucial for tasks requiring endurance [151]. Training and proper handling, alongside a nutritious diet, play a significant role in maximizing drawing power [152]. Draught animals that are well-cared for and fed with energy-dense feeds, including fruit and vegetable peels, tend to be more willing and capable of performing demanding tasks.
3.2 Meat Production
The integration of fruit and vegetable peels into the diets of livestock significantly enhances meat production, offering a sustainable alternative to traditional feed sources [27, 110]. These peels are rich in essential nutrients, including vitamins, minerals, fibers, and antioxidants, which play a crucial role in improving the overall health and productivity of meat animals [120, 153, 154]. By incorporating peels such as those from citrus fruits, carrots, or pumpkins into animal diets, farmers can observe notable improvements in growth rates and feed efficiency. The nutritional content of these peels not only provides energy but also supports the development of lean muscle mass, resulting in higher-quality meat [155]. Supplementation of dietary banana peel at a level of 20% increased feed intake, growth rate, and the average daily weight gain in sheep [156]. The sun-dried ripe plantain peels can possibly replace 75%–100% of maize in weaned rabbits' diets with a good profit margin. As the inclusion rates exceeded 30%, the compromised daily weight gain and feed conversion efficiency were observed [157]. A study found that the inclusion of fruit and vegetable peels in calf diets resulted in improved average daily gain, indicating that such by-products can be utilized [158].
Research studies indicate that livestock fed with fruit and vegetable peels often demonstrate better feed conversion ratios, allowing them to grow faster while consuming less feed [27, 110]. This is particularly beneficial in meat production, where the cost of feed is a significant expense for farmers. The use of peels as a feed source can help mitigate these costs, enhancing the economic viability of meat production systems. Additionally, the fiber content in peels contributes to improved gut health, which is essential for nutrient absorption and overall animal well-being. A healthy digestive system leads to more efficient nutrient utilization, further boosting growth and productivity.
3.3 Milk Production
The fruit and vegetable peels are rich in essential nutrients, including vitamins, minerals, fibers, and antioxidants, which contribute to improved health and productivity in livestock [93, 101]. Feeding dairy animals with peels can lead to an increase in milk yield and quality [159]. For instance, the addition of peels, such as those from citrus fruits, apples, or carrots, has been associated with higher levels of beneficial compounds in milk, such as omega-3 fatty acids and vitamins, which not only enhance the nutritional profile of the milk but also contribute to better health outcomes for consumers [9, 24-26, 43, 44].
Moreover, the fiber content in fruit and vegetable peels aids in digestion, promoting a healthier gut microbiome in dairy cows [110]. This results in improved feed conversion efficiency, allowing animals to extract more nutrients from their feed. Enhanced digestion is crucial for maximizing milk production, as well-nourished animals are better able to sustain lactation [160]. Additionally, the antioxidant properties of certain peels can bolster the immune system of dairy cows, reducing the incidence of diseases that may negatively affect milk yield [161].
The above review of literature validates the significant environmental and nutritional benefits of utilizing fruit and vegetable peels as animal feed. This practice not only reduces waste and promotes sustainable agricultural practices but also enhances the one-health concept (human, animal, and environmental health) and productivity of livestock. The incorporation of these nutrient-rich by-products into animal diets contributes to improved meat and milk production, increased drawing power in draught animals, and overall better animal welfare. As the demand for sustainable food systems grows, leveraging the potential of fruit and vegetable peels represents a promising strategy for optimizing animal nutrition while minimizing environmental impact.
4 Fruits and Vegetable Peels: A Pathway to One Health (Human, Animal, and Environmental Well-Being)
The concept of one health recognizes the interdependence of human, animal, and environmental health. In this framework, fruit and vegetable peels play a vital role when utilized as animal feed, contributing to the overall well-being of all three components (Figure 2). Their inclusion in livestock diets not only enhances the nutritional quality of animal products but also supports sustainable farming practices that benefit the environment.
Utilizing fruit and vegetable peels as animal feed significantly influences interconnected factors within the One Health framework—encompassing human, animal, and environmental well-being. This approach enhances human health by promoting sustainable dietary practices and reducing food waste, which can lead to improved nutrition. For animal health, incorporating these peels into feed provides essential nutrients, encourages healthier livestock, and reduces reliance on commercial feed sources, which can be resource-intensive. This practice also aids environmental health by minimizing waste and lowering carbon footprints associated with traditional waste disposal methods. Overall, this integrated approach demonstrates the linkage among food security, diet, and social determinants, emphasizing the importance of holistic concerns in public health strategies.
When animals consume peels rich in nutrients such as vitamins, fibers, and antioxidants, the resulting livestock products like milk, meat, and eggs become nutritionally enriched [75, 95]. This provides healthier food sources for humans, as the animals' enhanced diets translate into better-quality products. For instance, livestock that consume citrus or apple peels—both rich in antioxidants—produce dairy and meat with added nutritional benefits [9, 24-26, 30, 31]. This can contribute to addressing malnutrition, particularly in regions where access to nutrient-rich foods is limited, while also offering safer, more nutritious animal-based products for human consumption.
On the animal side, peels improve digestion and overall health [61, 75]. Fiber from fruit and vegetable peels aids in better feed efficiency and nutrient absorption, leading to healthier and more productive animals [27, 98]. Additionally, bioactive compounds in these peels strengthen the animals' immune systems, reducing their vulnerability to diseases and lowering the need for antibiotics and synthetic growth enhancers [119]. Healthier animals require fewer medical interventions, which promotes more natural livestock farming practices and reduces the risk of antimicrobial resistance—a concern for both animal and human health [162].
Beyond animal health, the environmental benefits of using fruit and vegetable peels in feed are significant. This practice reduces food waste by diverting organic by-products that would otherwise end up in landfills, thereby cutting down on methane emissions from decomposing waste [114, 163]. Utilizing peels also reduces the need for resource-intensive traditional animal feeds, such as grains, conserving water, land, and energy. This lessens the pressure on ecosystems and promotes biodiversity by decreasing the demand for large-scale monoculture farming, which often leads to deforestation and habitat loss.
Moreover, the manure produced by animals fed on nutrient-dense peels is rich in organic matter and essential nutrients, enhancing soil fertility and reducing the reliance on synthetic fertilizers [164]. Healthier soils, in turn, improve plant growth, creating a sustainable feedback loop that benefits both crop and livestock production. This nutrient cycling between animals and plants fosters a more resilient agricultural system, ensuring long-term sustainability [165].
5 Collection and Processing of Fruit and Vegetable Peels Waste
5.1 Conventional Approaches
5.1.1 Animal Feeding
It is important to carefully assess this option because not all animals can consume all the food/residue [104, 166]. Moreover, there is a possibility that residues destined for animal feeding may have harmful substances that transmit diseases or might be unbalanced from a dietary point of view. However, the transportation cost and conservation expenses make this option unfeasible [167].
5.1.2 Landfilling
It is the most popular and simple method of disposing of solid wastes. This is mostly owing to its great biodegradability combined with a high nutritional content [168]. Methane from landfills, caused by the anaerobic biological decay of deposited organic matter, is the third greatest human source of atmospheric methane emissions, accounting for approximately 800 million tons of CO2 [169]. A major environmental problem related to landfilling is leachate formation. It is primarily caused by rainwater seepage through the waste layers into the landfill's bottom [170]. The appropriate facilities should be used to treat leachate. They could be treated by municipal wastewater treatment plants based on their composition.
5.1.3 Anaerobic Digestion
Anaerobic digestion is an established technique for handling fruit and vegetable waste in treatment plants [171]. Its application to fruit and vegetable waste valorization has huge potential, although its implementation is low.
5.1.4 Composting and Vermicomposting
Composting is effectively used to manage organic waste, making it an ideal option for fruit and vegetable waste [172]. The critical factors affecting this process are moisture content, aeration rate, pH, particle size, porosity, and C/N ratio. Vermicomposting has been developed more recently to produce biofertilizers from food waste [173].
5.1.5 Thermal Treatments
Combustion or incineration is a technique that can be considered beneficial since it significantly lowers the amount of waste material that is ultimately disposed off, and hence extends the life of landfills [104].
5.2 Food Waste Valorization: A Recently Developed Approach
Fruit and vegetable waste valorization involve extraction of enzymes, bioactive compounds, biofuels, and bioplastics from food waste [173]. Valorization of fruit and vegetable peels as animal feed on a large scale involves multifaceted challenges that span logistical, biochemical, and operational domains [174]. The logistics domain involves the collection, transportation, and centralized processing of peels from dispersed sources such as markets, processing plants, and farms, demanding a well-coordinated infrastructure. The perishable nature of these by-products, particularly those with high sugar content, such as citrus or banana peels, aggravates storage and transport challenges, as they are prone to microbial spoilage and fermentation [7]. This necessitates rapid stabilization through drying, ensiling, or other preservation techniques, which require significant energy inputs and may not always be economically viable. Biochemically, certain peels contain antinutritional factors, such as tannins, alkaloids, or enzyme inhibitors that can interfere with nutrient absorption or exhibit toxicity, necessitating pre-treatment or detoxification processes to ensure feed safety and efficacy [175]. Moreover, the seasonal variability of peel availability introduces inconsistencies in supply volume and nutrient composition, complicating the formulation of balanced animal feed. Developing scalable solutions that address these issues, including robust preservation technologies and adaptive supply chain models, is critical for harnessing the full potential of fruit and vegetable peels as a sustainable feed resource.
6 Conclusion and Future Perspective
The utilization of fruit and vegetable peels as animal feed presents a transformative opportunity in the realm of sustainable agriculture. The compelling evidence gathered from various past studies highlights not only the nutritional enrichment these peels offer to livestock but also their role in reducing food waste and enhancing environmental sustainability. Animal health, productivity, and well-being can be greatly enhanced by repurposing the peels otherwise to be discarded, resulting in a more effective food system that is beneficial for both farmers and consumers. Looking ahead, the future of integrating fruit and vegetable peels into animal feed appears bright and open for experimentation. However, there are some limitations that are obvious and should be acknowledged. The seasonal and regional differences resulting in variation in the nutrient composition of peels, the possibility of antinutritional factors, and the difficulty in processing and preserving may become challenging in the utilization of feed consistently. Different processing strategies can be used to control the waste from fruits and vegetables, but these days, finding a suitable balance between conventional and new waste management techniques for value-addition is the most effective strategy of action.
Continued research is essential to optimize feed formulations, ensuring that livestock receive a balanced diet that maximizes the benefits of these by-products. Additionally, expanding awareness and education among farmers regarding the economic and environmental advantages of this practice can foster widespread adoption. Innovations in processing techniques and feed delivery systems could further enhance the efficacy of peel utilization in livestock diets. Understanding the potential of fruit and vegetable peels is a step toward a more resilient and sustainable agricultural system. It also helps us achieve ecological goals by promoting a healthier life for mankind and animals and, eventually, a healthier planet. By working together, we can take advantage of this chance to build a future in which resource conservation, waste reduction, and the welfare of people, animals, and the environment are top priorities.
Author Contributions
Muhammad Wasim Haider: conceptualization, methodology, writing – original draft, validation, investigation, project administration, data curation, writing – review and editing, visualization, supervision. Syed Mohsin Abbas: validation, investigation, methodology, project administration, conceptualization, writing – original draft, supervision. Muhammad Ahmad Saeed: methodology, validation, investigation, project administration, conceptualization, writing – original draft. Umar Farooq: validation, methodology, investigation, project administration, writing – original draft, conceptualization. Muhammad Waseem: writing – original draft, investigation, methodology, software, conceptualization, formal analysis, validation, project administration, visualization, supervision. Muhammad Adil: investigation, writing – review and editing, validation, methodology, project administration, data curation. Muhammad Rizwan Javed: investigation, writing – review and editing, validation, methodology, project administration, data curation. Izhar ul Haq: investigation, methodology, validation, project administration, conceptualization, writing – original draft. Crossby Osei Tutu: investigation, writing – review and editing, visualization, validation, formal analysis, methodology, conceptualization, writing – original draft, resources, supervision.
Conflicts of Interest
The authors declare no conflicts of interest.
Open Research
Data Availability Statement
The data associated with this study are included in article/referenced in article.
