**1. Introduction**

Livestock production is rapidly increasing due to population growth, changing lifestyles, and dietary habits in developed industrialized countries. It accounts for approximately 40% of the gross value of agricultural products. Projections indicate that total demand for animal products in developing countries will double by 2030 [1]. Considering this issue and with the aim of dealing with food insecurity and strengthening sustainable agriculture, it is possible to use feeding strategies and feedstuffs that are able to increase livestock productivity and have fewer environmental effects compared to conventional livestock production [2]. In addition to reducing the environmental impacts associated with animal feed production,

valorizing plant by-products for feed formulation can maximize resource efficiencies and helps the competitiveness of feed manufacturers by making available of more sustainable raw materials that could reduce dependence on current raw materials [3]. Plant by-products (PBP) include a wide range of secondary residues produced from the industrial processing of plants into valuable commercial products [4]. These by-products are considered safe and widely accepted as animal feed [5]. These by-products include residues from food factories, fruit and vegetable wastes, and grain harvesting by-products. However, the use of plant waste as animal feed has limitations arising from the processes of agricultural products transformation industries, which can affect the possibility of evaluating its nutritional value. For example, its high water content, which is frequently greater than 80%, makes it more difficult and can hasten the spread of microbiological contamination [6]. On the other hand, the use of PBP in animal nutrition is limited due to restrictions such as diversity in nutrient composition and technical requirements for storage, which are necessary to stabilize the product and reduce seasonal availability of resources. Furthermore, preservation methods such as thermal processing can be expensive and diminish the environmental sustainability of PBP feed [5]. Also, the lack of efficient storage strategies is a fundamental barrier that limits the use of PBP in animal feeding, as their intrinsic instability causes quick quality deterioration and severe changes in nutritional composition [7]. This chapter provides information on some agricultural postharvest residues, their chemical composition, processing methods, nutritional value, and guidelines for including PBP in livestock diets. It also covers aspects related to the use of such post-harvest waste as a substrate for the production of value-added products. It is expected that this chapter will promote conversion of agricultural waste into valuable resources and help create opportunities for development. The recycling of these resources saves livestock feed and also reduces the environmental pollution associated with the disposal of PBP.

## **2. Grape pomace**

Grapes are one of the most widely grown crops in the world, with an expected production of more than 79 million tons in 2018 [8]. Grape seeds have a significant amount of oil, which contains large amounts of unsaturated fatty acids, more than 80% of which include linoleic acid (**Figure 1**) [9].

Due to the presence of antioxidant substances such as flavonoids, grape pomace plays an important role in preventing the phenomenon of oxidation by removing free radicals produced from the environment under heat stress [10]. Proanthocyanidins of grape seed extract act as antioxidants in poultry feed, improve the performance of broiler chickens, and treat clinical symptoms caused by oxidative stress caused by Eimeria tenella infection [11]. Grape pomace can be used in animal nutrition, so that the use of its extract in amounts of 62 and 92 mg in the diet of broiler chickens from the age of 3 to 6 weeks prevented the lipid oxidation of the chicken carcasses during their storage in the refrigerator [12]. When grape pomace is fed to cattle as a dietary supplement, it can potentially increase the oxidative stability of beef products by increasing intestinal absorption and transfer of polyphenolic compounds to meat [13]. It has been reported that the use of grape pomace up to 10% of the ration of fattening lambs has no negative effects on the growth performance of lambs (**Figures 2** and **3**) [15].

*New Advances in Postharvest Technology: An Overview for Feed Production from Postharvest… DOI: http://dx.doi.org/10.5772/intechopen.111539*

**Figure 1.** *Grape plant.*

The effects of grape pomace on the quality and characteristics of fatty acids in meat samples obtained from lactating lambs were investigated in the ewe's diet. The results revealed that grape pomace incorporation did not have any negative effect on the carcasses but improved the water holding capacity [16]. Compared to diets lacking naturally occurring antioxidants, adding antioxidants such polyphenol-rich grape by-products to animal diets enhances meat quality while also preventing oxidation [17]. The appropriate use of grape pomace could increase the growth and production rate and reduce the feed conversion ratio (FCR) in Afshari fattening lambs [18]. Also, in another report, the use of grape pomace resulted in an increase in voluntary feed intake, growth rate, and a decrease in FCR in fattening lambs [19].

#### **Figure 3.** *Components of grape pomace [14].*

**Figure 4.** *Pomegranate plant.*
