The impact of potato chips waste addition on fermentation and in vitro digestibility of corn silage

1 Introduction

Livestock sector plays a crucial role in the Turkish economy (Akbay and Boz, 2005). The use of silage as a livestock feed in recent years has contributed to a decrease in feed costs and an improvement in animal health (Aslim and Daniş, 2021). The expense associated with feeding livestock is the most significant financial burden in the country (Boğa and Çevik, 2012). One of the most challenging aspects pertaining to feed expenses is in the exorbitant cost associated with quality roughage (Cakan and Tıpı, 2023).

Approximately 50 % of the global potato harvest is consumed in its fresh form, while the remaining is processed into various products such as potato chips, French fries, potato flour, potato starch, potato seed, and animal feed (Mickiewicz et al., 2022). A substantial proportion of the potatoes processed by the starch industry is disposed away as waste (Oda et al., 2002). Consequently, there exists significant potential for feed production by recycling this waste material into animal feed (Pen et al., 2006). The potato industry in Türkiye has seen significant growth in recent years, resulting in an increased range of potato products available to customers, such as potato chips and frozen potatoes (Çapoğlu and Özden, 2023). The by-products derived from potato business, i.e., chips products, frozen potato products, and potato skins, exhibit varying compositions on a dry matter basis. These compositions generally consist of starch ranging from 3 % to 55.9 %, neutral detergent fiber ranging from 20 % to 40.7 %, and acid detergent fiber ranging from 6.2 % to 31.2 %. Based on available information, the crude oil contents of these byproducts range from 2.9 to 6.9 % (Aibibula et al., 2007; Nelson, 2010).

Various studies have been carried out on alternative feed sources in the world and in Türkiye during recent years (Jalal et al., 2023; Şenyüz and Karsli, 2022). Industrial by-products should also be evaluated as an alternative feed source. Industrial by-products that contain enough nutrients and have a certain production capacity are important for the nutrition of ruminants (Charmley et al., 2006; Şenyüz and Karsli, 2022; Yani et al., 2015). Several industrial by-products are used successfully in animal nutrition in Türkiye. One of the most important agricultural and industrial wastes is potato waste and residues (Doğan Daş et al., 2023; Kara et al., 2023). These products appear as agricultural waste during the production phase and as shells, splinters, and pulp, which are produced because of processing in industry. Potatoes and potato waste have low protein and high energy values, which depend on the type of waste, the time spent cleaning, the amount of residue remaining in the wash water and the amount of skin residue the potato contains. In addition, the wastes of products such as potato flakes, French fries, and chips, which are produced during the processing of dried potato products, have a good nutrient content, and are easily used in beef cattle feed (Hinman and Sauter, 1978).

The objective of this study was to investigate the impact of incorporating PCW into corn silage on the quality of the silage, fermentation characteristics, and in vitro digestibility.

2 Materials and Methods

3 Results

Table 1 displays the results of the nutritional analyses performed on the corn plant material used as silage and PCW included as an additive in the research. Table 2 displays the nutritional contents and values of IVOMD, ME, and in vitro CH₄ generation for silages generated by the incorporation of PCW at different rates (0.5 %, 1 %, and 2 %).

The statistical analysis of the CP and IVOMD values of the silages shown in Table 2 demonstrated significant group differences at a significance level of p < 0.05. Nevertheless, the levels of DM, CA, ADF, NDF, ME, and CH₄ did not exhibit any statistically significant changes (p > 0.05). The examination of the CP values of the silages revealed that the addition of PCW resulted in an increase in CP levels. Table 3 presents the fermentation characteristics of the silages generated in this study using CPW.

Statistically significant differences (p < 0.05) were seen across groups when analyzing the fermentation parameters (pH, NH₃-N, total yeast-mold, and CO₂) of silages made by including varying quantities of PCW. However, no significant difference was identified in LAB values (p > 0.05). The control group exhibited the greatest pH value (3.66), whereas the silage group with the addition of 2 % PCW had the lowest pH value (3.61) (p < 0.05) during the pH testing of the silages.

4 Discussion

The addition of PCW significantly improved the quality and fermentation of corn silage in the current study. The easily soluble carbohydrates included in PCW might potentially serve as a source of energy for microorganisms in the silage. This process enhanced the fermentation process and reduced the chances of spoiling (Doğan Daş et al., 2023). The properties of fermentation in silage were significantly impacted by the addition of PCW. For example, the acids in the leftover PCW cause the pH of the silage to drop more quickly. These acids efficiently preserve the feed by preventing the growth of dangerous microorganisms (Doğan Daş et al., 2023). The PCW may be used to form an impervious barrier on the surface of silage pits, thus inhibiting bacterial development and the decomposition of the stored feed. This strategy is efficient and does not need additional storage space. The acidic properties of PCW inhibit the growth of undesirable microorganisms, hence enhancing the preservation of silage.

Yakişir and Aksu (2019) reported that insufficient preservation of silages might result in the denaturation of protein components. Nevertheless, the results of this research demonstrate that the protein levels were increased, indicating that the proteins did not experience denaturation throughout the fermentation process in the present investigation. The potential influence of low-dose PCW application on the absence of discernible disparities in silage ADF and NDF concentrations between the control and experimental cohorts is under scrutiny. The absence of a discernible increase in ambient LAB activity resulting from PCW addition led to the inability of the cell wall components in the silages to undergo degradation. Consequently, this lack of degradation contributed to the absence of any significant disparity in ADF and NDF values between the control and experimental groups.

Significant enhancements in in vitro organic matter digestibility (IVOMD) values were seen across all experimental groups in comparison to the control group. The control group had the lowest IVOMD value. Conversely, the group that received an addition of 0.5 % PCW demonstrated the highest IVOMD value. The potential cause for the observed rise in IVOMD values is believed to be the readily soluble carbohydrate content found in PCW. Lactic acid (LA) serves as the primary fermentation product in silages, and it undergoes fermentation in the rumen before being assessed by ruminant animals. Consequently, an elevation in IVOMD values would be logically consistent with this relationship. The current study's results are corroborated by a work conducted by (Şenyüz and Karsli, 2021, 2022), which demonstrated that the inclusion of potato pulp silage as a substitute for corn silage in dairy cow diets resulted in increased organic matter digestibility at different levels.

No significant differences were seen in the ME and CH₄ levels of the silages when comparing the groups. The lack of a noticeable difference between the two groups was attributed to the inclusion of a small number of PCW.

It has been shown that the ideal pH range for silage falls between 3.5 and 4.2 (Rondahl et al., 2011). Upon examination of the NH₃-N values of the silages, it was observed that the control group exhibited the highest value (10.63), whilst the group supplemented with 2 % PCW had the lowest value (6.67). There are two significant adverse processes that take place in the plant when the material intended for silage is shredded to the appropriate sizes and then compressed into the silo. Respiration and protein catabolism are two instances of metabolic processes. Plant proteases are enzymes that catalyze the hydrolysis of proteins, resulting in the formation of smaller peptide and amide molecules. These molecules are then subjected to further degradation processes, leading to the production of amino acids and ammonia. Elevations NH₃-N concentrations inside silage may arise, perhaps attributable to the process of proteolysis.

The consumption and productivity of animals that are fed silages containing a significant degree of protein breakdown resulting from proteolysis are diminished (Filya, 2001). A significant decrease in the overall yeast and mold levels of the silages was seen when comparing the control group to the experimental groups. In a study conducted by Özüretmen (2019), it was shown that the transformation of easily soluble sources of carbohydrates into lactic acid (LA) and acetic acid (AA) resulted in a reduction in pH levels of silage. This reduction in pH levels was attributed to the antibacterial properties of AA, which effectively prevented the growth of yeast and mold in silages. The CO₂ levels observed in the silages were determined to be comparatively lower when compared to the control samples. The occurrence of high levels of carbon dioxide in silages serves as an indication of the aerobic degradation of the silages. Additionally, the presence of residual sugars following the fermentation process diminishes the capacity of silages to withstand aerobic conditions when they are opened for feeding and exposed to unrestricted air intake (Filya, 2002).

5 Conclusion

This study examined the effects of varying amounts of PCW addition on quality, fermentation process, IVOMD, and in vitro gas generation in corn silage. The inclusion of 2 % PCW had beneficial impacts on the fermentation characteristics, overall quality, and in vitro digestion of organic matter. This research concluded that PCW may be considered a suitable silage supplement due to its beneficial impact on both the quality of the silage and its fermentation characteristics.

CRediT authorship contribution statement

Besime Doğan Daş: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.