Intake, digestibility and rumen fermentation pattern in wethers\nfed total mixed ration silage containing dry or fresh apple pomace

Abstract

Apple pomace is a by-product that remains after milling and pressing apples for juice and cider production. It is usually a seasonal product available after the autumn harvest and is produced in large amounts in many countries (Perussello et al., 2017). Apple pomace has many uses, such as for food, pectin, citric acid and dietary fibre production (Shalini and Gupta, 2010). Demand for it as feed is expected to increase with a global supply shortage of feed grains and rising feed prices. As a feed material, the chemical composition of fresh apple pomace (FAP) is characterized by high moisture and fermentable sugar contents and low crude protein (CP) content (Gasa et al., 1992). It was shown that FAP promotes silage fermentation (Fang et al., 2016). However, it was also indicated that silage containing FAP produces not only organic acids but also ethanol. Ethanol contains high energy and volatilizes easily, however when its content in silage is high, a loss of energy and dry matter (DM) may occur through volatilization (Pedroso et al., 2005). Furthermore, in some studies it was observed that ethanol affects cow milk composition and flavour (Randby et al., 1999) and reduces feed digestibility in ruminants (Emery et al., 1959; Fang et al., 2016). Because of high moisture content, FAP is challenging to transport over long distances, limiting its widespread use. In practice, apple pomace as feed material is circulated in a dry state. Because most of the circulated dry apple pomace (DAP) ABSTRACT. The fermentation quality of total mixed ration silage (TMRS) prepared with dry apple pomace (DAP) or fresh apple pomace (FAP), as well as their effects on digestibility and rumen fermentation in feeding wethers were evaluated. Maize, wheat bran, soyabean meal, timothy and alfalfa hay were used to compose TMRS. Proportions of DAP and FAP in TMRS were 200 g/kg dry matter (DM) each, and the moisture content of TMRS was adjusted to 550 g/kg and ensiled for 60 days. The mixture of TMR with DAP without ensiling was used as a control diet, and experimental treatments were TMRS with DAP and TMRS with FAP. The TMRS with DAP and FAP were well fermented, with low pH and high lactic acid content. Ethanol was produced in both TMRS treatments and was significantly higher in that with FAP. Nitrogen retention and digestibility of DM, organic matter and crude protein were significantly lower in the treatments with DAP and FAP than in control one. Four hours after feeding TMRS with DAP and FAP, the rumen molar proportion of acetic acid was higher, while those of propionic acid and ammonia nitrogen content were lower, with more pronounced changes in the treatment with FAP. The results of this study suggest that the proportion of DAP or FAP in TMRS should not exceed 200 g/kg of diet DM. Received: 16 November 2020 Revised: 3 March 2021 Accepted: 7 March 2021