Abstract
Simple SummaryReutilization of agroindustrial by-products in animal feeding could contribute to the reduction of environmental problems associated with their accumulation, but it is necessary to assess their nutritive value. Tomato pomace (TP) is a by-product of the tomato industry that could be used in ruminant feeding, but data on its nutritive value are limited. The aim of this work was to analyze the chemical composition, in vitro rumen fermentation, and intestinal digestibility of 12 TP samples obtained from two processing plants at different times during the tomato campaign and to assess the in vitro fermentation of diets including increased TP amounts. The chemical composition of TP showed little variability. Samples of TP had high fiber, protein, and fat content and were rapidly fermented in the rumen, but the in vitro intestinal digestibility of the protein was low. The in vitro results provide useful information for including TP in ruminant diets, indicating that amounts of TP up to 180 g/kg could be included in a diet for fattening ruminants without negatively affecting rumen fermentation, but these results should be confirmed in vivo.The objective of this study was to determine the variability in nutritive value for ruminants of tomato pomace (TP) samples and analyze its effect on in vitro fermentation when it was included in a high-concentrate diet. Twelve TP samples were obtained from two processing plants at weekly intervals and analyzed for chemical composition, in vitro rumen fermentation, and intestinal digestibility. The chemical composition of TP did not differ between processing plants and only slight variations were observed among sampling times. Tomato pomace had a low dry matter content (<300 g/kg), a high content of neutral detergent fiber, crude protein, and ether extract (572, 160, and 82.7 g/kg dry matter on average, respectively), and was rapidly fermented in the rumen. Protein degradability at 16 h in situ incubation was 510 g/kg and in vitro intestinal digestibility of protein was low (430–475 g/kg). Replacing soybean meal and barley straw by dried TP increased the in vitro fermentation rate and the production of volatile fatty acids and reduced NH3-N concentrations without affecting CH4. In summary, TP samples showed little variability in nutritive value over sampling time and TP of up to 180 g/kg could be included in high-concentrate diets without negatively affecting rumen fermentation.
Highlights
The world production of processing tomato has increased up to 37.8 × 106 tons in 2017 according to estimates of the World Processing Tomato Council [1]
Chemical composition of Tomato pomace (TP) (Table 2) was relatively unchanged over the sampling period and only lignin and ether extract (EE) contents varied significantly (p ≤ 0.017) with time; in general, lignin increased with advancing time, whereas EE decreased
According to Drouliscos [44], the essential amino acids profile in TP protein is similar to that in soybean meal, but the low values of IDCP observed in our study indicate that about half of the protein reaching the small intestine may not be digested, whereas intestinal digestibility of soybean meal is greater than 90% [43]
Summary
The world production of processing tomato has increased up to 37.8 × 106 tons in 2017 according to estimates of the World Processing Tomato Council [1]. Animals 2019, 9, 343 the greatest tomato producers, accounting for 4.7 × 106 and 2.8 × 106 tons of tomatoes for processing in. Tomato pomace (TP) is a by-product of the tomato industry that consists mainly of peels, seeds, and small quantities of pulp that remain after the production of juice, paste, sauce, and other processed products, representing between 5% and 10% of the original fruits [2]. The nutritive value of TP depends on many factors, such as cultivars, season, or processing, among others [8], but current knowledge on its variability is limited
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