Nutritive evaluation of olive cake and tomato pomace for small ruminant feeding

Abstract

The use of agroindustrial by-products in animal feeding requires precise information on their nutritional value. However, agroindustrial by-products are heterogeneous and as consequence, values for chemical composition and nutritive parameters are highly variable, and the information related is scarce. For that reason, the objective of this Doctoral Thesis is to evaluate the nutritive value of two by-products that are produced in huge amounts in Spain: olive cake (OC) and tomato pomace (TP). In order to achieve this objective, six Experiments (five in vitro and one in vivo) were conducted. The objective of Experiment 1 (Paper 1) was to analyse the influence of storage time and further processing: crude OC (COC), exhausted OC (subjected to a second oil extraction; EOC) and cyclone OC (obtained from a cyclone separator; CYOC) on nutritive value of OC samples. Twelve samples (six COC and six EOC) were obtained monthly from the same pond from 1 to 6 storage months, and nine samples (three COC, three EOC and three CYOC) were obtained monthly from a different pond from 6 to 9 months storage. Chemical composition was analysed, and OC samples were fermented in vitro with sheep rumen fluid. Increasing storage time up to 6 months decreased sugars and total soluble polyphenols (TSP) content but increased fibre content in OC. Dry matter effective degradability (DMED) decreased linearly (P The objective of Experiment 2 (Paper 2) was to determine the variability in the chemical composition and in vitro ruminal fermentation of OC by-products. Forty-two OC samples with different storage times (1–14 months) and processing (25 COC, 9 EOC and 9 CYOC) were fermented in vitro with sheep ruminal fluid. EOC samples had a lower EE content than COC and CYOC (15.9, 110 and 157 g/kg DM, respectively), but greater neutral detergent fibre (NDF) (645, 570 and 441 g/kg DM) and acid detergent insoluble nitrogen (ADIN) (9.76, 8.10 and 8.05 g/kg DM) content. EOC had the greatest (P The aim of this Experiment 3 (Paper 5; Appendix) was to estimate in vitro the nutritive value of four samples of COC with different particle size obtained during the drying process from the same trommel at different stages of the screening procedure. Particles size was greater than 3 mm (COC3), 2 mm (COC2) and 1 mm (COC1) or smaller than 1 mm (COC0). Alfalfa hay and barley straw were included in the study for comparative purposes. Chemical composition was analysed in all samples. Gas production kinetics was determined in 120 h in vitro incubations with sheep rumen fluid as inoculum, and fermentation parameters and in vitro dry matter digestibility (DMD) were analysed after 24 h of incubation. COC3 and COC0 samples had lower contents of NDF (415 and 391 g/kg DM), but greater crude protein (CP) (96.6 and 114 g/kg DM) and EE (220 and 242 g/kg DM) contents, than COC2 and COC1 (627 and 624; 42.4 and 48.7; 102 and 124 g/kg DM, respectively). DMD of COC samples ranged from 39.4 to 58.7%, and was lower than that for alfalfa hay (67.5%) for all samples, but greater than that for barley straw (42.4%) for COC0 and COC3 samples. COC3 and COC0 samples had greater (P The objective of Experiment 4 (Paper 3) was to determine the variability in nutritive value for ruminants of 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 analysed 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 DM content ( The objective of Experiment 6 (Paper 4) was to verify lower 15N abundances of ADIN than of total N and neutral detergent insoluble N (NDIN) in different feeds, and to assess the magnitude of ADIN contamination. Samples from one corn crop (aerial biomass, grain and root) and two sunflower (SF) crops (aerial biomass and seeds) were analysed for 15N abundance and content of total N, NDIN and ADIN. Samples had been 15N-labelled by fertilizing with either 15NH4NO3 or NH4 15NO3, and there were three replicates per type of sample. The 15N-abundance of total N and NDIN was similar (P > 0.05) for all samples, whereas that of ADIN was lower (P