Chemical composition and nitrogen availability for goats and sheep of some olive by-products

Application of Olive By-Products in Livestock with Emphasis on Small Ruminants: Implications on Rumen Function, Growth Performance, Milk and Meat Quality

The olive oil industry has a leading position in the Mediterranean countries, resulting in the production of considerable quantities of the respective by-products (OB) that constitute an important environmental issue. OB contain valuable nutrients and bioactive components that can be re-used under the bioeconomy strategy, and several chemical, physical, and biological processes have been evaluated with the intention to improve their nutritional value. One feasible application of OB is their incorporation in the diets of livestock and especially ruminants due to their high fiber content. As indicated by numerous studies, OB dietary supplementation increases the levels of monounsaturated fatty acids (MUFAs) and decreases that of saturated fatty acids (SFAs) in the milk and meat of ruminants with beneficial effects for consumers' health. At the same time, environmental impact and feeding costs are reduced without detrimental effects on ruminal fermentation, nutrients utilization, growth performance, carcass traits, milk yield and composition.

Can Agro-Industrial By-Products Rich in Polyphenols be Advantageously Used in the Feeding and Nutrition of Dairy Small Ruminants?

Simple Summary

In the Mediterranean area, where dairy sheep and goats are widespread, the use of by-products in the diet of small ruminants is an ancient practice. Today the great availability of industrial by-products produced at the local level (e.g., grape, olive, tomato and myrtle residues), appears to be a promising strategy for reducing competition with human edible foods and the cost of off-farm produced feeds since they are imported worldwide. Moreover, these co-feeds can contribute to reducing the ecological and water footprint associated with crop cultivation. The presence of bioactive compounds, such as polyphenols, confers added value to these materials. Several positive aspects are apparent when such by-products are included in the diets of small dairy ruminants, in particular on ruminal metabolism, animal health, and the quality of derived products.

Abstract

Recently, the interest in industrial by-products produced at the local level in Mediterranean areas, resulting from fruit and vegetable processes, has increased because of their considerable amounts of bioactive compounds, including polyphenols. In this review, we analyze the most recent scientific results concerning the use of agro-industrial by-products, naturally rich in polyphenols (BPRP), in the diets of small dairy ruminants. Effects on milk production, milk and rumen liquor fatty acid profile, metabolic parameters, and methane production are reviewed. The feed intake and digestibility coefficients were generally depressed by BPRP, even though they were not always reflected in the milk yield. The main observed positive effects of BPRP were on quality of the milk’s FA profile, antioxidant activity in milk and blood, a reduction of rumen ammonia, and, consequently, a reduction of milk and blood urea. The expected beneficial effects of dietary polyphenols in small ruminants were not always observed because of their complex and variable matrices. However, owing to the large quantities of these products available at low prices, the use of BPRB in small ruminant nutrition offers a convenient solution to the valorization of residues arising from agricultural activities, reducing feed costs for farmers and conferring added value to dairy products at the local level, in a sustainable way.

Performance of Barki Lambs Fed on Rations Containing Olive Cake with or Without Polyethylene Glycol

BACKGROUND AND OBJECTIVE

Olive by-products could be a suitable alternative feedstuffs ingredient in ruminants rations. This study was carried out to evaluate effects of replacing clover hay by olive cake with or without addition of poly ethylene glycol in growing lambs ration.

METHODOLOGY

Thirty five Barki lambs averaged 34 kg body weight and 5 months old were divided into 5 groups (7 animals of each) according to live weight for 90 days feeding trial. Olive cake was treated mechanically by hummer mill, screened to produce screening olive cake (treated olive cake, TOC).

RESULTS

Data of dry matter and organic matter digestibility were decreased with ration containing 20% TOC from ration or 67% from clover hay comparing with others. No significant differences were observed among groups in crude protein digestibility. Total digestible nutrients (TDN) as an energy measurement for the experimental rations cleared that replacing process of clover hay by TOC up to 20% of DM intake or 67% of clover hay, given lower values (65.32 and 66.80%). The rumen pH values were not affected by the different experimental rations including control. The highest rumen NH3 was recorded with lambs fed ration containing 33% TOC without PEG instead of clover hay, while the lowest values was recorded with that group fed ration containing 33% TOC with PEG. No significant differences were detected in total gain, ADG as well as feed efficiency among the experimental rations. Dry matter intake slightly increased with feeding growing lambs on TOC containing rations except R5 compared to the control group.

CONCLUSION

Summing up partially de-stoned olive cake by screening could be used in replacing clover hay for growing lamb rations, at inclusion levels up to 33 and 67% with or without poly ethylene glycol, with no adverse on performance of growing lambs.

Effects of dietary olive leaves on performance, carcass traits, meat stability and antioxidant status of fattening Mahabadi male kids

Twenty-four Mahabadi goat kids (5-6 months of age) were used to evaluate the effects of feeding olive leaves (OL) on performance, carcass traits and antioxidant status. The kids received three dietary treatments for 84 d with three levels of OL: 0 (control), 7.5 (OL7.5) and 15 (OL15) % (DM basis). Supplementation with OL had no effects on kid performance (P > 0.05). Total antioxidant capacity (TAC) was increased and malondialdehyde (MDA) concentration was decreased in plasma blood (P < 0.01) and Longissimus lumborum (LL) muscle (days 1, 4, 7 and 10) of kids (P < 0.01) with increasing level of OL in diet. The activity of glutathione peroxidase (GSH-Px) in LL muscle was increased (P < 0.05) in OL15 fed kids compared with control group. Also, glucose content of serum was decreased by adding OL to kid diets (P < 0.01). Finally, inclusion of OL to kid diets resulted in similar growth performance compared to alfalfa feeding, and improved the antioxidative potential of LL muscle.

Determination of the In Vitro Gas Production and Potential Feed Value of Olive, Mulberry and Sour Orange Tree Leaves

This study was conducted to determine the potential nutritive value and in vitro gas production (IVGP) parameters of Olea europaea L. (Olive = OL), Morus alba L. (Mulberry = ML) and Citrus aurantium L. (Sour orange = SOL) tree leaves. Hohenheim gas test was used to determine the in vitro gas productions of the leaves. The gas production of samples over time was recorded for 3, 6, 9, 12, 24, 48, 72 and 96 h after incubation. Completely Randomized Design was used to compare gas production, and gas production kinetics of samples. The findings of the present study suggested that there were differences among the tree leaves in terms of crude protein, NDF, in vitro gas productions, organic matter digestibility (OMD), metabolisable energy (ME), net energy lactation (NE_L) and relative feed values (RFV) (P<0.01). ML had the highest condensed tannin contents (P<0.05), in vitro gas production (IVGP), OMD and energy values (P<0.01). SOL had highest RFV values. OL showed the lowest IVGP when compared to SOL and ML. Low NDF and ADF contents of SOL would probably increase the voluntary intake, digestibility and relative feed values of these leaves by ruminants. In conclusion, it was determined that OL, ML and SOL used in the study have low in vitro gas production and can be utilized as alternative roughage feed in ruminants. However, it is recommended that the results obtained from this research should be tested in in vivo studies.

Products derived from olive leaves and fruits can alter in vitro ruminal fermentation and methane production

BACKGROUND

The industrial processing of olive generates a high quantity of by-products. The objective of this study was to examine the effects of products derived from olive trees, i.e. leaves, fruits or kernels as a sole substrate (part A), and crude extract from leaves combined with a substrate (part B) on rumen microbial fermentation in an in vitro batch fermentation system. In this study, total gas production, methane production, and concentrations of volatile fatty acids (VFA) and ammonia in ruminal fluid were measured.

RESULTS

In part A, in vitro fermentation of leaves or fruits yielded a gas and total VFA production that were comparable with control substrate, while most of them produced significantly less methane (up to 55.6%) when compared to control substrate. In part B, amongst leaf extracts, only addition of chloroform extract reduced methane production, which was also associated with a decrease (P < 0.01) in gas production. This effect was associated with a significant reduction (P < 0.01) in acetate to propionate ratio and ammonia production, but not in reduction in VFA concentrations.

CONCLUSION

Olive leaf and olive leaf chloroform extract reduced ammonia production and increased the molar proportion of propionate in the rumen and can assist in developing novel feed additives for methane mitigation from the rumen. © 2016 Society of Chemical Industry.

Nutrient assessment of olive leaf residues processed by solid-state fermentation as an innovative feedstuff additive

AIMS

Olive leaf residue feedstuff additives were prepared by solid-state fermentation (SSF), and its feeding effects on broiler chickens were examined.

METHODS AND RESULTS

The fermentation's nutrient value, that is, protein enrichment, cellulase activity, tannic acid degradation and amino acid enhancement, was determined. The effect of different strains, including molds (Aspergillus niger, Aspergillus oryzae and Trichoderma viride) and yeasts (Candida utilis, Candida tropicalis and Geotrichum candidum), and the fermentation time on the nutrient values of the feedstuff additives was investigated. The experimental results showed that the optimal parameters for best performance were A. niger and C. utilis in a 1 : 1 ratio (v/v) in co-culture fermentation for 5 days. Under these conditions, the total content of amino acids in the fermented olive leaf residues increased by 22·0% in comparison with that in the raw leaf residues. Both Glutamic acid and Aspartic acid contents were increased by more than 25·4%. Broiler chickens fed with different amounts of feedstuff additives were assessed. The results demonstrated that the chicken weight gains increased by 120%, and normal serum biochemical parameters were improved significantly after 10% of the feedstuff additives were supplemented to the daily chicken feed for 28 days.

CONCLUSIONS

The co-culture combination of A. niger and C. utilis with SSF for olive leaf residue had the best nutrient values. The addition of 10% fermented olive leaf residue facilitated the chicken growth and development.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reveals that olive leaf residues fermented by SSF exhibited considerable potential as feed additives for feeding poultry.

In vitro utilization of lime treated olive cake as a component of complete feed for small ruminants

AIM

The current in vitro study was carried out to determine the chemical composition and inclusion level of lime treated olive cake on acid detergent fiber (ADF) replacement basis in adult male goats.

MATERIALS AND METHODS

Crude olive cake was collected and evaluated for proximate composition and protein fractionation. It was treated with 6% lime and incubated for 1 week under room temperature in 2 kg sealed polythene bags and was evaluated for proximate composition after incubation. Different isonitrogenous complete diets containing 0-50% of lime treated olive cake on ADF replacement basis were formulated as per the requirement of adult male goats. In ADF replacement, fiber and concentrate sources were replaced by lime treated olive cake by replacing the 0-50% ADF percentage of the total 40% ADF value of complete feed. The formulated complete diets were tested for in vitro degradation parameters.

RESULTS

Treatment of olive cake with 6% slaked lime increased availability of cellulose and alleviated digestibility depression caused by high ether extract percentage. Organic matter, nitrogen free extract, ADF and neutral detergent fiber were significantly lowered by lime treatment of olive cake. The cornell net carbohydrate and protein system analysis showed that non-degradable protein represented by acid detergent insoluble nitrogen (ADIN) was 21.71% whereas the non-available protein represented by neutral detergent insoluble nitrogen (NDIN) was 38.86% in crude olive cake. The in vitro dry matter degradation (IVDMD) values were comparable at all replacement levels. However, a point of inflection was observed at 40% ADF replacement level, which was supported by truly degradable organic matter (TDOM), microbial biomass production (MBP), efficiency of MBP and partitioning factor values (PF).

CONCLUSION

In our study, we concluded that there is comparable difference in composition of Indian olive cake when compared with European olive cake. The most important finding was that about 78% of nitrogen present in Indian olive cake is available to animal in contrary to that of European olive cake. We concluded from in vitro studies that Indian olive cake can be included in complete feed at 30% level (w/w; 40% ADF replacement) for feeding in small ruminants without compromising in vitro degradability of the feed.

Treated Olive Cake as a Non-forage Fiber Source for Growing Awassi Lambs: Effects on Nutrient Intake, Rumen and Urine pH, Performance, and Carcass Yield

The objective of this study was to investigate the effects of partial replacement of wheat hay with sun-dried (SOC) or acid-treated SOC (ASOC) olive cake on nutrient intake and performance of Awassi lambs. An additional objective was to study the effects of acid treatment of olive cake (OC) on its chemical composition and nutritive value. On DM basis, sun-drying of OC did not dramatically affect its chemical composition. On the other hand, treating SOC with phosphoric acid decreased (p<0.05) SOC contents of neutral detergent fiber. Twenty seven male lambs (17.6±0.75 kg body weight) individually housed in shaded pens were randomly assigned to one of three dietary treatments (9 lambs/treatment). Dietary treatments were formulated to be isocaloric and isonitrogenous by replacing 50% of wheat hay in the control diet (CTL) with SOC or ASOC and to meet all nutrient requirements. Dietary treatments had no effects on nutrient intake or digestibility except for ether extract. Lambs fed the SOC diet had (p = 0.05) faster growth rate, greater final body weight, and greater total body weight gain in comparison with the CTL diet, but not different from the ASOC diet. Additionally, lambs fed the SOC diet had greater (p = 0.03) hot and cold carcass weights than the ASOC diet, but not different from the CTL diet. However, feed conversion ratios and dressing percentages were similar among dietary treatments. In conclusion, replacing half of dietary wheat hay with SOC improved performance of Awassi lambs with no detrimental effects on nutrients intake or digestibility. No further improvements in the nutritive value of SOC and lambs performance were detected when SOC was treated with acid.

Performance of lambs grazing an annual Mediterranean pasture or fed supplements based on olive oil cake or maize and its influence on system outputs

Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual Mediterranean pasture (GRAZE), weaned followed by a concentrate plus hay diet (CONC), or weaned and fed a concentrate with 33% dry olive oil cake plus hay (CAKE). Grazing lambs averaged a liveweight gain of 334 g/day during the 28-day experimental period, which was higher (P < 0.05) than that of CONC and CAKE (283 and 276 g/day, respectively); however, there were no differences in empty body or dressed carcasses weights due to dietary treatment. The feed conversion of the olive seed cake supplement (kg supplement/kg gain) was lower (P < 0.01) than that of the maize-based supplement. Despite some significant differences between carcasses traits, all were small and of little commercial consequence. Simulation modelling of whole-system performance suggested that early weaning of lambs followed by concentrate feeding would reduce the finishing period, marginally increase the liveweight of ewes and would have little effect on pasture availability. It was further concluded that olive oil cake can be a large proportion of concentrate diets without negatively affecting carcass quality.

Suitability of partly destoned exhausted olive cake as by-product feed ingredient for lamb production

The effect of diets with different levels of partly destoned exhausted olive cake (PDEOC) on growth performance and carcass traits of Gentile di Puglia breed lambs was studied. Sixty lambs (16.5 ± 0.5 kg) at weaning were randomly allocated to 3 isocaloric and isonitrogenous diets for 50 d. Pelleted total mixed rations (TMR) were formulated to provide olive by-product at 3 different levels: 1) a control diet without olive by-product (PDEOC-0), 2) an experimental corn-based diet containing 10% by-product (PDEOC-10) replacing part of the oat hay and sunflower meal, and 3) an experimental corn-based diet containing 20% PDEOC (PDEOC-20) replacing part of the oat hay and soybean meal. To evaluate in vivo digestibility of the diets, adult rams (n = 3) were placed in metabolic cages, their individual feces and urine were collected, and differences were observed for DM and fiber fractions. Results from the growth trial of the lambs showed that performance was influenced by olive by-product inclusion in diet (P < 0.05). At the end of the feeding period, lambs were slaughtered, and none of the variables studied were influenced by dietary treatment except for cold carcass dressing (P = 0.027) and half-carcass weight (P = 0.019), which were improved in lambs fed the PDEOC-20 diet. As a result, the current study confirms that olive by-product can be used in lamb finishing rations, resulting in a valuable ingredient as replacement for conventional feeds, which could reduce feeding costs because of the lower cost of the olive by-product. Use of olive by-products as animal feed may become economically feasible for producers where the olive oil industries play an important economic role.

A comparative study of the effect of two-stage olive cake added to alfalfa on digestion and nitrogen losses in sheep and goats

This work was conducted to evaluate the effect of tannins, contained in a by-product derived from olive oil extraction (two-stage olive cake), on nutrient digestibility, nitrogen (N) losses and liver and kidney functions in goats and wethers. Six Segureña wethers and six Granadina goats were fed three experimental diets: alfalfa hay (AH); alfalfa hay and a concentrate (formulated with two-stage olive cake, barley and a mineral-vitamin mixture) without (AHCO) or with polyethylene glycol (PEG) addition (AHCOP). The inclusion of two-stage olive cake increased condensed tannins content of the diet and led to a decrease ( P < 0.001) in dry matter, organic matter, neutral-detergent fibre, acid-detergent fibre and crude protein (CP) digestibility. PEG supply increased ( P < 0.001) CP digestibility and N losses in urine and faeces only in wethers. Concentrations of creatinine and alkaline phosphatase activity, measured in the serum of animals, were not modified either by olive cake inclusion or by PEG supply. Results from this work indicate a higher sensitivity of sheep to diets containing condensed tannins, compared with goats, and reveal no toxic effect of tannins from two-stage olive cake at the concentration used in the experimental diets.

Effect of dietary supplementation with olive pomaces on the performance and meat quality of growing rabbits

The aim was to investigate the effects of three types (A, B and C) of stoned and dehydrated olive pomaces (OPs), differing in olive cultivar, on productive performance and meat quality of growing rabbits. The inclusion of OPs (5%) negatively affected the performance of rabbits as it reduced the feed intake, growth rate, carcass weight and dressing out percentage (P<0.05). Compared with the control, the meat of OP rabbits had a greater amount of monounsaturated and a lower amount of polyunsaturated fatty acids (P<0.05), independent of the type of OP used. Oxidative processes in the meat of OPA and OPB were higher (P<0.05), whereas OPC showed the same levels as the control group. This was due to the higher total polyphenol concentration and to the concomitant lower peroxide value of OPC. These results recommend the use of OP in rabbit diet with caution, taking into account the quality of the by-product in terms of oxidative status.

Fermentation characteristics and microbial growth promoted by diets including two-phase olive cake in continuous fermenters

Two-phase olive cake (2POC) is the by-product obtained from the so called 'two-phase' procedure to extract olive oil by mechanical methods. After the mechanical extraction the 2POC is dried and most of the remaining oil extracted by chemical means. The production of the crude by-product may reach more than 4 millions t/year in Spain (MAPA, 2003), most of it in areas (Southeast) with shortage of pastures and conventional feeds for ruminants. Six continuous fermenters, inoculated with ruminal liquor from wethers or goats, were fed lucerne hay (LH); LH plus a concentrate including dried two-phase olive cake (LHCO) and; diet LHCO added with polyethylene glycol (LHCOP). The highest pH values and ammonia N (NH(3)-N) output were found in fermenters fed diet LH (6.19 and 6.35 for pH, and 53.7 and 68.9 mg NH(3)N/day, respectively, in fermentes inoculated with rumen liquor from sheep and goats) without differences due to the inoculum origin. The digestibility of carbohydrates (CHO) was affected (p < 0.001) by inoculum (67.0 and 58.8%, respectively, for goats and wethers) the lowest values being for diet LHCO (53.2 and 57.0% with inoculum from wethers and goats, respectively). The main volatile fatty acid (VFA) was acetic acid with higher (p < 0.01) values in fermenters with inoculum from goats than from wethers (80.2 and 63.0 mmol/day respectively). The efficiency of bacterial protein synthesis (EBS) was not different (p > 0.05) with inoculum from wethers and goats [26.4 and 28.1 and 35.2 and 33.5 g bacterial N/kg digested CHO, respectively, obtained by using diamino pimelic acid (DAPA) and purine bases (PB) as microbial markers]. The lowest (p < 0.05) values were found in fermenters fed diets LHCOP and LH, estimated, respectively, from DAPA and PB (21.9 and 29.0 g bacterial N/kg digested CHO). The substitution of a part of lucerne hay by a concentrate including dried 2POC does not seem to cause important differences in efficiency of VFA production. Results concerning bacterial protein synthesis are not so clear since values estimated from DAPA and PB did not show similar trends. Neither inoculum origin nor PEG had important effects on fermentation characteristics. The DAPA could be an adequate marker in continuous fermenters, with comparative purposes, as protozoa are not present and, estimated protein synthesis values are similar to those obtained in vivo with similar diets using urinary excretion of PD (Yáñez Ruiz et al., 2004b). Further research is needed to state the optimal proportion of 2POC in practical diets for ruminants at both maintenance and production stages.

Nutritive evaluation of olive tree leaves by near-infrared spectroscopy: effect of soil contamination and correction with spectral pretreatments

Olive leaves obtained as a byproduct in the Mediterranean region could play an important role in the nutrition of extensive ruminant systems. However, the reported variation in their nutritive value, among other reasons due to discrepancies in mineral content, is considered an important obstacle for their common use. Near-infrared spectroscopy (NIRS) could fulfill the requirements of these productive systems, providing analytical information in a rapid and economic way. In this work, the effect of soil contamination on NIR spectra has been studied, as well as its correction with some of the most commonly used spectral pretreatments (derivatives, multiplicative scatter correction, auto scaling, detrending, and a combination of the last two transforms). Effects were evaluated by visual inspection of the transformed spectra and comparison of the calibration statistics obtained to estimate acid insoluble ash and total ash contents and in vitro pepsin cellulase digestibility of organic and dry matter. The incidence of spectral curvature effects caused by soil contamination that can be conveniently corrected with pretreatments such as derivatives was confirmed.

Ruminal fermentation and degradation patterns, protozoa population, and urinary purine derivatives excretion in goats and wethers fed diets based on two-stage olive cake: effect of PEG supply

Three experiments were conducted in Granadina goats and Segureña wethers fed at maintenance level to evaluate the effect of including a mixture of barley and a new by-product derived from olive oil extraction (two-stage dried olive cake) on ruminal degradation and passage kinetics (Exp. 1), fermentation pattern and protozoa population (Exp. 2), and urinary purine derivatives excretion (Exp. 3). Polyethylene glycol was supplied to the animals to evaluate the effects of tannins contained in the by-product. The experimental diets were as follows: alfalfa hay and alfalfa hay plus a concentrate, formulated with two-stage dried olive cake, barley, and a mineral-vitamin mixture either with or without the addition of polyethylene glycol to the drinking water. The inclusion of two-stage dried olive cake in the diet resulted in an increase of condensed tannins. Ruminal VFA concentration in goats and wethers increased (P < 0.05) and ammonia N (NH3-N) concentration decreased (P < 0.05). The inclusion of two-stage dried olive cake decreased (P < 0.001) urinary allantoin excretion only in wethers. Ruminal degradation profiles and fractional passage rates were similar in goats and wethers. The polyethylene glycol supply increased (P < 0.001) DM and N degradation rates in both animal species but did not modify the fractional passage rate. Ruminal fermentation patterns were also similar in goats and wethers and were affected by polyethylene glycol supply. In general, Entodiniomorphida and Holotricha protozoa counts were higher (P < 0.05) in the rumen of goats than of wethers. Protozoa count in wethers responded more to polyethylene glycol supply than in goats. The present work presents the first data obtained from a comparative study with sheep and goats concerning urinary excretion of purine derivatives. The excretion was similar in both animal species when fed alfalfa hay; however, polyethylene glycol affected only urinary allantoin excretion in wethers. Results suggest a greater sensitivity of wethers than of goats to two-stage olive cake condensed tannins.

Ruminal fermentation and degradation patterns, protozoa population and urinary purine derivatives excretion in goats and wethers fed diets based on olive leaves1

Olives leaves, accrued during the processing of olive harvests for oil extraction, are poor in N, rich in crude fat and ADF (1.19, 8.03 and 28.2 g/100 g of DM, respectively), and relatively low in condensed tannins (11.1 mg/g of DM). Three experiments were conducted in a 2 x 3 (two animal species: goats vs. wethers; and three experimental diets: olive leaves without or with polyethylene glycol supply and olive leaves supplemented with barley and faba beans) factorial design to evaluate ruminal degradation and passage kinetics (Exp. 1), fermentation pattern and protozoa population (Exp. 2), and urinary purine derivatives excretion (Exp. 3). Polyethylene glycol was supplied to evaluate the effects of condensed tannins contained in olive leaves. Ruminal degradability of CP was low in both goats and wethers, although goats showed higher (P < 0.05) values than wethers. Supplementation of olive leaves with barley and faba beans increased (P < 0.001) ruminal degradability of DM and CP. Both goats and wethers fed olive leaves showed similarly low particulate fractional passage rates (0.021 and 0.023/h, respectively). Ingestion of olive leaves promoted low NH3-N and VFA concentrations, which reflect poor microbial activity. These concentrations, especially that of VFA, increased when barley and faba beans were added. Ingestion of olive leaves affected ruminal protozoa: Entodiniomorphida showed low concentrations and Holotricha completely disappeared. When animals received a diet based on olive leaves, barley, and faba beans, Holotricha appeared in the ruminal liquor and Entodiniomorphida increased (P < 0.001). In goats and wethers fed olive leaves alone, urinary allantoin excretion was very low (163 and 164 micromol/kg BW0.75 in goats and wethers, respectively), and moderate values (352 and 389 micromol/kg BW0.75 in goats and wethers, respectively) were observed when a diet of olive leaves, barley, and faba beans was fed. The polyethylene glycol supply did not have an effect in goats or in wethers, indicating the lack of an effect of condensed tannins in olive leaves. Ingestion of olive leaves promotes a low microbial activity, although its supplementation with readily degraded carbohydrates and protein improves microbial activity and, as a consequence, increases its ruminal degradation. In general, for most of the measured variables, there were no animal species x diet interactions. Thus, goats and wethers had similar ruminal activities when fed diets based on olive leaves.