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Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 369. 1-4 de diciembre, Virtual meeting (2020)., CSI276P18, JCyL, FEDER and ESF, UE.

Resumen de la Comunicación Oral presentada al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems. 1-4 de diciembre. Virtual meeting (2020)., Projects EUSMARTER & JCyL CSI276P18, FEDER and ESF.

Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 176. 1-4 de diciembre, Virtual meeting (2020)., AGL2017-87812-R, AEI/FEDER, UE; Ramón y Cajal program, RYC-2015-17230, MINECO/ESF, UE.

11 páginas, 4 tablas, 1 figura., Milk odd- and branched-chain fatty acids (OBCFA) are largely derived from bacteria leaving the rumen, which has encouraged research on their use as biomarkers of rumen function. Targeted research has examined relationships between these fatty acids (FA) and dietary components, but interactions between the effects of lipids and other nutrients on milk OBCFA are not well characterized yet. Furthermore, factors controlling milk OBCFA in sheep are largely unknown. Thus, the present meta-analysis examined relationships between diet composition and milk OBCFA using a database compiled with lot observations from 14 trials in dairy ewes fed lipid supplements. A total of 47 lots received lipid supplements, whereas their respective controls (27 lots) were fed the same basal diets without lipid supplementation. Relationships between milk OBCFA and dietary components were first assessed through a principal component analysis (PCA) and a correlation analysis. Then, responses of milk OBCFA to variations in specific dietary components (selected on the basis of the PCA) were examined in more detail by regression analysis. According to the loading plot, dietary unsaturated C18 FA loaded opposite to major milk OBCFA (e.g., 15:0, 15:0 anteiso, and 17:0) and were strongly correlated with principal component 1, which described 46% of variability. Overall, regression equations supported this negative, and generally linear, relationship between unsaturated C18 FA levels and milk OBCFA. However, the influence of C20–22 n-3 polyunsaturated FA and saturated FA was more limited. The PCA also suggested that dietary crude protein is not a determinant of milk OBCFA profile in dairy ewes, but significant relationships were observed between some OBCFA and dietary fiber or starch, consistent with a potential role of these FA as biomarkers of rumen cellulolytic and amylolytic bacteria. In this regard, regression equations indicated that iso FA would show opposite responses to increasing levels of acid detergent fiber (positive linear coefficients) and starch (negative linear coefficients). Lipid supplementation would not largely affect these associations, supporting the potential of OBCFA as noninvasive markers of rumen function under different feeding conditions (i.e., with or without lipid supplementation). Because consumption of these FA may have nutritional benefits for humans, the use of high-fiber/low-starch rations might be recommended to maintain the highest possible content of milk OBCFA in dairy sheep., This work was supported by the Spanish Research State Agency (Agencia Estatal de Investigación) and the European Regional Development Fund (project AGL2017-87812-R, AEI/FEDER, UE). P. G. Toral benefited from a Ramón y Cajal research contract (RYC-2015-17230) and A. Della Badia from a FPI predoctoral contract (PRE2018-086174), from the Spanish Ministries of Economy and Competitiveness (MINECO) and Science and Innovation (MICINN), respectively. Co-funding by the European Social Fund is also acknowledged. The authors thank M.-P. Létour-neau-Montminy (Université Laval, Québec, Canada) for helpful assistance with statistical analysis. The authors have not stated any conflicts of interest.

Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 369. 1-4 de diciembre, Virtual meeting (2020)., CSI276P18, JCyL, FEDER and ESF, UE.

14 páginas, 5 tablas, 2 figuras., The causative relationship between ruminal biohydrogenation alterations known as the trans-10 shift and marine lipid-induced milk fat depression (MFD) has been questioned in dairy ewes, but the large intra- and inter-experiment differences in the levels of trans-10 shift indicators precludes firm conclusions. This meta-analysis was conducted to quantify the relationship between trans-10 shift milk indicators [i.e., trans-10,cis-12 conjugated linoleic acid (CLA), trans-10 18:1 or trans-10:trans-11 18:1 ratio] and lactation performance, mainly milk fat traits, in Assaf dairy ewes. A database comprising of 17 experiments including 50 dietary treatments was compiled. The diets were grouped into 2 dietary conditions: (1) non-MFD condition, which included 14 diets supplemented with plant oils and tannins that modified the milk fatty acid profile without lowering milk fat concentration and yield, and 12 respective control diets, and (2) MFD condition, which included 15 diets supplemented with marine lipids that induced the low fat-milk syndrome, and 9 respective control diets. The overall levels of milk trans-10 shift indicators did not differ between dietary conditions, but significant increments were found in the supplemented diets relative to their respective controls. A similar linear and negative (slope: −7.28 ± 2.816) relationship between milk fat concentration and trans-10,cis-12 CLA was found in both dietary conditions. However, the quadratic negative response of milk fat content to trans-10 18:1 concentration was greater in MFD than in non-MFD conditions. In the two dietary conditions, the relationship between milk trans-10,cis-12 CLA or trans-10 18:1 and de novo fatty acid concentration in milk was negative, whereas the relationship with preformed fatty acid proportion was positive. The magnitude of changes in both milk fatty acid groups in response to changes in these trans-10 shift indicators were greater in non-MFD compared with MFD conditions. Milk fat yield and trans-10 shift indicators were only negatively related in ewes that were fed marine lipid supplements, because reductions in de novo fatty acid yield with increased shift indicator levels were not counteracted by concomitant increments in preformed fatty acid secretion. The best-fit (lower root mean squared error, higher R2 and no prediction biases) equations of milk fat or major milk fatty acid groups, as concentration or yield, were based on milk trans-10 18:1 concentration. In conclusion, different responses between the two conditions to similar shift indicator levels support that the trans-10 shift would not be a major factor explaining the diet-induced low-fat milk syndrome in dairy ewes., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2017-87812-R), co-funded by the European Regional Development Fund. P. G. Toral benefited from a Ramón y Cajal research contract from the MINECO (RYC-2015-17230), co-funded by the European Social Fund, and a researcher mobility grant from the University of León.

Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 160. 1-4 de diciembre, Virtual meeting (2020)., Ramón y Cajal program, RYC-2015-17230, MINECO/ESF, UE.

Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 176. 1-4 de diciembre, Virtual meeting (2020)., AGL2017-87812-R,AEI/FEDER, UE; Ramón y Cajal program, RYC-2015-17230, MINECO/ESF, UE.

Trabajo presentado al: 71st Annual Meeting of the European Federation of Animal Science (EAAP). Farming for carbon neutral livestock systems, 370. 1-4 de diciembre, Virtual meeting (2020)., Project CSI276P18, JCyL, FEDER and ESF, UE.

11 páginas, 5 tablas, 2 figuras., Isotopic tracers are used to directly quantify the effect of mammary Δ9-desaturation on milk fatty acid (FA) composition, but very few studies have applied this method to measuring the endogenous synthesis of rumenic acid (RA; cis-9,trans-11 conjugated linoleic acid) in cows and goats, and no publications exist in ewes. In sheep, knowledge about the contribution of stearoyl-coenzyme A desaturase (SCD) to milk FA secretion is derived mostly from indirect estimates based on inhibition of the enzyme by oral administration of cobalt, a cost-effective method that has not been validated to date. To fill both gaps, we conducted an isotopic tracer assay in sheep to quantify the proportion of endogenous RA in milk for the first time in this species. We then compared the results with estimates derived from a Co administration assay performed on the same animals. First, 5 lactating ewes received an intravenous injection of 200 mg of [1-13C]trans-11 18:1 (vaccenic acid, VA), the precursor for RA production by SCD activity. At −24, −15, 0, 9, 24, 33, 48, 57, 72, 81, and 96 h post-injection, we recorded milk yield and collected milk samples to examine fat concentration and FA profile. We conducted compound-specific isotope analysis of VA and RA by gas chromatography–combustion isotope ratio mass spectrometry. Afterward, in the Co administration assay, ewes received a daily dose of 7 mg of Co/kg of body weight for 5 d. We analyzed milk samples for composition before and on the last days of cobalt dosing. On average, 17% of the injected amount of [1-13C]VA was transferred to milk within 96 h post-injection, and up to 29% of the VA taken up by the mammary gland was desaturated to milk RA. Under our conditions, the mean proportion of this conjugated linoleic acid isomer deriving from Δ9-desaturation represented 82 to 90% of the amount secreted in milk. However, the proportion estimated in the Co assay with calculations based on individual FA concentrations was lower (on average, 46%). When we calculated the same estimates based on changes in Δ9-desaturation ratios after Co dosing, the higher values of endogenous RA (75%) did not differ from the results of the isotopic tracer assay. Nevertheless, correlation analysis between the results obtained through [1-13C]VA or Co administration revealed no significant relationship, which would prevent acceptance of the latter as a reliable alternative to isotopic labeling to examine mammary Δ9-desaturation in dairy ewes., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2017-87812-R), co-funded by the European Regional Development Fund. P. G. Toral benefits from a Ramón y Cajal research contract from the MINECO (RYC-2015-17230), co-funded by the European Social Fund. The authors thank V. Peiró and R. Redondo (Autonomous University of Madrid, Spain) for their contribution to isotope analysis.

9 páginas, 2 figuras, 1 tabla., The role of marine lipids as modulators of ruminal biohydrogenation of dietary unsaturated fatty acids may be explained by the effects of their n-3 polyunsaturated fatty acids (PUFA) on the bacterial community. However, the impact of individual PUFA has barely been examined, and it is uncertain which bacteria are truly involved in biohydrogenation. In addition, despite interspecies differences in rumen bacterial composition, we are not aware of any direct comparison of bovine and ovine responses to dietary PUFA. Therefore, rumen fluid from cannulated cattle and sheep were used as inocula to examine in vitro the effect of 20:5n-3 (EPA), 22:5n-3 (DPA), and 22:6n-3 (DHA) on the bacterial community. Amplicon 16 S rRNA sequencing suggested that EPA and DHA had a greater contribution to the action of marine lipids than DPA both in cattle and sheep. Certain effects were exclusive to each ruminant species, which underlines the complexity of rumen microbial responses to dietary fatty acids. Based on changes in bacterial abundance, Barnesiella, Prevotella, Paraprevotella, Hallela, Anaerovorax, Succiniclasticum, Ruminococcus and Ruminobacter may be involved in the ruminal response in biohydrogenation to the addition of marine lipids, but further research is necessary to confirm their actual role in ruminal lipid metabolism., 54587-R and AGL2017-87812-R). D. Carreño benefited from an FPI predoctoral grant (BES-2012-054972) and P. G. Toral from a Ramón y Cajal research contract (RYC-2015-17230), both from the MINECO. Co-funding by the European Regional Development Fund and the European Social Fund is also acknowledged.

6 páginas, 1 tabla.-- Contributed to: Innovation for Sustainability in Sheep and Goats, 2nd Joint Seminar of the Subnetworks on Nutrition and on Production Systems of the FAO-CIHEAM Network for Research and Development in Sheep and Goats. Ruiz R., López-Francos A., López Marco L. (Eds). Vitoria-Gasteiz (Spain), 3-5 October 2017. Marine lipid supplements have been used to inhibit the ruminal saturation of trans-11 18:1, with the final goal of enhancing cis-9 trans-11 conjugated linoleic acid (CLA) concentration in milk and meat. This response would be largely explained by the effects of n-3 very long chain polyunsaturated fatty acids (PUFA) on the last step of biohydrogenation (BH). In cows, docosahexaenoic acid (DHA, 22:6n-3) has been suggested to be a stronger inhibitor of trans-18:1 hydrogenation than eicosapentaenoic acid (EPA, 20:5n-3), but information about changes in individual 18:1 isomers is very limited, and no reports are available in sheep. This in vitro study was therefore conducted to compare the impact of EPA and DHA on the BH of 18-carbon fatty acids in ovine, using batch cultures of rumen microorganisms and cannulated ewes as inocula donors. The two PUFA were added at a dose of 2% incubated DM and effects were examined after 24 h of incubation. The DHA treatment led to the greatest concentration of trans-18:1 in digesta, but this was mainly accounted for by accumulation of metabolites from alternative BH pathways (e.g, trans-9, -10, -12 and -15 18:1), while the inhibition of trans-11 18:1 saturation was comparable with both PUFA. The saturation of cis-18:1 was constrained too, particularly by DHA, whereas EPA seemed to have specific effects on 18:3n-3 metabolism. Changes in oxo-FA concentrations suggested that ruminal hydration (an alternative metabolic pathway to BH) was also affected by PUFA treatments. The work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC; AGL2014-54587-R). P. G. Toral and D. Carreño received Ramón y Cajal and FPI contracts from the MEIC. Co-funding by the European Regional Development Fund is also acknowledged.

13 páginas, 5 tablas, 3 figuras., The lactational effects of shearing (CO, control unshorn; SH, shorn) were investigated in 48 dairy ewes of 2 breeds (Lacaune, LC, n = 24; Manchega, MN, n = 24) having a similar stage of lactation (120 ± 6 d in milk) and body frame (65.1 ± 1.5 kg of body weight and 2.4 ± 0.1 body condition score), but differing in fleece and milk production. Ewes were penned indoors, adapted to the diet (alfalfa hay ad libitum and fixed amount of concentrate), and allocated for 30 d in 8 balanced groups to which the experimental treatments were applied. All ewes were sheared on the same day. Feed intake by pen and milk yield by ewe were recorded daily. Individual samples of milk (d −3, 3, 5, 7, and 15) and blood (d −7, 3, 7, and 15) were collected, as well as body weight and body condition score measured (d −15, 0, and 15), related to shearing. Pooled milk samples per pen were also collected before and after shearing for milk fatty acid analysis (d −3 and 15). Average temperatures in the barn before (12.6 ± 0.7°C) and after (13.7 ± 0.4°C) shearing were mild. Fleece was heavier in MN than in LC (1.04 ± 0.10 vs. 0.75 ± 0.09 kg/ewe) and tended to cover more body surface in MN than in LC ewes. Responses to shearing varied according to breed, the rectal temperature after shearing only decreasing significantly in the MN (−0.36 ± 0.09°C). Feed intake increased in the LC-SH (5%), when compared with LC-CO, but did not vary in the MN ewes. Ingestibility of the alfalfa hay, expressed as filling units for sheep and monitored in 2 groups of 6 dry and unshorn ewes of each breed (73.0 ± 2.5 kg of body weight and 3.1 ± 0.2 body condition score), was constant throughout the experiment (0.99 ± 0.03 filling units for sheep/kg of dry matter). Regarding milk production, LC-SH ewes yielded 10% more milk (1.38 ± 0.06 vs. 1.52 ± 0.05 kg/d) than LC-CO ewes, but no differences were detected in MN ewes (0.74 ± 0.03 kg/d, on average). No differences in the concentration of major milk components by effect of the shearing treatment were detected in either breed, but LC-SH ewes yielded 9% more milk protein than did LC-CO ewes. No relevant effects of shearing were detected on milk fatty acid profiles, although MN ewes showed lower C4:0, C6:0, C14:0, trans-11 and trans-12 C18:1 contents than did LC ewes. Moreover, no changes by effect of shearing were detected in plasma glucose, nonesterified fatty acids, cortisol, or insulin values in either breed, or in body weight or body condition score. In conclusion, shearing dairy ewes during lactation under mild winter conditions is a suitable management option that may increase feed intake and milk production, without deleterious effects on milk composition., This work is part of a research project of the Plan Nacional I+D+i Retos 2013 (Project AGL2013-44061-R) funded by the Spanish Ministry of Economy and Competitiveness (Madrid, Spain) and was also supported by a research scholarship to Abdelaali El Hadi from the International Centre for Advanced Mediterranean Agronomic Studies (Instituto Agronómico Mediterráneo de Zaragoza, Zaragoza, Spain). The authors are also grateful to Ramon Costa and the team of the SGCE (Servei de Granges i Camps Experimentals) of the Universitat Autònoma de Barcelona (Bellaterra, Barcelona, Spain) for the care of the animals and to Charles (Chuck) Simmons, native English-speaking university instructor (Cerdanyola, Barcelona, Spain) for the English language and style revision of the manuscript

Trabajo presentado al: XIIIth International Symposium on Ruminant Physiology (ISRP), P 68. 3-6 de septiembre de 2019. Leipzig (Alemania)., Despite their bad reputation among some nutritionists, it is nowadays widely accepted that tannins can be used as additives to modulate rumen fermentation. However, there is a void of information about which of the many types of tannins and at which doses may be more useful for a particular purpose. Furthermore, little is known about potential synergistic effects of different combinations of tannins. An in vitro assay with batch cultures of rumen microorganisms, using cannulated ewes as donors of rumen inocula, was performed to try to move forward on this subject. Commercial extracts of quebracho, oak and grape tannins, at doses selected from a previous study were combined following a simplex centroid design (in total, 10 combinations plus 1 control without tannins) and added to the incubation substrate (a total mixed ration based on alfalfa hay and concentrates, with 27% of starch and a F:C ratio of 40:60). Results suggested that there might be a synergistic effect of the combinations. For instance, none of the tannin extracts alone altered methane production, while some mixtures (mentioned below) did it, and the reductions of NH3-N, which would support a protection of dietary protein against ruminal degradation, were higher when combinations were used. Considering all the results together, we selected the next 3 treatments as the most convenient (doses are reported as % of incubated DM; real amounts after considering the simplex centroid design). Combination 1: 1.7% oak + 0.85% grape. This treatment induced lower gas and methane productions, ammonia-N concentration and molar proportion of minor volatile fatty acids (VFA; namely isobutyrate, isovalerate, valerate and caproate). Combination 2: 1.13% quebracho + 1.13% oak + 0.57% grape. Although this treatment affected negatively the ruminal disappearance of NDF (-8%), which would challenge its selection, it reduced gas and methane productions, ammonia-N concentration and molar proportion of minor VFA, as well as the acetate/propionate (A/P) ratio, and also increased the molar proportion of propionate. Combination 3: 0.57% quebracho + 2.27% oak + 0.28% grape. It reduced gas and methane productions, ammonia-N concentration, molar proportion of minor VFA, and the A/P ratio. This was the treatment with the strongest effect on NH3-N concentration (-22%). It also increased molar proportions of propionate and acetate, and it did not exert non-desirable effects on the in vitro ruminal fermentation parameters that were investigated. In closing, an appropriate combination of tannins may improve ruminant diet utilization while reducing methane emissions.

3 páginas, 1 tabla.- Trabajo presentado al: XVIII Jornadas sobre Producción Animal AIDA. Zaragoza, España, 7-8 mayo 2019., Este trabajo se financió con fondos del contrato de investigación VATC-20160394. P. G. Toral disfruta de un contrato Ramón y Cajal del MINECO con apoyo del Fondo Social Europeo.

3 páginas, 3 tablas.- Trabajo presentado al: XVIII Jornadas sobre Producción Animal AIDA. Zaragoza, España, 7-8 mayo 2019., P. G. Toral disfruta de un contrato Ramón y Cajal (RYC-2015-17230) del MINECO, cofinanciado por el Fondo Social Europeo.

3 páginas, 1 tabla.- Trabajo presentado al: XVIII Jornadas sobre Producción Animal AIDA. Zaragoza, España, 7-8 mayo 2019., P. G. Toral disfruta de un contrato Ramón y Cajal (RYC-2015-17230) del MINECO, cofinanciado por el Fondo Social Europeo.

31 páginas, 5 tablas, 2 figuras.- Este trabajo ha recibido el VI Premio Fundación CESFAC otorgado por la Real Academia de Ciencias Veterinarias de España., [EN] Intensive ruminant feeding systems are highly dependent on soybean meal as the source of protein, which encourages to search for alternatives. The use of insects has been suggested as one of these alternatives, but to date there are very few scientific reports characterizing this type of feeds. Furthermore, and given that the extent of ruminal degradation of insect meals is still unknown, we considered the use of tannins to try to limit it, thus improving its digestive utilization. This study was therefore performed with two objectives: 1) to conduct a protein evaluation of several insect meals using different techniques (in vitro and in situ) and 2) to study if the use of tannins could reduce the ruminal degradation of insect meal protein without affecting its intestinal digestibility. On this basis, 2 trials were performed using 4 insect meals: Tenebrio molitor, Zophobas morio, Alphitobius diaperinus and Acheta domesticus. In addition, soybean meal was used as a reference feed. Results confirmed the potential of insect meals as alternative ingredients to traditional sources of protein. Regardless of the protein evaluation method, all insect meals showed lower degradations than soybean meal. Furthermore, both oak and quebracho tannin extracts reduced the in situ ruminal degradation in all cases. The intestinal digestibility of the protein was high for all insects, being higher after the treatment with oak tannins than with quebracho tannins., [ES] Los sistemas intensivos de alimentación de rumiantes tienen una gran dependencia de la torta de soja como fuente de proteína, lo que hace necesaria la búsqueda de alternativas. Una de ellas es el empleo de insectos, pero, hasta la fecha, existen muy pocos trabajos científicos al respecto. Por otro lado, y dado que se desconoce aún cuán elevada puede ser la degradación ruminal de las harinas de insectos, nos planteamos el uso de taninos para poder limitarla y mejorar así su utilización digestiva. Por lo tanto, este estudio se realizó con dos objetivos: 1) realizar una valoración proteica de varias harinas de insectos mediante diversas técnicas (in vitro e in situ) y 2) estudiar si el uso de taninos podría reducir la degradación ruminal de la proteína de estas harinas sin afectar a su digestibilidad intestinal. Para cumplirlos, realizamos 2 ensayos con 4 harinas de insectos: Tenebrio molitor, Zophobas morio, Alphitobius diaperinus y Acheta domesticus. Además, utilizamos torta de soja como alimento de referencia. Los resultados confirmaron el potencial de los insectos como ingredientes alternativos a las fuentes tradicionales de proteína. Independientemente del método de empleado, todos los insectos mostraron valores de degradación más bajos que la torta de soja. Además, el tratamiento con extractos de taninos de roble o quebracho redujo la degradación ruminal in situ en todos los casos. La digestibilidad intestinal de la proteína in vitro fue alta en todos los insectos, siendo los valores siempre mayores en el tratamiento con taninos de roble que de quebracho.

XIIIth International Symposium on Ruminant Physiology (ISRP), P 27. 3-6 de septiembre de 2019. Leipzig (Alemania)., Diet-induced milk fat depression (MFD) is presumably caused by the effects of ruminal biohydrogenation intermediates with antilipogenic activity. However, in marine lipid-induced MFD the involvement of t10c12-CLA, which is the only intermediate shown unequivocally to inhibit milk fat synthesis in ruminants, has been questioned, particularly in sheep. Thus, we conducted a meta-analysis to summarize the relationship between milk t10c12-CLA concentration and milk fat traits in lactating ewes. A database comprising 23 trials conducted by our team has been used. Fifty-five dietary conditions were characterized and grouped in two major categories (experimental treatments): non-MFD and marine lipid-induced MFD. The non-MFD category included 40 diets without supplementation or supplemented with plant oils and extracts, which modified the fatty acid profile of milk without detrimentally affecting milk fat synthesis. The marine lipid-induced MFD group comprised 15 diets supplemented with fish oil or microalgae. To ensure stable responses to diets, only the data collected after 21 or more days of adaptation were considered. Differences in diet formulation and chemical composition between the two groups of experimental treatments (non-MFD and MFD) were analyzed by one-way ANOVA. Linear and quadratic relationships between milk fat traits (yield and concentration of fat and yield of de novo synthesized and preformed fatty acids) and milk t10c12-CLA levels were examined using the MIXED procedure of SAS. Diet characteristics that may influence the response to lipid supplementation (e.g., forage:concentrate ratio, fibre concentration or starch content) did not differ between marine lipid-induced MFD and non-MFD groups. Prediction models showed an inverse linear relationship between t10c12-CLA and milk fat concentration in both treatments (R2=0.78; P0.10 for the treatment × t10c12-CLA level interaction). Similarly, milk fat yield was 23% lower in MFD than in non-MFD conditions (P, Spanish MINECO (AGL2017-87812 and Ramón y Cajal program) and European Regional Development Fund.

5 páginas, 2 tablas.--Contributed to: Efficiency and resilience of forage resources and small ruminant production to cope with global challenges in Mediterranean areas, Proceedings of the 1st Joint Meeting of the FAO-CIHEAM Network for Research and Development in Sheep and Goats (Subnetworks on Nutrition and Production Systems) and the FAO-CIHEAM Subnetwork on Mediterranean Forage Resources. López-Francos A., Jouven M., Porqueddu C., Ben Salem H., Keli A., Araba, A. and Chentouf M. (Eds.). Meknes (Morocco), 23-25 October 2019., [EN] Due to the high dependence of ruminant feeding systems on the use of soybean meal as source of protein, insect meals have been suggested as a promising alternative. However, a high rumen degradability might be a drawback for its utilisation. In this regard, tannins are known to be able to exert beneficial effects on the digestive utilization of protein-rich feeds due to a reduction of their degradation in the rumen, especially of the protein, although they might also restrict intestinal digestibility. Therefore, this experiment was conducted to examine if tannins could improve the digestive utilization of 4 insect meals (from Acheta domesticus, Alphitobius diaperinus, Tenebrio molitor and Zophobas morio). To this aim, four ruminally cannulated sheep were used to study the ruminal degradation and intestinal digestibility of these feedstuffs as well as those of soybean meal, which was used as a reference. The five substrates were treated with either 0% (control) or 15% DM of commercial tannin extracts from oak (OAK) or quebracho (QUE), and incubated in situ for 16 h. Afterwards, the intestinal digestibility of non-degraded protein was estimated in vitro. Both oak and quebracho tannins were able to protect the protein of insect meals from ruminal degradation, following a similar pattern than that observed in soybean meal. On average, reductions were about 15%, with no significant differences between oak and quebracho effects. On the opposite, the OAK treatment might offer advantages over QUE in terms of intestinal protein digestibility, as the latter caused a lower value in A. domesticus compared with the control. More research would be advisable to confirm these results, particularly in vivo, [FR] . En raison de la forte dépendance à l’utilisation de tourteau de soja comme source de protéines dans les systèmes d’alimentation des ruminants, la farine d’insectes a été suggérée comme une alternative prometteuse. Cependant, une forte dégradation de sa protéine dans le rumen pourrait constituer un inconvénient à son utilisation. À cet égard, les tanins peuvent avoir des effets bénéfiques sur l’utilisation digestive des aliments riches en protéines, en réduisant leur dégradation dans le rumen, même si ils peuvent limiter la digestibilité intestinale. Par conséquent, cet essai a été mené afin d’examiner si les tanins pouvaient améliorer l’utilisation digestive de 4 farines d’insectes (provenant d’Acheta domesticus, Alphitobius diaperinus, Tenebrio molitor et Zophobas morio). Pour ce faire, quatre moutons munis d’une canule ruminale ont été utilisés afin d’étudier la dégradation ruminale et la digestibilité intestinale de ces aliments, en comparaison avec celles du tourteau de soja (aliment de référence). Les cinq substrats ont été traités avec 0 (témoin) ou 15% MS des extraits commerciaux de tanin de chêne (OAK) ou de quebracho (QUE) et par la suite ils ont été incubés in situ pendant 16 h. Ensuite, la digestibilité intestinale de la protéine non dégradée a été estimée in vitro. Les tanins de chêne et de quebracho ont permis de protéger la protéine des farines d’insectes de la dégradation ruminale, en suivant une tendance similaire à celle observée pour le tourteau de soja. En moyenne, la réduction de la dégradation protéique a été d’environ 15%, sans différence significative entre les effets du chêne et du quebracho. Au contraire, en termes de digestibilité intestinale des protéines, le traitement OAK pourrait offrir des avantages par rapport à QUE, puisque ce dernier a entrainé une valeur inférieure pour A. domesticus par rapport au contrôle. D’autres recherches seraient requises pour confirmer ces résultats, particulièrement en conditions in vivo, P. G. Toral received a contract (RYC-2015-17230) from the MINECO, co-funded by the ESF.

7 páginas, 1 tabla.--Contributed to: Innovation for Sustainability in Sheep and Goats, 2nd Joint Seminar of the Subnetworks on Nutrition and on Production Systems of the FAO-CIHEAM Network for Research and Development in Sheep and Goats. Ruiz R., López-Francos A., López Marco L. (Eds). Vitoria-Gasteiz (Spain), 3-5 October 2017., Despite the benefits of using marine lipid supplements in dairy ewe diets to modulate milk fatty acid (FA) composition, this strategy causes milk fat depression (MFD), which precludes its use under farm conditions. One theory trying to explain this type of MFD attributes the depression to an impaired capacity of the mammary gland to achieve an adequate melting point for milk fat secretion. This alteration of fluidity has been linked to a shortage of available ruminal 18:0 caused by the consumption of marine lipids. However, in a previous study, we were not able to prevent the effects of fish oil supplementation through concomitant dietary addition of stearic acid (2% DM). Yet, before ruling out a mechanism based on milk fat fluidity, we decided to try with a higher dose of 18:0. Thus, this assay was conducted with 12 lactating ewes divided in 3 treatments that lasted for 4 weeks: a total mixed ration without lipid supplementation (control) or supplemented with 20 g/kg DM of fish oil alone (FO) or in combination with 40 (FOSA-4) g/kg DM of 18:0. As expected, FO supplementation modified milk FA composition towards a healthier profile for consumers but, at the same time, reduced milk fat concentration. This MFD was not alleviated by the dietary addition of 4% 18:0 (FOSA-4). Depression of milk fat is discussed in relation to milk FA composition, particularly to the concentration of main metabolites responsible for changes in the melting point and fluidity of fat (i.e., 18:0 and cis-9 18:1)., P.G. Toral Received a Ramón y Cajal contract from the Spanish Ministry of Economy, Industry and Competitiveness.

3 páginas, 1 figura.- Trabajo presentado al: XVIII Jornadas sobre Producción Animal AIDA. Zaragoza, España, 7-8 mayo 2019., Este trabajo forma parte del proyecto AGL2017-87812 del MINECO, cofinanciado por el FEDER. P. G. Toral disfruta de un contrato Ramón y Cajal también del MINECO (RYC-2015-17230) y cofinanciado por el FSE.

Trabajo presentado al: XIIIth International Symposium on Ruminant Physiology (ISRP), P 191. 3-6 de septiembre de 2019. Leipzig (Alemania)., Improvements in sustainability include the enhancement of feed efficiency, which in ruminant livestock might be associated with the diversity of the rumen microbiome. Results in the literature are inconsistent; efficient animals have been related with both high and low microbial diversity. However, no studies are available in dairy ewes. Therefore, we aimed at examining the relationship between feed efficiency, measured as residual feed intake (RFI), and rumen bacterial diversity in lactating sheep. The latter was estimated through the richness, Shannon and evenness indices, using T-RFLP and 3 enzymes: HhaI, MspI and HaeIII. The RFI is defined as the difference between the actual and expected feed intake, which was determined from feed requirements for maintenance and lactation according to the AFRC system. Animals with lower RFI eat less than predicted, being more efficient. Data from two studies performed by our team (with 20+15 animals fed a 50:50 F:C diet) were employed. Regression analyses were conducted to investigate the link between RFI and diversity measures. RFI averaged 0.29±0.062 (range: -0.75 to 1.01) and showed no significant relationship with most diversity indices. However, trends to significance (P, MINECO (AGL2017-87812 and programme Ramón y Cajal), JCyL (CSI276P18), FEDER and FSE.

14 páginas, 6 tablas., This study was funded by the Instituto de Ganadería de Montaña (CSIC-University of León, Spain) and the University of Perugia (Department DSA3; project “Ricerca di Base – 2015”). P. G. Toral benefits from a ‘Ramón y Cajal’ research contract (MINECO-European Regional Development Fund).

Shifts in ruminal oleic acid (OA) metabolism have received little research attention but recent studies have suggested their association with marine lipid-induced milk fat depression (MFD) in ewes and cows. Measurement of specific products of OA within the complex mixture of digesta lipids is however challenging. Therefore, this in vitro trial combined the isotopic labelling technique with the use of rumen inoculum from cannulated sheep fed a diet supplemented or not with 2% of fish oil (which has been demonstrated to cause MFD in dairy ruminants) to characterize the metabolism of OA in response to ruminal alterations associated with MFD. The products of 13C-OA after 24 h of incubation were analysed by gas chromatography-combustion isotope ratio mass spectrometry (GC-C-IRMS). Numerous 13C-labeled 18:1 intermediates and oxygenated FA were detected and no elongation or desaturation of 13OA occurred. Diet supplementation with fish oil (i.e., MFD conditions) resulted in no unique metabolites of 13OA but in relevant changes in the relative contribution of specific metabolic pathways. The inhibition of 18:0 saturation caused by this treatment appeared largely attributable to increased oxygenated FA proportion, in particular the candidate milk fat inhibitor 10-oxo-18:0, and warrants further research on the association between MFD and oxygenated FA. Changes in the concentration of 13C-labeled trans 18:1 intermediates but not in cis 18:1, were also observed., This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2017-87812). P. G. Toral benefits from a Ramón y Cajal research contract from the MINECO (RYC-2015-17230). Co-funding by the European Regional Development Fund is also acknowledged.

16 páginas, 5 figuras., Tannins are a large, diverse and complex group of phenolic compounds that may be detrimental, innocuous or beneficial to animal nutrition and health depending on a number of factors (e.g., type, amount ingested, consumer animal species or the basal diet). The ability of tannins to modulate ruminal biohydrogenation and, consequently, the fatty acid (FA) composition of milk and meat is a relatively recent finding that has attracted interest among ruminant nutritionists. In this review, we take a close look at the effects of tannins on the broadest possible range of FA, including less abundant compounds that have previously received little attention. Tannins are able to improve the concentrations of potentially beneficial FA, such as 18:3n-3, 18:2n-6, trans-11 18:1 and conjugated linoleic and linolenic acids, both in milk and meat, which may contribute to meeting consumer demand for health-promoting foods. These positive responses to tannins can be explained by their modulatory action on specific biohydrogenation steps and pathways. Thus, higher contents of dietary polyunsaturated FA in ruminant-derived products, as well as increased or decreased accumulation of other biohydrogenation intermediates (e.g., cis and trans 18:3, 18:2 and 18:1 isomers) and changes in lipids of bacterial origin (odd- and branched-chain FA and dimethylacetals), are somewhat common findings when the effects of tannins are examined. In contrast, de novo synthesized FA are less frequently affected by these plant secondary metabolites, which also applies to other FA (e.g., trans-10 18:1) that might be detrimental to animal performance (i.e., milk fat synthesis) and perhaps to human health. However, further studies are required to unravel the reasons for certain erratic responses to tannins. This paper reviews the roles of tannin chemical and structural diversity, dosage, interaction with other dietary ingredients, differences among ruminant species and variations over time in the reaction of rumen microbiota in the influences of these phenolic compounds on milk and meat FA profiles., P. G. Toral benefited from a Ramón y Cajal research contract from the MINECO (RYC-2015-17230), co-funded by the European Social Fund.

Póster presentado al: 10th International Symposium on the Nutrition of Herbivores (ISNH).--Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p. 389. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Dietary addition of EPA, DPA, and DHA altered the abundance of several bacterial genera, such as Prevotella, Hallella, Paraprevotella and Succiniclasticum, that might participate in rumen biohydrogenation., Support by the Spanish MINECO (AGL2014-54587 and AGL2017-87812] and the European Regional Development Fund is acknowledged. D. Carreño benefits from a FPI and P. G. Toral from a Ramón y Cajal research contract.

Póster presentado al: 10th International Symposium on the Nutrition of Herbivores (ISNH).--Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p. 456. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Comparison of genes downregulated in lactating ewes showing CLA- or fish oil-induced milk fat depression highlights the involvement of several genes related to mammary lipogenesis., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2014-54587-R and AGL2015-66035-R). P. G. Toral and B. Gutierrez-Gil benefit from Ramón y Cajal research contracts. Cofunding by the European Regional Development Fund is also acknowledged.

1 página.--Trabajo presentado al Proceedings of the Fifth Dairycare Conference 2018, p. 21 (#9). Thessalonika (Grecia),19-20 de marzo de 2018., Requirements of high producing ruminants can only be covered by diets of high nutritive value that can induce subacute rumen acidosis (SARA), but not for all animals at the same time and with the same intensity. A challenge is to find noninvasive biomarkers to detect animals suffering from SARA. Milk fatty acids composition is a good candidate as it is partly linked to rumen metabolism. The aim of this work was to compare two methods of measure of milk fatty acids composition: gas chromatography (GC) considered as a “standard”, but a time-consuming and expensive method and medium infrared analysis (MIR), a rapid and cheap method which can be applied on field. Eight rumen cannulated dairy goats adapted to a low concentrate diet (20 %) were abruptly switched to a high concentrate diet (50 %). Samples of milk were taken individually on the morning for 2 days before the change, the 4 days following the change and once weekly for 3 weeks. 91 fatty acids were detected by GC and 58 were estimated by MIR. Rumen fluid was sampled simultaneously before the morning feed (T0) and 1, 2, 4 and 6 hours after. Rumen samples were analysed for pH and volatile fatty acid (VFA) composition. A principal component analysis (PCA) was used to examine the relationships among milk fatty acids percentages measured by GC. The projection of the saturated fatty acids on the first two components showed an opposition between the short and medium fatty acids (SMFA) up to 13C and the long (L) chain fatty acids (LFA). An index was calculated as the ratio of SMFA/LFA. It was positively linked to the pH values and negatively to [VFA] ones. A similar ratio was calculated from the MIR estimation. Even if both ratios were correlated (r = 0.60, n = 72), the MIR ratio was higher (0.72 ± 0.06) than the GC ratio (0.50 ± 0.05) and was not correlated with pH and only poorly with VFA. MIR overestimated SMFA and underestimated LFA. In conclusion, GC is a useful tool to detect SARA in dairy goats from milk composition, but MIR is not a relevant method due to the inaccuracy in the prediction of FA.

Resumen de la Comunicación oral al congreso e invitada: 10th International Symposium on the Nutrition of Herbivores (ISNH).-- Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p.766. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Growth in demand for foods with potentially beneficial effects on consumer health has motivated increased interest in developing strategies for improving the nutritional quality of ruminant-derived products. Manipulation of the rumen environment offers the opportunity to modify the lipid composition of milk and meat by changing the availability of fatty acids (FA) for mammary and intramuscular lipid uptake. Dietary supplementation with marine lipids, plant secondary compounds and direct-fed microbials has shown promising results. In this review, we have compiled information about their effects on the concentration of putative desirable FA (e.g., c9t11-conjugated linoleic acid and vaccenic, oleic, linoleic and linolenic acids) in ruminal digesta, milk and intramuscular fat. Marine lipids rich in very long-chain n-3 polyunsaturated fatty acids (PUFA) efficiently inhibit the last step of C18 FA biohydrogenation (BH) in the bovine, ovine and caprine, increasing the outflow of t11-18:1 from the rumen and improving the concentration of c9t11-18:2 in the final products, but increments in t10-18:1 are also often found due to shifts toward alternative BH pathways. Direct-fed microbials appear to favourably modify rumen lipid metabolism but information is still very limited, whereas a wide variety of plant secondary compounds, including tannins, polyphenol oxidase, essential oils, oxygenated FA and saponins, has been examined with varying success. For example, the effectiveness of tannins and essential oils is as yet controversial, with some studies showing no effects and others a positive impact on inhibiting the first step of BH of PUFA or, less commonly, the final step. Further investigation is required to unravel the causes of inconsistent results, which may be due to the diversity in active components, ruminant species, dosage, basal diet composition and time on treatments. Likewise, research must continue to address ways to mitigate negative side-effects of some supplements on animal performance (particularly, milk fat depression) and product quality (e.g., altered oxidative stability and shelf-life).

Póster presentado al: 10th International Symposium on the Nutrition of Herbivores (ISNH).--Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p. 459. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Pomegranate by-products can be used to enhance the content of potentially health-promoting fatty acids in ruminant meat and milk. Specific effects may vary depending on the by-product used., This study was supported by the VATC-20160394 research project (IGM, Leon).

10 páginas, 2 tablas., Growth in demand for foods with potentially beneficial effects on consumer health has motivated increased interest in developing strategies for improving the nutritional quality of ruminant-derived products. Manipulation of the rumen environment offers the opportunity to modify the lipid composition of milk and meat by changing the availability of fatty acids (FA) for mammary and intramuscular lipid uptake. Dietary supplementation with marine lipids, plant secondary compounds and direct-fed microbials has shown promising results. In this review, we have compiled information about their effects on the concentration of putative desirable FA (e.g. c9t11-CLA and vaccenic, oleic, linoleic and linolenic acids) in ruminal digesta, milk and intramuscular fat. Marine lipids rich in very long-chain n-3 polyunsaturated fatty acids (PUFA) efficiently inhibit the last step of C18 FA biohydrogenation (BH) in the bovine, ovine and caprine, increasing the outflow of t11-18:1 from the rumen and improving the concentration of c9t11-CLA in the final products, but increments in t10-18:1 are also often found due to shifts toward alternative BH pathways. Direct-fed microbials appear to favourably modify rumen lipid metabolism but information is still very limited, whereas a wide variety of plant secondary compounds, including tannins, polyphenol oxidase, essential oils, oxygenated FA and saponins, has been examined with varying success. For example, the effectiveness of tannins and essential oils is as yet controversial, with some studies showing no effects and others a positive impact on inhibiting the first step of BH of PUFA or, less commonly, the final step. Further investigation is required to unravel the causes of inconsistent results, which may be due to the diversity in active components, ruminant species, dosage, basal diet composition and time on treatments. Likewise, research must continue to address ways to mitigate negative side-effects of some supplements on animal performance (particularly, milk fat depression) and product quality (e.g. altered oxidative stability and shelf-life)., This work was conducted within the framework of the research projects AGL2014-54587 and AGL2017-87812 (Spanish Ministry of Economy and Competitiveness, MINECO). P.G.T. benefited from a Ramón y Cajal research contract (RYC-2015-17230, MINECO).

Póster presentado al: 10th International Symposium on the Nutrition of Herbivores (ISNH).--Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p. 435. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Individual milk fatty acid composition is a good biomarker in dairy goats to detect status of rumen fermentation patterns. According to this purpose, it can be used to phenotype dairy goats susceptibility to acidosis., This research was partially supported by grants from Idele in the project CASDAR rfi AcID 1310. The authors thank J. Tessier and his colleagues from Inra-AgroParisTech experimental farm for taking care of the goats.

Póster presentado al: 10th International Symposium on the Nutrition of Herbivores (ISNH).--Herbivore nutrition supporting sustainable intensification and agro-ecological approaches.-- p. 389. 2-6 de septiembre de 2018. Clermont-Ferrand (Francia)., Individual variation in the severity of milk fat depression cannot be explained by a single mechanism (e.g., changes in rumen VFA or biohydrogenation metabolites) but most probably by a complex combination of factors., This work was supported by the Spanish MINECO (AGL2014-54587-R). P. G. Toral benefits from a Ramón y Cajal research contract. Cofunding by the European Regional Development Fund is also acknowledged.

13 páginas, 4 figuras, 2 tablas., A great deal of uncertainty still exists about intermediate metabolites and pathways explaining the biohydrogenation (BH) of 20- and 22-carbon polyunsaturated fatty acids (PUFA). Therefore, this study was conducted to provide further insight into the ruminal metabolism of 20:5 n-3 (EPA), 22:5 n-3 (DPA), and 22:6 n-3 (DHA), the main n-3 PUFA present in the marine lipids used in dairy ruminant feeding, and to examine potential differences between bovine and ovine. To meet this aim, we investigated the 20- and 22-carbon metabolites accumulated during in vitro incubation of EPA, DPA, and DHA with rumen inocula from cows and ewes. The PUFA were added at a dose of 2% incubated dry matter and digesta samples were analyzed after 24 h of incubation using complementary gas-liquid chromatography of fatty acid methyl esters and gas chromatography-mass spectrometry of 4,4-dimethyloxazoline derivatives. Results suggested that the main BH pathway of EPA and DPA would proceed via the reduction of the double bond closest to the carboxyl group (cis-5 in EPA and cis-7 in DPA); curiously, this mechanism seemed of much lower importance for DHA. Thus, DPA would not be a major intermediate product of DHA and their BH might actually follow separate pathways, with the accumulation of numerous unique metabolites in each case. A principal component analysis supported this hypothesis, with a clear separation between PUFA treatments in the score and loading plots. Within EPA and DPA groups, cow and ewe samples loaded separately from each other but not distant. No conjugated 20:5, 22:5, or 22:6 isomer compatible with the initial product of EPA, DPA, or DHA metabolism, respectively, was identified in the ruminal digesta, although this would not unequivocally exclude their transient formation. In this regard, results from DPA incubations provided the first indication that the metabolism of this very long chain PUFA may involve the formation of conjugated double bond structures. The BH of EPA, DPA, and DHA resulted in the appearance of several tentative trans-10-containing metabolites, showing a general trend to be more abundant in the digesta of ewes than in that of cows. This finding was speculated to have some relationship with the susceptibility of dairy sheep to marine lipid-induced milk fat depression. Differences in the relative proportion of intermediate products would also suggest an influence of ruminant species on BH kinetics, with a process that would likely be slower and less complete in cows than in ewes. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved., This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO; AGL2014- 54587-R). P. G. Toral benefited from a Ramón y Cajal research contract from the MINECO. Co-funding by the European Regional Development Fund is also acknowledged.

Tesis de máster del Instituto de Ganadería de Montaña (IGM-CSIC-ULE). Departamento de Nutrición y Producción de Herbívoros; Cnetro Internacional de Altos Estudios Agronómicos Mediterráneos (CIHEAM); Instituto Agronómico Mediterráneo de Zaragoza (IAMZ).--Octubre 2015., [EN] There is still controversy surrounding the ability of tannins to modulate the process of biohydrogenation (BH) of fatty acids (FA) in the rumen and improve the lipid profile of milk or meat without conferring a negative response in the digestive utilization of the diet. Based on this, the current work was performed with the aim of investigating the effect of dietary tannins (particularly those from sainfoin -Onobrychis viciifolia- hay) on the BH of linoleic (18:2n-6) and linolenic (18:3n-3) acids and on the ruminal fermentation. This study was carried out in vitro, using batch cultures of rumen microorganisms and the gas production technique. Rumen cannulated sheep were used as donors of microbial inocula. Two legume hays, alfalfa (virtually free of tannins) and sainfoin (with a similar chemical composition but containing 3.5% total tannins, expressed as tannic acid equivalents), were utilized as incubation substrates. Both hays were enriched with either sunflower oil (as a source of linoleic acid) or linseed oil (as a source of linolenic acid). The analytical techniques included the determination of tannins, of the lipid profile of rumen contents (focused primarily on relevant metabolites such as 18:0, trans-11, trans-10 and cis-9 18:1, cis-9 trans-11 18:2 -the main isomer of the conjugated linoleic acid; CLA-, trans-11 cis-15 18:2, 18:2n-6 and 18:3n-3) and of some rumen fermentation parameters (e.g., gas production, ammonia concentration, dry matter disappearance, etc.). Most results related to intermediate BH metabolites (e.g., greater concentrations of 18:3n-3, 18:2n-6, trans-11 cis-15 18:2, cis-9 18:1 or total polyunsaturated FA in sainfoin incubations) show the ability of this legume, possibly due to its tannin content, to inhibit the ruminal BH of dietary unsaturated FA. On the other hand, no significant differences (P>0,10) were detected in the accumulation of cis-9 trans-11 CLA, total CLA or 18:0, and variations in trans-11 18:1 did not follow a regular pattern. Regarding the rumen fermentation, it was observed that gas production was lower in the incubations with sainfoin hay (-17%), which is consistent with previous findings when using tannins. Accordingly, ammonia concentrations and total volatile fatty acid (VFA) production also presented smaller values with sainfoin (-23% and -11%, respectively); differences in VFA being especially clear in the molar proportions of butyrate and valerate. Overall, the study shows the ability of Onobrychis viciifolia, probably by means of its moderate tannin content, to modify the ruminal BH of dietary unsaturated FA, which could result in improvements in the lipid profile of final products (meat and milk). Nonetheless, the present results are not as promising as expected or as obtained before with other nutritional strategies., [ES] Existe aún bastante controversia acerca de la capacidad de los taninos para modular el proceso de biohidrogenación ruminal (BH) de los ácidos grasos (AG) y mejorar el perfil lipídico de la leche o la carne sin afectar negativamente a la utilización digestiva de la dieta. A partir de esta base, este trabajo se llevó a cabo con el objetivo de investigar el efecto de la presencia de taninos en la dieta (en concreto, en el heno de esparceta, Onobrychis viciifolia) sobre la BH de los ácidos linoleico (18:2n-6) y linolénico (18:3n-3) y el proceso de fermentación ruminal. El estudio se realizó in vitro, mediante cultivos discontinuos de microorganismos ruminales y la técnica de producción de gas. Como donantes del inóculo microbiano se utilizaron ovejas canuladas en el rumen. Los sustratos incubados fueron dos henos de leguminosas: uno de alfalfa (prácticamente libre de taninos) y otro de esparceta (similar al anterior en cuanto a su composición química pero con un 3,5% de taninos totales en equivalentes de ácido tánico). Ambos henos se enriquecieron con aceite de girasol (como fuente de ácido linoleico) o aceite de lino (como fuente de ácido linolénico). La parte analítica incluyó determinaciones de taninos, del perfil lipídico del contenido ruminal (centrado fundamentalmente en metabolitos de interés como 18:0, trans-11, trans-10 y cis-9 18:1, cis-9 trans-11 18:2 -principal isómero del ácido linoleico conjugado; CLA-, trans-11 cis-15 18:2, 18:2n-6 y 18:3n-3) y de algunos parámetros indicativos de la fermentación en el rumen (e. g., producción de gas, concentración de amoniaco, desaparición de materia seca, etc.). La mayor parte de los resultados relativos a los metabolitos intermedios de la BH (e. g., mayores concentraciones de 18:3n-3, 18:2n-6, trans-11 cis-15 18:2, cis-9 18:1 o AG poliinsaturados totales en las incubaciones de esparceta) muestran la capacidad de esta leguminosa, posiblemente atribuible a su contenido de taninos, para inhibir la BH ruminal de los AG insaturados de la dieta. Por otra parte, no se detectaron diferencias significativas (P>0,10) en la acumulación de cis-9 trans-11 CLA, CLA total o 18:0, y la variación en el trans-11 18:1 no siguió un patrón regular. En cuanto a la fermentación ruminal, se observó que la producción de gas era inferior en las incubaciones del heno de esparceta (-17%), lo cual coincide con lo señalado previamente por muchos autores cuando se utilizan taninos. De acuerdo con esto, las concentraciones de amoniaco también mostraron un valor más bajo en la esparceta (-23%), al igual que la producción de ácidos grasos volátiles totales (-11%), siendo las proporciones molares de butírico y valérico las que mejor reflejaron esta diferencia. En conjunto, el estudio muestra la capacidad de Onobrychis viciifolia, seguramente gracias a su contenido moderado de taninos, para modificar la BH ruminal de los AG insaturados de la dieta, lo cual podría redundar en una mejora del perfil lipídico de los productos finales (carne y leche). Sin embargo, los resultados observados no son tan prometedores como cabría esperar a priori o como se han conseguido con otras estrategias nutricionales.