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[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.

El proyecto “Calendario Científico Escolar” ha consistido en la elaboración de un calendario dirigido al alumnado de educación primaria y secundaria obligatoria. Cada día se ha recogido un aniversario científico o tecnológico como, por ejemplo, nacimientos de personas de estos ámbitos o conmemoraciones de hallazgos destacables. Además, el calendario se acompaña de una guía didáctica con orientaciones para el aprovechamiento educativo transversal del calendario en las clases, incluyendo actividades adaptadas a cada rango de edad.

El proyecto “Calendario Científico Escolar” ha consistido en la elaboración de un calendario dirigido al alumnado de educación primaria y secundaria obligatoria. Cada día se ha recogido un aniversario científico o tecnológico como, por ejemplo, nacimientos de personas de estos ámbitos o conmemoraciones de hallazgos destacables. Además, el calendario se acompaña de una guía didáctica con orientaciones para el aprovechamiento educativo transversal del calendario en las clases, incluyendo actividades adaptadas a cada rango de edad.

El proyecto “Calendario Científico Escolar” ha consistido en la elaboración de un calendario dirigido al alumnado de educación primaria y secundaria obligatoria. Cada día se ha recogido un aniversario científico o tecnológico como, por ejemplo, nacimientos de personas de estos ámbitos o conmemoraciones de hallazgos destacables. Además, el calendario se acompaña de una guía didáctica con orientaciones para el aprovechamiento educativo transversal del calendario en las clases, incluyendo actividades adaptadas a cada rango de edad.

[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.

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.

[EN] Most 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. Protein evaluation would be among the first needs in this regard. However, concerns exist about the use of methodologies such as the in situ nylon bag technique or batch cultures of ruminal microorganisms, and other possibilities must be explored. 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 master thesis was therefore performed with two main 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. In the first experiment, 4 insect meals were studied: 1) mealworm (Tenebrio molitor); 2) morioworm (Zophobas morio); 3) buffaloworm (Alphitobius diaperinus), and 4) domestic cricket (Acheta domesticus, adults). In addition, soybean meal was used as a reference feed. The protein evaluation of these meals was conducted using 3 different techniques. First, in vitro batch cultures of ruminal microorganisms were carried out with increasing levels of starch, and N degradation was estimated by linear regression (mL of gas vs. mg of ammonia-N). The second methodology consisted in estimating N disappearance by filtering the in vitro incubation residue, whereas the third approach involved the in situ nylon bag technique. In the second experiment, the effect of treating the 4 insect meals with 15% dry matter of commercial extracts of oak or quebracho tannins was evaluated and compared agai, [ES] En la mayor parte de los sistemas intensivos de alimentación de rumiantes existe una gran dependencia de la torta de soja como fuente de proteína, lo que hace necesaria la búsqueda de alternativas. El empleo de insectos se ha sugerido como una de dichas alternativas, pero, hasta la fecha, existen muy pocos trabajos científicos que los caractericen. Una de las primeras necesidades al respecto es su valoración proteica. Sin embargo, el uso las técnicas in situ de las bolsas de nailon o in vitro de cultivos no renovados de microorganismos ruminales han sido cuestionadas, por lo que sería preciso explorar otras posibilidades. 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, esta tesis de máster se llevó a cabo con dos objetivos principales: 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 harinas de insectos sin afectar a su digestibilidad intestinal. Para cumplirlos, se realizaron 2 ensayos. En el primero, se valoraron 4 harinas de insectos: 1) gusano de la harina (Tenebrio molitor); 2) gusano rey (Zophobas morio); 3) escarabajo de la cama (Alphitobius diaperinus), y 4) grillo doméstico (Acheta domesticus, adultos). Además, se utilizó torta de soja como alimento de referencia. Para la valoración proteica de estos alimentos se usaron 3 técnicas diferentes. En el primero, se siguió la metodología in vitro de cultivos no renovados de microorganismos ruminales con dosis crecientes de almidón y la degradación del N se estimó mediante regresión lineal (mL de gas vs. mg de N-amoniacal). El segundo consistió en la estimación de la degradación de N mediante el filtrado clásico tras la incubación in vitro y en el tercero se empleó la técnica in sit, [FR] Dans la plupart des systèmes intensifs, l'alimentation des ruminants est fortement dépendante de l’utilisation du tourteau de soja comme source de protéines, ce qui rend nécessaire la recherche d’aliments protéinés alternatifs. L'utilisation de la farine d'insectes a été suggérée comme l'une de ces alternatives, mais à ce jour, très peu de travaux scientifiques ont caractérisé ces aliments. L’évaluation de la valeur des protéines serait l’un des premiers besoins à cet égard. Toutefois, l'emploi des techniques des sacs en nylon in situ ou des cultures discontinues de microorganismes ruminaux in vitro est remise en question. Par ailleurs, l'ampleur de la dégradation ruminale des farines d’insectes est inconnue. C’est pourquoi, l'utilisation de tanins a été envisagée dans ces travaux afin de la limiter, et ainsi, améliorer l’utilisation digestive. Par conséquent, deux principaux objectifs composent cette thèse de maîtrise: 1) évaluer la digestibilité de la protéine de certaines farines d’insectes à l’aide de differentes techniques (in vitro et in situ), et 2) évaluer l’efficacité des tanins à réduire la dégradation ruminale de la protéine sans affecter sa digestibilité intestinale. Pour ce faire, deux essais ont été réalisés. Dans le premier, la digestibilité de la protéine de quatre farines d'insectes a été étudiée en comparaison avec le tourteau de soya (aliment de référence), soit celle du 1) ver de farine (Tenebrio molitor), 2) ver morio (Zophobas morio) 3) ver buffalo (Alphitobius diaperinus) et 4) grillons domestiques (Acheta domesticus, adultes). Trois techniques d’analyses ont été utilisées. La première utilisait des cultures discontinues de microorganismes ruminaux in vitro en combinaison avec des doses croissantes d’amidon. Le N dégradé a par la suite été estimée à l’aide d’une régression linéaire (mL de gas vs. mg de N-amoniacal). La seconde consistait à estimer la disparition du N au moyen de la filtration classique suite à une incubation in vitro. Enf

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<0.10) were observed in the quadratic regression using all data and the evenness index with HhaI (R2=0.15) and in the linear regression using data from one experiment and the Shannon index with MspI (R2=0.15). Furthermore, a significant quadratic relationship (P<0.01) was found for data from one experiment and richness with MspI (R2=0.43). In the linear regression, RFI decreased (efficiency increased) as diversity augmented. In the two quadratic correlations, however, the most efficient animals were those with the greatest and least diverse bacterial communities, which might be associated with apparent inconsistencies in the literature. In this regard, one hypothesis postulates that a greater microbial diversity might also imply a larger diversity in micro

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.

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

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).

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; P<0.05), which was unexpected, particularly in the non-MFD conditions. Nevertheless, this relationship was equivalent in the two experime

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

Milk fat depression (MFD) is characterized by a reduction in the content of milk fat, presumably caused by the anti-lipogenic effects of rumen biohydrogenation intermediates, such as trans-10 cis-12 conjugated linoleic acid (CLA). In this study, RNA-Seq technology was used to help elucidate the mammary responses involved in CLA-induced MFD in lactating ewes. To this end, we compared the milk somatic cell transcriptome of ewes suffering from CLA-induced MFD with control ewes (i.e., those without MFD), as well as with ewes fed a diet supplemented with fish oil (FO-MFD) that we previously reported affects the mammary transcriptome. In the differential expression analysis between CLA-MFD and controls, we identified 1,524 differentially expressed genes (DEGs), whereas 653 were detected between CLA- and FO-MFD groups. Although this article focuses on lipid metabolism, CLA affected the expression of many genes related to other biological processes, especially immunity. Among the 55 genes shared by both MFD conditions, some genes linked to fatty acid synthesis, such as ACACA, AACS, ACSS2, or ACSS3, were downregulated. In addition, this study provides a list of candidate genes that are not usually considered in the nutrigenomics of MFD but that may act as key regulators of this syndrome in dairy ewes.

El proyecto “Calendario Científico Escolar” ha consistido en la elaboración de un calendario dirigido al alumnado de educación primaria y secundaria obligatoria. Cada día se ha recogido un aniversario científico o tecnológico como, por ejemplo, nacimientos de personas de estos ámbitos o conmemoraciones de hallazgos destacables. Además, el calendario se acompaña de una guía didáctica con orientaciones para el aprovechamiento educativo transversal del calendario en las clases, incluyendo actividades adaptadas a cada rango de edad.

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 performa

La suplementación de la dieta de las ovejas con lípidos de origen marino permite mejorar el carácter saludable de la grasa de la leche. Sin embargo, produce el síndrome de baja grasa en la leche, lo que impide su implementación en condiciones prácticas.

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.

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.

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.

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 supplem