The role of pastoralism in regulating ecosystem services.

Pastoralism is rarely viewed as a major future form of land use, because of well-documented cases of rangeland degradation, attributed to irrational overstocking by pastoralists, and the subsequent losses of ecosystem services. However, pastoralists were actually encouraged to settle and adopt such strategies, copied from rangelands with higher and more reliable rainfall. This curtailed mobility resulted in a shift from opportunistic and extensive land use to more intensive and settled forms of use. The purpose of this review is to examine the link between pastoralism and the provision of ecosystem services by rangelands, focusing on biodiversity conservation and carbon sequestration. Pastoralists employ several techniques to manage rangeland resources, including mobility, herding, corralling, grazing reserves and the use of fire. With these strategies, pastoralists have contributed to the enhancement of rangeland biodiversity and the long-term conservation of important wildlife habitats. Pastoralists also possess detailed knowledge of rangeland plants and their uses, which could be valuable in the assessment, conservation and utilisation of rangeland biodiversity. Similarly, traditional pastoral rangeland management practices, such as the use of seasonal grassland reserves and livestock mobility, influence vegetation composition, coverage and abundance in rangelands and offer tools for biomass and soil carbon restoration, contributing to the mitigation of climate change. However, various internal and external factors have curtailed traditional management practices and livestock mobility, breaking the co-evolved balance of vegetation, wildlife and land use, thus exposing rangeland to continued livestock pressure, which often leads to degradation. Rather than abandoning pastoralism, the revitalisation of traditional practices and indigenous knowledge is vital to secure sustainable livelihoods for millions of pastoralists and to maintain rangeland biodiversity and ecosystem services.

Parmi les modalités d'utilisation des terres, le pastoralisme n'est guère considéré comme présentant un fort potentiel d'avenir, en raison d'exemples bien documentés de prairies dégradées suite à leur surexploitation irrationnelle par les pasteurs, entraînant une baisse des services écosystémiques qui leur étaient associés. Il faut toutefois rappeler que ces mêmes pasteurs avaient d'abord été encouragés à se sédentariser et à adopter ce type de stratégies, directement inspirées des pratiques d'élevage appliquées dans les prairies bénéficiant de précipitations plus importantes et plus fiables. Le déclin de la mobilité s'est traduit par le passage d'une utilisation opportuniste et extensive des terres à des formes d'exploitation plus intensives et sédentarisées. Les auteurs se sont attachés à faire apparaître les liens entre le pastoralisme et les services écosystémiques rendus par les prairies, en premier lieu la protection de la biodiversité et la séquestration de carbone. Les pasteurs recourent à diverses techniques pour gérer les ressources des prairies, dont la transhumance, la conduite des troupeaux, l'érection de clôtures, la rotation des pâtures et l'usage du feu. En déployant ces stratégies, les pasteurs ont contribué à améliorer la biodiversité des prairies et à assurer la conservation durable d'habitats importants pour la faune sauvage. Les pasteurs possèdent également une connaissance détaillée des espèces végétales poussant dans les prairies et de leur utilisation, qui s'avère précieuse pour évaluer, conserver et utiliser la biodiversité des prairies. De même, les pratiques pastorales traditionnelles de gestion des prairies telles que la rotation saisonnière des parcelles et les déplacements des troupeaux influent sur la répartition, la couverture et l'abondance de la végétation des prairies et constituent des outils permettant de réparer la biomasse et de séquestrer le carbone des sols, contribuant ainsi à atténuer le réchauffement climatique. Néanmoins, plusieurs facteurs internes et externes ont limité les pratiques de gestion traditionnelles et la mobilité des troupeaux, brisant l'équilibre d'une coévolution parallèle de la végétation, la faune sauvage et l'exploitation des terres, et exposant de ce fait les prairies à une pression permanente, souvent suivie de leur dégradation. Plutôt que de renoncer au pastoralisme, il est désormais crucial de revitaliser les pratiques traditionnelles et les savoirs autochtones afin de sécuriser les moyens de subsistance de millions de pasteurs et de préserver la biodiversité des prairies et les services écosystémiques.

Al pensar en las principales modalidades de usos del suelo de cara al futuro, rara vez se tiene en cuenta el pastoreo. Ello se debe a la existencia de casos probados de degradación de los pastos, atribuida a un acopio excesivo e irracional por parte de los pastores, y a la consiguiente pérdida de servicios ecosistémicos. La realidad, sin embargo, es que las comunidades de pastores fueron alentadas a asentarse y adoptar tales procederes, importados de zonas de pastizales con niveles más elevados y constantes de pluviosidad. La consiguiente limitación de la movilidad llevó a pasar de un uso oportunista y extensivo de las tierras a modalidades de explotación más intensivas y sedentarias. Los autores examinan aquí el vínculo entre el pastoreo y los servicios ecosistémicos ligados a los pastizales, centrándose sobre todo en la conservación de la diversidad biológica y el secuestro de carbono. Las sociedades de pastores emplean varias técnicas para gestionar los recursos que suponen las tierras de pasto, en particular la movilidad, el uso de rebaños, corrales y reservas de pastizales y el recurso al fuego. Con estas estrategias los pastores han contribuido a mejorar la diversidad biológica de los pastizales y a conservar duraderamente importantes hábitats de la fauna salvaje. Estas sociedades atesoran asimismo un detallado conocimiento de las plantas que forman los pastizales y de sus usos, lo que puede revestir gran utilidad para evaluar, preservar y utilizar la biodiversidad de los pastizales. Análogamente, las prácticas tradicionales de gestión de pastos que aplican los pastores (como el uso de reservas estacionales de tierras de pasto o la movilidad del ganado) influyen en la composición vegetal, la cobertura y la abundancia de los pastizales y brindan así herramientas para restaurar la biomasa y el carbono del suelo, ayudando con ello a mitigar el cambio climático. Sin embargo, hay una serie de factores internos y externos que han coartado las prácticas de gestión tradicionales y la movilidad del ganado, alterando el equilibrio entre vegetación, fauna salvaje y usos del suelo que se había alcanzado por coevolución y sometiendo así a los pastizales a una presión ganadera continua, que a menudo acaba por degradarlos. Más que de abandonar el pastoreo, se trata pues de revitalizar las prácticas tradicionales y el saber indígena como expediente crucial para procurar medios de sustento duraderos a los millones de personas que viven del pastoreo y a la vez mantener la diversidad biológica y los servicios ecosistémicos de los pastizales.

Identification and characterization of functional genes encoding the mouse major urinary proteins.

Mouse Ltk- cells were stably transfected with cloned genes encoding the mouse major urinary proteins (MUPs). C57BL/6J MUP genomic clones encoding MUP 2 (BL6-25 and BL6-51), MUP 3 (BL6-11 and BL6-3), and MUP 4 (BL6-42) have been identified. In C57BL/6J mice, MUP 2 and MUP 4 are known to be synthesized in male, but not female, liver, and MUP 3 is known to be synthesized in both male and female liver and mammary gland. A BALB/c genomic clone (BJ-31) was shown to encode a MUP that is slightly more basic than MUP 2 and was previously shown to be synthesized in both male and female liver of BALB/c but not C57BL/6 mice. Comigration on two-dimensional polyacrylamide gels of the MUPs encoded by the transfecting gene provides a basis for tentative identification of the tissue specificity and mode of regulation of each gene. DNA sequence analysis of the 5' flanking region indicates that the different MUP genes are highly homologous (0.20 to 2.40% divergence) within the 879 base pairs analyzed. The most prominent differences in sequence occur within an A-rich region just 5' of the TATA box. This region (from -47 to -93) contains primarily A or C(A)N nucleotides and varies from 15 to 46 nucleotides in length in the different clones.

Diurnal variation in the inducibility of luteal 20 alpha-hydroxysteroid dehydrogenase in pregnant rats.

Luteolysis was induced in rats during late pregnancy by fetoplacental removal, and was monitored by the increased activity of luteal 20 alpha-hydroxysteroid dehydrogenase (20 alpha-OHSDH). The extent of enzyme induction over a given length of time varied according to the time of day at which the fetuses and placentae were removed, 11.00 and 21.00 h appearing to give optimal and minimal enzyme activities respectively. The 20 alpha-OHSDH was more readily induced on day 19 than on day 18.

The lactose and neuraminlactose content of rat milk and mammary tissue.

Specific analyses of rat milk sugar revealed lactose and N-acetylneuraminyl-lactose. The latter showed multiple, interconvertible forms in certain paper-chromatographic systems. Mean lactose concentrations rose from 33.1mumol/ml at day 0 to 100mumol/ml at day 20 of lactation. Mean N-acetylneuraminyl-lactose concentrations rose from 7.1mumol/ml at day 0 to 25.9mumol/ml at day 4 and thereafter declined, decreasing to zero by day 20 of lactation. Similar data are given on the concentrations of these sugars in mammary tissue of rats. Neuraminyl-lactose was also detected in mouse mammary tissue.

Lactogenesis in the rat. Metabolism of uridine diphosphate galactose by mammary gland.

1. Lactose synthetase activity in the rat mammary gland increases during the last day of pregnancy from an essentially zero value. There is a parallel increase of tissue lactose and of glucose 6-phosphate dehydrogenase activity. 2. Mammary-gland homogenates prepared both before and after parturition hydrolyse the lactose precursors glucose 6-phosphate, glucose 1-phosphate, UDP-glucose, UDP-galactose and also maltose, but not lactose. 3. A role of lactose synthetase as the rate-limiting enzyme for lactose biosynthesis and the possible significance of the hydrolytic activities are discussed with respect to lactogenesis.

Esterification of glycerol 3-phosphate in lactating guinea-pig mammary gland.

1. The presence of palmitoyl-CoA-l-glycerol 3-phosphate palmitoyltransferase (EC 2.3.1.15) has been demonstrated in a particulate fraction of mammary tissue from lactating guinea pigs. 2. Cell-free preparations also catalysed the activation of palmitate and oleate, and the conversion of enzymically formed phosphatidic acid into glycerides, in accord with the Kennedy pathway of glyceride formation. 3. The properties of the system that esterifies l-glycerol 3-phosphate were studied with respect to substrates and cofactors, and the reaction product was shown to be phosphatidic acid (1,2-diacyl glycerol 3-phosphate). 4. The extent to which newly formed phosphatidic acid was converted into glyceride in a cell-free system was dependent on the nature of the acyl donor, the concentration of subcellular particles, the time of incubation and the concentration of Mg(2+).

Regulation of triglyceride synthesis in the parturient guinea-pig mammary gland.

1. The specific activity of the enzyme palmitoyl-CoA-l-glycerol 3-phosphate palmitoyltransferase (EC 2.3.1.15) in the mammary tissue of guinea pigs has been shown to increase 37-fold at parturition. 2. Increases also occur in tissue concentrations of glycerol 3-phosphate, CoA and free fatty acid, but not in that of acid-insoluble CoA. 3. The isolation and fatty acid composition of plasma triglyceride and of mammary-tissue free fatty acid, diglyceride and triglyceride are described. 4. The findings are discussed in relation to the regulation of milk fat synthesis.

Aerobic lactate production by mammary tissue.

Glucose uptake and L-lactate production were measured in cell, slice and intact tissue preparations of mammary glands from late-pregnant and lactating rats. The tissues showed extensive conversion of glucose into lactate in vitro, but not in vivo. Therefore aerobic lactate formation is not a normal feature of mammary tissue, but occurs in vitro as the result of some metabolic derangement.

Effects of phlorrhizin and thiol reagents on the galactosyltransferase activity of Golgi membrane vesicles of lactating rat mammary gland.

1. The ability of phlorrhizin to inhibit the galactosylation of glucose was re-examined with Golgi membrane vesicles purified from rat mammary gland, and extended to the galactosylation of several glucose analogues and N-acylglucosamines. 2. The inhibition is ascribed, contrary to previous conclusions, to a general annealing of leaky membranes comprising a minority of the vesicles. 3. Three thiol reagents were able to inhibit the galactosylation of N-acylglucosamines with less, or no, inhibition of galactosylation of glucose. This demonstrates the existence of a Golgi membrane carrier that distinguishes between glucose and N-acylglucosamines.

Arteriovenous glucose differences across the mammary gland of the fed, starved, and re-fed lactating rat.

Arteriovenous glucose difference across the mammary gland of the lactating rat was used as an 'instantaneous' monitor of mammary glucose uptake. Plasma [glucose] and arteriovenous glucose difference varied according to whether Halothane, diethyl ether or sodium pentobarbitone anaesthesia was used. In pentobarbitone-treated rats a 60% glucose extraction in the fed state decreased to 5% after 18 h starvation, and recovered to 40% and 59% after 15 min and 60 min re-feeding respectively. The increase and decrease in plasma [fatty acids] and the depletion and restoration of hepatic glycogen mostly followed similar time courses. Re-feeding was accompanied by a brief surge of plasma [insulin]. Starved lactating rats showed a markedly greater capacity than age-matched virgin rats in the oral and intraperitoneal glucose tolerance tests. Mammary glucose uptake in the starved rat was significantly restored by oral or intraperitoneal glucose or by insulin, but not by acetoacetate or by heparin-induced elevation of plasma [fatty acids]. The role of insulin and of possible changes in mammary sensitivity to insulin in the return of mammary glucose uptake on re-feeding is discussed.

Lactogenesis in the rat. Changes in metabolic parameters at parturition.

1. Tissue concentrations of nucleic acids, protein, fat, water, metabolites and lactose, and the activities of seven enzymes concerned in milk biosynthesis, were measured in the rat mammary gland at closely spaced times before, at and after parturition. 2. Changes are seen in the tissue concentrations of most substances, and several changes are initiated at least during the day preceding parturition. 3. Lactose, which is absent 1 day before parturition, is found in amounts of 12mumoles/g. fresh wt. of tissue at parturition. 4. From the tissue activities before parturition of three enzymes on the biosynthetic pathway of lactose, and, from the small changes observed in their activities at parturition itself, it is concluded that the factors responsible for the appearance of lactose at parturition remain to be demonstrated.

Incorporation into phospholipid vesicles of pore-like properties from Golgi membranes of lactating-rat mammary gland.

The ability of rat mammary-gland Golgi membranes to produce monosaccharide-specific pores in phospholipid vesicles was investigated. The apparent ability of Triton X-100 extracts of Golgi membranes to form such pores was re-evaluated, since we have now found that an apparent pore is produced by the detergent alone. We therefore incorporated intact Golgi membranes (1 mg of protein) into egg-yolk phospholipid vesicles by direct sonication in the absence of any detergent. These vesicles retained about 0.6% of the total sucrose, but demonstrated selective permeability towards glucose compared with sucrose, with 19.8% of the glucose being lost during gel filtration on Sepharose 4B. This phenomenon seemed to be enhanced by the presence of acidic phospholipids and lysophosphatidylcholine, but was inhibited by inclusion of cholesterol in the vesicles. The best mixture of phospholipids comprised 6.5 mg of egg-yolk phospholipid, 1 mg of phosphatidylserine and 0.05 mg of lysophosphatidylcholine, where 32.9% of the glucose was lost. By using this optimum phospholipid mixture the pores were shown to be permeable to both glucose and mannitol, whereas sucrose and lactose were retained by the vesicles. Chaps (3- [(3-cholamidopropyl)dimethylammonio] propane-1-sulphonate)-solubilized membranes produced similar permeability in vesicles produced by dialysis of a solution of the phospholipids mixed with the membrane extract. This technique resulted in a greater loss of glucose, 33% loss requiring about 0.25 mg of protein. The pore-forming ability of both intact Golgi membranes and Chaps extracts was sensitive to boiling and proteolysis, indicating that a membrane protein was likely to be involved in pore formation.

The roles of pregn-5-ene-3 beta, 20 alpha-diol and 20 alpha-hydroxy steroid dehydrogenase in the control of progesterone synthesis preceding parturition and lactogenesis in the rat.

1. The activity of 20alpha-hydroxy steroid dehydrogenase in rat ovarian corpora lutea increased at least 50-fold between 2 days before and 2 days after parturition, and then fell gradually during lactation. The activity of 3beta-hydroxy Delta(5)-steroid dehydrogenase decreased by 50% at parturition but remained constant at other times. 2. The 20alpha-hydroxypregn-4-en-3-one/progesterone concentration ratio in the ovary fell tenfold between 1 day before and 1 day after parturition, in contrast with the increase of the ratio for these steroids in plasma. 3. Pregnenolone was metabolized in intact cells or cell-free systems either to pregn-5-ene-3beta,20alpha-diol and then to 20alpha-hydroxypregn-4-en-3-one by 20alpha-hydroxy steroid dehydrogenase and 3beta-hydroxy Delta(5)-steroid dehydrogenase respectively, or directly to progesterone by the latter enzyme. The relative activities of these pathways appeared to reflect the relative amounts of the two enzymes and the concentrations of their respective coenzymes NADPH and NAD(+). 4. From these and other observations it was concluded that the cessation of progesterone secretion, which precedes parturition and lactogenesis at the end of pregnancy, is partly due to the redirected metabolism of pregnenolone away from progesterone and towards 20alpha-hydroxypregn-4-en-3-one as the secreted end product. This is primarily the consequence of the sharp increase in the activity of 20alpha-hydroxy steroid dehydrogenase. This mechanism is super-imposed on the already declining rate of net Delta(4)-steroid release by the ovary. 5. A relationship of these pathways to subcellular compartments of luteal cells is proposed.

The role of nucleoside diphosphatase in a uridine nucleotide cycle associated with lactose synthesis in rat mammary-gland Golgi apparatus.

1. UDP-galactose utilization by isolated Golgi vesicles or rat mammary gland synthesizing lactose causes accumulation of UMP but not UDP, although UDP is the immediate product of lactose synthase (EC 2.4.1.22). 2. This can be ascribed to a nucleoside diphosphatase (EC 3.6.1.6), specific for UDP, GDP and IDP, activated by bivalent metal ions and apparently located on the luminal face of the Golgi membrane. 3. The uridine diphosphatase activity exceeds the total galactosyltransferase activity 5-fold, and is estimated to maintain UDP at about 14 micrometer within the Golgi lumen. 4. Evidence is given that UMP, but not UDP, penetrates the membrane and that UMP is rephosphorylated to UDP by a UMP kinase located in the cytosol. 5. Golgi-cytosol relationships with respect to lactose synthesis are formulated in terms of a uridine nucleotide cycle which throws new light on the energy cost and possible regulation of lactose synthesis.