A review of strategies aimed at adapting livestock to volatile climatic conditions in Nigeria

Despite their crucial importance, limited information exists about how livestock are affected by climate change in Nigeria. Changing climatic patterns are manifested through occurrences like abrupt temperature increase, dwindling rainfall pattern, rise in spells of drought and flood. These conditions exert different effects across the geographical landscape of the country, which can broadly be classed as Semiarid, Sahel and Derived Savannah, respectively as well as Forest and Montane. Livestock provide humans with the full complement of amino acids, which are the only known natural suppliers of Vitamin B12 and equally supply iron, calcium, iodine and zinc. In addition, livestock accounts for 40% of Agricultural Gross Domestic Product and significantly contributes to enhancing rural livelihood. Stress conditions are induced in livestock by harsh weather conditions that reduce the feed available to them as well as impede growth rate and reproduction efficiency and disease incidence which may eventually result in death. In the light of the livestock benefits to humanity, it is necessary to devise means of making their climate resilient. Some of the proven strategies include animal genetic improvement for stress tolerance, growing disease resistant, early maturing and drought tolerant crops, selecting for and rearing climate tolerant animal species and breeds. Malgré leur importance cruciale, il existe peu d'informations sur la manière dont le bétail est affecté par le changement climatique au Nigéria. Le changement des modèles climatiques se manifeste par des événements tels que l'augmentation brutale de la température, la diminution des précipitations, l'augmentation des périodes de sécheresse et d'inondation. Ces conditions exercent des effets différents sur le paysage géographique du pays, qui peuvent être globalement classés comme semi-aride, sahélien et savane dérivée, respectivement, ainsi que forêt et montagne. Le bétail fournit aux humains le complément complet d'acides aminés, qui sont les seuls fournisseurs naturels connus de vitamine B12 et fournissent également du fer, du calcium, de l'iode et du zinc. En outre, l'élevage représente 40% du produit intérieur brut agricole et contribue de manière significative à l'amélioration des moyens d'existence ruraux. Les conditions de stress sont induites chez le bétail par des conditions météorologiques difficiles qui réduisent les aliments disponibles pour eux et entravent le taux de croissance, l'efficacité de la reproduction et l'incidence des maladies qui peuvent éventuellement entraîner la mort. À la lumière des avantages de l'élevage pour l'humanité, il est nécessaire de concevoir des moyens de rendre leur résilient climatique. Certaines des stratégies éprouvées comprennent l'amélioration génétique animale pour la tolérance au stress, la culture de cultures résistantes aux maladies, à maturation précoce et à la sécheresse, la sélection et l'élevage d'espèces et de races animales tolérantes au climat.

Potential seed dispersal by Didelphis albiventris (Marsupialia, Didelphidae) in highly disturbed environment

Urban forests are usually isolated and highly disturbed, however they are important shelters for tolerant animal species. Their food habits expose the different ecological roles these animals perform in the habitat. We analyzed the contribution of Didelphis albiventris Lund (1840), as a seed disperser, to the vegetation renewal of an urban forest fragment, describing its frugivorous diet and testing the viability of ingested seeds. Both male and female of white-eared opossum included a vast variety of items in their diet, mainly invertebrates and fruits. Fruits were consumed during all year round and seasonality was not observed. The majority of consumed fruits was from pioneer plant species, which is common in disturbed areas, in accordance to the opossum's opportunistic habits. The viability of ingested seeds, evaluated by linear logistic regression models applied to data from germination tests, was different of the seeds collected directly from ripe fruits; it varied among species, maybe due to the intrinsic characteristics of plant species. As a highly generalist species, D. albiventris can inhabit disturbed environments and then disperse seeds from pioneer plants, where the vegetation must be restored. It is crucial that this process does not depend only on the specialist frugivores, which are frequently absent in urban forest fragments. Therefore, the presence of generalist species of secondary environments has its importance emphasized.

THE THYMUS AND RECOVERY OF THE SHEEP ERYTHROCYTE RESPONSE IN IRRADIATED MICE

The role of the thymus in the recovery of the sheep erythrocyte response after lethal irradiation has been studied in adult CBA mice with the hemolytic plaque technique of Jerne. This immunological parameter is markedly thymus-dependent. 10 wk after irradiation and after antigenic challenge the thymectomized animal has only one-twentieth to one-fortieth the number of plaque-forming cells as does the irradiated animal with intact thymus. The thymus continues to function into the 7th and 8th month of life in this strain. Unlike the drug-tolerant animal, the incompetent irradiated thymectomized mouse retains base line plaques (plaques without antigenic stimulation). Thymectomy 18 days after irradiation is as effective as prior thymectomy in preventing recovery of the sheep cell response. Thymectomized animals receiving grafts of isogenic neonatal thymus (placed beneath the kidney capsule) 1 day, 1 wk, or 2 wk after irradiation are somewhat more responsive at 10 wk than intact animals. Grafts in place for 1 or 2 wk after irradiation and then removed result in one-fifth the recovery of grafts in place the entire time, while only slight restoration is obtained from grafts in place for the final 3 wk of the experiment. The results indicate that the thymus is not required for the 18 days after irradiation, that a period of at least 3 wk residence is required for complete restoration, and that the thymus itself is somewhat radiation-sensitive. Allogeneic thymus grafts failed to restore the hemolysin response of irradiated thymectomized animals.

PRODUCTION OF IMMUNOLOGICAL TOLERANCE IN MICE AFTER REPEATED INJECTIONS OF DISRUPTED SPLEEN CELLS

1. Tolerance of male skin isografts has been regularly produced in female mice of the C57B1 strain sublines 1, 4, and 6 during adult life by repeated injection of completely disrupted spleen cells derived from male donors. The tolerant state is long-lasting since such grafts have remained in place more than 9 months. 2. Prolonged survival of homotransplants of skin has regularly been produced in DBA/2 mice during adult life by repeated injections of completely disrupted spleen cells from Balb/C donors. When injections of disrupted spleen cell material are continued over a sufficiently long period, permanent acceptance of the skin homografts may be obtained between these strains. 3. Immunological tolerance across even the strong H-2 histocompatibility barrier was obtained in the neonatal period and during adult life by repeated injection of disrupted spleen cell preparations. The tolerant state has been revealed by both mammary adenocarcinoma and skin homografting across this strong histocompatibility barrier. 4. In contradistinction to the tolerant state produced by injection of intact spleen cells in neonatal animals or during adult life or that produced by parabiotic union, the tolerance produced by repeated injection of disrupted spleen cell preparations cannot be transferred to syngenic neonatal mice with spleen cells of the tolerant animal. 5. The implications of these findings in transplantation biology and in consideration of the basic nature of tolerance are discussed.

MECHANISMS OF ENDOTOXIN TOLERANCE

Pyrogenic tolerance following 7 daily intravenous injections of 2.0 µg/kg E. coli endotoxin in albino rabbits was associated with significant increases in RES phagocytic activity as measured with colloidal carbon. Nevertheless, 4 hours after RES blockade with thorotrast (3 ml/kg), the tolerant rabbits exhibited significantly lower fever indices following intravenous endotoxin challenge than did non-tolerant control animals despite comparably depressed capacities to clear carbon from the blood. Moreover, plasma from rabbits tolerant to endotoxin induced significant tolerance in normal rabbits prepared by thorotrast blockade without enhancing the depressed carbon clearance. This passive protection extended to heterologous endotoxins. Analysis of the data indicates that RES blockade does not abolish tolerance; rather blockade resets the reactivity to endotoxin in the normal and tolerant animal, rendering both exquisitely reactive, but permitting retention of the major portion of tolerance. Apparently the tolerant animal possesses a dual endotoxin defense system. One system is abolished by thorotrast; the other is in part humoral, accounts for the greater portion of tolerance, and is thorotrast-resistant. The nature of the humoral component is not defined but is consistent with that of an opsonin with high endotoxin specificity.