Species extinctions strengthen the relationship between biodiversity and resource use efficiency

Evidence from terrestrial ecosystems indicates that biodiversity relates to ecosystem functions (BEF), but this relationship varies in its strength, in part, as a function of habitat connectivity and fragmentation. In primary producers, common proxies of ecosystem function include productivity and resource use efficiency. In aquatic primary producers, macroecological studies have observed BEF variance, where ecosystems with lower richness show stronger BEF relationships. However, aquatic ecosystems are less affected by habitat fragmentation than terrestrial systems and the mechanism underlying this BEF variance has been largely overlooked. Here, we provide a mechanistic explanation of BEF variance using a trait-based, numerical model parameterized for phytoplankton. Resource supply in our model fluctuates recurrently, similar to many coastal systems. Our findings show that following an extinction event, the BEF relationship can be driven by the species that are the most efficient resource users. Specifically, in species-rich assemblages, increased redundancy of efficient resource users minimizes the risk of losing function following an extinction event. On the other hand, in species-poor assemblages, low redundancy of efficient resource users increases the risk of losing ecosystem function following extinctions. Furthermore, we corroborate our findings with what has been observed from large-scale field studies on phytoplankton

Transcriptomic analysis of the developing and adult mouse cochlear sensory epithelia

International audienceThe adult mammalian cochlea lacks regenerative ability and the irreversible degeneration of cochlear sensory hair cells leads to permanent hearing loss. Previous data show that early postnatal cochlea harbors stem/progenitor-like cells and shows a limited regenerative/repair capacity. These properties are progressively lost later during the postnatal development. Little is known about the genes and pathways that are potentially involved in this difference of the regenerative/repair potentialities between early postnatal and adult mammalian cochlear sensory epithelia (CSE). The goal of our study is to investigate the transcriptomic profiles of these two stages. We used Mouse Genome 430 2.0 microarray to perform an extensive analysis of the genes expressed in mouse postnatal day-3 (P3) and adult CSE. Statistical analysis of microarray data was performed using SAM (Significance Analysis of Microarrays) software. We identified 5644 statistically significant differentially expressed transcripts with a fold change (FC) >2 and a False Discovery Rate (FDR) ≤0.05. The P3 CSE signature included 3,102 transcripts, among which were known genes in the cochlea, but also new transcripts such as, Hmga2 (high mobility group AT-hook 2) and Nrarp (Notch-regulated ankyrin repeat protein). The adult CSE overexpressed 2,542 transcripts including new transcripts, such as Prl (Prolactin) and Ar (Androgen receptor), that previously were not known to be expressed in the adult cochlea. Our comparative study revealed important genes and pathways differentially expressed between the developing and adult CSE. The identification of new candidate genes would be useful as potential markers of the maintenance or the loss of stem cells and regenerative/repair ability during mammalian cochlear development

Efecto de la incorporación de aceites esenciales de romero sobre la producción de leche de cabra y el crecimiento de los cabritos

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Effects of distillated myrtle (Myrtus communis L.) leaves’ intake on cull ewes’ body weight gain, carcass composition and meat quality

Aim of study: Cull ewes are characterized by poor body condition, low body weights and tough meat texture. This work aimed to investigate the effect of distillated myrtle leaves (MDL) intake on body weight (BW) gain; carcass characteristics and meat quality of Barbarine cull ewes.Area of study: Northwest of TunisiaMaterial and methods: 27 Barbarine ewes were assigned into 3 groups receiving 500 g of oat hay and 750 g of concentrate control group (C), while they were given concentrate and pellets, containing 87% MDL, as substitute to hay in MHay group; for MConc group, they were fed hay, concentrate and pellets containing 30% MDL in partial substitution to concentrate. At the end of the fattening period (90 days), ewes were slaughtered.Main results: The dry matter intake was higher (p<0.05) for MConc and C groups. The average daily gain was significantly higher for C and MConc than MHay groups (113 and 107 vs. 87 g, respectively). Ewes fed MHay and MConc had a significantly lower feed conversion rate than Control group (12.5 vs. 15.4). Dietary treatment had no significant effect on carcass joint’s weight and proportions. The dressing percentage and carcass tissue composition were similar for all groups. The ultimate pH, water cooking loss and color parameters values were unaffected by the type of diet.Research highlights: These findings revealed that MDL could substitute, in ewes feeding, up to 87% to hay or up to 30% to concentrate without negative effects on body weight, carcass characteristics and meat quality

Effects of using rosemary residues as a cereal substitute in concentrate on vitamin e, antioxidant activity, color, lipid oxidation, and fatty acid profile of barbarine lamb meat

The shortage of some ingredients and, consequently, the continuous increase in the price of feed encourage the search for other alternatives to maintain animal production and enhance its products. In this line, the use of aromatic plant by-products in animal diet has been recently and widely considered, given their richness in bioactive compounds. Therefore, the aim of this study was to investigate the effects of the inclusion of rosemary residues (RR) and protein sources on lamb meat quality. The experiment was carried out on 24 male Barbarine lambs (3 months old) with an average body weight (BW) of 17.8 ± 2.6 kg, which were divided into three homogeneous groups according to BW. The diet comprised 600 g of oat hay and 600 g of concentrate. Three types of concentrate were evaluated: commercial concentrate as the control group (C); rosemary residues (RR) plus soybean meal as the RRS group, and RR plus faba bean as the RRF group. After an experimental period of 65 days, lambs were slaughtered. The inclusion of RR in both concentrates increased the a-tocopherol and total polyphenol content in meat and protected meat against discoloration (high red index and chroma after 9 days of storage) but did not affect meat lipid oxidation, which was similar for all groups. The FA profile was affected by the inclusion of RR, with no effect from the source of protein (faba bean or soybean). The inclusion of RR in the concentrate increased the C18:2 n-6, C18:3n-3, C20:4 n-6, C20:5 n-3, and C22:5 n-3 content (p < 0.05). Consequently, the inclusion of RR also increased the total polyunsaturated FA (p < 0.05) and the ratio of polyunsaturated FA to saturated FA (p < 0.05). The results of this study demonstrate that concentrate based on RR could be useful for lamb meat production by improving the nutritional quality of meat, especially the fatty acid profile. In addition, soybean meal can be replaced by faba bean in lamb concentrate without affecting meat quality. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Rumen fermentation pattern and blood metabolites of lambs from three breeds reared on pasture or feedlot

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Efecto de la inclusión de aceite de murta en la dieta de cabritos sobre la calidad sensorial de la carne

Los autores agradecen a Zina Taghouti, técnica en el laboratorio de Producción Animal del INRAT por la asistencia técnicaPublishe