1,721,046 research outputs found
Relationship between oxidative status and pregnancy outcome in dairy cows
No full textIn ruminants, oxidative stress may be involved in several pathological conditions, including conditions that are relevant for ruminant reproduction, production and the general welfare (Miller et al 1993). Oxidative stress resulting from increased production of pro-oxidants, and/or a decrease in antioxidant defence, leads to damage of biological macromolecules and disruption of normal metabolism and physiology. Recent evidence has identified a potential role for oxidative stress as a trigger for cell death during luteolysis. Corpus luteum is essential for the maintenance of pregnancy and an excessive free radical generation damages luteal cell membrane and affects progesterone (P4) production (Kato et al 1997). This condition may lead to a failure in embryo development, increasing days open and calving intervals. It is possible that the metabolic stress induced by lactation makes the corpus luteum more susceptible to stress and free radicals may be involved in the decrease in fertility.
This study was designed to evaluate if the establishment of pregnancy may be affected by metabolic and oxidative status of dairy cows. We used 40 pasture fed Holstein-Friesian cows which were monitored daily for oestrous activity starting from day 50 postpartum. On the day of the artificial insemination (AI; Day 0), and on Days 30 and 42 after AI, blood samples were collected and reactive oxygen metabolites (ROMs) and biological antioxidant potential (BAP) concentrations were determined by a commercial kit (Diacron, Grosseto, Italy) on fresh blood by FRAS4 (H&D limited, Parma, Italy). Blood was centrifuged immediately and plasma was stored at -20 ̊C until assayed for its concentrations of P4, pregnancy associated glycoprotein (PAG), advanced oxidation protein products (AOPP), glucose, total proteins, urea, non-esterified fatty acid (NEFA), and glutathione (GSH). Plasma PAG concentrations at days 30 and 42 were used to perform a pregnancy diagnosis according to Zoli et al (1992). On the days of sampling, all cows were monitored for body condition score (BCS). The data gathered were analysed by logistic regression (GenStat); analysis included: between-subjects main effect of AI outcome (AI positive: AI+, AI negative: AI- and embryo mortality: EM), within-subjects main effect of postpartum period (Period 1: 120 days) and their interaction. Pearson’s correlation coefficients were calculated between the parameters measured in this study.
Overall, we observed 26 AI+ (33%), 49 AI- (62%), while EM was observed in 4 cases (5%). Cows that experienced EM had lower BCS values (2.5) compared to the AI+ (2.8) and AI- (2.9) cows (P<0.05). A reduction in BCS during early lactation doubles the rate of pregnancy losses and embryo mortality in dairy cows (Lopez-Gatius et al 2003). During the postpartum BCS increased and NEFA decreased (P<0.05) suggesting a recovery from the negative energy balance (NEB). The observation that on Day 0 plasma NEFA concentrations were higher in the AI+ (0.62 mmol/L; P<0.05) cows compared to the AI- (0.58 mmol/L) and EM (0.58 mmol/L) cows was unexpected as high serum concentrations of NEFA are known to have detrimental effects on fertility. Plasma glucose and ROMs concentrations increased during the postpartum (P<0.03 and P<0.01, respectively) with their highest values observed during Period 3. The gradual increase in glucose concentration suggests a recovery from the NEB. It is likely that the increase in ROMs concentration was due to the parallel increase in glucose, indeed the two were significantly correlated (r=0.2; P<0.05). Concentrations of BAP decreased during the postpartum (P<0.05) possibly as a consequence of parallel increase in ROMs levels; antioxidant depletion indeed, is considered the consequence and not the cause of oxidative stress. GSH and AOPP showed a similar trend: during Period 1 their concentrations were higher in EM than in AI+ and AI- (P<0.05). However, because of the low number of EM cases, this finding needs to be confirmed in further studies. It seems that plasma ROMs and BAP concentrations are not related to AI outcome. Considering that the maintenance of redox homeostasis is quite complex, further studies are required to clarify the role of oxidative status on cows’ fertility
Progesterone plus PMSG priming in seasonally anovulatory lactating Sarda ewes exposed to the ram effect
No full textThe aim of this trial was to evaluate the effectiveness (fertility and lambing) of priming with a single injection of progesterone plus PMSG in anovulatory lactating Sarda ewes subjected to the ram effect (RE) in spring. Thirty ewes (P4 group) were i.m. injected with 30 mg progesterone and 500 IU PMSG 36 h before ram introduction (d 0). This treatment was compared to a 12-day treatment with fluorogestone acetate intravaginal sponges that was followed by injections of 350 IU PMSG upon sponge withdrawal (FGA group, n = 30). All ewes responded to RE, showing plasma progestrone concentrations > 1 ng/mL between d 6 and 12 (FGA) or 6 and 9 (P4). Eighty-nine percent of the P4 ewes conceived at first ovulation, and 11% conceived following a short estrus cycle. Lambings occurred on d 150.4±3.9, and the lambing rate was 100%. The fertility of the FGA ewes was 83% for the induced ovulation and was 7% for the second ovulation after a normal cycle. The FGA ewes lambed on d 149.8±4.4, and the lambing rate was 83%. Two abortions were recorded for the FGA ewes, which had higher prolificacy than the P4 group (2.2 ± 0.8 vs. 1.8 ± 0.4, respectively; P<0.05). Both fertility and the lambing rate were high in both groups, with a high degree of estrus synchronization, and there were no significant differences between the groups. We concluded that priming of lactating Sarda ewes in spring with P4+PMSG before RE is an effective and competitive method (cheaper and more practical than FGA+PMSG) of inducing fertile ovulations in these ewes.
Key words: Estrus induction, Fertility, Progesterone priming, Prolificacy, Sheep
Concentraciòn hematica de progesterona durante la gestaciòn en alpacas criada en Italia
No full textBlood Progesterone concentration during pregnancy in Alpaca bred in Italy
Responses to intra-luteal administration of cloprostenol in dairy cows
No full textThe aim of the study was to determine the luteolytic dose of cloprostenol administered directly into the corpus luteum (CL; intra-luteal treatment, ILT) in dairy cattle. Cows of two control groups were treated with 500 μg of cloprostenol (Estrumate®) intramuscularly (IM-500) or via ILT with 0.2 mL of physiological solution (ILT-0). Cows of four experimental groups were treated by ILT with cloprostenol in doses 5, 25, 50 and 100 μg (ILT-5, -25, -50 and -100 groups). Progesterone concentrations (P4) and size of CL were evaluated to assess luteolysis at 0, 0.5, 1, 2, 4, 8, 24 and 48 h or at 0, 24 and 48 h after ILT, respectively. Cows in the ILT-0 and -5 groups were unaffected by ILT. The P4 concentrations were less in cows of the IM-500, as well as ILT-25, -50 and -100 groups at 48 h subsequent to ILT. The size of the CL was less in cows of IM-500, as well as ILT-25, -50 and -100 groups at 48 h after ILT. There were P4 concentrations of about 1 ng/mL 48 h after ILT in cows of the IM-500, as well as ILT-50 and -100 groups. In conclusion, the cloprostenol dose of 50 μg administered intra-luteally is a luteolytic dose in cows
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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