4,517 research outputs found

    Invited commentary

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    Diet shifts of juvenile red snapper (Lutjanus campechanus) with changes in habitat and fish size

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    We examined the diets and habitat shift of juvenile red snapper (Lutjanus campechanus) in the northeast Gulf of Mexico. Fish were collected from open sand-mud habitat (little to no relief), and artificial reef habitat (1-m3 concrete or PVC blocks), from June 1993 through December 1994. In 1994, fish settled over open habitat from June to September, as shown by trawl collections, then began shifting to reef habitat — a shift that was almost completed by December as observed by SCUBA visual surveys. Stomachs were examined from 1639 red snapper that ranged in size from 18.0 to 280.0 mm SL. Of these, 850 fish had empty stomachs, and 346 fish from open habitat and 443 fish from reef habitat contained prey. Prey were identified to the lowest possible taxon and quantified by volumetric measurement. Specific volume of particular prey taxa were calculated by dividing prey volume by individual fish weight. Red snapper shifted diets with increasing size. Small red snapper (<60 mm SL) fed mostly on chaetognaths, copepods, shrimp, and squid. Large red snapper (60–280 mm SL) shifted feeding to fish prey, greater amounts of squid and crabs, and continued feeding on shrimp. We compared red snapper diets for overlapping size classes (70–160 mm SL) of fish that were collected from both habitats (Bray-Curtis dissimilarity index and multidimensional scaling analysis). Red snapper diets separated by habitat type rather than fish size for the size ranges that overlapped habitats. These diet shifts were attributed to feeding more on reef prey than on open-water prey. Thus, the shift in habitat shown by juvenile red snapper was reflected in their diet and suggested differential habitat values based not just on predation refuge but food resources as well

    Understanding functional benefits of Isoleucine and Arginine on poultry performance and health.

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    Poultry industry is rapidly moving towards utilizing the best ingredients to precisely feed the birds for better performance, welfare, health, and profitability. One of the practices that evolved over time with research is better optimization of amino acid utilization in the diets thus changing the crude protein landscape. Historically, if we compare the modern diets to diets from 1980, significant changes are visible in the use of unbound or crystalline amino acids leading to reduced levels of CP and reduced unutilized nitrogen in the diets. Multiple feed-grade amino acids are available in a cost-effective manner in poultry diets. Multiple research has been conducted over 80 years to better understand the optimal requirement of lower limiting amino acids in poultry, formulation with digestible amino acid values, and ideal amino acid formulation to achieve precision feeding of nutrients. Those findings enabled the nutritionist to incorporate crystalline amino acids, remove CP minimum, and crystalline amino acid maximum in the diets to lower the feed cost, reduce CP, reduce excess nitrogen in hindgut and improve the health of the birds and improve litter quality (Kidd 2000; Maia et al., 2021). A 1960 diet would only contain the Methionine as synthetic amino acid, whereas the 2023 diet would contain up to 5/6 limiting amino acids in USA-based broiler diets. The 4th, 5th and 6th limiting amino acids in USA-based poultry diets are usually Valine (Val), Isoleucine (Ile) and Arginine (Arg) depending on the ingredients used. With almost 90% of the industry using the 4th limiting amino acid, there is a need to understand the optimal requirement of 5th and 6th limiting amino acids for performance and other biological functionality. With Ile and Arg being the 5th and 6th limiting amino acid in most broiler, turkey, and layer diets, this article will discuss the importance of Ile and Arg in birds and the effect on performance and health

    Understanding functional benefits of Isoleucine and Arginine on poultry performance and health.

    Get PDF
    Poultry industry is rapidly moving towards utilizing the best ingredients to precisely feed the birds for better performance, welfare, health, and profitability. One of the practices that evolved over time with research is better optimization of amino acid utilization in the diets thus changing the crude protein landscape. Historically, if we compare the modern diets to diets from 1980, significant changes are visible in the use of unbound or crystalline amino acids leading to reduced levels of CP and reduced unutilized nitrogen in the diets. Multiple feed-grade amino acids are available in a cost-effective manner in poultry diets. Multiple research has been conducted over 80 years to better understand the optimal requirement of lower limiting amino acids in poultry, formulation with digestible amino acid values, and ideal amino acid formulation to achieve precision feeding of nutrients. Those findings enabled the nutritionist to incorporate crystalline amino acids, remove CP minimum, and crystalline amino acid maximum in the diets to lower the feed cost, reduce CP, reduce excess nitrogen in hindgut and improve the health of the birds and improve litter quality (Kidd 2000; Maia et al., 2021). A 1960 diet would only contain the Methionine as synthetic amino acid, whereas the 2023 diet would contain up to 5/6 limiting amino acids in USA-based broiler diets. The 4th, 5th and 6th limiting amino acids in USA-based poultry diets are usually Valine (Val), Isoleucine (Ile) and Arginine (Arg) depending on the ingredients used. With almost 90% of the industry using the 4th limiting amino acid, there is a need to understand the optimal requirement of 5th and 6th limiting amino acids for performance and other biological functionality. With Ile and Arg being the 5th and 6th limiting amino acid in most broiler, turkey, and layer diets, this article will discuss the importance of Ile and Arg in birds and the effect on performance and health

    K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147

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    We identify a sub-Neptune exoplanet (Rp=2.5±0.2R_p = 2.5 \pm 0.2 R_\oplus) transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H] = +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2 Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%, and a duration of ~4 hours. Based on our analysis of high-resolution MIKE spectra, broadband optical and NIR photometry, the cluster parallax and interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST, we estimate the following properties for the host star: M=1.01±0.03M_\star = 1.01 \pm 0.03 M_\odot, R=0.95±0.03R_\star= 0.95 \pm 0.03 R_\odot, and Teff=5695±50T_{\rm eff} = 5695 \pm 50 K. This star appears to be single, based on our modeling of the photometry, the low radial velocity variability measured over nearly ten years, and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry. Applying a probabilistic mass-radius relation, we estimate that the mass of this planet is Mp=7+53M_p = 7 +5 -3 M_\oplus, which would cause a RV semi-amplitude of K=2±1K = 2 \pm 1 m s1^{-1} that may be measurable with existing precise RV facilities. After statistically validating this planet with BLENDER, we now designate it K2-231 b, making it the second sub-stellar object to be discovered in Ruprecht 147 and the first planet; it joins the small but growing ranks of 23 other planets found in open clusters.Comment: 24 pages, 7 figures, light curve included as separate fil
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