Silaje de grano de sorgo húmedo con y sin urea o semilla de algodón como suplemento invernal en vaquillas

Para comparar el valor alimenticio del silaje de grano de sorgo húmedo con y sin urea o semilla de algodón para la recría de vaquillas en condiciones de pastoreo, se realizó un ensayo de suplementación invernal en potreros de Dichantium caricosum (2,25 animales/ha). Se utilizaron vaquillas cruza de 180 kg PV, clasificadas por fenotipo (tipos cebú o británico), que fueron asignadas aleatorizadamente a cuatro lotes, según recibieran (durante 6 días por semana durante 6 meses) silaje de grano de sorgo húmedo (SH, n = 10); SH + semilla entera de algodón (SH+SA, n = 16); SH + urea (SH+U, n = 16) o ningún suplemento (testigos, n = 10). Los suplementos fueron iso–energéticos y aportaron 3 Mcal EM /vez (2,6 Mcal EM /vaquilla/día). Los contenidos de proteína bruta fueron de 9% (SH) y 14,6% (SH+SA y SH+U). Mensualmente se registraron los pesos (con y sin desbaste), condición corporal (escala 1–9), altura a la cadera y perímetro torácico, así como las concentraciones séricas de nitrógeno ureico y proteínas totales. Los datos obtenidos se analizaron mediante el procedimiento GLM del programa SAS, bajo un modelo que incluyó: tratamiento, tipo y tratamiento x tipo, tomándose al animal como unidad experimental. Las vaquillas SH+SA registraron mayores ganancias de peso que el resto, en tanto que la ganancia de todos los animales suplementados aventajó a la de los testigos. La mejor evolución observada en SH+U comparada con SH se registró en julio–agosto, en coincidencia con la mayor concentración sérica de nitrógeno ureico en SH+U. Las proteínas séricas totales no fueron afectadas por los tratamientos. La mejor respuesta productiva se registró al utilizar semilla de algodón como fuente proteica

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

<p>Abstract</p> <p>In December of 3 years, 87 beef cows with nursing calves (594 ± 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (<it>Cynodon dactylon</it> [L.] Pers.)/bahiagrass (<it>Paspalum notatum</it> Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (<it>Triticum aestivum</it> L.) and ryegrass (<it>Lolium multiflorum</it> Lam., <b>WRG</b>), 2) wheat and ryegrass plus red clover (<it>Trifolium pretense</it> L., <b>WRR</b>), or 3) wheat and ryegrass plus white (<it>Trifolium repens</it> L.) and crimson clovers (<it>Trifolium incarnatum</it> L., <b>WRW</b>). All groups had <it>ad libitum</it> access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (<it>P</it> ≥ 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (<it>P</it> ≥ 0.17) among treatments; however, calves grazing pastures with clovers did tend (<it>P</it> = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (<it>P</it> = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.</p

The microbiome beyond the horizon of ecological and evolutionary theory

The ecological and evolutionary study of community formation, diversity, and stability is rooted in general theory and reinforced by decades of system-specific empirical work. Deploying these ideas to study the assembly, complexity, and dynamics of microbial communities living in and on eukaryotes has proved seductive, but challenging. The success of this research endeavour depends on our capacity to observe and characterize the distributions, abundances, and functional traits of microbiota, representing an array of technical and analytical challenges. Furthermore, a number of unique characteristics of microbial species, such as horizontal gene transfer, the production of public goods, toxin and antibiotic production, rapid evolution, and feedbacks between the microbiome and its host, are not easily accommodated by current ecological and evolutionary theory. Here we highlight potential pitfalls in the application of existing theoretical tools without careful consideration of the unique complexities of the microbiome, focusing particularly on the issue of human health, and anchoring our discussion in existing empirical evidence