Using ammonium sulfate, three levels of dietary S (.15, .20, and .25%, DM basis) were evaluated in a finishing trial with 108 yearling crossbred heifers (384 kg). The basal diet contained (DM basis) 4% alfalfa hay, 6% sudangrass hay, 74% steam-flaked corn, 4% yellow grease, 6% cane molasses, and 6% protein-mineral supplement. Increasing dietary S decreased ADG (quadratic effect, P < .10), DMI (linear effect, P < .10), feed efficiency (quadratic effect, P < .10), diet NE (quadratic effect, P < .10), and longissimus muscle area (linear effect, P < .05). Six Holstein steers (218 kg) with cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on characteristics of digestion. Treatment effects on ruminal and total tract digestion of OM and N were small (P > .10). However, ruminal digestion of ADF and starch was slightly lower (quadratic effect, P < .10), and postruminal digestion of ADF and starch was correspondingly greater (quadratic effect, P < .05) with supplemental S. Dietary S level did not influence (P > .10) ruminal synthesis of microbial N. Increasing dietary S did not influence (P > .10) ruminal pH or lactic acid. Increasing S decreased molar proportions of acetate (quadratic effect, P < .10) and increased molar proportions of propionate (linear effect, P < .10). We conclude that S in excess of .20% of dietary DM may have detrimental effects on growth performance and dietary NE. Excessive dietary S may also compromise carcass merit by decreasing longissimus muscle area.
Para la caracterización de la curva de crecimiento se utilizaron los datos de 11 pesajes mensuales (1188 observaciones), desde los 8 hasta los 18 meses de edad correspondientes a 108 búfalos de la raza mestizo de Bufalipso que se encontraban en prueba de comportamiento entre los años 2007 y 2012, los cuales vinieron de 16 rebaños localizados en una empresa de la región occidental de Cuba. Los pesos individuales de cada animal fueron ajustados a las edades que correspondieron a cada uno de los pesajes, y además se utilizó un modelo mixto para corregir los mismos a los efectos mes y año de destete. En la estimación de la curva de crecimiento y sus parámetros (β0, β1 y β2) de los animales se utilizaron los modelos Brody, Gompertz, Von Bertalanffy y Logístico. La bondad de ajuste y discriminación entre los modelos utilizados demostraron un alto ajuste en los cuatros modelos, con R2 por encima de 90 %. El modelo Logístico fue el de mejor ajuste para describir la curva de crecimiento en machos bubalinos mestizos Bufalipso según los criterios estadísticos evaluados bajo estas condiciones.
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