Ingestive behaviour and forage intake responses of young and mature steers to the vertical differentiation of sugarcane in pen and grazing studies

Abstract

SUMMARYSugarcane is an important forage resource in sub-tropical and tropical areas as it is used during the winter or dry season when the growth rate of pastures is significantly reduced. The current research study assessed the effect of four vertical sections of sugarcane in a pen trial and the level of sugarcane utilization in a grazing trial on the ingestive behaviour and forage intake of two age groups of steers (1 and 2 years old). The pen trial was comprised of two simultaneous 4 × 4 balanced Latin square designs (one for each age group of animals) of four periods, four animals and four feeding treatments, which consisted of four equal vertical sections of sugarcane. Dry matter (DM) and digestible DM (DDM) intake per kilogram of metabolic weight declined gradually from top to bottom of the sugarcane, with no significant differences between the age groups of steers. This difference in intake was associated with a decline in intake of neutral detergent fibre (NDF) as a proportion of the liveweight of the animal and an increase of total chewing time per kilogram of DM or NDF from top to bottom of the sugarcane. It was concluded that the toughness of plant material played a significant role regulating intake, which was higher for the top sections of sugarcane. In the grazing trial, steers of both age groups grazed down sugarcane in three plots over 9 days. Steers grazed up to four distinctive grazing strata. Digestible DM intake (DDM intake) was high at low levels of horizontal utilization of the top grazing stratum but DDM intake started to decline sharply when this stratum was removed in 0·92 of paddock area (i.e. equivalent to 0·08 of the pasture area remaining un-grazed). It was concluded that the proportion of un-grazed area of the pasture can be used as a grazing management strategy to control forage intake for sugarcane.

The effect of stage of regrowth on the physical composition and nutritive value of the various vertical strata of kikuyu (<i>Cenchrus clandestinus</i>) pastures

“…It is well known from previous studies that beef and dairy cattle graze pastures in strata, and herbage quality declines from the top to the bottom of the swards (Ungar and Ravid 1999;Benvenutti et al 2016Benvenutti et al , 2017Ison et al 2018). These studies found that, when grazing pressure increased, cattle were forced to graze forage in the lower strata which was of lower quality and as a result diet quality and animal performance declined.…”

Tropical Grasslands-Forrajes Tropicales Vol.8 No.2 [May 2020]

“…It is well known from previous studies that beef and dairy cattle graze pastures in strata, and herbage quality declines from the top to the bottom of the swards (Ungar and Ravid 1999;Benvenutti et al 2016Benvenutti et al , 2017Ison et al 2018). These studies found that, when grazing pressure increased, cattle were forced to graze forage in the lower strata which was of lower quality and as a result diet quality and animal performance declined.…”

Long-term assessment of a new rotational-grazing management strategy called PUP-grazing (proportion of un-grazed pasture)

“…En el Renopa, la proporción de forraje remanente no pastado fue aproximadamente 11%, lo que permite que el consumo voluntario y por tanto la ganancia diaria de peso no sean limitados antes del cambio de potrero, como se observó en los estudios anteriores (Benvenutti et al 2016;2017). El mayor consumo voluntario de los animales en el sistema Renopa es debido al mejor acceso al estrato superior de la gramínea (= hojas con valor nutritivo más alto) por los animales.…”

“…No obstante esta estrategia es limitada por el hecho que la altura residual a la cual el consumo de forraje y la respuesta animal decrecen depende no solo de la especie de pastura sino también de la altura al comienzo del pastoreo (Benvenutti et al 2016;2017). Benvenutti et al (2016;2017) en pasturas del pasto Jesuita Gigante (Axonopus catarinensis) en un sistema de rotación y en caña de azúcar, encontraron que aplicando el criterio del forraje remanente no-pastado (Renopa) mejoró el consumo de forraje por bovinos en pasturas con diferentes alturas. En estos trabajos se encontró que al comienzo del periodo de ocupación los animales alcanzaron el mayor nivel de consumo diario de forraje especialmente en el estrato superior de hojas de la pastura.…”

“…El consumo se redujo cuando más del 90% de la superficie de la pastura fue defoliada por primera vez, debido a que los animales no tuvieron otra opción que consumir el estrato inferior de esta de menor calidad con alta proporción de tallos y material senescente. Con base en esta observación se determinó que el mejor indicador para el cambio de potrero de los animales sin pérdida de consumo de forraje era la proporción del remanente no-pastado, la cual fue equivalente entre el 5 y 10% del total del área del potrero, independiente de la especie de pastura y la altura al comienzo del pastoreo (Benvenutti et al 2016;2017). Este remanente estuvo normalmente asociado con sectores de la pastura contaminados por heces.…”