Effects of grazing on deposition of chemical body components, energy retention and plasma hormones in steers

Abstract

The objective of this study was to evaluate the effects of grazing on the accretion of energy and chemical components in steers, using the comparative slaughter technique and taking into consideration the growth rate. Twelve Holstein steers aged 6 months and weighing 160 kg were divided into three treatment groups -an initial, grazing and control group. The initial group was slaughtered at the beginning of the experiment. The grazing group was grazed on timothy pastures for 18 weeks. The control group was kept in a stable and offered concentrate and timothy hay in a proportion of 2:1 throughout the 18 weeks. The amount of ration offered to the control group was adjusted in order to obtain a growth rate similar to that of the grazing group. The grazing and control groups were slaughtered at the end of the experiment. The grazing and the control groups had similar growth rates of approximately 0.8 kg/day throughout the experimental period and similar final live weights of approximately 260 kg. The grazing group had lower fat and energy deposition rates than the control group ( P < 0.05). Deposition rates of protein, fat, ash, moisture and energy were 130, 32, 30, 374 g/day and 4.4 MJ/ day, respectively, in the grazing group and 117, 85, 32, 381 g/day and 6.2 MJ/day, respectively, in the control group. The net energy for growth was lower in the grazing group (7.7 MJ/kg) than in the control group (9.9 MJ/kg, P < 0.05). The grazing group had higher plasma concentrations in growth hormone and lower plasma concentrations in insulin and insulin-like growth factor 1 than those in the control group ( P < 0.05).

Basal levels and responses to glucose infusion of plasma glucose and insulin in beef steer before and after the end of the growing phase on pasture

“…(1995) compared the plasma metabolites and insulin levels of growing beef steers reared on pasture with those of beef steers fed in a barn, which grew at the same rate, and suggested that grazing might exert a preferable effect in providing energy sources such as glucose to the peripheral tissues. These findings were partly supported by Hata et al . (2005).…”

“…(1995) showed that the level of plasma glucose was higher, while that of plasma insulin was lower in grazing steers (4 months of age) that were not fed the concentrate when compared with the control animals that were fed hay and concentrate to achieve a similar growth rate in both groups (0.7 kg/day). Hata et al . (2005) demonstrated a lower insulin level in grazing animals that were not fed the concentrate and that differences were not observed in the plasma glucose level when compared with animals kept indoors (9 months of age and grown at approximately 0.7 kg/day).…”

Body composition and net requirements of protein and energy for weight gain of Nellore and crossbreed steers finished under grazing

“…The rate of gain would be strongly and positively associated to fat deposition (NRC, 2000), which would explain mainly the lower body concentration of fat and higher body concentration of protein in grazing animals (Table 6), compared to confined animals (Fontes, 1995;Zervoudakis et al 2002;Fontes et al, 2005b). This pattern, however, would not result only by the lowest rates of weight gain, but also by the direct effect of grazing on body composition (Hata et al, 2005).…”

“…The nutritional requirements of grazing animals would differ markedly from that observed for confined animals (Zervoudakis et al, 2002), due not only to lower performance of animals on pasture, but also to the effect of grazing itself (Hata et al 2005).…”

Quantitative Comparison of Diversity and Conformity in Nitrogen Recycling of Ruminants

“…Cattle and sheep are grass/roughage eaters and have a larger rumen and smaller hindgut compared with animals in concentrate selector and intermediate groups. Furthermore, compared with sheep, cattle have a relatively greater omasum and a smaller large intestine (McLeod and Baldwin, 2000;Hata et al, 2005). Lapierre and Lobley (2001) summarized available published data quantifying trans-hepatic VA differences and concluded that urea production rate is positively correlated with digestible N intake.…”