Visceral organ mass and cellularity in growth-restricted and refed beef steers.

Abstract

Beef steers were fed in two phases to compare the effects of diet and intake on growth and cellularity of visceral organs. During the growing phase (237 to 327 kg), steers were fed either a high (C) or low (F) concentrate diet. Diet F was available ad libitum (FA), whereas diet C was available either ad libitum (CA) or on a limited basis (CL) to match live weight gains of the FA group. During the finishing phase (327 to 481 kg), all steers received diet C either ad libitum (CA-CA, CL-CA, and FA-CA) or restricted (CL-CL and FA-CL) to 70% of the intakes of corresponding CA steers. Marked nutritional effects on liver growth (e.g., -25 and -15% in CL and FA, respectively, relative to CA) were due mainly to changes in cell size (i.e., protein:DNA), with smaller changes in cell numbers (i.e., DNA). Hyperplasia and hypertrophy played a role in growth of the forestomachs, although cell numbers and sizes tended to change in opposite directions, limiting magnitudes of changes in organ mass. Protein synthetic capacity (i.e., RNA) varied as well, often in parallel with cell number. This result differed from that observed in intestines, which maintained constant cell sizes but underwent marked changes in cell number. For liver, amounts of absorbed nutrients seemed to be the main factor driving hypertrophy. The organs of the gastrointestinal tract responded to physical and chemical signals, as shown by the effects of dietary fiber on growth of the forestomachs and intestines. Forestomachs responded mainly to diet fiber content, whereas the intestines responded to diet type and nutrient supply. Feeding programs for beef animals often include changes in diet type and periods of feed limitation, and these in turn affect visceral organ growth and metabolism. Because visceral organs are a major contributor to whole-body energy expenditures, factors affecting these tissues must be understood. This study supports the concept that workload determines organ size, but dietary factors influencing workload clearly vary for each organ.

Effects of Protein and/or Energy Restriction for Six Weeks, Followed with Nutritional Recovery on the Antioxidant Capacity and Development of Liver, Spleen and Muscle of Weaned Kids

“…Previous studies have demonstrated similar results (Yeh, 1983;Johnson et al, 1990;Sainz & Bentley, 1997;McLeod & Baldwin, 2000;D'Inca et al, 2010;Wang et al, 2005).…”

“…Previous studies have proven that nutritional restriction such as energy and protein delay the development of tissues (Sainz & Bentley, 1997;McLeod & Baldwin, 2000;Shen et al, 2004) and compensatory growth, defined as a phase of accelerated growth when favorable conditions are restored after a period of growth depression (Fabian et al, 2007;Heyer & Lebret, 2007). Previous studies also found that the deficiency of dietary protein and energy can lead to change the antioxidation capacity of tissues, such as reducing the concentrations of glutathione (GSH) and activity of superoxide dismutase (SOD) (Ogasawara et al, 1989), and further arouse an oxidative stress (Marks et al, 1996;Li et al, 2002), which retarded the development of tissues or organs though changing digestion and absorption (Li et al, 2010), nutrient metabolism (Robertson et al, 2003) and immune function (Tohyama et al, 2004).…”

Energy nutritional requirements for females of Nellore, Nellore × Angus and Nellore × Simmental fed on two forage: concentrate ratios

“…Observing the percentages of organs plus viscera (Table 4), one could expect that Nellore × Angus animals would present higher net energy requirement for maintenance, once, according to Sainz et al (1997), the size of visceral organs contributes to explaining differences in net energy requirements for maintenance of genetic groups. However, synthesis and protein degradation occurring in the organs and viscera represent 42% of the energy used by the gastrointestinal tract (Baldwin, 1995), i.e., such degradation is of great importance in energy requirements for maintenance.…”

Carbohydrate metabolism in meat animals

“…In meat animals the aerobic capacity decreases in the following order cattle > pig > poultry. The size of the heart in beef cattle has been reported to be approximately 0.44% of live weight (Sainz & Bentley, 1997) and in pigs 0.33% (Ruusunen & Puolanne, unpublished), and even greater difference is seen in the capillary density. In the longissimus muscle of cattle the capillary density is approximately 450/mm 2 (Karlström, Essén-Gustavsson, & Lindholm, 1994), but in pigs the value is only 150/mm 2 (Ruusunen & Puolanne, 2004).…”