Prediction of the Energy Requirements for Growth in Beef Cattle 1. The irrelevance of fasting metabolism

Abstract

1. According to the Agricultural Research Council (1965) energy retention in cattle is predicted from metabolizable energy (ME) intake, the net availabilities of ME for maintenance (k m ) and for fattening (k f ) and measurements made of fasting metabolism (F). The present experiments were designed to examine the validity of the use of F as a basis from which to predict energy retention. 2. Four British Friesian and four Aberdeen Angus steers were fed, from weaning to slaughter at about 450 kg, a barley-based, pelleted diet at two levels calculated to yield overall efficiencies of retention of ME of 20% and 10% respectively. Successive measurements were made of the energy balance of each animal at intervals of 4 to 8 weeks. 3. The metabolizability of the diet was measured for both sheep and cattle. In both species metabolizability was greater at the higher level of feeding. In sheep k f measured directly or estimated from metabolizability was 0-61. 4. Measured values for F in cattle agreed closely with values given by the Agricultural Research Council. 5. Basal metabolism in the growing animal (F') was predicted by extrapolation to zero intake of measurements made on animals in positive energy balance. Log F' during growth was proportional to log body weight 073 . Expressed in terms of the usual exponent of metabolic body size, F' was about 440 kJ/kg 0 " 75 per 24 hr throughout growth. There were no major differences in F' attributable to breed or to level of food intake. 6. The results indicate that F is not a good basis from which to predict energy retention in steers.

Thyroid Hormone Concentrations: Some Kinetic Parameters of Triiodothyronine and Metabolic Rate in 'Double-Muscled' Cattle

“…The metabolic rate of 424 kJl kgo z;'Out l for the yearling bulls was significantly (P<0.05) higher than 357 kJl kgo zs'6ut 1 for the 3-yr-old bulls (Table 5). These values fall in the range of estimates surveyed by Webster (1978) For personal use only. Recently, experimental evidence has prompted the speculation that the maintenance requirements (Hanset et al 19'79) and the metabolic rate (Kolataj et al 1979) of Anim.…”

Maintenance requirements in metabolizable energy of adult, nonpregnant, nonlactating Charolais cows1

“…Animal behavior differed slightly between treatment groups but these differences were not sufficient to significantly alter ME,. Indeed, it was calculated that the difference in physical activity would account for energy requirements that would be higher by 1.4 kcal-kg BW-.75.d-1 for the H cows, assuming that the energy costs of eating and ruminating averaged 645 cal.kg BW-.75&1 (Webster, 1978) and 81 cal.kg BW-.75&1 (Toutain et al, 19771, respectively, and that sleep reduced energy expenditures by 86 cal.kg BW-.75&1 (Toutain et al, 1977).…”

Implications of fasting on the energy metabolism and feed evaluation in ruminants

“…In general the ME requirement for maintenance is about 1.35 times fasting heat production (Flatt, 1988). This has been criticized on several grounds by Marston (1948), Webster et al (1974), Ku Vera (1988) and Orskov and MacLeod (1990). When Marston (1948) fed sheep at half energy maintenance for 10 weeks and then fasted them, their mean fasting metabolic rate was 231 kJ/kg W 0 75 daily.…”