Empty body weight gain, protein, faty and energy deposit and utilization of metabolizable energy for energy deposit in black and white bulls. 2. Relationship between energy deposit and intake of metabolizable energy

The protein, fat and energy deposition determined in 6 series of individual feeding experiments with different energy supply on slaughter steps (altogether 458 animals) and whole body analysis were generalized in this publication on nonlinear regression analyses. The protein deposition per kg empty body weight gain is influenced by empty body weight, it takes off with increase of the empty body weight. At low empty body weight (100-200 kg) the protein deposition per kg empty body weight gain is small increased with increasing of empty body weight gain, at high empty body weight it is reduced continuously. The fat deposition per kg empty body weight gain increases progressively with the empty body weight and with the empty body weight gain respectively. The energy deposition per kg empty body weight gain increases with increase of empty body weight and of empty body weight gain. It showed the same development like the fat deposition. The protein, fat and energy deposition per kg live weight gain are calculated and tabulated in dependence on the live weight and the live weight gain.

Six series of individual feeding experiments (altogether 544 animals) with different energy supply and connected with steps slaughteries and whole-body analyses, constructed carried out and analysed upon the same aspects, were regression analytically interpreted with the aim of quantify the relation of empty body weight to live weight. The relation of empty body weight to live weight showed a nonlinear dependence on the live weight as well as on the age of animals. The assessment of the metabolizability of energy of the diet as an additional variable reduced the residual variation considerably. Therefore from the knowledge of live weight or age of the animals, and the metabolizability of energy of the diet the relation of empty body weight to live weight of black and white bulls could be calculated. Moreover, the relation of empty body weight gain to live weight gain in dependence on live weight and live weight gain was investigated.

Objectives of the study were to 1) describe body composition and composition of gain of crossbred steers sired by Angus, Hereford, Belgian Blue, or Piedmontese sires from Angus, Hereford, or MARC III dams and 2) determine the influence of sire and dam type on energy utilization during the finishing period. Beginning at 330 kg, 70 steers were adjusted to a high-corn diet and individual feeding. Steers were assigned, by sire and dam breed, to be killed as an initial slaughter group or fed either a limited amount or ad libitum for 140 d, then killed. Organ weights, carcass traits, and body composition were obtained. Effects included in the statistical model were nutritional treatment (T), sire breed (S), dam breed (D), and the S x T and D x T interactions. All traits were influenced (P < .05) by T. Sire influenced longissimus area, fat thickness, and quality and yield grade (P < .01); weight of hide, stomach complex, heart, lung, spleen, empty body fat, protein, ash, and energy; rates of fat, protein, and energy gains; and water, fat, ash, and energy content of gains (P < .10). Dam breed influenced (P < .10) DM and ME intake, fat thickness, yield grade, heart, lung, and spleen weights, and rates of water, fat, protein, and energy gains. Rates of DM or ME intake, live and empty body weights, and water, protein, ash, and energy gains were influenced (P < .05) by D x T. Neither S nor D influenced (P > .10) regressions of heat production on ME intake. Fasting heat production and maintenance were estimated to be 80.6 and 124.4 kcal ME/(kgx75xd). The nonlinear relationship between energy gain (Y, kcal/[kgx75xd]) and ME intake (X, kcal/[kgx75xd]) was Y = 74.69 x (1 - 2.60 x exp(-.0159x(ME - 80.597))), and indicated energy gain approached an asymptote (74.69) as ME intake increased. This relationship also implies that efficiency of ME use for gain decreased as ME intake increased.

Body composition and net energy and protein requirements of Morada Nova lambs

Energy utilization for maintenance and growth in preruminant kid goats and lambs

The objective of this study was to determine the nutritional requirements of energy and protein and estimate the efficiencies of metabolizable energy utilization for fat and protein deposition, as well as for maintenance (km) and growth (kg). An experiment of comparative slaughter was carried out with thirty-seven 14-month-old (±1 month) Nellore bulls with 259±24.9 kg. Animals were divided as follows: five to reference, four to maintenance level and twenty-eight bulls feeding ad libitum. Bulls were also grouped in 4 different feedlot periods (42, 84, 126 and 168 days) for slaughter. The diet was composed of corn silage and concentrate, at a 55:45 ratio. After the slaughter, the left half carcasses were totally dissected for determination of body composition. The energy requirements for maintenance were obtained by exponentially relating the heat production and the metabolizable energy intake, while the energy requirements for gain (NEg) were obtained according to empty body weight (EBW) and EBW gain (EBG). The net protein requirements for gain (NPg) were estimated according to EBG and retained energy (RE). The net (NEm) and metabolizable (MEm) energy requirements for maintenance were 76.5 and 113.84 kcal/EBW0.75/day, respectively. The km was 0.67. The equations for NEg and NPg were: NEg (Mcal/day) = 0.0555 × EBW0.75 × EBG1.095 and NPg (g/day) = 263.37 × EBG - 23.21 × RE. The kg was 0.33. The efficiencies to deposition of energy as protein and fat were 0.18 and 0.71, respectively. The model obtained for the percentage of retained energy as protein (%REp) was %REp = 2.4221 × (RE/EBG)-1.6472. The net and metabolizable energy requirements for maintenance of Nellore bulls were 76.5 and 113.84 kcal/EBW0.75/day. The energy and protein requirements for gain could be obtained by the respective equations: NEg (Mcal/day) = 0.0555 × EBW0.75 × EBG1.095 and NPg (g/day) = 263.37 × EBG - 23.21 × RE.

The present study was conducted to estimate energy requirements for maintenance in laying hens by using indirect calorimetry and energy balance. A total of 576 28-wk-old Nongda-3 laying hens with dwarf gene were randomly allocated into four ME intake levels (86.57, 124.45, 166.63 and 197.20 kcal/kg body weight (BW)0.75 per d) with four replicates each. After a 4 d adaptation period, 36 hens from one replicate were maintained in one of the two respiration chambers to measure the heat production (HP) for 3 d during the feeding period and subsequent 3 d fast. Metabolizable energy (ME) intake was partitioned between heat increment (HI), HP associated with activity, fasting HP (FHP) and retained energy (RE). The equilibrium FHP may provide an estimate of NE requirements for maintenance (NEm). Results showed that HP, HI and RE in the fed state increased with ME intake level (p<0.05). Based on the regression of HP on ME intake, the estimated ME requirements for maintenance (MEm) was 113.09 kcal/kg BW0.75 per d when ME intake equals HP. The FHP was decreased day by day with the lowest value on the third day of starvation. Except for lowest ME intake level, the FHP increased with ME intake level on the first day of starvation (p<0.05). The FHP at the two higher ME intake levels were greater than that at the two lower ME intake levels (p<0.05) but no difference was found between the two lower ME intake levels. Linear regression of HP from the fed state to zero ME intake yielded a value of 71.02 kcal/kg BW0·75 per d, which is higher than the extrapolated FHP at zero ME intake (60.78, 65.23 and 62.14 kcal/kg BW0.75 per d for the first, second and third day of fasting, respectively). Fasting time, lighting schedules, calculation methods and duration of adaptation of hens to changes in ME intake level should be properly established when using indirect calorimetry technique to estimate dietary NE content, MEm and NEm for laying hens.

Two experiments were conducted to measure efficiency of energy use in limit-fed cows. In Exp. 1, 32 pregnant, crossbred cows were used to examine the effects of dietary energy concentration and intake level on energy utilization and digestion. In a 2 × 2 factorial treatment arrangement, cows received diets formulated at either 1.54 Mcal NEm/kg high energy (H) or 1.08 Mcal NEm/kg low energy (L); amounts of each diet were fed at amounts to achieve either 80% (80) or 120% (120) of maintenance energy requirements. Fecal grab samples were collected on days 14, 28, 42, and 56 for determination of energy digestion and metabolizable energy (ME) intake. Acid detergent insoluble ash and bomb calorimetry were used to estimate fecal energy production. Cow body weight and 12th rib fat thickness were used to estimate body energy, using 8 different methods, at the beginning and end of a 56-d feeding period. Energy retention (RE) was calculated as the difference in body energy on days 0 and 56. Heat energy (HE) was calculated as the difference in ME intake and RE. Energy digestion increased (P = 0.04) with intake restriction. Cows consuming H tended to have greater (P = 0.08) empty body weight (EBW) gain than cows consuming L, but no difference was observed (P = 0.12) between cows fed 120 compared with cows fed 80. Estimates of HE were greater for L than H (P < 0.01) and greater for 120 than 80 (P < 0.01), such that estimated fasting heat production of H (57.2 kcal/kg EBW0.75) was lower than that of L (73.3 kcal/kg EBW0.75). In Exp. 2, 16 ruminally cannulated, crossbred steers were used to examine the effects of dietary energy concentration and intake level on energy digestion. Treatment arrangement and laboratory methods were replicated from Exp. 1. Following a 14-d adaptation period, fecal samples were collected, such that samples were represented in 2-h intervals post-feeding across 24 h. Diet × intake interactions were observed for nutrient digestibility. Energy digestibility was greater in steers fed H than in steers fed L (P < 0.01); however, digestibility of each nutrient increased by approximately 10% in steers fed H80 vs. those fed H120 (P ≤ 0.03); nutrient digestibility was similar among levels of intake in steers fed L (P = 0.54). These results suggest that intake restriction may increase diet utilization and that the magnitude of change may be related to diet energy density.

There is uncertainty whether feed efficiency traits are related to energetic efficiency. The objective of this study was to utilize comparative slaughter data to evaluate the relationships of feed efficiency traits with maintenance energy requirements (MEm) and efficiency of metabolizable energy (ME) use for maintenance (km) and gain (kg). Published data were compiled (31 studies, 214 treatment means) on metabolizable energy intake (MEI) and composition of empty body gain in growing cattle. Data analyses were performed using R statistical software considering each treatment mean as an independent experimental unit. Assuming fasting heat production (FHP) varies only due to empty body protein (EBP) composition, it was computed as 295 kcal/kg EBP.75. MEm, km, and kg were computed from the nonlinear relationship between heat production and MEI. Residual intake (lower is more efficient) was computed as the residual from linear regression of MEI on EBW and EBW gain (RMEI) or MEI on EBP, retained energy as protein and retained energy as fat (RMEIc). Residual gain (higher is more efficient) was computed as the residual from linear regression of EBW gain on EBW and MEI (REBG) or retained energy on EBP and MEI (RRE). MEI was positively correlated with RMEI (0.46) and RMEIc (0.44), and EBW gain was correlated with REBG (0.58) and RRE (0.39). FHP was correlated with RMEIc (-0.25). MEm was weakly correlated with RMEI (0.19), RMEIc (0.22), and REBG (-0.26), but strongly correlated with RRE (-0.51). km was moderately correlated with RMEI (-0.35), but strongly correlated with REBG (0.49), RMEIc (-0.59), and RRE (0.79). kg was strongly correlated with RMEI (-0.69), REBG (0.47), RMEIc (-0.89), and RRE (0.70). Correlations among feed efficiency traits were strong (&amp;gt;±0.48). In conclusion, feed efficiency traits using retained energy as the dependent variable had stronger correlations with maintenance energy requirements than those using feed intake as the dependent variable.

Metabolism and comparative slaughter feedlot trials were conducted with 85 Angus-Hereford crossbred steers to evaluate effects of isocaloric diets with five levels of N on protein and energy deposition in tissues. The diets had Urea Fermentation Potentials (UFP) of 3.8, 1.2, -1.4, -3.9 and -6.9 and metabolizable protein (MP) levels of 69.2, 76.6, 80.1, 80.8 and 80.0 g/kg dry matter, respectively, with increasing dietary N levels. Crude protein digestibility increased (P less than .005) with increasing N levels, but total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME) showed no significant relationship to variation in N level. Metabolism trial N and energy utilization indicates that N to energy balance occurred at zero to slightly negative UFP. In the feedlot trial, average daily gain, ME intake, dry matter intake and energy gain increased with increasing dietary MP level. Daily gains in empty body fat and energy and carcass characteristics indicating increased finish also increased with increasing MP level. However, empty body protein gain increased with increased N level and indicated that in isocaloric diets, urea-N could replace a portion of the plant protein without decreasing tissue protein gains. The results support the UFP system for determining N to energy balance in feedlot diet.

Effect of body condition and energy utilization on the length of post-partum anoestrus in PRID-treated and untreated post-partum<i>Bos indicus</i>(Zebu) cattle

In a stress-free environment and given adequate intakes of essential nutrients, protein deposition (PD) in growing pigs is determined by either energy intake or the genetically determined upper limit to body protein deposition (PDmax). In this experiment, the effect of metabolizable energy (ME) intake on PD was determined in 24 female pigs between 25 and 70 kg BW. Casein and cornstarch-based diets that were not limiting in any of the essential nutrients were offered semi-ad libitum (12 pigs) or restrictively at 1.8, 2.2, or 2.6 times the ME requirements for maintenance (MEm; four pigs at each level of ME intake). Nitrogen balances were determined over 7-d periods at approximately 25, 40, and 70 kg BW. The serial slaughter method was used to determine average PD over the entire BW range. Based on the N balances, PD increased up to intakes of 22.6, 21.3, and 25.1 MJ ME/d at 25, 40, and 70 kg BW, respectively. At higher ME intakes, PDmax was at least 156 g/d at 25 kg body weight; it was 149 g/d at 40 and 150 g/d at 70 kg BW. The serial slaughter technique showed a PDmax of 127 g/d at ME intakes above 22.5 MJ/d. At 25 kg BW, intakes of ME of approximately four times MEm are necessary to achieve PDmax. The results indicate that PDmax at 25 kg BW is at least as high as at 40 and 70 kg BW.

The effects of energy metabolism variables on feed efficiency in respiration chamber studies with lactating dairy cows

Estimation of metabolizable energy (ME) requirement for maintenance (ME) and growth (ME) in pre-weaned lambs have been limited to milk-only fed lambs. This study aimed to determine energy and nitrogen metabolisability of milk and pellets when fed together, compare the growth and chemical body composition of lambs fed varying levels of pellets in addition to milk, and to estimate ME, ME, and the CP:ME ratio requirements for growth. The study included 32 twin-born Romney-cross ram lambs. Four lambs were slaughtered at 24 h post-partum to estimate initial body composition and the remaining 28 were assigned to 1 of 4 treatment groups of 7. Group 1 was fed milk replacer (MR) only; group 2 was fed MR and allowed ad libitum access to pellets; groups 3 and 4 were offered 30% and 60%, respectively of the average pellet intake of the ad libitum group the previous day while being fed MR. Milk replacer was fed as a proportion of the lamb's live weight (LW). Lambs from each treatment were placed in metabolic cages at 17 kg LW for 4 d to allow for total fecal and urine collection. All lambs were slaughtered at 18 kg LW. The ADG, ADG:ME ratio, stomach and liver weight, and rumen papillae lengths increased ( < 0.05) with increasing pellet intake. Increasing daily ME intake increased ( < 0.05) both daily energy and protein deposition but had no effect ( > 0.05) on fat deposition. However, the total chemical body composition was unaffected ( > 0.05) by dietary treatment. Digestibility of energy and N decreased ( < 0.05) with increasing ME intake. Percent energy and N retained for growth were 96% vs. 71% and 72% vs. 30% for milk and pellets, respectively. The ME and ME values obtained were 0.40 MJ ME/kg LW·d and 13.8 MJ ME/kg ADG, respectively. The CP:ME ratio of MR and pellet was 11.1 and 15.7, respectively. However, a simulation model suggested that lambs require a CP:ME ratio of 13.1 at 5 kg and 10.9 at 18 kg LW, indicating that protein intake may be limiting to lamb growth in early life and in excess by 18 kg LW. In conclusion, increasing pellet intake was associated with decreased N retention. The inclusion of pellets, however, improved the efficiency of ME utilization for growth in pre-weaned lambs and was beneficial for rumen development. The ME was higher than previously recommended values and the CP:ME intake of lambs does not match their requirements which may warrant further studies.

Toward a new theory of feed intake regulation in ruminants 3. Optimum feed intake: in search of a physiological background