Physical and chemical components of the empty body during compensatory growth in beef steers.
TL;DR: Reduced NEg requirements and changes in gut fill accounted for most of the compensatory growth response exhibited in these steers, and net energy requirements for growth were approximately 18% lower for CG steers.
Abstract: The composition of carcass and noncarcass tissue growth was quantified by serial slaughter of 26 Angus x Hereford crossbred steers (initial age and weight 289 +/- 4 d and 245 +/- 4 kg) during continuous growth (CON) or compensatory growth (CG) after a period of growth restriction (.4 kg/d) from 245 to 325 kg BW. All steers were fed a 70% concentrate diet at ad libitum or restricted levels. Homogenized samples of 9-10-11th rib and noncarcass tissues were analyzed for nitrogen, fat, ash, and moisture. Growth rate from 325 to 500 kg BW was 1.54 and 1.16 kg/d for CG and CON steers. The weight of gut fill in CG steers was 10.8 kg less (P less than .05) before realimentation and 8.8 kg more (P less than .10) at 500 kg BW than in CON steers. The allometric accretive rates for carcass chemical components relative to the empty body were not affected by treatment. However, the accretive rates for CG steers were greater (P less than .01) for noncarcass protein (.821 vs .265), noncarcass water (.861 vs .507), and empty-body protein (.835 vs. .601) than for CON steers. Final empty-body fat was lower (P less than .001; 24.2 vs 32.4%) and empty-body protein higher (P less than .001; 16.6 vs 14.8%) in CG steers than in CON steers. Consequently, net energy requirements for growth (NEg) were approximately 18% lower for CG steers. We conclude that reduced NEg requirements and changes in gut fill accounted for most of the compensatory growth response exhibited in these steers.
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TL;DR: The role of plasma IGF-I during compensatory growth is not clear and must be explained in connection with changes of its binding proteins, which seem to have a permissive effect on growth.
425 citations
TL;DR: The protein:fat ratio of the carcass can be increased through increasing mature size, by administering hormones or hormonal modifiers, by limiting energy intake during the growing period or finishing period, or by slaughtering cattle at an earlier stage of maturity.
Abstract: Growth in animals is defined as accretion of protein, fat and bone. Although growth typically is measured as the change in live weight, nutrient retention is estimated more precisely by measuring empty body weight and composition, whereas production economics are measured ideally through carcass weights and quality. As a percentage of live weight gain, carcass weight gain usually is a much higher percentage during the feedlot phase than during the growing phase of production because dressing percentage (ratio of carcass:live weight) increases with maturation and is greater with concentrate than with roughage diets. At a given fraction of mature body size (maximum body protein mass), body fat percentage seems to be a constant. Mature size may be altered genetically and nutritionally. Protein accretion declines to zero when cattle reach their mature body size (approximately 36% fat in empty body weight in modern cattle) even though mature animals can continue to accrete fat. Although fat accretion can be reduced by limiting the supply of net energy, rate of fat accretion by finishing steers given ad libitum access to high-concentrate diets seems to reach a plateau at approximately 550 g daily. Protein mass, in contrast, increases in proportion to empty body weight. The protein:fat ratio of the carcass can be increased through increasing mature size, by administering hormones or hormonal modifiers, by limiting energy intake during the growing period or finishing period, or by slaughtering cattle at an earlier stage of maturity. Energetically, efficiency of accretion of fat is approximately 1.7 times that of protein. But because more water is stored with deposited protein than with deposited fat, lean tissue gain is four times as efficient as accretion of fat tissue. Conversion of protein to fat is very inefficient, suggesting that excess protein is utilized inefficiently.
412 citations
TL;DR: The traditional way of using feeding as a quality control tool in the production of meat is re-thinked and the potential of a nutrigenomic approach is introduced as a first step in the development of pro-active quality control systems which fulfil future demands from industry and consumers.
205 citations
TL;DR: Beef steers were fed in two phases to determine the relative importance of changes in DMI, gastrointestinal tract fill, energy expenditures, and composition of gain in the compensatory growth phenomenon and to examine changes in carcass composition and quality resulting from different types of growth restriction.
Abstract: Beef steers were fed in two phases 1) to determine the relative importance of changes in DMI, gastrointestinal tract fill, energy expenditures, and composition of gain in the compensatory growth phenomenon, 2) to compare the effects of growth restriction due to ad libitum consumption of a low-energy (low-concentrate) diet to those of limited intake of a high-energy (high-concentrate) feed, and 3) to examine changes in carcass composition and quality resulting from different types of growth restriction. During the growing phase (237 to 327 kg), steers were fed either a high- (C) of low- (F) concentrate diet. Diet F was available for ad libitum consumption (FA) and diet C was available either for ad libitum consumption (CA) or on a limited basis (CL) to match the live weight gains by the FA group. During the finishing phase (327 to 481 kg), all steers received diet C, either for ad libitum consumption (CA) or restricted (CL) to 70% of the intake by the corresponding CA steers. Backfat thickness was markedly reduced (P < .001) by final feed restriction (7.4 and 6.9 mm for CL-CL and FA-CL respectively), compared with CA-CA (12.6 mm). Backfat also was lower in CL-CA (11.6 mm, P < .10) and FA-CA (9.9 mm, P < .05) than in CA-CA steers. Conversely, marbling scores were similar among groups, except for the FA-CL steers, which had lower marbling scores than FA-CA and CL-CA steers (P < .05). Higher DMI following growth restriction were accompanied by increased rates of live weight (+54 and +27%) and empty body weight (EBW; +57 and +43%) gain for CL-CA and FA-CA steers, respectively, compared with CA-CA steers. Gain:feed (EBW basis) were improved in some restricted/refed groups (+30, +13, and +10%, for Cl-CA, CL-CM respectively CA-CA. Increased DMI played a major role in the compensatory gain response in both CL-CA and FA-CA groups. Maintenance requirement was reduced (-17%) in CL-CA and increased in the FA-CA group (+21%); both changes affected the magnitude of compensatory gain in those animals. In contrast, composition of gain had little or no effect on the compensatory gain response. Programmed feeding can be used to manipulate carcass quality, but low-concentrate feeding during the growing phase may impair overall feedlot performance.
205 citations
TL;DR: Results indicate that enhanced growth rates in the early phase of compensatory growth are associated with the physiological response of the GH-IGF-I-insulin axis coupled with reduced maintenance requirement due to slower metabolic rate in restricted-refed heifers.
Abstract: Twelve recently weaned Hereford crossbred heifers weighing 227 kg (12 kg SD) and aged 230 d ( 8 d SD) on d 0 were used to investigate physiological responses associated with compensatory growth. Six heifers were allotted to ad libitum intake ( ADLIB) and six were restricted to a maintenance diet for 95 d followed by realimentation ( REST ). Plasma collected from all heifers during feed restric- tion (d 0, 20, 48) and realimentation (d 104, 125, 153, 195) was analyzed for growth hormone ( GH) , insu- lin-like growth factor I ( IGF-I) , thyroid hormones (thyroxine (T4) and triiodothyronine (T3)), insulin, glucose, nonesterified fatty acids ( NEFA) , blood urea nitrogen ( BUN) , and 3-methyl histidine ( 3-MH ). Resting metabolic rate ( RMR) was measured 5 d before and 15 and 36 d after the beginning of realimentation. Feed restriction was associated with higher ( P .05) between treatments were observed on d 104 (d 10 of realimentation) and thereafter. Conversely, GH con- centration in REST heifers remained elevated through d 104 but dropped to ADLIB levels by d 125 (d 31 of realimentation). The T4 and T3 concentrations re- mained lower ( P < .05) in REST than in ADLIB heifers after 10 d of realimentation but rose to control levels by d 31 of realimentation. The RMR was lower ( P < .05) in REST than in ADLIB heifers 15 d into realimentation; however, no difference was found between treatments by d 36 of realimentation. These results indicate that enhanced growth rates in the early phase of compensatory growth are associated with the physiological response of the GH-IGF-I- insulin axis coupled with reduced maintenance re- quirement due to slower metabolic rate in restricted- refed heifers.
176 citations
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TL;DR: Compensatory growth did not persist as long in the sheep as in the cattle, and they remained lighter than the controls at the end of the experiment, but the greater persistence of compensatory growth in the livestock was due to their intake remaining elevated longer.
Abstract: Sheep and cattle often exhibit compensatory growth following nutritional restriction. Complete compensation, that is the same weight at the same age as non-restricted contemporaries, has often been observed in sheep but not in cattle. In this experiment the compensatory growth of sheep and cattle was measured after their nutrition had been restricted sufficiently to induce losses in body weight. The growth, feed intake and feed conversion efficiency of the compensating sheep and cattle, measured during re-alimentation, was compared to control animals fed ad libitium throughout the experiment. A high-quality diet was used to maximize the opportunity for compensatory growth. The cattle exhibited compensatory growth for the 11 months between re-alimentation and the end of the experiment, and were able to compensate completely. Compensatory growth did not persist as long in the sheep as in the cattle, and they remained lighter than the controls at the end of the experiment. During the first 12 weeks of re-alimentation there was no difference in the feed intake of the compensating and control animals in both species. Compensatory growth during this time was due to the greater efficiency of the compensating animals. After this initial 12 weeks the feed intake of the compensating animals increased, and the subsequent compensatory growth could be fully accounted for by greater feed intake. The greater persistence of compensatory growth in the cattle was due to their intake remaining elevated longer.
94 citations
TL;DR: Chemical composition of the empty body was determined in 159 animals slaughtered at weights ranging from 121 to 706 kilograms and a breed influence on the accretion rate of chemical fat was detected only among bulls, where Angus had a more rapid accretion rates.
Abstract: Chemical composition of the empty body was determined in 159 animals slaughtered at weights ranging from 121 to 706 kilograms. Holstein and Angus bulls, steers and heifers were fed at two energy levels: ad libitum and 65 to 70% ad libitum. The allometric equation, Y = aXb, was used to determine the effect of energy intake and the influence of breed and sex on the accretion rates of the chemical components relative to the growth of the empty body or fat-free empty body. Group comparisons for chemical composition were made after adjustment by regression to a common empty body weight. The expression of the sex influence on the accretion rates of water, protein and ash relative to the empty body depended on the breed and the energy intake level considered. The accretion rate of chemical fat was not influenced by sex. Genetic differences in the accretion rate relative to the empty body were detected only among animals in the high energy intake group. Regardless of sex, the accretion rates of protein and ash were more rapid (P < .05) in Holsteins than in Angus. However, a breed influence on the accretion rate of chemical fat was detected only among bulls, where Angus had a more rapid accretion rate. Feeding animals at two energy levels resulted in different accretion rates relative to the empty body. In the Angus breed, regardless of sex, the accretion rates of water, protein and ash were more rapid (P < .05) in the low intake group, whereas the accretion rate of chemical fat was slower (P < .05). Among Holsteins, the low energy intake level had a less definite effect; for bulls, the accretion rates of water and chemical fat were more rapid (P < .05) and slower (P < .05), respectively; for steers, and accretion rate of protein was more rapid (P < .05), and for heifers, none of the accretion rates was altered.
79 citations
57 citations
TL;DR: In this paper, the carcass composition of Hereford × Friesian (HE), Friesians (FR) and Charolais × Fryian (CH) steers was examined in a 3 × 2 × 3 (no. = 9) factorial experiment.
Abstract: The carcass composition of Hereford × Friesian (HE), Friesian (FR) and Charolais × Friesian (CH) steers finished on diets of high (H) and medium (M) dietary metabolizable energy (ME) concentrations and slaughtered at low (L), normal (N) and heavy (W) carcass weights was examined in a 3 × 2 × 3 (no. = 9 per individual treatment) factorial experiment. A pre-finishing slaughter group of nine animals of each breed type was also included, giving a total 189 animals in 21 experimental groups. ME concentrations of the H and M diets which were offered ad libitum were 12·6 and 10·4 MJ/kg dry matter. Target carcass weights for L, N and W were 260, 300 and 340 kg for HE and FR and 260, 320 and 380 kg for CH.Carcass side weights (before tissue separation) of the HE, FR and CH pre-finishing slaughter groups were 90·8, 970 and 101·0 (s.e.d. 3·9) kg. Corresponding tissue proportions were 188, 199 and 200 (s.e.d. 4·3) g/kg bone, 663, 686 and 690 (s.e.d. 5·3) g/kg muscle and 135, 99 and 96 (s.e.d. 5·7) g/kg fat. Main effect side weights of the finished groups were 152·3, 151·4 and 162·2 (s.e.d. 1·4) kg for HE, FR and CH. 158·5 and 152·2 (s.e.d. 1·1) kg for H and M and 131·2, 155·2 and 179·6 (s.e.d. 1·4) kg for L, N and W, respectively. Tissue proportions in the same order were 146, 160 and 157 (s.e.d. 2·0), 149 and 159 (s.e.d. 1·6) and 163, 154 and 146 (s.e.d. 2·0) g/kg bone, 579, 601 and 635 (s.e.d. 5·5), 600 and 610 (s.e.d. 4·5) and 637, 599 and 574 (s.e.d. 5·5) g/kg muscle and 264, 228 and 195 (s.e.d. 6·4), 240 and 219 (s.e.d. 5·2) and 188, 235 and 264 (s.e.d. 6·4) g/kg fat. CH had more (P 1·0 for the thorax, ribs, flank and fat. The regression coefficients for the main muscles of the pelvic limb and loin and total thoracic limb muscle on total side muscle were 1·0. Similarly the regression coefficients for the bones of the two limbs on total side bone were 10. It was calculated (for the H diet) that at a carcass weight of 300 kg, HE, FR and CH would have carcass tissue proportions of 576, 600 and 642 g/kg muscle and 261, 227 and 180 g/kg fat. The three breed types would have similar carcass fat contents at carcass weights of 264, 300 and 376 kg for HE, FR and CH, respectively.
52 citations
TL;DR: Although steers consuming the lowest level of feed made gains containing a lower percentage of fat and a higher percentage of protein than steers at higher intakes, body composition within a breed was not altered by level of energy intake when animals, within breeds, were slaughtered at similar end weights.
Abstract: Hereford and Charolais steers were fed at three levels of feed intake (low, medium or ad libitum) to similar weights within breed groups to evaluate effects of energy intake on energetic efficiency and body composition. Two methods were employed to partition metabolizable energy intake into use for maintenance and gain. Method one used an assumed daily fasting heat production of 77 kcal/weight (W).75; method two estimated fasting heat production from the regression of log daily heat production against metabolizable energy intake (kcal/W.75). Net energy for gain (NEg) was determined in method one by regressing retained energy (kcal/W.75) against feed intake (g/W.75). For method two, the estimated maintenance requirement of feed was subtracted from total feed intake and retained energy was regressed against feed intake above maintenance to estimate NEg. Conclusions regarding feed energy utilization for maintenance and gain were the same by either method of energy partitioning. Charolais steers used feed energy less efficiently for gain than Hereford steers, and ad libitum steers used feed energy less efficiently for gain than steers at lower intakes (P less than .05). Charolais steers made leaner (P less than .05) gains than Hereford steers. Although steers consuming the lowest level of feed made gains containing a lower percentage of fat and a higher percentage of protein (P less than .05) than steers at higher intakes, body composition within a breed was not altered by level of energy intake when animals, within breeds, were slaughtered at similar end weights.
46 citations