Mechanisms of reduced and compensatory growth.

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.

Compensatory growth and carcass quality in growth-restricted and refed beef steers.

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.

Physical and chemical components of the empty body during compensatory growth in beef steers.

Relating long-term rainfall variability to cattle population dynamics in communal rangelands and a government ranch in southern Ethiopia

The role of thermodynamics in controlling rumen metabolism simple allometric models to predict rumen feed passage rate in deomstic ruminants modelling production and portal appearance of volatile fatty acids in cows modelling energy expenditure in pigs simulation of the development of adipose tissue in beef cattle modelling nutrient digestion and utlization in dairy cows fed tropical forages - the validation test a pig model for feed evaluation.

Modelling Nutrient Utilization in Farm Animals

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.

Compensatory growth in sheep and cattle. 1. Growth pattern and feed intake

Compensatory growth can be due to increased protein deposition, reduced maintenance and greater feed intake. However, the contribution to and interaction between these mechanisms during compensatory growth is not clear. It was hypothesized that initial compensatory growth was due to reduced maintenance requirement and greater deposition of protein, after which compensatory growth was due to greater feed intake. Changes in the composition of sheep and cattle were measured during nutritional restriction and subsequent compensatory growth, and compared with the changes in control animals fed ad libitum throughout. At the end of the experiment the restricted cattle had compensated completely, and there was no difference in the body composition of the restricted and the control cattle. The restricted sheep did not compensate completely and were leaner than the control sheep. During nutritional restriction there was differential weight loss of carcase tissues in both the sheep and the cattle. The greatest losses were in the liver and the digestive tract in both species and in the skin of the sheep. It was concluded that the loss of these tissues reduced the maintenance requirement of the restricted animals and that the lowered maintenance requirement persisted during re-alimentation until these tissues had been fully repleted. Further, the repletion of these tissues required an increase in protein deposition, and it was a combination of these two mechanisms that was responsible for compensatory growth during the first 12 weeks of re-alimentation.

IH Williams

Papers

Compensatory growth in sheep and cattle. 1. Growth pattern and feed intake

Compensatory growth in sheep and cattle. II. Changes in body composition and tissue weights