Effects of feeding level on efficiency of high- and low-residual feed intake beef steers

Abstract Comparing heat production after ad libitum (ADLIB) and restricted (RESTRICT) feeding periods may offer insight into how residual feed intake (RFI) groups change their energy requirements based on previous feeding levels. In this study, the authors sought to explain the efficiency changes of high- and low-RFI steers after feed restriction. To determine RFI classification, 56 Angus-cross steers with initial body weight (BW) of 350 ± 28.7 kg were individually housed, offered ad libitum access to a total mixed ration, and daily intakes were recorded for 56 d. RFI was defined as the residual of the regression of dry matter intake on mid-test BW0.75 and average daily gain. High- and low-RFI groups were defined as >0.5 SD above or below the mean of zero, respectively. Fourteen steers from each high and low groups (n = 28) were selected for the subsequent 56-d RESTRICT period. During the RESTRICT period, intake was restricted to 75% of previous ad libitum intake on a BW0.75 basis, and all other conditions remained constant. After the RESTRICT period, both RFI groups had decreased maintenance energy requirements. However, the low-RFI group decreased maintenance energy requirements by 32% on a BW0.75 basis, more (P < 0.05) than the high-RFI group decreased maintenance requirements (18%). Thus, the low-RFI steers remained more efficient after a period of feed restriction. We conclude that feed restriction decreases maintenance energy requirement in both high- and low-RFI groups that are restricted to the same degree.

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Influence of timing and duration of feed restriction on growth and economic performance of finisher broiler chickens

African Journal of Food, Agriculture, Nutrition and Development ◽

10.18697/ajfand.55.11650 ◽

2012 ◽

Vol 12 (55) ◽

pp. 6976-6986

Author(s):

OA Makinde ◽

Keyword(s):

Feed Intake ◽

Crude Protein ◽

Average Daily Gain ◽

Live Weight ◽

Feed Restriction ◽

Meat Production ◽

Feed Conversion ◽

Final Body Weight ◽

Ad Libitum ◽

Cost Of Production

The study investigated different feed restriction programs during an 8-week broiler chicken growing cycle as a management strategy for reducing cost of production. Initially, 90 Hubbard day-old chicks fed ad libitum a commercial starter feed supplying 24% crude protein and 3000 kcal of ME/kg for 4 weeks. Thereafter, they were randomly allotted to five different feed restriction programs (R0, R5, R56, R67 and R57) utilizing finisher diets supplying 19% crude protein and 2850 kcal of ME/kg from 5-8 weeks. Each program had three replicates and six birds per replicate. Unrestricted (R0) was the control where birds fed ad libitum. In R5, birds were restricted the 5th week; R56, 5th and 6th weeks; R67, 6th and 7th weeks, and R57, 5th and 7th weeks. However, all the feed-restricted birds fed ad libitum in the 8th week. Feed restriction involved feeding one-third feed intake of R0 birds starting from 14.00 to 18.00 h daily and performance parameters recorded. Feed restriction negatively affected growth performance as the severity of restriction increased. Final body weight, carcass weight, average daily gain and average daily feed intake were similar (P>0.05) for R0 and R5 but higher than R56, R67 and R57. However, feed restriction did not significantly affect (P>0.05) carcass and breast yields or feed conversion ratio except for R67, the least (P<0.05) feed efficient. Feed cost, cost of production and revenue declined as the period of restriction increased. However, profit or profit/kg live weight, economic efficiency (EE) of feed and relative EE of feed were highest for R0 followed by R5, R56, R57 and R67 in that order. Generally, birds restricted for 1 week performed better than those restricted for 2 weeks and birds restricted continuously for 2 weeks before the last week of re-alimentation and slaughter were inferior to others. These results suggest that the duration and timing of feed restriction can reduce cost in broiler meat production without seriously affecting performance or economics of production depending on the restriction program applied.

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Running Head: Heat Affects Cholesterol and Bile Acid Alterations in Cholesterol and Bile Acids Metabolism in Large White Pigs during Short-Term Heat Exposure

Animals ◽

10.3390/ani10020359 ◽

2020 ◽

Vol 10 (2) ◽

pp. 359 ◽

Cited By ~ 1

Author(s):

Wei Fang ◽

Xiaobin Wen ◽

Qingshi Meng ◽

Lei Liu ◽

Jingjing Xie ◽

...

Keyword(s):

Heat Stress ◽

Bile Acid ◽

Bile Acids ◽

Feed Intake ◽

Average Daily Gain ◽

Growing Pigs ◽

Short Term ◽

Large White ◽

Ad Libitum ◽

Ad Libitum Intake

Heat stress influences lipid metabolism independently of nutrient intake. It is not well understood how cholesterol and bile acid (BA) metabolism are affected by heat stress. To investigate the alterations of cholesterol and bile acids when pigs are exposed to short term heat stress, 24 Large White pigs (63.2 ± 9.5 kg body weight, BW) were distributed into one of three environmental treatments: control conditions (CON, 23 °C with ad libitum intake; n = 8), heat stress conditions (HS, 33 °C with ad libitum intake; n = 8), or pair-fed conditions (PF, 23 °C with the same amount to the feed consumed by the HS; n = 8) for three days. Compared with CON pigs, HS pigs reduced the average daily feed intake and average daily gain by 55% and 124%, respectively, and significantly increased rectal temperatures by 0.9 °C and respiration rates more than three-fold. The serum total cholesterol (TC), low-density lipoprotein-cholesterol, and triglycerides (TG) increased (p < 0.05), while hepatic TC, TG, and mRNA of 3-hydroxy-3-methylglutaryl-CoA reductase were reduced on day 3. Furthermore, liver taurine-conjugated BAs (TCBAs), including taurolithocholic acid, taurochenodeoxycholic acid (TCDCA), tauroursodeoxycholic acid, taurohyodeoxycholic acid, and taurocholic acid were elevated in HS pigs compared to CON and PF pigs (p < 0.05), and the level of chenodeoxycholic acid was more significant in the PF group than in the CON and HS groups. The concentration of ursodeoxycholic acid in the serum was higher in HS pigs than CON and PF pigs (p < 0.05), and TCDCA was increased in HS pigs compared with PF pigs (p < 0.05). Altogether, short-term HS reduced hepatic cholesterol levels by decreasing cholesterol synthesis, promoting cholesterol to TCBAs conversion, and cholesterol release to serum in growing pigs. This independently reduced feed intake might serve as a mechanism to protect cells from damage during the early period.

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EFFECT OF REDUCED FEED INTAKE ON ZEARALENONE METABOLISM AND TOXICITY IN THE RAT

Canadian Journal of Animal Science ◽

10.4141/cjas87-052 ◽

1987 ◽

Vol 67 (2) ◽

pp. 535-542 ◽

Cited By ~ 6

Author(s):

M. C. KIRITSY ◽

M. J. LATTA ◽

D. W. FITZPATRICK

Keyword(s):

Feed Intake ◽

Young Female ◽

Female Rats ◽

Feed Restriction ◽

Standard Diet ◽

Uridine Diphosphate ◽

Metabolizing Enzymes ◽

Ad Libitum ◽

Ad Libitum Intake ◽

Conjugated Metabolites

Three experiments were conducted to determine the effect of reduced feed intake on the metabolism and toxic expression of zearalenone. Young female rats were fed a standard diet either ad libitum or 75% of ad libitum intake. The enzyme activities of 3α-hydroxysteroid dehydrogenase (3α-HSD) and uridine diphosphate glucuronyl transferase (UDP-G), the zearalenone metabolizing enzymes, were determined after 14 d of feeding. When feed was restricted, 3α-HSD activity increased 28% while UDP-G activity increased 79% compared to fed controls. After 14 d of feeding, animals were orally dosed with 1 mg zearalenone kg−1 body weight; zearalenone and its metabolites were measured in urine and feces. Feed restriction resulted in more conjugated zearalenone being excreted in the urine, with a corresponding decrease in α- and β-zearalenols produced and fecal metabolites compared to fed animals. No conjugated metabolites were found in the feces. Animals were fed the same diet, but 0–150 ppm zearalenone were added for 3 wk and growth and organ weights were determined. Feed restriction ameliorated zearalenone's toxic expression. These results indicate that nutritional regimen effects zearalenone metabolism, excretion and toxicity. Key words: Mycotoxin, zearalenone, feed intake, toxicity

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Enteric methane emissions from growing beef cattle as affected by diet and level of intake

Canadian Journal of Animal Science ◽

10.4141/a06-021 ◽

2006 ◽

Vol 86 (3) ◽

pp. 401-408 ◽

Cited By ~ 37

Author(s):

Karen A Beauchemin ◽

Sean M McGinn

Keyword(s):

Feed Intake ◽

Methane Emissions ◽

Feedlot Cattle ◽

Energy Requirements ◽

Maintenance Energy ◽

Final Body Weight ◽

Greenhouse Gasses ◽

Enteric Methane ◽

Ad Libitum ◽

Barley Silage

A study was conducted to determine whether enteric methane (CH4) emissions from growing feedlot cattle fed backgrounding diets based on barley silage could be reduced through grain supplementation. A second objective was to determine the effects of feed intake on CH4 emissions. Eight Angus beef heifers (initial and final body weight, 328 ± 28 and 430 ± 29 kg) were used. The experiment was designed as a split-plot crossover with two diets and two 8-week periods. The main plot was the diet [dry matter (DM) basis]: high forage (70% barley silage, 30% barley-based concentrate) or high grain (30% barley silage, 70% corn-based concentrate). The sub-plot was the feeding level: unrestricted (ad libitum feed intake, 5% orts) or restricted (65% of ad libitum intake) feed intake. Methane emissions were measured during each sub-plot over 3 d using whole animal chambers. Changing the forage to concentrate ratio and substituting barley for corn did not affect CH4 emissions (141.5 g d-1; P = 0.26), and the average emission was about 10% higher than the emission calculated using the International Panel on Climate Change (IPCC) Tier 1 approach. Methane conversion rate was also similar for both diets [6.23% of gross energy intake (GEI), P = 0.29], and was similar to the value of 6.0 used in the IPCC Tier 2 approach to calculating CH4 emissions from cattle. Restricting intake reduced CH4 emissions (169 vs. 114 g d-1; P < 0.002), with the reduction in CH4 proportional to the decline in intake. Level of intake relative to maintenance energy requirements was moderately inversely related (r = -0.30; P = 0.04) to CH4 (% GEI). The proportion of GEI lost as CH4 declined by 0.77 percentage units per unit increase in level of intake above maintenance. This study shows that supplementing barley-silage-based diets with corn grain to increase diet quality has only small effects on reducing CH4 emissions. In contrast, maximizing feed intake above maintenance energy requirements increases daily CH4 emissions, but improves efficiency of CH4 conversion because CH4, as a percentage of GEI, declined. Thus, feeding cattle for maximum gain is an important CH4 mitigation strategy for the cattle industry as it reduces the proportion of feed energy lost as CH4 each day, as well as, reduces the number of days to market and associated CH4 production. Key words: Cattle, methane, greenhouse gasses

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Animals selected for postweaning weight gain rate have similar maintenance energy requirements regardless of their residual feed intake classification

Journal of Animal Science ◽

10.1093/jas/skab067 ◽

2021 ◽

Author(s):

Camila Delveaux Araujo Batalha ◽

Luís Orlindo Tedeschi ◽

Fabiana Lana de Araújo ◽

Renata Helena Branco ◽

Joslaine Noely dos Santos Gonçalves Cyrillo ◽

...

Keyword(s):

Body Composition ◽

Body Weight ◽

Weight Gain ◽

Feed Intake ◽

Body Weight Gain ◽

Energy Requirement ◽

Residual Feed Intake ◽

Breeding Program ◽

Energy Requirements ◽

Net Energy

Abstract Data of comparative slaughter were used to determine Nellore bulls' net energy requirements classified as efficient or inefficient according to residual feed intake (RFI) and selection lines (SL). Sixty-seven Nellore bulls from the selected (SE) and control (CO) lines of the selection program for postweaning weight gain were used. The animals underwent digestibility trials before being submitted to the finishing trial. Sixteen bulls were slaughtered at the beginning of the finishing trial, and their body composition were used as the baseline for the remaining animals. For body composition determinations, whole empty body components were weighed, ground, and subsampled for chemical analyses. Initial body composition was determined with equations developed from the baseline group using shrunk body weight, fat, and protein. The low RFI (LRFI) and CO animals had a lower dry matter (DMI) and nutrient intake (P < 0.05) than high RFI (HRFI) and SE animals, without alterations in digestibility coefficients (P > 0.05). During the finishing trial, DMI remained lower for LRFI and CO animals. Growth performance was similar between RFI classes, except for empty body weight gain that tended to be higher for LRFI than HRFI (P = 0.091). The SE animals had less fat content on the empty body (P = 0.005) than CO. Carcasses tended to be leaner for LRFI than HRFI (P = 0.080) and for SE than CO (P = 0.066) animals. LRFI animals retained more energy (P = 0.049) and had lower heat production (HP; P = 0.033) than the HRFI ones. Retained energy was not influenced by SL (P = 0.165), but HP tended to be higher for SE when compared to CO (P = 0.075) animals. Net energy requirement for maintenance (NEm) was lower for LRFI than HRFI (P = 0.009), and higher for SE than CO (P = 0.046) animals. There was an interaction tendency between RFI and SL (P = 0.063), suggesting that NEm was lower for LRFI+CO than HRFI+CO (P = 0.006), with no differences for SE (P = 0.527) animals. The efficiency of ME utilization for maintenance (km) of LRFI and HRFI animals were 62.6 and 58.4%, respectively, and for SE and CO were 59.0 and 62.1%, respectively. The breeding program for postweaning weight has not improved feed efficiency over the years, with RFI classification not being a promising selection tool for SE animals. Classification based on RFI seems to be useful in animals that have not undergone the breeding program, with LRFI animals having lower energy requirements than the HRFI ones.

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Metabolic and endocrine responses to cold and feed restriction in ruminants

Canadian Journal of Animal Science ◽

10.4141/a99-028 ◽

2000 ◽

Vol 80 (1) ◽

pp. 87-95 ◽

Cited By ~ 19

Author(s):

E. D. Ekpe ◽

R. J. Christopherson

Keyword(s):

Rectal Temperature ◽

Cold Exposure ◽

Feed Intake ◽

Average Daily Gain ◽

Feed Restriction ◽

Plasma Insulin Concentration ◽

Treatment Groups ◽

Cold Environments ◽

Warm Environment ◽

Ad Libitum

Twenty-four wether lambs were assigned to different temperature and feeding levels to assess their metabolic and endocrine profiles and to test the hypothesis that energy conservation responses of sheep to feed restriction occur in warm but not cold environments. Lambs were kept in warm (W; 23 ± 2 °C) or cold (C; 0 ± 2 °C) environments and received either an ad libitum (A) or a restricted (1.35 × maintenance) (R) level of feed intake, thus creating four treatment groups (WA, WR, CA and CR). Average daily gain (ADG), feed intake, metabolic rates, rectal temperature, and plasma levels of insulin, thyroxine (T4), triiodothyronine (T3) and cortisol were recorded during three periods of 5 wk each. The ADG was lower (P < 0.001) in feed-restricted groups. Cold exposure reduced the ADG along with feed efficiency in the first period (P < 0.01). Metabolic rate was lowered by feed restriction (P < 0.01) in periods 1 and 3, but was increased by cold exposure in ad libitum-fed sheep during period 1 (P < 0.05). Both cold exposure and feed restriction lowered rectal temperature (P < 0.001). Plasma insulin concentration was lowered by feed restriction (P < 0.05) and was increased (P < 0.05) by cold exposure during periods 2 and 3. Plasma T3 concentration was reduced (P < 0.05) by feed restriction and was increased by cold exposure during periods 1 and 2. Plasma T4 level remained unaltered (P > 0.05) while plasma cortisol concentration was increased by both cold exposure and feed restriction (P < 0.01). The results indicate that lambs show metabolic and physiological responses to feed restriction, which conserve energy in a cold as well as a warm environment. Key words: Sheep, hormone, cold-exposure, feed-restriction.

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Feed Restriction Modifies Intestinal Microbiota-Host Mucosal Networking in Chickens Divergent in Residual Feed Intake

mSystems ◽

10.1128/msystems.00261-18 ◽

2019 ◽

Vol 4 (1) ◽

pp. e00261-18 ◽

Cited By ~ 7

Author(s):

Barbara U. Metzler-Zebeli ◽

Sina-Catherine Siegerstetter ◽

Elizabeth Magowan ◽

Peadar G. Lawlor ◽

Renée M. Petri ◽

...

Keyword(s):

Fatty Acids ◽

Intestinal Microbiota ◽

Feed Intake ◽

Barrier Function ◽

Residual Feed Intake ◽

Short Chain Fatty Acids ◽

Short Chain ◽

Feed Restriction ◽

Physiological Adaptations ◽

Ad Libitum

ABSTRACT Differences in chickens’ feed intake may be the underlying factor influencing feed-efficiency (FE)-associated variation in intestinal microbiota and physiology. In chickens eating the same amount of feed, quantitative feed restriction may create similar intestinal conditions and help clarify this cause-and-effect relationship. This study investigated the effect of ad libitum versus restrictive feeding (85% of ad libitum) on ileal and cecal microbiota, concentrations of short-chain fatty acids, visceral organ size, intestinal morphology, permeability, and expression of genes related to nutrient uptake, barrier function, and innate immune response in broiler chickens with divergent residual feed intake (RFI; metric for FE). On day 30 posthatch, 28 low-RFI (good FE) and 29 high-RFI (poor FE) chickens across both feeding-level groups (n = 112) were selected. Supervised multigroup data integration and relevance network analyses showed that especially Lactobacillus (negative) in ileal digesta, Turicibacter (positive) in cecal digesta, and Enterobacteriaceae (positive) in both intestinal segments depended on chicken’s feed intake, whereas the level of Anaerotruncus in cecal digesta was most discriminative for high RFI. Moreover, shallower crypts and fewer goblet cells in ceca indicated host-related energy-saving mechanisms with low RFI, whereas greater tissue resistance suggested a stronger jejunal barrier function in low-RFI chickens. Values corresponding to feed intake level × RFI interactions indicated larger pancreas and lower levels of ileal and cecal short-chain fatty acids in restrictively fed high-RFI chickens than in the other 3 groups, suggesting host physiological adaptations to support greater energy and nutrient needs of high-RFI chickens compensating for the restricted feeding. IMPORTANCE The impact of the FE-associated differences in feed intake on intestinal bacterial and host physiological parameters has so far not been clarified. Understanding the underlying principles is essential for the development of cost-effective strategies to improve FE in chicken production. Under conditions of quantitative feed restriction, low- and high-RFI chickens ate the same amount of feed. Therefore, this research helps in distinguishing intestinal bacterial taxa and functions that were highly reliant on feed intake from those that were associated with physiological adaptations to RFI-associated differences in host nutritional needs and intestinal nutrient availability. This work provides a background for further research to assess manipulation of the intestinal microbiota, host physiology, and FE in chickens by dietary intervention.

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Modelling the relation between energy intake and protein and lipid deposition in growing pigs

Animal Science ◽

10.1017/s1357729800054941 ◽

2000 ◽

Vol 71 (1) ◽

pp. 119-130 ◽

Cited By ~ 32

Author(s):

J. van Milgen ◽

N. Quiniou ◽

J. Noblet

Keyword(s):

Energy Requirement ◽

Growing Pigs ◽

The Other ◽

Maintenance Energy ◽

Lipid Deposition ◽

Large White ◽

Protein Deposition ◽

Ad Libitum ◽

Maintenance Energy Requirement ◽

Ad Libitum Intake

AbstractWhen modelling the effect of a changing nutrient supply to growing animals, it is important to distinguish the individual response curve of an animal from the change in this response that may occur during growth. A data analysis model is proposed where, for an individual animal, the relation between protein deposition (PD) and metabolizable energy (ME) intake above maintenance (MEp) is curvilinear, so that PD intersects the origin and reaches its maximum at the maximum protein deposition rate (PDmax). An increase of MEp beyond that required to attain PDmax would not change PD. The MEp not used for protein synthesis can be used for lipid deposition (LD). The relation between PD and LD on the one hand and ME on the other hand can then be described as a function of the maintenance energy requirement (MEm), PDmax, the level of ME required to attain PDmax (F; as a multiple of MEm) and the energetic efficiencies of PD (kp) and LD (kf). Of these statistics, only kp and kf were assumed to be independent of body weight (BW), age or genotype. Variation in PDmax was described as a Gompertz function (of age) whereas variation in F was assumed a linear function of BW. Maintenance energy requirement was expressed as a power function of BW. To evaluate the model, 145 nitrogen and energy (indirect calorimetry) balances were obtained from three types of pigs (Large White castrated males (cLW) and Piétrain × Large White castrated males (cPP× ) and males (bPP×)) ranging in BW between 45 and 100 kg and housed under thermoneutral conditions. Animals were allotted to one of four energy levels ranging from 0·70 to 1·00 of ad libitum intake. The MEm was not different between genotypes (849 kJ/kg BW0·60) whereas the kp and kf were 0·56 and 0·75, respectively. For castrated animals on ad libitum intake, PDmax started limiting PD at approximately 130 days of age (78 and 86 kg BW for cLW and cPP×, respectively). Before this age and for bPP×, PD was limited by MEp. In bPP×, the difference between PD and PDmax was small (less than proportionately 0·05). The F did not change with BW for bPP× (2·85 × MEm) whereas for the other genotypes, it decreased linearly from 4·47 at 45 kg to 2·00 at 100 kg of BW. Due to its nature, the model allows estimation of PDmax even when energy is restricting PD.

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Determination of Maintenance Energy Requirements for Fattening Castrated Korean Black Goats (Capra hircus coreanae)

Animals ◽

10.3390/ani11061543 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1543

Author(s):

Sang-Ho Moon ◽

Yeong Sik Yun ◽

Na Yeon Kim ◽

Sanguk Chung ◽

Qi Man Zhang ◽

...

Keyword(s):

Body Weight ◽

Energy Intake ◽

Energy Levels ◽

Average Daily Gain ◽

Nutrient Digestibility ◽

Metabolic Energy ◽

Energy Requirements ◽

Capra Hircus ◽

Maintenance Energy ◽

Daily Gain

Twelve adult (10 months old) castrated Korean black goats, with an average initial body weight of 24.98 ± 3.7 kg, were used in this experiment to determine their maintenance energy requirements. Dry matter intakes (g/d, p = 0.945) were not affected by energy levels, but metabolic energy intake (kcal/d, p < 0.002) and average daily gain (g/d, p < 0.001) were significantly increased at higher energy levels. Nutrient digestibility was similar in the treatments, but crude fat digestibility increased with the addition of protective fat powder (p = 0.001). The energy required for fattening the castrated Korean black goats was estimated using the correlation between metabolic energy intake per dietary body weight and average daily gain per dietary body weight. The Y-axis intercept value was calculated to be 108.76 kcal/kg BW0.75 (p < 0.05, r2 = 0.6036), which was the metabolic energy requirement for maintaining the lives of the fattening Korean black goats. The estimated energy requirements of the black goat can improve specification techniques, such as the energy level and the amount of feed supply required for domestic black goats.

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PSXI-6 Calculating energy efficiency use for Nellore bulls divergent in residual feed intake

Journal of Animal Science ◽

10.1093/jas/skaa278.692 ◽

2020 ◽

Vol 98 (Supplement_4) ◽

pp. 393-394

Author(s):

Camila D A Batalha ◽

Fabiana L De Araújo ◽

Renata H Branco ◽

Luis O Tedeschi ◽

Sarah F Bonilha

Keyword(s):

Energy Efficiency ◽

Feed Intake ◽

Subcutaneous Fat ◽

Residual Feed Intake ◽

Efficiency Index ◽

Least Square ◽

Metabolic Energy ◽

Energetic Efficiency ◽

Base Line ◽

Ad Libitum

Abstract Retained energy (RE) and energetic efficiency index were measured in Nellore bulls from divergent classes of residual feed intake (RFI). Thirty-four Nellore bulls (15 low RFI-LRFI and 19 high RFI-HRFI) were feedlot finished and slaughtered with 385 ± 40 kg of body weight (BW) and 520 ± 26.2 days of age. At the beginning of the experiment, five LRFI and three HRFI were slaughtered and used as base line. Individual dry matter intake was recorded daily; initial and final BW were recorded after 16 h of fasting. Eight bulls, four LRFI and four HRFI, were fed at maintenance, receiving 65 g of DM/kg0.75 BW, and 18 bulls (10 LRFI and eight HRFI) were fed ad libitum. Diet had 19:81 roughage:concentrate, 88% of DM and 15% of crude protein. Ultrasound measurements on the Longissimus muscle were performed at intervals of 28 days. When two ad libitum bulls reached 4 mm of subcutaneous fat thickness, one maintenance bull was randomly chosen and slaughtered on the same day. After slaughter, the centesimal composition of the empty body and carcass was measured. Data were analyzed using a random coefficients model, and RFI class was included as a fixed effect. Least-square means were used to compare the means, and significance was declared for P ≤ 0.05. The LRFI had greater protein retention than HRFI (248 vs. 142 g/d; P = 0.009), and same fat and energy retention (313 g/d and 4.12 Mcal/d, respectively). The energy efficiency indexes, heat production per metabolic energy intake (Mcal/Mcal) and gain-to-feed (kg/kg) ratio, did not differ between RFI classes. Though LRFI had the same energy efficiency index, they were leaner. These results indicated an association of RFI and maturity patterns. Further research is needed to estimate the net energy requirements of Nellore bulls classified according to RFI. Acknowledgments: FAPESP Processes 2017/06709-2, 2018/20080–2 and 2019/17714-2.

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