With feed costs representing on average 65% of the total cost of production improvements in feed efficiency could have a major impact on the beef industry. Postweaning performance and feed efficiency data were collected on 114 heifers born on the University of Arizona's V bar V Ranch. Residual feed intake (RFI) was significantly correlated with dry matter intake (DMI) (r = 0.46) and G:F (r = -0.43), while G:F was moderately correlated with initial age (r = -0.54), initial body weight (r = -0.40), and average daily gain (ADG) (r = 0.68). Residual gain (RG) was moderately correlated with RFI (r = -0.41) and highly correlated with ADG (0.62) and G:F (0.73). In addition, RG was significantly correlated (r = -0.21) with initial weight suggesting that selection for RG could lead to increased cow mature size. Heifers were sorted into three breed categories: Hereford, Hereford cross, and Wagyu cross and breed effect on performance and feed efficiency traits were analyzed. Significant differences in DMI, FCR, and RG were noted, but likely due to significant differences in age at the time of testing. RFI was not significantly different between breed groups, suggesting that RFI is less influenced by animal age than other measures of feed efficiency. In addition, sires of study heifers with 5 or more progeny were selected and progeny performance and feed efficiency traits were compared between sires. No significant differences in ADG, RFI, FCR, or RG were noted between sire progeny. This was likely due to an insufficient number of progeny used in the trial. Further research and an increased number of animals used may uncover significant impacts of sire on RFI.

Ontario cage culture operations produce the majority of farmed rainbow trout in Canada, using a diverse range of management practices that are expected to result in substantial variation in trout performance across the industry. A preliminary survey of performance data was undertaken, resulting in data from 5 commercial sites between 2008 and 2012. Commercial performance was somewhat poorer than expected, particularly for mortality rates, thermal-unit growth coefficients, and economic feed conversion ratios (average weighted values of 12%, 0.165, and 1.36, respectively). Substantial variability in all performance parameters within and across operations suggests that continued production monitoring and benchmarking could be highly valuable for improving the economic sustainability of the sector. For future benchmarking efforts to be effective, improvement and standardization of data collection methods is needed. As such, a number of recommendations are provided to the industry for the refinement and standardization of performance recording protocols used by Ontario producers.

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Submitted by VIVIANE ENDO null (endo_vica@hotmail.com) on 2016-03-09T19:43:01Z No. of bitstreams: 1 Tese_Viviane_Endo.pdf: 2381814 bytes, checksum: 1717fe0a2a655707a2aa6da8a9f8467a (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-03-10T19:32:22Z (GMT) No. of bitstreams: 1 endo_v_dr_jabo.pdf: 2381814 bytes, checksum: 1717fe0a2a655707a2aa6da8a9f8467a (MD5) / Made available in DSpace on 2016-03-10T19:32:22Z (GMT). No. of bitstreams: 1 endo_v_dr_jabo.pdf: 2381814 bytes, checksum: 1717fe0a2a655707a2aa6da8a9f8467a (MD5) Previous issue date: 2016-02-16 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A cana-de-açúcar tem papel importante no agronegócio brasileiro para a produção de etanol e açúcar. A palha da cana-de-açúcar é um resíduo orgânico pobre em sacarose para produção de etanol e de baixo valor nutritivo para a alimentação animal. Devido a isso, o processo de queima dos canaviais ocorre em larga escala com intuito de facilitar a colheita da cana-de-açúcar, além de limpar o canavial para a próxima safra. Entretanto, a queima causa danos à saúde e impacto ambiental. No estudo foram avaliados dois fatores da cana-de-açúcar: a influência da palha e a influência dos tempos de preparo da calda de hidróxido de cálcio (Ca(OH)2) antes da hidrólise da cana-de-açúcar. Os parâmetros avaliados neste estudo foram: composição bromatológica, temperatura e pH da cana-de-açúcar, digestibilidade de nutrientes, desempenho de vacas leiteiras e uso de imagens de microscopia eletrônica de varredura (MEV) da cana-de-açúcar antes e após a digestão in vitro. O primeiro estudo foi um arranjo fatorial 2 x 5 [cana-de-açúcar com ou sem palha e cinco tempos de preparo da calda de Ca(OH)2 antes da hidrólise da cana-de-açúcar (72, 48, 24, 0,5 horas e sem preparo)]. No segundo estudo foi avaliado a digestibilidade in vitro dos nutrientes em um delineamento inteiramente casualizado, com cinco tratamentos: cana-de-açúcar fresca sem palha, HPT0,5 (cana-de-açúcar hidrolisada com palha e a calda preparada 0,5 horas antes da hidrólise), HPT72 (cana-de-açúcar hidrolisada com palha e a calda preparada 72 horas antes da hidrólise), HT0,5 e HT72, cana-de-açúcar hidrolisada sem palha usando os mesmos procedimentos de preparo da calda na cana-de-açúcar com palha. Posteriormente, utilizou-se um delineamento em quadrado latino 5 x 5 (cinco vacas em lactação e cinco tratamentos) para estudo de desempenho. Imagens de MEV foram feitas como complemento para visualização da cana-de-açúcar com e sem digestão in vitro. Como resultados, a cana-de-açúcar fresca sem palha e hidrolisada com palha e a calda preparada 72 horas antes apresentou menor teor de fibra em detergente neutro (FDN). O pH da cana-de-açúcar hidrolisada, devido à presença do agente alcalinizante foi maior em comparação à cana-de-açúcar fresca independente da palha. A temperatura foi influenciada pela palha, apresentando-se maior quando esta estava presente. Em relação à digestibilidade dos nutrientes, a cana-de-açúcar hidrolisada com palha, quando comparada à hidrolisada sem palha, apresentou menor digestibilidade in vitro de matéria seca (MS) e maior digestibilidade in vitro da FDN. Para o desempenho das vacas, houve menor consumo de MS para a cana-de-açúcar com palha em comparação à cana-deaçúcar sem palha. A produção de leite manteve-se constante entre os tratamentos, assim como a sua composição. Nas imagens da MEV, algumas pequenas partículas de cana-de-açúcar que foram observadas nas amostras não digerida, após a digestão in vitro parecem ter sofrido alguma digestão. O que permaneceu foram partículas maiores, ou seja, partículas indigestíveis. A utilização da cana-de-açúcar com palha e a calda de Ca(OH)2 preparada 72 horas antes da hidrólise é recomendada devido à melhor eficiência alimentar das vacas, além de facilitar a mão-de-obra. / Sugarcane has an important role in agribusiness because of ethanol and sugar production. Straw of sugarcane is an organic residue, it has low nutritional value to animal feed and a poor sucrose content which is used to produce ethanol. Because of this, burning of the sugarcane is performed on a large scale aiming to facilitate the sugarcane harvest, besides cleaning the sugarcane fields for the next crop. Burning, however, is not safe for health and causes harmful environmental impact. The study evaluated two sugarcane factors: the influence of straw and the time of lime preparation on the sugarcane hydrolysis. The variables analyzed on this study were: chemical composition, temperature and pH of sugarcane, nutrient digestibility, performance of dairy cows and the use of scanning electron microscopy (SEM) images of sugarcane before and after in vitro digestion. First study was arranged as a factorial 2 x 5 [sugarcane with or without straw and five times of the lime preparation before hydrolysis of sugarcane (72, 48, 24, 0.5 hours and no lime used)]. The lime used was calcium hydroxide (Ca(OH)2. In the second study the in vitro digestibility of nutrients was evaluated and arranged as a completely randomized design with five treatments: fresh sugarcane without straw, HST0.5 (hydrolyzed sugarcane with straw and the lime prepared 0.5 hours before the hydrolysis), HST72 (hydrolyzed sugarcane with straw and the lime prepared 72 hours before the hydrolysis), HT0.5 (hydrolyzed sugarcane without straw and the lime prepared 0.5 hours before the hydrolysis) and HT72 (hydrolyzed sugarcane without straw and the lime prepared 72 hours before the hydrolysis). Posteriorly, a Latin square design 5 x 5 five lactating cows and five treatments was arranged for performance of dairy cows. As complement, SEM images of sugarcane before and after the in vitro digestion were done. As results, fresh sugarcane without straw and hydrolyzed with straw and the lime prepared 72 hours in advance presented lower neutral detergent fiber (NDF) content. The pH of hydrolyzed sugarcane was higher compared to fresh sugarcane, due to the presence of the alkalizing agent, regardless of straw. Temperature was higher when the straw was present. Regarding the digestibility of nutrients, sugarcane with straw showed lower in vitro digestibility of dry matter (DM) and higher in vitro digestibility of NDF compared with hydrolyzed sugarcane. For the cow’s performance, a lower DM intake was observed for sugarcane with straw compared with sugarcane without straw. Milk production was similar among treatments, as well as its composition. Providing sugarcane with straw and the lime of Ca(OH)2 prepared 72 hours before hydrolysis of sugarcane is recommended because it provided better feed efficiency to the cows. Additionally, it facilitates the labor. / CNPq: 151452/2012-1

A seleção de animais para consumo alimentar residual (RFI) está intrinsecamente associada com a diminuição do consumo matéria seca e é independente do ganho de peso corporal, selecionando animais de eficiência produtiva e econômica, além também de diminuir a emissão de gases de efeito estufa provinda do gado. Neste estudo, amostras de soro de 16 animais selecionados divergentemente para eficiência de alimentação foram coletadas antes do confinamento (dia -21) e avaliadas em uma abordagem metabolômica global, com o objetivo de usar análise diferencial, análise de co-expressão e enriquecimento funcional, identificando marcadores para eficiência de alimentação antes do confinamento. Um analito foi diferencialmente presente entre os animais de baixo e alto RFI. A análise WGCNA identificou 22 e 25 módulos no modo positivo e negativo, respectivamente e, 1 módulo de cada modo foi fortemente associado a RFI (r = 0,53, p-valor <0,05 e r = 0,52, p-valor <0,1 nos modos negativo e positivo, respectivamente). A análise de enriquecimento funcional predize 13 processos biológicos associados à eficiência alimentar, incluindo alterações no metabolismo de vitaminas lipossolúveis, inflamação, estresse oxidativo, metabolismo de aminoácidos e metabolismo de ácidos graxos. Esse trabalho evidencia a possibilidade de se identificar um biomarcador para eficiência alimentar e também sugerem que as diferenças nas respostas ao estresse oxidativo e nos processos inflamatórios já influenciam na variação da eficiência alimentar previamente ao confinamento. / Animal selection for residual feed intake (RFI) is intrinsically associated with decreased consumption of dry matter independent of body weight gain, selecting yielding increased production and economic efficiency but also decreasing the greenhouse gas emission of livestock. In this study, serum samples of 16 animals selected for divergent feed efficiency were collected prior to feedlot (day -21) and evaluated in an untargeted metabolomics approach, with the goal of using differential analysis, co-expression analysis and functional enrichment to identifier markers for feed efficiency prior to the feedlot. One feature was differentially accumulated between low and high RFI. WGCNA analysis identified 22 and 25 modules in positive and negative mode, respectively, of 1 module of each mode was strongly associated with RFI (r= 0.53, p-value <0.05 and r=0.52, p-value < 0.1 to negative and positive mode, respectively). Pathway enrichment analysis yielded 13 biological processes associated with feed efficiency including alterations in vitamins liposoluble metabolism, inflammation, oxidative stress, amino acid metabolism and fatty acid metabolism. Our findings suggest the possibility to identify a biomarker for feed efficiency and also discuss that differences in oxidative stress responses and inflammatory processes could explain the feed efficiency variation prior to feedlot.

Orientador: Flávio Dutra de Resende / Resumo: Objetivou-se com o presente trabalho avaliar o efeito da suplementação com gordura protegida contendo ácidos graxos saturados e insaturados, durante a recria em pastagens e na terminação em confinamento de tourinhos Nelore. O experimento foi desenvolvido no Polo Regional de Desenvolvimento Tecnológico dos Agronegócios da Alta Mogiana, em Colina – SP. Foram utilizados 124 tourinhos, com 8 meses de idade e peso corporal (PC) médio inicial de 190 kg ± 25,1, blocados por peso e avaliados durante a primavera, verão e outono em pastejo de lotação contínua com taxa de lotação variável (fase de recria), distribuídos ao acaso em dois tratamentos: 1) Controle - suplementação proteica-energética 3 g/kg de PC (sem gordura protegida); 2) Gordura Protegida - Suplementação proteica-energética 3 g/kg de PC com adição de ácidos graxos saturados e insaturados na forma protegida (Blend, Nutricorp, Araras, São Paulo, Brasil). Após a recria (270 dias), os animais com média de 20 meses e 420 kg, foram confinados em 12 baias, por 106 dias, e distribuídos entre 4 tratamentos: 1) CONT – CONT: Controle da recria sem a presença de gordura protegida no confinamento; 2) CONT - GORP: Controle da recria com a presença de gordura protegida no confinamento; 3)GORP – CONT: Gordura protegida da recria sem a presença de gordura protegida no confinamento e 4)GORP – GORP: Gordura protegida da recria com a presença de gordura protegida no confinamento. Para os parâmetros sanguíneos durante a fase da recria, foram ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to evaluate the effect of supplementation with protected fat containing saturated and unsaturated fatty acids in diet of Nellore cattle during growing phase on pasture and finishing phase in the feedlot. The experiment was carried out at the Regional Technological Development Center of the Agribusiness of Alta Mogiana (APTA), in Colina - SP. One hundred twenty-four young bulls were used (months old) with initial body weight (BW) of 190 kg ± 25.1. The animals were blocked by BW and evaluated during the spring, summer and autumn in grazing systems through growing phase, randomly distributed into two treatments (with or without protected fat): 1) Control - protein-energy supplementation 3 g/kg BW (without protected fat); 2) Protected Fat - Protein-energetic supplementation 3 g/kg BW with addition of saturated and unsaturated fatty acids in protected form (Blend, Nutricorp, Araras, São Paulo, Brazil). Following the growing phase (270 days), the animals with an average of 20 months and 420 kg were finished in feedlot (106 days), three replicates (totalizing 12 pens) within each treatment were randomly assigned to one of two treatments (with or without protected fat during finishing phase). The treatments diets were: 1) CON - CON: Control without protected fat in feedlot; 2) CON - FAT: Control during the growing phase with protected fat in feedlot; 3) FAT - CON: Protected fat during the growing phase without protected fat in feedlot and 4) FAT - FAT:... (Complete abstract click electronic access below) / Doutor

Estimating feed efficiency in grazing environments is challenging due to difficulties in quantifying food intakes and diet choices in free-grazing animals. The plant-wax marker technique may be a useful tool to redress this problem. However, its reliability needs to be validated before its wider application. This study was designed to assess the reliability of plant-wax markers for estimating botanical composition of test diets, and diet choices in beef cattle, and provided opportunities to evaluate efficiency in growing heifers. To test estimation of botanical composition, samples of red clover and fescue hay were mixed to form test diets containing 0-100% of either forage. To test estimation of diet choices, 24 heifers from large and moderate frame size lines were evaluated at two instances. Cubed red clover and fescue hays were offered ad libitum. After an acclimation period, feed intakes and body weights were collected for 10 days; fecal samples were collected for the final 5 days. Hydrocarbons and alcohols were quantified with gas chromatography. Estimates were based on least squares. Operator expertise affected measured concentrations of shorter-chained n-alkanes (P<0.041) and long-chain alcohols (P<0.02). Still, overall reliability of the technique was unaffected. Large and moderate framed animals did not differ in efficiency (P>0.05), although large framed animals had increased red clover intakes (P<0.01). Once corrected for fecal losses of n-alkanes, diet choices were estimated accurately. Plant-wax markers provided reliable estimates of botanical composition of diets, and diet choices of animals, suggesting it is a valuable tool to assess efficiencies of grazing cattle. / Master of Science

In recent years, there has been a growing interest in feeding phytogenic products to poultry for their growth and health benefits. The objective of this experiment was to determine the effects of a phytogenic feed additive on turkey poult performance and digestive physiology over a 6-week brooding period. In total, 864 male Hybrid Converter turkey poults were obtained from a local commercial hatchery on day-of-hatch and placed into floor pens with clean pine shavings. The treatments were randomly assigned including an industry-type corn-soybean meal positive control (PC), a similar diet with a 1.5% reduction in crude protein and key amino acids (NC), or the NC with the addition of Digestarom® (PFA) included at a rate of 1 g/kg. Body weight gain (BWG), feed intake (FI), feed efficiency (FE), and mortality were recorded throughout the experiment. On day 14 poults fed the PFA had significantly higher BWG compared to the PC and NC fed birds. By day 42 birds fed the PC and PFA diets had significantly higher BWG compared to the NC, and the PC had significantly higher FE compared to the NC and PFA fed birds. No differences in FI or mortality were observed throughout the experiment. There were no significant differences in AMEn, crude protein digestibility, or nutrient transporter or pancreatic enzyme mRNA expression among treatments. However, aminopeptidase activity tended to be lower in the ileum of poults fed the PC or PFA diets compared to the NC, suggesting that the PFA may be improving protein utilization. / Master of Science / Recent regulations and customer demand have severely restricted the use of antibiotics in poultry production. Historically, antibiotics have been included in poultry diets at sub-therapeutic concentrations to improve performance and reduce disease incidence. Since this restriction, producers have experienced increased feed conversion ratio, decreased body weights, and increases in morbidity and mortality. Not only does this present an animal welfare issue, but producers experience decreased profits due to the decrease in performance associated with restricted antibiotic use. Many researchers are investigating the ability of alternative feed additives to help mitigate the lost performance this restriction has caused. One such alternative is a class of compounds known generally as phytogenic feed additives. These are herbs, spices, and associated products which can be included into the diet at relatively low concentrations. Previous research has demonstrated the ability of phytogenic feed additives to positively influence performance and gastrointestinal tract health, primarily in broiler chickens. Therefore, the objective of this thesis is to investigate the effect of a commercially available phytogenic feed additive on the performance, nutrient digestibility, and absorption in turkey poults over the first six weeks of feeding. Previous indications with this product seem to indicate that it also increases protein utilization so this product was evaluated using a reduced protein diet. By day 14, poults fed the feed additive had significantly higher body weights compared to both the positive and negative control. At the conclusion of the experiment on day 42, the birds fed the feed additive had significantly higher body weight compared to the negative control and were similar to the positive control. This suggests the ability of the feed additive to improve performance when dietary protein is reduced. Data from aminopeptidase activity in the ileum suggest a potential improvement in the efficiency of protein utilization, which may explain the performance improvements when poults were fed the phytogenic feed additive.

BACKGROUND:General, breed- and diet-dependent associations between feed efficiency in beef cattle and single nucleotide polymorphisms (SNPs) or haplotypes were identified on a population of 1321 steers using a 50K SNP panel. Genomic associations with traditional two-step indicators of feed efficiency - residual feed intake (RFI), residual average daily gain (RADG), and residual intake gain (RIG) - were compared to associations with two complementary one-step indicators of feed efficiency: efficiency of intake (EI) and efficiency of gain (EG). Associations uncovered in a training data set were evaluated on independent validation data set. A multi-SNP model was developed to predict feed efficiency. Functional analysis of genes harboring SNPs significantly associated with feed efficiency and network visualization aided in the interpretation of the results.RESULTS:For the five feed efficiency indicators, the numbers of general, breed-dependent, and diet-dependent associations with SNPs (P-value<0.0001) were 31, 40, and 25, and with haplotypes were six, ten, and nine, respectively. Of these, 20 SNP and six haplotype associations overlapped between RFI and EI, and five SNP and one haplotype associations overlapped between RADG and EG. This result confirms the complementary value of the one and two-step indicators. The multi-SNP models included 89 SNPs and offered a precise prediction of the five feed efficiency indicators. The associations of 17 SNPs and 7 haplotypes with feed efficiency were confirmed on the validation data set. Nine clusters of Gene Ontology and KEGG pathway categories (mean P-value<0.001) including, 9nucleotide binding / ion transport, phosphorous metabolic process, and the MAPK signaling pathway were overrepresented among the genes harboring the SNPs associated with feed efficiency.CONCLUSIONS:The general SNP associations suggest that a single panel of genomic variants can be used regardless of breed and diet. The breed- and diet-dependent associations between SNPs and feed efficiency suggest that further refinement of variant panels require the consideration of the breed and management practices. The unique genomic variants associated with the one- and two-step indicators suggest that both types of indicators offer complementary description of feed efficiency that can be exploited for genome-enabled selection purposes.

L'amélioration de l'efficacité alimentaire est un enjeu économique et environnemental important pour la production porcine. L'aliment est le premier poste de dépenses en élevage porcin, et le restera vraisemblablement au vu de l'évolution du coût des matières premières. Historiquement, l'efficacité alimentaire a été améliorée en sélectionnant, avec succès, pour une diminution de l'indice de consommation (IC), qui représente l'efficacité de conversion de l'aliment en gain de poids. Dans un contexte d'évolution des objectifs de sélection, de nouvelles stratégies d'amélioration de l'efficacité alimentaire sont recherchées. Ce travail de thèse propose d'en explorer certaines en utilisant des données enregistrées en stations publiques de contrôle de performance entre 2000 et 2009 dans les quatre races porcines en sélection collective en France, deux races maternelles (Large White femelle et Landrace) et deux races paternelles (Large White mâle et Piétrain). L'approche privilégiée s'appuie sur la consommation moyenne journalière résiduelle (CMJR), qui est un critère d'efficacité alimentaire indépendant des performances des animaux, afin d'estimer ses relations génétiques avec les performances de production, ainsi qu'avec les quantités d'azote et de phosphore excrétées. Dans un premier temps, l'étude d'une population expérimentale Large White a montré que les corrélations génétiques entre sexes pour la CMJR étaient proches de 1, permettant par la suite de comparer les estimations de paramètres obtenues sur des femelles Piétrain à celles obtenues sur les mâles castrés des trois autres races. Nous montrons que ce caractère a une héritabilité (h²) comprise entre 0,21 et 0,33 selon les races, qu'il est un peu moins héritable que l'IC (h² entre 0,30 et 0,40), que ces deux caractères présentent des corrélations génétiques favorables (entre 0,52 et 0,85), et que si la CMJR est par définition phénotypiquement indépendante des caractères de croissance et de composition corporelle, elle l'est aussi au niveau génétique (corrélations inférieures à 0,16 en valeur absolue quelle que soit la race). En revanche, la CMJR, comme l'IC, a des relations génétiques antagonistes avec les caractères de qualité de la viande. Cependant, nous montrons que la CMJR, contrairement à l'IC, n'est pas affectée par le génotype halothane en ségrégation chez le Piétrain. Enfin, des corrélations génétiques très élevées avec l'IC (0,97 et plus), et plus modérées avec la CMJR (entre 0,38 et 0,86) ont été trouvées pour l'excrétion d'azote et de phosphore, suggérant la réduction attendue des rejets en réponse à la sélection sur l'efficacité alimentaire. Ces corrélations étaient globalement plus élevées dans les races paternelles que dans les races maternelles. Enfin, l'étude des cinétiques de croissance et d'ingestion des animaux en fonction de leur niveau d'efficacité alimentaire a montré qu'une sélection pour des animaux plus efficaces ne peut être réalisée qu'en adaptant la formulation des aliments, notamment leur concentration en acides aminés, de façon à permettre la pleine expression de leur potentiel génétique. / Improvement of feed efficiency is a main economic and environmental goal for pig production. Feed is the first component of cost production for pig farmers, and this will remain the case due to the evolution of feedstuffs cost. Historically, feed efficiency has been improved through selection, with success, for a decrease of feed conversion ratio (FCR) representing efficiency of feed conversion into body weight gain. In a context of evolving breeding objectives, new strategies of feed efficiency improvement are investigated. This PhD work has studied some of them using data collected in the French central test stations between 2000 and 2009 for the four main pigs breeds used in collective selection, i.e. two dam breeds (Large White dam line and Landrace) and two sire breeds (Large White sire line and Piétrain). The main approach retained here deals with residual feed intake (RFI), which is a criterion of feed efficiency independent from animal's performance level, in order to estimate its genetic relationships with usual production traits, and also with nitrogen and phosphorus quantities excreted by the animals. In a first step, a study of an experimental Large White population showed that genetic correlations between the three sexes for RFI were very close to 1 for RFI. This result allowed the comparisons of the results obtained on Piétrain females with those obtained on castrated males in the three other breeds. We showed that RFI had an heritability (h²) ranging between 0.21 and 0.33 depending on the breed, slightly less heritable than FCR (h² between 0.30 and 0.40) and with a favourable genetic correlation between them (between 0.52 and 0.85). The RFI is, by definition, phenotypically independent from growth rate and carcass composition traits, and this was also the case at the genetic level (genetic correlations lower than 0.16 in absolute values whatever the breed). However, RFI, like FCR, did not display favourable genetic correlations with meat quality traits. Contrary to FCR, RFI was shown to be unaffected by the halothane genotype segregating in the Piétrain breed. Very high genetic correlations with FCR (0.97 and higher), and more moderate genetic correlations with RFI (between 0.38 and 0.86) were found for nitrogen and phosphorus excreted quantities, which indicates that the reduction of excreted quantities is expected in response to selection for a better feed efficiency. These genetic correlations were globally higher in sire lines than in dam lines. Finally, the study of growth and feed intake curves of animals classified according to their feed efficiency level (either RFI or FCR) suggested that breeding for more efficient animals could not be conducted without an adaptation of feed formulation (e.g. for amino acids concentration), in order to allow the full expression of their genetic potential.