Low Residual Feed Intake Animals Research Articles

Variability in residual feed intake, nutrient utilisation and blood parametersin Murrah buffalo calves fed on total mixed ration

The present study was conducted on 18 female Murrah buffalo calves divided into two treatment groups to determine the residual feed intake, nutrient digestibility and blood metabolite parameters when fed with ration containing wheat (Triticum aestivum) straw, berseem (Trifolium alexandrinum) fodder as roughages and concentrate mixture to meet their requirements. Regular recording of body weight and feed intake was done during 90-day trial period. Residual feed intake (RFI) values were determined for individual animals based on which they were divided into low and high RFI groups. DM intake was lower in low RFI animals than high RFI animals. The blood glucose level and growth hormone level in low and high RFI group was comparable in both groups. Low RFI group had greater concentration of creatinine (1.62 vs. 1.21 mg/dL) as well as IGF-1 (136.70 vs. 120.38 ng/mL) whereas, concentration of total plasma protein level (6.80 vs 7.43 g/dL), albumin (3.46 vs 3.71 g/dl), aspartate aminotransferase (102.20 vs. 122.60 IU/L) and cortisol (3.48 vs. 5.32 ng/mL) were lesser in low RFI group with respect to high RFI group, indicating a positive correlation of RFI with total plasma protein, albumin, aspartate aminotransferase and cortisol and a negative correlation with plasma creatinine and IGF-1 levels in female Murrah buffalo calves. It was concluded that low RFI group of female Murrah buffalo calves showed better performance when fed with total mixed ration.

Effects of Feeding and Drinking Behavior on Performance and Carcass Traits in Beef Cattle.

Feed and water efficiency are important traits to improve beef cattle production's economic and environmental sustainability. This study evaluated residual feed intake (RFI) and residual water intake (RWI) and their relationship with performance, ingestive behavior, and carcass traits in Caracu beef cattle. The data were analyzed using a generalized linear model with least squares means. The ingestive behavior, performance, and carcass traits were influenced by sex (p < 0.05). Males showed higher dry matter intake (DMI), average daily gain (ADG), mid-test metabolic weight (BW0.75), rib eye area, and rump fat thickness than females, besides spending more time drinking and eating. Low RFI animals exhibited higher DMI than high RFI animals. Low RWI animals ingested 3.89 L/d of water further than high RWI animals. The interaction between sex and RWI influenced the DMI, BW0.75, and backfat thickness. The ingestive behavior of low and high RFI animals was similar, although high RWI animals visited a smaller number of drinkers than low RWI animals. Water intake positively affects productive efficiency, and the combined use of RWI and RFI may help improve the selection of more efficient animals contributing to reducing the costs of beef cattle production and improving environmental sustainability.

Residual feed intake and related biochemical parameters in male Sahiwal calves

This study was conducted to evaluate the differences in efficiency of feed utilisation in Sahiwal calves with low and high residual feed intake (RFI) by comparing feed intake, nutrient digestibility, growth traits and blood biochemical parameters. Eighteen growing male Sahiwal calves (aged 12 months, average body weight 120.04 kg) were selected and fed individually total mixed ration as per their requirements for a period of 60 days. Fifty per cent of maize grains in concentrate mixture containing 33% maize grains were replaced by fresh potatoes (DM basis). Based on linear regression models involving dry matter intake (DMI), average daily gain (ADG) and mid test metabolic body size, calves were assigned into low and high RFI groups. Residual feed intake (RFI) values were calculated for individual calves and the calves were divided into low (–0.20) and high (+0.18) RFI groups. Low RFI animals consumed less dry matter than the expected or predicted one indicating their more efficiency of feed utilization. The intakes of DM and CP were 4.95 and 6.47% lower in low RFI animals compared to high RFI animals while average daily gain was higher in low RFI group. The digestibility of DM, OM, CP, EE, total carbohydrates, NDF and ADF were similar in low and high RFI groups, however, nitrogen retention was higher in low RFI group. Values of alanine amino transferase (25.85 vs. 35.72 IU/L), aspartate amino transferase (80.33 vs. 100.57 IU/L), total protein (7.34 and 8.24 mg/dL), blood urea nitrogen (15.45 and 22.22 mg/dL) and creatinine (1.27 and 1.78 mg/dL) were higher for high RFI as compared to low RFI group. The concentration of growth hormone, insulin and IGF-1 were similar in both the groups. From present study, it could be concluded that low RFI animals were more efficient in feed conversion.

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

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 was 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.

Nitrogen metabolism and mammary gland amino acid utilization in lactating dairy cows with different residual feed intake.

ObjectiveThis study was conducted to enhance our understanding of nitrogen (N) metabolism and mammary amino acid (AA) utilization in lactating cows with divergent phenotypes of residual feed intake (RFI).MethodsFifty-three multiparous mid-lactation Holstein dairy cows were selected for RFI measurements over a 50-d experimental period. The 26 cows with the most extreme RFI values were classified into the high RFI (n = 13) and low RFI (n = 13) groups, respectively, for analysis of N metabolism and AA utilization.ResultsCompared with the high RFI cows, the low RFI animals had lower dry matter intake (p<0.01) with no difference observed in milk yield between the two groups (p> 0.10). However, higher ratios of milk yield to dry matter intake (p<0.01) were found in the low RFI cows than in the high RFI cows. The low RFI cows had significant greater ratios of milk protein to metabolizable protein (p = 0.02) and milk protein to crude protein intake than the high RFI cows (p = 0.01). The arterial concentration and mammary uptake of essential AA (p<0.10), branched-chain AA (p<0.10), and total AA (p<0.10) tended to be lower in the low RFI cows. Additionally, the low RFI cows tended to have a lower ratio of AA uptake to milk output for essential AA (p = 0.08), branched-chain AA (p = 0.07) and total AA (p = 0.09) than the high RFI cows.ConclusionIn summary, both utilization of metabolizable protein for milk protein and mammary AA utilization are more efficient in cows with lower RFI than in the high RFI cows. Our results provide new insight into the protein metabolic processes (related to N and AA) involved in feed efficiency.

Growth, ruminal and metabolic parameters and feeding behavior of Nellore cattle with different residual feed intake phenotypes

The aim of this study was to evaluate growth, ruminal and metabolic parameters and feeding behavior of young Nellore males classified based on postweaning residual feed intake (RFI). Fifty-nine Nellore males (290 ± 20 days of age and 294 ± 8.48 kg of body weight) were evaluated for 70 days in a feed efficiency test conducted with the GrowSafe System®, with automatic and daily measurement of individual feed intake and feeding behavior. The animals were weighed every 14 days. Body measures and blood samples were obtained at the beginning and end of the efficiency test. The RFI was calculated as the residual of the regression equation of dry matter (DM) intake on average daily weight gain and mid-test metabolic body weight. The animals were classified as low (n = 25), medium (n = 15), and high (n = 19) RFI. Six low RFI and six high RFI animals were used for determining ruminal parameters and microbial nitrogen. The data were analyzed considering the fixed effect of RFI class and initial age as linear covariate. Low RFI animals consumed less DM to achieve a performance similar to that of animals with medium and high RFI. The different RFI groups did not influence ruminal fermentation parameters, microbial nitrogen, blood metabolites, or body measures. Low RFI animals spent less time at the feed bunk when compared to animals with medium and high RFI for a similar amount of feed consumed per visit. Animals with low RFI are efficient in feed utilization as demonstrated by their good production potential despite lower feed intake, without losses in growth or ruminal and metabolic parameters.

Serum Metabolite Biomarkers for Predicting Residual Feed Intake (RFI) of Young Angus Bulls.

Residual feed intake (RFI) is a feed efficiency measure commonly used in the livestock industry to identify animals that efficiently/inefficiently convert feed into meat or body mass. Selection for low-residual feed intake (LRFI), or feed efficient animals, is gaining popularity among beef producers due to the fact that LRFI cattle eat less and produce less methane per unit weight gain. RFI is a difficult and time-consuming measure to perform, and therefore a simple blood test that could distinguish high-RFI (HRFI) from LRFI animals (early on) would potentially benefit beef farmers in terms of optimizing production or selecting which animals to cull or breed. Using three different metabolomics platforms (nuclear magnetic resonance (NMR) spectrometry, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and inductively coupled plasma mass spectrometry (ICP-MS)) we successfully identified serum biomarkers for RFI that could potentially be translated to an RFI blood test. One set of predictive RFI biomarkers included formate and leucine (best for NMR), and another set included C4 (butyrylcarnitine) and LysoPC(28:0) (best for LC-MS/MS). These serum biomarkers have high sensitivity and specificity (AUROC > 0.85), for distinguishing HRFI from LRFI animals. These results suggest that serum metabolites could be used to inexpensively predict and categorize bovine RFI values. Further validation using a larger, more diverse cohort of cattle is required to confirm these findings.

Mitochondrial protein gene expression and the oxidative phosphorylation pathway associated with feed efficiency and energy balance in dairy cattle

Feed efficiency and energy balance are important traits underpinning profitability and environmental sustainability in animal production. They are complex traits, and our understanding of their underlying biology is currently limited. One measure of feed efficiency is residual feed intake (RFI), which is the difference between actual and predicted intake. Variation in RFI among individuals is attributable to the metabolic efficiency of energy utilization. High RFI (H_RFI) animals require more energy per unit of weight gain or milk produced compared with low RFI (L_RFI) animals. Energy balance (EB) is a closely related trait calculated very similarly to RFI. Cellular energy metabolism in mitochondria involves mitochondrial protein (MiP) encoded by both nuclear (NuMiP) and mitochondrial (MtMiP) genomes. We hypothesized that MiP genes are differentially expressed (DE) between H_RFI and L_RFI animal groups and similarly between negative and positive EB groups. Our study aimed to characterize MiP gene expression in white blood cells of H_RFI and L_RFI cows using RNA sequencing to identify genes and biological pathways associated with feed efficiency in dairy cattle. We used the top and bottom 14 cows ranked for RFI and EB out of 109 animals as H_RFI and L_RFI, and positive and negative EB groups, respectively. The gene expression counts across all nuclear and mitochondrial genes for animals in each group were used for differential gene expression analyses, weighted gene correlation network analysis, functional enrichment, and identification of hub genes. Out of 244 DE genes between RFI groups, 38 were MiP genes. The DE genes were enriched for the oxidative phosphorylation (OXPHOS) and ribosome pathways. The DE MiP genes were underexpressed in L_RFI (and negative EB) compared with the H_RFI (and positive EB) groups, suggestive of reduced mitochondrial activity in the L_RFI group. None of the MtMiP genes were among the DE MiP genes between the groups, which suggests a non-rate limiting role of MtMiP genes in feed efficiency and warrants further investigation. The role of MiP, particularly the NuMiP and OXPHOS pathways in RFI, was also supported by our gene correlation network analysis and the hub gene identification. We validated the findings in an independent data set. Overall, our study suggested that differences in feed efficiency in dairy cows may be linked to differences in cellular energy demand. This study broadens our knowledge of the biology of feed efficiency in dairy cattle.

Meat and sensory quality of major muscles from Angus, Charolais, and Angus crossbred steers with high and low residual feed intake

Effects of residual feed intake (RFI) and genetic group on growth, carcass, and meat quality characteristics of bovine longissimus lumborum (LL), triceps brachii (TB), semimembranosus (SM), and gluteus medius (GM) muscles were investigated using 72 purebred Angus, purebred Charolais, and Angus crossbred steers (n = 24 per genetic group) classified as either high (inefficient) or low (efficient) RFI (n = 12 high and low RFI steers within genetic group). There was no RFI effect (P &gt; 0.05) on growth, carcass, and meat quality measurements except high RFI steers had the highest dry matter intake (P &lt; 0.05), and low RFI TB was rated as having reduced beef flavour intensity and sustained juiciness (P &lt; 0.05). Purebred Angus and Charolais LL and GM had lower shear force values (P &lt; 0.05) than Angus crossbreds and ageing reduced mean shear force values except in TB. For TB, SM, and GM, Angus crossbred steers had the highest mean beef flavour intensity scores, and Charolais SM and TB were less tender than those of Angus crossbred (P &lt; 0.05). Overall, RFI did not influence most meat quality traits; therefore, low RFI animals may contribute to reducing feed costs or environmental impact without compromising meat quality and palatability.

Association between residual feed intake, digestion, ingestive behavior, enteric methane emission and nitrogen metabolism in Nellore beef cattle.

This study aimed to evaluate nutrient intake and digestibility, enteric methane emission and nitrogen utilization efficiency in Nellore cattle ranked by residual feed intake (RFI). Twenty-four Nellore bulls at 466±24days of age and with 352±14.6kg of body weight, classified as low and high RFI, were evaluated. Animals were kept in individual pens for three periods of 28days and variables were measured. Data were analyzed as repeated measures over time, considering as fixed effects RFI class, period and RFI class x period interaction, and linear (co)variate of age. No significant differences in dry matter or nutrient intake were detected between RFI classes, but total digestible nutrients intake tended to be lower in low RFI animals, and apparent nutrient digestibility was higher in high RFI animals. Partial efficiency of growth tended to be lower in high RFI animals. RFI class did not interfere with enteric methane production or microbial protein synthesis, but fecal nitrogen output was higher in low RFI animals. The greater efficiency of low RFI animals is consequence of lower maintenance requirements, since energy from higher nutrients digestibility in high RFI animals was spent on metabolic processes other than body tissue deposition.

Effects of Breed Type, Residual Feed Intake and Post-Mortem Aging on Physio-Chemical Properties of Triceps Brachii Muscle and Their Relationships With Beef Toughness

ObjectivesThe influence of breed type, residual feed intake (RFI) and post-mortem aging on meat and carcass quality attributes and intramuscular connective tissue characteristics were examined in the bovine Triceps brachii, a high connective tissue muscle from the chuck. The hypothesis that selection for low RFI in beef cattle increases beef toughness, increases collagen content and reduces collagen heat solubility of the Triceps brachii was tested.Materials and MethodsSeventy-one beef steers from Angus (n = 23), Charolais (n = 24) and Angus crossbred (n = 24)) genetics were used. Each breed had high RFI and low RFI steers (n = 12). Muscles collected were aged for 3- and 13-days post-mortem (dpm). Final animal live weight, grade marbling, intramuscular pH, water holding capacity (WHC), intramuscular fat, cooking loss, drip loss, protein, temperature, moisture, color, RFI, and Warner Bratzler shear force (WBSF) data were collected for carcass and meat quality measurements. Total collagen, collagen heat solubility, and collagen cross-link Ehrlich’s chromogen (EC) of the isolated perimysium were quantified. Data were analyzed using a split-plot experimental design procedure (R software 3.4.1) with breed and RFI as main effects in the whole plot and postmortem aging included at the subplot level.ResultsFinal weight was significantly greater for Charolais (683 ± 9.58 kg) than Angus (554 ± 9.65 kg) and Angus crossbred (568 kg ± 9.58 kg) steers (P = 0.017), and grade marbling score was higher for high RFI (421 ± 19.85) than for low RFI steer carcasses (385 ± 19.82) (P = 0.001). No significant effects of breed type and RFI (P &gt; 0.05) were observed on meat quality attributes. WBSF value at 3 dpm (3.72 kg) was significantly higher than at 13dpm (3.21 kg) (P &lt; 0.005). Collagen solubility was significantly higher at 13 dpm (25.88%) than at 3 dpm (18.03%) (P &lt; 0.005). Total collagen and wet endomysium were positively correlated (r = 0.44) as were total collagen and EC in raw muscle (r = 0.76), EC and wet perimysium (r = 0.42) and WBSF and EC at 13 dpm (r = 0.27) (P &lt; 0.005). Total collagen and collagen solubility at 3dpm (r = –0.36) and 13 dpm (r = –0.63) were negatively correlated, as were EC and solubility at 3 dpm (r = –0.38) (P &lt; 0.005).ConclusionIncreasing postmortem aging periods reduced WBSF and increased collagen heat solubility of the Triceps brachii muscle. With no effect of RFI on meat quality measurements, the production cost can be reduced by selecting for low RFI animals without sacrificing product quality.Table 7.Least square means (± standard error of the mean) for WBSF, soluble collagen, and collagen solubility of Triceps brachii muscles at 3 and 13 d post-mortem aging (dpm)

Metabolomics Analyses in High-Low Feed Efficient Dairy Cows Reveal Novel Biochemical Mechanisms and Predictive Biomarkers.

Residual feed intake (RFI) is designed to estimate net efficiency of feed use, so low RFI animals are considered for selection to reduce feeding costs. However, metabolic profiling of cows and availability of predictive metabolic biomarkers for RFI are scarce. Therefore, this study aims to generate a better understanding of metabolic mechanisms behind low and high RFI in Jerseys and Holsteins and identify potential predictive metabolic biomarkers. Each metabolite was analyzed to reveal their associations with two RFIs in two breeds by a linear regression model. An integrative analysis of metabolomics and transcriptomics was performed to explore interactions between functionally related metabolites and genes in the created metabolite networks. We found that three main clusters were detected in the heat map and all identified fatty acids (palmitoleic, hexadecanoic, octadecanoic, heptadecanoic, and tetradecanoic acid) were grouped in a cluster. The lower cluster were all from fatty acids, including palmitoleic acid, hexadecanoic acid, octadecanoic acid, heptadecanoic acid, and tetradecanoic acid. The first component of the partial least squares-discriminant analysis (PLS-DA) explained a majority (61.5%) of variations of all metabolites. A good division between two breeds was also observed. Significant differences between low and high RFIs existed in the fatty acid group (P < 0.001). Statistical results revealed clearly significant differences between breeds; however, the association of individual metabolites (leucine, ornithine, pentadecanoic acid, and valine) with the RFI status was only marginally significant or not significant due to a lower sample size. The integrated gene-metabolite pathway analysis showed that pathway impact values were higher than those of a single metabolic pathway. Both types of pathway analyses revealed three important pathways, which were aminoacyl-tRNA biosynthesis, alanine, aspartate, and glutamate metabolism, and the citrate cycle (TCA cycle). Finally, one gene (2-hydroxyacyl-CoA lyase 1 (+HACL1)) associated with two metabolites (-α-ketoglutarate and succinic acid) were identified in the gene-metabolite interaction network. This study provided novel metabolic pathways and integrated metabolic-gene expression networks in high and low RFI Holstein and Jersey cattle, thereby providing a better understanding of novel biochemical mechanisms underlying variation in feed efficiency.

Hot topic: Selecting cattle for low residual feed intake did not affect daily methane production but increased methane yield

Reducing enteric methane (CH4) production and improving feed conversion efficiency of dairy cows is of high importance. Residual feed intake (RFI) is one measure of feed efficiency, with low RFI animals being more efficient in feed conversion. Enteric CH4 is an important source of digestible energy loss in ruminants and, because research in beef cattle has reported a positive relationship between RFI and daily CH4 production, we hypothesized that low RFI dairy heifers, which are more feed efficient, would produce less CH4/d. We measured the daily methane production (g of CH4/d), methane yield [g of CH4/kg of dry matter intake (DMI)], and CH4 per kilogram of body weight (BW) gain for 56 heifers (20-22 mo old) in a 2 × 2 factorial arrangement: factors included 2 breeds (Holstein-Friesian and Jersey; n = 28/breed), with equal numbers of animals previously determined as being either high [+2.0 kg of dry matter (DM)/d] or low RFI (-2.1 kg of DM/d; n = 28/RFI category). All heifers were commingled and offered unrestricted access to the same diet of dried alfalfa cubes. Between RFI categories, heifers did not differ in BW or BW gain but low RFI heifers had 9.3 and 10.6% lower DMI and DMI/kg of BW, respectively, than high RFI heifers. Similarly, RFI category did not affect CH4/d or CH4/kg of BWg, but CH4/kg of DMI was higher in low RFI heifers because of their lower DMI. These results might reflect more complete digestion of ingested feed in the more efficient, low RFI heifers, consistent with previous reports of greater apparent digestibility of organic matter. Holstein-Friesian heifers were heavier and consumed more total DM than Jersey heifers, but breed did not affect DMI/kg of BW or BWg. Jersey heifers produced less CH4/d, but not CH4/kg of DMI or CH4/kg of BWg. We detected no interaction between breed and RFI category in any of the variables measured. In conclusion, differences in RFI in dairy heifers did not affect daily CH4 production (g/d); however, low RFI heifers had a greater CH4 yield (g/kg of DMI) on a high forage diet.

Effects of Breed Type, Residual Feed Intake and Post-Mortem Aging on Physio-Chemical Properties of Triceps Brachii Muscle and Their Relationships With Beef Toughness

ObjectivesThe influence of breed type, residual feed intake (RFI) and post-mortem aging on meat and carcass quality attributes and intramuscular connective tissue characteristics were examined in the bovine Triceps brachii, a high connective tissue muscle from the chuck. The hypothesis that selection for low RFI in beef cattle increases beef toughness, increases collagen content and reduces collagen heat solubility of the Triceps brachii was tested.Materials and MethodsSeventy-one beef steers from Angus (n = 23), Charolais (n = 24) and Angus crossbred (n = 24)) genetics were used. Each breed had high RFI and low RFI steers (n = 12). Muscles collected were aged for 3- and 13-days post-mortem (dpm). Final animal live weight, grade marbling, intramuscular pH, water holding capacity (WHC), intramuscular fat, cooking loss, drip loss, protein, temperature, moisture, color, RFI, and Warner Bratzler shear force (WBSF) data were collected for carcass and meat quality measurements. Total collagen, collagen heat solubility, and collagen cross-link Ehrlich’s chromogen (EC) of the isolated perimysium were quantified. Data were analyzed using a split-plot experimental design procedure (R software 3.4.1) with breed and RFI as main effects in the whole plot and postmortem aging included at the subplot level.ResultsFinal weight was significantly greater for Charolais (683 ± 9.58 kg) than Angus (554 ± 9.65 kg) and Angus crossbred (568 kg ± 9.58 kg) steers (P = 0.017), and grade marbling score was higher for high RFI (421 ± 19.85) than for low RFI steer carcasses (385 ± 19.82) (P = 0.001). No significant effects of breed type and RFI (P > 0.05) were observed on meat quality attributes. WBSF value at 3 dpm (3.72 kg) was significantly higher than at 13dpm (3.21 kg) (P < 0.005). Collagen solubility was significantly higher at 13 dpm (25.88%) than at 3 dpm (18.03%) (P < 0.005). Total collagen and wet endomysium were positively correlated (r = 0.44) as were total collagen and EC in raw muscle (r = 0.76), EC and wet perimysium (r = 0.42) and WBSF and EC at 13 dpm (r = 0.27) (P < 0.005). Total collagen and collagen solubility at 3dpm (r = –0.36) and 13 dpm (r = –0.63) were negatively correlated, as were EC and solubility at 3 dpm (r = –0.38) (P < 0.005).ConclusionIncreasing postmortem aging periods reduced WBSF and increased collagen heat solubility of the Triceps brachii muscle. With no effect of RFI on meat quality measurements, the production cost can be reduced by selecting for low RFI animals without sacrificing product quality.Table 7.Least square means (± standard error of the mean) for WBSF, soluble collagen, and collagen solubility of Triceps brachii muscles at 3 and 13 d post-mortem aging (dpm)

Residual feed intake phenotype and gender affect the expression of key genes of the lipogenesis pathway in subcutaneous adipose tissue of beef cattle

BackgroundFeed accounts for up to 75% of costs in beef production systems, thus any improvement in feed efficiency (FE) will benefit the profitability of this enterprise. Residual feed intake (RFI) is a measure of FE that is independent of level of production. Adipose tissue (AT) is a major endocrine organ and the primary metabolic energy reservoir. It modulates a variety of processes related to FE such as lipid metabolism and glucose homeostasis and thus measures of inter-animal variation in adiposity are frequently included in the calculation of the RFI index. The aim of this study was to determine the effect of phenotypic RFI status and gender on the expression of key candidate genes related to processes involved in energy metabolism within AT. Dry matter intake (DMI) and average daily gain (ADG) were measured over a period of 70 d for 52 purebred Simmental heifers (n = 24) and bulls (n = 28) with an initial BW±SD of 372±39.6 kg and 387±50.6 kg, respectively. Residual feed intake was calculated and animals were ranked within gender by RFI into high (inefficient; n = 9 heifers and n = 8 bulls) and low (efficient; n = 9 heifers and n = 8 bulls) groups.ResultsAverage daily gain ±SD and daily DMI ±SD for heifers and bulls were 1.2±0.4 kg and 9.1±0.5 kg, and 1.8±0.3 kg and 9.5±1 kg respectively. High RFI heifers and bulls consumed 10% and 15% more (P < 0.05) than their low RFI counterparts, respectively. Heifers had a higher expression of all genes measured than bulls (P < 0.05). A gender × RFI interaction was detected for HMGCS2(P < 0.05) in which high RFI bulls tended to have lower expression of HMGCS2 than low RFI bulls (P < 0.1), whereas high RFI heifers had higher expression than low RFI heifers (P < 0.05) and high RFI bulls (P < 0.05). SLC2A4 expression was consistently higher in subcutaneous AT of low RFI animals across gender.ConclusionThe findings of this study indicate that low RFI cattle exhibit upregulation of the molecular mechanisms governing glucose metabolism in adipose tissue, in particular, glucose clearance. The decreased expression of SLC2A4 in the inefficient cattle may result in less efficient glucose metabolism in these animals. We conclude that SLC2A4 may be a potential biomarker for RFI in cattle.

Proteomic investigation of liver from beef cattle (Bos indicus) divergently ranked on residual feed intake.

Proteomics studies can be used to identify proteins that affect feed efficiency traits, related to cost and profitability of meat production. We used a proteomic approach based on two-dimensional electrophoresis (2D-PAGE) in combination with mass spectrometry (ESI-MS) to study liver samples of Nellore bulls divergently ranked according to residual feed intake (RFI). The study showed that 71 protein spots were expressed differentially (P < 0.05) among RFI groups and 47 were identified by ESI-MS. In RFI, efficient animals (low RFI) eat less than predictions, based on their weights and growth rate, while inefficient animals (high RFI) that eat more than predicted. Data from 18 animals (9 high vs. 9 low RFI) aged 24-26months in feedlot finishing were used. Immediately after slaughter, liver samples were collected and protein extracts were separated. The gels of RFI groups were scanned and the images analyzed, whereby we found 279 and 215 liver protein spots in high and low RFI bulls, respectively. The proteins identified were related to the following biological functions: (I) oxygen transport and blood flow; (II) mitochondrial function and energy metabolism; (III) amino acid metabolism, ion transport, and cell survival. The study suggests hemoglobin subunit beta and heat shock protein 71kDa and as molecular markers to study FE in Nellore cattle. Moreover, proteins such as 3-ketoacyl-CoA thiolase and glutamate dehydrogenase 1 were found in liver from high and low RFI animals, respectively. Such protein expression could be associated with changes in the oxidative capacity of RFI phenotypes.

Poor feed efficiency in sheep is associated with several structural abnormalities in the community metabolic network of their ruminal microbes.

Ruminant animals have a symbiotic relationship with the microorganisms in their rumens. In this relationship, rumen microbes efficiently degrade complex plant-derived compounds into smaller digestible compounds, a process that is very likely associated with host animal feed efficiency. The resulting simpler metabolites can then be absorbed by the host and converted into other compounds by host enzymes. We used a microbial community metabolic network inferred from shotgun metagenomics data to assess how this metabolic system differs between animals that are able to turn ingested feedstuffs into body mass with high efficiency and those that are not. We conducted shotgun sequencing of microbial DNA from the rumen contents of 16 sheep that differed in their residual feed intake (RFI), a measure of feed efficiency. Metagenomic reads from each sheep were mapped onto a database-derived microbial metabolic network, which was linked to the sheep metabolic network by interface metabolites (metabolites transferred from microbes to host). No single enzyme was identified as being significantly different in abundance between the low and high RFI animals (P > 0.05, Wilcoxon test). However, when we analyzed the metabolic network as a whole, we found several differences between efficient and inefficient animals. Microbes from low RFI (efficient) animals use a suite of enzymes closer in network space to the host's reactions than those of the high RFI (inefficient) animals. Similarly, low RFI animals have microbial metabolic networks that, on average, contain reactions using shorter carbon chains than do those of high RFI animals, potentially allowing the host animals to extract metabolites more efficiently. Finally, the efficient animals possess community networks with greater Shannon diversity among their enzymes than do inefficient ones. Thus, our system approach to the ruminal microbiome identified differences attributable to feed efficiency in the structure of the microbes' community metabolic network that were undetected at the level of individual microbial taxa or reactions.

Analysis of meat quality traits and gene expression profiling of pigs divergent in residual feed intake

Residual feed intake (RFI), the difference between actual feed intake and predicted feed requirements, is suggested to impact various aspects of meat quality. The objective of this study was to investigate the molecular mechanisms underpinning the relationship between RFI and meat quality. Technological, sensory and nutritional analysis as well as transcriptome profiling were carried out in Longissimus thoracis et lumborum muscle of pigs divergent in RFI (n=20). Significant differences in sensory profile and texture suggest a minor impairment of meat quality in more efficient pigs. Low RFI animals had leaner carcasses, greater muscle content and altered fatty acid profiles compared to high RFI animals. Accordingly, differentially expressed genes were enriched in muscle growth and lipid & connective tissue metabolism. Differences in protein synthesis and degradation suggest a greater turnover of low RFI muscle, while divergence in connective tissue adhesion may impact tenderness. Fatty acid oxidation tending towards decrease could possibly contribute to reduced mitochondrial activity in low RFI muscle.

Residual feed intake, carcass traits and meat quality in Nellore cattle

A total of 127 Nellore bulls classified as low and high residual feed intake (RFI), from three selection lines, were evaluated in five experiments aiming to identify associations between RFI, carcass, and meat quality traits. Feedlot performance, carcass traits, and meat quality of Longissimus muscle were evaluated. A mixed model including the fixed effects of RFI class, selection line, interaction between RFI class and selection line, and age at slaughter as a covariate, and the random effects of diet within experiment and experiment was used, with means compared by the t-test. Feed intake average difference was 0.962kg/day; low RFI animals consumed 0.479kg/day less feed and high RFI animals consumed 0.483kg/day more feed than expected. No differences between RFI classes were detected for most of studied variables, demonstrating the absence of unfavorable associations between RFI and carcass and meat quality traits. Low RFI Nellore animals use feed efficiently and produce good quality carcasses and meat.

Digestion and metabolism of low and high residual feed intake Nellore bulls.

Understanding the reasons why animals of similar performances have different feed requirements is important to increase profits for cattle producers and to decrease the environmental footprint of beef cattle production. This study was carried out aiming to identify the associations between residual feed intake (RFI) and animal performance, nutrient digestibility, and blood metabolites related to energy balance of young Nellore bulls during the finishing period. Animals previously classified as low (n = 13) and high RFI (n = 12), with average initial body weight of 398kg and age of 503days were used. Cattle were fed a high energy diet and were slaughtered when rib fat thickness measured by ultrasound between the 12th and 13th ribs reached the minimum of 4mm. A completely randomized design was adopted, being data analyzed with a mixed model that included the random effect of slaughter group, the fixed effect of RFI class, and linear effect of the covariate feedlot time. No differences were found (p > 0.10) between RFI classes for performance, dry matter, and nutrients intake. However, dry (p = 0.0911) and organic matter (p = 0.0876) digestibility tended to be lower, and digestibility of neutral detergent fiber corrected for ash and protein (p = 0.0017), and total digestible nutrients (p = 0.0657) were lower for high RFI animals, indicating lesser capacity of food utilization. Difference between low and high RFI animals was also found for blood cortisol at the end of the trial (p = 0.0044), having low RFI animals lower cortisol concentrations. Differences in the ability to digest food can affect the efficiency of transforming feed into meat by Nellore cattle.