High Residual Feed Intake Research Articles

Characterization of the rumen microbiota and its relationship with residual feed intake in sheep

Feed efficiency is a highly important economic trait in sheep production and has a significant impact on the economic benefits of sheep farming. Microbial fermentation of the rumen has a vital role in the host's nutrition; the rumen microbiota might affect host feed efficiency. However, the relationship between the rumen microbiota and feed efficiency in sheep is unclear. In the present study, the microbiota of 195 Hu sheep was investigated and their residual feed intake (RFI), a commonly used measure of feed efficiency, was determined. From birth, all sheep were subjected to the same management practices. At slaughter, samples of liquid rumen contents were collected and subjected to amplicon sequencing for the 16S rDNA gene on the IonS5™XL platform. To identify the bacterial taxa differentially represented at the genus or higher taxonomy levels, we used linear discriminant analysis coupled with effect size and curve fitting. In the sheep rumen, the four most abundant phyla were Firmicutes, Bacteroidetes, Fibrobacteres, and Proteobacteria; and the dominant genera were unidentified Prevotellaceae, Fibrobacter, unidentified Lachnospiraceae, Saccharofermentans, and Succinivibrio. Pathway analysis of the 16S rDNA sequencing data from the rumen microbiota identified that carbohydrate metabolism was enriched. Using α-diversity analysis, we further identified that Observed species, ACE, Good's coverage, and Chao1 are more abundant (P < 0.01) in the low-RFI (L-RFI) group compared to the high-RFI (H-RFI) group. High-RFI sheep had a higher abundance of three bacterial taxa (Prevotellaceae, Negativicutes, and Selenomonadales), and one taxa was overrepresented in the L-RFI sheep (Succinivibrio), respectively. Furthermore, model fitting showed that Veillonellaceae, Sphaerochaeta, Negativibacillus, Saccharofermentans, and members of the Tenericutes, Kiritimatiellaeota, Deltaproteobacteria, and Campylobacterales were correlated with the sheep RFI classification and thus were indicative of a role in animal efficiency. Tax4Fun analysis revealed that metabolic pathways such as “energy metabolism,” “metabolism of cofactors and vitamins,” “poorly characterized,” and “replication recombination and repair proteins” were enriched in the rumen from H-RFI sheep, and “genetic information processing” and “lipopolysaccharide biosynthesis” were overrepresented in L-RFI sheep rumen. In addition, six Kyoto Encyclopedia of Genes and Genomes orthology pathways were identified as different between H-RFI and L-RFI groups. In conclusion, the low RFI phenotype (efficient animals) consistently (or characteristically) exhibited a more abundant and diverse microbiome in sheep.

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.

Differential gene expression in duodenum of colored broiler chicken divergently selected for residual feed intake.

Feed constitutes about 70% of the total expenditure of poultry production. Maximizing the feed efficiency in juvenile period is essential to achieve low production cost. The efficiency of feed utilization was measured by RFI (residual feed intake) by calculating the difference between an individual animal's observed and its expected feed intake. The expression of genes influencing low and high RFI is required to know the basic molecular mechanism influencing feed efficiency. The present study aimed to estimate the RFI (0-5week) in a population of indigenously developed colored broiler sire line chicken. The duodenum sample of high and low-RFI broiler chicken was used for microarray analysis. Duodenum exhibited 1030 differentially expressed genes after analysis. Out of total DEGs, 461 genes were downregulated and 569 were upregulated. The fold change of differentialllyexpressed genesvaries from - 162.6 to 1549.28. A subset of genes was validated by qRT-PCR and results were correlated well with microarray data. In functional annotation study of DEGs, 89 biological processes, 30 cellular components, and 29 molecular functions were identified. Study of the important differentially expressed genes and the related molecular pathways in the population may hold the potential for future breeding strategies for augmenting feed efficiency.

Residual feed intake and the inclusion of crude glycerin in the diet of feedlot-finished Nellore cattle

Context The beef market faces an increasing demand for an environmentally friendly production system with high-quality final products. The use of strategies that improve system efficiency without detriment on quality are desired for both producers and consumer. Aims This study aimed to evaluate the effects of residual feed intake (RFI) and dietary inclusion of crude glycerin on carcass and meat quality traits of feedlot-finished Nellore cattle. Methods Nellore bulls selected for growth and classified as high (n = 14) and low (n = 14) RFI, with average liveweight of 328 kg and age of 552 days were used. Bulls received a high-concentrate diet for 96 days before slaughter and were randomly allocated to two experimental diets in a 2 × 2 factorial arrangement: RFI class (low or high) and dietary inclusion (CG) or not (WCG) of crude glycerin (20% on dry-matter basis). Data were analysed with the SAS MIXED procedure considering RFI class and diet as fixed effects and selection line as a random effect. Key results There were no significant differences between RFI classes for dry-matter intake during finishing or production traits. Dry-matter intake tended to be reduced by 16% in CG bulls, without alterations in production. Dietary glycerin inclusion tended to increase the protein content in the Longissimus muscle and significantly reduced the fat content. In low-RFI bulls, shear force was higher in unaged beef, and shear force and myofibrillar fragmentation index tended to be higher in meat aged for 14 days. RFI class did not affect Longissimus muscle fatty acid profile, which was highly influenced by dietary glycerin inclusion. Bulls allocated to the CG treatment had a reduction in saturated fatty acids, an increase in odd-chain fatty acids, and a trend towards increased omega-3 fatty acids, which significantly increased the omega-3:omega-6 ratio. Conclusions The use of Nellore bulls classified as low-RFI and crude glycerin inclusion in finishing diets of Nellore cattle do not compromise production, carcass traits or beef properties. Implications This approach increases the efficiency and sustainability of the production process and improves the nutritional characteristics of beef for human consumption.

Identification of functional candidate variants and genes for feed efficiency in Holstein and Jersey cattle breeds using RNA-sequencing

The identification of functional genetic variants and associated candidate genes linked to feed efficiency may help improve selection for feed efficiency in dairy cattle, providing economic and environmental benefits for the dairy industry. This study used RNA-sequencing data obtained from liver tissue from 9 Holstein cows [n = 5 low residual feed intake (RFI), n = 4 high RFI] and 10 Jersey cows (n = 5 low RFI, n = 5 high RFI), which were selected from a single population of 200 animals. Using RNA-sequencing, 3 analyses were performed to identify: (1) variants within low or high RFI Holstein cattle; (2) variants within low or high RFI Jersey cattle; and (3) variants within low or high RFI groups, which are common across both Holstein and Jersey cattle breeds. From each analysis, all variants were filtered for moderate, modifier, or high functional effect, and co-localized quantitative trait loci (QTL) classes, enriched biological processes, and co-localized genes related to these variants, were identified. The overlapping of the resulting genes co-localized with functional SNP from each analysis in both breeds for low or high RFI groups were compared. For the first two analyses, the total number of candidate genes associated with moderate, modifier, or high functional effect variants fixed within low or high RFI groups were 2,810 and 3,390 for Holstein and Jersey breeds, respectively. The major QTL classes co-localized with these variants included milk and reproduction QTL for the Holstein breed, and milk, production, and reproduction QTL for the Jersey breed. For the third analysis, the common variants across both Holstein and Jersey breeds, uniquely fixed within low or high RFI groups were identified, revealing a total of 86,209 and 111,126 functional variants in low and high RFI groups, respectively. Across all 3 analyses for low and high RFI cattle, 12 and 31 co-localized genes were overlapping, respectively. Among the overlapping genes across breeds, 9 were commonly detected in both the low and high RFI groups (INSRR, CSK, DYNC1H1, GAB1, KAT2B, RXRA, SHC1, TRRAP, PIK3CB), which are known to play a key role in the regulation of biological processes that have high metabolic demand and are related to cell growth and regeneration, metabolism, and immune function. The genes identified and their associated functional variants may serve as candidate genetic markers and can be implemented into breeding programs to help improve the selection for feed efficiency in dairy cattle.

Thermoregulation at birth differs between piglets from two genetic lines divergent for residual feed intake

Thermoregulation is essential to piglets' neonatal survival. This study used infrared thermography (IRT) to assess thermoregulation abilities of piglets from two lines divergent for residual feed intake (RFI). At birth, morphology (weight, length, width and circumference), vigour (respiration, mobility and vocalisation), and rectal temperature were recorded from piglets of the 11th generation of the low RFI (LRFI, more efficient; n = 34) and the high RFI (HRFI, less efficient; n = 28) lines. Infrared thermography images were taken at 8, 15, 30 and 60 min post partum. Temperatures of the ear base and tip, and of the back (i.e. shoulders to rumps) were extracted (Thermacam Researcher Pro 2.0) and analysed with linear mixed models (SAS 9.4). Piglets had different average hourly weight gain (HRFI = 7.1 ± 1.3 g/h, LRFI = 3.6 ± 1.3 g/h; P < 0,001) but did not differ in morphology or vigour. All temperatures increased overtime. At birth, piglets' rectal temperature was correlated with the initial temperature of the ear base and the maximum back temperature (0.37 and 0.33, respectively; P < 0.05). High residual feed intake piglets had lower ear tip temperatures than LRFI piglets at 15 (24.7 ± 0.37 °C vs. 26.3 ± 0.36 °C, respectively; F1, 63.5 = 9.11, P < 0.005) and 30 min post partum (26.2 ± 0.47 °C vs. 27.6 ± 0.44 °C, respectively; F1, 66.9 = 4.52, P < 0.05). Moreover, thermal pattern of the ear tip differed between the two genetic lines. In conclusion, IRT allowed non-invasive assessment of piglets' thermoregulation abilities and indicated an influence of genetic selection for RFI on neonatal thermoregulation abilities.

Impact of prenatal maternal nutrition and parental residual feed intake (RFI) on mRNA abundance of metabolic drivers of growth and development in young Angus bulls

• Muscular, hepatic, and testicular MEF2A expression associated with feed efficiency • Longissimus MEF2A expression was also affected by prenatal maternal nutrition • Hepatic PCDH19 expression was increased in bulls exposed to low prenatal nutrition • Muscular/hepatic/testicular gene expression correlated with measures of intake • Muscular/hepatic/testicular gene expression correlated with final/trimmed weight Approximately 70% of the cost of beef production is impacted by feed utilization. Maximizing production efficiency of beef cattle requires not only genetic selection to maximize feeding efficiency (i.e. residual feed intake - RFI), but also adequate nutrition throughout all stages of growth and development to maximize productivity of growth and reproductive capacity, even during gestation. Nutrient restriction during gestation has been shown to negatively affect post-natal growth and development. This, when combined with efforts to minimize RFI, may significantly affect energy partitioning in the offspring and subsequently important performance traits. Therefore, we decided to investigate the impacts of prenatal under-nutrition during the first half of gestation, as well as selection for divergent RFI, upon gene expression in select tissues, including Longissimus thoracis (LT) and semimembranosus (SM) muscles, liver, and testis, in Angus bull progeny. The genes monitored in this study included metabolic drivers of animal growth, especially muscle growth and development, and those that were aspects of detoxification/immune function. The results showed that the mRNA abundance of protocadherin 19 [ PCDH19 ] in liver, and myocyte enhancer factor 2A [ MEF2A ] in LT muscle, was significantly higher in Low-diet (Ldiet), and Normal-diet (Ndiet) prenatal maternal diet groups, respectively. The results also showed that in all four tissues, expression of MEF2A was significantly higher in the Low-RFI (LRFI) group as compared to its High-RFI (HRFI) counterpart. We also reported correlations between gene expression in these four tissues with phenotypic measures of feed efficiency and body weight.

PSI-37 Post-weaning feed efficiency did not influence female fertility traits of commercial or Lowline Angus heifers

Abstract Feed costs represent ~50% of beef production costs making selection for improved efficiency without affecting female reproduction critical to the cow/calf sector. Objectives were to determine the relationship between post-weaning feed efficiency and female fertility in commercial (n = 19) and half-blood Lowline-influenced Angus heifers (n = 20). Yearling heifers were delivered to the CSU, Chico Farm cattle feeding unit 45-d post weaning and randomly assigned to one of three 7 x 18 m pens, equipped with GrowSafe feeding units. Heifers were given ad libitum access to water and a forage-based diet targeting 0.68 kg gain/d (TDN: 54%, CP: 14%, and NDF: 39.7%, on a DM basis) for 72-d. Feed efficiency measures included dry matter intake (DMI), feed conversion ratio (FCR) and residual feed intake (RFI). Heifer RFI was calculated as the difference between predicted DMI and actual DMI during the trial. Feed efficiency groups were identified as: 1) low RFI (0.5 SD above the RFI mean), 2) marginal RFI (+/- 0.5 SD about the RFI mean), and 3) high RFI (0.5 SD above the RFI mean). Serial weights were taken every 14-d to calculate average daily gain (ADG) and metabolic midweight (MMWT). Heifers were synchronized using a 14-d CIDR-PG protocol. Heifers received PG injection 16-d post-CIDR removal and were equipped with an estrous detection patch. Estrous behavior was observed morning and evening for 90-h. Heifers were artificially inseminated (AI) 12-h post-standing estrus and injected with 2 mL GnRH. Pregnancy determination via rectal palpation occurred 6-mos after initial AI. Reproductive measures included: first service conception (FSC), pregnancy rate (PR), and response to estrous synchronization (RES). Reproductive traits were analyzed using the GLM procedures of SPSS with a binary logistic response. Breed type and feed efficiency group were independent variables. Relationships among reproductive measures and performance were analyzed using logistic regression of SPSS, fitting the independent variables of ADG, DMI, and RFI. Traits FSC, PR, and RES did not differ among breed types or feed efficiency groups (P &amp;gt; 0.05) and DMI, ADG and RFI were not predictors of FSC, PR, nor RES (P &amp;gt; 0.05). Cumulatively, results indicate there is no relationship between feed efficiency and reproductive performance. Producers can select for low RFI to decrease feed costs without compromising reproductive performance.

PSI-36 Phenotypic Relationship of Feed Efficiency and Fertility in Angus and Red Angus Bulls

Abstract Recent advances in measuring feed intake improve selection for efficient beef bulls; however, such selection must not decrease bull fertility. Objectives herein were to determine the phenotypic relationship between feed efficiency and fertility traits in growing Angus (n = 14) and Red Angus (n = 14) bulls. Two feeding trials were conducted at the CSU, Chico University Farm in 2017 (87 d) and 2018 (84 d). Each year, bulls were randomly assigned to 7 x 18 m pens equipped with GrowSafe feed intake units and allowed ad libitum access to water and feed (CP: 15.6%, TDN: 56.22%, NDF: 52%, DM basis). Performance traits included: feed conversion ratio (FCR) and residual feed intake [RFI; measured as the difference between predicted dry matter intake (PDMI) and actual dry matter intake (DMI)], start weight (SWT), end weight (EWT), metabolic mid-weight (MMWT), residual gain and average daily gain (ADG). Breeding soundness exams (BSE) were conducted at 18 mo of age and included traits: scrotal circumference (SC), motility (MT), and morphology (MP). Residual feed intake was calculated by regressing DMI on ADG and MMWT. The RFI group was categorized as low (0.5 SD above the RFI mean), marginal (± 0.5 SD about the RFI mean), and high (0.5 SD above the RFI mean) by year. Data were analyzed using ANOVA, blocking on year-pen and fitting breed and RFI group as independent factors. Tukey pairwise contrasts were run. Motility among breeds and RFI group were analyzed using chi-square. Pearson correlations were calculated between growth, feed efficiency, and BSE measures of SC and MP. There were no differences (P &amp;gt; 0.05) among breeds nor RFI groups for SWT, EWT, MMWT, residual gain, SC, and MT. No interaction was detected between breed and RFI group with exception of MP (P = 0.049); specifically, low RFI Red Angus bulls had poor MP compared to marginal and high RFI groups (66.94 ± 6.87 vs. 87.43 ± 3.77 and 93.74 ± 5.48 %, respectively). Angus bulls were superior to Red Angus bulls in ADG (1.23 ± 0.04 vs. 1.06 ± 0.05 kg/d; P = 0.01), FCR (7.98 ± 0.31 vs. 9.18 ± 0.38; P = 0.04), and RFI (-0.24 ± 0.09 vs. 0.09 ± 0.11 kg DMI/d; P = 0.04). High and marginal RFI groups had greater DMI compared to low RFI group (10.40 ± 0.26 and 9.64 ± 0.18 kg/d vs. 8.31 ± 0.32 kg/d; P &amp;lt; 0.001). There were no significant phenotypic correlations between growth and efficiency measures with SC and MP (P &amp;gt; 0.05). Cumulatively, results indicate that SC and MT were not affected in efficient bulls.

229 The effects of direct-fed microbial with and without monensin plus tylan on performance, feed efficiency and feeding behavior patterns in feedlot steers

Abstract Objectives of this study were to evaluate the effects of DFM with and without Monensin plus Tylan on feed efficiency and feeding behavior patterns in steers. Crossbred steers (n = 125; BW = 303 kg) were randomly assigned to 1 of 4 treatments in a 2 x 2 factorial design: (1) control (no feed additives), (2) DFM only (25 g/d; Natur’s Way), (3) Monensin (40 g/ton) plus Tylan only (MON) and (4) DFM and MON. In pens with GrowSafe feedbunks, steers were fed the grower diet for 14 d and transitioned to a finisher diet on 16 d. During the grower/transition phase, MON-fed steers had 9.5% higher (P &amp;lt; 0.05) ADG and improved F:G (7.8 vs 8.94; P = 0.06) and RFI (-0.28 vs 0.27 kg/d; P &amp;lt; 0.01) vs CON-fed steers. DFM-fed steers had lower (P &amp;lt; 0.01) ADG, but similar F:G and RFI than CON-fed steers. Daily variances of bunk-visit event frequencies were reduced (P &amp;lt; 0.01) in MON- vs CON-fed steers. During the finisher period, MON x DFM interactions (P &amp;lt; 0.10) were observed for ADG and F:G. MON-fed steers had numerically improved F:G (5%) when DFM was excluded, but not when DFM was included. MON-fed steers had lower RFI (P &amp;lt; 0.01; -0.23 vs 0.23 kg/d), whereas DFM-fed steers had higher RFI (P &amp;lt; 0.01) compared to respective controls. MON-fed steers ate less (P &amp;lt; 0.01) DMI, spent 9% more (P &amp;lt; 0.05) time consuming meals and had 14% slower (P &amp;lt; 0.01) meal eating rate then CON-fed steers. The DFM did not positively affect feed efficiency. Although the magnitude of improvement in feed efficiency due to MON was small, results demonstrated that MON may minimize digestive upsets by reducing daily variation in feeding behavior during diet transition and slow meal-eating rate on high-grain diets.

PSXI-19 Investigating the Relationship Between Temperament and Performance Traits in Feedlot Cattle

Abstract Temperament in cattle, is defined as behavioral changes in response to humans or changes in the environment, and has been associated with reduced feed efficiency, reduced growth rate, and poor feedlot health. The objective of the study was to determine if temperament affected the performance, growth and health of feedlot cattle. One-hundred and thirty-one Angus x Simmental steers from a single ranch were sampled at a commercial feedlot in Chappell, NE. Blood samples for metabolite analysis, exit velocity, and blood lactate concentration for temperament classification were collected in addition to feedlot performance data and carcass quality measurements. The GLM and LSM procedures of SAS (SAS 9.4, 2014) were used to evaluate differences between temperament classifications. Pearson correlations were calculated between temperament and performance variables. Steers were divided into three exit velocity classifications, with fast animals (n = 27) having exit velocity greater than one standard deviation from the mean and slow animals (n = 26) having exit velocities lower than one standard deviation from the mean. Feed intake and behavior was monitored for 42 days with GrowSafe feed bunks and average daily gain, dry matter intake and residual feed intake calculated. There were significant differences between the temperament classifications of fast, medium and slow for both exit velocity and blood lactate (P &amp;lt; 0.0001), indicating there was a difference in responses from the classifications. Exit velocity had no effect on any of the growth parameters measured. There was a significant positive correlation between exit velocity and blood lactate (P &amp;lt; 0.0001). RFI was significantly correlated with exit velocity (P = 0. 051) and blood lactate (P &amp;lt; 0.05). This suggests that animals with higher RFI or less efficient animals had more flighty temperaments as determined by blood lactate and exit velocity.

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.

282 The Influence of RFI classification and cow age on body weight and body condition change, supplement intake and grazing behavior of beef cattle winter grazing mixed-grass rangelands

Abstract behavior of beef cattle winter grazing rangelands in North Central Montana. A herd of non-lactating commercial Angus cows, n = 205 (yr-1) and n = 203 (yr-2), ranging in age from 1 to 9 yr old, grazed rangeland pastures (586 ha) from mid-October to early January of 2018 and 2019. Cows were grouped into 6 age classes to evaluate the effects of RFI and age on average daily individual supplement intake, CV of supplement intake, and intake rate, as well as changes in body weight and body condition during an 84-day grazing period each year. Additionally, 30 cows were stratified by age and RFI and fitted with Lotek GPS collars each year to record distance traveled and time spent grazing. Change in cow weight differed by year where cows in yr-1 gained 26.3 ± 1.96 kg while cows in yr-2 lost 19.2 ± 1.96 kg during the 84-day grazing period (P &amp;lt; 0.01). Change in BCS exhibited an age × RFI interaction (P = 0.05); however, an analysis within age groups did not result in differences between RFI classifications (P ≥ 0.27). There was an interaction between RFI, age and year related to supplement intake expressed as g∙kg cow bw-1∙d-1 where in year 2, 4-yr-old high RFI cattle consumed less supplement than 4-yr-old low and average RFI cattle (P &amp;lt; 0.01). Supplement intake rate expressed as g∙min-1 also differed by year (P &amp;lt; 0.01), with cows in yr-1 consuming less supplement per minute than in yr-2 (29.9 ± 1.81 and 91.8 ± 1.87). There were no effects of RFI, cow age or year on time spent grazing (P ≥ 0.19) with cows averaging 6.1 ± 0.61 hrs per day grazing. In summary, cow age had an influence on supplement intake, change in weight and body condition, and grazing behavior, while RFI classification had minimal effects.

Muscle and liver metabolomic signatures associated with residual feed intake in Nellore cattle

Identification of those cattle genetics with superior feed efficiency is necessary to increase the productivity of the entire beef industry. The aim of this study was to investigate metabolites profiling in the liver and muscle to identify physiological changes in animals in the livestock system with low or high residual feed intake. Liver and muscle were collected after slaughter from Nellore males, with high and low residual feed intake (H-RFI, n = 10 and L-RFI, n = 10, respectively). Metabolites were extracted with cold methanol/water solution (4:3 v/v). Metabolomics analyses were performed by 1D 1H nuclear magnetic resonance. Metabolites were identified using Chenomx and analysed using MetaboAnalyst 4.0. The residual feed intake classification did not change most of animal performance traits; however, animals with lower residual feed intake presented greater carcass dressing, lower carcass fat deposition. Sixty-three compounds were identified in the liver and 31 in muscle. Coexpression network analysis was carried out and identified four metabolite network modules correlated with the phenotypic traits, indicating common metabolites with a variate important projection score that influences residual feed intake. Metabolites in liver samples was correlated with energy and protein metabolism and on muscle with fat metabolism. Differences on energetic metabolism, including of carbohydrate- and fat-correlated compounds, according to residual feed intake can be assessed by importance of concentration of citrate, isocitrate, glucose-6-phosphate, nicotinamide adenine dinucleotide + hydrogen and creatine phosphate (in liver) and choline, glycine, glycerol, malonate, glucose-6-phosphate and 3-hydroxybutyrate (in muscle). Moreover, differences on protein metabolism, can be assessed by importance of creatinine, glutamine, urea and creatine phosphate concentration in liver and creatinine, creatine, anserine and carnosine in muscle. Animals with low residual feed intake presented changes in energy production, represented by carbohydrate and fatty acid metabolites, and decreased carcass fat deposition and protein turnover.

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.

Predicting Cattle Grazing Behavior on Rangeland using Accelerometers

The objective was to determine if 3-axis accelerometers could be used to predict daily activity for cattle grazing rangeland. There were 48 Hereford × Angus 2-yr-old low- or high-residual feed intake (LRFI or HRFI) cows used in this 2-yr trial. Cattle grazed in 4 pasture treatments consisting of continuously grazed, control (CCON); continuously grazed, supplemented (CTRT); rotationally grazed, control (RCON); and rotationally grazed, supplemented pastures (RTRT). Three LRFI- and 3 HRFI-collared cows in each treatment had accelerometers mounted for 29 d in 2016 and 45 d in 2017, beginning mid-October. Grazing time (GT), resting time (RT), and walking time (WLK) were obtained for each cow by direct observation over 3 d each year and compared with accelerometer predicted behavior. In 2016, 1.6% of the days were rejected for halter-mounted accelerometers and 3.6% were rejected in 2017 for collar-mounted accelerometers. The GT and RT were more accurately predicted than was WLK with the percentage error of predicted against observed data being 11.94% for RT, 13.51% for GT, and 30.13% for WLK in 2017. Less observation data were available in 2016, but when considering other sampling periods for the same cows and halters, the error rate was 15.1% for RT, 19.3% for GT, and 52.6% for WLK. The accelerometers successfully identified patterns of grazing behavior and differentiated among climatic, grazing system, supplementation status, and residual feed intake classification influences on GT, RT, and WLK. In a more moderate climate year, HRFI cattle appeared to rest less (P < 0.08) and walk more (P < 0.07) than LRFI cattle. Similar patterns were observed for cattle in the CCON versus CTRT treatments, with supplemented cattle resting more (P < 0.05) and walking less (P < 0.05). Accelerometers appear to be effective in determining mechanistic adaptations in grazing behavior by beef cattle on range.

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

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

Relationships between feed efficiency and puberty in Bos taurus and Bos indicus-influenced replacement beef heifers.

The objective of this experiment was to investigate the relationship between residual feed intake (RFI) and parameters associated with reproductive efficiency in growing beef heifers. One hundred and seventy-nine replacement beef heifers (Bos taurus and Bos indicus-influenced) were enrolled in a retrospective cohort design. Heifers were assigned to a 70-d feed efficiency test, and results were utilized to retrospectively classify heifers into low (n = 51), medium (n = 66), or high (n = 62) RFI groups based on their individual RFI values. Blood samples were collected weekly throughout the feed efficiency test and breeding season, which were analyzed for plasma concentration of progesterone to determine age at puberty (PUB). By design, residual feed intake differed among RFI groups where high (1.21 ± 0.08 kg/d) had greater (P < 0.01) RFI than medium (0.00 ± 0.08 kg/d) and low RFI groups (-1.49 ± 0.09 kg/d), and medium had greater (P < 0.01) RFI than low RFI heifers. Yet, no differences were observed between breed types for RFI (P = 0.53). Average daily gain (ADG) differed between breed types where Bos taurus heifers had greater ADG (P = 0.02) than B. indicus-influenced heifers. Furthermore, ADG tended (P = 0.08) to differ among RFI groups, where medium RFI heifers tended to have reduced ADG compared with low and high RFI heifers. No differences were determined between breed types for gain-to-feed ratio (G:F; P = 0.20; however, G:F differed among RFI groups and was greater (P < 0.01) in low vs. high, and low vs. medium RFI heifers. The percentage of cycling heifers by the start of the breeding season differed (P = 0.03) by RFI group, where a greater percentage of low RFI heifers were cycling compared with high RFI heifers. A difference was determined on PUB between breed types (P = 0.03), where Bos taurus (393.40 ± 4.64 d) heifers had a reduced PUB compared with B. indicus-influenced (406.90 ± 5.07 d) heifers. In addition, PUB differed by RFI group where low (385.96 ± 6.20 d; P < 0.01) and medium (398.47 ± 5.47 d; P = 0.02) RFI heifers had a reduced PUB compared with High RFI heifers (416.03 ± 5.58 d). In conclusion, more feed efficient heifers attained PUB earlier than less feed efficient heifers. Therefore, selection of heifers for feed efficiency may positively impact reproductive performance of replacement beef heifers.

Correlations between feed intake, residual feed intake and methane emissions in Maternal Composite ewes at post weaning, hogget and adult ages

Sheep production in southern Australia (particularly south west Victoria) is based increasingly on the Maternal Composite ewe, a self-replacing stable crossbred. Breeding programs have focussed on maternal traits such as reproduction and lamb growth. Understanding the variability, range and correlations between the traits of residual feed intake (RFI), feed intake (dry matter intake, DMI), growth rate and methane (CH4) emissions within the Maternal Composite ewe flock is essential to development of selection parameters that improve feed efficiency and reduce environmental impact. Sheep and cattle with low RFI (more efficient) have been observed to produce less CH4 than animals with high RFI. Selecting for animals with improved RFI may enable producers to improve the enterprise productivity while decreasing greenhouse gas emissions.

Evaluating the association between feed efficiency and the fecal microbiota of early-life Duroc pigs using 16S rRNA sequencing

Improving the predication efficiency of porcine production performance at early stage will contribute to reducing the breeding and production costs. The intestinal microbiota had received plenty of attention in recent years due to their influence on host health and performance. The purpose of this study was to investigate the relationship between the fecal microbiota at early growth period and porcine feed efficiency (FE) under a commercial feeding environment. Ninety-one pigs were reordered according to the residual feed intake (RFI) values between day 90 on test and day 160 off test, 9 lowest RFI pigs and 9 highest RFI pigs were selected as the LRFI group and the HRFI group, respectively. Fecal samples from pigs in the early grower phase (day 80) were performed for microbial diversity, composition, and predicted functionality by using 16S rRNA sequencing. The results showed that no significant differences in microbial alpha diversity were observed between two RFI groups, whereas, some RFI-associated compositional differences were revealed. In particular, the microbiota of the LRFI group (more feed-efficient) had significantly higher levels of some members of Clostridiales and Bacteroidales (e.g., g_1_68 and g_norank_f_p_2534_18B5), which may promoted FE through protecting gut barrier function, compared with those of the HRFI pigs. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis found that the LRFI pigs were likely have microbiota with higher levels of amino acid metabolism. Moreover, redundancy analysis (RDA) showed that litter size, parity, and date of birth had significant effects on the bacterial community structure. These results improved our knowledge of the porcine early-life fecal microbiota and its potential link underlying RFI, which would be useful for future development of microbial biomarkers for predicting and improving porcine FE as well as investigation of targets for dietary strategies.