Inefficient Animals Research Articles

Occurrence Autosomal Mosaicism in Karan Fries Cattle and Murrah Buffalo with Poor Reproduction

Background: The present study was conducted at the Livestock Genome Analysis Laboratory (LGAL), ICAR-National Dairy Research Institute (NDRI), Karnal, Haryana, India, to explore, chromosomal anomalies in reproductively inefficient animals. Chromosomal abnormalities are deviations in normal genetic architecture and lead to disorders in bearer individuals. These can be both in number and structure of autosomes or sex chromosomes, usually inflict adverse effects on anatomy, survival and reproductive performance in domestic animals. Methods: Present report is on a female Murrah buffalo (Bubalus bubalis) and a Karan Fries cattle which were identified during a routine cytogenetic reproductively inefficient females at cattle yard, National Dairy Research Institute, Karnal. Metaphase chromosome preparations were prepared using standard lymphocyte culture method. Slides were stained with Giemsa and treated for R-banding using fluorochrome-photolysis-Giemsa technique (RB-FPG technique). Karyotypes were prepared and abnormal chromosome was identified. Result: Routine examination using Giemsa-stained slides revealed two cell lines with 60 and 61 chromosomal constitutions in cattle and 3 cell lines in buffalo. Among 182 metaphase plates examined were examined for Karan fries which revealed two types of chromosome configuration, the frequency of cells carrying 60 and 61 chromosomes was 83.5% and 16.5%, respectively. R banding technique distinguished autosome 16 responsible for mosaicism. Cytogenetic evaluation of 407 metaphase spreads of Murrah buffalo revealed three types of chromosome configurations, viz. 49, 50 and 51 all with XX and the overall frequency was 16.7, 76.7 and 6.6 per cent, respectively. The R- bandings confirmed autosome 11 both in monosomy (2n=49) and trisomy (2n=51), respectively. This unusual chromosomal number might have arisen due to non-disjunction during early stage of zygotic development of the buffalo and cattle.

Blood parameters as a possible indicator of feed efficiency in Nellore bulls

The objective of this study was to investigate the relationships between energy, protein, enzymatic metabolism, and residual feed intake (RFI) in purebred Nellore bulls. A total of 120 Nellore bulls, individually housed, underwent performance trials while being fed a high-concentrate diet. The study utilized data from the 10 most efficient, least efficient, and moderately efficient animals. Blood samples were collected via venipuncture for a complete blood count, and serum was analyzed for albumin, total protein, urea, creatinine, glucose, cholesterol, gamma GT, AST, and alkaline phosphatase. The data were subjected to a completely randomized design with three treatments and 10 replicates, and treatment means were compared using the Tukey test. Pearson's linear correlation analysis was performed. The most efficient animals demonstrated a 27.62% reduction in feed intake compared to the least efficient ones. No significant differences were observed in the serum biochemistry between different RFI classes. Inefficient animals exhibited elevated mean corpuscular hemoglobin (MCH), a red blood cell index, which correlated with RFI, gain-to-feed ratio, and dry matter intake (r = 0.46, 0.42, and -0.42, respectively). Hemoglobin concentration showed correlations with RFI and gain-to-feed ratio (r = 0.36, -0.41, respectively). These findings suggest potential variations in oxygen-carrying capacity. Red blood cell parameters could serve as biomarkers for identifying inefficient animals.

Challenges and strategies for reducing enteric methane emissions in sustainable animal production

Methane emissions in ruminants are influenced by various factors, including feed type and rumen microbial population. Mitigation strategies involve nutritional interventions, soil and plant management, and synergistic use of different forages. Effective management practices in pasture-based systems, such as monitoring forage mass and adjusting stocking rates, optimize intake and forage quality, resulting in reduced emissions and improved sustainability. Dry matter intake, diet profile, and quality significantly impact methane production, and interactions between microorganisms and ruminal ecology also influence emissions. While more efficient animals with lower feed intake may not necessarily emit less methane, understanding the differences in methanogenic profiles between efficient and inefficient animals is crucial and requires further investigation. Animal genotype is another factor influencing emissions. Comprehensive research considering diet, production, and farming systems is needed to develop effective strategies and achieve significant methane emission reductions

Evaluation of the Links between Lamb Feed Efficiency and Rumen and Plasma Metabolomic Data

Feed efficiency is one of the keystones that could help make animal production less costly and more environmentally friendly. Residual feed intake (RFI) is a widely used criterion to measure feed efficiency by regressing intake on the main energy sinks. We investigated rumen and plasma metabolomic data on Romane male lambs that had been genetically selected for either feed efficiency (line rfi−) or inefficiency (line rfi+). These investigations were conducted both during the growth phase under a 100% concentrate diet and later on under a mixed diet to identify differential metabolite expression and to link it to biological phenomena that could explain differences in feed efficiency. Nuclear magnetic resonance (NMR) data were analyzed using partial least squares discriminant analysis (PLS-DA), and correlations between metabolites’ relative concentrations were estimated to identify relationships between them. High levels of plasma citrate and malate were associated with genetically efficient animals, while high levels of amino acids such as L-threonine, L-serine, and L-leucine as well as beta-hydroxyisovalerate were associated with genetically inefficient animals under both diets. The two divergent lines could not be discriminated using rumen metabolites. Based on phenotypic residual feed intake (RFI), efficient and inefficient animals were discriminated using plasma metabolites determined under a 100% concentrate diet, but no discrimination was observed with plasma metabolites under a mixed diet or with rumen metabolites regardless of diet. Plasma amino acids, citrate, and malate were the most discriminant metabolites, suggesting that protein turnover and the mitochondrial production of energy could be the main phenomena that differ between efficient and inefficient Romane lambs.

Skeletal Muscle Expression of Actinin-3 (ACTN3) in Relation to Feed Efficiency Phenotype of F2 Bos indicus - Bos taurus Steers.

In this study, actinin-3 (ACTN3) gene expression was investigated in relation to the feed efficiency phenotype in Bos indicus - Bos taurus crossbred steers. A measure of relative feed efficiency based on residual feed intake relative to predictions from the NRC beef cattle model was analyzed by the use of a mixed linear model that included sire and family nested within sire as fixed effects and age, animal type, sex, condition, and breed as random effects for 173 F2 Nellore-Angus steers. Based on these residual intake observations, individuals were ranked from most efficient to least efficient. Skeletal muscle samples were analyzed from 54 steers in three groups of 18 (high efficiency, low efficiency, and a statistically average group). ACTN3, which encodes a muscle-specific structural protein, was previously identified as a candidate gene from a microarray analysis of RNA extracted from muscle samples obtained from a subset of steers from each of these three efficiency groups. The expression of ACTN3 was evaluated by quantitative reverse transcriptase PCR analysis. The expression of ACTN3 in skeletal muscle was 1.6-fold greater in the inefficient steer group than in the efficient group (p = 0.007). In addition to expression measurements, blocks of SNP haplotypes were assessed for breed or parent of origin effects. A maternal effect was observed for ACTN3 inheritance, indicating that a maternal B. indicus block conferred improved residual feed efficiency relative to the B. taurus copy (p = 0.03). A SNP haplotype analysis was also conducted for m-calpain (CAPN2) and fibronectin 1 (FN1), and a significant breed effect was observed for both genes, with B. indicus and B. taurus alleles each conferring favorable efficiency when inherited maternally (p = 0.03 and p = 0.04). Because the ACTN3 structural protein is specific to fast-twitch (type II) muscle fibers and not present in slow-twitch muscle fibers (type I), muscle samples used for expression analysis were also assayed for fiber type ratio (type II/type I). Inefficient animals had a fast fiber type ratio 1.8-fold greater than the efficient animals (p = 0.027). Because these fiber-types exhibit different metabolic profiles, we hypothesize that animals with a greater proportion of fast-twitch muscle fibers are also less feed efficient.

Identifying active rumen epithelial associated bacteria and archaea in beef cattle divergent in feed efficiency using total RNA-seq.

To date, the role of ruminal epithelial attached microbiota in cattle feed efficiency is undefined. In this study, we aimed to characterize transcriptionally active bacteria and archaea attached to the rumen epithelial wall and to determine whether they differ in cattle with varied feed efficiency. RNA-sequencing was performed to obtain the rumen epithelial transcriptomes from 9 of the most efficient (low RFI) and 9 of the most inefficient (high RFI) animals. The bacteria and archaea 16S rRNA transcripts were identified using an in-house developed pipeline, enriched from filtered reads that did not map to the bovine genome. Archaea from unclassified genera belonging to the Euryarchaeota phylum showed the most activity on the rumen epithelium of low RFI (81.3±1.9%) and high RFI (76.4±3.0%) steers. Bacteria from the Succinivibrionaceae family showed the greatest activity of bacteria on the low RFI (28.7±9.0%) and high RFI (33.9±8.8%) epithelium. Of the bacterial families, Campylobacteraceae and Neisseriaceae had significantly greater activity on the low RFI epithelium (p<0.05) and are known to play a role in oxygen scavenging. Greater activity of rumen epithelial attached oxygen scavenging bacteria may provide more optimal feed fermentation conditions, which contributes to high fermentation efficiency in the rumen.

Meat quality and lipid profile of intramuscular fat of Texel crossbred lambs classified by residual intake and gain

Context Many indices of feed efficiency for livestock have been proposed, but most are associated with differences in body composition and consequently affect meat quality. Aims This study aimed to assess meat quality and lipid profile of intramuscular fat of Texel crossbred lambs classified by residual intake and gain (RIG). Methods Seventy-seven non-castrated male Texel crossbred lambs (1/4 Pantaneira and 3/4 Texel) were assessed in a 2-year study. First year: Forty-seven lambs with initial bodyweight of 29.9 ± 5.5 kg. Second year: Thirty lambs with an initial bodyweight of 22.4 ± 3.3 kg. Lambs were confined in individual stalls for 70 days for the assessment of individual dry matter intake and average daily gain, being then slaughtered. The muscle Longissimus lumborum was removed for analyses. The RIG was obtained by: RIG = (−1 × residual feed intake) + residual gain. The data of meat quality and lipid profile from both years were grouped and analysed in a completely randomised design. Animals were classified into three RIG classes based on the s.d. of RIG variable. Efficient (n = 20) and inefficient (n = 22) animals were classified adopting ± 0.5 s.d. from RIG mean, and animals between these two groups were classified as intermediate (n = 35). Key results No significant differences were observed between RIG classes regarding instrumental characteristics and proximate composition of the Longissimus lumborum muscle. We observed no differences between RIG classes for concentrations of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA), as well as for the total sum of SFA, MUFA, and PUFA of intramuscular fat, with 40.9, 54.1, and 5.1% of total FA, respectively. The MUFA:SFA ratio, PUFA:SFA ratio, atherogenic and thrombogenic index were also not influenced by RIG classes. Conclusions There were no differences in meat quality and lipid profile of intramuscular fat between animals classified based on RIG. Implications Improvements provided by using RIG to identify efficient and faster-growing lambs could assist in reducing feed and labour investments in the production system through an early slaughter without having negative impacts on meat quality.

FABP1 and SLC2A5 expression levels affect feed efficiency-related traits

Improving the efficiency of production to reduce the environmental footprints is pivotal to the sustainability of livestock systems. Despite the advances in cattle feed efficiency (FE) measurement and identification of potential mechanisms involved, much is still unclear regarding the genetic and biological basis of this trait. Nevertheless, lipid and carbohydrate metabolism have been outlined as important in determining efficient and inefficient animals. To address the role of genes partaking in these processes and previously involved with residual feed intake (RFI), we carried out a liver expression profile in Nelore steers (n = 83). Six target genes (FABP1, FADS2, PPP1R26, RGS2, SLC2A5, and UCP2) were measured by qPCR analysis. A general linear mixed model approach was applied to associate them with dry matter intake (DMI), body weight (BW), metabolic BW (MBW, kg), DMI as a percentage of BW (DMI%BW), and average daily gain (ADG, kg/d). Residual feed intake (RFI), feed conversion ratio (FCR), feed efficiency (FE), Kleiber index (KI), and relative growth rate (RGR) were also evaluated. Our results support that increased expression of FABP1 gene was associated with enhanced values for RFI and DMI. Likewise, higher expression level of SLC2A5 was related to higher KI and RGR. There was no phenotypic correlation between RFI and ADG, BW, and MBW. The positive correlations between FABP1 and SLC2A5, and between FABP1 and FADS2 gene expression suggest a putative co-regulation affecting feed efficiency phenotypes.

Residual intake and gain for the evaluation of performance, non-carcass components, and carcass characteristics of confined crossbred Texel lambs

ABSTRACT We evaluated performance, non-carcass components, and carcass characteristics of crossbred Texel lambs in different categories of residual intake and gain (RIG). We assessed 77 crossbred (¼ Pantaneira and ¾ Texel) non-castrated animals in two study phases. The first phase included 47 lambs with an initial average weight of 29.9±5.5 kg, and the second phase included 30 lambs with initial average weight of 22.4±3.3 kg. Dry matter intake (DMI) and average daily gain (ADG) were evaluated for 70 days. Animals were divided into three groups in terms of efficiency: efficient (high RIG), intermediate (medium RIG), or inefficient (low RIG), based on the standard deviation of the mean for the RIG variable. We measured the yield of non-carcass components, carcass characteristics, and yield of meat cuts. Efficiency group had no association with DMI, nor with initial and final body weights of the animals. The ADG of efficient (0.310 kg day−1) and intermediate (0.290 kg day−1) animals was greater than observed in inefficient (0.260 kg day−1) animals. Lambs in the efficient and intermediate groups had significantly higher levels of all efficiency indicators evaluated. Efficient and intermediate animals yielded significantly more wool/skin in comparison with lambs in the inefficient group. Animals with high RIG also had lower relative weight of testicles/scrotal sac in comparison with inefficient animals. Fat deposition in the omentum and mesentery as well as total fat were decreased in efficient animals. No significant differences occurred among groups regarding carcass characteristics and yield of meat cuts. The RIG index allows for the identification of lambs with higher growth rates and greater wool/skin yield and lower proportion of visceral fat.

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.

Interrelations between the rumen microbiota and production, behavioral, rumen fermentation, metabolic, and immunological attributes of dairy cows

Different studies have shown a strong correlation between the rumen microbiome and a range of production traits (e.g., feed efficiency, milk yield and components) in dairy cows. Underlying dynamics concerning cause and effect are, however, still widely unknown and warrant further investigation. The aim of the current study was to describe possible functional interrelations and pathways using a large set of variables describing the production, the metabolic and immunological state, as well as the rumen microbiome and fermentation characteristics of dairy cows in early lactation (n = 36, 56 ± 3 d in milk). It was further hypothesized that the feed intake-associated behavior may influence the ruminal fermentation pattern, and a set of variables describing these individual animal attributes was included. Principal component analysis as well as Spearman's rank correlations were conducted including a total of 265 variables. The attained plots describe several well-known associations between metabolic, immunological, and production traits. Main drivers of variance within the data set included milk production and efficiency as well as rumen fermentation and microbiome diversity attributes, whereas behavioral, metabolic, and immunological variables did not exhibit any strong interrelations with the other variables. The previously well-documented strong correlation of production traits with distinct prokaryote groups was confirmed. This mainly included a negative correlation of operational taxonomic units ascribed to the Prevotella genus with milk and fat yield and feed efficiency. A central role of the animals' feed intake behavior in this context could not be affirmed. Furthermore, different methodological and interpretability aspects concerning the microbiome analysis by 16S rRNA gene sequencing, such as the discrepancy between taxonomic classification and functional communality, as well as the comparability with other studies, are discussed. We concluded that, to further investigate the driving force that causes the difference between efficient and inefficient animals, studies including more sophisticated methods to describe phenotypical traits of the host (e.g., rumen physiology, metabolic and genetic aspects) as well as the rumen microbiome (e.g., metagenome, metatranscriptome, metaproteome, and metabolome analysis) are needed.

Sheep residual feed intake and feeding behaviour: are ‘nibblers’ or ‘binge eaters’ more efficient?

Efficient liveweight gain is an important component of profitable livestock systems. In cattle, studies of residual feed intake (RFI) suggest that there are behavioural differences between efficient and inefficient animals; more efficient animals have less frequent, larger feed events. There is limited understanding of the association between feeding behaviour and feed conversion efficiency (measured as RFI) in sheep. We hypothesised that more efficient sheep would have lower daily number of meals but larger meal size than would less efficient sheep and that feeding behaviour would be repeatable between measurements conducted using the same sheep at different ages. Feeding behaviour was monitored at post-weaning (average 311 days) and hogget (average 533 days) age in a single cohort of maternal composite 2014-born ewes undergoing feed-efficiency testing. Feed intake (kg/day) and daily feeding behaviour (meal number, meal size and eating rate) were recorded by using automated feeders. Feed intake was recorded daily for a minimum of 40 days (mean 41 days), following a 14-day adaptation period. Animals were fed a pelleted hay-based diet, with liveweight measured three times per week. At both ages of measurement, a positive (P &lt; 0.01) linear relationship was established between average daily number of meals and RFI. In these cohorts, as daily number of meals increased, RFI became more positive (less efficient). Meal size (kg DM) was also related to RFI (P &lt; 0.05) when measured at the hogget age, with meal size decreasing with an increasing RFI (less efficient animals had smaller meals). These analyses suggest that sheep feeding behaviour, and in particular daily meal number, is associated with feed efficiency.

Feed efficiency phenotypes in lambs involve changes in ruminal, colonic, and small-intestine-located microbiota.

Several studies have revealed differences in rumen-located microbes between greatly efficient and inefficient animals; however, how the microbiota vary in the hind gastrointestinal tract (GIT) has only been sparsely explored and how they vary in the small intestine remains to be determined. We therefore sampled the microbiota of the duodenum, jejunum, ileum, colon, and colorectally-obtained feces, in addition to the rumen of 12 lambs that, in a residual feed intake trial, were found to be at either extreme of feed efficiency phenotypes. The 16S rRNA gene (V3-V4 region) profiles of all samples were analyzed and revealed unique microbiota in all GIT locations except the jejunum and ileum (ANOSIM > 0.2, < 0.001). Measures of β-diversity revealed greater dissimilarity between more anatomically distant GIT locations (e.g., Rumen-Duodenum, ANOSIM = 0.365, < 0.001; Rumen-Colon, ANOSIM = 1, < 0.001) with the nearest distal region typically more similar than the nearest proximal location. The relative abundances of 13 operational taxonomic units (OTUs) from the duodenum, jejunum, colon, and feces, as well as the rumen, differed between efficient and inefficient animals (Bonferroni corrected, < 0.05), while another 2 OTUs trended toward significance. These OTUs were classified as taxa with known roles in fibrolysis (Fibrobacteres, Ruminococcaceae, and Saccharofermentans) and others that are commonly associated with health (Bifidobacteriaceae, and Christensenellaceae) and dysbiosis (Proteobacteria). Our findings show biospatial delineations of microbiota throughout the GIT and suggest that feed efficiency extends beyond the rumen, transcending these regions, and involves increases in both rumen- and colon-located fibrolytic taxa, increases in bifidobacterial species in the small intestine, and reductions in small intestine and distal GIT-located Proteobacteria.

Feed efficiency indexes and their relationships with carcass, non-carcass and meat quality traits in Nellore steers

Five hundred and seventy-five Nellore steers were evaluated for residual feed intake and residual feed intake and gain and their relationships between carcass, non-carcass and meat quality traits. RFI was measured by the difference between observed and predicted dry matter intake and RIG was obtained by the sum of −1*RFI and residual gain. Efficient and inefficient animals were classified adopting ±0.5 standard deviations from RFI and RIG mean. A mixed model was used including RFI or RIG and contemporary group as fixed effects, initial age as covariate and sire and experimental period as random effects, testing the significance of the regression slope for each evaluated trait. RIG was positively related to longissimus muscle area. Efficient-RFI animals had lower liver and internal fat proportions compared to inefficient-RFI animals. Efficient-RFI and efficient-RIG animals had 11.8% and 11.2% lower extracted intramuscular fat, compared to inefficient-RFI and inefficient-RIG animals, respectively. Efficient-RFI animals had tougher meat compared to inefficient-RFI animals.

Relationship of efficiency indices with performance, heart rate, oxygen consumption, blood parameters, and estimated heat production in Nellore steers.

The objective of this study was to examine the relationship of efficiency indices with performance, heart rate, oxygen consumption, blood parameters, and estimated heat production (EHP) in Nellore steers. Eighteen steers were individually lot-fed diets of 2.7 Mcal ME/kg DM for 84 d. Estimated heat production was determined using oxygen pulse (OP) methodology, in which heart rate (HR) was monitored for 4 consecutive days. Oxygen pulse was obtained by simultaneously measuring HR and oxygen consumption during a 10- to 15-min period. Efficiency traits studied were feed efficiency (G:F) and residual feed intake (RFI) obtained by regression of DMI in relation to ADG and midtest metabolic BW (RFI). Alternatively, RFI was also obtained based on equations reported by the NRC's to estimate individual requirement and DMI (RFI calculated by the NRC [1996] equation [RFI]). The slope of the regression equation and its significance was used to evaluate the effect of efficiency indices (RFI, RFI, or G:F) on the traits studied. A mixed model was used considering RFI, RFI, or G:F and pen type as fixed effects and initial age as a covariate. For HR and EHP variables, day was included as a random effect. There was no relationship between efficiency indices and back fat depth measured by ultrasound or daily HR and EHP ( > 0.05). Because G:F is obtained in relation to BW, the slope of G:F was positive and significant ( < 0.05). Regardless of the method used, efficient steers had lower DMI ( < 0.05). The initial LM area was indirectly related to RFI and RFI ( < 0.05); however, the final muscle area was related to only RFI. Oxygen consumption per beat was not related to G:F; however, it was lower for RFI- and RFI-efficient steers, and consequently, oxygen volume (mL·min·kg) and OP (μL O·beat·kg) were also lower ( < 0.05). Blood parameters were not related to RFI and RFI ( > 0.05); however, G:F-efficient steers showed lower hematocrit and hemoglobin concentrations ( < 0.05). Differences in EHP between efficient and inefficient animals were not directly detected. Nevertheless, differences in oxygen consumption and OP were detected, indicating that the OP methodology may be useful to predict growth efficiency.

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake (RFI) offered contrasting diets.

BackgroundMethane (CH4) emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency. The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake (RFI) while offered (i) a low energy high forage (HF) diet followed by (ii) a high energy low forage (LF) diet. Ruminal fluid was collected from 14 high (H) and 14 low (L) RFI animals across both dietary periods. Quantitative real time PCR (qRT-PCR) analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes. Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance, rumen fermentation variables and diet digestibility.ResultsAbundance of methanogens, did not differ between RFI phenotypes. However, relative abundance of total and specific methanogen species was affected (P < 0.05) by diet type, with greater abundance observed while animals were offered the LF compared to the HF diet.ConclusionsThese findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH4 emissions between efficient and inefficient animals, however dietary manipulation can influence the abundance of total and specific methanogen species.

Thermoregulatory differences in lactating dairy cattle classed as efficient or inefficient based on residual feed intake

It is suggested that one-third of the inter-animal differences in efficiency is explained by differences in digestion, heat production, body composition and activity; while the remaining variation is the result of energy expenditure due to biological processes such as ion pumps and mitochondrial function. Inefficient animals may be wasting energy on inefficient processes resulting in increased heat production that may be reflected by differences in skin and core temperature. While the association between heat production and residual feed intake (RFI) has been touched on, it is yet to be fully elucidated. It is hypothesised that more efficient animals will expend less energy as heat, which will be reflected by differences in core and skin temperature measures. Fifty-four primiparous, Holstein-Friesian cows previously assessed for RFI (26 inefficient/high RFI, 28 efficient/low RFI) were selected and drafted into outdoor holding yards for measurements on two occasions (once during lactation and once during the non-lactating ‘dry’ period). Measures of body temperature were obtained using an infrared (IR) camera to obtain skin (surface) temperatures at multiple locations [muzzle, eye, jaw, ear, leg (front and back), rump, shoulder, teat, udder, side and tail] and rectal temperatures were measured using a digital thermometer. Respiration rates (RR) were obtained by counting the number of flank movements in 1 min. A subset of 16 cows (8 efficient and 8 inefficient) were utilised for further IR imagery in an undercover environment (to eliminate the influences of external environments). Skin temperature measurement obtained using an IR camera during the outdoor period demonstrated that inefficient cows had higher (0.65°C) teat temperatures (P = 0.05). Rectal temperature and RR were not influenced by efficiency group. When IR images were obtained undercover inefficient cows tended to have higher shoulder (0.85°C) and neck (0.98°C) temperatures than efficient cows (P &lt; 0.087); while udder temperature was significantly greater (1.61°C) for inefficient than efficient cows (P = 0.018). These data indicate that some of the differences in efficiency may be attributed to differences in thermoregulation, as reflected by differences in skin (but not core) temperature and that IR imagery is a suitable method for determining these differences in a non-invasive manner. Further research is required to further establish these relationships, and the measurement of skin temperatures should be undertaken indoors to eliminate external environmental influences.

Rumen Methanogenic Genotypes Differ in Abundance According to Host Residual Feed Intake Phenotype and Diet Type

Methane is an undesirable end product of rumen fermentative activity because of associated environmental impacts and reduced host feed efficiency. Our study characterized the rumen microbial methanogenic community in beef cattle divergently selected for phenotypic residual feed intake (RFI) while offered a high-forage (HF) diet followed by a low-forage (LF) diet. Rumen fluid was collected from 14 high-RFI (HRFI) and 14 low-RFI (LRFI) animals at the end of both dietary periods. 16S rRNA gene clone libraries were used, and methanogen-specific tag-encoded pyrosequencing was carried out on the samples. We found that Methanobrevibacter spp. are the dominant methanogens in the rumen, with Methanobrevibacter smithii being the most abundant species. Differences in the abundance of Methanobrevibacter smithii and Methanosphaera stadtmanae genotypes were detected in the rumen of animals offered the LF compared to the HF diet while the abundance of Methanobrevibacter smithii genotypes was different between HRFI and LRFI animals irrespective of diet. Our results demonstrate that while a core group of methanogen operational taxonomic units (OTUs) exist across diet and phenotype, significant differences were observed in the distribution of genotypes within those OTUs. These changes in genotype abundance may contribute to the observed differences in methane emissions between efficient and inefficient animals.

Relationships between residual feed intake, average daily gain, and feeding behavior in growing dairy heifers

Residual feed intake (RFI) is a measure of an individual’s efficiency in utilizing feed for maintenance and production during growth or lactation, and is defined as the difference between the actual and predicted feed intake of that individual. The objective of this study was to relate RFI to feeding behavior and to identify behavioral differences between animals with divergent RFI. The intakes and body weight (BW) of 1,049 growing dairy heifers (aged 5–9mo; 195±25.8kg of BW) in 5 cohorts were measured for 42 to 49d to ascertain individual RFI. Animals were housed in an outdoor feeding facility comprising 28 pens, each with 8 animals and 1 feeder per pen, and were fed a dried, cubed alfalfa diet. This forage diet was chosen because most dairy cows in New Zealand are grazed on ryegrass-dominant pastures, without grain or concentrates. An electronic feed monitoring system measured the intake and feeding behavior of individuals. Feeding behavior was summarized as daily intake, daily feeding duration, meal frequency, feeding rate, meal size, meal duration, and temporal feeding patterns. The RFI was moderately to strongly correlated with intake in all cohorts (r=0.54–0.74), indicating that efficient animals ate less than inefficient animals, but relationships with feeding behavior traits (meal frequency, feeding duration, and feeding rate) were weak (r=0.14–0.26), indicating that feeding behavior cannot reliably predict RFI in growing dairy heifers. Comparison of the extremes of RFI (10% most and 10% least efficient) demonstrated similar BW and average daily gain for both groups, but efficient animals ate less; had fewer, longer meals; shorter daily feeding duration; and ate more slowly than the least-efficient animals. These groups also differed in their feeding patterns over 24h, with the most efficient animals eating less and having fewer meals during daylight (0600 to 2100h), especially during the afternoon (1200 to 1800h), but ate for a longer time during the night (0000–0600h) than the least-efficient animals. In summary, correlations between RFI and feeding behavior were weak. Small differences in feeding behavior were observed between the most- and least-efficient animals but adverse behavioral effects associated with such selection in growing dairy heifers are unlikely.