Records on 1,180 young Angus bulls and heifers involved in performance tests were used to estimate genetic phenotypic parameters for feed intake, efficiency, other postweaning traits. The mean age was 268 d at the start of test, which comprised 21-d adjustment 70-d test periods. Traits studied included 200-d weight, 400-d scrotal circumference, ultrasonic measurements rib rump fat depths longissimus muscle area, ADG, metabolic daily conversion ratio, residual intake. For all traits except...

Residual feed intake (RFI) is a measure of efficiency that independent level production, such as size and growth rate in beef cattle, thus useful new trait for studying the physiological mechanisms underlying variation efficiency. Five major processes are likely to contribute RFI, these being associated with feed, digestion metabolism (anabolism catabolism including body composition), physical activity, thermoregulation. Studies on Angus steers following divergent selection RFI estimated...

The optimum duration of test for measurement growth rate, feed intake, conversion, and residual intake was examined using postweaning weight data from 760 Angus, Hereford, Polled Shorthorn heifer Angus bull progeny 78 sires. Variance components, heritability, phenotypic genetic correlations, the efficiency selection shortened tests compared with a 119-d were used as criteria to assess length. results indicated that 35-d sufficient whereas 70-d required measure without compromising accuracy...

There is considerable individual animal variation in feed intake above and below that expected or predicted on the basis of size growth rate. This difference calculated as residual (or net) (RFI). Genetic RFI beef cattle exists both during (slaughter generation replacement females; heritability estimates since 1996 range from 0.16 to 0.43) adult (the breeding herd; one published estimate 0.23). Evidence shows selection for lower measured postweaning will lead a decrease by young cows, with...

Residual feed intake measures variation in independent of liveweight and gain. First generation steer progeny (n = 33) parents previously selected for low or high post-weaning residual were examined to determine metabolic processes contributing intake. Blood samples taken from the steers weaning through slaughter. These analysed key metabolites hormones. Total urine total faecal collections an animal-house experiment estimate dry matter digestibility, microbial protein production turnover....

A genome wide-association study for production traits in cattle was carried out using genotype data from the 10K Affymetrix (Santa Clara, CA) and 50K Illumina (San Diego, SNP chips. The results residual feed intake (RFI), BW, hip height 3 beef breed types (Bos indicus, Bos taurus, B. indicus × taurus), stature dairy cattle, are presented. aims were to discover associated with all studied, but especially RFI, further test consistency of effects across different populations types. analyzed...

Yearling Angus steer progeny of parents selected for low residual feed intake (RFI; high efficiency) or RFI (low were evaluated intake, growth and differences in body composition. is the difference between actual expected based on an animal’s size over a test period. Individual intakes grain content ration rates recorded 140 days then steers slaughtered measurement All internal organs non-carcass fat depots removed, weighed ground chemical analysis. Carcasses kept overnight chiller left half...

In the last 10 years, there have been 3 major research and development projects in Australia on efficiency of feed utilisation by beef cattle. The primary objective these has to examine individual animal variation its exploitation for genetic improvement results indicate that exists Australian herds, is moderately heritable potential reduce cost production through selection efficient These further developed industry application generation BREEDPLAN estimated breeding values net (or residual)...

Data on 185 Angus cows were used to study the effect of divergent selection for residual feed intake maternal productivity across 3 mating seasons, starting from 2000. The result 1 2.5 generations (mean 1.5), and differed in estimated breeding value by 0.8 kg/day. In general, lost subcutaneous fat (measured 2 times a year) during period when they nursing calves, gained thereafter. No significant line differences fatness observed except those measured at start 2000 (10.8 ± 0.4 v. 9.3 mm),...

Ruminants contribute 80% of the global livestock greenhouse gas (GHG) emissions mainly through production methane, a byproduct enteric microbial fermentation primarily in rumen. Hence, reducing methane is essential any GHG reduction strategy livestock. Data on 1,046 young bulls and heifers from 2 performance-recording research herds Angus cattle were analyzed to provide genetic phenotypic variance covariance estimates for traits examine interrelationships among these traits. The fed roughage...

Ruminants contribute up to 80% of greenhouse gas (GHG) emissions from livestock, and enteric methane production by ruminants is the main source these GHG emissions. Hence, reducing essential in any reduction strategy livestock. Data 2 performance-recording research herds Angus cattle were used evaluate a number measures that target (MPR) independent feed intake examine their phenotypic relationships with growth body composition. The data comprised 777 young bulls heifers fed roughage diet...

Residual feed intake (RFI) is calculated as the difference between an animal’s actual and its expected based on size growth over a specified test period. Following single generation of divergent selection for postweaning RFI, Angus steers × Hereford, Angus×Poll Hereford Shorthorn crossbred born in 1996 1997 were fed feedlot. Cohorts slaughtered at same age had attained similar (P>0.05) final liveweights: 467 kg selected low RFI (high efficiency; HE, n = 91) 459 high (low LE, 98). The...

Enteric methane emissions from beef cattle are a significant component of total greenhouse gas agriculture. The variation between in is partly genetic, whether measured as production, yield (methane production/DMI), or residual production (observed - expected production), with heritabilities ranging 0.19 to 0.29. This suggests could be reduced by selection. Given the high cost measuring individual cattle, genomic selection most feasible approach achieve this reduction emissions. We derived...

Methane (CH) is a product of enteric fermentation in ruminants, and it represents around 17% global CH emissions. There has been substantial effort from the livestock scientific community toward tools that can help reduce this percentage. One approach to select for lower emitting animals. To achieve this, accurate genetic parameters identification genomic basis traits are required. Therefore, objectives study were 1) perform genomewide association identify SNP associated with several Angus...

Respiration chambers are considered the reference method for quantifying daily CH4 production rate (MPR) and CO2 (CPR) of cattle; however, they expensive, labor intensive, cannot be used in environment, can to assess only a limited number animals. Alternative methods now available, including those that provide multiple short-term measures CO2, such as GreenFeed Emission Monitoring (GEM) system. This study was conducted information optimizing test procedures estimating MPR CPR cattle from...

Genetic improvement strategies in the past have concentrated on traits associated with outputs. Traits that directly affect input costs, such as those related to efficiency of feed utilisation, only recently started receive some attention. This paper examines current state knowledge, benefits and challenges genetic utilisation by livestock. Current information indicates existence variation moderate heritability for most all livestock species. However, there is a paucity relationships among...

Angus cattle that had been divergently selected for Low and High post-weaning residual feed intake (RFI) were used in two projects to evaluate early-life reproductive performance onset of puberty females. In the first project, data on 1999-born females (n = 64) evaluated weight, subcutaneous fat (P8 depth) over breeding cycles. These result 1.0–2.5 (mean 1.8) generations selection, mean (±s.e.) RFI –0.82 ± 0.19 kg/day 0.57 0.18 selection lines, respectively. second ultrasonography was scan...

The objective of the study was to evaluate associations among animal performance and methane emission traits under feedlot conditions in respiration chambers Angus cattle bred vary residual feed intake (RFI), which is a measure efficiency. Fifty-nine were tested for RFI, 41 had production recorded on an ad libitum grain-based ration feedlot, 59 restricted chambers, 57 roughage chambers. became older heavier as they went through different phases experiment, but their (expressed DMI) daily...

The records of 282 young beef bulls from eight breeds tested November 1981 to April 1987 at the Ellerslie Bull Test Station, Alberta, Canada, were used study variation in feed efficiency among performance-tested bulls. Considerable existed animals both residual metabolizable energy consumption and dry matter consumption. heritability estimates for 0.33 0.29, respectively. In addition, moderately correlated (r = 0.43) with conventional feed-to-gain ratio, indicating that ratio only accounted...

This study examined whether a single generation of divergent selection for residual feed intake was accompanied by differences in red and white blood cell parameters that could assist the early identification animals likely to perform well test intake. Two cohorts steer progeny born 1996 (n = 74) 1998 120) parents selected low (high efficiency) high (low were used. The steers grazed on pasture before feedlot entry subsequent test. Blood samples collected from cattle at day induction, all...