Rump Fat Thickness Research Articles

Correlations of visual scores, carcass traits, feed efficiency and retail product yield in Nellore cattle

The growing use of visual scores (VS) and ultrasound (US) for carcass evaluation in breeding programs, calls for a knowledge of the relationships between these traits and other relevant characteristics, such as feed efficiency and production of commercial cuts. The objective of this study was to evaluate correlations between body visual scores and carcass traits identified by ultrasound (US) and feed efficiency (FE), carcass weight (HCW), dressing percentage (DP) and retail product yield (RPY) in beef cattle. Nellore cattle (male), 42 non-castrated [NCAST] and 44 castrated [CAST]) were evaluated by both VS and US, at the postweaning (15-month old) and finishing phases (21-month old). Visual scores of conformation (C), precocity (P) and muscling (M) were assessed and the backfat thickness (UBFT), rump fat thickness (URFT) and ribeye area (UREA) were measured by ultrasound. Gain-to-feed (G:F) ratio and residual feed intake (RFI) were measured in feedlot. Hot carcass weight, DP and RPY were determined at harvest. Non-castrated cattle had greater HCW and RPY but lower UBFT and URFT than CAST. Postweaning VS and US were poorly correlated with FE in both sexual conditions. Finishing VS were negatively correlated with G:F in CAST and finishing URFT was negatively correlated with RPY in NCAST. The relationship of VS and US with feed efficiency and meat yield is affected by age at the date of evaluation and by castration. Feed efficiency is not related to the yield of meat cuts in Nellore cattle

Genetic variations in the leptin gene associated with growth and carcass traits in Nellore cattle

The aim of the study was to detect polymorphisms in the leptin gene and to determine the association of these polymorphisms with growth and carcass traits in Nellore cattle. The single nucleotide polymorphisms (SNPs) -1457 (AJ571671:g.-1457A>G) and A59V (AF536174.1:g. 321C>T), as well as the microsatellite BM1500 (3.9 kb downstream), were genotyped. The measures of body weight and ultrasound examinations (rib eye area, back, and rump fat thickness) were performed in 3 different periods of animal management. During the first period, the animals were fed with grass and mineralized salt ad libitum. In the second period, they received grass and concentrate, and in the third, only concentrate. After the slaughter of animals, data were collected for classification and typification of carcasses. No significant association was found between the variables assessed and SNP -1457. Conversely, SNP A59V was associated with rump fat thickness and muscle color post-slaughter. BM1500 was associated with rump fat thickness in the first period (pre-slaughter), subcutaneous fat thickness in the second, weight of the animals in the third, and length of the carcass after slaughter. These results suggest that SNP A59V and the microsatellite BM1500 might be useful for marker-assisted selection in Nellore cattle.

Development and Body Composition of Quarter Horse Foals during Nursing

The monitoring and development of foals, based on biometric indices, and the determination of body composition could be important for genetic improvement and the elaboration of nutritional plans for horses. Considering that little information was available, the aim of the present study was to assess the growth and determine the body composition of suckling Quarter Horse foals. Animals (n = 46) of both sexes were monitored monthly from birth until the fifth month of age, using an ultrasound device and the following measurements: Wither Height (WH); Chest Perimeter (CP); Cannon Bone Circumference (CBC) Cannon Bone Girth (CG); Body Mass (BM); and Rump Fat Thickness (RFT). These tests determined the Fat-Free Mass (FFM), BM, Fat Percentage (FP) and Fat Thickness (FT). The data were analyzed using ANOVA and Tukey’s test, with differences considered statistically significant when P ≤ 0.05. The results demonstrated that the parameters analyzed changed significantly during the study period. The BM was ~41 at birth and ~177 kg at the point of weaning. Conversely, the FM was ~3.8 at birth and 18.1 kg at the point of weaning. The FFM was ~37 and ~160 kg at the time of birth and weaning, respectively. The FP varied from 9.3 at birth to 9.54 at weaning. The mean FT was ~1.39 and ~1.91 cm at birth and weaning, respectively. The WH measured ~91 at birth and 116 cm at weaning. In conclusion, suckling foals gain BM quickly from the time of birth to the time of weaning. The main cause of this gain is FFM. Therefore, due to the significant changes in the parameters studied herein, it is important to monitor these values in order to prevent nutritional imbalances.

Influence of supplementation with corn dried distillers grains plus solubles to growing calves fed medium-quality hay on growth performance and feeding behavior1

To determine the effect of increasing supplementation of corn dried distillers grains plus solubles (DDGS) on growth performance and feeding behavior, 70 steer calves (287 ± 10 kg of BW) were blocked by BW to 3 pens equipped with Insentec feeders. For 84 d, calves were fed medium-quality grass/legume hay offered for ad libitum intake and provided 1 of 3 dietary supplemental treatments (n = 7 or 8 steers per treatment within each pen; n = 23 or 24 per treatment): 1) nothing, 2) DDGS at 0.5% of BW daily (DM basis), and 3) DDGS at 1% of BW daily (DM basis). Hay intake (kg/d and % of BW daily) decreased linearly (P < 0.001) as DDGS supplementation increased. Total DMI (kg/d and % of BW) increased linearly (P < 0.001) with DDGS supplementation. Average daily gain and gain efficiency (G:F) responded quadratically (P ≤ 0.006) as G:F increased to a lesser extent when DDGS supplementation increased from 0.5 to 1% than from 0 to 0.5%. Meals (number per day) and time eating per meal for hay and total diet decreased linearly (P ≤ 0.006) with increasing DDGS supplementation. Time eating per day for hay responded quadratically (P < 0.001) and decreased to a greater extent when increasing from 0 to 0.5% DDGS supplementation than from 0.5 to 1% DDGS. Feed intake per minute (eating rate) for hay and total diet increased linearly (P ≤ 0.05) with increasing DDGS supplementation. On d 84, LM area, back fat thickness, and rump fat thickness increased linearly (P ≤ 0.006) with increasing DDGS supplementation. There were significant day × treatment interactions (P < 0.001) for plasma glucose and urea-N concentrations. Glucose did not change over the feeding period in control steers but increased in both supplemented groups. Urea-N decreased for control steers over the feeding period whereas urea-N increased in supplemented steers. In conclusion, supplementation of DDGS in amounts of 0.5 or 1% of BW daily can be used to reduce hay intake and improve ADG and G:F in growing steers fed medium-quality hay. Additionally, DDGS supplementation alters feeding behavior.

Blood cell and metabolic profile of Nellore bulls and their correlations with residual feed intake and feed conversion ratio

Due to the potential metabolic changes related to the residual feed intake (RFI), this study investigated the correlation of traditional RFI (RFI1), RFI adjusted for final rump fat thickness (RFI2) and feed conversion ratio (FCR) with the metabolic and blood profiles, as well as determined the possible different classes of RFI1 and RFI2. For this purpose, 46 Nellore bulls, 22 month-old and 411kg of weight at the beginning of the study were used. The animals were fed with the same diet for 84 days, and blood samples were collected every 21 days for evaluation of serum metabolites and blood cell profiles. No significant correlations were found between FCR and metabolic or blood traits, although there was a significant correlation between RFI1 and urea serum concentration. There were also differences between the RFI classes for creatinine, in which more efficient animals showed higher values. The RFI2 did not correlate with any metabolic and blood cell variable, but young bulls with smaller RFI2 had a smaller number of eosinophils when compared to animals with higher RFI2. These results suggest that animals with a high RFI can have greater energy expenditure due to protein synthesis and degradation process, resulting in a larger blood urea level.

Alternative Models in Genetic Analyses of Carcass Traits Measured by Ultrasonography in Guzerá cattle: A Bayesian Approach

The objective was to study alternative models for genetic analyses of carcass traits assessed by ultrasonography in Guzerá cattle. Data from 947 measurements (655 animals) of Rib-eye area (REA), rump fat thickness (RFT) and backfat thickness (BFT) were used. Finite polygenic models (FPM), infinitesimal polygenic models (IPM) and FPM combined with IPM (IPM + FPM) were empirically tested, adjusting for the effects of permanent environment, age and weight at measurement and the contemporary group. A Bayesian analysis using the computer package FlexQTLTM was adopted. The combined model adjusted to the data, allowing reliable genetic analyses of REA and BFT. For the RFT, the IPM model was the only one to have convergence and, in this case, the trait should be analyzed by a polygenic model. The presence of up to three major genes (MGs) controlling the expression of REA and two MGs for BFT was detected. The additive genetic action was over dominance to REA, and for BFT the dominance genetic action was greater. Heritability estimates, and respective standard error, adjusted for the combined model to REA were 0.15 (0.00025) for the polygenic fraction and 0.10 (0.00019) for the oligogenic fraction; for BFT was 0.19 (0.00027) and 0.13 (0.00025), respectively. Heritability of 0.17 (0.00028) was estimated for RFT when the model was adjusted to IPM. There are major genes segregating within the population studied for REA and BFT traits, thus, their genetic analyses must be studied considering oligogenic effects. The major gene effects detected for a small number of genes, may possibly help to increase the reliability in detecting chromosomal regions that explain and control the phenotypic expression of these traits, facilitating research on detection and validation of molecular markers in this population.

Development of a direct (non-extracted) enzyme immunoassay for measurement of serum progesterone in mares

s / Journal of Equine Veterinary Science 33 (2013) 321-399 371 reproductive cyclicity in obese broodmares maintained on pasture. Eighteen healthy, light horse mares were matched by age and assigned to obese control (OBC; n1⁄45, mean BCS1⁄47.4 0.3), obese supplemented with 5g/d resveratrol (OBR; n1⁄47, mean BCS1⁄47.4 0.2) or non-obese control (NOC; n1⁄46, mean BCS1⁄45.4 0.1) treatments. Control horses received the resveratrol carrier placebo andNOChorseswere managed to maintain constant BCS throughout the trial. Across three consecutive estrous cycles, morphometric measurements were collected biweekly and follicular dynamics were evaluated via transrectal ultrasonography every other day to determine estrous cycle and follicular phase length, follicle size and number, and time of ovulation. Frequently-sampled intravenous glucose tolerance tests were conducted during luteal phase prior to supplementation and after third ovulation. Insulin and glucose kinetics were analyzed via minimal model. For all parameters, repeated measures (parametric or nonparametric, as warranted) techniques were used to determine treatment effect. Resveratrol supplementation had no discernible effect on reproductive parameters (P>0.05). Regardless of treatment (OBC or OBR), obese mares had more (7 vs. 0) hemorrhagic anovulatory follicles and tended (P1⁄40.07) to have longer inter-ovulatory intervals than NOC. Neither resveratrol treatment nor time on study influenced BCS, or bodyweight, rump fat thickness or neck circumference (raw data or data adjusted for animal size). Insulin sensitivity and disposition index were neither affected by resveratrol supplementation nor initial BCS, although as a whole, horses became more insulin resistant over time (P<0.05). NOC horses had lower (P<0.06) acute insulin response to glucose relative to OBC or OBR, but no difference (P1⁄40.19)was detected between obese groups. Although resveratrol supplementation did not elicit detectable responses in this study, promising results in other species warrant further investigation of the compound in horses, including exploration of bioavailability and possible effects at the tissue or cellular levels. Development of a direct (non-extracted) enzyme immunoassay for measurement of serum progesterone in mares R.M. Brooks , D.J. Denniston , J.E. Bruemmer , T.M. Nett , and P.M. McCue 3 Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, Department of Clinical Sciences, Colorado State University, Fort Collins, CO 80523 Progesterone (P4) isa steroidhormoneproducedby theovary and placenta of the mare. Progesterone is required for the maintenance of pregnancyand anassessmentof endogenous concentration is useful in many diagnostic applications related to equine breeding management. The overall objectiveof thisstudywastodevelopandvalidateadirectenzymelinked immunosorbent assay (ELISA) for themeasurement of P4 in themare. The specific aimwas to develop a quantitative and sensitive progesterone assay that could be used on nonextracted equine serum or plasma. Significant events in the successful development of the ELISA included the use of purified anti-progesterone antibody, heterologous combination of antibody and conjugate, and methodology to avoid organic solvent extraction. It was determined that by lowering the volume of serumused for analysis and lowering the pH of the serum, a non-extracted assay could be accomplished. The overall correlation between ELISA of nonextracted serum and radioimmunoassay (RIA) of extracted serumwas high (r1⁄4 0.92) as seen in Figure 1.

Studies on the Failure Rate of Artificial Insemination in Korean Native Cows

This study was carried out to investigate the influence of artificial insemination (AI) failure in 1,619 Korean native cows at Gangwon East area, Korea. The average AI failure rate was 37.02% in the cows and the highest rate was 40.85% in Yangyang-city. Based on the parity in the cows, the AI failure rate was 49.14% and 29.91% in the first and fifth parity cows, respectively. Whereas cows until fifth parity were decreased in AI failure, cows with sixth or more parity showed an upturning AI failure trends with the increasing of parity number. AI failure rate incidence according to the rump fat thickness measured by ultrasound was 28.9% and 33.4% at 5 mm to 10 mm and over than 15 mm, respectively. There was a positive correlation (0.2186) between AI failure rate of mother and that of their offspring cows. That is, offspring of dams with high AI failure rate showed also higher AI failure than those of dams having lower AI failure rate. In conclusion, these results indicate that the AI failure rate was closely related to the rump fat thickness, parity number, and conception rate of mother cows. In addition, these results might strengthen the basis to improve the reproductive performance in Korean native cows.

The development and evaluation of a mathematical nutrition model to predict digestible energy intake of broodmares based on body condition changes

Mathematical nutrition models have been developed for beef and dairy cattle to estimate dietary energy intake needed to change BCS. Similar technology has not been used to improve nutrition and feeding strategies for horses. An accurate equine nutrition model may enhance feeding management and reduce the costs of unnecessary overfeeding and promote an optimal level of fatness to achieve reproductive efficiency. The objectives of this study were to develop and evaluate a mathematical nutrition model capable of accurately predicting dietary energy changes to alter BW, rump fat (RF) thickness, and overall body fat (BF), which is needed to maximize profitability and productivity of mares. Model structure was similar to a previously developed model for cattle, and literature data for Quarter Horse mares were used to parameterize the horse model in predicting DE requirement associated with BCS changes. Evaluation of the horse model was performed using an independent dataset comprising 20 nonlactating Quarter Horse mares. Pretrial BCS was used to assign mares to 1 of 4 treatment groups and fed to alter BCS by 1 unit as follows: from 4 to 5 (Group 1), 5 to 4 (Group 2), 6 to 7 (Group 3), and 7 to 6 (Group 4). The BCS, RF thickness, and BW were measured for each mare before the commencement of the feeding trial and once per week thereafter for the duration of a 30-d feeding trial. Initial and target BCS, percent BF, and BW data were collected from each mare and inputted into the model. Mares were individually fed according to the DE suggestions proposed by the model to achieve the targeted BCS change within 30 d. The coefficient of determination of observed and model-predicted values (model precision) was 0.907 (P < 0.001) for BCS, 0.607 (P < 0.001) for percent BF, and 0.94 (P < 0.001) for BW. The BCS was highly correlated to percent BF (r = 0.808; P = 0.01). We concluded the reparameterized model was reliable to predict changes in BW and BCS, but more work is needed to improve the predictions of initial and final body composition.

Intake of conserved and grazed grass and performance traits in beef suckler cows differing in phenotypic residual feed intake

The objectives of the study were to quantify the phenotypic variation in residual feed intake (RFI) and productivity of beef suckler cows offered grass silage during pregnancy and, to determine the effect of RFI classification on herbage intake during lactation. Data were collected on 39 Simmental and Simmental×Holstein-Friesian cows. During the winter indoor feeding period cows were offered grass silage ad libitum daily and their individual DMI was recorded over 73d. Cow LW, BCS, skeletal measurements, ultrasonic fat and muscle depth, visual muscularity score, rumen fermentation, total tract digestibility, blood metabolites and haematological variables, as well as feeding behaviour were measured. Phenotypic RFI was calculated for each animal as the difference between actual silage DMI and expected silage DMI. Expected silage DMI was computed for each animal by regressing average daily silage DMI on conceptus adjusted mean LW0.75 and conceptus adjusted ADG over a 73-d period. Within breed, cows were ranked by RFI into low (efficient), medium and high (inefficient) groups by dividing them into thirds. Overall mean (SD) values for grass silage DMI (kg/d), grazed grass DMI (kg/d), feed conversion ratio (FCR) kgDMI/kg of LW gain (kg/d) and RFI (kgDM/d) were 9.08 (1.15), 9.98 (1.86), 24.66 (29.61), 0.00 (1.00), respectively. The RFI groups did not differ (P>0.05) in LW or ADG at any stage of measurement. Residual feed intake was positively correlated with silage DMI (r=0.87; P<0.001) but not with grass DMI (r=−0.03; P>0.05). Cows in the low RFI group consumed 14% (P<0.05) and 22% (P<0.001) less silage than those in medium and high RFI groups, respectively. Corresponding values for grazed herbage were 3% and 2% (P>0.05). Cow RFI groups did not differ (P>0.05) in BCS, ultrasonic backfat or rump fat thickness, visual muscle scores or total tract digestibility, cow milk yield, calving difficulty score, calf birth weight and ADG of calves did not differ (P>0.05) between RFI groups. Overall, this study showed that low RFI cows were more biologically and economically efficient, as they consumed less feed during the indoor winter period and a similar amount of herbage during the grazing season compared to high RFI cows, without any compromise in growth, body composition or production traits measured.

The relationship between body composition, training and race performance in a group ofThoroughbred flat racehorses

Few noninvasive measures associated with performance assessment are available for racehorse trainers. Evaluation of body composition of superior human sprinters has revealed a lower fat mass (FM), percentage (%) fat and greater fat-free mass (FFM), but to date there have been few studies evaluating this in racehorses. To determine the effects of age, gender and training on body composition and the relationship between body composition, physiological measurements and performance in Thoroughbred racehorses. At 2, 5 and 8 months of training, rump fat thickness (RFT) was ultrasonographically measured in 1-, 2- and 3-year-old Thoroughbreds (n = 148), with FM, % fat and FFM calculated. Speed, heart rate, plasma lactate and serum creatine kinase concentrations were recorded during each fast work session. Training duration (number of training days) and intensity (number of fast work sessions) were collated for each training period. Retrospective racing performance was used to categorise horses as elite or nonelite. FFM was greater in males (P = 0.006) at all training stages. There were no interactions between training duration, intensity, gender and age (P>0.05); all effects were linear. Training duration had a negative effect on RFT (P = 0.0002), FM (P<0.0001) and % fat (P<0.0001) and a positive effect on FFM (P = 0.01). Training intensity had a negative effect on RFT (P = 0.009), FM (P<0.0001), % fat (P<0.0001) and FFM (P<0.0001). FFM was greater for elite vs. nonelite horses at all training stages (P = 0.003), for males (P = 0.05) and females (P = 0.04) and for 2- (P = 0.002) and 3-year-olds (P = 0.02). While age and training affect body composition, FFM is associated with performance. Body composition assessment may assist fitness and performance evaluation.

Use of corn gluten feed and dried distillers grains plus solubles as a replacement for soybean meal and corn for supplementation in a corn silage-based stocker system

Corn gluten feed and dried distillers grains plus solubles (DDGS) were evaluated as replacements for soybean meal and ground ear corn when supplemented with corn silage during 2 yr of a beef cattle stockering program. Experiment 1: In YR 1, 104 steers (initial BW = 305 ± 30 kg), and in YR 2, 56 steers and 38 heifers (initial BW = 301 ± 32 kg) were stratified by weight and assigned to 1 of 9 groups. Each group was randomly assigned to 1 of 3 corn silage-based (75% of DM) diets supplemented with: i) corn gluten feed (CGF), ii) DDGS, or iii) soybean meal and ground ear corn (CSBM) at 25% of DM. On d 0, 28, 56, and 84, BW and BCS were recorded. Additionally, ribeye area, 12th rib fat thickness, intramuscular fat, and rump fat thickness were assessed via ultrasound on 9 (YR1) and 4 (YR 2) steers per pen that were randomly assigned as observational units. Average daily gain was greater (P < 0.05) for steers fed DDGS and CSBM compared with CGF (1.08, 1.08, and 0.94 kg/d, respectively). Average DMI (P < 0.05) was less for DDGS compared with CSBM with CGF intermediate (18.1, 18.8, 20.2 g/kg BW, respectively), and the resulting G:F was greatest for DDGS (P = 0.01). Cost per kilogram of BW gain was least for DDGS (P > 0.05). Ultrasound data indicated no differences (P ≥ 0.13) in predicted carcass traits among treatments. Experiment 2: Diets from Exp. 1 were subjected to in vitro digestion for incubation times of 0, 2, 4, 8, 16, 24, 48, and 72 h to estimate DM degradation, gas production kinetics, and CP fractions. The potentially degradable DM fraction was greater (P = 0.01) for CSBM compared with CGF and DDG. Total gas production and rate of gas production was not different among treatments (P > 0.42). Rumen degradable protein was greatest for CSBM and least for DDG (P = 0.001). These data indicate that DDGS can be used to replace soybean meal and corn in silage-based stocker systems to decrease feed costs without compromising animal performance and CGF may decrease animal performance.

Variants of the bovine retinoic acid receptor-related orphan receptor C gene are in linkage disequilibrium with QTL for milk production traits on chromosome 3 in a beef × dairy crossbreed population

Abstract. The bovine retinoic acid receptor-related orphan receptor C gene (RORC) is located on bovine chromosome 3 in the vicinity of several QTL for milk production traits, and an association of RORC genetic variants with carcass fatness traits had been confirmed by several studies. In a F2 resource population, a chromosome-wise QTL and association study with 26 genetic markers (microsatellites and SNPs from genes involved in fat metabolism) on BTA3 was performed. In the analysis, 183 first and 152 second lactation records of 183 cows were included. The QTL study revealed five QTL affecting milk yield (MY), fat percentage (FP) and protein percentage (PP) as well as the milk fat/milk protein ratio (FPR), respectively, in the chromosomal region harbouring the RORC gene. The association study displayed a significant association between RORC c.1138+65A&gt;G and MY and also associations between RORC c.934-262T&gt;G and MY, FP and FPR, respectively. A combined QTL association study showed that these SNPs included as fixed effect in the corresponding model resulted in a prominent drop of the QTL test statistic. For the RORC c.934-262T allele, which had been confirmed to increase intramuscular fat deposition, an increasing effect on milk fat content traits was detected. The RORC c.1138+65G allele that had been shown to positively affect rump fat thickness, was associated with increased MY in our study. In conclusion, we found indications that the RORC SNPs, which previously had been highlighted due to their effects on carcass fat deposition, are also associated with milk production traits.

Associations of FASN gene polymorphisms with economical traits in Nellore cattle (Bos primigenius indicus)

The aim of this study was to identify molecular markers to be applied to marker-assisted selection. Three SNPs of the FASN gene were studied. PCR-RFLP was used for genotyping. The SNPs g.17924A>G, g.17860C>T and g.15603A>G all in the FASN gene were genotyped using the enzymes MscI, DdeI and Hae III, respectively. The animals were raised in extensive systems and belong to three lines selected for growth as part of the Selection Program of Zebu and Caracu Breeds, São Paulo, Brazil. Allele and genotype frequencies were compared between selection lines using the Genepop 3.4. Associations between polymorphisms and the traits studied were evaluated using the PROC MIXED procedure of the SAS/STAT 9.1.3. The G and C alleles were the most frequent alleles of the g.15603A>G and g.17860C>T loci, respectively. The g.17924A>G locus showed no polymorphism in the population studied. Allele and genotype frequencies differed significantly between the NeT line and the NeC and NeS lines. The g.15603A>G polymorphism tended to exert an additive effect on rump fat thickness and male yearling height. For g.17860C>T, an additive effect on male yearling height was observed. Genotype combination analysis revealed a significant effect on loin eye area. Although this study provided evidence of an association between the FASN gene and some traits, more detailed analyses are needed to obtain more efficient molecular markers.

Prediction of retail beef yield, trim fat and proportion of high-valued cuts in Nellore cattle using ultrasound live measurements

The objective of this study was to develop equations to predict retail product and fat trim (weights and percentages) for Nellore (Bos indicus) cattle. Live ultrasound measurements of the longissimus muscle area, backfat thickness at the 12th rib and rump fat depth and shrunk body weight were obtained from 218 Nellore steers to predict weights and percentages of carcass retail product, pistola retail product and fat trimmings. After slaughter, carcasses were deboned and weighed and percentages of retail cuts were obtained directly. Measurements taken directly in the carcasses explained 97% and 36% of variation in carcass retail product weight and percentage, and 94% and 36% of variation in pistola retail weight and percentage, respectively. Live measurements explained 93% of carcass retail product weight and 39% of carcass retail product percentage. Lower accuracies were observed for pistola retail product weight (R2=0.87) and percentage (R2=0.33). Accuracies for fat trimmings weight and percentage were 79% and 55%, respectively. Ultrasound rump fat thickness showed greater correlations with retail product and fat trimmings (weights and percentages) when compared with ultrasound backfat thickness. The weight and percentage of retail products and of trimmable fat can be estimated in Nellore steers from live animal measurements, with similar accuracy to equations developed based on carcass measurements obtained at slaughter.

Genetic association between body composition measured by ultrasound and visual scores in Brazilian Nelore cattle1

The objective of this study was to evaluate the genetic variability of body composition traits measured by ultrasound, growth traits, and visual scores as well as their genetic associations in Nelore cattle. A total of 9,765, 13,285, 13,061, 12,811, 3,484, 3,484, 3,483, and 3,303 records of weight at time of ultrasound measure (W550), 12th-13th rib LM area (LMA), backfat thickness (BF), rump fat thickness (RF), visual scores for body structure (BS), finishing precocity (FP), muscling (MS), and sheath and navel characteristics (SN), respectively, were used. The model included contemporary group (defined as year and season of birth, sex, and management group) as a fixed effect and age of dam at calving and age of the animal (linear and quadratic effects) as covariates. The direct additive genetic effect was included as a random effect. The analyses also included 46,157 observations of BW adjusted to 120 d. The (co)variance components were estimated by the restricted maximum likelihood method using a multitrait animal model. Heritability estimates for W550, LMA, BF, RF, BS, FP, MS, and SN were 0.37 ± 0.030, 0.33 ± 0.03, 0.24 ± 0.02, 0.28 ± 0.03, 0.24 ± 0.04, 0.38 ± 0.05, 0.29 ± 0.05, and 0.38 ± 0.06, respectively. The estimated genetic correlations between visual scores and LMA were moderate and positive, ranging from 0.37 to 0.44. Similar results were obtained for the estimated genetic correlations between FP and MS with fat thickness measures (BF and RF). Low genetic correlations were estimated between SN and BS and between SN and the body composition traits, indicating that selection for body composition traits and BS will not affect sheath and navel size. The estimated genetic correlations between weight adjusted to 120 d of age (W120) and W550 and BS were high (0.87 and 0.91) and moderate with LMA (0.49 and 0.55), FP (0.37 and 0.41), and MS (0.47 and 0.55). The visual scores and ultrasound-measured body composition traits have enough genetic variation for selection purposes in Nelore cattle. Selection based on visual scores for body structure, finishing precocity and muscling should lead to desired changes in body composition albeit much more slowly than direct selection on those traits measured by ultrasound. Selection for heavier BW at early ages should lead to favorable changes in yearling LM area and visual scores.

Dietary supplementation of conjugated linoleic acid in horses increases plasma conjugated linoleic acid and decreases plasma arachidonic acid but does not alter body fat

Studies using dietary supplementation of eicosapentaenoic and docosahexaenoic fatty acids (FA) in horses report inconsistent anti-inflammatory results but consistently report an increase in plasma arachidonic acid (C20:4), the major substrate of cyclooxygenase (COX) II inflammatory pathway. Conjugated linoleic acid has shown anti-inflammatory effects in laboratory and food animal species, but effects of CLA supplementation in horses have not been reported. Our objective was to determine the effects of CLA supplementation on plasma CLA and C20:4 and body fat in healthy horses at maintenance. In a crossover study, 12 mature mares were blocked by breed, age, and BCS and separated into 2 treatment groups (n = 6/group). Groups were fed CLA and corn oil (CO; isocaloric control) for two 6-wk feeding periods, separated by a 4-wk period during which treatment was withheld. Corn oil or CLA supplement (55% mixed CLA isomers) was incorporated into diets at 0.01% BW/d. Mares were fed individually and restricted to dry lots to control forage intake. Rump fat thickness (RFT), BW, and BCS were measured before (d 0) and after (d 42) each feeding period. Blood was collected on d 0, 14, 28, and 42 of each 6-wk period for GLC analysis of plasma CLA isomers (cis-9, trans-11; trans-10, cis-12; and trans-9, trans-11) and C20:4. An ANOVA was conducted to compare the response of RFT, BW, and BCS of CLA-treated and control mares. A mixed methods analysis with repeated measures was used to detect differences in plasma FA concentrations. There were no differences in BW, RFT, or BCS between treatment groups. All CLA isomers present in the CLA supplement were greater in plasma of horses fed CLA compared with controls (P < 0.01). Additionally, plasma concentrations of C20:4 were decreased in horses fed CLA (P < 0.05). This decline in C20:4 may impact the COX II pathway and warrants further investigation. These results suggest that in an equine model, dietary CLA increases circulating concentrations of supplemented CLA isomers and decreases circulating C20:4. Examining physiological effects of CLA supplementation in horses at varying levels of growth, exercise, and progression of joint disease may offer insight to potential benefits of CLA in the horse.

Feed efficiency and its correlations with carcass traits measured by ultrasound in Nellore bulls

Forty-six Nellore bulls were individually fed for 84days and evaluated for residual feed intake (RFI) and feed conversion ratio (FCR) with the objective to correlate RFI1 (usual), RFI2 (adjusted for final rump fat thickness) and FCR with carcass composition traits measured by ultrasound and to verify differences between RFI groups (classified by standard deviation) in performance and carcass traits. Carcass traits were evaluated by ultrasound at the beginning and at the end of the test and the gain over the test period was calculated for ribeye area (REA), backfat thickness on the 12–13th ribs (BFT) and rump fat thickness on the Biceps femoris muscle (RFT). The RFI1 was positively correlated (P<0.05) with the final RFT (r=0.34) and with the gain in RFT (r=0.36) and also there were differences (P<0.05) in these traits and also in dry matter intake (DMI) between groups, in which the most efficient animals had lower values of DMI, final RFT, and gain in RFT. For the RFI2, there were no differences (P>0.05) between groups and neither were there significant correlations between those with the carcass traits, only for FCR, feed efficiency and DMI. FCR was correlated with the gain in REA and BFT (r=−0.43 and r=−0.31, respectively) and with the initial BFT (r=0.31). The positive correlation between residual feed intake and subcutaneous fat of Nellore bulls' may cause some concern, because with the selection of more efficient individuals (with negative RFI), carcasses which are too lean will be produced. Adjustments in the estimation of RFI including carcass traits may override this undesirable effect.

Variation in the XKR4 gene was significantly associated with subcutaneous rump fat thickness in indicine and composite cattle

Variation in the XK, Kell blood group complex subunit-related family, member 4 (XKR4) gene on BTA14 was associated with rump fat thickness in a recent genome-wide association study. This region is also of interest because it is known to show evidence of a signature of population genetic selection. In this study, additional variation in this gene was genotyped in a sample of a total of 1283 animals of the Belmont Red (BEL) and Santa Gertrudis (SGT) breeds. The SNP rs41724387 was significantly (P < 0.001) associated with rump fat thickness and explained 5.9% of the genetic variance for the trait in this sample. Using the 4466 genotypes for the SNP rs42646708 from several data sets to estimate effects in seven breeds, this relatively large quantitative trait locus effect appears to be a result of the variation in indicine and taurine-indicine composite cattle. However, the only DNA variant found in Brahman cattle that altered the predicted amino acid sequence of XKR4 was not associated with rump fat thickness. This suggests that causative mutations lie outside the coding sequence of this gene.

Association of single nucleotide polymorphisms in the bovine leptin and leptin receptor genes with growth and ultrasound carcass traits in Nellore cattle

Given the important role of leptin in metabolism, we looked for a possible association of leptin and leptin receptor polymorphisms with carcass and growth traits in Nellore cattle. We examined associations of leptin and leptin receptor SNPs with ultrasound carcass (longissimus dorsi muscle area (ribeye area), backfat thickness and rump fat thickness and growth traits (weaning weight adjusted to 210 days of age, yearling weight adjusted to 550 days of age, weight gain of weaning to yearling and scrotal circumference adjusted to 550 days of age) of 2162 Bos primigenius indicus (Nellore) animals. Allele and genotypic frequencies were calculated for each marker. Allele substitution, additive and dominance effects of the polymorphisms were also evaluated. Some alleles of the molecular markers had low frequencies, lower than 1%, in the sample analyzed, although the same polymorphisms described for B. p. taurus cattle were found. Due to very low allelic frequencies, the E2JW, A59V and UASMS2 markers were not included in the analysis, because they were almost fixed. E2FB was found to be significantly associated with weight gain, ribeye area and backfat thickness. The promoter region markers, C963T and UASMS1, were also found to be significantly associated with ribeye area. T945M was significantly associated with weight gain. We conclude that the leptin and receptor gene markers would be useful for marker-assisted selection.