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Measures of heifer fertility are economically relevant traits for beef production systems and knowledge of candidate genes could be incorporated into future genomic selection strategies. Ten traits related to growth and fertility were measured in 890 Brangus heifers (3/8 Brahman × 5/8 Angus, from 67 sires). These traits were: BW and hip height adjusted to 205 and 365 d of age, postweaning ADG, yearling assessment of carcass traits (i.e., back fat thickness, intramuscular fat, and LM area), as well as heifer pregnancy and first service conception (FSC). These fertility traits were collected from controlled breeding seasons initiated with estrous synchronization and AI targeting heifers to calve by 24 mo of age. The BovineSNP50 BeadChip was used to ascertain 53,692 SNP genotypes for ∼802 heifers. Associations of genotypes and phenotypes were performed and SNP effects were estimated for each trait. Minimally associated SNP (P < 0.05) and their effects across the 10 traits formed the basis for an association weight matrix and its derived gene network related to FSC (57.3% success and heritability = 0.06 ± 0.05). These analyses yielded 1,555 important SNP, which inferred genes linked by 113,873 correlations within a network. Specifically, 1,386 SNP were nodes and the 5,132 strongest correlations (|r| ≥ 0.90) were edges. The network was filtered with genes queried from a transcriptome resource created from deep sequencing of RNA (i.e., RNA-Seq) from the hypothalamus of a prepubertal and a postpubertal Brangus heifer. The remaining hypothalamic-influenced network contained 978 genes connected by 2,560 edges or predicted gene interactions. This hypothalamic gene network was enriched with genes involved in axon guidance, which is a pathway known to influence pulsatile release of LHRH. There were 5 transcription factors with 21 or more connections: ZMAT3, STAT6, RFX4, PLAGL1, and NR6A1 for FSC. The SNP that identified these genes were intragenic and were on chromosomes 1, 5, 9, and 11. Chromosome 5 harbored both STAT6 and RFX4. The large number of interactions and genes observed with network analyses of multiple sources of genomic data (i.e., GWAS and RNA-Seq) support the concept of FSC being a polygenic trait.

ETH10 is a dinucleotide microsatellite within the promoter of signal transducer and activator of transcription 6 (STAT6) gene on bovine chromosome 5. ETH10 is included in the panel of genetic markers used in parentage testing procedures of cattle breed associations. Allelic sizes of ETH10 PCR amplicons range from 199 to 225 bp. Objectives of this study were to use microsatellite data from beef cattle breed associations to investigate genetic distance and population stratification among Angus- and Brahman-influenced cattle and to use ETH10 genotypes and growth and ultrasound carcass data to investigate their statistical relationships. Three series of genotype to phenotype association analyses were conducted with 1) Angus data (n = 5,094), 2) Brangus data (3/8 Brahman × 5/8 Angus; n = 2,296), and 3) multibreed data (n = 4,426) of Angus and Brangus cattle. Thirteen alleles and 38 genotypes were observed, but frequencies varied among breed groups. Tests of genetic identity and distance among 6 breed composition groups increasing in Brahman influence from 0 to 75% revealed that as Brahman-influence increased to ≥50%, genetic distance from Angus ranged from 18.3 to 43.5%. This was accomplished with 10 microsatellite loci. A mixed effects model involving genotype as a fixed effect and sire as a random source of variation suggested that Angus cattle with the 217/219 genotype tended to have 2.1% heavier (P= 0.07) 205-d BW than other genotypes. In Brangus cattle, allele combinations were classified as small (≤215 bp) or large (≥217 bp). Brangus cattle with the small/large genotype had 2.0% heavier (P< 0.05) birth weight, yet cattle with the large/large genotype had approximately 5.1% greater (P< 0.05) percentage of fat within LM and more LM per BW than cattle with small/large or small/small genotypes. Genotype-to-phenotype relationships were not detected in multibreed analyses. The ETH10 locus appears to be associated with growth and carcass traits in Angus and Brangus cattle. Results from this study provide support for STAT6as one of the candidate genes underlying cattle growth QTL on chromosome 5.

The growth endocrine axis influences reproduction. The objectives of this study were to evaluate population genetic characteristics of SNP genotypes within genes of the GH-IGF axis in straightbred and crossbred Angus, Brahman, and Romosinuano heifers (n = 650) and to test the association of these genotypes with measures of reproduction. These objectives were achieved using 73 SNP within 7 genes on chromosome 5 and the pregnancy-associated plasma protein A2 (PAPP-A2) and GH-receptor genes, which map to chromosomes 16 and 20, respectively. The SNP were elucidated by resequencing conserved regions of each gene by using DNA from familial-unrelated cattle of a multibreed discovery population. A multiplex SNP assay yielded 59 biallelic SNP useful for evaluating genetic identity and distance. Specifically, the divergence of straightbred Brahman cattle was approximately 15.5% from 5 Bos taurus-influenced breed groups. In the straightbred groups used as a validation population, only 3 SNP had minor allele frequencies >10%. These SNP were in the genes PAPP-A2(ss115492449-A/C and ss115492450-G/T within intron 10) and signal transducers and activators of transcription 2 (STAT2; ss252841035-A/G within the 5′ untranslated region), and they met the conditions of Hardy-Weinberg equilibrium (P> 0.31). The other 56 SNP were useful for assigning each animal into ancestral clusters (n = 3 proportions) to account for population stratification in genotype to phenotype association analyses. The 2 SNP in the PAPP-A2gene influenced (P< 0.05) traits indicative of first-calf heifer rebreeding (i.e., calving interval, days to calving, and pregnancy rate). A STAT2SNP genotype (i.e., GG) × primary ancestral cluster interaction (P< 0.05) suggested heifers primarily of B. taurusancestry had a reduction of approximately 16.4 ± 0.1% in calving interval and days to calving relative to heifers clustering primarily as Bos indicusancestry. Even though additional research is needed to delineate the allelic variation attributed to genes of the GH-IGF axis, results of this study provide support for STAT2and PAPP-A2as potential candidate genes associated with first-calf heifer rebreeding traits.

Balancing growth and reproductive performance in beef cattle managed in desert environments is challenging. Our objectives were to 1) evaluate trends in growth and reproductive traits, and 2) assess associative relationships between growth characteristics and reproductive performance in a Brangus herd managed in a Chihuahuan Desert production system from 1972 to 2006. Data were from bull (n = 597) and heifer calves (n = 585; 1988 to 2006) and cows (n = 525; repeated records of cows, n = 2,611; 1972 to 2006). Variables describing the growth curve of each cow were estimated using a nonlinear logistic function (each cow needed 6 yr of data). Mixed-effect models and logistic regression were used to analyze trends across years in growth and reproductive traits (both continuous and categorical). For continuous traits of calves, a slight cubic response (P< 0.01) described the dynamics of birth weight, 205-d BW, and 365-d BW across years. For categorical traits of females, positive linear trends (P< 0.05) across years were observed in percent pregnant as yearlings, calved at 2 yr of age, and first-calf heifer rebreeding (slopes ranged from 0.007 to 0.014%/yr). Autumn cow BW increased gradually until 1997 (509 kg ± 8.8) and then decreased gradually by 0.6 kg/yr, whereas pregnancy percentage decreased gradually until 1995 (78.4% ± 1.0) and then increased slightly by 0.2%/yr. A quadratic effect best described the dynamics of these 2 variables across years (P< 0.01) as well as estimates describing the growth curve of each cow. Specifically, asymptotic BW and age increased (P< 0.05) from 1972 to 1983 and 1990, respectively. Asymptotic age then decreased by 27% from 1983 to 1996 (P< 0.05). The maturing rate index was negatively correlated with age at first calving and calving interval (r = –0.42 and –0.18, P< 0.01), which suggested that early-maturing cows had enhanced fertility in this environment and production system. In summary, minimal changes were observed in measures of growth in bulls and heifers in a Brangus herd managed in the Chihuahuan Desert. Opposing relationships were observed among measures of cow size and fertility; as growth curves shifted toward earlier maturity, measures of reproductive performance suggested that fertility improved.

Feed costs and market volatility make identifying cattle biological types and performance traits with significant economic impact at the feedlot imperative. Thus, the objective of this study was to determine the economic values of feedlot performance traits in commercial Angus (n= 20), half-blood Lowline-influenced Angus (n= 20), and full-blood Lowline Angus (n= 8) steers. Steers were fed for 72-d after a 28-d adjustment period at the CSU, Chico Agricultural Teaching and Research Center's beef cattle feeding facility. Upon delivery, steers were randomly assigned to three, 7 × 18 m pens, each fitted with two GrowSafe feed nodes and allowed ad libitum access to water and finishing ration (CP = 11.9%, TDN = 72.58%, NDF = 20.20%). After the 72-d GrowSafe trial, steers continued in their assigned GrowSafe pens until slaughter. Feedlot performance traits with significant economic impact were identified using stepwise, multiple-trait linear regression of net revenue onto residual feed intake (RFI), ADG, DMI, slaughter weight, and dummy variables representing breed type. Net revenue was defined as gross revenue minus feed costs. Gross revenue for each steer was determined by multiplying each animal's slaughter weight by market price at the time of sale ($3.26/kg). Costs included yardage ($.50/hd/d), billed daily feed consumption, and average feeder price ($3.68/kg) multiplied by delivery weight. Average net revenue (±SD, USD) for the commercial Angus, half-blood Lowline-influenced and full-blood Lowline Angus steers were $10.13 ± 86.97, $–44.30 ± 69.98, and $–105.05 ± 86.97, respectively. Multiple linear regression results identified slaughter weight, DMI, and ADG as significant predictors of feedlot net revenue (R2= 0.41; P< 0.05). Coefficients representing economic values for slaughter weight, DMI and ADG were $0.66, $–32.92, and $71.30, respectively. Results suggest that slaughter weight, DMI, and ADG are key predictors of feedlot net revenue, and deserve consideration in the development of breeding objectives with the goal of improving feedlot profitability.

Objectivesof this study were to determine the effects of supplemental brewers grain on growth performance and reproductive characteristics of Angus and Red Angus heifers in a 3-yr study. A total of 85 spring-born, weaned heifers were randomized via gate cut and placed on an 84 d supplementation trial. Treatment groups were either control (CON; n= 43; initial BW = 311.90 ± 8.57 kg) or wet brewers grain (WBG; n= 42; initial BW = 309.43 ± 8.57 kg) groups. Heifers were housed on adjacent improved pastures (TDN, 56.5%; CP, 11.19%; NDF, 64.8%) and supplemented once daily at 1800 with either the control (CON, alfalfa hay + corn silage; TDN, 52.4%, CP, 8.2%, NDF, 65.6%) or WBG (Alfalfa hay + corn silage + wet brewers grain; TDN, 53.6%, CP: 9.8%, NDF, 66.2%) ration. Diets were balanced to target 0.68 kg ADG/head and were offered on an ad libitum basis. Fifteen days after supplementation period, heifers were synchronized using the 14 d controlled internal drug release-PG + heat detection + timed AI protocol. Traits collected were: BW at d 0, 28, 56, and 84; total gain; ADG; response to synchronization protocols; and ultrasound pregnancy rate. During yr 2, weekly blood serum samples were collected via jugular venipuncture for determination of serum progesterone concentration. Age at puberty was defined as heifer age in days on date of second consecutive progesterone values > 1 ng/mL. Growth performance measures were analyzed as a completely randomized block design (block = year of study) and age at puberty was analyzed as a completely randomized design. No difference (P> 0.05) was detected between the control and treatment groups for heifer BW on d 28 (325.97 ± 8.88 vs. 324.86 ± 8.88 kg), d 56 (341.54 ± 8.57 vs. 341.84 ± 8.57 kg), d 84 (361.42 ± 8.21 vs. 360.38 ± 8.21 kg), and ADG (0.14 ± 0.01 vs. 0.14 ± 0.01 kg). Age of puberty did not differ (P> 0.05) between treatment groups. Results indicate that heifers supplemented with brewer's grain showed no deviation in development compared with heifers fed the control ration. Cumulative results suggest that WBG could be used as part of a heifer development ration to help offset costs associated with diet ingredients; however, economic analyses of ration and development costs need to be investigated further.

Objectives of this study were to determine the effects of wet brewers grain (WBG) as a winter supplement on cow and calf performance while grazing native annual grasslands. The study was conducted at the Sierra Foothill Research and Extension Center (Browns Valley, CA) during 2014–2015 and 2015–2016 winter grazing seasons (i.e., November through January). A total of 92, fall-calving Angus × Hereford cows grazing native annual pastures (12.12 ha/pair for 84 d; 3.56% CP, 39.3% TDN, 75.3% NDF) were supplemented with either molasses low moisture protein block, available ad libitum (CON; n= 28; CP, 26%) or WBG (fed 3 times/wk; formulated to offer 0.68 kg CP head/d on DM basis; CP, 26%). Treatment groups were housed in adjacent pastures during the 84 d supplementation period and weights were taken in 28 d intervals. Dependent variables included: cow and calf BW and cow BCS. Data were analyzed as a randomized block design where block = year of study. Treatment × block interaction was not significant (P> 0.05). Calves were born before beginning of study each year and calf date of birth was fit as a covariate. Brewers grain supplemented cows were heavier on d 56 compared with CON cows (560.63 vs. 529.86 ± 13.99 kg; P= 0.03). Similarly, WBG calves were also heavier on d 56 compared with CON calves (117.97 vs. 110.06 ± 3.72 kg; P= 0.03). Calves born to WBG supplemented cows tended (P< 0.10) to be heavier than those of CON supplemented cows on d 0 (57.96 vs. 58.81 ± 2.73 kg) and d 86 (141.64 vs. 152.03 ± 3.74 kg). Results indicate that cows and calves supplemented with WBG recovered weight more quickly than those consuming liquid protein supplement. Therefore, WBG may have considerable potential as a winter protein supplement on California grasslands; however, economic analyses need further investigation.

Objectives of this study were to measure growth performance and feed efficiency of commercial (n= 20) and half-blood Lowline-Angus (n= 20) steers during the backgrounding and finishing growth phases. A total of 40, spring-born steers were delivered to the CSU, Chico cattle feeding facility 30 d postweaning and randomly assigned to three 7 × 18 m pens equipped with GrowSafe feed intake system for a 28 d adaption period. Commercial (n= 20) and half-blood Lowline-Angus (n= 20) steers were fed a forage-based backgrounding ration (CP, 15.6%; TDN, 56.22%; NDF, 52%, DM basis) for 58 d and allowed ad libitum access to feed and water. Cattle were transitioned to the finishing ration (CP, 11.9%; TDN, 72.58%; NDF, 20.21%, DM basis) over a 16 d period. Finishing phase trial was 72 d and weights were taken on d 0, 1, 35, 71, and 72. Data were analyzed as a randomized block design (block = pen). Breed × pen effect was not significant (P> 0.05). In the backgrounding phase, dry matter intake tended (P= 0.06) to be greater for commercial steers (DMI; 9.16 ± 0.36 kg) compared with half-blood Lowline-Angus (DMI; 8.17 ± 0.36 kg) steers. ADG, metabolic mid-weight, residual feed intake and feed conversion ratio were not different (P> 0.05) between breed groups in the backgrounding phase. In the finishing phase, commercial and half-blood Lowline-Angus steers had different (P< 0.05) ADG (1.82 ± 0.05 kg vs. 1.53 ± 0.05 kg), metabolic mid-weight (MMWT; 72.30 ± 1.18 kg vs. 68.16 ± 1.18 kg), DMI (10.12 ± 0.20 kg vs. 8.65 ± 0.20 kg), residual feed intake (RFI; 0.24 ± 0.13 kg vs. –0.22 ± 0.13 kg) and end weight (464.41 ± 9.28 kg vs. 423.16 ± 9.25 kg). Results indicate that backgrounding phase performance may not be an accurate predictor for finishing phase performance. Lack of significance in the backgrounding phase between breed groups may be a function of half-blood steers being F1 generation. Further research should be conducted to assess feed efficiency performance during the backgrounding phase in commercial and half-blood Lowline-Angus steers.