Browsing by Subject "beef cattle"
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Item Characterization of residual feed intake and relationships with performance, carcass and temperament traits in growing calves(Texas A&M University, 2004-11-15) Fox, James TrentThe objectives of this study were accomplished with two experiments in growing Bonsmara bulls (N = 68) (experiment 1), and Simmental crossbred calves (N = 132) (experiment 2). Specific objectives for experiment 1 were to characterize residual feed intake (RFI) in growing bulls, and examine relationships between RFI and performance, fertility, temperament and body composition traits. In experiment 2, the objectives were to examine stocker-phase supplementation effects on feedlot feed conversion ratio (FCR) and RFI and to characterize relationships between these feed efficiency traits, and performance and carcass traits in finishing calves. In both experiments, individual feed intakes and BW were measured. Ultrasound technology was used to measure body composition in experiment 1, while actual carcass measurements taken at harvest were used for experiment 2. Experiment 1 demonstrated that temperament affected ADG and DMI, but not FCR or RFI. Residual feed intake was not phenotypically correlated to scrotal circumference or bull fertility traits. Experiments 1 and 2 demonstrated that RFI was independent of ADG and BW, but that there was a tendency (P < 0.10) for RFI to be phenotypically correlated with 12th rib fat thickness (r = 0.20 and 0.22). However, RFI was not correlated with longissimus muscle area in either experiment. Both experiments demonstrated that low RFI (< 0.5 SD below mean RFI) calves consumed significantly (20 and 22%) less feed and had improved (21%) FCR compared to calves with high RFI (> 0.5 SD above mean RFI). Results from experiment 2 suggest that RFI measured while calves are consuming high-grain diets may be less influenced by previous level of stocker supplementation compared to FCR or residual gain efficiency traits. In summary, RFI was found to be phenotypically independent of growth rate and BW, had no effect on bull fertility or temperament traits, and was less impacted by previous plane of nutrition compared to FCR.Item Factors Influencing the Adoption of Water Quality Best Management Practices by Texas Beef Cattle Producers(2014-05-28) Peterson, JenniferThe management of agricultural nonpoint source pollution is complex due to the diffuse nature of the various sources. As a result, rather than relying on direct regulation, natural resource agencies generally utilize a watershed approach to encourage the voluntary adoption of best management practices (BMPs) to improve water quality and control nonpoint source pollution originating from livestock, farm, and forestry operations as well as urban nonpoint sources. Policy tools used to encourage voluntary adoption include educational programming as well as technical and financial assistance opportunities. Despite the known water quality benefits of BMPs and the availability of policy tools to encourage adoption, some landowners and livestock producers choose not to adopt conservation practices. This study examined the current adoption behavior of Texas beef cattle producers and investigated how factors related to capacity, attitudes, environmental awareness, and farm characteristics influenced the adoption of BMPs known to reduce levels of bacteria, sediment, nutrients, and other contaminants in runoff. A statewide mail survey of beef cattle producers was conducted in the Fall of 2013. Univariate probit analysis was used to estimate the influence of 30 predictor variables on the probability of a beef cattle producer adopting 18 different water quality BMPs. Results from the analysis show producers are adopting and maintaining water quality BMPs despite a significant lack of knowledge concerning common water quality terms and the availability of financial assistance programs to aid in practice implementation. The most significant predictors of adoption among survey respondents included visits with Extension, prior participation in a government cost-share program, crop diversity, annual income, and percent income from the operation. The most significant factors reducing the probability of adoption among survey respondents included education, gender, visits with NRCS, membership in a livestock organization, and having a family member take over the operation. These results suggest the need to address information gaps among beef cattle producers as well as demonstrate a significant opportunity for the NRCS and Extension to forge a strategic long-term partnership to promote increased and sustained adoption of water quality BMPs.Item Fixed-time insemination of porcine luteinizing hormone-treated superovulated beef cows and the resynchronization of beef cows for fixed-time embryo transfer(2009-05-15) Nelson, John StephenTwo trials were conducted to compare the effectiveness of fixed-time artificial insemination (AI) to AI based upon visual detection of estrus following superstimulation of donor beef cows. In Trial 1, multiparous beef cows (n = 31) were randomly allotted to one of three treatments following superstimulation and removal of an intravaginal progesterone insert (CIDR). Cows in the Control group were inseminated at 12 and 24 h after onset of estrus. Cows in the Estradiol group were injected with estradiol-17? (1 mg, im) at 12 h and inseminated at 24 and 36 h after CIDR removal. Cows in the pLH36 group were injected with porcine LH (Lutropin, 12.5 mg, im) at 24 h and inseminated at 36 and 48 h after CIDR removal. Mean numbers of viable embryos were 7.8, 3.6 and 9.6 for Control, Estradiol and pLH36 treatment groups, respectively (P > 0.10). In Trial 2, multiparous beef cows (n = 22) were randomly allotted to one of three treatments following superstimulation and removal of a CIDR. Sixteen of the cows were superstimulated a second time approximately 50 days later and allotted to one of the two treatments that differed from the initial treatment group. Cows in the Control group were inseminated at 12 and 24 h after onset of estrus. Cows in the two pLH groups were injected with porcine LH (Lutropin,12.5 mg, im) at 24 h after CIDR removal and were inseminated with either one unit of semen at 36 and 48 h (pLH36) or with two units of semen at 48 h (pLH48) after CIDR removal. Mean numbers of viable embryos were 3.0, 6.4 and 3.8 for Control, pLH36 and pLH48 treatment groups, respectively (P > 0.10). These data indicate that administration of pLH can facilitate use of fixed-time AI in superovulated beef cows without sacrificing embryo production. The second study evaluated the efficacy of resynchronizing beef cow recipients using CIDR devices for only 7 or 14 d. Recipient cows received CIDRs either on the day of transfer (n = 88) or 7 d post-transfer (n = 230). All CIDRs were removed on d 21 and cows were observed for estrus between d 22 and 24. Cows that displayed estrus were ultrasounded on d 30, those cows not pregnant that possessed a CL had an embryo transferred that day. Cows were later examined for pregnancies approximately 23 to 30 d later. There were no differences in pregnancy rates between cows with 7 or 14 d CIDRs and therefore data were combined. Pregnancy rates at two different ranches indicate that beef cow recipients can be successfully resynchronized by insertion of a CIDR without compromising pregnancy rates of transferred embryos. At Center Ranch the pregnancy rate for the first transfer was 57% while the resynchronized group that received the second transfer had a pregnancy rate of 55%. At Mound Creek Ranch the first transfer of embryos produced 59% pregnancy rates while the second transfer had a pregnancy rate of 71%. No significant differences (P > 0.05) were observed between the pregnancy rates of the initial transfer and those of the resynchronized transfer using only CIDRs, indicating that resynchronization using CIDRs can be used without reducing pregnancy rates.Item Genetic epidemiology and familial risk factors for paratuberculosis seropositivity in beef cattle(2009-05-15) Osterstock, Jason BarrettParatuberculosis is an intestinal infection of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Genetic associations with paratuberculosis have been described in Holstein cattle. The objectives were to describe the association between paratuberculosis status of the dam and her offspring in beef cattle, develop methods to assess familial aggregation of paratuberculosis in cattle of unknown pedigree, and model the paratuberculosis status of beef cattle given familial and herdlevel covariates. Texas beef cattle were tested for paratuberculosis using serum antibody and microbiologic culture of feces. Available pedigree data were used to confirm familial relationships. The association between the paratuberculosis ELISA status of the dam and her offspring was assessed using mixed-effects models. Increased odds of being classified as a ?suspect? or greater based on ELISA results were observed if the dam was classified as a ?suspect? or greater. A positive linear association was observed between the ELISA value of the dam and her offspring. Analysis of pedigree data using conditional logistic regression identified ancestors associated with significantly increased odds of being classified as ?low positive? or greater. Microsatellite markers were used to classify cattle into genetically similar groups using allele frequency data. Nine clusters of genetically similar cattle were identified among paratuberculosis test positive cattle, herd matched controls, and pedigreed cattle. Clusters were validated using animals of known pedigree. Increased odds of paratuberculosis seropositivity were observed for some clusters compared to the cluster with the lowest seroprevalence. A predictive model was developed using a Bayesian framework to assess the association between antibody status of the dam and her offspring adjusted for herd-level risk factors. Predictors associated with highly probable increased odds of seropositivity included herd seroprevalence and herd fecal prevalence of MAP. The association between dam and offspring ELISA status was small (OR 1.35) and not highly probable. The results of this work support familial aggregation of paratuberculosis ELISA status, but herd-level risk factors appear to be more important in predicting ELISA status. A large proportion of observed serological reactions were not supported by fecal culture results; therefore, observed associations might be limited to humoral responses to Mycobacterium spp.Item Post-Extraction Algal Residue as a Protein Source for Cattle Consuming Forage(2012-11-13) Drewery, Merritt Leanne 1989-Four studies were conducted to evaluate the potential for post-extraction algal residue (PEAR) to be incorporated as a protein source in the grazing sector of the beef cattle industry. In Experiment 1, blends of PEAR and conventional protein supplements (dried distillers? grains, DDG; cottonseed meal, CSM) were offered to steers consuming Bermudagrass to evaluate palatability of PEAR. Supplement completion, time required for consumption, and amount of supplement consumed were recorded. In Experiment 2, isonitrogenous amounts of PEAR and CSM (100 mg N/kg BW) were supplemented to steers consuming low-quality forage to compare effects on nutrient utilization. Experiment 3 evaluated the optimal inclusion rate of PEAR to steers consuming low-quality forage. Treatments included no supplemental protein, 3 levels of PEAR (50, 100, and 150 mg N/kg BW) and 1 level of CSM (100 mg N/kg BW). In Experiment 4, the effects of upstream operations on the nutritive value of PEAR were quantified. Observations indicate PEAR may be blended with existing protein sources in the beef industry without negatively affecting palatability, but there may be palatability concerns when PEAR is offered alone. Provision of 100 mg N/kg BW of PEAR or CSM stimulated forage intake (P ? 0.05) and increased N retention (P = 0.02) relative to unsupplemented animals. Imbalances in mineral intakes (Ca:P ratio of 8:1) were observed when PEAR was supplemented, but not CSM. Total digestible OM intake (TDOMI) responded quadratically (P = 0.01) to increasing provision of PEAR with maximization occurring when PEAR was provided at 100 mg N/kg BW. There was not a difference in TDOMI (P = 0.13) at isonitrogenous levels of PEAR and CSM, indicating forage utilization was stimulated to a similar extent. Excess mineral levels and imbalances in PEAR were largely a result of cultivation, harvesting, and extraction procedures which could be controlled. Thus, there is potential to alter production streams to optimize oil yield and co-product value. Overall, our results indicate PEAR can be incorporated as a protein source in the beef cattle industry, thus increasing economic viability of biofuel production from algal biomass.Item Predicting Forage Nutritive Value Using an In Vitro Gas Production Technique and Dry Matter Intake of Grazing Animals Using n-Alkanes(2011-08-08) Aguiar, Andre D.In the first experiment, forage samples (n = 39) were collected during 4 years (2006 ? 2009) from pastures grazed by Santa Gertrudis cattle at the King Ranch, TX. The in vitro gas production technique (IVGP) was performed to understand the pattern of fermentation parameters of the forage and obtain fractional digestion rate (kd) values to predict total digestible nutrients (TDN). The best nonlinear model to describe the IVGP values of the forages was the two-pool logistic equation. The passage rate (kp) of 4%/h was used.. The kp predicted by the Large Nutrient Ruminant System (LNRS) model was 3.66%/h. The average TDN was 55.9% compared to 53.8% using a theoretical equation. In the second experiment, Brahman bulls (n = 16) grazed Coastal bermudagrass pastures [Cynodon dactylon (L.) Pers.] and stocked at a moderate to low grazing pressure. Three periods of fecal collections were made within each period. Bulls were individually fed at 0700 and 1900 h of 400 g of corn gluten pellets containing C32 n-alkanes. Each period was divided in 2 sub periods in which fecal samples were collected 4 times a day (0700, 1100, 1500 and 1900 h). N-alkanes in the forage and feces were determined using gas chromatography. In the third experiment, four methods were used to estimate dry matter intake (DMI): C31 or C33 with or without adjustment for forage C32 (C31_0 and C33_0, respectively). There was a difference between morning (0700 and 1100 h) and afternoon fecal collections (1500 and 1900 h) on the predicted DMI using C31 (P = 0.0010), C33 (P = 0.0001), C31_0 (P = 0.0010), or C33_0 (P < 0.0001). There was no difference in average daily gain (ADG) between low and high residual feed intake (RFI) (P = 0.5709). The nonparametric analysis indicated that preranking animals for efficiency under confinement conditions does not guarantee (P < 0.0001) similar ranking under grazing conditions when using the alkane technique to determine forage DMI. In order to estimate DMI at least 5 d of fecal collection and 2 times a day of collection (0700 and 1500h) are needed to decrease the variability.Item Synchronization of follicular wave emergence, luteal regression, and ovulation for fixed-time artificial insemination in beef cows and heifers(Texas A&M University, 2006-10-30) Stutts, Kyle JeffreyTwo experiments tested the efficacy of gonadotropin-releasing hormone (GnRH) or estradiol cypionate (ECP) administration in combination with controlled internal drug release (CIDR) inserts on pregnancy rate to fixed-time artificial insemination (FTAI) in beef heifers. In the first experiment, heifers in the two ECP groups received ECP in conjunction with the CIDR insert. The CIDR insert was removed and PGF was administered on either d 7 or 9. Heifers received ECP 24 h after CIDR removal and were inseminated 30 h after ECP. Heifers in the two GnRH groups received GnRH in conjunction with the CIDR insert. Heifers received PGF on either d 6 or 7, and the CIDR insert was removed on d 7. Heifers were inseminated and received GnRH 48 h after CIDR removal. Pregnancy rates to FTAI were higher for heifers treated with GnRH. Pregnancy rate to FTAI was highest for heifers in the GnRH group that received PGF on d 6 and was lowest for the group that received ECP in combination with a 7-d CIDR insert. In the second experiment, heifers received GnRH in conjunction with the CIDR insert. CIDR inserts were removed and PGF was administered on d 7. Heifers were inseminated 60 h later, with one group receiving GnRH at insemination. Pregnancy rate to FTAI was higher for heifers that received GnRH at insemination. The final experiment tested the efficacy of estradiol 17_ (E17) or GnRH in combination with a CIDR insert on pregnancy rate to FTAI in Brahman cows. Either E17 or GnRH was administered in conjunction with the CIDR insert. CIDR inserts were removed on d 7. Cows in the GnRH group received PGF on d 6 and GnRH at insemination which occurred 48 h after CIDR removal. Cows in the E17 group received PGF on d 7, E17 24 h later, and were inseminated 30 h after E17 administration. Pregnancy rate to FTAI was higher for cows treated with E17. These data indicate acceptable pregnancy rates were obtained when the CIDR insert was combined with either GnRH in beef heifers or with E17 in Brahman cows.Item Understanding Beef Cattle Efficiency: I) Understanding Physiological and Digestive Factors Affecting Residual Feed Intake and II) Tannin Supplementation: Effects on Animal Performance, Fermentation, and Carcass Traits(2010-10-12) Krueger, Wimberley K.Objectives of this study were 1) to characterize the relationship between beef cattle efficiency, namely residual feed intake (RFI), and digestive, microbial, and fermentation parameters in growing beef calves and 2) to examine the effects of added dietary hydrolysable or condensed tannin on animal performance and efficiency, fermentation and carcass and non-carcass traits. To accomplish the first objective, multiple RFI studies were conducted and in all studies RFI was calculated as the difference between actual and expected dry matter intake (DMI) based on average gaily gain (ADG) and body weight0.75(BW). A total of 187 head selected out of a population of 600 head of growing beef calves were evaluated for diet and nutrient digestibility, ruminal and fecal volatile fatty acids (VFA) concentrations and methane producing activity (MPA). Low RFI calves consumed less DMI and had lower feed conversion ratios (FCR) as compared to high RFI calves. Low RFI calves also had higher diet and nutrient digestibilities compared to high RFI calves. Residual feed intake was negatively correlated with diet and nutrient digestibilities such that more efficient animals had higher digestibilities. Low RFI calves tended to have lower ruminal propionate and higher acetate:propionate ratios when fed a high-forage diet. Calves with divergent RFI did not have different gross microbial populations as evidenced by the Firmicute:Bacteriodetes ratio, but low RFI calves tended to have higher fecal Prevotella spp. and lower fecal Spirochaetes and ruminal Cyanobacteria. The importance of these subtle shifts in microbial ecology is not evident at this time and more research is needed to fully elucidate the interaction of host and microbes to fully grasp the importance of minor microbial deviations. No differences in 3 h MPA were detected in low vs. high RFI calves but low RFI calves had higher fecal MPA when sampled at 24 h; however, calculated methane emissions were lower for low RFI calves. Tannin supplementation had no effect on animal performance and efficiency, ruminal fermentation VFA concentrations, MPA, or ammonia concentrations in finishing beef steers. There was also no detrimental effect of tannins on carcass traits; however, hydrolysable tannin supplementation resulted in increased empty rumen mass. Results from these studies indicate that diet and nutrient digestibility are affected by RFI such that more efficient calves had higher DMD, microbial ecology is responsive to RFI such that minor microbial shifts were observed, and tannin supplementation, at the current inclusion rate, had no effect on animal and carcass performance.