Purebred Beefmaster steers (n = 160) from five owners were fed at a commercial feedlot in South Texas beginning in November of 2004; 68 steers possessed pedigree information. Beginning in mid-November, steers were individually weighed and evaluated for ultrasound body composition at 56-d intervals by a certified technician. Feeder calf frame (FRM) and muscle (MUS) scores were assigned at initial ultrasound evaluation. Steers were fed and marketed through a lean-based, branded beef program and were harvested in two groups in May and June of 2005 at a commercial beef plant. Analyses were conducted to investigate the ability to predict carcass traits from the different sources of information available on these cattle. Evaluation of carcass traits were investigated using four sets of independent variables referred to as sources A, B, C, or D and ultrasound scan session (1 – 4). An analysis included initial weight at first scan session (IWT), FRM and MUS as independent variables through GLM procedures. B analyses utilized ultrasound measures of the longissimus area, intramuscular fat, fat thickness, rump fat, and gluteus medius depth along with IWT as independent variables. Multiple regression was performed on each carcass trait using IWT and ultrasound traits at each scan session. Mallow’s CP was used to select a model that best described each carcass trait. C analyses (GLM) utilized variables from A and B analyses combined plus ranch. D analyses (GLM) included variables from C analyses plus sire nested within ranch. Respective R-square values (scan 1 – 4) for marbling score were .02, .04, .05, and .10 using A information, .14, .17, .42, and .54, using B information, .35, .35, .47, and .55 using C information, and .56, .59, .65, and .76 using D information. R-square values ranged from .34 to .86 for carcass weight, .11 to .77 for fat thickness, .06 to .82 for ribeye area, and .10 to .81 for yield grade. Ultrasound data obtained closer to harvest and increasing amount of data related to genetic and management background showed increased R-square values, but may be best utilized in conjunction with one another to predict carcass traits and final carcass value.

This study investigated the hypothesis that cattle fed to produce a lean carcass during a winter restriction period will subsequently grow faster and remain leaner than fatter steers during the summer, exploiting cheap grazed grass. Three studies were carried out; in the first study steers were restricted at three levels of growth (300, 600 and 900 g/day) during winter and turned out to graze grass during summer. At each level of growth during winter steers were fed on one of two diets aimed at producing steers of either a lean or fat carcass composition. At the end of the winter restriction period differences in lean composition were observed at the 300 and 600 g/day growth rates. Steers were slaughtered when they attained the target slaughter weight at the end of summer; but there was no difference between treatments in meat quality characteristics or fat composition. Liveweight gain during the summer period was inversely correlated to winter liveweight gain. Two further studies were carried out to assess the effect of altering carcass composition during winter, fed to a predicted growth rate of 600g/day to investigate the underlying physiological and endocrinological mechanism regulating the growth characteristics. In the first study at the end of winter steers that were fatter had higher glucose and insulin concentrations. No differences between diet treatments were detected in muscle protein synthesis or breakdown. At the end of the winter in the second experiment there were no differences in carcass composition, metabolite or hormone profiles between treatments. For both studies, at the end of summer, steers on different dietary treatments had similar carcass compositions and metabolic parameters. It was concluded that by altering the diet of steers during a winter restriction period the composition of carcass gain can be manipulated. Since steers altered the deposition of carcass protein and fat during the subsequent summer period at grass resulting in similar body compositions at slaughter it was deduced the that composition of steers at the end of winter remains unimportant. Reductions in beef production costs may be attained by restricting the growth rates during winter when commercial feeds are expensive.

No description available.

While the Southeastern U.S. does not produce cereal grains at the same output as Midwestern states, a relatively temperate climate and consistent rainfall allow for abundant forage production. Tall fescue dominated pastures in this region provide a high-quality forage source to support consistent cattle growth and production. Furthermore, the nearly year-round grazing potential serves as a cost-effective feed source. Leveraging forage resources is imperative for the U.S. beef industry to maintain consistent production of a quality human protein source at a consumer-friendly price, but energy content in purely forage diets is lacking to produce comparable growth and carcass performance to concentrate-based diets. Therefore, the objectives of this dissertation are to examine supplementation strategies for growing and finishing cattle in fescue-based systems in the Southeast to optimize value for cattle producers. The first experiment investigated whether steer performance and grazing behavior was affected by supplement feeding time and delivery method in a forage-based backgrounding program. Traditionally, producers choosing to supplement backgrounding cattle with grain or coproduct feeds do so in a single meal event in the early morning. It has been hypothesized that these morning feedings could disrupt the natural diurnal grazing pattern of cattle to negatively affect forage utilization and overall cost of gain. Additionally, while self-feeder systems using supplements containing intake limiters give producers an option to reduce feeding labor compared to daily hand-fed supplementation, alternate methods of supplement delivery also have the potential to influence grazing behavior and cost of gain within backgrounding programs. This experiment used backgrounding steers supplemented daily at 0930 (AM), steers supplemented daily at 1330 (PM), and steers provided supplement through a self-feeder (SELF) to provide cattle performance and economic data directly relevant to regional producers. Combined 2-yr results show that while AM, PM, and SELF cattle all exhibited altered grazing routines, treatments did not result in differences (P ≥ 0.18) in final body weight (BW), average daily gain (ADG), ultrasound 12th rib fat thickness (uFT), or overall forage mass disappearance. Dry matter intake (DMI) in the SELF treatment exceeded the target despite inclusion of intake limiters, resulting in increased (P < 0.01) supplement DMI, a tendency (P = 0.07) towards decreased G:F, and substantially greater (P < 0.01) cost of gain in SELF relative to the hand-fed treatments. Results support that producers have flexibility in scheduling daily supplementation routines without compromising steer performance in pasture-based backgrounding programs. Furthermore, producers should consider the tradeoff between labor efficiency and ration cost when considering utilizing self-feeders containing intake limiters. The second experiment investigated the effects of frame size and supplementation containing a rumen protected fat (RPF) on growth performance and carcass characteristics of pasture finished cattle. Market dynamics continue to favor cattle that produce heavier carcasses, which discounts smaller framed feeder calves at sale barns. At the same time, Virginia is flush with cow-calf production, high quality tall fescue pastures, and access to population dense areas with markets that incentivize pasture-finished beef through price premiums. Together, this provides an alternative marketing channel for smaller framed calves through pasture-finished beef markets, but questions remain on how to optimally produce this specialty beef. Supplemental feeds can increase cattle production on pasture, and RPF offer a feeding strategy to increase energy intake without negatively effecting ruminal fiber digestion. There is limited work investigating the application of RPF within beef cattle systems and carcass traits, and it is unclear if RPF has been utilized specifically within pasture finishing systems. Therefore, this experiment examined growth performance, carcass characteristics, and organoleptic qualities of beef from small-framed (SM) and medium-framed (MED) cattle on novel endophyte-infected fescue pasture finishing systems either offered no supplement (NON) or daily supplementation (SUP) containing RPF. Pasture treatments were compared relative to a grain-fed feedlot control (F) to show these cattle had the genetic merit to meet expectations of the U.S. fed-beef system. Results from this 2-yr experiment indicate that frame size had little impact on growth performance, with SM and MED cattle having similar (P ≥ 0.37) final BW, ADG, and forage DMI in this pasture finishing system. However, MED cattle produced more valuable carcasses compared to SM cattle as evident by greater (P ≤ 0.04) mean HCW, 12th rib fat thickness, and marbling score. Samples of M. longissimus thoracis from MED cattle also had greater (P ≤ 0.02) concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids compared to samples from SM cattle. While NON cattle produced carcasses with a lower (P = 0.01) yield grade than SUP cattle, overall, SUP cattle were more productive by both live and carcass metrics. The SUP treatment produced greater (P ≤ 0.04) final BW, ADG, 12th rib fat thickness, HCW, marbling score, dressing percentage, and concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids. Similarity (P = 0.55) in objective measures of meat tenderness between F and pasture treatments emphasizes the importance of harvesting cattle before 2 years of age to prevent declines in meat tenderness associated with advancement of connective tissue. There tended (P = 0.05) to be a frame by supplement interaction for marbling score driven by lower values in SM-NON in relation to other pasture treatments. Tendencies towards frame by supplement interactions for Warner-Bratzler shear force (P = 0.08) and total energy (P = 0.06) were also driven by increased values in SM-NON relative to other pasture treatments. Taken together, a lack fat deposition in SM-NON cattle appears to have a negative impact on beef tenderness relative to pasture treatments. Overall results of this experiment support low levels of supplementation in pasture-finishing systems to improve carcass value, and that medium framed cattle are more flexible in profit margins compared to smaller framed counterparts. Collectively, these investigations support that tall fescue grazing systems in the Southeast can serve as a nutritional foundation to beef cattle growing and finishing enterprises. Data from these experiments can be directly applied to help producers match cattle type to feed resources when supplementing a pasture-based system to optimize resource management and overall profitability. / Doctor of Philosophy / The U.S. beef cattle industry is unique to any other commercial food animal enterprise. Smaller animals like poultry and swine can be raised within enclosed spaces to control temperature, humidity, and airflow. Beef cattle, however, require a larger land footprint and more feed resources per animal. This exposes cattle to the volatility of outdoor production, which adds another set of variables that cattle managers must account for. Additionally, cattle have the longest lifecycle from conception to harvest relative to all other livestock species, so cattle producers are more vulnerable to long-term financial risk. Despite these challenges the U.S. beef industry succeeds by organizing cattle production into multiple interconnected business sectors. Segmenting the beef cattle industry allows producers to tailor their management practices to what works within their region of the country based on unique resources, climate patterns, and especially feed availability. Collectively the parts of the beef industry work as a dynamic system, but this also creates cattle with a variety of physical characteristics and genetics to complement the array of production styles. Different types of cattle can be valued differently depending on what traits consumers in a specific market desire. Therefore, sustained economic success in the cattle industry often comes down to pairing different cattle management systems with the correct end consumer market. Approximately 20% of the U.S. cattle population resides in Southeastern states where relatively temperate climates and consistent rainfall allows for abundant availability of high-quality forage. Especially in states like Virginia, tall fescue and other cool-season grasses provide nearly year-round forage growth for cattle to graze as a relatively inexpensive and abundant feed supply. However, forages lack the nutrient density of cereal grains, which support higher rates of growth and produce beef with an eating experience that the American palate has grown accustomed to. This creates a gradient of cattle nutritional strategies ranging from primarily forage-based cattle production on one end to primarily grain-based strategies on the other. Therefore, the objective of this dissertation was to evaluate supplementation strategies for growing and finishing beef cattle in fescue-based production systems in the Southeast from the perspectives of both live cattle and meat production. Backgrounding systems are a transitional period following weaning that focuses on lean growth to prepare yearling calves for the feedlot finishing phase. Cattle on these traditionally forage-based systems are frequently supplemented with grain or grain coproduct feeds to increase weight gain, but supplement delivery method and time of feeding varies between producers. This could influence natural cattle grazing cycles to negatively impact pasture utilization, which would increase the cost of gain. Over a 2-yr study post-weaning cattle growth performance and grazing behavior were compared between backgrounded cattle supplemented by hand in the morning, by hand in the afternoon, or through a self-feeder. Although altering the time of day that supplements were provided to cattle changed daily grazing routines, there were no differences in weight gain, body composition, or forage disappearance between all 3 treatments. Self-fed cattle had nearly twice the cost of gain compared to hand-fed cattle, highlighting the importance of accounting for cost of gain when making nutritional program decisions. Market dynamics favor cattle that produce heavier carcass weights, but this has led to smaller framed feeder calves receiving discounts at sale barns. The Southeast is flush with cow-calf production, abundant forage resources, and population dense areas that incentivize pasture-finished beef. This creates opportunity for cattle producers looking to increase the value of smaller framed calves through premiums in specialty beef markets. A 2-yr study examined the effects of frame size and supplementation containing a rumen protected fat on cattle growth performance, forage utilization, and carcass characteristics. Small framed and medium framed cattle on novel endophyte-infected tall fescue pastures were either received daily supplementation or no supplement and were compared against a grain-fed control group. Smaller framed cattle grew at a slower rate relative to medium framed cattle, and produced less valuable carcasses in terms of both the amount of beef produced and meat quality. Low levels of supplementation improved growth performance and carcass value, but overall medium frame, unsupplemented cattle had the greatest profit flexibility relative to other pasture treatments. Collectively, these experiments highlight the profit potential of forage-based beef cattle production in the Southeast. The beef industry will have to continue to adapt to produce more beef to feed a growing global population through tighter constraints, and forage resources will play a key role in providing a cost-effective, high quality feed source. Accounting for differences in resource management, end markets, and cattle type is paramount in maintaining a sustainable and profitable U.S. beef industry.

No description available.

This study was conducted to assess cutout and value differences in Yield Grade 4 beef carcasses by evaluating impacts of gender, fatness, muscling, and weight. USDA Choice, Yield Grade 4 carcasses (n = 60) were selected according to gender: heifers (n = 20) and steers (n = 40), and weight groups: lightweight heifers (315.5 - 362.9 kg) and steers (362.9 - 408.2 kg), and heavy weight heifers (362.9 - 408.2 kg) steers (408.2 - 453.6 kg). Within weight classes, carcasses were separated according to ribeye area per 45.36 kg of HCW ratio (REAcm2 :100 kg): heifers (>21.76) and (< or equal to 21.76); steers (greater than 20.07) and (less than or equal to 20.07) based on analysis from NBQA-2005 (National Beef Quality Audit - 2005). Data in this study showed that within yield grade 4 carcasses, there are both conformational and value differences associated with different types of yield grade 4's, particularly when sex-class is considered due to the biological differences associated with fat and muscle deposition between genders. As expected, carcasses from heifers had more trimmable fat than steers, and steers had higher yields of certain cuts from the chuck and in bone differences than did heifers. In this demonstration, applied estimated discounts out-weighted the value differences found in cutout values. There were no clear associations in carcass traits that could be used to more accurately sort value differences in Yield Grade 4 carcasses with exception to sex-class. However, the present data suggests a need to establish a prediction equation that predicts carcass value in addition to the current Yield Grade equation. In conclusion, further research is needed incorporating all yield grade carcass types. Standard carcass fabrication styles and fat trim levels consistent with industry are needed to further assign current subprimal and minor cut prices. Additional premium and discount prices are needed for a current industry representation to obtain if premiums and discounts are being applied according to potential profits or losses incurred because of cutability differences found between the different yield grades.

During the harvesting process, meat products can become contaminated with enteric pathogens, such as Escherichia coli O157:H7 and Salmonella Typhimurium. Surrogates for these pathogens would be beneficial for validating carcass decontamination treatments. Surrogate organisms are organisms that behave similarly to specific pathogens but are non-pathogenic and can be used to determine efficacy of decontamination regimes for pathogens. The surrogates proposed are non-pathogenic, ampicillin-resistant E. coli biotype I strains that were previously isolated from beef cattle hides. Each E. coli strain was transformed to express a fluorescent protein (red: EcRFP; green: EcGFP; yellow: EcYFP) that is detectable under an ultraviolet light source. Surface areas on hot boned beef carcasses (clod, brisket, outside round) were inoculated with a fecal slurry containing EcRFP, EcGFP, EcYFP and rifampicin-resistant E. coli O157:H7 and S. Typhimurium. Surface regions were then treated in a model spray cabinet using an initial water wash (28ºC) followed by treatments using 2% L-lactic acid (55ºC), hot water (95ºC at source) or a combination of the two. Treatments were compared for their effectiveness at reducing populations of inoculated (4.7 to 6.7 log CFU/cm2) E. coli, S. Typhimurium, EcRFP, EcGFP and EcYFP. Log reductions for inoculated organisms were calculated individually and then total and average surrogate cocktail values were calculated. All decontamination treatments reduced the inoculated numbers of pathogens and surrogates to near or below the detection limit of 0.5 log CFU/cm2. The combined treatment resulted in the greatest log reductions. The three individual surrogate organisms varied in log reductions according to the different decontamination treatments applied; however, log reductions for the total surrogate cocktail did not differ significantly from that of E. coli O157:H7. With the exception of EcYFP, the individual surrogates and average surrogate cocktail were significantly more resistant to microbial interventions including lactic acid than S. Typhimurium. Because abattoirs utilize different carcass decontamination treatments, it is difficult for one single fluorescent protein-producing isolate to accurately represent the behavior of E. coli O157:H7 or S. Typhimurium. Instead, surrogates should be used as a total cocktail to accurately represent the effectiveness of different treatments for reduction of enteric pathogens.

Steers produced in Cycle I of the Texas A & M University McGregor Genomics Project (n = 232, F2 Nellore-Angus) were evaluated for carcass composition, visceral organ weights, and model predicted residual consumption (MPRC), a measure of feed efficiency. Hot carcass weight was strongly correlated with liver weight (r = 0.70, P < 0.001) heart weight (r = 0.58, P < 0.001), and viscera weight (r = 0.55, P < 0.001) but not spleen weight (r = -0.01, P = 0.83). Liver, heart and viscera weights were moderately positively correlated with external and kidney pelvic heart fat (KPH), but not with marbling. None of the organ weights were correlated with MPRC. A subset of 54 animals was selected for extreme values of residuals of MPRC after a mixed model analysis that included fixed effects of sire and family nested within sire, and these animals were evaluated for insulin-like growth factor I (IGFI) expression in liver samples collected at harvest through quantitative real time polymerase chain reaction (qRT-PCR). IGFI relative quantity (IGFI RQ) was collected from qRT-PCR and was correlated with liver (r = -0.23, P = 0.09), spleen (r = 0.48, P <0.001) and viscera weight (r = 0.24, P = 0.08), but not any carcass trait or MPRC residual. Gene breed types were determined for 4 candidate genes of feed efficiency: insulin like growth factor-1 (IGF1), leptin (LEP), neuropeptide-Y (NPY) and ghrelin (GHRL). Gene breed types were represented as AA, AN, NA, and NN where A and N denote Angus and Nellore, respectively, and paternal inheritance is listed first. Given that contemporary group significantly influenced most traits (MPRC, all carcass traits, liver weight and viscera weight), effects of gene breed type and contemporary group were evaluated together in analyses. GHRL influenced liver (P = 0.02) and viscera weight (P = 0.02), IGF1 influenced kidney, pelvic, and heart fat (P = 0.05), NPY influenced liver weight (P = 0.03) and hot carcass weight (P = 0.04), and LEP influenced ribeye area (P = 0.05) and hot carcass weight (P = 0.04) with a tendency to influence liver weight (P = 0.06). Alternate heterozygotes for GHRL were statistically different in liver weight and viscera weight where NA was heavier than AN. Alternate heterozygotes for LEP did not differ in ribeye area, hot carcass weight, or liver weight. Alternate heterozygotes for NPY differed in liver weight (NA heavier than AN), but did not differ in hot carcass weight. Carcasses with AA for LEP and NPY were 18 to 19 kg heavier (P < 0.05) than those with NN, with heterozygotes intermediate.

Food safety is a critical issue for beef harvest operations. There are multiple interventions available for treating carcasses; however, this project was designed to evaluate an intervention capable of reducing bacterial counts on the hide prior to opening in order to minimize carcass contamination. In Trial I, fresh beef hides (n = 12) were cut into sections and assigned to serve as either clipped (hair trimmed) or non-clipped sections. Sections were inoculated with a bovine fecal slurry and sampled following a water wash. Treatments (distilled water, isopropyl alcohol, 3% hydrogen peroxide, 2% L-lactic acid, 1% cetylpyridinium chloride (CPC), and 10% Povidone-iodine) then were applied to each section and sampled for aerobic plate counts (APCs), coliform, and Escherichia coli counts. Within clipped samples, 1% CPC and 3% hydrogen peroxide caused the greatest reductions in aerobic plate counts, and 1% CPC, 2% L-lactic acid, and 3% hydrogen peroxide showed among the greatest reductions in coliform counts. In Trial II, beef carcasses with hides on were sampled initially and clipped, and then antimicrobials (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) were applied before sampling again for APC, coliform, and E. coli counts. This procedure was replicated in Trial II utilizing a non-pathogenic E. coli Type I indicator strain transformed to produce a green fluorescing protein (GFP). In Trial II, though few differences existed between antimicrobial treatments, all three (1% CPC, 2% L-lactic acid, and 3% hydrogen peroxide) resulted in approximately a 2-log10 CFU/100-cm2GFP reduction when applied to clipped hide surfaces in the brisket region of the carcass. In Trial III, 1% CPC produced the greatest reduction on the hide surface for APCs. In Trial IV clipped beef hide sections were sampled initially and then antimicrobials (2% L-lactic acid, 3% hydrogen peroxide, and 1% CPC) were applied before sampling again to determine reduction. Trial IV also involved the use of the E. coli GFP indicator strain. In Trial IV, non-clipped samples had a mean reduction of 2.8 log10 CFU/100 cm2, and clipped samples had a mean reduction of 2.2 log10 CFU/100 cm2. Within the antimicrobials tested, 1% CPC and 3% hydrogen peroxide produced the greatest reductions.

Forty eight crossbred steers (BW = 296 ± 16.7 kg) were fed four dietary treatments for 56 d: AL-LS (low starch diet fed ad libitum for a rate of gain of 1 kg/d), AL-HS (high starch diet fed ad libitum), LF-HS (a limit fed high starch diet designed to be isocaloric with AL-LS), and AL-IS (a diet fed ad libitum for the midpoint daily energy intake between AL-LS and AL-HS). On d 57 all steers were placed on AL-HS for finishing until d 140. Steers that consumed more total energy (AL-HS and AL-IS) throughout production achieved greater carcass fatness in the end of the 140 d period, although these responses were difficult to evaluate via real-time ultrasound measurements. No differences in insulin and glucose kinetics were observed. Data suggested that energy source may influence energy partitioning during the growing period, but these effects may be overcome by differences in energy intake. Higher marbling scores (AL-HS and AL-IS) rewarded higher grid values and greater premiums, which increased profitability. This data set was also used for a model evaluation that showed that mathematical models (CVDS and NRC) were able to explain most of the variation in individual feed requirements of group- fed growing and finishing cattle. Another data set was used for evaluation of a decision support system Cornell Net Carbohydrate and Protein System (CNCPS) as a tool to minimize nutrient excretion from fed cattle. One-hundred eight-four group- fed steers were fed a 13% crude protein (CP) diet until reaching 567 kg of BW, when their diets were either maintained at 13% or reduced to 11.5% or 10% CP. Data from the second half of the experiment were modeled to predict urinary, fecal, and total N excretion. As dietary CP decreased from 13 to 11.5%, the model indicated a total N excretion of 16%. An even greater reduction in total N excretion (26%) occurred when dietary CP was decreased from 11.5% to 10%. The overall decrease from 13 to 10% CP resulted in a reduction of total N excretion by 38%. Data suggest that decision support sys tems can be used to assist in balancing diets to meet environment restriction.