Taurus Steers Research Articles

PSX-14 Effect of starch supplementation on rumen bacterial abundance in Bos taurus taurus steers consuming low-quality forage

Abstract Low-quality forage provides a limited supply of ruminally available nitrogen and is generally resistant to digestion, inhibiting microbial growth in the rumen and ultimately decreasing forage utilization. Supplementation with protein is well documented to increase forage utilization by promoting microbial growth. Even when protein requirements are met, additional energy, often provided as starch, may be required to meet performance expectations. The objective of this study was to evaluate the effect of increasing starch supplementation on rumen bacterial populations in Bos taurus taurus steers supplemented protein and consuming low-quality forage. Ruminal samples were collected from ruminally-cannulated Angus steers [n = 5; body weight (BW) = 375 ± 45 kg] used in a 4 × 4 Latin square fed a basal diet of King Ranch Bluestem Hay (3.5% CP, 73% NDF) ad libitum, and supplemented with one of four isonitrogenous (130 mg N/kg BW) supplements with increasing starch (2% starch = 100% soybean meal; 20% starch = 73% soybean meal, 26.2% corn, 0.8% urea; 38% starch = 47% soybean meal, 51.6% corn, 1.4% urea; 56% starch = 19% soybean meal, 78.6% corn, 2.4% urea). Rumen content samples were collected via rumen cannula 4 h after supplementation and immediately frozen. Microbial DNA was extracted; full length 16S rRNA amplicon libraries were prepared using Kinnex kits and sequenced on the PacBio Revio platform. Reads were analyzed using DADA2 and QIIME2. Statistical analysis was performed with the GLIMMIX procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). Firmicutes and Bacteriodata were the most abundant phyla in all treatments (82% and 11%, respectively), and were not affected by starch supplementation (P ≥ 0.45). Actinobacteriota and Euryarchaeota abundance responded quadratically (P < 0.01) to increasing starch provision. Christensenellaceae R-7 group, Rikenellaceae RC9 gut group, Lachnospiraceae XPB1014 group, Butyrvibrio, Lachnospiraceae NK3A20 group, and Prevotella represented the most abundant genera for all treatments. Increasing supplemental starch resulted in a quadratic response (P < 0.01) for abundance of Christensenellaceae R-7 and Lachnospiraceae XPB1014 groups. Relative abundance of Butyrvibrio was 4.05% for steers fed 2% starch supplement and increased to 18.24 and 11.85% for 20 and 38% starch, respectively and then decreased to 4.34% for steers fed 56% starch supplement (quadratic, P < 0.01) Abundance of Pseudobutyrvibrio followed a similar but less dramatic pattern (quadratic, P < 0.01). In contrast, abundance of Streptococcus and Methanobrevibacter decreased with the first two levels of starch and then increased with 56% (quadratic; P < 0.01). In conclusion, responses to the first two increments of starch supplementation suggest increased fibrolytic and decreased methanogenic activity. These results are supported by the previously reported increase in TDOMI for 20 and 38% starch 49.0 and 48.2 g/kg MBW, respectively versus 45.7 and 44.3 g/kg MBW for 2 and 56%, respectively.

PSIX-19 Effect of protein and starch level on N balance and ruminal fermentation parameters in steers consuming low-quality forage: Bos taurus taurus

Abstract Globally cattle convert low-quality forage to beef and milk; therefore, understanding protein utilization in Bos taurus taurus is critical to enhancing sustainability as over and under-supplementation of protein are economically and environmentally costly. Low-quality forage lacks the N necessary for proper utilization and metabolic function. Supplemental protein improves low-quality forage utilization and is expected to increase N absorption and retention. Supplement starch can increase volatile fatty acid (VFA) production and energy supplied to the animal; however, too much starch decreases ruminally available N and pH potentially decreasing fibrolytic activity. Accordingly, our objective was to determine the effect starch supplementation on N balance and ruminal fermentation parameters in Bos taurus steers. Ruminally cannulated Angus steers [n = 5; body weight (BW) = 375 ± 45 kg] were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. Supplemental N intake decreased linearly (P < 0.01) with increasing starch as the crude protein content of the soybean was underestimated. Forage and total N intake were not affected by starch level (P ≥ 0.17). Fecal and total urinary N excretion were not different between starch levels (P ≥ 0.43). Urinary ammonia-N and urea-N averaged 6.6 and 16.8% of total urinary N excretion, respectively, but no differences between starch levels were observed (P ≥ 0.39). Level of starch supplementation had no effect on N retention and absorption (P ≥ 0.50). There was a treatment × time interaction observed for ruminal ammonia concentration (P < 0.01). All treatments, except 2% starch, peaked at 4 h post feeding, 20 and 38% treatments gradually decreased following four, but the concentration of ruminal ammonia decreased by 80% between 4 h and 8 h after feeding in the 56% starch treatment. Starch level had no effect total VFA concentration, VFA molar proportions, or ruminal pH (P ≥ 0.10). In conclusion, providing supplemental starch did not affect N balance or VFA production when fed to steers consuming low-quality forage. Nitrogen balance and VFA production likely were not affected because all supplements provided sufficient ruminally available N and, therefore, exerted minimal effects on forage utilization.

363 Effect of Protein and Starch Supplementation Level on Intake and Digestibility By Steers Consuming Low-Quality Forage: I. Bos Taurus Taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage depresses forage utilization. Supplemental protein improves forage utilization by increasing RAN, resulting in increased intake and potentially improving digestion. Addition of starch to a supplement can increase total digestible OM intake (TDOMI); however, too much starch decreases RAN creating competition between fiber and starch fermenting bacteria potentially decreasing forage utilization. Our objective was to determine the effect of starch supplementation on intake and digestion in Bos taurus taurus steers. Accordingly, five ruminally cannulated Angus steers (BW 375 ± 45 kg) were used in a 4 × 4 Latin square to evaluate the effect of decreasing supplemental starch when consuming King Ranch Bluestem hay (3.5% CP, 73% NDF). Steers received four isonitrogenous (130 mg N/ kg BW) supplements providing increasing levels of starch (2% starch = 100% soybean meal; 20% starch = 26.3% corn, 73% soybean meal, 0.7% urea; 38% starch = 51.6% corn, 47% soybean meal, 1.4% urea; 56% starch = 78.6% corn, 19% soybean meal, 2.4% urea). Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. As designed, supplement OM intake (SOMI) increased linearly (P < 0.01) as starch level increased. Forage OM intake (FOMI) decreased linearly with increasing starch (P < 0.01). Increases in SOMI and decreases in FOMI combined to result in no significant (P ≥ 0.14) differences in total OMI (TOMI) between starch levels. Total digestible OMI (TDOMI) responded quadratically (P = 0.05) to increasing starch and was 45.8, 49.4, 48.4 and 41.9 g TDOMI/kg BW0.75 for 2, 20, 38, and 56% starch, respectfully. Total DOMI was 18% greater when steers were provided 20% starch supplement compared with 56% starch. Similarly, total digestible NDF intake responded quadratically (P = 0.05) and was maximized with 20% starch. Total tract OM digestion and NDF digestion were not significantly affected (P ≥ 0.15) by starch level in the supplement. In conclusion, providing supplemental starch over 20% decrease forage utilization. Decreases in FOMI with starch inclusion may be attributed to competition for RAN between fiber fermenting and starch fermenting bacteria.

PSII-22 Effect of Protein Supplementation Level and Degradability on N Balance By Steers Consuming Low-Quality Forage: I.Bos Taurus Taurus

Abstract Globally, cattle convert low-quality forage to beef and milk; therefore, understanding protein utilization in Bos taurus taurus is critical to enhancing sustainability as over and under-supplementation of protein are economically and environmentally costly. Low-quality forage lacks the N necessary for proper utilization and metabolic function. Supplemental protein improves low-quality forage utilization and is expected to increase N absorption and retention. Accordingly, our objective was to determine the effect of ruminal degradability and level of protein supplementation on N balance in Bos taurus taurus steers. To achieve this objective, six ruminally cannulated Angus steers (BW 294 ± 37.7 kg) were used in a 5 × 5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2 × 2 factorial steers receiving protein supplements (43% CP) with two ruminal degradable protein levels; 35% RDP (35%; 58% corn gluten meal and 42% soybean hulls) and 70% RDP (70%; 100% soybean meal). Supplements were fed at two levels, providing 1.26 or 2.53 g of supplement/kg BW (LOW and HIGH, respectively). A control (CON) provided no supplement. Five, 14-d periods, consisted of 9 d adaptation and 4 d to measure intake, digestion, and N balance, and 1 d for ruminal fermentation. No significant (P ≥ 0.14) degradability × level interactions were detected for any measures of N balance. Although forage organic matter intake increased (P < 0.01) in response to supplementation, forage N intake was not improved. Supplemental N intake increased linearly (P < 0.01) with increased supplementation, as designed, resulting in a significant linear (P < 0.01) increase in total N intake. In addition, 70% RDP supplement resulted in greater supplemental N intake than the 35% RDP supplement. Fecal N excretion increased linearly with supplementation. Supplementation at the HIGH level increased (P < 0.01) fecal N excretion 90% compared with CON. There was no significant (P = 0.94) effect of ruminal degradability. Urinary N excretion was greater (P < 0.01) when the 70% RDP supplement was fed than the 35% RDP. Nitrogen absorption linearly increased with supplementation (P < 0.01). Similarly, nitrogen retention linearly increased (P < 0.01) with level of supplementation but was not significantly affected by degradability (P = 0.87). In conclusion, providing supplemental N to Bos taurus taurus increased N intake, excretion, absorption, and retention. Level of ruminal degradability did not affect N retention or absorption suggesting that protein supplementation regardless of ruminal N degradability improves N balance in Bos taurus taurus consuming low-quality forage.

Carcass traits and meat lipid profile of cull cows fed palm kernel cake

Context Among the by-products derived from oilseeds, palm kernel cake (PKC) contains high concentrations of protein, fat, and fibre, which allows some flexibility in the use of this ingredient in ruminant diets. Aim This study examined the effects of including palm kernel cake (PKC) in high-grain diets for cull cows on production performance, carcass traits, and meat fatty acid profile. Methods Thirty-six ½ Girolando cows at 83 ± 5 months of age, with an average liveweight of 384.88 kg ± 59.18, were confined in collective stalls for 90 days. The animals were distributed into the following four diet groups: 0% (control), 8%, 16%, or 24% inclusion of PKC in the diet dry matter (DM). Key results On the basis of regression analysis, the highest slaughter weight and carcass weight were at PKC inclusion levels of 11.5% and 10.3% respectively. Backfat thickness was greatest (8.8 mm, P < 0.01) in the carcasses of cows fed the diet with 15.1% PKC (on the basis of regression analysis), whereas the total lipid content in the meat decreased linearly (P < 0.05) with PKC inclusion. The C10:0, C12:0, C14:0, C14:1, C16:0, C16:1, C17:1, C18:0, C18:2n6t, and C20:5n3 fatty acids in the longissimus thoracis muscle responded quadratically (P < 0.05) to the inclusion of PKC. The highest concentration of desirable fatty acids was obtained with the inclusion of 11% PKC in the diet (on the basis of regression analysis). There was a linear increase in C14:1, C20:2, and C22:2 fatty acids and Δ9 desaturase 14 and 16 activity indices in the muscle of cows fed PKC. Conclusion We recommend the inclusion of 10% PKC in the diet of cull cows fed high-grain diets. Intramuscular fatty-acid proportions were appreciably different from those reported for young B. taurus steers and heifers finished on high-concentrate diets. Implications Therefore, inclusion of PKC is an excellent alternative to reduce production costs, having the availability and quality of the product as a limiting factor, since PKC is an industrial by-product.

PSII-3 Effect of Protein Supplementation Level and Degradability on Forage Utilization by Steers Consuming Low-Quality Forage: II. Bos taurus indicus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage may depress forage utilization. Supplemental protein improves utilization by addressing the RAN therefore increasing intake and potentially improving digestibility. The objective of this study was to determine the effect of ruminal degradability and level of protein supplementation on forage utilization by Bos taurus indicus steers. Accordingly, five ruminally cannulated Brahman steers (BW 369 ± 51 kg) were used in a 5 × 5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming a basal diet of King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2 × 2 factorial with steers receiving protein supplements (43% CP) having two levels of protein degradability (35 or 70% RDP) fed at two levels of supplementation, 1.26 or 2.53 g/kg BW (LOW and HIGH). A control treatment providing no supplemental protein was also included (CON). Five 14-d periods were conducted, consisting of 9 d adaptation, 4 d to measure intake and digestion, and 1 d for ruminal fermentation. No degradability × level interactions were observed for any measures of intake or digestion (P > 0.10). Protein supplementation linearly increased (P < 0.01) total digestible OM intake (TDOMI), NDF intake (P = 0.01), and total digestible NDF intake (DNDFI; P < 0.03). Total digestible OMI was greater in steers receiving 70% RDP than the 35% RDP (P = 0.08). This response resulted from the linear increase in FOMI with 75% RDP (P = 0.03), that was not observed with 35% RDP. Despite differences in FOMI, TDOMI increased linearly (P ≤ 0.03) for both 35 and 70% RDP, partially the result of providing a highly digestible supplement. Forage OMI differences also resulted in NDFI being greater for 70% RDP than 35% RDP (P = 0.06) and DNDFI increasing linearly with the addition of both supplements (P ≤ 0.03). Organic matter digestibility (OMD) increased linearly with supplementation as a result of supplement provision. In contrast to observations previously reported in Bos taurus steers, provision of 35% RDP supplement did not improve FOMI. Supplementation with 70% RDP improved FOMI 19 and 20% compared to the basal diet at LOW and HIGH levels, respectively. A portion of this relatively modest response to protein supplementation could be attributed to greater intake in the unsupplemented controls.

PSII-2 Effect of Protein Supplementation Level and Degradability on Forage Utilization by Steers Consuming Low-Quality Forage: I. Bos taurus taurus

Abstract A deficiency of ruminally available N (RAN) caused by a basal diet of low-quality forage may depress forage utilization. Supplemental protein improves utilization by increasing RAN therefore increasing intake and potentially improving digestibility. The objective of this study was to determine the effect of ruminal degradability and level of protein supplementation on forage utilization by Bos taurus taurus steers. Accordingly, six ruminally cannulated Angus steers (BW 294 ± 37.7 kg) were used in a 5×5 Latin square to evaluate the interaction between level and degradability of protein supplementation when consuming King Ranch Bluestem hay (3.5% CP, 71.0% NDF). Treatments were arranged as a 2×2 factorial with steers receiving protein supplements (43% CP) with two levels of protein degradability (35 or 70% RDP) fed at two levels of supplementation, providing 1.26 or 2.53 g/kg BW (LOW and HIGH). A control treatment (CON) provided no supplemental protein. Five 14-d periods were conducted, consisting of 9 d adaptation and 4 d to measure intake and digestion, and 1 d for ruminal fermentation. No degradability × level interactions were significant for any measures of intake or digestion, although there was a tendency for an interaction (P = 0.09) for total organic matter intake (TOMI), resulting from a tendency for a quadratic (P = 0.08) increase when supplemented. In contrast, the 70% RDP supplement continued to increase TOMI linearly (P < 0.01), suggesting the maximum effective level of supplementation was not reached. As expected, protein supplementation increased all measures of intake such as, forage OMI (FOMI), total digestible OMI (TDOMI), and NDF intake (P < 0.01). In addition, level of supplementation affected all measures of intake (P ≤ 0.01) with HIGH being greater than LOW. Protein supplements with 70% RDP at LOW increased FOMI 28% versus control when supplemented at LOW, and 47% at HIGH. Supplementation with 35% RDP increased FOMI 23% at the LOW and 28% at HIGH indicating the lower degradability supplement was less effective at improving forage utilization that the 70% RDP supplement (P = 0.01). Total NDF intake (NDFI) followed this same pattern with 70% RDP supplementation increasing NDFI 29 and 52% with LOW and HIGH supplementation, respectfully; 28 and 37% when 35% RDP supplementation was provided (P = 0.10). Despite the effect of protein supplementation on intake, OM digestion (OMD) and NDF digestion (NDFD) were not affected by protein supplementation regardless of degradability or level (P ≥ 0.23). In conclusion, FOMI and TDOMI were increased with the provision of greater levels and more degradable supplements resulting in better forage utilization.

PSXII-19 Organ and cellular contributions to heat production in Brahman and Angus steers

Abstract Reductions in basal metabolism and growth rate appear to contribute to decreased heat production of Bos indicus breeds. Lower metabolic rate may be due to smaller organ size and lower metabolic activity. Liver and heart account for high percentage of metabolic activity relative to their weight, and at a cellular level, mitochondria are responsible for producing energy for cellular maintenance. Our objective was to determine liver and heart weight and evaluate expression of key mitochondrial proteins in Bos indicus (80–100% Brahman) and Bos taurus (80–100% Angus) steers. Steers (n = 14 per breed) were harvested at the university meat laboratory. After evisceration, livers and hearts were weighed, and samples were frozen in liquid nitrogen for further analyses. Western blotting was used to determine expression of proteins in mitochondrial energy production: citrate synthase, a marker of mitochondria content; succinate dehydrogenase B (SDH-B), complex II; cytochrome c oxidase subunit IV, complex IV; and ATP synthase subunit 5A (ATP5A), complex V. Data were analyzed using an unpaired t-test in SAS-JMP. Although steers were similar age at slaughter (P = 0.84), Brahman steers weighed less (P < 0.0001) and thus produced lighter carcasses (P < 0.0001) and smaller livers and hearts (P < 0.0001). On a relative basis (kg organ/kg BW), Brahman tended to possess smaller hearts (P = 0.06) and smaller livers (P = 0.03). Expression of mitochondria proteins in heart did not differ between breeds (P > 0.3). However, Brahman exhibited lower expression of SDH-B (P = 0.005) but tended to have higher expression of ATP5A (P = 0.07) in liver. Altogether, this supports that smaller organ size is a contributing factor to lower heat production in heat-tolerant Brahman steers, and shifts in mitochondria protein expression in liver may impact energy metabolism at the cellular level.

PSII-4 Changes in body temperature of lot-fed Bos taurus and Bos indicus steers during a heat wave

Abstract Body temperature (BT) is a reliable method for evaluating the thermal status of cattle. The objective of this study was to evaluate the regulation of BT in B. indicus and B. taurus steers during a heat wave event. Thirty-five steers (466.30±10.2kg) of mixed genotypes (B. taurus, n = 18; B. indicus, n = 17) were used in a larger 100-d study. Cattle were housed in six un-shaded pens at a commercial feedlot. Body temperature data for this were obtained at 1 h intervals over a 3-d heat wave event using in situ abdominal data loggers. Data were analysed using a repeated measures model, using residual maximum likelihood estimation. The model included genotype (B. taurus; B. indicus) and animal ID as random effects and hour as a fixed effect. Mean maximum BT occurred at 1500 h for B. taurus (40.52±0.03ºC) and 0400 h for B. indicus (40.48±0.31ºC). The BT of B. indicus decreased between 0400 h and 0700 h, and then increased to 1100 h (+0.10±0.01ºC/h), before decreasing again. The BT of B. taurus decreased between 0500 h and 0600 h, and then slowly increased (+0.04±0.01ºC/h) to 1500 h. Mean minimum BT occurred at 2100 h for B. taurus (40.12±0.11ºC) and 0700 h for B. indicus (40.00±0.22ºC). B. taurus maintained lower BT (40.21±0.05ºC) between 1900 h and 2200 h compared to B. indicus (40.27±0.05ºC) which may be due to disrupted heat loss mechanisms during the day, highlighting the importance of night time cooling. In response to increasing heat load, BT in B. taurus had slower increases but retained heat for longer, whilst B. indicus BT responded by a series of rapid increases and decreases. Developing an understanding of the differences in BT regulation in B. indicus and B. taurus will allow for more effective heat load management strategies during heat waves to be established.

147 Changes in body temperature of lot-fed Bos taurus and Bos indicus steers during a heat wave

Abstract Body temperature (BT) is a reliable method for evaluating the thermal status of cattle. The objective of this study was to evaluate the regulation of BT in B. indicus and B. taurus steers during a heat wave event. Thirty-five steers (466.30±10.2kg) of mixed genotypes (B. taurus, n = 18; B. indicus, n = 17) were used in a larger 100-d study. Cattle were housed in six un-shaded pens at a commercial feedlot. Body temperature data for this were obtained at 1 h intervals over a 3-d heat wave event using in situ abdominal data loggers. Data were analysed using a repeated measures model, using residual maximum likelihood estimation. The model included genotype (B. taurus; B. indicus) and animal ID as random effects and hour as a fixed effect. Mean maximum BT occurred at 1500 h for B. taurus (40.52±0.03ºC) and 0400 h for B. indicus (40.48±0.31ºC). The BT of B. indicus decreased between 0400 h and 0700 h, and then increased to 1100 h (+0.10±0.01ºC/h), before decreasing again. The BT of B. taurus decreased between 0500 h and 0600 h, and then slowly increased (+0.04±0.01ºC/h) to 1500 h. Mean minimum BT occurred at 2100 h for B. taurus (40.12±0.11ºC) and 0700 h for B. indicus (40.00±0.22ºC). B. taurus maintained lower BT (40.21±0.05ºC) between 1900 h and 2200 h compared to B. indicus (40.27±0.05ºC) which may be due to disrupted heat loss mechanisms during the day, highlighting the importance of night time cooling. In response to increasing heat load, BT in B. taurus had slower increases but retained heat for longer, whilst B. indicus BT responded by a series of rapid increases and decreases. Developing an understanding of the differences in BT regulation in B. indicus and B. taurus will allow for more effective heat load management strategies during heat waves to be established.

Genome association of carcass and palatability traits from Bos indicus-Bos taurus crossbred steers within electrical stimulation status and correspondence with steer temperament 1. Carcass

Genome-wide association analyses were conducted using SNP and carcass traits, with and without electrical stimulation separately, of 350 Bos indicus-Bos taurus steers from a designed mapping population consisting of full-sibling families (embryo transfer) and half-sibling families. Four F1 Nellore–Angus sires had progeny in both types of families. Relationships of carcass traits with multiple assessments of temperament (correlation coefficients of unadjusted or residual values), including aggressiveness (willingness to hit an evaluator), nervousness, flightiness (nervousness with running or other movement), gregariousness (willingness to separate from other steers), and overall temperament (all temperament traits assigned as 1 to 9 values; higher numbers indicate worse or less desirable temperament) at 1 year of age and with overall temperament evaluated immediately prior to slaughter were low (0 < |r| < 0.18). Significant SNP associations were detected (False Discovery Rate controlled at 0.05) on BTA 1 with skeletal maturity (n = 1), and BTA 14 (n = 2) with carcass weight. Candidate genes were (skeletal maturity) phospholipase C like 2 (PLCL2) and (carcass weight) neutral sphingomyelinase activation associated factor (NSMAF) and thymocyte selection associated high mobility group box (TOX). Two SNP with association with marbling score were identified on BTA 12—dachshund family transcription factor 1 (DACH1) was a candidate gene. A region from 24.25 to 38.54 Mb on BTA 23 contained 6 SNP with significant associations with lean or overall maturity, which may be the first reported for these traits. Candidate genes on that chromosome included fibrocystin/polyductin (PKHD1), glial cells missing homolog 1 (GCM1), prolactin (PRL), and ring finger protein 144B (RNF144B). All detections of association were in traits measured on the side with no electrical stimulation; it may be that electrical stimulation removes some of the variation permitting detection of association.

Short communication: pharmacokinetics of oxytocin administered intranasally to beef cattle

Providing the neuropeptides oxytocin and vasopressin intranasally increased concentrations in plasma and cerebral spinal fluid in humans and primates, respectively. This is of interest because of the documented anxiolytic effects of oxytocin observed in humans and rodents. To date, a transnasal approach of hormone administration has not been investigated in beef cattle. Defining the pharmacokinetics of intranasal oxytocin in cattle is necessary for determining optimum sampling and dosing timelines for future investigations. Five, weaned Bos taurus steers were used in a 3 × 3 Latin square design. Treatments included 1) 0.33 IU oxytocin/kg BW (A, n = 5), 2) 0.66 IU oxytocin/kg BW (B, n = 5), and 3) 1.32 IU oxytocin/kg BW (C, n = 5). Steers were acclimated to handling and restraint procedures for 4 wk leading up to the start of the experiment. Frequent blood collection occurred every 2 min for the first 30 min and every 5 min for the second 30 min, relative to administration of intranasal treatment. No treatment by time interaction was detected; however, there was an effect of time (P < 0.001) and treatment (P = 0.002) on oxytocin concentrations over time. Pharmacokinetic parameters, determined by PKSolver excel add-in, demonstrated an average maximum concentration (CMAX) of 63.3 pg/mL at 3.5 min after intranasal dose administration. An average half-life (T1/2) of 12.1 min after intranasal administration was determined. Pharmacokinetic parameters to a single bolus were not dose-dependent.

Antibody titers to vaccination are not predictive of level of protection against a BVDV type 1b challenge in Bos indicus - Bos taurus steers

Subclinical illness associated with infection is thought to reduce performance and increase production costs in feedlot cattle, but underlying components remain largely unidentified. Vaccination is frequently used in feedlot settings but producers lack metrics that evaluate the effectiveness of vaccination programs. The goal of this study was to determine if levels of serum neutralizing antibody titers were predictive of levels of vaccine protection in a commercial setting. During this four-year study, Angus-Nellore steers housed in a production feedlot setting were assigned to 1 of 3 vaccine treatments: killed vaccine (kV), modified live virus (MLV) vaccine, or no vaccine (control), and were challenged with a noncytopathic 1b field strain of bovine viral diarrhea virus. Rectal temperature and levels of circulating lymphocytes and platelets were monitored following challenge. While no animals were diagnosed as clinically ill with respiratory disease, indicators of disease (pyrexia, lymphopenia, and thrombocytopenia) were observed. The MLV treatment elicited higher antibody titers to the vaccination than the kV, and calves in the MLV treatment had higher mean titers at challenge. The year that elicited the highest antibody response to the vaccination and the year with the lowest frequency of phenotypic responses to the challenge were not concurrent. The MLV treatment had the highest proportion, 34.68%, of animals that were protected against the challenge regardless of the pre-challenge antibody titer and had the fewest number of lymphopenia cases in response to the challenge. Both vaccine treatments mitigated thrombocytopenia when compared to the control treatment, and the MLV treatment reduced lymphopenia; however, these symptoms were not completely eliminated in vaccinated animals. Pyrexia was present in 40.11% of the animals, but no difference in the frequency of cases between treatments was observed. Pre-challenge vaccination response was not indicative of the level of protection nor was anamnestic antibody response correlated with health status.

003 Genome wide association of beef flavor and tenderness in steaks (with electrical stimulation and without) from carcasses of Nellore-Bos taurus steers

003 Genome wide association of beef flavor and tenderness in steaks (with electrical stimulation and without) from carcasses of Nellore-Bos taurus steers

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on tenderness of Longissimus steaks of Bos taurus steers

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on tenderness of Longissimus steaks of Bos taurus steers

Computed tomographic evaluation to determine efficacy of euthanasia of yearling feedlot cattle by use of various firearm-ammunition combinations

To evaluate with CT the efficacy of various combinations of firearms and ammunitions to penetrate and disrupt the brain tissue of cadaveric heads of feedlot steers. 42 fresh cadaveric heads of 12- to 18-month-old Bos taurus steers. For each of 7 combinations of firearms and ammunitions (.22-caliber rifle firing a long rifle 30-grain plated lead solid- or hollow-point round, .223-caliber carbine firing a 50-grain ballistic-tip round, 9-mm pistol firing a 124-grain total metal jacket round, .45-caliber automatic Colt pistol [ACP] firing a 230-grain full metal jacket round, and 12-gauge shotgun firing a 2.75-inch 1.25-ounce No. 4 birdshot shell or a 1-ounce rifled slug), 6 cadaveric heads were shot at an identical distance (3 m), angle, and anatomic location. Heads were scanned with third-generation CT, and images were evaluated to determine extent of penetration, projectile fragmentation, cranial fracture, and likelihood of instantaneous death (≥ 30% destruction of brain tissue or a brainstem lesion). RESULTS-41 of 42 skulls were penetrated by the projectile. Instantaneous death was considered a likely consequence for 83% (25/30) of heads shot with a rifle-fired .22-caliber solid-point round, pistol-fired .45-caliber ACP round, carbine-fired .223-caliber round, and shotgun-fired birdshot and slug. Of the 18 heads shot with pistol-fired 9-mm and .45-caliber ACP rounds and rifle-fired .22-caliber hollow-point rounds, only 6 had brainstem lesions. CONCLUSIONS AND CLINICAL RELEVANCE-Results suggested that gunshots delivered by all firearm-ammunition combinations except rifle-fired .22-caliber hollow-point rounds and pistol-fired 9-mm rounds were viable options for euthanasia of feedlot cattle.

Effects of backgrounding and finishing growth rates on P8 fat and intramuscular fat in Bos taurus steers

The present study investigates the effects of backgrounding and finishing growth rates of Bos taurus steers grown out on three post-weaning growth pathways, across 4 years (1995–1998) on fat deposition. Scanned P8 fat at backgrounding exit (SP8exit), scanned P8 fat before slaughter (SP8sla) and carcass intramuscular fat (IMF, %) were evaluated. Four equations to predict SP8sla and four equations to predict carcass IMF across years were developed. Three post-weaning growth pathways (GPs) generated by different nutritional treatments across years were used in the study. Growth pathways were created by backgrounding steers on pasture with no supplementation (GP1), pasture plus supplementary feeding formulated pellets (GP2) or pasture with access to a forage crop (GP3). The steers were then finished in a feedlot or on pasture to slaughter weights of 520 kg (Korean market specification) or 600 kg (Japanese market specification). Cubic smoothing splines were fitted to the liveweight of all animals from the start of backgrounding until slaughter. Backgrounding growth rates were interpolated off the GP curves and the mean average daily gain (ADG, kg/day) at Day 100 (D100, Days 100–91 before relocation to the finishing phase), and Day 150 (D150, Days 150–141 before relocation to the finishing phase) were calculated. Significant (P &lt; 0.01) differences between SP8exit and backgrounding ADG (BADG) were detected in all years except GP2 v. GP3 in 1997. GP1 steers had the lowest BADG across all years, ranging from 0.39 to 0.88 kg/day. At backgrounding exit, the mean SP8exit for the different GPs was ranked, with GP1 &lt; GP3 for all years, with significant (P &lt; 0.01) differences among GP1, GP2 and GP3 in all years except 1996. At the end of finishing, the mean carcass IMF over all years and finish (pasture and feedlot) (P &lt; 0.05) was 4.71% for GP1 v. 5.09% for GP3 for Korean market steers and the mean SP8sla (P &lt; 0.01) was 14.59 mm for GP1 v. 16.04 mm for GP3 and the mean carcass IMF (P &lt; 0.01) was 5.54% for GP1 v. 6.27% for GP3 for Japanese market steers. The residual correlation of the multivariate response variables, namely, D100, D150 and BADG v. SP8exit (n = 1054), SP8sla (n = 1049) and carcass IMF (n = 1002), indicated that the highest correlations, all significant (P &lt; 0.01), were 0.33, 0.20 and 0.12 for BADG v. SP8exit, SP8sla and carcass IMF, respectively. The residual variances (mm2) of the four SP8sla equations were 6.14, 7.44, 8.72 and 10.73 for 1995, 1996, 1997 and 1998, respectively, and the residual variances (%2) for the four carcass IMF equations were 2.51, 2.26, 1.75 and 0.84, for 1995, 1996, 1997 and 1998, respectively.

Comparison of steer behavior when housed in a deep-bedded hoop barn versus an open feedlot with shelter1

The use of hoop barns as an alternative housing system for beef cattle has not been widely researched. The objectives of this study were to determine the main effects of behavior of steers 1) over winter and summer, 2) when housed in either a hoop barn or a conventional feedlot, and 3) interactions between season and housing system. A total of 960 crossbred Bos taurus steers were used [August 2006 to April 2008 (2 winter and 2 summer trials)]. Steers were housed in either 1 deep-bedded hoop barn (n = 12 pens; 4.65 m(2)/steer) or 1 open feedlot with shelter (n = 12 pens; 14.7 m(2)/steer). Steers were ear tagged, implanted, and weighed (414 ± 36 kg) on arrival and allotted to treatments that were balanced for source, BW, and hide color. Behavioral data (3 postures and 2 behaviors) were collected using a 10-min live scan. The experimental unit for behavior was a pen of steers. Behavioral data were arcsine transformed to achieve a normal distribution. There were no (P > 0.05) differences for time spent at bunk or waterer for steers between housing treatments. Steers housed in an open feedlot with shelter spent less time lying and more time standing and walking (P < 0.05) compared with steers housed in a hoop barn. There were no (P = 0.32) differences between seasons for standing. Steers spent more time at the bunk (P < 0.0001) and waterer (P < 0.0001) in the summer compared with the winter. In the winter, steers engaged in more lying (P = 0.0002) and walking (P < 0.0001). Overall, steers stood less (P = 0.006) and spent more time lying (P = 0.024) when housed in a hoop barn than in the open feedlot with shelter regardless of season. Steers housed in the open feedlot with shelter walked more (P < 0.0001) than steers housed in the hoop barn and walked more (P < 0.0001) in winter than in summer months (6 vs. 3%). There were no (P > 0.05) differences in time spent at bunk and waterer between housing systems within season, but time spent at the waterer and bunk decreased (P < 0.05) for both housing systems during the winter. In conclusion, housing 40 steers per pen in a cornstalk-bedded hoop barn at 4.65 m(2)/steer does not result in adverse behavioral alterations and can be considered as a housing alternative for finishing steers in the Midwestern United States when compared with steers fed in an open feedlot with shelter provided.

Relationships of behavioral and physiological symptoms of preslaughter stress to beef longissimus muscle tenderness1

Relationships between behavioral and physiological symptoms of preslaughter stress and LM Warner-Bratzler shear force (WBSF) were investigated using Bos taurus steers (n = 79) and heifers (n = 77). Measurements of heart rate, respiration rate, rectal temperature, and concentrations of serum cortisol and plasma epinephrine were used as indicators of stress associated with physical handling and chute restraint, whereas concentrations of cortisol, glucose, lactate, and creatine kinase in blood samples obtained at exsanguination were measured to reflect physiological reactions of animals to transportation stress. Increased plasma epinephrine concentration, indicative of acute handling stress, was associated with elevated heart rate (r = 0.42, P < 0.001) and rectal temperature (r = 0.34, P < 0.001) during restraint, increased plasma lactate (r = 0.22, P = 0.006) and serum creatine kinase (r = 0.28, P < 0.001) concentrations at slaughter, and greater LM WBSF (r = 0.22, P = 0.006). Plasma lactate concentration at slaughter, which reflected an adrenergic stress response to transportation, was associated with lesser final LM pH (r = -0.30, P < 0.001) and greater LM WBSF (r = 0.26, P = 0.002). Categorical analyses of chute and posttransportation behavior scores (calm vs. restless vs. nervous) showed that cattle exhibiting adverse behavioral reactions to handling and chute restraint had increased (P < 0.05) values for plasma epinephrine concentration, heart rate, and rectal temperature during chute restraint, elevated (P < 0.05) plasma lactate concentration at slaughter, and increased (P < 0.05) LM WBSF. In addition, cattle showing behavioral symptoms of stress after transportation had greater (P < 0.05) plasma glucose and lactate concentrations at slaughter and produced LM steaks that were 0.34 kg tougher (P < 0.05) when compared with calm cattle. No carcasses were identified as dark cutters, and LM pH did not differ (P > 0.05) among behavior categories. Grouping cattle according to differences in plasma lactate concentration categorized them according to mean differences in LM WBSF. Moreover, steaks from cattle with the greatest plasma lactate concentrations at slaughter (91st to 100th percentile) had a delayed response to aging that persisted until 14 d postmortem. Stress-induced differences in LM tenderness observed in this study were independent of differences in muscle pH.

A new heat load index for feedlot cattle1

The ability to predict the effects of extreme climatic variables on livestock is important in terms of welfare and performance. An index combining temperature and humidity (THI) has been used for more than 4 decades to assess heat stress in cattle. However, the THI does not include important climatic variables such as solar load and wind speed (WS, m/s). Likewise, it does not include management factors (the effect of shade) or animal factors (genotype differences). Over 8 summers, a total of 11,669 Bos taurus steers, 2,344 B. taurus crossbred steers, 2,142 B. taurus x Bos indicus steers, and 1,595 B. indicus steers were used to develop and test a heat load index (HLI) for feedlot cattle. A new HLI incorporating black globe (BG) temperature ( degrees C), relative humidity (RH, decimal form), and WS was initially developed by using the panting score (PS) of 2,490 Angus steers. The HLI consists of 2 parts based on a BG temperature threshold of 25 degrees C: HLI(BG>25) = 8.62 + (0.38 x RH) + (1.55 x BG) - (0.5 x WS) + e((2.4-WS)), and HLI(BG<25) = 10.66 + (0.28 x RH) + (1.3 x BG) - WS, where e is the base of the natural logarithm. A threshold HLI above which cattle of different genotypes gain body heat was developed for 7 genotypes. The threshold for unshaded black B. taurus steers was 86, and for unshaded B. indicus (100%) the threshold was 96. Threshold adjustments were developed for factors such as coat color, health status, access to shade, drinking water temperature, and manure management. Upward and downward adjustments are possible; upward adjustments occur when cattle have access to shade (+3 to +7) and downward adjustments occur when cattle are showing clinical signs of disease (-5). A related measure, the accumulated heat load (AHL) model, also was developed after the development of the HLI. The AHL is a measure of the animal's heat load balance and is determined by the duration of exposure above the threshold HLI. The THI and THI-hours (hours above a THI threshold) were compared with the HLI and AHL. The relationships between tympanic temperature and the average HLI and THI for the previous 24 h were R(2) = 0.67, P < 0.001, and R(2) = 0.26, P < 0.001, respectively. The R(2) for the relationships between HLI or AHL and PS were positive (0.93 and 0.92 for HLI and AHL, respectively, P < 0.001). The R(2) for the relationship between THI and PS was 0.61 (P < 0.001), and for THI-hours was 0.37 (P < 0.001). The HLI and the AHL were successful in predicting PS responses of different cattle genotypes during periods of high heat load.