Effect of wheat middling incorporation into wet corn distillers grains with solubles on apparent diet digestibility and ruminal fermentation characteristics in growing and finishing diets.

Two separate cross-over experiments were conducted to evaluate the effects of incorporating wheat middlings into wet corn distillers grains with solubles (WDGS) on apparent diet digestibility and ruminal fermentation characteristics in growing and finishing diets. In experiment 1, four ruminally cannulated heifers (313 ±â€…42.9 kg) were limit fed a high-energy growing diet that included WDGS (CON) or WDGS + wheat middlings (CON + WM) at 40% of diet dry matter (DM). The diet also contained (DM basis) 39.5% dry-rolled corn, 7.5% supplement, and 13% warm-season grass hay. In experiment 2, four ruminally cannulated Holstein steers (321 ±â€…17.4 kg) were fed a finishing diet that included WDGS (CON) or WDGS + wheat middlings (CON + WM) at 30% of diet DM. The diet also contained (DM basis) 60.3% dry-rolled corn, 2.7% supplement, and 7.0% warm-season grass hay. Experiments consisted of two 15-d periods that were conducted concurrently. Each period included 10 d of diet adaptation, 4 d of fecal collection, and 1 d of ruminal fluid collection. Fecal samples were collected on days 11 to 14 of each period and composite samples were analyzed for chromium to estimate apparent diet digestibility. On day 15, ruminal fluid samples were collected prior to feeding and again at 2, 4, 6, 8, 12, 18, and 24-h post-feeding. In experiment 1, DM, organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) intake did not differ (P ≥ 0.11) between diets; however, starch intake was greater (P = 0.03) for heifers fed CON + WM compared with CON. Apparent DM, OM, NDF, and starch digestibilities were similar between diets (P ≥ 0.13), but feeding CON + WM tended to lead to lesser (P = 0.06) apparent ADF digestibility. Ruminal pH and total volatile fatty acid concentrations did not differ between diets (P ≥ 0.16); however, ruminal ammonia concentrations tended to be less (P = 0.09) for CON + WM compared with CON. In experiment 2, DM intake did not differ (P = 0.65) between diets. Apparent DM digestibility was greater (P = 0.01) for CON + WM compared with CON but the difference was small. Intake and apparent digestibility of OM, NDF, ADF, and starch did not differ (P ≥ 0.25) between diets. Ruminal ammonia concentrations were lesser (P = 0.03) while ruminal pH was greater (P = 0.02) for CON + WM compared with CON. Overall, incorporation of wheat middlings into WDGS had minimal impacts on feed intake, apparent diet digestibility, and ruminal fermentation characteristics when fed to growing and finishing cattle.

Pregnancy risk in beef and dairy cows after supplementing semen with transforming growth factor beta-1 at the time of artificial insemination.

Our objective was to determine if the addition of a concentrated human recombinant transforming growth factor beta-1 (TGF) to bovine semen at the time of AI would result in increased risk of pregnancy in beef and dairy cows. Suckled beef cows (n = 1,132) in 11 herds across 2 states and lactating dairy cows (n = 2,208) in one organic-certified herd were enrolled. Beef cows received fixed-time AI (FTAI) following a 7 d CO-Synch + controlled internal drug release estrous synchronization protocol. Dairy cows were inseminated following observation of natural estrus expression. Cows received either no treatment as a control (CON) or 10 ng of TGF in 10 µL added through the cut-end of a thawed straw of semen immediately prior to AI. At the time of FTAI of beef cows, the mean ±â€…SD age was 5.0 ±â€…2.4 yr, BCS was 5.3 ±â€…0.7, and days postpartum was 78.2 ±â€…15.5 d. The overall pregnancy risk (PR) in beef cows was 55.2% to AI and 90.5% season-long. PR in beef cows was not affected (P = 0.27) by the addition of TGF (53.1% vs. 58.1%). Furthermore, there was no difference (P = 0.88) for season-long PR in beef cows that received TGF (91.2% vs. 91.5%). At the time of insemination of dairy cows, the mean ±â€…SD lactation was 3.0 ±â€…1.3 lactations, BCS was 2.9 ±â€…0.3, days in milk was 115.6 ±â€…56.6 d, and cows had received 2.4 ±â€…1.5 inseminations/cow. The overall pregnancy risk to AI in dairy cows was 23.1%. PR to AI for dairy cows was not affected (P = 0.32) by addition of TGF (22.0% vs. 23.8%). In conclusion, PR to AI was not affected by addition of TGF to thawed semen immediately prior to AI in beef or dairy cows.

Seminal plasma is the fluid portion of the ejaculate that is routinely removed or significantly diluted when preparing semen for artificial insemination. Seminal plasma has been shown to elicit changes to the tissues of the uterus at the time of insemination that improves pregnancy outcomes in rodents and swine. Here, we supplemented the molecule of seminal plasma, transforming growth factor beta-1, to semen at the time of artificial insemination in an attempt to improve pregnancy rates in beef and dairy cattle. In total, 3,340 cows were inseminated; half received no treatment, and the other half received a supplementation of transforming growth factor beta-1. We found that supplementing transforming growth factor beta-1 did not improve the pregnancy rate in beef or dairy cattle. We conclude that the pregnancy rate was not affected by the supplementation of transforming growth factor beta-1 to semen at the time of insemination. Future studies should consider the effects of transforming growth factor beta-1 on other pregnancy outcomes, such as calving rate, birth weight, and postnatal growth.

Almond hulls and shells as an alternative fiber source in limit-fed growing beef cattle diets.

Almond hulls and shells are a by-product of almond production that can be incorporated as a feed ingredient in beef cattle diets. Three experiments were conducted to determine the effects of hammermill screen size on almond hull and shell bulk density and inclusion of ground or non-ground almond hulls and shells in limit-fed growing diets on growth performance, diet digestibility, and ruminal fermentation characteristics of beef cattle. In experiment 1, almond hulls and shells were ground with a laboratory-scale hammermill using no screen, a 11.1-mm screen, a 19.1-mm screen, or a 25.4-mm screen. Each screen-size treatment was ground at three separate time points (n= 3 replications/treatment). Grinding almond hulls and shells with no screen increased bulk density by 111% and minimized proportions of fine particles; therefore, almond hulls and shells ground using no screen were included as a treatment in the following experiments. In experiment 2, 364 steers (initial body weight [BW]: 257±â€…20.7 kg) were blocked by truckload (n = 4), stratified by BW, and assigned to pen within block. Pens were randomly assigned to 1 of 4 experimental diets (n= 10 pens/treatment). The control diet (CON) contained (DM basis) 39.5% dry-rolled corn, 7.5% supplement, 40% wet-corn gluten feed, and 13% prairie hay. Non-ground (13AH) or ground (13GAH) almond hulls and shells replaced prairie hay and were fed at 13% of diet DM or non-ground almond hulls and shells were fed at 26% of diet DM and replaced 13% prairie hay and 13% dry-rolled corn (26AH). Diets were limit-fed at 2.2% of BW daily (DM basis) for 56 d. Overall average daily gains (ADG) were greater (P ≤ 0.05) for CON, 13AH, and 13GAH compared with 26AH. In addition, ADG from days 14 to 56 were greater (P= 0.03) for 13GAH and tended to be greater (P = 0.09) for 13AH compared with CON. Experiment 3 was a 4 × 4 replicated Latin square in which 8 ruminally cannulated heifers (initial BW = 378 ±â€…44.0 kg) were fed diets from experiment 2. Apparent dry matter digestibility did not differ (P = 0.21) among treatments. Total ruminal volatile fatty acid concentrations were greater (P ≤ 0.03) for 13GAH and 13AH compared with 26AH and tended (P = 0.06) to be greater for 13GAH compared with CON. Overall, almond hulls and shells can be utilized as an alternative to prairie hay in limit-fed growing diets without negatively influencing rates of gain or diet digestibility.

Effects of high-sulphur water on hepatic gene expression of steers fed fibre-based diets.

Sulphur-induced polioencephalomalacia (sPEM), a neurological disorder affecting ruminants, is frequently associated with the consumption of high-sulphur (S) water and subsequent poor performance. Currently, there is no economical method for S removal from surface water sources, and alternative water sources are typically neither readily available nor cost-effective. Determination of genes differentially expressed in response to high-S water consumption may provide a better understanding of the physiology corresponding to high dietary S and ultimately lead to the development of treatment and prevention strategies. The objective of this study was to determine changes in gene expression in the liver, an organ important for S metabolism, of fibre-fed steers consuming high-S water. For this study, liver tissues were collected on the final day of a trial from yearling steers randomly assigned to low-S water control (566 mg/kg SO4 ; n = 24), high-S water (3651 mg/kg SO4 ; n = 24) or high-S water plus clinoptilolite supplemented at either 2.5% (n = 24) or 5.0% (n = 24) of diet dry matter (DM). Microarray analyses on randomly selected healthy low-S control (n = 4) and high-S (n = 4; no clinoptilolite) steers using the Affymetrix GeneChip Bovine Genome Array revealed 488 genes upregulated (p < 0.05) and 154 genes downregulated (p < 0.05) in response to the high- vs. low-S water consumption. Real-time RT-PCR confirmed the upregulation (p < 0.10) of seven genes involved in inflammatory response and immune functions. Changes in such genes suggest that ruminant animals administered high-S water may be undergoing an inflammation or immune response, even if signs of sPEM or compromised health are not readily observed. Further study of these, and other affected genes, may deliver new insights into the physiology underlying the response to high dietary S, ultimately leading to the development of treatments for high S-affected ruminant livestock.

Effects of late-season sheep grazing following early-season steer grazing on population dynamics of sericea lespedeza in the Kansas Flint Hills.

Mature ewes were used in a 4-yr study to evaluate effects of intensive late-season sheep grazing on vigor of sericea lespedeza in native tallgrass prairie. Pastures (N = 8; 31 ± 3.6 ha) infested with sericea lespedeza (initial basal frequency = 1.4%) were assigned randomly to one of two treatments: early-season beef steer grazing (1.1 ha/steer; initial BW = 258 ± 34 kg) from April 15 to July 15 followed by no grazing for the rest of the year (control; STR) or steer grazing from April 15 to July 15 followed by intensive grazing by mature ewes (0.2 ha/ewe; SHP) from August 1 to October 1. Ewes (initial BW = 65 ± 3.1 kg) were assigned randomly to graze four of eight pastures; remaining pastures were not grazed from August 1 to October 1. Vegetation responses to treatment were measured along four permanent 100-m transects in each pasture. Herbivory on sericea lespedeza was monitored weekly in each pasture from July 21 to October 7. Herbivory on sericea lespedeza in SHP and STR after steer grazing and before sheep grazing was not different (P = 0.51). In contrast, sericea lespedeza herbivory following sheep grazing was greater (P < 0.01) in SHP than in STR. Herbivory of individual sericea plants was greater (P < 0.01) in SHP than in STR by the end of week 1 of the sheep-grazing period (10.6% vs. 0.5%); moreover, herbivory on sericea lespedeza steadily increased (P ≤ 0.01) such that 92.1% of sericea lespedeza plants were grazed in SHP compared to 1.4% in STR by week 8 of the sheep-grazing period. Whole-plant DM weight of sericea lespedeza at dormancy was less (P < 0.01) in SHP than in STR. Additionally, annual seed production by sericea lespedeza was less (P < 0.01) in SHP than in STR (114 vs. 864 seeds/plant). Pasture forage biomass was not different (P = 0.76) between SHP and STR after the steer-grazing period. Conversely, STR had more (P < 0.01) residual forage biomass than SHP at the end of the sheep-grazing period. Growth performance of beef steers grazing from April 15 to July 15 annually was not different (P ≥ 0.59) between treatments. Our results were interpreted to suggest that intensive late-season grazing by sheep decreased vigor of sericea lespedeza. Late-season sheep grazing decreased forage biomass by 904 kg DM/ha compared with late-season rest; however, residual biomass was adequate to prevent soil-moisture loss and erosion during the dormant season.

A 6-yr evaluation of prescribed-fire timing on yearling cattle growth performance and plant community dynamics on native tallgrass prairie in the Kansas Flint Hills.

A 6-yr experiment was conducted to determine the effects of prescribed-fire season on stocker cattle growth performance and rangeland plant community characteristics in the Kansas Flint Hills. Eighteen pastures were grouped by watershed and each watershed was randomly assigned to 1 of 3 prescribed-fire treatments: spring (11 April ±â€…5.7 d), summer (25 August ±â€…6.2 d), or autumn (2 October ±â€…9.0 d). All burns were applied prior to grazing in years 1, 2, 3, and 5; however, no burns were applied in year 4 because of unfavorable burn conditions. Over 5 consecutive grazing seasons, 1,939 yearling stocker calves (initial BW = 281 ±â€…58.9 kg) were grazed from May to August at a targeted stocking density of 280 kg live-weight + ha-1. Beginning in June of 2018 (pretreatment), a permanent 100-m transect was established in each pasture and was used to determine plant-species composition using a modified step-point method. Forage biomass accumulation and root carbohydrate concentrations of 4 native tallgrass plant species were also measured. All data were analyzed as a completely randomized design using a mixed model. Average daily gain (ADG) was 0.05 to 0.07 kg greater (P = 0.02) for calves grazing spring-burned pastures compared with calves grazing summer- or autumn-burned pastures; however, ADG did not differ (P ≥ 0.55) between calves assigned to the summer or autumn prescribed-fire treatments. Basal cover of all graminoids and all forbs did not differ (P ≥ 0.30) among prescribed-fire treatments; however, basal cover of C3 grasses tended (P = 0.06) to be greater while basal cover of C4 grasses tended (P = 0.08) to be less in autumn-burned pastures compared with spring-burned pastures. Forage biomass accumulation did not differ (P = 0.58) among treatments. In addition, root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) did not differ (P ≥ 0.26) among prescribed-fire treatments. Overall, we interpreted these data to suggest that prescribed-fire timing had small influences on yearling stocker cattle growth performance and rangeland plant composition but did not influence forage biomass accumulation or root carbohydrate concentrations of key native tallgrass plant species in the Kansas Flint Hills.

Effects of early or conventional weaning on beef cow and calf performance in pasture or drylot environments.

Performance of cows and calves during 63-d early or conventional weaning periods was evaluated. Spring-calving beef cows (n = 167) of similar age, body condition score (BCS), and body weight (BW = 599 ± 54.5 kg), and their calves (initial BW = 204 ± 26.7 kg; 153 ± 15 d of age) were assigned randomly to 1 of 4 weaning treatments: weaning at 153 d of age followed by 56 days of limit feeding in confinement (E-D), confinement of cow and calf for a 56-d period of limit feeding followed by weaning at 209 d of age (C-D), weaning at 153 d of age followed by a 56-d grazing period (E-P), and a 56-d grazing period for both cow and calf followed by weaning at 209 d of age (C-P). Cows and calves assigned to pasture treatments grazed native range pastures without supplement. Cows and calves assigned to drylot treatments were fed complete diets. Calves assigned to E-D were fed a concentrate-based diet at 2.5% of BW, whereas cows assigned to E-D were fed a forage-based diet at 1.6% of BW. Cows assigned to C-D were offered the diet fed to E-D cows at 2.0% of BW. Calf average daily gain (ADG) was influenced by diet and weaning treatments (diet × weaning, P ≤ 0.03). Cows and calves assigned to all treatments were limit fed common diets for 7 d at the end of our study to equalize gut fill. In general, calves managed in confinement and fed concentrate-based diets (i.e., E-D and C-D) had greater ADG than non-supplemented calves maintained on pasture (i.e., E-P and C-P). Cow BW and BCS change (days 0 to 63) were influenced by both diet and weaning status (P ≤ 0.05). Non-lactating cows maintained on pasture had lesser BW loss than other treatments, whereas non-lactating cows fed in confinement had lesser BCS on day 63 and greater BCS loss from days 0 to 63 than other treatments. Conversely, rump-fat depth on day 63 was greater (P < 0.01) for non-lactating cows maintained on pasture than for lactating cows in either pasture or drylot environments. Similarly, change in rump-fat depth was greatest (diet × weaning, P < 0.01) for non-lactating cows on pasture and least for lactating cows in either pasture or drylot environments. Results were interpreted to indicate that early-weaning spared cow BW and rump fat compared to weaning at conventional ages. Performance of cows appeared to be similar when limit-fed under drylot conditions or maintained in a pasture environment. Conversely, calf performance was generally greater in confinement than on pasture.

Effects of weaning method on postweaning performance by early weaned beef calves.

Health and performance of early-weaned steers were evaluated during a 56-d weaning period, a 56-d feedlot receiving period, and a 165-d feedlot finishing period. Steers (n = 239; 128 ± 14 d of age) were assigned to a 56-d weaning treatment: drylot weaning (D) or pasture weaning (P). Pasture steers grazed mature, native tallgrass range (89.2% dry matter [DM], 9.08% crude protein [CP]), without supplementation. A concentrate-based diet (18.7% CP and 1.15 Mcal NEg/kg) was fed to D steers. Later, all steers were transitioned to a receiving, then a finishing diet and fed to a common endpoint. Body weight (BW) after and average daily gain (ADG) during weaning were greater (P < 0.01) for D than for P. Incidence of undifferentiated fever during weaning tended to be greater (P = 0.10) for D steers than for P steers. Conversely, incidence of keratoconjunctivitis was greater (P < 0.01) for P than for D during weaning (40.2% vs. 0%, respectively) and receiving (P < 0.01; 14.3% vs. 1.6%, respectively). At the start and end of receiving, D steers had greater (P < 0.01) BW compared with P steers. Drylot steers had greater (P = 0.03) ADG compared with P steers during receiving. Pasture steers tended to have greater dry matter intake (DMI) (P = 0.09) during receiving than D steers. In contrast, gain:feed (G:F) was improved (P < 0.01) for P steers than for D steers during receiving. Incidence of undifferentiated fever was not different (P = 0.99) between D and P steers during receiving. At start of finishing, D steers were heavier (P < 0.01) than P steers; however, finishing ADG was greater (P < 0.01) for P compared with D. Conversely, hot carcass weight of P steers was less (P < 0.01) compared with D steers. Drylot steers had greater DMI (P < 0.01) than P steers during finishing, whereas P steers had improved G:F (P < 0.01) compared with D steers. There were no differences (P ≥ 0.19) between treatments in DOF, carcass characteristics or United States Department of Agriculture yield grade. Growth and health during a 56-d weaning period and a 56-d receiving period were improved when steers were weaned in a drylot environment and fed a concentrate-based diet compared with non-supplemented steers weaned in a pasture environment. We interpret these data to suggest that, under the conditions of our experiment, steers preconditioned on mature, native, warm-season pasture for 56 d without supplementation were unable to compensate for previous nutrient restriction during finishing.

Bunk space requirements for growing beef cattle limit-fed a high-energy corn and corn co-product diet.

Bunk requirements for optimal growth performance of growing calves limit-fed high-energy corn and corn co-product diets have not been widely evaluated. Three-hundred eighty-five crossbred steers (initial body weight = 215 ± 25 kg) were purchased in Texas, transported to the Kansas State Beef Stocker Unit, and weighed at arrival. Steers were stratified by body weight and randomly assigned to 1 of 28 pens containing 12 to 14 head. Within block, pens were randomly assigned to one of four bunk allotment treatments: 25.4, 38.1, 50.8, or 63.5 cm of bunk per head for a 58-d receiving period. Calves were fed at 0700 h once daily at 1.8% of bodyweight (dry matter basis) from February 2 to March 13, 2021; thereafter the daily feed allotment was increased to 2.0% of bodyweight. The diet contained (dry matter basis) 39.5% dry-rolled corn, 7.5% supplement, 40% wet corn gluten feed, and 13% prairie hay. Steers were individually weighed on days 29 and 58 and pen weights were measured weekly to determine feed offered for the following week. Body weights on days 29 and 58, dry matter intake, or gain-to-feed ratio during the receiving period did not differ (P ≥ 0.34) between treatments. During the first 29 d, average daily gain (ADG) increased linearly as bunk space increased (P = 0.03); however, no treatment effects were observed thereafter. In addition, ADG standard deviation from days 0 to 29 responded quadratically (P = 0.05) where ADG standard deviation tended to be greater in the 38.1-cm allotment and was greater in the 50.8-cm allotment compared to the 25.4-cm allotment (P = 0.07 and P = 0.04, respectively). Bunk score tended to decrease linearly as bunk allotment decreased (P = 0.06). Following the receiving period, steers were blocked by bunk treatment and randomly assigned to 1 of 18 pastures. Steers were grazed for 90-d from May to August at a targeted stocking density of 280 kg live-weight ˖ ha-1. During the grazing season, ADG increased linearly with reduced (P < 0.01) bunk allotment; however, body weights did not differ (P = 0.91) between bunk treatments at the completion of the grazing period. In addition, overall total body weight gains and ADG from the receiving and grazing periods did not differ (P > 0.57) between bunk treatments. We interpreted our data to suggest that bunk space allotments of 25.4 to 63.5 cm per head had minimal impact on growth performance during a 58-d receiving period and did not affect final body weights following a 90-d grazing season.

Effects of prescribed fire timing on vigor of the invasive forb sericea lespedeza (Lespedeza cuneata), total forage biomass accumulation, plant-community composition, and native fauna on tallgrass prairie in the Kansas Flint Hills.

The predominant grazing-management practice of the Kansas Flint Hills involves annual prescribed burning in March or April with postfire grazing by yearling beef cattle at a high stocking density from April to August. There has been a dramatic increase in sericea lespedeza (Lespedeza cuneata [Dumont] G. Don) coincident with this temporally focused use of prescribed fire in the Flint Hills region. The species is an aggressive invader and a statewide noxious weed in Kansas. Control has generally been attempted using repeated herbicide applications. This approach has not limited proliferation of sericea lespedeza and resulted in collateral damage to nontarget flora and fauna. Alternative timing of prescribed fire has not been evaluated for its control. Our objectives for this 4-yr experiment were to (1) document the effects of prescribed burning during early April, early August, or early September on vigor of sericea lespedeza, standing forage biomass, and basal cover of native graminoids, forbs, and shrubs and (2) measure responses to fire regimes by grassland bird and butterfly communities. Whole-plant dry mass, basal cover, and seed production of sericea lespedeza were markedly less (P < 0.01) in areas treated with prescribed fire in August or September compared with April. Forage biomass did not differ (P ≥ 0.43) among treatments when measured during July; moreover, frequencies of bare soil, litter, and total basal plant cover were not different (P ≥ 0.29) among treatments. Combined basal covers of C4 grasses, C3 grasses, annual grasses, forbs, and shrubs also did not differ (P ≥ 0.11) between treatments. Densities of grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), and eastern meadowlark (Sturnella magna) were not negatively affected (P > 0.10) by midsummer or late-summer fires relative to early-spring fires. There were no differences (P > 0.10) in densities of grassland-specialist butterfly species across fire regimes. Under the conditions of our experiment, prescribed burning during summer produced no detrimental effects on forage production, desirable nontarget plant species, grassland birds, or butterfly communities but had strong suppressive effects on sericea lespedeza. Additional research is warranted to investigate how to best incorporate late-summer prescribed fire into common grazing-management practices in the Kansas Flint Hills.

Effect of Protracted Free-Choice Chlortetracycline-Medicated Mineral for Anaplasmosis Control on Escherichia coli Chlortetracycline Resistance Profile from Pastured Beef Cattle.

Anaplasmosis is an economically-significant, hemolytic, tick-borne disease of cattle caused by Anaplasma marginale which can cause clinical anemia and death. Current control options are limited, and FDA-approved antimicrobial control options do not have a defined duration of use. A practical and routinely used anaplasmosis control method involves feeding free-choice chlortetracycline (CTC)-medicated mineral to pastured cattle for several months. Constant antimicrobial use poses the risk of expediting the development and dissemination of antimicrobial resistance in off-target commensal bacteria in the bovine gastrointestinal tract. The objective of this study was to determine the CTC-susceptibility of Escherichia coli isolated from anaplasmosis endemic beef cattle herds provided different FDA-approved free-choice CTC-medicated mineral formulations, all intended to provide cattle a dosage of 0.5 to 2.0 mg CTC/lb bodyweight per day. A closed-herd, comprised of Hereford-Angus cows, naturally endemic for anaplasmosis, were grazed in five different pastures with one herd serving as an untreated control group. The other cattle herds were randomly assigned one of four FDA-approved CTC-medicated mineral formulations (700, 5000, 6000, and 8000 g CTC/ton) labeled for "the control of active anaplasmosis" and provided their respective CTC-medicated mineral formulation for five consecutive months. Fecal samples were collected monthly from a subset of cows (n = 6 or 10) per pasture. Fecal samples were cultured for E. coli isolates and the minimal inhibitory concentration of CTC was determined. Baseline CTC-susceptibility of E. coli was variable among all treatment and control groups. The susceptibility of E. coli isolates was significantly different between study herds over the treatment period (p = 0.0037 across time and 0.009 at the final sampling time). The interaction between study herds and treatment period was not significant (p = 0.075).

Effects of prescribed fire timing on grazing performance of yearling beef cattle, forage biomass accumulation, and plant community characteristics on native tallgrass prairie in the Kansas Flint Hills.

Recent research demonstrated that mid- or late-summer prescribed fires can be employed to manage sericea lespedeza (Lespedeza cuneata) infestations in the Kansas Flint Hills. The effects of prescribed fire applied during the growing season (i.e., August to October) on grazing performance of yearling cattle have not been evaluated. Native pastures (n = 18; 22 ± 4.0 ha) were grouped by watershed and assigned randomly to one of three prescribed-fire treatments: spring (7 April ± 2.1 d), summer (21 August ± 5.7 d), or autumn (2 October ± 9.9 d). Yearling beef cattle were grazed from May to August at a targeted stocking density of 280 kg live-weight/ha following prescribed-fire application. Forage biomass accumulations, soil cover, plant species composition, and root carbohydrate concentrations in four native plant species were evaluated. Total body weight (BW) gains and average daily gain were greater (P = 0.01) for cattle that grazed the spring and summer prescribed-fire treatments compared with those that grazed the autumn prescribed-fire treatment. As a result, final BW were greater (P = 0.04) in the spring and summer treatments than the autumn treatment. Conversely, forage biomass accumulations did not differ (P = 0.91) between fire regimes. Proportions of bare soil were greater (P < 0.01) in the spring treatment compared with the summer and autumn treatments, whereas proportions of litter on the soil surface were greater (P < 0.01) in summer- and autumn-burned pastures compared with spring-burned pastures. Total basal cover of graminoids and forbs did not differ (P ≤ 0.15) between prescribed fire treatments. Likewise, total basal cover of C3 or C4 perennial grasses did not differ (P ≥ 0.23) between prescribed-fire treatments. No treatment differences (P = 0.24) in root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) were detected. These data were interpreted to suggest that summer or autumn prescribed fire can be applied without reducing forage biomass accumulations, root carbohydrate concentrations in key native plant species, or considerably altering native plant populations compared with conventional spring-season prescribed fire; however, summer prescribed fire could be favored over spring or autumn prescribed fire both to maintain stocker cattle growth performance and to achieve control over sericea lespedeza.

Plasma pharmacokinetics of oral chlortetracycline in group fed, ruminating, Holstein steers in a feedlot setting.

Chlortetracycline HCl (CTC) has impacted profitable livestock production since 1945. However, pharmacokinetic parameters for CTC in ruminating cattle are unavailable in peer-reviewed literature. A total of 18 steers were randomized to 4.4, 11, or 22 mg/kg/day p.o. CTC treatment groups (n = 6). Chlortetracycline treatment was offered as one-half of the daily dose b.i.d. (160 total doses/group) for 80 days. Blood samples were collected at selected time points throughout an 83-day study and analyzed with a solid phase extraction technique and novel ultrahigh performance liquid chromatography-mass spectroscopy/mass spectroscopy analytical method. Noncompartmental analysis (NCA) determined individual pharmacokinetic parameters by treatment group with coefficient of variation (CV %) estimates. A one-compartment open model with first order absorption and elimination, where absorption rate constant was equal to elimination rate constant, was fitted using nonlinear mixed effects modeling (NLMEM). NLMEM determined the primary pharmacokinetic parameters: volume of distribution (V/F, 40.9 L/kg) and rate constant (k, 0.0478 h(-1)), and the secondary parameters: dose-normalized area under the curve (AUC/D, 0.29 h x microg/L), clearance (Cl/F, 1.8 L/kg/h), elimination half-life (t(1/2), 16.2 h), C(max/Dose) (4.5 ng/mL), and time of C(max) (T(max), 23.3 h) with improved CV estimates over NCA. Dose linearity was confirmed by anova of parameters derived from NCA by treatment group. Further studies are necessary for determining absolute bioavailability and pharmacokinetic-pharmacodynamic relationships of CTC in group fed, ruminating cattle.

Determination of plasma-chlortetracycline (CTC) concentrations in grazing beef cattle fed one of four FDA approved free-choice CTC-medicated minerals.

Control of active bovine anaplasmosis in the United States is predicated on the use of chlortetracycline (CTC)-medicated feed throughout the vector season. However, data describing population pharmacokinetics of chlortetracycline in cows, on pasture, having free-choice access to CTC-medicated mineral for consecutive months is lacking. This study documented plasma-CTC concentrations in grazing cows during peak vector season in an anaplasmosis endemic herd. Each pasture was administered one of the four Food and Drug Administration approved CTC-medicated mineral formulations and were assigned as follows: 0.77 g/kg, Aureo Anaplaz C700 Pressed (Sweetlix Livestock Supplements, Mankato, MN); 5.5 g/kg, Purina Anaplasmosis Block (Purina Animal Nutrition, Gray Summit, MO); 6.6 g/kg, Stockmaster Aureo FC C6000 Mineral (Hubbard Feeds, Mankato, MN); 8.8 g/kg, MoorMan's Special Range Minerals AU 168XFE (ADM Animal Nutrition, Quincy, IL). Blood samples were collected monthly for determining plasma drug concentration by Ultra performance liquid chromatography (UPLC) and mass spectrometry. Continued plasma-CTC monitoring allowed for characterization of trends between treatment groups (pastures), age groups (<3 yr or >4 yr), and sampling times (June to October). Results indicate formulation (pasture) and time were significant factors affecting concentrations of CTC in plasma. Cows exposed to 5.5 g/kg block formulation recorded higher CTC plasma concentrations compared with other pasture groups (P = 0.037). Plasma-CTC concentrations increased over time (month of measurement; P = 0.0005). Specifically, concentrations measured after 5 months of continuous CTC treatment were higher than those measured in earlier months.

Influence of maternal protein restriction in primiparous heifers during mid- and/or late-gestation on meat quality and fatty acid profile of progeny.

The objective of this study was to evaluate the influence of metabolizable protein (MP) restriction in mid- and/or late-gestation on meat quality characteristics of progeny. Heifers were assigned to 2 levels of dietary protein (control [CON], 102% of MP requirements; or restricted [RES], 80% of MP requirements) at 2 stages of gestation (mid-gestation [MID] and late-gestation [LATE]) in a Balaam's Design crossover treatment structure resulting in 4 treatment combinations (CON-CON, CON-RES, RES-CON, RES-RES). A carryover effect of MID MP treatment on LATE CON indicated CON-CON steaks were more tender (P < .001) than RES CON. Mid-gestation restriction resulted in progeny with increased (P < .05) carcass water, soft tissue moisture, and decreased soft tissue fat percentage compared with progeny from dams receiving MID CON. Reduced maternal MP also differentially influenced the fatty acid profiles of progeny. Results suggest it is possible for progeny to overcome a moderate gestational MP restriction with minimal impacts on carcass composition or meat characteristics.

Feeding and Watering Beef Cattle During Disasters.

Animal care, feeding, and nutrition in the wake of a natural disaster or emergency situation are difficult and require resourcefulness. Immediately following the event, the most basic needs essential for survival of cattle (ie, water, feed, rest, and recovery) should be addressed. Once these basic needs have been addressed, the primary objective then becomes to maintain the present condition of the animals to reduce the potential for negative production outcomes. The objective of this article is to provide a general overview of feeding and managing cattle immediately following a natural disaster or emergency situation.

Serum and plasma metabolites associated with postpartum ovulation and pregnancy risks in suckled beef cows subjected to artificial insemination.

Two experiments were conducted to determine relationships of blood metabolite concentrations, BW, BCS, and rump fat depth with postpartum ovulation and pregnancy risks, as well as their utility in predicting those outcomes in suckled beef cows. In experiment 1, plasma glucose collected 10 and 3 d before AI of suckled beef cows at seven locations did not differ between cows that had resumed estrous cycles (ovulated) before AI compared with anovulatory cows, whereas plasma glucose 3 d before AI was greater (P < 0.01) in cows that became pregnant compared with nonpregnant cows. Serum beta-hydroxybutyrate (BHB) tended (P = 0.09) to be less in ovulatory cows compared with anovulatory cows 10 d before AI, but was unrelated to pregnancy status. Receiver-operator derived true-positive (sensitivity) and false-positive (1-specificity) risks were determined for plasma glucose and serum BHB as predictors for postpartum ovulation and pregnancy status. Serum BHB 3 d before AI produced true-positive and false-positive risks of 82% and 37%, respectively, when predicting ovulatory status before AI. Serum BHB 10 d before AI produced a true-positive and false-positive risks of 92% and 25%, respectively, when predicting pregnancy status. In experiment 2, blood was collected weekly for 12 wk from multiparous suckled beef cows to assess blood metabolite concentrations in addition to concurrent weekly assessments of BW, BCS, and rump fat. When blood metabolites and physical measures were normalized to parturition reflecting changes occurring during the first 6 wk after calving, we observed reduced (P < 0.05) concentrations of serum BHB and NEFA, and greater (P < 0.05) rump fat and BCS in cows that ovulated before first AI, whereas reduced (P < 0.05) plasma glucose was characteristic of cows that became pregnant. When blood metabolites and physical measures were normalized to the onset of the AI program reflecting changes during 6 wk before AI, ovulatory cows had increased (P < 0.05) BCS and lower (P < 0.05) NEFA from 3 to 6 wk before the onset of the AI program compared with anovulatory cows. With all predictor variables in regression models, some multiple correlation coefficients (R2) exceeded 50% when predicting postpartum ovulatory status, but those for predicting pregnancy risk were less than 25%. Although measures of BCS and BHB during 6 wk after calving were related to postpartum ovulation risk, rump fat, glucose, BCS, and NEFA were associated with cows that were ovulatory and pregnant.

Effects of high condensed-tannin substrate, prior dietary tannin exposure, antimicrobial inclusion, and animal species on fermentation parameters following a 48 h in vitro incubation.

Condensed tannins (CT), prior dietary CT exposure, animal species, and antimicrobial inclusion effects on 48 h extent of in vitro fermentation were measured in an experiment with a 3 × 2 × 2 × 3 factorial arrangement of treatments. Treatments included species of inoculum donor (Bos taurus, Ovis aries, or Capra hircus; n = 3/species), prior adaptation to dietary CT (not adapted or adapted), culture substrate (low-CT or high-CT), and antimicrobial additive (none, bacterial suppression with penicillin + streptomycin, or fungal suppression with cycloheximide). Low-CT or high-CT substrates were incubated in vitro using inoculum from animals either not exposed (period 1) or previously exposed to dietary CT (period 2). The extent of IVDMD after 48 h of incubation was greater (P < 0.001) for cultures with low-CT substrate (21.5%) than for cultures with high-CT substrate (16.5%). Cultures with high-CT substrate or with suppressed bacterial activity had less (P < 0.001) gas pressure than cultures with low-CT substrate or cultures with suppressed fungal activity. Total VFA concentrations were greater (P < 0.001) in low-CT cultures when inoculum donors were without prior CT exposure (83.7 mM) than when inoculum was from CT-exposed animals (79.6 mM). Conversely, total VFA concentrations were greater (P < 0.001) in high-CT cultures with tannin-exposed inoculum (59.4 mM) than with nonexposed inoculum (52.6 mM). As expected, CT and suppression of bacterial fermentative activities had strong negative effects on fermentation; however, prior exposure to dietary CT attenuated some negative effects of dietary CT on fermentation. In our experiment, the magnitude of inoculum-donor species effects on fermentation was minor.

Management of mineral supplementation programs for cow-calf operations.

Wasting diseases, hair loss, depigmented hair, skin disorders, noninfectious abortion, diarrhea, loss of appetite, bone abnormalities, tetany, low fertility, and pica have all been attributed to dietary mineral deficiencies or excesses in beef cattle diets. When discussing the mineral nutrition of beef cattle, it is common to focus on readily observable problems such as these. It is a fact, however, that the probability of a particular beef operation ever encountering one of these classical symptoms of deficiency or excess is vanishingly small. Most economic losses associated with mineral nutrition stem from less obvious circumstances (ie, sub-clinical deficiencies or toxicities). Problems with animal health or performance are frequently the result of interaction between one or more minerals in the diet and not due to deficiency or excess per se. Even more likely to cause economic harm is a mineral supplementation program that is mismanaged or overpriced. This article will attempt to distinguish between facts and perceptions regarding mineral nutrition of beef cattle and to make suggestions on cost effective supplementation practices.

The effects of nutritional management on carcass merit of beef cattle and on sensory properties of beef.

The ultimate goal of feeding beef cattle is to develop a meat product that satisfies consumer needs. Nutritional management plays a significant role in determining carcass merit of beef cattle. Certain management procedures (eg, metabolic modifiers, early weaning), general animal health (eg, history of respiratory disease), and certain feed ingredients (eg, trace minerals, antioxidants) can have positive and negative effects on the overall quality of beef that is supplied to the consuming public.