Cow-calf Operations Research Articles

Bovine respiratory disease during the mid-portion of the feeding period: Observations from vaccination history, viral and bacterial prevalence, and rate of gain in feedlot cattle

The objective of this research was to provide preliminary observations related to bovine respiratory disease (BRD) morbidity in high-performing cattle related to cow-calf operations, number of vaccines received before the feedlot, viral and bacterial presence in the nasal cavity during the mid-feeding period, and rate of gain related to incidence of BRD. Health outcomes were evaluated from 4,346 cattle. Cattle were evaluated by the number of modified-live-viral, Mannheimia haemolytica, Histophilus somni, or Clostridiaspp. vaccines administered before feedlot entry. Individual animal rate of gain was evaluated by incidence of BRD. Nasal swabs were collected from BRD cases and controls to evaluate presence of viruses and bacteria. First treatment for BRD was associated with the number of times cattle received modified-live-viral vaccines before the feedlot (P = 0.02). Cattle administered a modified-live-viral vaccine 3 times before the feedlot had a greater first treatment for BRD (21.32%) compared with cattle vaccinated 1 time (9.56%; P = 0.06). Cattle that developed BRD had lower (P < 0.01) ADG through the first 30 d on feed compared with clinically healthy cattle. Preliminary nasal swab PCR results show common respiratory viral or bacterial pathogens were not identified in BRD during the mid-feeding period. There is great variability in BRD morbidity among cow-calf operations. A greater number of vaccinations administered before the feedlot was detrimental to health outcomes. Additional research is needed to further evaluate the entire host, environment, and pathogen triad for development of BRD.

Survey of veterinary involvement in management decisions on Mississippi cow-calf operations

The objective of this study was to describe veterinary involvement in management decisions on Mississippi cowcalf operations. Anonymous surveys were mailed to 1,275 members of the Mississippi Cattlemen’s Association. Multivariable logistic regression using manual forward variable selection was used to test demographic and management factors for association with veterinary involvement outcomes. Significance was defined at alpha=0.05. Three-hundred eight surveys (24%) were returned, with 292 (95%) respondents being active in cow-calf production. Fifty-three (18%) of 289 respondents were located in a county contained in a rural area food animal medicine shortage area designated by the USDA-NIFA in 2020. One-hundred seventeen of 285 (41%) indicated regular veterinary involvement in management decisions on their operation. Of these 117, 56 (48%) said their veterinarian uses their cattle health and production records to provide management recommendations. Seventy-five (27%) of 283 respondents indicated they would consider paying their veterinarian to provide cattle health and production record management services. Factors associated with regular veterinary involvement in management decisions on cow-calf operations were regularly recording of antibiotic treatments (OR=3.2) and herd size (50-99 head: OR= 1.6; ≥100 head: OR=2.5, compared to 1-49 head). Opportunity exists for veterinarians to be more involved in management decisions on Mississippi cow-calf operations.

Prepartum protein supplementation in Angus cows

Cow calf operations in Argentina are managed under extensive grazing condition and the quality of forages is often poor during the second half of gestation. The present work investigated the effects of two levels of crude protein (CP) provided to mature dams during late gestation on their subsequent reproductive performance and milk yield, heifer’s (F1) postweaning growth, reproductive performance, milk production and grand offspring growth (F2). Sixty eight multiparous cows were randomly assigned to either low (LP, 6% CP) or high protein (HP, 12% CP) diets. Body weight (BW) and body condition score (BCS) of cows were determined, and milk production was measured until weaning. In the female, progeny time and BW at puberty, were determined. Reproductive and milk performance of female offspring until weaning, were recorded, as well as their offspring growth until weaning. The HP cows had greater BW gain during the prepartum period (P &lt; 0,01) and tended to gain more BCS (P = 0,06) than LP cows. Pregnancy rates, milk production and composition were not influenced by dietary treatments. At puberty (P = 0,01) and pregnancy diagnosis (P = 0,05), HP heifers were heavier than LP heifers. No dam nutrition effects were found on offspring age at puberty (P = 0,98), final pregnancy rate (P = 0,28) or milk yield (P = 0,76), but heifers born from LP dams had greater milk protein percentage (P = 0,04) and tended to produce more milk fat percentage (P = 0,08) compared with HP heifers. The LP grand offspring grew faster from birth until weaning compared with HP grand offspring (P &lt; 0,01). In conclusion, protein level of the diet during the prepartum period in multiparous beef cows affected the BW change at calving, without consequences on reproductive performance and milk quality and yield. Protein supplementation during late gestation did not affect reproductive performance of the offspring heifers but did impact their BW evolution, milk quality and grand offspring performance. The use of diet with low amount of protein during late gestation can affect progeny development and ability to nourish subsequent generations.

Experimentación y validación de tecnologías adecuadas para pequeños productores ganaderos

&lt;p&gt;Se evaluó la suplementación mineral con fósforo y sodio en rodeos bovinos de cría en un área con deficiencia de dichos elementos en el departamento Mercedes, provincia de Corrientes, Argentina. Se realizó la práctica en 3 establecimientos durante 4 años en los que se totalizaron 176 observaciones en los lotes suplementados y 155 en los no suplementados. Se obtuvo un 59% de preñez al suplementar y 44% en los lotes que no recibieron dicha práctica, lo cual resulta rentable para el productor.&lt;/p&gt;

Antimicrobial Resistance at Two U.S. Cull Cow Processing Establishments

Culled beef cows (cows that have reached the end of their productive life span in cow-calf operations) and culled dairy cows represent approximately 18% of the cattle harvested in the United States annually, but data on antimicrobial resistance (AMR) in these cull cattle are extremely limited. To address this data gap, colon contents were obtained from 180 culled conventional beef cows, 179 culled conventional dairy cows, and 176 culled organic dairy cows (produced without using antimicrobials). Sponge samples were also collected from 181 conventional beef, 173 conventional dairy, and 180 organic dairy cow carcasses. These samples were obtained on 6 days (3 days each at two beef harvest and processing establishments). At one establishment, 30 samples of beef manufacturing trimmings from conventional cows and 30 trim samples from organic dairy cows were acquired. All 1,129 samples were cultured for Escherichia coli, tetracycline-resistant (TETr) E. coli, third-generation cephalosporin-resistant (3GCr) E. coli, Salmonella, and 3GCrSalmonella. Metagenomic DNA was isolated from 535 colon content samples, and quantitative PCR assays were performed to assess the abundances of the following 10 antimicrobial resistance genes: aac(6')-Ie-aph(2″)-Ia, aadA1, blaCMY-2, blaCTX-M, blaKPC-2, erm(B), mecA, tet(A), tet(B), and tet(M). For colon contents, only TETrE. coli (P < 0.01), 3GCrE. coli (P < 0.01), and erm(B) (P = 0.03) levels were higher in conventional than in organic cows. Sampling day also significantly affected (P < 0.01) these levels. Production system did not affect the levels of any measured AMR on carcasses or trim. The human health impact of the few significant AMR differences could not be determined due to the lack of standards for normal, background, safe, or basal values. Study results provide key heretofore unavailable data that may inform quantitative microbial risk assessments to address these gaps.

121 The impact of changing consumer preferences on production and management practices at cow-calf level

Abstract Changes in cow-calf operations and management need to be deliberate and focus on consumer preferences that are substantive and enduring. For the sake of argument these preference changes could include: 1) continued erosion of the image of the cattle industry; 2) growth in demand of high quality grade beef, likely branded, and available at an affordable price; 3) production systems that yield improvements in cattle health, have a lesser environmental impact, and demonstrate prudent animal care and well-being; 4) Specification systems that may or may not include stipulations such as grass fed or non-implanted. At the ranch level there will be continued pressure to pursue rapid, efficient growth, marbling, structural soundness, and immunocompetence via genetic selection. A major step to reduce health problems is to reduce co-mingling. To achieve this goal breeding programs will change to improve the genetic and phenotypic uniformity and possibly the heterosis of the calf crop on each ranch. The National calving season needs to be more uniformly distributed throughout the year. New, more relevant cattle performance metrics will be developed. Calves that fit a branded production stream will have more value. Production streams that require Verified processes will be inequitably distributed across herd size because of associated costs, forcing smaller herds to either coop, vertically integrate, or accept generic cattle prices. Because of the diversity of environments and corresponding compatible bio-types of cows, identifying the profitable combination of specific branded systems with the genetics, calving season, labor, resource management and nutrition program of the ranch is very complicated. It will be increasingly necessary to put incremental response assessments in the context of the greater production-product system. Successful adaptors will place a much greater reliance on strong technical support in the areas of genetics, nutrition, growth, animal handling, documentation, and branded production streams.

268 Administering an appeasing substance to optimize welfare and performance of receiving cattle

Abstract This experiment evaluated the impacts of bovine appeasing substance (BAS) administration on performance, health, and physiological responses of feedlot cattle during a 45-d receiving period. A total of 342 recently-weaned Angus-influenced steers, originating from 16 cow-calf operations, were obtained from an auction yard on d -1 and road-transported (12 h) to the feedlot. Upon arrival on d 0, body weight (BW) was recorded and steers were ranked by BW and source and assigned to receive BAS (Nutricorp, Araras, SP, Brazil; n = 171) or placebo (diethylene glycol monoethyl ether; CON; n = 171). Treatments (5 mL) were topically applied to the nuchal skin area of each animal. Within treatment, calves were allocated to 1 of 24 drylot pens (12 pens/treatment) and received a free choice total-mixed ration from d 1 to 45. Calves were assessed for bovine respiratory disease (BRD) signs and feed intake was recorded from each pen daily. Steer BW was again recorded on d 1, 7, 17, 31, and 45, whereas blood samples were collected from 5 steers/pen concurrently with each BW assessment. Average daily gain was greater (P = 0.05) in BAS vs. CON calves, although final BW did not differ (P = 0.36) between treatments. No treatment effects were detected for feed intake (P = 0.95), resulting in greater (P = 0.05) feed efficiency in BAS vs. CON steers. No treatment effects were detected (P ≥ 0.37) for plasma concentrations of haptoglobin, whereas plasma cortisol concentrations were greater (P = 0.05) in CON vs. BAS steers on d 7 (treatment × day; P = 0.07). Incidence of BRD was greater (P ≤ 0.05) in BAS vs. CON on d 6 to 10 and d 18 to 21 (treatment × day; P &amp;lt; 0.01), although overall BRD incidence did not differ (P = 0.24) between treatments. The number of antimicrobial treatments required per steer diagnosed with BRD symptoms to recover from sickness was greater (P = 0.04) in CON vs. BAS calves. No treatment differences were detected (P ≥ 0.41) for mortality incidence, or proportion of steers removed from the experiment due to extreme sickness. Results from this experiment indicate BAS administration upon feedlot entry improved average daily gain by enhancing feed efficiency. Administration of BAS facilitated earlier detection of BRD and reduced the need for antimicrobial treatments. Collectively, these results suggest BAS administration as a promising strategy to benefit performance and immunocompetence of feedlot receiving cattle.

177 Development of Feasible Pre-Conditioning Programs for Limited Resource Cow-Calf Producers in North Florida

Abstract Cost-effective calf pre-conditioning programs utilizing high-quality pastures and minimal grain supplements can improve net returns of limited-resource cow-calf operations. The objective of the study was to evaluate the feasibility of utilizing two different supplements in a forage-based 45-day pre-conditioning program. Twenty-one Angus-cross calves averaging 6 months of age were assigned randomly at weaning to two groups based on sex and initial body weights: commercially available complete feed, 16% crude protein (Group 1), and corn-mineral mix, 10% crude protein (Group 2, Control). Calves were backgrounded on natural pastures that were predominantly Bahia grass and acclimated to the feeds for 2 weeks prior to the start of the actual trial. Supplementation rates for both groups were maintained at 1.0 lb./150 lb. calf BW equivalent to 2.0 lbs./calf/day. Groups were rotated among pasture plots weekly depending on forage availability. Calves were weighed at 2-week intervals during the study. Data were analyzed by analysis of covariance using GLM methods of SAS. No differences were observed among groups in calf BW gain (P &amp;lt; 0.74) and net returns (P &amp;lt; 0.92). Initial calf BW were 357.2 ± 15.2 vs. 370.9 ± 16.6 lbs., whereas final BW were 398.2 ± 17.2 vs. 408.6 ± 20.1 lbs., for groups 1 and 2, respectively. Thus, average weight gains were 41.0 vs 37.7 lbs., for groups 1 and 2, respectively (Table 1). Feed costs were $17.97 vs. $16.97 for groups 1 and 2, respectively culminating in a $0.44 vs. $0.45 cost per lb. of gain, respectively. The current market price of a 400 lb. calf at the North Florida Livestock market averages $1.39/lb. Therefore, pre-conditioning calves using complete feed provides a $0.95/lb. return, whereas using corn-mineral mix returns a profit of $0.93/lb. Therefore, the corn-based supplement compared favorably to the commercially available complete feed in this system.

161 Effects of management strategies on environmental footprints of cow-calf production in the United States

Abstract Estimates of beef cattle production’s national and regional cradle to farm grate environmental impacts have been quantified. As baseline footprints are now established, cow-calf dietary and production management strategies can be evaluated for their capacity to reduce environmental impacts. Accordingly, our objective was to quantify environmental changes from implementing management strategies in cow-calf production. Ten management strategies were identified, with each related to animal performance, feed management, or pasture management. Each strategy was incorporated into a representative cow-calf operation for each of 6 major regions of beef production in the United States and simulated with the Integrated Farm System Model (IFSM) using local soil and climate data. A combined strategy was also identified based on results of the individual strategies, which was simulated with IFSM. Farm-gate life cycle assessment was used to estimate carbon (C) footprint, fossil energy use, blue water use, and total reactive nitrogen (N) loss for all production systems and strategy combinations. Averages of each environmental metric for the cow-calf sector were based on weighted averages of regional cow inventory data. Averaged across all strategies, the reduction in C footprint was 4.1% and fossil energy use was reduced 3.5% for the cow-calf sector. Improved feed efficiency (8.0%) and terminal cross (7.1%) strategies reduced C footprint to a greater extent than other strategies simulated (2.0%). Fossil energy use was reduced by 8.3, and 6.5% from improved feed efficiency and terminal cross strategies, respectively. Early weaning increased C footprint, fossil energy use, blue water use, and reactive N loss by 13.8, 17.8, 20.2, and 12.7%, respectively. The combined strategy, including improved feed efficiency, improved fiber digestion, calf implant use, increased weaning rate, reduced cow body weight, and terminal cross strategies, reduced C footprint (18%), fossil fuel use (18%), blue water use (23%), and reactive N loss (15%).

385 Awardee Talk: Impacts of temperament on productive and reproductive responses of Bos taurus and B. indicus females

Abstract Temperament is defined as the fear-related behavioral responses of cattle when exposed to human handling. Our group evaluates cattle temperament using: 1) chute score: 1 to 5 scale that increases according to excitable behavior during chute restraining, 2) exit velocity: speed of an animal exiting the squeeze chute, 3) exit score: dividing cattle according to exit velocity into quintiles using a 1 to 5 scale (1 = slowest quintile; 5 = fastest quintile), and 4) temperament score: average of chute and exit scores. Subsequently, cattle are assigned a temperament type; adequate temperament (ADQ; temperament score ≤ 3) or excitable temperament (EXC; temperament score &amp;gt; 3). Our group associated these evaluation criteria with reproductive responses of Bos taurus and B. indicus-influenced females. Cattle classified as EXC had greater (P ≤ 0.04) plasma cortisol vs. ADQ during handling, independent of breed type or parity. Both B. taurus and B. indicus cows classified as EXC had reduced (P ≤ 0.09) annual pregnancy rates vs. ADQ cohorts, resulting in decreased calving rate, weaning rate, and kg of calf weaned/cow exposed to breeding. Bos indicus heifers classified as EXC as yearlings had less (P &amp;lt; 0.01) growth rate and delayed puberty attainment by 15 months of age compared with ADQ heifers. Bos taurus heifers that reached puberty by 12 months of age had less (P ≤ 0.05) temperament score and plasma cortisol concentrations at weaning compared with heifers that did not reach puberty. Acclimating B. indicus-influenced and B. taurus heifers to human handling after weaning improved (P ≤ 0.02) temperament and hastened puberty attainment. Hence, temperament impacts productive and reproductive responses of beef females independent of breed type and parity. Strategies to improve herd temperament are imperative for optimal production efficiency of cow-calf operations based on B. taurus and B. indicus-influenced cattle.

84 Evaluation of hair coat shedding ability as an adaptive trait in Angus cattle in the southern U.S

Abstract The objective of this study was to evaluate winter hair coat shedding ability and the association to cow production performance. This work was a collaborative effort from the S-1064 multi-state research project. Data were collected on spring and fall-calving purebred and commercial Angus females with calves (n = 1192) from March until July from 2008 to 2018 in Mississippi, Arkansas and Texas. Dams were observed once monthly by two trained technicians for winter hair coat shedding and give a visual hair shedding score of 1 to 5 with 1 indicating 100% shed, 2 = 75% shed, 3 = 50% shed, 4 = 25% shed, and 5 indicating 0% shedding of the winter hair coat. Month of first shedding (MFS) was determined once a female reached an average hair shedding score of ≤ 3.5 for any given month. Calf birth and weaning weights were considered as performance of the dam. For cow performance, the response variables included AdjBW and d205wt of the calf. Data were analyzed using the MIXED procedure of SAS with significance declared at P ≤ 0.05. The model included MFS as a fixed effect with calf sex as a covariate and calf sire as a random effect. Females that obtained a shedding score of ≤ 3.5 by May had heavier calves at birth (P ≤ 0.01) when compared with those that shed in June and July, with July weights being the lightest. Females that scored ≤ 3.5 by May has significantly heavier d205wt (P ≤ 0.01) when compared to those that shed by June and July. When comparing locations, females in Arkansas shed later (P ≤ 0.01) when compared with both Mississippi and Texas, which were similar. Shedding ability could be an important economic trait to be considered in cow-calf operations.

An agent-based simulation model to compare different reproductive strategies in cow-calf operations: Technical performance

The objective of this study was to create a stochastic, agent-based simulation model of a synthetic population of beef cattle, and then use it to compare the technical performance of different reproductive strategies. The model was parameterized using data from a real beef cattle herd and from the peer-reviewed scientific literature to represent a Nelore cattle herd in the state of São Paulo, Brazil. Ten scenarios were evaluated: natural mating (NM) only (ONM); one timed artificial insemination (TAI) plus NM (1TAI + NM); two TAI plus NM, with 24, 32, and 40 days between inseminations (2TAI/24 + NM, 2TAI/32 + NM, and 2TAI/40 + NM, respectively); three TAI without NM, with 24, 32, and 40 days between TAI (3TAI/24, 3TAI/32, and 3TAI/40, respectively); and three TAI plus NM, with 24 and 32 days (3TAI/24 + NM and 3TAI/32 + NM, respectively). NM began 10 days after the last TAI and was performed until the end of the breeding season. The size of the female herd was set to contain up to 400 individuals. The bull population was established at 0, 7, or 15 bulls depending on the used scenario. Simulation was performed for 5000 days. The outcomes for each scenario are means ± S.E. assessed on 32 farms at 1-day time intervals and on an animal-by-animal basis after steady state was reached (1825 days). The 3TAI/24 + NM scenario resulted in a greater number of births (279.85 ± 0.47 births), while the ONM scenario had the least value (202.38 ± 0.43 births). The heaviest males and females at weaning belonged to 3TAI/24, with 190.85 ± 0.17 kg for males and 173.89 ± 0.13 kg for females. The ONM scenario had the lightest males (166.84 ± 0.18 kg) and females (151.75 ± 0.16 kg). The greatest and least total pregnancy rates were found in 3TAI/24 + NM (0.91 ± 0.00) and ONM (0.62 ± 0.00), respectively. The ONM scenario required 52.5 days more than scenarios that included TAI to reach 50% of pregnancy. The greatest ages at culling for cows was 3TAI/24 + NM (3658.88 ± 10.41 days). In contrast, the lowest age at culling was found in ONM (2823.93 ± 8.28 days). We concluded that the proposed model represents the main interactions of a real beef cattle herd. It has all the advantages of a physical experiment, but does not require incurring significant expenses nor altering the real system. This study offers evidence that the scenarios that present the best technical performance are those that used TAI with a 24-day interval between inseminations.

Effects of inorganic selenium injection on the performance of beef cows and their subsequent calves

Sixty-seven pregnant Angus cows and their subsequent calves were used in a randomized design to evaluate the effect of inorganic Se injection from 80 d of gestation until weaning on cow reproductive parameters, BW and BCS evolution, milk yield and quality, calf growth and calf hematology parameters. The treatments were as follows: 1) Se+: cows were administered Se as sodium selenite at doses of 0.05 mg/Kg of BW at 80, 140, 200, 260 d of gestation and 30, 90, 150 and 240 d of lactation. Calves from Se + cows were Se as sodium selenite subcutaneously injected with a dose of 0.05 mg/Kg of BW at 70, 104, 144 d of age; 2) Control: cows and calves were administered sterile NaCl solution (9 g/l) at the same volume and intervals as Se + treatment. At the start of the experiment, forage Se concentration was 58.6 ppb ± 7.6 ppb, and cow whole blood Se concentration was similar (P > 0.10) between treatments (Se+, 29.3 ± 0.3 ppb; Control, 28.1 ± 0.5 ppb). After Se injection, cow whole blood Se concentration was increased (P < 0.01) in Se + cows in relation to control cows until the end of the experiment. Calf whole blood Se concentration was increased (P < 0.01) at birth and 30 d of age in calves from Se + cows compared to calves from Control cows. However, calf whole blood Se concentration was not different (P > 0.10) between treatments at d 70 after birth. After the first Se injection (70 d of age), calf whole blood Se concentration was increased (P < 0.01) at 104 and 144 d of age in calves from Se + cows compared to calves from Control cows. Cow BW and BCS did not differ (P > 0.10) between treatments throughout the experiment. Ovarian follicle diameter measured by ultrasound 47 d postpartum was greater (P = 0.03) in Se + cows compared to Control cows. Pregnancy rate to fixed time artificial insemination (FTAI), overall pregnancy rate (P > 0.10) and pregnancy loss (P = 0.19) did not differ between groups. Selenium injection did not affect (P > 0.10) milk yield and composition. Calf morphometric parameters, BW at birth and growth rate during lactation were not affected (P > 0.10) by treatments. No significant effect (P > 0.10) was observed between treatments on hematological results of blood samples from calves at weaning. Results of this study shown that inorganic Se injection was an efficient tool to improve Se-status in cow-calf operation under extensive management. Selenium injection increased follicle diameter in postpartum beef cow, however, did not affect the rest of the variables studied.

Preconditioning beef cattle for long-duration transportation stress with rumen-protected methionine supplementation: A nutrigenetics study.

In general, beef cattle long-distance transportation from cow-calf operations to feedlots or from feedlots to abattoirs is a common situation in the beef industry. The aim of this study was to determine the effect of rumen-protected methionine (RPM) supplementation on a proposed gene network for muscle fatigue, creatine synthesis (CKM), and reactive oxygen species (ROS) metabolism after a transportation simulation in a test track. Angus × Simmental heifers (n = 18) were stratified by body weight (408 ± 64 kg; BW) and randomly assigned to dietary treatments: 1) control diet (CTRL) or 2) control diet + 8 gr/hd/day of top-dressed rumen-protected methionine (RPM). After an adaptation period to Calan gates, animals received the mentioned dietary treatment consisting of Bermuda hay ad libitum and a soy hulls and corn gluten feed based supplement. After 45 days of supplementation, animals were loaded onto a trailer and transported for 22 hours (long-term transportation). Longissimus muscle biopsies, BW and blood samples were obtained on day 0 (Baseline), 43 (Pre-transport; PRET), and 46 (Post-transport; POST). Heifers’ average daily gain did not differ between baseline and PRET. Control heifer’s shrink was 10% of BW while RPM heifers shrink was 8%. Serum cortisol decreased, and glucose and creatine kinase levels increased after transportation, but no differences were observed between treatments. Messenger RNA was extracted from skeletal muscle tissue and gene expression analysis was performed by RT-qPCR. Results showed that AHCY and DNMT3A (DNA methylation), SSPN (Sarcoglycan complex), and SOD2 (Oxidative Stress-ROS) were upregulated in CTRL between baseline and PRET and, decreased between pre and POST while they remained constant for RPM. Furthermore, CKM was not affected by treatments. In conclusion, RPM supplementation may affect ROS production and enhance DNA hypermethylation, after a long-term transportation.

Impact of bovine leukemia virus infection on beef cow longevity

Bovine leukosis is a chronic lymphoproliferative disorder caused by bovine leukemia virus (BLV). Previous studies estimate that 38 % of cow-calf beef herds and 10.3 % of individual beef cows in the US are BLV seropositive. About 70 % of BLV infected animals are asymptomatic carriers of the virus, while less than 5% develop lymphosarcoma, the leading reason for carcass condemnation at the US slaughterhouses. Studies provide evidence that BLV infection leads to decreased immune function making animals more vulnerable to other diseases, which could shorten their productive lifespan and increase economic losses in the cattle industry. BLV seropositive dairy cows are reportedly more likely to be culled sooner compared with their uninfected herd mates. Beyond simple prevalence studies, little is known about the impact of BLV infection in beef cattle production or specifically on beef cow longevity. Our objective was to determine the association between BLV infection and cow longevity in beef cow-calf operations. Twenty-seven cow-calf herds from the Upper Midwest volunteered to participate in this study. Female beef cattle (n = 3146) were tested for serum BLV antibodies by ELISA. A subsample of 648 cows were also tested for BLV proviral load (PVL). Culling data was collected for the subsequent 24 months. Twenty-one herds (77.7 %) had at least one BLV-infected animal, and 29.2 % (930/3146) of tested animals were BLV seropositive. Of the BLV-positive cows, 33.7 % (318/943) were culled compared with 32.1 % (541/1682) of the seronegative cows. BLV status did not affect cows' longevity within herds (P = 0.062). However, cows with high BLV PVL had decreased survival within the herd compared with ELISA- negative cows (P = 0.01). Overall, infection with BLV did not impact beef cow longevity unless the disease had progressed to a point of high BLV PVL.

Assessment of Brix refractometry to estimate immunoglobulin G concentration in beef cow colostrum.

BackgroundBrix refractometry can be used to assess colostral immunoglobulin G (IgG) concentration, but studies identifying Brix percentages to detect high‐ and low‐IgG colostrum are lacking for beef cows and interlaboratory agreement is unknown.ObjectivesEvaluate Brix refractometer performance and interlaboratory agreement for assessing beef cow colostrum IgG concentration, including determination of thresholds to identify colostrum containing IgG concentrations <100 g/L and ≥150 g/L.AnimalsBeef cows (n = 416) from 11 cow‐calf operations in Alberta, Canada.MethodsColostral IgG concentrations were measured using radial immunodiffusion (RID) and estimated by Brix refractometry for this retrospective study. Spearman correlation coefficients were assessed between RID and Brix refractometry. Likelihood ratios and misclassification cost‐term analysis were used to determine optimal Brix percentages for detecting colostrum containing IgG concentrations <100 g/L and ≥150 g/L. Concordance correlation coefficient (CCC) and Bland‐Altman analyses were performed for Brix percentages obtained at 3 different laboratories.ResultsBrix percentages obtained at 3 laboratories were positively correlated with IgG results (r = 0.72, 0.68, and 0.76, respectively). Colostrum Brix percentages of <24% and ≥30% were optimal for indicating IgG concentrations of <100 g/L and ≥150 g/L, respectively. Interlaboratory agreement was substantial, with CCC ranging from 0.89 to 0.96 and Bland‐Altman analysis showing small mean differences (−1.2% to 0.09% Brix) and narrow limits of agreements (−4.8% to 2.4% Brix) among laboratories.Conclusions and Clinical ImportanceBrix refractometry shows good potential for reliably estimating IgG concentrations in beef cow colostrum across multiple laboratories and can be recommended to aid colostrum management decisions on farms.

An innovation path in Argentinean cow–calf operations: Insights from participatory farm system modelling

The information of how the high climatic variability in the south‐west Buenos Aires Province (SWBS) region, Argentina, impacts on existing cow–calf operations is needed. This research uses a combination of quantitative (modelling) and qualitative (workshops) methodologies. The objective was to assess, under interannual climate variability, the productive and economic performance and greenhouse gas emissions and the marginal value of additional feed of four cow–calf systems arranged as a potential farm innovation path in the SWBS, Argentina. Modelling results showed that along this technological path where forage crops are decreased, perennial pastures are increased and anticipated weaning is included, productive and economic outcomes increased and the emission intensity decreased. How extra feeds may be used to cope with seasonal and interannual feeding was also identified. Moreover, barriers to adopt the suggested farm innovation path were identified by farmers, consultants and extensionists and strategies and their implication discussed.

Cow-calf management practices in Mexico: Reproduction and breeding

Beef cattle breeding has developed in extensive grazing systems in Mexico, concerning the livelihood of over one million families and affecting the use of natural resources. Reproductive efficiency is a major determinant of both the environmental impact of the herd, and the economic viability of the cow-calf production system. However, as reproductive traits have low heritability, reproductive efficiency can be largely influenced by herd management practices. Thus, a questionnaire was administered as personal interviews to 3280 producers, to investigate the prevalence of practices that could directly influence the reproductive outcome of their cattle. Results show that year-round breeding (93%) and natural service by the bull (97.4%) are the most common mating methods. However, only 41% of producers evaluate the breeding soundness of their bulls, and diagnostic testing for specific reproductive diseases of the sires is barely performed in 20% of the farms. The main declared reason for replacing the bull is old age (26.8%), which is followed by to avoid inbreeding (68.4%). Less than 10% of the operations use methods for the synchronization of the estrous cycle, and most farmers breed their heifers for the first time after 2 years of age (73%). Diagnosis of pregnancy is performed in merely 31% of operations, with 23% of the producers declaring to discard non-pregnant cows. Energy or protein feed supplements are provided to the cattle in 63% of the production units, whilst mineral supplements are given in 79% of the farms. Calves are typically weaned between 6 months and a year of age (85%). Only 16% of operations vaccinate against brucellosis and 17.5% against other reproductive diseases (IBR-DVB-VSR and Leptospirosis). The present study showcases a low frequency of adoption of basic reproductive management practices by cow-calf operations in Mexico. Advancement of these practices, as well as implementation and promotion of associated technologies, denotes an area of opportunity to improve the reproductive efficiency of the national herd.

Occurrence and Antimicrobial Resistance Profiles of Campylobacter jejuni, Campylobacter coli, and Campylobacter upsaliensis in Beef Cattle on Cow-Calf Operations in South Africa.

This study investigated occurrence and antimicrobial resistance profiles of Campylobacter spp. isolates in beef cattle on five cow-calf operations in South Africa. A total of 537 fecal samples from adult beef cattle (n = 435) and rectal swabs from calves (n = 102) were screened for Campylobacter jejuni, Campylobacter coli, and Campylobacter upsaliensis by culture and polymerase chain reaction. Furthermore, 86 Campylobacter spp. isolates including 46 C. jejuni, 24 C. coli, and 16 C. upsaliensis were tested for antimicrobial resistance against a panel of 9 antimicrobials. Overall, Campylobacter spp. was detected in 29.7% of cattle. Among the 158 Campylobacter spp.-positive cattle, 61.8% carried C. jejuni, 25% carried C. coli, and 10% carried C. upsaliensis. Five animals (3.1%) had mixed infections: three cows carried C. jejuni and C. coli concurrently, one cow had both C. jejuni and C. upsaliensis, and one cow harbored C. coli and C. upsaliensis. Antimicrobial resistance profiling among 86 Campylobacter spp. isolates revealed that 52.3% of the isolates were resistant to one or more antimicrobials. Antimicrobial resistance was observed in 46.7% of C. jejuni isolates, 35.6% of C. coli, and 17.8% of C. upsaliensis. Thirty-six percent of isolates were resistant to clindamycin, 19.7% to nalidixic acid, 18.6% to tetracycline, and 17.4% to erythromycin. Lower resistance rates were recorded for azithromycin (8.1%), florfenicol (3.4%), gentamicin (4.8%), and telithromycin and ciprofloxacin (5.8%). Multidrug resistance (MDR) was observed in 32.5% of isolates. Significantly higher levels of MDR were detected among C. jejuni (36.9%) and C. coli (33.3%) isolates in comparison to C. upsaliensis (18.7%). Two main multiresistance patterns were detected: nalidixic acid/clindamycin (17.8%) and tetracycline/clindamycin (14.2%). To the best of our knowledge, this is the first study which has shown that beef cattle on cow-calf operations in South Africa constitute an important reservoir and a potential source of clinically relevant and antimicrobial resistant Campylobacter spp. strains.

Comparison of parasite load and average daily weight gain in suckling beef calves treated with macrocyclic lactones in either an extended-release injectable or a pouron formulation

The objective of the study was to compare the effect of macrocyclic lactones anthelmintic in either an extended-release injectable (ERI) or a pour-on (PO) formulation on parasite load and average daily weight gain in suckling beef calves. Spring born Angus cross beef calves (n=1228) grazing on 17 pastures from 4 cow-calf operations in Washington State during 2017 were included. Calves in each pasture were randomly assigned to ERI (n=611; Long Range®, 50 mg of eprinomectin/ml, Merial Inc., Duluth, GA, USA; @ 50 mg or 1ml/50 kg BW) or PO (n=671; Ivomec®, 5 mg ivermectin/ml; Merial Inc., Duluth, GA; @ 500 mcg or 1 ml/10 kg BW) treatment 105 days prior to weaning (approximately at 8 months of age) at the time of pasture turn-out in mid-May. Calves were weighed initially, at mid-trail (approximately 55 days after start) and at weaning. Faecal samples were taken from a subset of calves (n=30/pasture; 15 in each treatment group, a total of 510 calves) for faecal egg counts (FEC) at the start of the study and again at 15, 30, 60 and 90 d later. The data were analyzed using a mixed model. The FEC did not vary between calves in treatment and control groups on day 0 (P>0.1). However, accounting for temperament by treatment interaction, ERI treated calves had lower FEC compared with PO treated calves on day 90 (P<0.01). Accounting for gender (P<0.05), temperament (P<0.05) and treatment by age (P<0.01), ERI treated calves gained more weight compared with PO treated calves (P<0.01). In conclusion, treatment of nursing calves at late-spring with ERI experienced a reduction in GI (gastrointestinal) parasite load and a measurable but modest increase in weight gain compared with calves treated with PO.