Best of the best of the 2018 Onderstepoort Feedlot Challenge

The Onderstepoort Feedlot Challenge (OPFLC) is a group based Action Learning Project (ALP) within the Bachelor of Veterinary Science (BVSc) programme of the University of Pretoria (UP) (1-3). Initiated in 2007, the OPFLC maintains its original aims to stimulate interest in production animals through exciting practical exposure; to promote student wellbeing through physical activity and play; to apply “soft” skills such as leadership, communication, business and management skills; and to develop a culture of teamwork, self-learning and critical scientific reasoning amongst future veterinarians(4-7). The OPFLC uses real cattle, real facilities, real resources, and real problems encountered in a typical feedlot, within a simulated commercial environment. The competition between the participating student groups involves running the most economical and ethically acceptable feedlot from auction to abattoir, and demonstrating evidence of learning (7). Progress is monitored and feedback given continually and students are guided to make evidence based decisions in their daily feedlot management. Small changes are made to the detail of the OPFLC every year to keep it innovative. The educational success and validity of ALPs in veterinary education have been reported over the past decade and resulted in similar ALPs established within the veterinary curriculum of UP as well as at other institutions (8-12). Part of the ALP includes an assignment in which each student has to report, based on the individual task assigned, what s/he has learnt during the ALP. Students are encouraged to interpret their own data against existing knowledge to support their findings scientifically. Students are assessed in two phases (first for feedback then for grading) using a predetermined scoring rubric through UP’s online learning management system, ClickUP (Blackboard®). This document represents the best of the eight OPFLC assignments submitted for each topic in 2018, and serves as an example for future students and to acknowledge excellence.Includes bibliographical referencesThe 2018 Onderstepoort Feedlot Challenge was supported financially and through other means by: Zoetis, Vleissentraal Bosveld, Sparta beef, Tongaat, Hulett, Afgri, Fepro and SA Premixab201

The effect of cow-level factors on colostrum quality, passive immunity and health of neonatal calves in a pasture-based dairy operation

A study of 95 cows (19 primiparous and 76 multiparous) and their offspring was performed on a pasture-based dairy in the coastal region of South Africa. Collected data included weight changes during the dry period, colostrum immunoglobulin G (IgG) and calf serum IgG at 24–48 h after birth. Colostrum and serum IgG concentrations were measured using radial immunodiffusion and colostrum was regarded as having adequate IgG concentration if the amount was 50 g/L. Calf serum IgG concentration of 10 g/L was considered an adequate transfer of passive immunity. The median (range in parentheses) colostrum quality for cows with weight loss during the dry period was 23.1 g/L (9.0, 108.1) compared with 61.9 g/L (10.9, 200.0) in cows without weight loss. The median serum IgG of calves from cows with weight loss was 9.9 g/L (0.5, 44.6) compared with 14.0 g/L (0.5, 76.3) in calves from cows that did not lose weight during the dry period. Cows experiencing weight loss were four times more likely to have colostrum with lower concentrations of IgG (OR = 0.25; 95% CI, 0.07–0.88; P = 0.030). Lactation number was also significantly associated with colostrum IgG concentration (P < 0.001), with younger cows tending to have higher IgG concentrations. Failure of passive transfer did not have a significant effect on any calf-health or production variables measured in the study. The effect of dry-cow feeding on colostrum IgG concentration is poorly understood and inadequate pasture management could have an impact on colostrum quality in pasture-based dairy herds.The University of Pretoria and the National Research Foundation (NRF) of South Africa (Grant No. 76734).http://www.publish.csiro.au/anhj2018Production Animal Studie

Initial blood urea nitrogen concentration predicts subsequent blood urea nitrogen concentration in beef cows

This study was performed to determine whether beef cows have an inherent ability to maintain their relative blood urea nitrogen (BUN) concentration when cattle are exposed to varying levels of dietary nitrogen supplementation. Ten Hereford and 11 Nguni cows, aged between 2 and 16 years, were utilised in two crossover designs. In the first design, cows were exposed to diets containing normal and high crude protein (CP) levels. At the end of the first crossover design, cows received a normal diet for one week before commencement of the second design. In the second crossover design, cows were fed diets containing normal and low CP levels. Blood urea nitrogen concentration was measured 17-21 times (mean = 20) during the study. A linear mixed-effects model was used to assess whether baseline BUN concentration (measured one week before onset of the study) was predictive of subsequent BUN concentration in individual cows. The model was also used to assess whether any of the measured variables were predictive of subsequent BUN concentrations. Baseline BUN concentration was a significant predictor of subsequent BUN concentration in individual cows (P = 0.004). Other variables that were significantly associated with subsequent BUN concentration were breed (P = 0.033), the diet that the cows received before the current treatment (P < 0.001), treatment (P < 0.001) and the week during which sampling was performed (P < 0.001). Beef cattle appear to have an inherent ability to maintain their relative BUN concentration within herds despite changes in levels of dietary nitrogen supplementation.Poster presented at the University of Pretoria, Faculty of Veterinary Science Faculty Day, August 25, 2016, Pretoria, South Africa.ab201

Pre-breeding blood urea nitrogen concentration and reproductive performance of Bonsmara heifers within different management systems

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n= 369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or palpation was performed 4–8 weeks after a 3- month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP, respectively. After stratifying for herd and adjusting for age, heifers with relatively higher prebreeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P=0.011). In the herd with the highest estimated nitrogen intake (n=143), heifers with relatively higher BUN were less likely to become pregnant (P=0.013) and if they did, it was only later during the breeding season (P=0.017), after adjusting for body mass. These associations were not present in the herd (n=106) with the lowest estimated nitrogen intake (P>0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.Faculty of Veterinary Science, University of Pretoriahttp://link.springer.com/journal/112502015-08-31hb201

The effect of blood urea nitrogen on reproductive performance of beef heifers on different levels of nitrogen supplementation

Ruminants have a unique ability to acquire protein from non-protein nitrogen (NPN) sources, and to recycle nitrogen back into the rumen, instead of excreting all of it via the urine, faeces and milk. However, a high concentration of blood urea nitrogen (BUN) has a negative influence on conception. Additionally, a high dietary nitrogen intake poses a challenge to the environment in the form of ammonia emissions, eutrophication and bad odours. This calls for strategies to reduce the environmental impact of livestock production. Variation exists in the ability of cattle to recirculate nitrogen between as well as within cattle breeds. The purpose of this study was to investigate the effects of BUN concentration on reproductive performance in beef heifers under different management systems in South Africa. Serum samples from 369 Bonsmara heifers were taken in November and December 2010 to determine the BUN concentrations prior to the onset of the breeding season. Heifers were from five herds with different levels of protein supplementation during the weeks before the commencement of the breeding season. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at the same time as BUN concentration. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after the three-month breeding season to detect and estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until a heifer was successfully mated. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the effect of BUN concentration on subsequent pregnancy and DTP respectively, while stratifying by herd and adjusting for potential confounders. The correlations between BUN concentration, BCS and RTS were estimated using Spearman’s rho. Pearson correlations were used for the normally distributed variables of age and body mass. BUN concentration was not a significant predictor of pregnancy status but was a significant (P = 0.007) and independent predictor of DTP in heavily and some moderately supplemented herds. As BUN concentration increased, DTP also increased [hazard ratio (HR) = 0.827; 95% CI: 0.721 – 0.949; P = 0.007], while the chance of becoming pregnant decreased, although this was not statistically significant [odds ratio (OR) = 0.882; 95% CI: 0.772 – 1.007; P = 0.063]. Bonsmara heifers with higher BUN concentration, which suggests a better ability to recirculate nitrogen, might be at a disadvantage when the production system includes high levels of RDP supplementation because of this negative impact on reproductive performance. It is proposed that production systems be adapted to avoid selection against animals with an improved ability to recirculate nitrogen.Dissertation (MMedVet)--University of Pretoria, 2013.gm2014Production Animal StudiesUnrestricte

Effect of Temperature and Humidity on Milk Urea Nitrogen Concentration

This study investigated the effect of ambient temperature and humidity on milk urea nitrogen (MUN) concentration in Holstein cows. Meteorological data corresponding to the dates of milk sampling were collected over six years. A linear mixed-effects model including a random effect term for cow identification was used to assess whether temperature and humidity were predictive of MUN concentration. Age, days in milk, temperature humidity index (THI), ration, milk yield, parity and somatic cell count were also evaluated as main effects in the model. A general linear model including all variables as random effects was then fitted to assess the contribution of each variable towards the variability in MUN concentration. Maximum daily temperature and humidity on the sampling day were positively associated with MUN concentration, but their interaction term was negatively associated, indicating that their effects were not independent and additive. Variables that contributed the most to the variability of MUN concentration were dietary crude protein (21%), temperature (18%) and other factors (24%) that were not assessed in the model (error term). Temperature has a significant influence on urea nitrogen concentration and should therefore always be considered when urea nitrogen concentration data are used to make inferences about the dietary management of dairy cows

Occurrence and characterization of seven major Shiga toxin‐producing Escherichia coli serotypes from healthy cattle on cow–calf operations in South Africa

Cattle are a major reservoir of Shiga toxin‐producing Escherichia coli. This study investigated the occurrence of seven major STEC serogroups including O157, O145, O103, O121, O111, O45 and O26 among 578 STEC isolates previously recovered from 559 cattle. The isolates were characterized for serotype and major virulence genes. Polymerase chain reaction revealed that 41.7% (241/578) of isolates belonged to STEC O157, O145, O103, O121, O45 and O26, and 33 distinct serotypes. The 241 isolates corresponded to 16.5% (92/559) of cattle that were STEC positive. The prevalence of cattle that tested positive for at least one of the six serogroups across the five farms was variable ranging from 2.9% to 43.4%. Occurrence rates for individual serogroups were as follows: STEC O26 was found in 10.2% (57/559); O45 in 2.9% (16/559); O145 in 2.5% (14/559); O157 in 1.4% (8/559); O121 in 1.1% (6/559); and O103 in 0.4% (2/559). The following proportions of virulence genes were observed: stx1, 69.3% (167/241); stx2, 96.3% (232/241); eaeA, 7.1% (17/241); ehxA, 92.5% (223/241); and both stx1 and stx2, 62.2% (150/241) of isolates. These findings are evidence that cattle in South Africa carry STEC that belong to six major STEC serogroups commonly incriminated in human disease. However, only a subset of serotypes associated with these serogroups were clinically relevant in human disease. Most STEC isolates carried stx1, stx2 and ehxA but lacked eaeA, a major STEC virulence factor in human disease.The Gauteng Department of Agriculture Rural Development (GDARD) (Grant No. FY 2013/14-A0W907), the National Research Foundation (NRF)-Thuthuka Fund, the University of Pretoria, Institutional Research Theme (IRT)-Animal and Zoonotic Diseases (AZD) (Grant No. UP-AZD IRT A0W596), and the Global Disease Detection (GDD) Program of the Centers for Disease Control and Prevention (CDC) (Grant No. 1U2GGH001874-01).http://wileyonlinelibrary.com/journal/zph2019-11-01hj2019Paraclinical SciencesProduction Animal Studie

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