Rumen effects of monensin in dry cow diets varying in energy density.

Controversy has existed as to whether monensin will provide equal or differential benefits in a higher-energy, lower-roughage close-up diet versus a higher-roughage, lower-energy diet. Our objective was to determine the rumen effects of a controlled-energy, high-fiber diet balanced to meet but not greatly exceed energy requirements during the dry period or a traditional 2-group approach of higher-energy close-up diet. The effects of added monensin in each diet type were determined. Multiparous Holstein cows (n = 17) were fitted surgically with ruminal cannulas. During the first 4 wk of the dry period, all cows were fed a controlled-energy, high-fiber diet (CE) as a total mixed ration for ad libitum intake. During the last 3 wk before calving, half of the cows were switched to a higher-energy, close-up diet until calving (CU), whereas the other half continued to receive the CE diet. Within each dietary group, half of the cows received monensin (MON) supplementation in the diet (24.2 g/t of total dry matter) and half did not (CON). After calving, all cows received the same lactation diet containing monensin (15.4 g/t of dietary dry matter). At 14 d prepartum, dry matter intake was not different across treatments. The weight of rumen contents was greater for cows fed CE. Rumen liquid dilution rate, solids passage rate, pH, total volatile fatty acid (VFA) concentrations, molar proportions of acetate and propionate, and papillae length did not differ among diets. Butyrate percentage tended to be greater for cows fed CE. Postpartum, dry matter intake, mass of rumen contents, solids passage rate, pH, total VFA concentration, molar percentages of propionate and butyrate, and papillae length did not differ among treatments. Liquid dilution rate (16.6, 10.7, 16.0, and 18.2%/h for CE + CON, CE + MON, CU + CON, and CU + MON, respectively) was affected by a diet × monensin interaction. Cows on the CE + CON diet had a greater ruminal proportion of acetate than did cows fed CU + CON, whereas cows fed monensin on either diet were intermediate (diet × monensin interaction). Addition of MON to the CU diet decreased the proportion of propionate (diet × monensin interaction). Cows fed CE had greater mass of rumen contents before parturtition but the high inclusion of wheat straw in the CE diet did not negatively affect rumen papillae length. Monensin inclusion differentially affected liquid passage rate and VFA concentrations.

Effects of prepartum diets varying in dietary energy density and monensin on early-lactation performance in dairy cows.

Our objectives were to evaluate the effects of prepartum monensin supplementation and dry-period nutritional strategy on the postpartum productive performance of cows fed monensin during lactation. A total of 102 Holstein cows were enrolled in the experiment (32 primiparous and 70 multiparous). The study was a completely randomized design, with randomization restricted to balance for parity, body condition score, and expected calving date. A 2 × 2 factorial arrangement of prepartum treatments was used; the variables of interest were prepartum feeding strategy [controlled-energy diet throughout the dry period (CE) vs. controlled-energy diet from dry-off to 22 d before expected parturition, followed by a moderate-energy close-up diet from d 21 before expected parturition through parturition (CU)] and prepartum monensin supplementation [0 g/t (control, CON) or 24.2 g/t (MON); Rumensin; Elanco Animal Health, Greenfield, IN]. Lactation diets before and after the dry period contained monensin at 15.4 g/t. During the close-up period, cows fed CU had greater DM and NEL intakes than cows fed CE. Calf BW at birth tended to be greater for cows fed CU than for those fed CE but was not affected by MON supplementation. Diet did not affect calving difficulty score, but cows supplemented with MON had an increased calving difficulty score. We found a tendency for a MON × parity interaction for colostral IgG concentration, such that multiparous MON cows tended to have lower IgG concentration than CON cows, but colostral IgG concentration for primiparous MON and CON cows did not differ. Postpartum milk yield did not differ between diets but tended to be greater for cows supplemented with MON. Milk fat and lactose content were greater for cows fed CU than for those fed CE, and lactose content and yield were increased for cows supplemented with MON. Solids-corrected and fat-corrected milk yields were increased by MON supplementation, but were not affected by diet. Overall means for postpartum DMI did not differ by diet or MON supplementation. The CU diet decreased the concentration of nonesterified fatty acids during the close-up period but increased it postpartum. Neither diet nor monensin affected ß-hydroxybutyrate or liver composition. Overall, postpartum productive performance differed little between prepartum dietary strategies, but cows fed MON had greater energy-corrected milk production. In herds fed monensin during lactation, monensin should also be fed during the dry period.

Comparison of prepartum low-energy or high-energy diets with a 2-diet far-off and close-up strategy for multiparous and primiparous cows.

Previous research demonstrated that nutrition during the far-off (early) dry period may be as important to transition success as nutrition during the close-up dry period. Our objectives were to determine if a low-energy, high-fiber diet fed throughout the dry period improved metabolic status and production of dairy cows compared with a higher-energy diet or a 2-diet system, and to compare responses of cows and heifers to those diets. Holstein cows (n = 25 with 10 primiparous per treatment) were assigned to each of 3 diets at 60 d before expected calving. Treatment LO [40.5% wheat straw; 5.6 MJ of net energy for lactation (NEL)/kg of DM] was designed to meet but not exceed National Research Council recommendations for ad libitum intake from dry-off until calving. Treatment HI was a high-energy diet (6.7 MJ of NEL/kg of DM) fed for ad libitum intake from dry-off until calving. For the LO+HI treatment, the LO diet was fed ad libitum from dry-off until 21 d before expected calving, followed by the HI diet until parturition. After parturition all cows were fed a lactation diet (7.0 MJ of NEL/kg of DM) through 63 d postpartum. Dry matter intake and body weight were greater for HI cows prepartum, but not postpartum. When LO+HI cows were switched to the HI diet, their dry matter intake increased to match that of HI cows. Cows fed HI had greater gain of body condition before calving but lost more postpartum. Energy balance postpartum was higher for LO cows than for HI cows. Milk production, protein content, and protein yield did not differ among diets. Milk fat content and yield were highest for HI cows, lowest for LO, and intermediate for LO+HI cows. The HI cows had lower serum nonesterified fatty acids prepartum than either LO or LO+HI, but greater concentrations postpartum. Serum ß-hydroxybutyrate did not differ prepartum, but was greater for HI than for LO or LO+HI postpartum. Serum glucose and insulin were lower for LO than HI and LO+HI prepartum; insulin was lower for LO and HI than for LO+HI postpartum. The LO cows had lower liver total lipid concentration postpartum than the HI cows and LO+HI cows. Primiparous cows generally responded to diets the same as multiparous cows. The LO+HI feeding strategy provided no benefit over the LO diet. Moreover, the high-energy diet, even when fed for only 19 d before calving in the LO+HI group, resulted in increased serum ß-hydroxybutyrate and liver total lipid concentrations compared with LO.

Visceral adipose tissue mass in nonlactating dairy cows fed diets differing in energy density(1).

Our objective was to determine dietary energy effects on feed intake, internal fat deposition, body condition score (BCS), visceral organ mass, and blood analytes in Holstein cows. Eighteen nonpregnant, nonlactating cows (BCS = 3.04 ± 0.25) were blocked based on initial BCS and were randomly assigned within each block to 2 treatments. Treatments were either high energy [HE; net energy for lactation (NEL)=1.62 Mcal/kg] or low energy (LE; NEL = 1.35 Mcal/kg) diets fed as total mixed rations for 8 wk. The LE diet consisted of 81.7% forage, including 40.5% wheat straw and 28.3% corn silage, whereas the HE diet contained 73.8% forage with no straw and 49.9% corn silage (dry matter basis). Cows were fed for ad libitum intake once daily at 0800 h. Feed intake was recorded daily, blood was sampled at wk 1, 4, and 7, and BCS was assigned at wk 1, 4, and 7. Cows were killed following the 8-wk period, and visceral organs, mammary gland, and internal adipose tissues were weighed and sampled. The HE group had greater dry matter intake (15.9 vs. 11.2 ± 0.5 kg/d) and energy intakes than cows fed LE, but neutral detergent fiber intake did not differ (5.8 vs. 5.6 ± 0.25 kg/d for HE and LE). Final body weight was greater for cows fed HE (807 vs. 750 kg), but BCS did not differ between groups (3.52 vs. 3.47 for HE and LE). Omental (26.8 vs. 15.2 ± 1.6 kg/d), mesenteric (21.5 vs. 11.2 ± 1.9 kg), and perirenal (8.9 vs. 5.4 ± 0.9 kg) adipose tissue masses were larger in HE cows than in LE cows. Although subcutaneous adipose mass was not measured, carcass weight (including hide and subcutaneous fat) did not differ between HE (511 kg) and LE (496 kg). Liver weight tended to be greater for cows fed HE, but weights of gastrointestinal tract, heart, and kidney did not differ. Serum insulin tended to be greater and the glucose to insulin ratio was lower for cows fed HE. Serum concentrations of ß-hydroxybutyrate and cholesterol were greater for HE cows than for LE cows but concentrations of glucose, nonesterified fatty acids, total protein, and albumin did not differ. Final BCS was correlated with masses of omental (r = 0.57), mesenteric (r = 0.59), and perirenal (r = 0.72) adipose tissue, but mesenteric adipose mass increased more as BCS increased for cows fed HE. The similar final BCS between HE and LE cows demonstrates that BCS may lack sensitivity to detect differences in visceral fat deposition that might increase risk for peripartal diseases and disorders.

How medical students and residents describe the roles and characteristics of their influential clinical teachers.

PURPOSE: This study sought to identify students' perceptions about characteristics of faculty who had positively influenced their clinical education and to determine whether the students' perceptions matched those published for residents. METHOD: On exit surveys in 1997 and 1998, students graduating from Baylor College of Medicine were asked to list clinical faculty who had "significantly and positively influenced their clinical education" and to describe that influence. Using codes derived from Ullian's earlier 1994 study regarding residents' perceptions, the authors classified 1,153 written descriptions that expressed a single characteristic or teacher attribute into five roles: person, physician, supervisor, teacher, and unspecified (global). For each role, categories expressing similar characteristics were grouped into clusters. Although one author coded all descriptions, interrater reliability (.93) was determined by having an assistant code a set of randomly selected descriptions. RESULTS: The medical students ranked characteristics of the teacher role highest. In contrast, Ullian's residents ranked characteristics of the supervisor role highest. CONCLUSION: Medical students and residents differ substantially in their perceptions of the roles and characteristics of their influential clinical teachers. The results in this study corroborate Stritter's learning vector theory. Thus, learners' perceptions of the value of their teachers' behaviors change during their professional development. These perceptual changes may explain why medical students and residents assess the same faculty's teaching very differently. These results also support the need to prepare clinical faculty differently for working with medical students as compared with residents.

Development of a measure of medical faculty attitudes toward clinical evaluation of students.

PURPOSE: This research involved the development, and in particular the evaluation of the reliability, of scales to measure medical faculty attitudes toward clinical evaluation (ACE) of medical students. The intent was to create measures that yield reliable data and have practical utility in medical education research and faculty development. METHOD: A systematic, eight-step scale development protocol was used to create the instrument. In early 1993 factor analysis was used on data from 217 clinical faculty at four medical schools to refine the measures. Internal consistency and test-retest reliability analyses were performed. Analyses were also done to determine whether the attitude scores were influenced by such faculty demographic attributes as employing medical school, gender, age, tenure track status, academic rank, or academic department. RESULTS: An initial pool of 52 items was reduced to 30 items based on iterative reliability studies. Factor analysis on the 30 items yielded two scales: (1) Quality of Evaluation Procedures, 12 items, alpha = .81; and (2) Content of Departmental Evaluations, eight items, alpha = .85. Test-retest reliabilities (12 weeks) for the scales were .67 and .74, respectively. Faculty demographics did not influence attitudes about the quality of evaluation procedures. However, family physicians showed a slightly more positive attitude toward the content of departmental evaluations than did physicians in five other medical specialties. CONCLUSION: The goal of developing reliable measures of faculty attitudes toward clinical evaluation of medical students has been achieved. With baseline reliabilities established, future research should assess the validity and utility of the scales, especially in the context of clinical practice examinations.

Ratings of students' performances in a third-year internal medicine clerkship: a comparison between problem-based and lecture-based curricula.

PURPOSE: To compare clinical performances in a third-year medicine clerkship between studies from a problem-based learning (PBL) curriculum and students from a traditional, lecture-based learning (LBL) curriculum. METHOD: The study participants were 88 PBL students and 364 LBL students rotating through a common third-year internal medicine clerkship at the Bowman Gray School of Medicine at Wake Forest University, classes of 1991-1995. Faculty and housestaff assessed the students' performances using four clinical rating scales. The student also completed the medicine student ("shelf") test of the National Board of Medical Examiners (NBME). RESULTS: On average, the PBL students received significantly higher ratings from housestaff and faculty on all four rating scales. No difference in scores on the NBME medicine shelf test was observed. CONCLUSION: The results support the hypothesis that preclinical PBL curricula as found at the Bowman Gray School of Medicine may enhance third-year students' clinical performances.

Are medical students ready to provide HIV-prevention counseling?

PURPOSE: To determine whether medical students were prepared to assess risk and counsel patients about prevention of HIV infection, and whether HIV-related experience produced better knowledge and counseling skills. METHOD: In 1995, students at four North Carolina medical schools interviewed a standardized patient portraying a young woman concerned about HIV infection. The standardized patient recorded whether students asked risk-behavior questions and provided risk-reduction advice. A 21-item questionnaire assessed the students' knowledge of HIV testing and prevention. Students indicated whether they had had experience in educational settings related to HIV or STDs. RESULTS: 415 students completed both the patient interview and the questionnaire. Many failed to ask the patient about several HIV-risk behaviors. Although nearly all (98%) inquired about condom use, fewer than two thirds asked about the patient's history of STDs, number of sexual partners, or specific sexual practices. Most students advised the patient to use condoms. The average score on the knowledge test was 79%; 70% of students confused anonymous with confidential testing, more than half overestimated the risk of HIV transmission from a needle stick, and nearly one in ten did not know how to use a condom. Educational exposures did not produce significantly better risk assessment, counseling information, or knowledge scores. CONCLUSION: A majority of experienced medical students did not assess several important risk factors of a patient concerned about HIV infection, and many would have provided incorrect information related to HIV testing and prevention of infection. Patient contact in traditional clinical settings did not influence prevention knowledge or behavior. More innovative methods are needed to train students in HIV-infection prevention and counseling.

A comparison between students in problem-based and traditional curricula at the same medical school: preparing for the NBME Part I.

Eighteen of 22 students in a problem-based curriculum and 62 of 79 students in a traditional curriculum at the same medical school completed a survey 10 weeks after completing Part I of the National Boards. The survey asked students to report the average time they had spent each week during the first 2 years of medical school preparing for the Part I examination. Students were also asked to rate the usefulness of a variety of learning resources. The purpose of the survey was to compare the preparation activities of students in the two curricula. The results of the survey revealed that students in the problem-based curriculum tended to study many more hours for Part I than did students in the traditional curriculum, especially during their second year. The results also found problem-based curriculum students tended to rate textbooks and the PreTest Series as more valuable than did their peers in the traditional curriculum. The effects of the format and goals of the two curricula on the students' preparation activities are explored.

Scoring the objective structured clinical examination using a microcomputer.

The objective structured clinical examination (OSCE) is being used increasingly to assess students' clinical competence in a variety of controlled settings. The OSCE consists of multiple stations composed of a variety of clinically relevant problems (e.g. examining simulated patients, diagnosing X-rays, etc.) Generally, three types of performance data are collected: answers to multiple choice or true/false questions, written short answers, and performance check-lists completed by observers. In most OSCEs these student performance measures are scored by hand. This is time-consuming, increases the probability of mistakes and reduces the amount of data available for analysis. This paper describes a method of computer scoring OSCEs with over 100 students using statistical and test-scoring software regularly used for multiple choice examinations. During the examination, students, markers and raters code answers and performance data directly on optical mark-sheets which are read into the computer using an optical mark reader. The resultant computer data can be efficiently scored and rescored, grouped into different types of subscales, weighted to reflect questions' relative importance, and easily printed in a variety of report formats.

Is it worth it? A look at the costs and benefits of an OSCE for second-year medical students.

For the past two years, the Bowman Gray School of Medicine has used an Objective Structured Clinical Exam (OSCE) to measure the performance of 117 first- and second-year medical students at the end of introductory courses on differential and physical diagnosis. Given the surprisingly high costs of conducting the OSCE ($1300 for supplies and 527 person-hours of donated time), data about the format's perceived benefits were collected. All of the faculty involved in the examination who responded to a questionnaire (80%) reported that it was worth the time they had volunteered to evaluate students by observation and that the format should be used in the future. The majority of student examinees also reported that the OSCE format was appropriate for the course and should continue to be used.