Dairy cattle characteristically exhibit decreased milk yield and reproductive performance, as well as increased uterine infection rates during periods of high stress. Chromium supplementation has demonstrated efficacy as a feed additive capable of reducing the detrimental effects of stress. As such, its application in dairy production may help to alleviate economic losses associated with seasonal heat stress and the stress experienced during the early postpartum period. Therefore, the objective of the work described in this thesis was to evaluate the potential benefits of short-duration, high-dose chromium (Cr) supplementation in early postpartum dairy cows during the summer months. Multiparous, early postpartum cows (20.95 ± 0.21 DIM, 658.29 ± 13.61 kg) were assigned to one of two treatment groups: 1) normal TMR (Con; n=10) and 2) normal TMR + Cr propionate supplementation (CrPro; 12 mg/h/d Cr; n=12). Body weight (BW), milk yield, and feed intake were measured each day of the experiment. Ambient temperature and humidity were monitored, and the temperature-humidity index (THI) was calculated for the duration of the study as an indicator of the severity of the heat stress experienced by the cows. Transrectal ultrasonography was performed every three days to assess ovarian follicular and luteal dynamics. Respiration rates (RR), rectal temperatures (RT), and blood glucose were recorded concurrently with ovarian ultrasonography. Plasma was collected and used for analysis of progesterone concentrations. Every six days in conjunction with ultrasonography, endometrial cytology samples were collected via cytobrush from each cow to determine the incidences of subclinical endometritis (SCE), as determined by polymorphonuclear leukocyte (PMNL) %. There were no treatment-based differences in RR, RT, blood glucose, feed intake, milk yield, or BW. However, the supplementation strategy did improve reproductive parameters. Within the Con group, there was an increase in PMNL % between samples five and six. Furthermore, at cytology sample six, the Con group had a greater percentage of PMNL than the CrPro group (P=0.01). Chromium consumption did not affect the counts or sizes of most follicles, with the exception being the 6-9 mm category where the CrPro group had a greater average diameter and tended to have more follicles in this category. While CL numbers or size did not differ between treatments, the ratio of progesterone (P4) to corpus luteum (CL) volume was greater in the CrPro group compared to the Con group (P=0.03). The results from this study indicate that the proposed supplementation strategy does not influence DMI or milk yield in cows experiencing stress. Nonetheless, short-duration, high-dose Cr supplementation strategy could benefit reproductive performance and thereby limit economic losses experienced by dairy producers during periods of stress. / Master of Science / Dairy producers continue to experience monetary losses due to the decrease in production performance by dairy cows resulting from physiological changes in response to stress. Elevated ambient temperature and humidity conditions can lead to heat stress, which has been found to decrease both milk and reproductive performance on dairy operations. The period after calving, known as the postpartum period, can also lead to metabolic changes in a cow due to the stress of giving birth and beginning to produce milk. Chromium is an essential trace mineral that can be supplemented with cattle feed to improve the impacts of such stressful periods on production parameters. This study evaluated the effect of a short-duration, high-dose chromium supplementation strategy on reproduction and lactation of early postpartum dairy cattle during summer months. Twenty-two cows were assigned to two treatment groups: control (standard feed only) and chromium supplement (standard feed plus chromium propionate supplementation). Cows receiving the chromium supplement did not experience any changes in respiration rate, rectal temperature, blood glucose levels, feed intake, milk yield, or body weight. Reproductive analyses determined that cows receiving the chromium supplementation had a lower number of immune cells present in the uterus by the end of the experiment, which may be indicative of a healthier uterine environment. Chromium supplemented cows also had a greater level of progesterone concentration to corpus luteum volume compared to cows in the control group. These results indicate that the short-duration, high-dose chromium supplementation strategy could benefit reproductive performance and limit losses experienced by dairy cows under stress conditions.

Forty-eight Holstein cows at Utah State Dairy Farm were blocked statistically according to date of calving, previous milk production, and numbers of lactation at parturition. The cattle were assigned randomly to one of four treatments within blocks. The four treatments included a base ration (control, treatment #1), base ration plus .8% of sodium bicarbonate (treatment #2), base ration plus .4% of magnesium oxide (treatment #3), and base ration plus both .8% of sodium bicarbonate and .4% of magnesium oxide (treatment #4). The research was conducted from February 1983 to November 1984. A formagraph was used to measure milk coagulation parameters and pH was determined. There was no significant difference in milk coagulation parameters or pH between the control and the buffer treatments. Milk parameters were significantly different in individual cow, week, and milk pH. Milk parameters did not appear to be dependent upon season. Curd firmness was significant in interaction of season and treatment. Significant variations in milk pH were observed in relation to week, season, and individual cow. Overall treatments, the clotting time, K20, and pH value increased each week, and A30 decreased each week. The milk parameters and pH in each treatment were significant between weeks except K20 and A30 in treatment #3, and A30 in treatment #2 (p>0.05). The clotting time and K20 were negatively correlated with firmness, and there was positive correlation between Ct and K20 as expected. Somatic cell count was positively correlated with clotting time, K20, and pH and negatively correlated with A30. Milk pH was the most significant and had positive correlation coefficient with clotting time and firming rate and negative correlation coefficient with curd firmness.

The purpose of this study was to determine the influence of diet and physical activity behaviors on weight status and lipid profiles in low-income women in early postpartum. In addition, the relationship of nutrition knowledge with dietary intakes was evaluated. A convenience sample of low-income mothers was recruited from public health clinics, community centers, and doctor's offices. Inclusion criteria was Hispanic, African American, or Caucasian ethnicity; body mass index (BMI) [greater-than or equal to] 25 kg/m², low-income (annual household income <185% federal poverty line); parity<3 and ability to speak and write English. Demographic, dietary (24-hr recalls and 2 day food intake recalls), psychosocial, anthropometric, serum lipids (LDL, HDL and total cholesterol and triglycerides) and physical activity (pedometer steps) data were collected. For study 1, the Healthy Eating Index-2005 (HEI-2005) scores were computed as a measure of diet quality in a sample of 125 women. Analysis of Covariance and linear regression was performed to determine the relationship between HEI-2005 and serum lipids. The mean total index score of the sample was 51.4 and was associated inversely with BMI ([beta]=-0.117), LDL ([beta]=-.659) and total ([beta]=-.690) and positively with HDL ([beta]=.216) (P<0.05). Less than 20% of the sample failed to meet the recommendations for fruits, total vegetables, whole grains and oil and 60% had overconsumption of solid fats, alcohol and added sugars. In study 2, snacking frequency and choices of 134 postpartum women were evaluated. Influence of snacking frequency on HEI-2005 scores and disparities in snack choices by BMI categories was assessed by performing ANCOVA. A majority of the sample (82%) consumed snacks and the most favored snack group was sweets and desserts. Increase in snacking frequency was associated with higher mean total HEI-2005 scores, and total fruit, dark green vegetables and legumes, total grains, and saturated fat (P<0.05) component scores when adjusted for energy intakes. Snacking frequency was also associated with higher intakes of protein, vitamins A and C, and calcium (P<0.05). In study 3, 66 new mothers participated and completed an 8-week weight loss intervention promoting exercise by using pedometers. Paired t test revealed improvement in physical activity after intervention. Linear regression analysis determined the ability of pedometer steps to predict weight loss ([beta]=0.465), % body fat ([beta]=-0.316), triglycerides ([beta]=-0.549), LDL ([beta]=-0.391) and total cholesterol ([beta]=-0.418). In study 4, a nutrition knowledge scale was developed and validated in new mothers. Knowledge was associated with greater consumption of grains, low fat meats and dairy (P<0.01), fiber (p<0.01), calcium (p<0.001), and iron (p<0.05). Participants appeared to be more cognizant of information about vitamins and minerals and weight management and less of energy nutrients and calorie counting. Hierarchical regression model identified age, education, ethnicity and income as determinants of knowledge. / text

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