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.