INTERPRETIVE SUMMARY: SUPPLEMENTATION WITH RUMEN-PROTECTED CAPSICUM DURING THE TRANSITION PERIOD IMPROVES METABOLIC STATUS OF DAIRY COWS

In ruminants, it has been observed that capsicum oleoresin can alter insulin responses and high-intensity artificial sweetener can increase glucose absorption from the small intestine. Since glucose metabolism and insulin responses are critical during early lactation, these supplements might have an effect on metabolic status. The objective of this experiment was to evaluate the effects of rumen-protected capsicum (RPCap) oleoresin fed alone or in combination with artificial sweetener during the transition period on lactational performance and susceptibility to sub-clinical ketosis in dairy cows. Fifteen primiparous and 30 multiparous Holstein cows were arranged in a randomized complete block design during days -21 to 60 of lactation. Cows within block were randomly assigned to one of the following treatments (15 cows/treatment): no supplement (CON), supplementation with 100 mg/cow/d RPCap, or RPCap plus 2 g/cow/d of high-intensity artificial sweetener (RPCapS). For both RPCap and RPCapS groups of cows, only RPCap was fed during the dry period. From d 8 to 11 of lactation, intake was limited to 70% of predicted dry matter intake to induce sub-clinical ketosis. Production variables were recorded daily, and blood samples were collected on wk -1, 1, 2, 4, and 8 of the lactation periods for analysis of metabolic hormones and blood chemistry. Supplementation with RPCap increased insulin and decreased ß-hydroxybutyrate pre-calving, indicating a decrease in lipolysis. During the lactation period, RPCap was associated with increased milk production and efficiency in multiparous cows only. In primiparous cows, blood insulin remained elevated in RPCap during the lactation period, but this was not accompanied by changes in blood glucose, milk yield, body condition score, or body weight. Supplementation with RPCapS eliminated the positive response to RPCap in multiparous cows and it prevented the increase in blood insulin in primiparous cows. In addition, multiparous cows receiving RPCapS produced less milk than CON or RPCap cows after the ketosis challenge. All cows developed sub-clinical ketosis during the challenge, and this was not affected by treatment. We conclude that treatment did not decrease susceptibility to sub-clinical ketosis; however, RPCap was effective at improving energy status pre-calving in both primiparous and multi-parous cows, and increased milk production in multiparous cows. The mechanism underlying these responses is unclear.