Progesterone milk residues in goats treated with CIDR-G(®) inserts

Progesterone (P4)-impregnated intravaginal controlled internal drug-releasing devices (CIDRs) have been used worldwide for estrus synchronization in ruminants. CIDRs serve to place all treated animals in the luteal phase of the estrous cycle. The objectives of this study were to compare P4 concentrations in milk from normal reproductively cycling, CIDR-treated, and pregnant goats. CIDRs were placed in treatment goats on day 0 and removed on day 19. Milk was collected daily from day 0 to day 21 from control and CIDR-treated goats and for 5 consecutive days between 40 and 60 days of gestation from pregnant does. Milk P4 was plotted against time (in days) for each individual, and the area under the curve (AUC) was calculated as an estimate of total milk P4. The AUC(day 0-21) for control and CIDR-treated goats were 29.5 ± 11.9 and 33.7 ± 6.6 d·ng/mL, respectively (P = 0.77). The highest single-day and highest 5-day average P4 values for each animal were also compared among groups. Single-day peak P4 levels were 4.8 ± 1.5, 4.0 ± 1.0, and 6.0 ± 0.4 ng/mL for control, CIDR-treated, and pregnant goats (P = 0.42). The highest 5-day average P4 concentrations were 3.6 ± 1.3, 2.9 ± 1.8, and 4.2 ± 0.3 for control, CIDR-treated, and pregnant goats (P = 0.56). The results of this study show that intravaginal P4 CIDR devices inserted for 19 days in healthy goats resulted in milk P4 levels similar to or less than those endogenously produced during diestrus or pregnancy.