Is hemp (Cannabis sativa) safe to feed pregnant sheep?

Cannabis sativa (varieties for industrial use or animal feed are termed hemp), and its extracted byproducts are being considered for animal feed due to their high protein content. However, if hemp disrupts fertility and reproduction in livestock, it should not be used as a feed source. We hypothesized that the phytocannabinoids in hemp would disrupt fertility and reproduction, cause craniofacial defects (cyclops, cleft palate, misshapen head), and low birth weight in lambs. To test this hypothesis, 22 timed pregnant ewes were dosed with hemp in the form of dried ground hemp plant material at 150 mg/kg body weight per day total cannabinoids, and from gestational days 10 to 20 and a separate 22 timed pregnant ewes were dosed similarly with dried ground grass hay as a control. The most prevalent cannabinoids in the plant material were cannabidiolic acid (CBDA) at a concentration of 23.2 mg/g, and cannabidiol (CBD) at a concentration of 5.8 mg/g. Delta 9-tetrahydrocannabidiol was present in the plant material at a concentration of 0.3 mg/g. The hemp used in this study had crude protein concentrations of 15.6%, neutral detergent fiber concentrations of 42.2%, and in vitro true digestibility concentrations of 83.6%. After 10 d of dosing with hemp, a serum sample was obtained from each of the ewes, CBDA was measured at a concentration of 652 ± 38 ng/mL and CBD was measured at 16 ± 0.9 ng/mL. THC was not detected in the serum. The average gestation length for lambs from the hemp treated ewes was 148 ± 0.38 d, and the average gestation length for lambs from the grass hay treated ewes was 149 ± 0.38 d (P = 0.23). The numbers of male and female lambs did not significantly vary from expected (50:50) (P = 0.32). There were no significant fetal deformities (P > 0.05) or weight differences between the treatment groups (P > 0.05), and as expected, the lamb weights significantly increased over time (P < 0.05). These results suggest that Cannabis sativa may have the potential with further research to be a suitable protein source for gestating sheep.