ABSTRACT Reproductive performance of lactating cows is critically related to their nutritional management during the periparturient period. Five protocols for propylene glycol (PG) with or without glycerol (Gly) treatment were evaluated in dairy Holstein cows. A total of 141 animals received the following treatments as feed supplementation: 1) control group (n=18): no treatment, 2) PG-1 (n=25): 500 ml PG for 10 days before and after calving, 3) PG-2 (n=23): 400 ml PG for 7 days before and after calving, 4) PG-3 (n=37): 300 ml PG for 7 days before and 21 days after calving, 5) PG+Gly-150 (n=12): 150 ml PG+150 ml Gly 21 days before and after calving, 6) PG+Gly-250 (n=26): 250 ml PG+250 ml Gly for 21 days before and after calving. BCS, milk yield, and some reproductive performance parameters were recorded. Blood levels of glucose and progesterone were measured at days 14 and 21 after calving. Results showed that combined treatment (PG+Gly-250) significantly improved BCS on days 30 and 75 postpartum compared to control and other treatment groups. Moreover, reproductive performance of animals in PG+Gly-250 group showed significant shortening in DFH, DFS and DO by 11.39, 12.1 and 51.8 days, respectively compared to non-supplemented animals. Average milk yield was not affected by treatments (p>0.05). At day 14 after calving glucose was significantly high in PG-3 group compared to control (P<0.001). At day 21, glucose remained higher in PG-3 group (55.84±2.86 mg/dl Vs 46.86±2.32 in control) followed by PG+Gly-250 group (49.18±2.58). Progesterone level was significantly high in PG-3 group at days 14 and 21pp (P<0.001) compared to control group. In conclusion, periparturient dietary supplementation of PG and Gly at a dose of 250 ml/day could be recommended to improve reproductive performance in dairy cows.
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