Induction of Lactation in Holstein Cows Using Progesterone Injections or Progesterone Vaginal Inserts

The aim of this study was to evaluate the effect of replacing progesterone injections by progesterone vagi-nal inserts on productive and reproductive parameters of lactating cows with reproductive problems after prolonged periods of heat stress. Fifteen Holstein cows were randomly assigned to one of three treatments: 1) treated with two progesterone vaginal inserts (P4-INS); 2) treated with progesterone and estradiol via injections (P4-INJ) and 3) control, cows with gestation and parturition normally. All cows were subjected to a Presynch-Co-Synch timed artificial insemination protocol and then inseminated at 71 d in milk. Concen-tration of P4 in (P4-INS) and (P4-INJ) cows during the first 7 d of induction of lactation was similar (P > 0.05) and then increased linearly in both groups. Adjusted milk yield, total milk yield, and average daily milk yield were similar (P > 0.05) in treated cows, but cows from (P4-INJ) group produced less milk (P < 0.05) than control cows. Days in milk and peak milk yield were similar (P > 0.05) among all groups. Per-centage of milk fat and protein, as well as days to peak milk yield were higher (P < 0.05) in both treated groups compared to control. Body condition score, service per conception, conception to first service, total conception, days open and culling rate at the end of lactation were similar (P > 0.05) among treatments. Pro-gesterone administration by injection or by vaginal insertion resulted in similar production and reproduction parameters of dairy cattle with induced lactation.