[Synchronization of ovulation (OVSYNCH) in high producing dairy cattle herds. Part II: Milk yield, diseases and cost-benefit-analysis].

A method for synchronization of ovulation (OVSYNCH) was evaluated for its practical use in seven North German dairy cattle herds. The original procedure of PURSLEY et al. (1995) was applied, i. e. cows were treated with Gonadotropin Releasing Hormone (GnRH) at a random stage of the estrous cycle, followed by an injection of a prostaglandin F2alpha (PGF2alpha)-analog seven days later and another injection of GnRH two days after PGF2alpha. Cows were inseminated 24 h after the last injection by artificial insemination. Control animals were assigned by corresponding lactation number and month of lactation. Cows from the OVSYNCH group returned to the conventional reproductive management after the OVSYNCH treatment, which was the same management as that for the control group. The parameters of fertility and correlations between body condition score (BCS) as well as concentrations of serum progesterone and the success of OVSYNCH were presented in the first report. For the OVSYNCH group, the 100-day-duction during the time period from calving until a pregnancy was established differed markedly from healthy cows in a variety of parameters. Healthy cows had a greater FSC (65.22%) than sick cows (35.90%) (P < 0.05). Furthermore, mean days open were less in healthy cows than in sick cows (85.48 +/- 30.56 days vs 110.85 +/- 46.40 days) (P < 0.05). Cows showing a disease had a higher number of lactation (4.00 +/- 2.26 vs. 2.80 +/- 1.35; P < 0.01) and a decreased BCS (2.72 +/- 0.23 vs. 2.91 +/- 0.23; P < 0.05). Sick and healthy cows from the OVSYNCH group did not differ with regard to 100-day-milk-yield (milk kg, relative and absolute milk fat and protein content). The cost-benefit-analysis revealed higher total cost, and cost per pregnancy (16,408.07 euros and 278.10 euros, respectively) in the control group than in the OVSYNCH group (11,015.69 euros and 196.71 euros, respectively).