|dc.description.abstract||Cows with an extended interval from calving to first ovulation (post partum period) have increased intervals from calving to conception and are more likely to be culled compared with cows with a short post partum period. Treatment options for cows with an extended post partum period include hormonal and management strategies. Hormonal treatments result in the majority of treated animals displaying oestrus with a subsequent luteal phase of normal duration and improved pregnancy rates compared with untreated controls. Hormonal interventions also tend to have more predictable outcomes compared with management changes, such as manipulating body condition or dietary intakes after calving, and usually have some oestrus synchronization effect, thus facilitating the use of artificial insemination. However, responses to any treatment are variable and are related to those factors that influence duration of the PPI, such as body condition and parity.
In a study on a commercial farm of 700 dairy cows experiencing poor reproductive performance, cows were assigned to two different treatment protocols based on their ovarian function. This was carried out over a 12 month period. Cows with a normal corpus luteum and cystic corpus luteum were assigned to treatment with PGF2α and anoestrus cows and follicular cyst cows were assigned to treatment with GnRH. Success was based on return to oestrus within 6 days with PGF2α treatment and return to oestrus within 25 days with GnRH treatment. 35% of the cows were treated with PGF2α, of which 56% showed return to oestrus within 6 days after the first veterinarian visit. After 2 more subsequent visits, 10% of the initial treatment pool with PGF2α remained open. 39% of the cows were treated with GnRH. Within 25 days, 51% of the cows displayed oestrus. Following two more subsequent visits, again 10% of the non responsive cows remained open after continued GnRH treatment.
The long interval from parturition to first service (123 days), the low rate of oestrus response and poor pregnancy rate (20%) prior to treatment are consonant with inadequate oestrus detection.||en