Synchronisation Programs for Heifers
RememberBecause of the synchrony achieved with these programs, returns to service are also batched closely over only a few days. A rate of 5% bulls (1 per 20 heifers) should be sufficient in most cases until round 2 is completed. The additional bulls that are to be used over the milking herd after AI, could be used on the heifers for the first 3 weeks to overcome this problem.
CIDR Programs for heifers
Controlled Internal Drug Release (CIDR) devices slowly release progesterone when placed in the vagina. They produce a tight synchrony and are easy to administer.CIDRs delay the maturation of follicles by maintaining high progesterone levels for a period of 8 to 10 days. When the progesterone is removed follicle development resumes and ovulation follows 24 to 72 hours later.
| Day 0 | CIDR and capsule in all heifers. |
| Day 6 | PG all heifers (2 dose - 2.5ml) |
| Day 8 | (pm) Remove all CIDRs and tail paint. |
| Day 9 | Observe and AI. Very few will cycle |
| Day 10-11 | Observe and AI (most heifers will cycle on these days). |
Prostaglandin programs for heifers
Prostaglandins are the most commonly used drug in synchrony programs today. The ability to remove the corpus luteum between days 5 and 16 of the oestrus cycle provides the opportunity to influence the onset of oestrus of 75 per cent of cycling heifers with one treatment.A number of different programs are used to synchronise maiden heifer heats.
Double PG program
This traditional program involves treatment of heifers twice at an eleven day interval. The first treatment will bring all heifers into the 5 to 16 day period by the time of the second treatment.
In practice, 90 percent of heifers cycle within the period 2 to 5 days past 2nd treatment.
| Day 0 | PG all heifers |
| Day 11 | PG all heifers and tail paint |
| Day 12-16 | Observe and AI (most heifers will cycle on days 13-14) |
Five day AI - PG program
This program takes advantage of the five day non response period early in the cycle. By submitting heifers to AI in the first 5 days, all heifers not mated by 5 days will be between days 6 and 21 of their cycle. Treatment of this group with PG will result in all responsive heifers on heat in the subsequent 2 to 5 days.
About 75% of heifers will be treated with PG in this program. Up to 10 days of observation and AI are required to achieve high submission rates.
| Day 1 | Tail Paint and AI |
| Days 2-4 | AI |
| Day 5 | AI, PG all heifers not yet mated. |
| Days 6-10 | AI |
PG - AI Program
This program reduces the number of days of observation and AI to 5 however at a cost to submission rate.
Heifers between days 1 and 5 of their cycle will not respond to PG so will not come on heat in the ensuing 5 days.
| Day 1. | AI all heifers on heat, tail paint and PG others |
| Day 2-6. | Observe and AI. |
Comparative Costs of Programs (1998 prices)
| Program | Cost/animal treated | Cost/50 heifers | No. Days AI |
| Double PG | $8 | $400 | 3 |
| 5 day AI -PG | $4 | $150 (75% treated) | 10 |
| CIDR-PG | $15 | $750 | 2 |