Suboptimal reproductive performance leads to extended days open, increased culling due to reproductive failure, and decreased milk yield. Many factors influence the reproductive and productive performance of dairy herds, consequently, profitability. Choosing the most effective reproductive protocol for a given herd is a critical managerial decision.
Two aspects were assessed:
- The economic outcome of reproductive programs using estrus detection, Ovsynch, or a combination of both.
- The impact of improving 10 percentage points (from 85 percent to 95 percent) in both compliance and the accuracy of ED on the timing to reach the new level of pregnancy and milk yield.
The following reproductive programs were evaluated:
- Estrus detection only.
- Presynch-Ovsynch: Presynch-Ovsynch for first AI, and Ovsynch for resynchronization of open cows at 32 days after AI.
- Presynch-Ovsynch-estrus detection: same as previous protocol for first AI, but cows undergo estrus detection and AI after first AI, and cows not re-inseminated by 32 days after AI or diagnosed open 32 days after AI are resynchronized using Ovsynch.
Cows did not receive AI after 365 days in milk (DIM) and open cows were culled after 450 DIM.
Culled cows were immediately replaced with a bred heifer that was 280-days pregnant. Herd was maintained at 1,000 cows (lactating and dry). Death losses were set at 6 percent and abortion at 11.3 percent. Dry period was 60 days.
Net daily value was calculated by subtracting the costs with replacement heifers ($1,800 per heifer), feeding costs ($0.25 per kilogram of lactating cow diet; $0.25/kilograms of dry cow diet), breeding costs ($0.1 per cow per day for estrus detection; $2.5 per dose Prostaglandin F2alpha; (PGF); $3 per dose gonadotrophin releasing hormone (GnRH); $0.17 per injection administration), and other costs ($3.5 per day) from the daily income with milk sales ($0.31 per kilogram of milk), cow sales ($0.75 per kilogram of live weight), and calf sales ($200 per calf). Simulation was performed until steady-state was reached (3,000 days), then average daily values for the subsequent 2,000 days was used to calculate profit per cow per year.
First AI conception rate (CR) was set to 30 percent (decreased by 2.5 percent for every subsequent AI), and ED was set to 60 percent. Accuracy of estrus detection (95 or 85 percent), and compliance with each injection (95 or 85 percent) were evaluated. Inaccurate estrus detection resulted in 0 percent CR. Missing a Presynch injection resulted in loss of 50 percent of the benefit (40 percent increase to first AI), and missing an Ovsynch injection resulted in a decrease in CR by 70 percent.