The Prolific Flock Index

The question

In an intensive system with several lambings a year, one extra lamb per ewe per year changes the whole budget. Which ewes bring that extra lamb without losing the rest?

The concept

The Prolific Flock Index keeps the structure of the Flock Index and shifts the emphasis toward litter size. As Sires › Indexes shows: gain 50–100 (direct) 19%, number born in later lambings 15%, 50-day weight (direct) 14%, 50-day weight (maternal) 10%, number born at first lambing 9%, lambing interval 6%, total weaning weight at first and at later lambings 6% each, lamb survival (maternal) 4%, birth weight (direct) 4%, lamb survival (direct) 4% and birth weight (maternal) 4%.

Compared with the Flock Index, litter size goes from 9% to 24% of the emphasis and total weaning weight doubles. Growth stays close to a third so prolific ewes still raise saleable lambs.

Why it matters

Prolificacy has a low heritability (0.10 in the evaluation), so progress is slow and needs many records. Putting it into an index with growth and survival lets you push it without accepting weaker lambs.

Where you see it

Every ranking panel on the Dashboard offers Prolific Flock in its index selector. The profile shows "Prolific Flock 1.07 · P90 · 94% of its weights". The Sires page labels it as the third index in the head-to-head table.

Decisions it supports

Choosing the maternal line for accelerated systems (three lambings in two years, continuous lambing) and the mating objective "Prolific" in the mating matrix.

Limitations

More lambs born is only useful if they survive and are weaned; the Prolific Flock Index keeps survival in, but at 8% total. Watch the lambing statistics (stillborn, deaths 0–10 days) when you select hard on prolificacy. For a ewe without first-lambing records the index is partial.