Genetic and economic benefits of selection based on performance recording and genotyping in lower tiers of multi-tiered sheep breeding schemes

Table 2 Ewe age structure in different tiers of the breeding scheme supporting the commercial tier

Age of ewes (years)	Proportions of ewe age groups in the flock (ρ _s=f)			Probability of ewe survival to age group i given presence in age group 2 (a _i)	Probability of a ewe dying or being culled at age i (d _i)	Prolificacy by age group (Lrp_i)
Age of ewes (years)	Nucl	Mult	Comm	Comm	Comm	Comm
1^a	0.09	0.00	0.00	1.00	0.00	0.80
2	0.32	0.35	0.30	1.00	0.23	1.49
3	0.25	0.23	0.23	0.77	0.10	1.65
4	0.18	0.18	0.20	0.67	0.17	1.65
5	0.14	0.13	0.15	0.50	0.17	1.65
6	0.01	0.09	0.10	0.33	0.28	1.65
7	0.00	0.02	0.02	0.06	0.05	1.65

Nucl is the nucleus tier of the breeding scheme, Mult is the multiplier tier and Comm is the commercial tier
^aThis refers to the proportion of ewes mated in the first year of age as ewe lambs

ISSN: 1297-9686