Most of the long-term genetic gain from optimum-contribution selection can be realised with restrictions imposed during optimisation

Table 2 Output parameters that provide insight into the mechanisms underlying optimum-contribution selection (OCS) with restrictions

Breeding scheme	Penalty	∆G _short	∆F _short	L _short	nSires _short
Unrestricted OCS	50	109 ± 9.7	114 ± 27.0	4.1 ± 0.04	13.3 ± 1.19
Truncated dams	50	109 ± 9.6	132 ± 45.7	4.1 ± 0.04	12.8 ± 1.10
Dams unknown	100	102 ± 7.6	87 ± 30.2	4.2 ± 0.04	23.4 ± 1.72
One chance OCS of sires	50	106 ± 8.7	95 ± 22.2	3.8 ± 0.01	17.6 ± 1.25
Pre-selection of sires 25%	50	108 ± 10.2	137 ± 51.0	4.1 ± 0.04	12.7 ± 1.08
Pre-selection of sires 10%	100	103 ± 8.0	88 ± 26.9	4.1 ± 0.03	20.0 ± 2.03
Pre-selection of sires 5%	100	107 ± 10.5	105 ± 31.1	4.0 ± 0.03	17.9 ± 2.07
Pre-selection of sires 1%	200	111 ± 10.7	192 ± 60.8	3.9 ± 0.03	11.7 ± 1.69
Pre-selection of sires 0.5%	5000	110 ± 10.6	268 ± 85.2	3.9 ± 0.04	7.3 ± 0.70
Sire multiples 5	50	108 ± 10.2	139 ± 50.6	4.1 ± 0.05	11.9 ± 1.04
Sire multiples 10	50	108 ± 9.7	137 ± 43.3	4.1 ± 0.05	10.8 ± 0.77
Sire multiples 20	50	107 ± 12.1	134 ± 52.0	4.1 ± 0.05	8.9 ± 0.58
Sire multiples 50	50	104 ± 11.1	148 ± 51.4	4.0 ± 0.06	5.5 ± 0.21
Sire multiples 100	50	95 ± 12.2	172 ± 55.9	4.0 ± 0.07	3.0 ± 0.00
Offspring unknown	50	106 ± 15.1	189 ± 76.1	4.3 ± 0.05	9.7 ± 1.11
Multiple restrictions	50	108 ± 8.5	102 ± 24.4	3.8 ± 0.03	13.6 ± 0.80
Truncation selection 10		112 ± 10.0	413 ± 161.1	4.1 ± 0.03	10

Breeding scheme applying OCS without restrictions is Unrestricted OCS. All other schemes applied OCS with restrictions, except Truncation selection 10, which is a conventional scheme with truncation selection. The output parameters are penalty on average relationship that maximised long-term rate of genetic gain, short-term rates of genetic gain and inbreeding (∆G_short, ∆F_short), short-term generation interval (L_short), and short-term number of sires with allocated matings per selection time (nSires_short), where short and long-term refer to generations 6 to 8 and generations 23 to 25 (approximately). The rates of genetic gain and inbreeding, generation intervals, and numbers of sires are presented as means ± s.d. of 100 simulation replicates. Rates of genetic gain and inbreeding were scaled by setting to 100 the long-term rates of genetic gain and inbreeding realised by Unrestricted OCS at penalty 50. Rate of genetic gain at 100 is equivalent to 0.215 genetic-standard deviations per time and approximately 0.9 genetic-standard deviations per generation. Rate of inbreeding at 100 is equivalent to 0.0020 per time and approximately 0.008 per generation on the observed scale.

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