Data from the Montana State University Targhee flock were used to estimate genetic and environmental relationships between lamb BW and adult ewe BW, condition score, and prolificacy. The flock was managed under commercial western range conditions typical of the area. Data included records from 12,154 lambs born to 2,930 dams and 200 rams between 1960 and 2005. Lamb traits included BW at birth and approximately 45 d, 120 d (weaning), 12 mo, and 18 mo of age and fleece characteristics at 12 mo of age. Adult traits included ewe litter size; BW and BCS at weaning, in late gestation, and in early lactation; and adult fleece measurements. Multiplicative factors were used to adjust (pre)weaning lamb BW for effects of age of dam, type of birth and rearing, and lamb sex and to adjust adult litter sizes for effects of ewe age. An animal model was used to estimate genetic relationships. Models for lamb traits included fixed effects of year of birth and, for postweaning data, lamb sex and random additive genetic effects and, for (pre)weaning BW, additive genetic maternal and permanent environmental maternal effects. Models for adult traits included fixed effects of year of birth, year of record, and, when appropriate, numbers of lambs born or born and reared and random additive genetic and animal permanent environmental effects. Heritability estimates for lamb birth weight, 45-d BW, weaning weight, yearling weight, 18-mo BW, fleece weight, staple length, and spinning count were 0.19, 0.07, 0.12, 0.32, 0.38, 0.32, 0.31, and 0.25, respectively. Maternal heritabilities for lamb birth, 45-d, and weaning weights were 0.15, 0.09, and 0.08, respectively. Heritability estimates for adult traits were 0.12 for litter size, averaged 0.43 for BW and 0.13 for body condition, and were 0.44, 0.37, and 0.25 for adult fleece weight, staple length, and spinning count, respectively. Correlations between genetic effects on adult BW and direct and maternal genetic effects on lamb BW ranged from 0.21 to 0.96 (P < 0.05) and 0.29 to 0.53 (P < 0.05), respectively, with residual correlations ranging from 0.05 to 0.95. Correlations of lamb traits with adult body condition and number of lambs born were generally not different from zero; genetic and residual correlations ranged from -0.52 to 0.69 and -0.39 to 0.31, respectively.

Breeding objectives were developed for Targhee sheep under rangeland production conditions. Traits considered were those for which EPD were available from the US National Sheep Improvement Program and included direct and maternal effects on 120-d weaning weight (WW and MM, respectively); yearling weight (YW); yearling fleece weight, fiber diameter, and staple length; and percent lamb crop (PLC), measured as the number of lambs born per 100 ewes lambing. A bioeconomic model was used to predict the effects of a change of 1 additive SD in EPD for each trait, holding all other traits constant at their mean, on animal performance, feed requirements, feed costs, and economic returns. Resulting economic weightings were then used to derive selection indexes. Indexes were derived separately for 3 prolificacy levels (1.41, 1.55, and 1.70 lambs/ewe lambing), 2 triplet survival levels (50 and 67%), 2 lamb pricing policies (with or without discounting of prices for heavy feeder lambs), and 3 forage cost scenarios (renting pasture, purchasing hay, or reducing flock size to accommodate increased nutrient requirements for production). Increasing PLC generally had the largest impact on profitability, although an increase in WW was equally important, with low feed costs and no discounting of prices for heavy feeder lambs. Increases in PLC were recommended at all 3 prolificacy levels, but with low triplet survival the value of increasing PLC eventually declined as the mean litter size increased to approximately 2.15 lambs/ewe lambing and above. Increasing YW (independent of WW) increased ewe maintenance costs and reduced profitability. Predicted changes in breeding values for WW and YW under index selection varied with lamb pricing policy and feed costs. With low feed costs or no discounts for heavy lambs, YW increased at a modest rate in association with increasing WW, but with high feed costs or discounting of heavy lambs, genetic trends in WW were reduced by approximately 50% to constrain increases in YW. Changes in EPD for MM or fleece traits generally had smaller effects on profitability than changes in PLC, WW, and YW. Two indexes designed to address current rangeland production conditions (low forage costs and discounting of heavy feeder lambs) or more intensive and integrated production with retained ownership and value-based marketing of lambs (higher forage costs and no discounting of heavy lambs) were anticipated to meet the needs of most Targhee producers.

Procedures for continuous adjustment of lamb birth and weaning weights for effects of ewe age were developed using 18 747 birth and 13 139 weaning weight records of Polypay sheep enrolled in the US National Sheep Improvement Program. Changes in birth and weaning weights across ewe age groups were modelled using hybrid curves that combined asymptotic regression models to describe initial increases in lamb weight as ewes moved into adulthood with secondorder polynomials to describe declines in lamb weights in older ewes. Lamb birth and weaning weights were highest (and the asymptotic and polynomial forms comprising the hybrid curves intersected) at ewe ages of 76 and 52 months, respectively. Across all ewe ages, hybrid curves were superior to second-and third-order polynomials in goodness of fi t, producing a parabolic form with a fl at top and different decay rates on either side of the ewe ages corresponding to maximum lamb weights. Fourth-and fi fth-degree polynomials were equivalent to hybrid curves in goodness of fi t, but generally did not produce reasonable predictions for the oldest ewes. Adjustment factors derived from the hybrid curve predicted that lamb birth weight would increase from 76% of maximum in 11-month-old ewes to 90 and 96% of maximum in respectively, and then decline to 97% of maximum at 105 months. For weaning weight, 83, 95, 99, and 93% of maximum lamb weight were attained at ewe ages of 11, 24, 36, and 105 months, respectively. Resulting multiplicative adjustment factors avoid discontinuities at boundaries between ewe age categories and are particularly useful in accelerated or other multiple-season lambing systems.

Records from 2,525 adult Targhee ewes and 10,099 lambs were used to estimate genetic parameters in an animal model for ewe stayability (STAY), productive life (PL), adult BW (AW) and BCS, fleece characteristics, and number of lambs born (NLB) and for lamb BW at birth and approximately 45 d, 120 d (120W; weaning), 12 mo, and 18 mo of age. Stayabilities were analyzed as overall stayability (STAYn|2), which indicated presence or absence of a ewe at n yr of age, given that she was present at 2 yr of age, or marginal stayability (STAYn|n-1) recording the presence of a ewe at n yr of age, given that she was present in the previous year. Productive life was measured as the age of ewe in years at her last lambing. Lamb BW were corrected for age at weighing; BW taken at or before weaning were adjusted for effects of type of birth and rearing, age of dam, and sex using National Sheep Improvement Program methods. The NLB was likewise adjusted for effects of ewe age before analysis. Birth year was included as a fixed effect for all traits. Year of record and, for AW and CS, the number of lambs born or born and reared were also included in models for adult traits. Models for all traits included random additive genetic and residual effects. Random maternal genetic and dam permanent environmental effects were also included in the model for lamb (pre)weaning BW, and random permanent environmental effects of the ewe were included in models for adult traits. The heritability estimate for PL was 0.05 (P < 0.10). Additive variance in STAY was only present after 5 yr of age (P < 0.05), with estimated heritabilities ranging from 0.04 to 0.10. Phenotypic correlations between STAY and other traits were near zero, ranging from -0.07 to 0.14. Estimates of genetic correlations of STAY5|4 and STAY6|2 with maternal genetic effects on 120W were positive (both 0.46; P < 0.05), suggesting that STAY and maternal effects on 120W both reflect genetic variation in ewe fitness characteristics. Genetic correlations between STAY5|4 and 120W, AW, and NLB were not different from zero (0.06, 0.13, and -0.06, respectively; P > 0.10). However, genetic correlations between STAY6|2 and 120W, AW, and NLB were all negative, with values of -0.17, -0.32 (P < 0.05), and -0.03, respectively, indicating a possible small antagonism between STAY and genetic effects on body size.

Broiler breeding programs rely on crossbreeding. With genomic selection, widespread use of crossbred performance in breeding programs comes within reach. Commercial crossbreds, however, may have unknown pedigrees and their genomes may include DNA from 2 to 4 different breeds. Our aim was, for a broiler dataset with a limited number of sires having both purebred and crossbred offspring generated using natural mating, to rapidly derive parentage, assess the distribution of the sire contribution to the offspring generation, and to assess breed-of-origin of alleles in crossbreds. The dataset contained genotypes for 56,075 SNPs for 5,882 purebred and 10,943 3-way crossbred offspring generated by natural mating of 164 purebred sires to 1,016 purebred and 1,386 F1 crossbred hens. Using our algorithm FindParents, joint parentage derivation for the offspring and parent generations required only 1 m 29 s to retrieve parentage for 20,253 animals considering 4,504 possible parents. FindParents was similarly accurate as a maximum likelihood based method, apart from situations where settings of FindParents did not match the genotyping error rate in the data. Numbers of offspring per sire had a very skewed distribution, ranging from 1 to 270 crossbreds and 1 to 154 purebreds. Derivation of breed-of-origin of alleles relied on phasing all genotypes, including 8,205, 372, and 720 animals from the 3 pure lines involved, and allocating haplotypes in the crossbreds to purebred lines based on observed frequencies in the purebred lines. Breed-of-origin could be derived for 96.94% of the alleles of the 1,386 F1 crossbred hens and for 91.88% of the alleles of the 10,943 3-way crossbred offspring, of which 49.49% to the sire line. The achieved percentage of assignment to the sire line was sufficient to proceed with subsequent analyses requiring only the breed-of-origin of the paternal alleles to be known. Although required number of animals may be population dependent, to increase the total percentage of assigned alleles, it seems advisable to use at least approx. 1,000 genotyped purebred animals for each of the lines involved.