ELISA detection of restriction site polymorphisms in the pig ryanodine receptor locus.

We compare two strategies for ELISA detection of restriction site polymorphisms (EDRSP) that are suitable for high-throughput genotyping of the pig ryanodine receptor point mutation (RYR1(hal)). In both procedures, target DNA is amplified by PCR with one primer that is 5' biotinylated and a second primer that is 5' fluoresceinylated. PCR products are captured in duplicate wells on a streptavidin-coated, 96-well plate. The duplicates may be treated in two ways. In a single restriction enzyme assay, one duplicate is exposed to a restriction enzyme that cuts one allele specifically, and the second duplicate is exposed to no restriction enzyme. In a dual restriction enzyme assay, the second replicate is exposed to a second restriction enzyme that cuts the alternate allele specifically. Thereafter, the two procedures are similar; anti-fluorescein antibodies conjugated to peroxidase are allowed to bind to the fluoresceinylated ends, the plate is washed, and a substrate is converted to a colored end product. The ratio of the absorbances in the two wells is used to classify subjects by genotype. When the dual restriction enzyme assay is run, three genotype groups are easily distinguishable. When the single restriction enzyme assay is run, heterozygotes generate values that may overlap with those of the homozygotes that are not cut by the restriction enzyme. Dual restriction enzyme assays are more accurate than single restriction enzyme assays; however, single restriction enzyme assays are sufficient for identifying pigs that carry RYR1(hal).

Effect of the estrogen receptor locus on reproduction and production traits in four commercial pig lines.

We investigated the effect of the estrogen receptor (ESR) gene on growth and reproductive traits in four Large White-based commercial pig lines. A total of 9,015 litter records from 4,262 sows genotyped at the ESR locus were analyzed to determine whether ESR influenced total number born (TNB) or number born alive (NBA). Teat number (TN), test ADG, ADFI, feed:gain ratio (F/G), and ultrasonic backfat (BF) were also analyzed to determine effects of ESR. The TNB and NBA were increased per favorable allele of ESR (P < .01) with additive effects of .42 (.31) and .39 (.31) pigs/litter in the first parity (later parities), respectively. Dominance effects were near zero in parity one, but they were .16 and .14 pigs for TNB and NBA, respectively, in later parities (P < .05). A favorable additive pleiotropic effect was detected for BF (P < .001; -.11 mm per copy of the favorable litter size allele). There were no detectable effects on ADG or F/G (P > .10), although ADF was reduced 18 g/d per copy of the favorable litter size allele (P < .05). Average TN was 13.1 for pigs carrying the favorable litter size allele vs 13.2 for noncarriers (P < .05). Marker-assisted selection using ESR is warranted to increase litter size in the Large White-based lines considered here and will be of considerable economic value to pork producers.

Ten generations of selection for predicted weight of testes in swine: direct response and correlated response in body weight, backfat, age at puberty, and ovulation rate.

Selection for predicted weight of testes at 150 d of age (PWT) was practiced for 10 generations to determine the effect on reproductive and growth traits in swine. Mass selection among boars (line TS) or random selection (line C) was practiced beginning with the F3 generation of a Large White x Landrace composite population. Population size in each line was 40 to 45 litters by 15 sires per generation. Responses were estimated by regressions on cumulative selection differentials for PWT and on generation number and by mixed-model derivative-free REML procedures. The realized heritability of PWT was .35 +/- .02 and the response per generation was 19 g (P < .01). Correlated responses in body weight were .95 +/- .37 (140 d) and 1.13 +/- .42 kg (160 d) per generation for boars and .70 +/- .32 (130 d) and .64 +/- .46 kg (180 d) per generation for gilts. Response in backfat was .08 +/- .14 mm per generation in boars and .16 +/- .14 mm in gilts. Negative genetic trends occurred in age at puberty in both lines, but the difference between lines was not significant. At Generation 10, ovulation rate was .76 +/- .43 eggs more for gilts of the TS line than for C gilts. Genetic correlations of PWT with other traits are presented. Heritability of PWT was moderately high and its phenotypic variance was large; therefore, a high rate of response of 5.5% per generation occurred. Selection for PWT was not effective in decreasing age at puberty or increasing ovulation rate of daughters.

Effect of unilateral hysterectomy and ovariectomy on puberty, uterine size and embryo development in swine.

Eighty crossbred gilts were assigned randomly to treatments: 1) removal of an ovary and ipsilateral uterine horn (UHO) at 130 d of age and removal of the remaining ovary and uterine horn 12 d post-puberty; 2) UHO at 130 d of age, mated and reproductive tracts recovered when slaughtered at 30 d of gestation; 3) UHO 12 d post-puberty, mated and slaughtered at 30 d of gestation and 4) unoperated controls that were mated and slaughtered at 30 d of gestation. Age of puberty was not affected by treatments. Gilts in treatment 1 had a mean ovulation rate at the pubertal estrus comparable to gilts in treatment 3. But, gilts in treatments 2 and 3 had 16% fewer (P less than .01) corpora lutea at 30 d of gestation than control gilts. Length and weight of the remaining uterine horn at 12 d post-puberty for gilts treated at 130 d of age were similar to the averages of gilts left intact. Gilts with one uterine horn had 2.2 fewer live embryos at 30 d of gestation than control gilts (P less than .01). But, the proportion of corpora lutea represented by live embryos did not differ significantly among treatments. Gilts with one uterine horn had 1.1 fewer live embryos (P less than .15) after adjustment for number of corpora lutea, less uterine space occupied by each embryo (P less than .01) and less total placental membrane per embryo (P less than .05) than control gilts.(ABSTRACT TRUNCATED AT 250 WORDS)