Biomedical subjects

G A Rohrer

Publications and source records attributed to G A Rohrer.

95 records · Page 6Linked to original sources

PubMed1994

A microsatellite linkage map of the porcine genome.

We report the most extensive genetic linkage map for a livestock species produced to date. We have linked 376 microsatellite (MS) loci with seven restriction fragment length polymorphic loci in a backcross reference population. The 383 markers were placed into 24 linkage groups which span 1997 cM. Seven additional MS did not fall into a linkage group. Linkage groups are assigned to 13 autosomes and the X chromosome (haploid n = 19). This map provides the basis for genetic analysis of quantitative inheritance of phenotypic and physiologic traits in swine.

Animals↗

PubMed1994

Use of direct in situ single-copy (DISC) PCR to physically map five porcine microsatellites.

Direct in situ single-copy polymerase chain reaction (DISC-PCR) was used to assign and orient a linkage group to pig chromosome 1. Five microsatellites were analyzed, and all five were successfully localized using this procedure. Physical data were used to orient the linkage group with respect to the centromere and estimate the amount of coverage of chromosome 1. There was excellent concordance between the physical and linkage maps. The linear order of the microsatellites was identical, and relative distances were similar. All markers were located on the long arm of chromosome 1. Coverage was estimated at about 32%. Thus, DISC-PCR rapidly and easily assigned and ordered microsatellite markers for which large genomic clones do not exist.

Animals↗

PubMed1994

Evaluation of line and breed of cytoplasm effects on performance of purebred Brangus cattle.

Substantial differences between reciprocally crossed Bos taurus x Bos indicus calves for birth, weaning, and yearling weights have been reported. To determine whether cytoplasmic inheritance is responsible for a portion of these differences, field records for birth and weaning weight (n = 7,353) and postweaning average daily gain (n = 2,746) from registered Brangus calves were analyzed. An animal model that included maternal effects was fit for each trait. Breed of cytoplasmic origin was fit as a fixed effect and coded as Angus, Brahman, or unknown. Cytoplasmic line within each breed of origin was treated as a random effect. Variance components for random effects were estimated using derivative-free REML procedures. Line of cytoplasm accounted for less than .002% of the phenotypic variance in all three traits. Estimates for cytoplasmic breed of origin effects were small in magnitude, and contrasts tested (Angus vs Brahman and Angus vs Unknown) were not significant (P > .10). Estimates of heritability of direct (maternal) effects were .36 (.20), .41 (.27), and .21 (.08) for birth weight, weaning weight, and postweaning average daily gain, respectively. Estimates of genetic correlations between direct and maternal effects ranged from -.27 for postweaning average daily gain to -.58 for birth weight. No evidence for breed or line within breed of cytoplasmic origin effects was detected in these data.

Analysis of Variance↗

PubMed1994

Heritabilities and phenotypic and genetic correlations for bovine postrigor calpastatin activity, intramuscular fat content, Warner-Bratzler shear force, retail product yield, and growth rate.

To estimate the heritability (h2) of postrigor calpastatin activity (CA), 555 steers were reared and processed conventionally. Breed-types included purebreds (Angus [A], Braunvieh [B], Charolais [C], Gelbvieh [G], Hereford [H], Limousin [L], Pinzgauer [P], Red Poll [RP], and Simmental [S]), composite populations (MARC I [1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A], MARC II [1/4 S, 1/4 G, 1/4 H, 1/4 A], and MARC III [1/4 RP, 1/4 H, 1/4 P, 1/4 A]), and F1 crosses (H, A, C, G, P, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, or Salers x H or A). Steers were serially slaughtered on an age-constant (across breed groups) basis. Heritability estimates for CA, i.m. fat content (IMF), Warner-Bratzler shear (WBS) force, retail product yield (RPY), and ADG were .65 +/- .19, .93 +/- .02, .53 +/- .15, .45 +/- .18, and .32 +/- .26, respectively. The genetic correlations (rg) of CA with WBS, RPY, and ADG were .50 +/- .22, .44 +/- .25, and -.52 +/- .37, respectively. The rg of IMF with WBS, RPY, and ADG were -.57 +/- .16, -.63 +/- .15, and -.04 +/- .11, respectively. These h2 and rg estimates indicate that it should be possible to select for improvements in CA, IMF, and WBS. However, selection against CA may be a more suitable approach for improving meat tenderness than selection for increased IMF because the level of genetic antagonism between CA and RPY was not as great as that between IMF and RPY.

Adipose Tissue↗

PubMed1988

Productive longevity of first-cross cows produced in a five-breed diallel: I. Reasons for removal.

Data from 498 cows of 15 breed-types produced in a five-breed diallel (reciprocals pooled) including Angus, Brahman, Hereford, Holstein and Jersey were analyzed for differences in productive longevity, mean life span and reasons for removal from the herd over approximately 14 yr. The only culling related to production was of cows that did not give birth to at least one live calf every 24 mo. Otherwise, cows were only removed when they appeared to be incapable of weaning another live calf. The average age at removal, estimated from linear regression, was 3,470 d, with values ranging from 2,174 d (Jersey) to 4,087 d (Angus-Brahman). Longevity of crossbred cows was greater than that of purebred cows (P less than .001). Purebred cows usually had higher initial rates of removal than crossbred cows. Estimates of mean longevity from the nonlinear regression resembled the results of the linear regression analysis; mean life spans ranged from 6.2 yr (Jersey) to 14.6 yr (Angus-Brahman). The major reason for removal of Brahman and Brahman-cross cows was for reproductive reasons. Angus and Angus-cross cows were culled more frequently for structural unsoundness; Hereford cows had a higher incidence of cancer eye, calving difficulty and mammary problems; cows with 100% dairy breeding had exceptionally high susceptibility to diseases and mineral imbalance.

Animals↗