PubMed Health⌕ Search

Biomedical subjects

D S Buchanan

Publications and source records attributed to D S Buchanan.

47 records · Page 3Linked to original sources
PubMed1985

Selection for increased weaning or yearling weight in Hereford cattle. II. Direct and correlated responses.

Selection was applied from 1964 to 1978 for increased weaning weight (WWL) or yearling weight (YWL) in two Hereford lines. An Angus line was maintained as an unselected control line (CL). Each line was maintained with 50 cows and four sires each year (two sires selected each year and used for 2 yr). Primary traits measured in the lines were birth weight (BW), preweaning daily gain (WDG), weaning weight (WW), weaning conformation grade (WG), weaning condition score (WC), weaning to yearling daily gain (YDG), yearling weight (YW), yearling conformation grade (YG) and yearling condition score (YC). Averaged over two methods, estimated genetic responses/generation (in standard deviation units) in WWL and YWL were: BW, .29, .26; WDG, .17, .15; WW, .22, .19; WG, .19, .26; WC, .12, .12; YDG, -.02, .04; YW, .08, .14; YG, .19, .16; YC, -.13, -.03. The realized heritability estimates were .23 and .15 for WW and YW, respectively. The realized genetic correlation between WW and YW was .69. Progeny from crosses of selected WWL and YWL sires to Angus cows had similar feedlot and carcass performance. At the end of the study, milk yield and composition were similar for mature cows in WWL and YWL.

Animals↗
PubMed1984

Sow productivity comparisons for four breeds of swine: purebred and crossbred litters.

Data were collected from 366 litters produced in a four-breed (Duroc, Yorkshire, Spotted and Landrace) diallel mating system. Purebred and crossbred litters were farrowed during five consecutive (fall and spring) farrowing seasons (fall 1976 through fall 1978). Litters were produced by randomly mating boars of each breed to at least one female of each breed. Litter size and weight at birth, litter size and weight at 42 d and pig survival to 42 d were analyzed. There were significant parity effects for all traits except survival rate, and significant year and season effects for litter size at birth and 42 d and litter weight at 42 d. Large breed of dam differences were detected for most sow productivity traits. Litters from Spotted females were smaller and lighter in weight. Landrace females were most productive in terms of litter weight at weaning and proportion of their pigs raised from birth to weaning. Breed of sire differences were not significant for any trait. Significant heterosis estimates were obtained for litter size and weight at weaning and for survival rate. Crossbred litters had .79 more pigs, were 11.72 kg heavier at weaning and had a 5.56% greater survival rate than the average of all purebreds.

Animals↗
PubMed1984

Reproductive performance for four breeds of swine: crossbred females and purebred and crossbred boars.

Matings and litters were studied involving all three-breed crosses (sired by purebred boars) and four-breed crosses (sired by cross-bred boars) from the Duroc, Yorkshire, Landrace and Spotted breeds. There were 764 female mating records and 161 boars used over five sequential breeding seasons. A sample of pregnant gilts was slaughtered each season and the remainder were allowed to carry their litters to term so that 493 litters resulted. Crossbred and purebred boars and crossbred females were evaluated for their contributions to conception rate (first service and over an 8-wk breeding season), number of services/conception, litter size and weight at birth, 21 and 42 d and survival rate to 21 and 42 d. Crossbred boars had a 17.9% higher first service conception rate, a 5.3% higher breeding season conception rate and performed .11 fewer services/conception compared with purebred boars. There were no significant differences among the boar breeding groups for litter size, weight or survival rate. The six crossbred female groups (reciprocal crosses were combined) did not differ significantly in conception rate or number of services/conception. There were significant differences in litter weight born and differences that approached significance (P less than .10) for litter size at 42 d and litter weight at 21 d. Yorkshire-Landrace females had the largest litters at birth, 21 and 42 d and the heaviest litters at 21 and 42 d. The smallest litters at 21 and 42 d were from Yorkshire-Spotted females, and they also had the lightest weight litters at all three stages.

Animals↗