Biomedical subjects

J V Whiteman

Publications and source records attributed to J V Whiteman.

11 recordsLinked to original sources

PubMed1984

Transmitted effect of purebred versus crossbred rams on rate and variability of lamb growth.

The performance of 457 fall-, 510 winter-and 640 summer-born lambs from several years was examined to compare the progeny of purebred Hampshire (H) or Suffolk (S) and crossbred (S X H or H X S) rams for mean and variability of growth rate. Eight rams (four crossbred and four purebred) were mated to white-faced crossbred ewes each season with a total of 37 rams represented in the study. Individual rams were exposed to approximately 30 ewes each season. Purebred-sired lambs were slightly heavier at birth than crossbred-sired lambs averaged over seasons (P = .10). The differences in birth weight between purebred- and crossbred-sired lambs were .08 kg (P = .28); .15 kg (P = .20) and .13 kg (P = .03) for fall, winter and summer seasons, respectively. For 70-d weight and average daily gain from weaning to market weight (ADG), the differences between purebred- and crossbred-sired lambs were not consistent over seasons. Purebred-sired lambs were 1.62 kg heavier (P = .02) at 70 d of age for the winter season, but were .26 (P = .44) and .27 kg (P = .48) lighter than crossbred-sired lambs for the fall and summer lambing seasons, respectively. Differences in ADG between lambs sired by purebred and crossbred rams were -27 (P = .01), 35 (P = .01) and 5 g/d (P = .28) for fall, winter and summer seasons, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1982

Fertility and prolificacy of crossbred ewes under two cycles of accelerated lambing.

The reproductive performance of 227 crossbred ewes representing five combinations of Finnsheep (F), Dorset (D) and Rambouillet (R) breeding was evaluated under two cycles of accelerated lambing, with lambing every 8 mo. The five breed combinations represented were: 1/2D 1/2R, 1/4D 3/4R, 1/4F 1/2D 1/4R, 1/4F 1/4D 1/2R and 1/4F 3/4R. The ewes were 4 and 5 yr old when put on the accelerated lambing program. Ewes were mated to yearling Hampshire, Suffolk, HxS or SxH crossbred rams each season. Each cycle was made up of three breeding seasons: winter (January-February), fall (September-October) and late spring (May-June). Reproductive performance averaged over the two cycles showed reduced fertility to May-June breeding (47.8%), compared to January-February breeding (91.8%) and September-October breeding (90.6%; P less than .05). During May-June breeding, 1/2D 1/2R ewes were more fertile (P less than .05) than 1/4D 3/4R or any 1/4F ewe groups. During the winter and fall breeding seasons, ewe fertility averaged 91.5% and was similar for ewes exposed to purebred and crossbred rams. In the late spring the use of crossbred rams resulted in 62.4% conception compared with 41.0% from the use of purebred rams (P less than .05). Prolificacy of the ewes averaged 1.67 lambs during winter, 1.80 lambs during fall and 1.35 lambs during later spring. The 1/4F ewe groups produced .10 and .16 more lambs/lambing (P less than .05) than 1/2D 1/2R and 1/4D and 3/4R ewes, respectively.

Animals↗

PubMed1982

Repeatability of lambing rate.

Repeatability of number of lambs born using the life-time records on 263 crossbred ewes produced in 1971 and 1972 were estimated by the intraclass correlation method and by the regression of subsequent lamb production on number of lambs born alive at the first and second lambings. The ewes were of Finnsheep (F), Dorset (D) and Rambouillet (R) breeding and first lambed at 1 yr of age. Five breed combinations were represented 1/2D 1/2R 1/4R 3/4R, 1/4F 1/2D 1/4R, 1/4F 1/4D 1/2R and 1/4F 3/4R. Ewes were bred to yearling Hampshire, Suffolk or reciprocal cross rams at varied intervals in the course of study. The repeatability of number of lambs born estimated by intraclass correlation was .138 +/- .067. Repeatability of number of lambs born estimated by the regression of subsequent lamb production on initial lambing rate was .121 +/- .025 lambs/ewe season and that estimated by the regression of subsequent lamb production on second lambing rate was .046 +/- .020 lambs/ewe season. Ewes producing twins at their first lambing subsequently produced an average of .11 more lambs/lambing than ewes producing singles and ewes producing singles subsequently produced an average of .16 more lambs/lambing than ewes than produced no lambs. Differences between these lambing classes at the second lambing were small (.05 and .06). The first lambing at 1 yr of age was a much better predictor of the ewes' lifetime lambing rate.

Animals↗

PubMed1982

Lamb growth patterns following different seasons of birth.

Fall-, winter- and summer-born lambs were compared for birth weight, 70-d weight and avg daily gain (ADG); 70-d to market). Data were collected on 457, 510 and 640 lambs born during the fall (October, November), summer (June, July) and winter (January, March), respectively. Similarly bred lambs born during the different seasons varied in birth weight (P less than or equal to .01) and for 70-d weight (P congruent to .07). Large year-within-season variation for post-weaning gain contributed to inconclusive results for seasonal effects. Winter- and summer-born lambs were 1.28 and .95 kg heavier (P less than .05) at birth than were fall-born lambs, respectively. Winter-born lambs were 2.93 and 3.79 kg heavier (P congruent to .1) at 70-d of age than fall- and summer-born lambs, respectively. An interaction between sex and season was observed for ADG (P less than .01). There was a smaller average difference (40 g/d) between ram and ewe lambs born in the summer than between ram and ewe lambs (90 g/d) born in the fall and winter. Results suggest that differences in birth weight and 70-d weight existed between fall-, winter- and summer-born lambs under conditions where lambs were creep fed the same diet and ewes were well fed. Sex and birth (birth-rearing) type adjustment factors appeared to be similar among seasons for birth weight and 70-d weight. Only the adjustment of ADG for sex appeared to depend on the season of birth of the lamb.

Animals↗

PubMed1973