Biomedical subjects

K E Gregory

Publications and source records attributed to K E Gregory.

At least 91 records · Page 5Linked to original sources

PubMed1985

Heterosis retained in advanced generations of crosses among Angus and Hereford cattle.

Data from 1,909 purebred, F1, backcross and F2 and F3 inter se combinations of Angus and Hereford were used to estimate average individual, maternal and grandmaternal genetic effects, individual and maternal heterosis, dominance and epistatic genetic effects. Models for evaluating heterosis and epistatic or recombination effects were discussed. Average individual effects indicate that Angus, compared with Hereford, had calves that were born earlier, had lighter birth weights, lower pre- and postweaning gains and lower pregnancy rates. Angus also produced lighter weight carcasses with more fat cover and marbling. Maternal effects of Angus were in the direction of reduced birth weight, greater calving ease, higher preweaning but lower postweaning growth rate and increased fatness when contrasted with Hereford. There was a tendency for opposite direction of maternal and grandmaternal effects for traits influenced by preweaning maternal environment. When additive X additive effects were ignored, total heterosis was significant for earlier day born, heavier birth weight, preweaning and postweaning gain, and heavier and fatter carcasses. Heterosis retained in F3 inter se vs F1 generation crosses indicated that net epistatic effects were relatively negligible for date of calving, birth weight, weaning gain and fat cover. There was a greater reduction of heterosis effects than expected from dominance alone for survival, pregnancy and marbling score. Loss of heterosis in F3 was less than expected for postweaning gain, carcass weight and rib eye area. Except for survival, pregnancy and marbling, these deviations from dominance expectations, or lack of them, are favorable for F3 composite populations.

Animals↗

PubMed1985

Characterization of breeds of Bos indicus and Bos taurus cattle for maternal and individual traits.

Angus, Boran and Red Poll sires were mated to Ankole, Boran and small East African Zebu (Zebu) females to produce the cows characterized in this study, which produced calves by Friesian, Brown Swiss, Simmental, Boran and Red Poll sires. Individual traits included cow parturition weight, cow weight at weaning, cow mean weight and cow weight change from parturition to weaning; maternal traits included calf crop born percentage, preweaning viability percentage, overall viability percentage, birth weight, weaning weight, weight at 12, 18 and 24 mo and calf weight weaned per cow exposed to breeding (productivity index). Cows by Angus and Red Poll sires significantly exceeded cows by Boran sires (all cows in this comparison had Ankole and Zebu dams) in weaning weight of progeny and in cow weight at parturition and at weaning. Cows by Red Poll sires significantly exceeded cows by Boran sires in birth weight of progeny. Progeny of cows by Boran sires significantly exceeded progeny of cows by Angus and Red Poll sires in 24-mo weight. Cows by Angus and Red Poll sires did not differ (P greater than .05) in any of the traits analyzed. Cows with Ankole and Boran dams significantly exceeded cows with Zebu dams (all cows in this comparison had Angus and Red Poll sires) in progeny weight at birth, 18 mo and 24 mo and in cow weight at parturition and at weaning. Cows with Boran dams significantly exceeded cows with Zebu dams in weaning and 12-mo weight of progeny and significantly exceeded cows with Ankole dams in weaning weight of progeny. The significantly heavier weaning weight and significantly lighter 24-mo weight of the 3/4 Bos taurus progeny of cows with Angus and Red Poll sires relative to the 1/2 Bos taurus progeny of cows with Boran sires suggest that cattle that are 1/2 Bos taurus breed composition have greater general adaptation than cattle with 3/4 Bos taurus breed composition in the postweaning nutritive and climatic environment under which this experiment was conducted. Significantly heavier weights of Angus and Red Poll crossbred cows relative to Boran crossbred cows (all breeds crossed on Ankole and Zebu cows) indicate that the two Bos taurus breeds exceed the Boran (Bos indicus) breed in additive direct genetic effects for size when they have general adaptation to the environment.

Acclimatization↗

PubMed1985

Heterosis and breed effects on maternal and individual traits of Bos indicus breeds of cattle.

Data were analyzed to estimate the effects of heterosis and breed on a series of maternal and individual traits. Crossbred cows were Boran X Ankole and Boran X Zebu; straight-bred cows were Ankole, Boran and Small East African Zebu (Zebu). Cows of all breed groups were mated to Friesian, Brown Swiss and Simmental sires to produce crossbred progeny. While not generally significant, the average effects of heterosis of both crosses for the traits analyzed were: calf crop born, 7.0%; preweaning viability, 7.2%; overall viability, 7.3%; birth weight, 6.0%; weaning weight, 5.4%; 12-mo weight, 4.2%; 18-mo weight, 3.7%; 24-mo weight, 3.6%; calf weight weaned per cow exposed to breeding (cow productivity index), 24.5%; cow parturition weight, 3.5%; cow weaning weight, 4.2% and cow mean weight, 4.0%. Boran cows weaned 31.8 kg (48.0%) more (P less than .05) calf weight per cow exposed to breeding than Ankole cows. Boran cows were generally superior to Zebu cows in progeny weights at all ages (P less than .01). Boran cows weaned 34.5 kg (54.3%) more (P less than .05) calf weight per cow exposed to breeding than Zebu cows. Boran cows weighed an average of 70.8 kg more (P less than .01) than Zebu cows. Although progeny of Ankole dams were heavier (P less than .05) than the progeny of Zebu dams at all ages, the two breeds did not differ (P greater than .05) in calf weight weaned per cow exposed to breeding. Mean weight of Ankole cows was 75.8 kg heavier (P less than .01) than mean weight of Zebu cows.

Analysis of Variance↗

PubMed1985

Comparison of Bos taurus-Bos indicus breed crosses with straightbred Bos indicus breeds of cattle for maternal and individual traits.

Data were analyzed to compare crossbred females produced by crossing exotic Angus and Red Poll males to indigenous Ankole, Boran and Small East African Zebu (Zebu) females with straightbred females of the Ankole, Boran and Zebu breeds at the Ruhengere Field Station in the Ankole District of Southwestern Uganda. Progeny of the straightbred and crossbred dams were by Friesian, Brown Swiss and Simmental sires. Crossbred exotic X indigenous dams were favored over straightbred indigenous dams by 13.7% (P less than .01) in calf birth weight and by 14.8% (P less than .01) in calf weaning weight. Cross-bred cows exceeded (P less than .01) straightbred cows by 61.9% (48.5 kg) in calf weight weaned per cow exposed to breeding. Crossbred cows weighed 37, 46 and 42 kg more (P less than .01) than straightbred cows at parturition, weaning and cow mean weight, respectively. Angus X Boran and Red Poll X Boran crossbred dams were compared specifically with straightbred Boran dams. Exotic (Angus, Red Poll) X Boran crossbred dams exceeded straightbred Boran dams by 27.0% (P less than .05) in calf crop born, by 8.3% (P less than .05) in progeny birth weight and by 14.7% (P less than .01) in progeny weaning weight. Weight of calf weaned per cow exposed to breeding favored (P less than .01) the Angus X Boran and Red Poll X Boran crossbred dams over the straightbred Boran dams by 50.5% (50 kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗

PubMed1984

Crossbreeding cattle in beef production programmes in Kenya. I. Comparison of purebred Boran and Boran crossed with the Charolais, Ayrshire and Santa Gertrudis breeds.

Data collected on a privately owned ranch located in the Machakos District of Kenya at approximately 2 degrees latitude south of the equator at an elevation varying from 1,675 to 2,000 m were analysed on five breed groups of cows: (1) purebred Boran, (2) 1/2 Charolais-1/2 Boran (1/2 C-1/2 B), (3) 3/4 Boran-1/4 Charolais (3/4 B-1/4 C), (4) 1/2 Ayrshire-1/2 Boran (1/2 A-1/2 B) and (5) 1/2 Santa Gertrudis-1/2 Boran (1/2 SG-1/2 B). The maternal traits evaluated included age at first calving, calving interval, calf weight at weaning and cow productivity index (calf weight weaned annually per cow calving). Mean cow productivity index for all cows was 192 kg; for purebred Boran, 174 kg; for 1/2 C-1/2 B, 200 kg; for 3/4 B-1/4 C, 191 kg; for 1/2 A-1/2 B, 210 kg; and for 1/2 SG-1/2 B, 185 kg. Cow breed groups 1/2 C-1/2 B, 3/4 B-1/4 C, 1/2 A-1/2 B and 1/2 SG-1/2 B exceeded (P less than 0.01) purebred Boran by 14.9, 9.8, 20.7 and 6.3%, respectively, in cow productivity index.

Analysis of Variance↗

PubMed1984

Crossbreeding cattle in beef production programmes in Kenya. II. Comparison of purebred Boran and Boran crossed with the Red Poll and Santa Gertrudis breeds.

Two series of breed group comparisons for maternal traits were conducted at one location in Kenya. Data were collected on breed group series I for three years (Boran, 1/2 Red Poll-1/2 Boran (1/2 RP-1/2 B), 1/3 Red Poll-2/3 Boran (1/3 RP-2/3 B) and 2/3 Red Poll-1/3 Boran (2/3 RP-1/3 B) and on breed group series II for five years (Boran, 1/2 Santa Gertrudis-1/2 Boran (1/2 SG-1/2 B) and 1/2 Red Poll-1/2 Boran (1/2 RP-1/2 B]. The advantage in calf weight weaned per year per cow calving of 15.4% for the mean of three Red Poll-Boran crossbred groups over the purebred Boran in breed group series I can probably be accounted for by maternal heterosis. Thus the Red Poll breed probably does not exceed the Boran breed in additive maternal genetic effects in the environment where these data were collected. But the results suggest that the Red Poll breed exceeds the Boran breed in additive direct genetic effects for size while the Boran breed exceeds the Red Poll breed in additive maternal genetic effects as expressed by calf weight weaned per year per cow calving. Breed group series II comparisons show the Boran and the 1/2 SG-1/2 B breed groups do not differ (P greater than 0.05) in calf weight weaned per year per cow calving. The 1/2 SG-1/2 B breed group has maximum expected maternal heterosis; thus, it is indicated that the Boran breed exceeds the Santa Gertrudis breed in additive maternal genetic effects but the Santa Gertrudis breed exceeds the Boran breed in additive direct genetic effects for size.

Analysis of Variance↗

PubMed1984

Characterization of biological types of cattle (cycle III). IV. Postweaning growth and feed efficiency.

Postweaning growth and feed efficiency data were analyzed on 769 F1 crossbred steers out of Angus and Hereford dams and sired by Pinzgauer, Tarentaise, Brahman, Sahiwal, Hereford and Angus sires. Breed groups were fed in replicated pens and slaughtered serially at three different dates in each of 2 yr. Quadratic regressions of pen mean weight on days fed and of cumulative metabolizable energy consumption (ME) on days fed were used to estimate gain, ME consumption and efficiency (Mcal ME/kg gain) over time (0 to 213 d on feed) and weight (250 to 470 kg) intervals, and from d 0 to a small degree of marbling (corresponds to USDA low Choice quality grade) and an 18.9% fat trim end point. Brahman-sired crosses were significantly heavier at weaning than all other breed groups. However, during the postweaning period, which included winter months, and while being fed a moderately high concentrate diet, average daily gain of Brahman-sired crosses tended to be less than Angus- or Hereford-, Tarentaise- and Pinzgauer-sired crosses and that of Sahiwal-sired crosses was significantly less than all other breed groups. Differences among breed groups were not significant for feed efficiency in the time constant interval from 0 to 213 d. In a weight interval from 250 to 470 kg, only Sahiwal-sired crosses differed significantly, requiring more Mcal ME/kg gain than other breed groups. Hereford-Angus crosses were more efficient than all other breed groups (P less than .05) to the marbling end point and to the 18.9% fat trim end point, primarily because of fewer days on feed and thus less net energy required for maintenance. Pinzgauer-sired crosses were significantly more efficient than Tarentaise-, Brahman- and Sahiwal-sired crosses to the marbling end point (P less than .05).

Adipose Tissue↗

PubMed1983

Effects of late castration, zeranol and breed group on growth, feed efficiency and carcass characteristics of late maturing bovine males.

A total of 280 young bulls representing five breed groups with an average age of about 1 yr were assigned to five experimental treatments as follows: (1) emasculator castration at d 0, (2) surgical castration at d 0, (3) intact, (4) intact and implanted at d 0 and 70 with 36 mg of zeranol and (5) intact and implanted at d 0 with 72 mg zeranol. All animals were slaughtered and carcass data were collected after a feeding period of 141 d. Method of castration did not affect rate of gain. Intact males not implanted with zeranol gained 38.6% more (P less than .01) during the 141 d period than castrate males. Intact males from the two zeranol implant treatment groups did not differ from each other in gain, but averaged 11.1% more (P less than .01) during the 141 d period than males from the intact treatment group not implanted. Castrate males required 40.4% more (P less than .01) metabolizable energy (ME) and dry matter (DM)/kg gain than intact males not implanted, but intact males implanted with zeranol did not require less (P greater than .05) ME or DM/kg gain than intact males not implanted. Males castrated at about 1 yr showed a progressive decrease in secondary sex characteristics during the 141 d feeding period, while males from the three intact treatments showed a progressive increase. Zeranol did not have an effect on testicular weight or on aggressive male behavioral characteristics. Castrate males had greater (P less than .01) fat thickness at 12th rib, higher (P less than .01) marbling score and lower (P less than .01) cutability and retail product percentage than the males from the three intact treatments, which did not differ (P greater than .05) from each other in traits associated with carcass composition. The effect of treatment on lean color score, though significant, was not of major importance; all treatments produced meat of acceptable color. The longissimus muscle of castrate males had a finer texture (P less than .01) than longissimus muscle from males from intact treatments, which did not differ from each other (P greater than .05).

Adipose Tissue↗

PubMed1982

Production characters of the Sahiwal and Ayrshire breeds and their crosses in Kenya.

Data were analysed for lactation character of Ayrshire, Ayrshire x Sahiwal, Sahiwal x Ayrshire and Sahiwal females and on survival and growth characters of progeny of Ayrshire, Sahiwal, Simmental and Mixed breed sires mated to these females in the temperate highlands ecological zone of Kenya. The Ayrshire females had significantly higher total lactation yield than the other breeding groups; however, the Ayrshire females received preferential treatment. Despite this the Sahiwal-Ayrshire crosses were superior (3.8%) to the Ayrshire females in productivity index per cow per year because of a shorter calving internal and a higher level of calf survival. Sahiwal females had significantly lower total lactation yield than Ayrshire and Sahiwal x Ayrshire cross females. At 2 years of age female progeny of Sahiwal and Simmental sires were significantly heavier than the female progeny of Ayrshire sires but not of Mixed breed sires, viz. Sahiwal x Ayrshire and calves with sires not known. The Ayrshire breed was shown to be superior to the Sahiwal breed in transmitted effects for milk production and the Sahiwal breed was superior to the Ayrshire breed in transmitted effects for growth rate. It is concluded that the Sahiwal breed has potential to contribute to both milk and beef production programmes when combined in crosses with Bos taurus breeds of cattle in ecological zones similar to the lower to mid-potential areas of the temperate highlands of Kenya.

Animals↗

PubMed1982

Heterosis, additive maternal and additive direct effects of the Red Poll and Boran breeds of cattle.

Data on 202 calves born, 191 calves weaned and 182 calves at 30 mo of age produced in 1969 from the Boran and Red Poll breeds and their reciprocal crosses were analyzed to estimate heterosis, additive maternal effects and additive direct effects on survival and growth traits from birth to 30 mo of age. The calves were produced in the Ankole District of south-western Uganda as a part of a beef cattle research program designed to provide information to support a commercial ranching development scheme in an area that had been cleared of the tsetse fly. Breed of sire effects were significant for birth and weaning weight, and breed of dam effects were significant for birth, weaning and 12-mo weight. Breed of sire and breed of dam effects that were significant showed the Boran breed to have higher values for all traits except breed of dam effects on birth weight; calves with Red Poll dams were 3.6 kg heavier (P less than .01) at birth than calves with Boran dams. Steers were significantly heavier than heifers at all ages except birth. Young cows (3 and 4 yr old) and old cows (9 yr old and older) produced calves that weighed significantly less at weaning, 12 mo and 18 mo than calves with dams that were 5 through 8 yr old. Heterosis effects were significant for weights at weaning, 12, 18, 24 and 30 mo of age; generally, heterosis effects on weight increased with age. Heterosis effects approached significance for survival from birth to 30 mo. Additive maternal effects were significant for birth weight; crossbred calves with Boran dams weighted 6.0 kg less at birth than crossbred calves with Red Poll dams. There was a reversal of the reciprocal effect between prenatal and postnatal gains; crossbred calves with Boran dams weighed 7.1 kg more at weaning than crossbred calves with Red Poll dams. Examination of additive direct effects showed the Boran breed to be significantly heavier than the Red Poll breed for birth weight and weaning weight. Additive direct effects showed the Boran breed to have generally higher (P greater than .05) values than the Red Poll breed for most other traits analyzed. Differences between straightbreds of the Boran and Red Poll breeds, which reflect differences in additive maternal and additive direct effects combined, significantly favored the Boran breed for weaning weight and 18-mo weight and favored (P less than .05) the Boran breed for all other traits except birth weight. It was concluded that the Red Poll breed had higher values for additive maternal effects for birth weight than the Boran breed in the climatic and nutritive environment in which this experiment was conducted; for most other traits evaluated, the Boran breed generally had higher values for additive maternal and higher values for additive direct effects than the Red Poll breed.

Age Factors↗

PubMed1982

Influence of postweaning gain interval on estimates of heritability and genetic correlations.

Heritability and phenotypic environmental and genetic correlations of postweaning gains for intervals of 28 to 224 d were calculated from data on 2,410 crossbred steers and 3,088 Hereford bulls. Gains were essentially linear for the 224-d interval. As the length of the performance interval increased from 28 to 224 d, heritability of gain increased from .12 to .55 among the crossbred steers and from .09 to .24 among the Hereford bulls. There was no tendency for heritability to be larger or smaller for intervals of like duration initiated early or late in the 224-d interval. Heritability of individual animal regressions of weight on days was evaluated as an alternative measure of gain/d. Heritabilities were not different between daily gain and regressions when measured over the same intervals. Genetic correlations were generally positive and much larger than the environmental or phenotypic correlations, indicating that genetic influences tended to persist from one interval to another. Genetic correlations between intervals tended to become smaller as the number of days separating the intervals increased.

Animals↗

PubMed1979