Showing papers on "Breed published in 1982"
TL;DR: Because age at puberty varied by 62 d among breeds and 88 d among bulls and important characteristics of semen quality improved slowly after puberty, careful evaluation of the stage of pubertal development in individual bulls is recommended before selecting young bulls for natural breeding or artificial insemination.
Abstract: Semen characteristics were evaluated every 2 wk from 7 through 13 mo of age in 31 beef bulls representing six breed groups (Hereford, Angus, Hereford x Angus crossbreeds, Angus x Hereford crossbreds, Red Poll and Brown Swiss). Breeds differed in age at puberty, defined as the age at which an ejaculate was first obtained that contained a minimum of 50 x 10(6) total spermatozoa with at least 10% progressive motility (Hereford, 326 +/- 9 d; Angus, 295 +/- 4 d; Hereford x Angus, 300 +/- 8 d; Angus x Hereford, 296 +/- 9 d; Red Poll, 283 +/- 9 d and Brown Swiss, 264 +/- 9 d). Significant breed differences also were observed in concentration of spermatozoa, progressive motility, seminal protein concentration, abnormal spermatozoa and acrosomal morphology. Considerable variation was observed for the majority of pubertal traits among the 31 bulls, indicating that differences in stage of pubertal development existed among and within breeds of beef bulls between 7 and 13 mo of age. However, adjustment of data to age at puberty negated breed differences (P greater than .10), indicating that the pubertal patterns of change occurring in each semen characteristic were similar for the breeds evaluated. Concentration of spermatozoa, progressive motility, seminal protein concentration, percentage spermatozoa with normal head and tail morphology and percentage spermatozoa with normal acrosomal morphology increased (P less than .01) from puberty through 16 wk after puberty in all bulls and all breds. During the first 6 wk after puberty, rapid increases (P less than .01) were observed in percentage spermatozoa exhibiting normal head morphology (excluding acrosomes) and progressive motility, and a rapid decrease (P less than .01) was observed in percentage spermatozoa with proximal cytoplasmic droplets, with values at +6 wk approaching those reported for mature bulls. Percentage spermatozoa with normal acrosomal morphology and concentration of spermatozoa improved more slowly and had not reached mature levels by 16 wk after puberty. Because age at puberty varied by 62 d among breeds and 88 d among bulls and important characteristics of semen quality improved slowly after puberty, careful evaluation of the stage of pubertal development in individual bulls is recommended before selecting young bulls for natural breeding or artificial insemination. Additional investigations are needed to define the patterns of pubertal development through sexual maturity in beef bulls and to establish relationships to fertility.
135 citations
TL;DR: Some female Eiders breed when they are two years old, and most do so by the time they are four, but young birds lay later, have smaller clutches and are lighter in weight at the start of incubation than older females.
Abstract: Some female Eiders breed when they are two years old, and most do so by the time they are four. Young birds lay later, have smaller clutches and are lighter in weight at the start of incubation than older females.
89 citations
TL;DR: Sexual development of the Brahman bull occurred at a later chronological age and in a nonparallel pattern to that of the Angus, suggesting differences in SC exist for various populations of Brahman bulls and should provide opportunities for progress in selection for this trait.
83 citations
Journal Article•
TL;DR: Approximate threshold levels for semen characteristics that could provide a diagnostic basis for the classification of stallions as being suitable or doubtful for breeding purposes are presented.
Abstract: A study of stallion fertility was conducted on commercial studs in eastern Australia over 4 breeding seasons (1974/75-1977/78). Data from 47 stallions (66 stallion seasons) aged 2-26 years and representing 7 breeds and 1664 mares were used to relate seminal characteristics to fertility. Percentage pregnancies per service was the most sensitive measure of fertility with stallions on commercial studs. Breed and age of stallion, breeding season and the referral status of the stallion ('suspect' or 'normal') had significant (P less than 0.01) effects on fertility. The semen characteristics that were clearly associated with percentage pregnancies per service were: total volume, gel-free volume, sperm concentration, total numbers of spermatozoa and total number of live spermatozoa. Approximate threshold levels for these characteristics are presented which could provide a diagnostic basis for the classification of stallions as being suitable or doubtful for breeding purposes.
71 citations
TL;DR: Oxytocin was measured radioimmunologically during the oestrous cycle in six ewes of each of two local Moroccan breeds of sheep, finding that oxytocin concentrations remained at about the limit of detection for a further 19-20 days in both breeds.
Abstract: Oxytocin was measured radioimmunologically during the oestrous cycle in six ewes of each of two local Moroccan breeds of sheep. Concentrations in both breeds approached the lower limit of the assay (3 pg/ml) from 2 days before oestrus, throughout heat and ovulation until day 2 of the cycle. Oxytocin concentrations then increased in both breeds, the resulting highest levels on days 5-7 were, on average, between 30 and 60 pg/ml in the D'man sheep and 13-31 pg/ml in the Timhadite breed. Oxytocin levels then decreased to about 7 pg/ml in the D'man and about 4-5 pg/ml in the Timhadite breed on days 14-15. After ovariectomy oxytocin concentrations remained at about the limit of detection for a further 19-20 days in both breeds.
70 citations
TL;DR: In this article, live weight gain and efficiency of purebred British Friesian steers and of crossbred steers out of British-Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Lincoln Red, Simmental, South Devon and Sussex sires were examined in two beef production systems.
Abstract: The live-weight gain and efficiency of food utilization of purebred British Friesian steers and of crossbred steers out of British Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Lincoln Red, Simmental, South
Devon and Sussex sires were examined in two beef production systems. One system was similar to the commercial 18-month grass/cereal system (16-month system) and the other to a commercial 2-year system (24-month system). The cattle were slaughtered at a standard level of fatness, determined by the use of the Scanogram ultrasonic machine.The trial extended over 3 years and a total of 579 cattle were involved.Data for the two production systems were analysed separately. Adjustment was made to equal age at the beginning of the test and to equal carcass subcutaneous fat concentration.There were important differences between sire breeds in daily live-weight gain (P < 0.05), the order of performance for the different sire breeds being similar in the two systems. Charolais and Simmental crosses grew fastest, followed by South Devon crosses, and then by the purebred British Friesian and the other native breed crosses. Faster growing sire-breed crosses were generally heavier and older at slaughter; they ate more, and there was no obvious relationship between sire-breed means for growth rate and efficiency. The range in efficiency between sire breeds was 27 g and 17 g live-weight gain per kg digestible organic matter intake for the 16- and 24- month systems respectively. In both systems, Hereford crosses ranked highest and the purebred British Friesian among the lowest. Probability levels for sire breed differences were P < 0.1 (16 month) and P < 0.01 (24 month).
58 citations
TL;DR: The results indicate that conformation has little practical value as a predictor of carcass composition within breed.
57 citations
TL;DR: The results indicate that bulls of different breeds should not be compared to established standards; a more acceptable procedure would be the use of deviations from the respective breed-station-year means.
Abstract: Heritability estimates for scrotal circumference and testicular tone at weaning (225 d) and yearling (365 d) were determined from records on 565 bulls from a purebred Angus herd; year, station and breed effects were determined from scrotal circumference records on 2,420 bulls at five tests stations Year, breed and breed X year effects on scrotal circumference, length, width and volume were determined from records on 347 bulls at one station Heritability estimates (+/- SE) were 60 +/- 17, 28 +/- 18 and 25 +/- 18 for weaning scrotal circumference, right and left tone, and 38 +2- 16, 72 +/- 18 and 52 +/- 17 for yearling scrotal circumference, right and left tone, respectively With the exception of low negative correlations of 205-d weight and longissimus muscle area with yearling scrotal circumference (-01 and -02, respectively), correlations of growth and live-estimated carcass traits with weaning or yearling scrotal dimensions were low and positive (08 to 35) In the second data set, Simmental and Angus had greater (p less than 01) yearling scrotal circumferences than Charolais or Herefords; means were 353, 350, 337 and 335 cm, respectively Station and station x breed effects were significant (P less than 01), with the latter effect indicating that breeds did not rank similarly in scrotal circumference at different test stations In the third data set, scrotal circumference and volume were essentially the same as scrotal length and width in ranking breeds year X breed interactions were nonsignificant for all scrotal traits, indicating that breeds were ranked similar in different years with respect to scrotal dimensions These results indicate that bulls of different breeds should not be compared to established standards; a more acceptable procedure would be the use of deviations from the respective breed-station-year means
57 citations
TL;DR: The relationship between paired testes weight (PTW) and scrotal circumference (SC) was examined in 335, 1- and 2-yr-old Hereford and Angus bulls and differences in SC due to breed were examined.
Abstract: The relationship between paired testes weight (PTW) and scrotal circumference (SC) was examined in 335, 1- and 2-yr-old Hereford and Angus bulls. Measurements were taken within 15 days of each othe...
55 citations
TL;DR: In this paper, the authors compared the characteristics of purebred British Friesian steers and crossbred steers by eight sire breeds, including Charolais, Simmental and the main traditional British beef breeds, in 16-month and 24-month beef production systems.
Abstract: Carcass characteristics of purebred British Friesian steers and crossbred steers by eight sire breeds out of British Friesian dams, in 16-month and 24-month beef production systems, were compared. Sire breeds included Charolais, Simmental and the main traditional British beef breeds. A total of 579 cattle were involved.The cattle were slaughtered at a fixed level of fatness and the carcasses evaluated using a standardized commercial cutting technique. Data were adjusted to equal carcass subcutaneous fat concentration.Sire breed differences were similar in both feeding systems. Charolais crosses killed-out best and Aberdeen- Angus and Devon crosses poorest; the range was 25 g/kg live weight.Significant differences were recorded between breeds in the proportion of saleable meat in the carcass (P<0·001): Charolais, Sussex and Aberdeen-Angus crosses had the highest values, on average being 15g/kg carcass weight better than purebred Friesians. Breed differences were detected in the proportion of total saleable meat occurring in the higher-priced joints, Simmental and Charolais crosses ranking highest, but the range across sire breeds was only 10 g/kg carcass weight. There were important differences between sire breeds in rate of meat weight gain that were related to mature size.Purebred Friesians were less efficient than either Charolais or Hereford crosses in converting food into meat in the 24-month system. Friesians also had the lowest efficiency and Hereford crosses the highest efficiency in the 16-month system, although the differences were not statistically significant.
TL;DR: The results show large breed differences in the susceptibility to copper poisoning, some breeds being at risk when given diets containing 12mg copper per kg dry matter for long periods.
Abstract: Lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given diets containing 12 or 20 mg copper per kg dry matter for 13 weeks. Concentrations of liver copper and of copper and aspartate amino-transferase in the plasma were measured regularly, and the concentrations of copper in the kidney, mandible and cheek muscle were also measured terminally. Livers were examined for histological symptoms of copper toxicity.Wide breed variation was apparent in liver copper concentration after 6 weeks and in plasma aspartate aminotransferase concentration after 9 weeks. At slaughter, total liver copper and kidney copper concentration showed significant breed variation. For all traits, the Texel-cross lambs had the highest concentrations, followed by the Suffolk crosses, and the Blackface had the lowest. The proportion of ingested copper retained in the liver of the Texel-cross lambs was twice that of the Blackface lambs (0·137 v. 0·056), with the other breed crosses intermediate.There was a significant difference between diets for liver, kidney and mandible copper concentrations, plasma aspartate amino-transferase concentration, and for total liver copper but not for cheek muscle. Both diets produced elevated plasma aspartate amino-transferase concentration and histological symptoms of copper toxicity in the livers of some lambs.The results show large breed differences in the susceptibility to copper poisoning, some breeds being at risk when given diets containing 12mg copper per kg dry matter for long periods. There was no suggestion that breeds differed in resistance to poisoning other than through different retentions of copper consumed
TL;DR: The results of interviews with owners of free-ranging horses (Camargue breed) are given which show that, though rare, infant killing occurs in this breed, and that it seems to be confined to male foals.
TL;DR: The reproductive biology of Antarctic serolids is compared with that of temperate isopods, and it is shown that they produce larger young which is related to their larger adult size.
Abstract: Several species of serolid isopod from Signy Island, South Orkney Islands and also from South Georgia were studied, and aspects of their reproductive behaviour and associated morphology are discussed. InSerolis polita Pfeffer egg-laying took place at a mean age of 28 months, and the eggs were then incubated in a ventral marsupium for a period of 20 months before the release of juveniles in the spring. The mean egg dry weight at spawning was 0.68 mg forS. polita and 3.35 mg forSerolis cornuta Studer. The egg weight increased during marsupial development due to the uptake of minerals, but the total calorific content fell. Within each species brood size was linearly related to female size and the mean number of eggs varied from 40 forS. polita to 232 forSerolis pagenstecheri Pfeffer. There was no detectable marsupial mortality.S. polita appeared to breed repeatedly at two-year intervals, butS. cornuta probably only breeds once. The reproductive biology of Antarctic serolids is compared with that of temperate isopods, and it is shown that they produce larger young which is related to their larger adult size. The extremely protracted period of marsupial incubation is associated with the need to synchronize reproduction with the seasonal nature of Antarctic primary production.
Journal Article•
TL;DR: There were marked seasonal variations in the scrotal circumference, morphologically normal spermatozoa, libido, and serving capacity for each of the breed types.
Abstract: Seasonal variations in scrotal circumference, spermatozoal motility, morphologically normal spermatozoa, libido, and serving capacity were studied in Suffolk, Lincoln, Columbia, and Polypay rams (5 of each breed). There were marked seasonal variations in the scrotal circumference, morphologically normal spermatozoa, libido, and serving capacity for each of the breed types. Mean scrotal circumference was highest from August through October and lowest in February. Spermatozoa that were morphologically normal were highest in proportion in September (82.3%) and lowest in proportion in February (57.8%). Libido and serving capacity scores were highest from September through November and lowest in March.
TL;DR: The susceptibility of the North RonaldSAY breed of Orkney sheep to copper poisoning when first introduced to a diet of purely terrestrial herbage is demonstrated by the high liver copper levels of the four dead sheep compared to the normal serum copper levels and unimpaired health of two other breeds of sheep and a north country Cheviot cross North Ronaldsay ram.
Abstract: Copper toxicity occurred in North Ronaldsay sheep fed on a diet of terrestrial herbage relatively high in molybdenum. Five sheep were taken from the island of North Ronaldsay, Orkney to the veterinary investigation centre at Thurso and fed solely on the herbage of the laboratory paddocks, supplemented in winter by hay made from these paddocks. The level of copper, molybdenum, zinc and total sulphur in the terrestrial herbage was analysed, together with the seaweeds which form the major part of the diet on North Ronaldsay. Serum copper, vitamin B12 and serum aspartate aminotransferase levels were obtained. Four of the five sheep died on this diet of terrestrial herbage and had liver copper levels of 1379, 1723, 2279 and 2281 mg/kg. The susceptibility of the North Ronaldsay breed of Orkney sheep to copper poisoning when first introduced to a diet of purely terrestrial herbage is demonstrated by the high liver copper levels of the four dead sheep compared to the normal serum copper levels and unimpaired health of two other breeds of sheep and a north country Cheviot cross North Ronaldsay ram.
TL;DR: Major differences between breeds were demonstrated in the thermo-stability of extracted intra-muscular connective tissue elements, being highest in the zebu breeds, intermediate in the Canchim and lowest in the Charolais.
TL;DR: Live-weight growth and efficiency of food utilization of purebred Galloway, Luing and Welsh Black steers, and crossbred steers out of Blue-Grey and Hereford × Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Limousin, Lincoln Red, Simmental, South Devon and Sussex sires, were examined in two suckled calf fattening systems.
Abstract: Live-weight growth and efficiency of food utilization of purebred Galloway, Luing and Welsh Black steers, and crossbred steers out of Blue-Grey and Hereford × Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Limousin, Lincoln Red, Simmental, South Devon and Sussex sires, were examined in two suckled calf fattening systems. In one system, autumn-born calves were purchased at 1 year of age and fattened during their second winter; the other system involved late winter-born calves, which were purchased at 7 months of age, overwintered on a cheap growing diet and fattened during their second summer. The trial involved a total of 1430 cattle and extended over 5 years (winter system) and 6 years (summer system).Cattle were slaughtered as close as possible to a standard carcass subcutaneous fat concentration.The data for crossbred and purebred cattle were analysed separately within the fattening system using least squares models, which included effects for year, sire breed and dam breed, and with regression on the age at beginning of the trial and carcass subcutaneous fat concentration estimated by visual appraisal.Breed differences in live weight at slaughter were similar to those recorded in the Meat and Livestock Commission's on-farm recording work. Among crossbreds, the larger sire breeds consumed more food per day, generally grew faster and were older at slaughter.They did not differ significantly in the efficiency with which food was converted into live-weight gain. Among the purebreds, the Luing had a relatively high daily food intake in relation to its growth rate and, together with the Welsh Black in the summer fattening system, was less efficient than the Galloway (P<0·05).
TL;DR: A comparison was made of the carcass characteristics of purebred Galloway, Luing and Welsh Black steers, and crossbred steers out of Blue-Grey and Hereford × Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Limousin, Lincoln Red, Simmental, South Devon and Sussex sires, in winter and summer fattening systems.
Abstract: A comparison was made of the carcass characteristics of purebred Galloway, Luing and Welsh Black steers, and crossbred steers out of Blue-Grey and Hereford × Friesian dams by Aberdeen-Angus, Charolais, Devon, Hereford, Limousin, Lincoln Red, Simmental, South Devon and Sussex sires, in winter and summer fattening systems. A total of 1430 cattle were involved and the trial extended over 6 years.The cattle were slaughtered when their fatness was estimated, using the Scanogram ultrasonic machine, to be in fat class 3L of the Meat and Livestock Commission Beef Carcase Classification Scheme. Carcasses were evaluated using a standardized commercial cutting technique.The data for crossbred and purebred cattle were analysed separately within the fattening system using leastsquares models, which included effects for year, sire breed and dam breed, and with regression on age at the beginning of the trial and carcass subcutaneous fat concentration estimated by visual appraisal.Limousin and Charolais crosses killed out best. Their carcass weights were, on average, 20g/kg live weight heavier than those of Aberdeen-Angus, Devon, Hereford and Lincoln Red crosses. There was a range of 20 to 30 g/kg carcass weight between sire breeds in carcass saleable meat yield: the highest values were recorded for the Limousin crosses (evaluated on winter fattening only) followed by Charolais and Aberdeen-Angus crosses; Lincoln Red crosses had the lowest values among the crossbreds and Luing cattle among the purebreds. These differences were more a reflexion of differences in fat trim than of differences in meat to bone ratio.Continental sire breeds had significantly more of their total saleable meat in the higher-priced cuts (P<0·05), although the range between sire breeds was only 15 g/kg.
1 Jan 1982
TL;DR: The evolution of the Belgian Blue breed from a dual-purpose to an extremely muscled type is described and the hypothesis of a single recessive gene is tested and seems tenable.
Abstract: The evolution of the Belgian Blue breed from a dual-purpose to an extremely muscled type is described. A genetic analysis of this transformation is presented; it is based: 1) on field data; 2) on experimental data. The hypothesis of a single recessive gene is tested and seems tenable. In any case, two distinct biological types segregate within commercial herds with Blue Belgian cattle. The present-day situation of the breed is briefly described and also the testing programmes.
TL;DR: Environmental and genetic effects on preweaning growth traits were evaluated for 4034 calves born and 3732 calves weaned in second and later parities from contemporary populations of first-cross dams maintained at two locations, Brandon and Manyberries.
Abstract: Environmental and genetic effects on preweaning growth traits were evaluated for 4034 calves born and 3732 calves weaned in second and later parities from contemporary populations of first-cross dams maintained at two locations, Brandon and Manyberries. The calves were sired by Chianina (Chi), Charolais (C), Limousin (L) and Simmental (S) bulls mated to 10 F1 dam crosses representing the Hereford × Angus (HA) and nine dam-cross combinations produced by matings of C, S and L sires with H, A and Shorthorn (N) females. Sex differences were important (P < 0.0001) with males averaging 7% heavier at birth and 5% higher in measures of postweaning growth than females. Location differences were negligible for birth weight (1.2%), but preweaning growth rate was 10–13% greater at Brandon (P < 0.0001) than at Manyberries. Year differences were large for all traits measured (P < 0.0001) and, with the exception of birth weight, were related to differences in annual weaning date. Progeny rankings by terminal sire breed ...
TL;DR: A historic perspective of the beef cattle population and the legion of people directing its genetic change is developed so that future leadership can increase the rate of breeding technology assimilation.
Abstract: The purpose of this essay is to develop a historic perspective of the beef cattle population and the legion of people directing its genetic change so that future leadership can increase the rate of breeding technology assimilation. Use of cattle for beef to feed millions is relatively recent. The beef industry of the United States has a rich, romantic heritage that combined Spanish exploitation with British tradition. Spanish cattle became adapted as the Texas longhorn and the European cattle became indigenous. Breeds developed in Britain replaced both. The Zebu was introduced to produce cattle adapted to the Gulf Coast. Selection for early maturity in the British breeds promoted by livestock shows was ended by the dwarf gene. The Charolais breed demonstrated growth potential. Then in 1967, Continental European breeds were imported, given an array of biological types from which to select. Beef cattle breeding research expanded after the second world war through the three regional projects. Performance Registry International was the focal point for performance. The Beef Improvement Federation produced guidelines for recording beef performance including those for national sire evaluation. U.S. Meat Animal Research Center evaluated the several newly introduced breeds. To date, breeding researchers have developed breeding technology for the use by breeder. The major breed association are keeping and utilizing performance records. The genetic structure of the beef breeds is being altered by the use of AI such that genetic change can be made rapidly by the use of superior sires evaluated on their progeny in many herds.
TL;DR: Each of the phenotypes examined seemed to play a role in the cow's social adaptation to the variable herd conditions, and both phenotypic and breed characteristics affect the fitness and ability to adapt to the environmental conditions.
TL;DR: Results of a diallel analysis of Hereford-Red Pool matings indicated that maternal influence of the Red Poll breed was superior to Herefords for body weight up to 24 mo of age and incidence of puberty at 11.5 mo.
Abstract: Puberty traits of straightbred and crossbred heifers (n = 301) were evaluated under pasture conditions. Breed groups represented were straightbred Hereford and Red Poll, reciprocal crosses of these two breeds, Angus X Hereford, Angus X Charolais-Cross, Brahman X Hereford and Brahman X Angus. Breed group was an important (P less than .01) source of variation in heifer weights and in age at puberty. Straight-bred Red Poll and Red Poll cross heifers were youngest at puberty, Angus X Hereford and Angus X Charolais-Cross were intermediate, and straightbred Hereford and Brahman crosses were oldest at the onset of puberty. At the beginning of their first mating season at 19.5 mo of age, 96% of the straightbred Red Polls, 95% of Red Poll crosses, 81% of Angus X Herefords, 89% of Angus X Charolais-Crosses, 68% of straightbred Herefords, 48% of Brahman X Herefords and 74% of the Brahman X Angus had attained puberty. Results of a diallel analysis of Hereford-Red Pool matings indicated that maternal influence of the Red Poll breed was superior (P less than .01) to Herefords for body weight up to 24 mo of age and incidence of puberty at 11.5 mo. Red Polls also exceeded Herefords in direct effects for puberty percentage at 11.5, 15 and 19.5 mo of age. Heterosis was significant for puberty percentage and weight. Breed group differences in pregnancy rate at 24 mo were not significantly.
TL;DR: 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.
Abstract: 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.
TL;DR: Breed of maternal grandsire and of maternal granddam were the only factors that appeared to influence the time of parturition of beef cows.
Abstract: Data on 1151 calvings recorded over a 4-yr period at the Agriculture Canada Research Station, Brandon, Manitoba were analyzed to examine the influence of various factors on the time of day of calving of beef cows. Factors examined were year of calving, sex of calf, age of cow, weight of cow, calf birth weight and breed type. The hourly distribution of calvings was relatively uniform over the 24-h period. Slightly more calves were born from 0700 h to 1900 h (51.5%) than between 1900 h and 0700 h. Breed of maternal grandsire and of maternal granddam were the only factors that appeared to influence the time of parturition. Percentages of calves born during the day (0700–1900 h) having Hereford, Charolais, Simmental and Limousin grandsires were 59.0, 54.2, 51.0 and 45.6, respectively, whereas 55.9, 55.6 and 41.0% of the calves from Hereford, Angus and Shorthorn granddams, respectively, were born during the day. The hourly distribution of 212 potentially abnormal calvings was significantly uneven. The highest ...