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1.
A 2(3) factorial arrangement of treatments was utilized to determine effects of postweaning zeranol implantation, breed (Angus vs Limousin) and castration (bull vs steer) on growth, behavior and carcass traits. An initial slaughter group was used to account for breed differences in composition and to determine fat and lean growth in the 9-10-11th rib section (NTE). The remaining cattle were fed a finishing diet to a fat end point of .76 cm, as determined by a backfat probe. Control bulls outgained (P less than .01) control steers both to the first kill date and over the entire test and did not require significantly more time to reach the fat end point. The implant did not influence gain in bulls but did increase gain in steers. Angus and Limousins were similar in growth rate for the first 126 d before the first slaughter date. Limousins required more (P less than .01) time to reach the fat end point. Bulls and Limousins produced heavier (P less than .01) carcasses and larger rib eyes (P less than .05; bulls; P less than .01; Limousins). Steers and Angus had higher (P less than .01) marbling scores and lower bone maturity. Implanting decreased (P less than .05) marbling and increased carcass maturity. Small but significant shifts in carcass wholesale cut weight distribution were found between breed and sex condition groups. Bulls and Limousins had greater lean growth in the NTE. Bulls and steers were similar in fat growth, but Angus exceeded Limousin in this trait. Zeranol reduced scrotal circumference (P less than .01) and testicle weight at slaughter (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
The effect of high (HED) and medium energy diets (MED), fed to Hereford (H) and Angus (A) bulls from 6 through 24 mo of age, on scrotal circumference (SC), paired testes weight (PTW), epididymal sperm reserves (ESR) and seminal traits were examined. Over 3 yr, 120 bulls were involved. Angus exceeded H for both SC and PTW. Hereford bulls in yr 2 had smaller SC than in yr 1 or 3 but the response for A was consistent. Year affected PTW. In yr 2 Hereford bulls fed HED had 75% fewer ESR than MED-H bulls (9.3 vs 37.2 X 10(9]. Comparably treated A bulls had similar ESR numbers (29.2 vs 33.4 X 10(9]. In yr 3, epididymal sperm reserves of HED-H were depressed by 35% compared with MED-H (23.1 vs 35.7 X 10(9], whereas HED-A had 14% fewer ESR than did MED-A bulls (28.6 vs 33.1 X 10(9]. It was not obvious why H bulls were more susceptible to the effects of HED. Seminal quality of HED bulls was inferior to that of MED bulls, particularly with respect to progressive motility and the incidence of sperm in which a crater defect of the head was present at 2 yr of age. In yr 2 all seminal traits were severely depressed in 2-yr-old HED-H. Feeding HED to young H and A bulls reduced their reproductive potential.  相似文献   

3.
Feedlot traits, carcass traits and distribution of commercial cuts of crossbred intact male progeny (n = 556) from young and mature Hereford, Red Poll, Hereford X Red Poll, Red Poll X Hereford, Angus X Hereford, Angus X Charolais, Brahman X Hereford and Brahman X Angus dams were evaluated. First-calf heifers were bred to Red Angus bulls; Santa Gertrudis sires were used for each cow's second and third breeding seasons. Calves from these young dams were slaughtered at 13 mo. Calves of mature dams were all sired by Limousin bulls and slaughtered at 12 mo. Dam breed was a major source of variation in most bull traits. Progeny of Brahman-cross dams were inferior (P less than .01) in daily gain, final weight, carcass weight and in edible cuts/day of age compared with progeny from Bos taurus dams. Intact male progeny of Angus X Charolais dams ranked highest in longissimus area, cutability, and edible cuts/day of age. The range of dam breed means in percentage of steak, roast, bone-in cuts (chuck short ribs and back ribs), short plate and thin cuts, and lean trim was just over 1%. Greater variation among dam breeds existed in fat measurements. Analyses in which Hereford-Red Poll diallel data for young dams and mature dams were combined showed positive maternal heterosis for dressing percentage (P less than .05), carcass weight (P less than .05), carcass weight/day of age (P less than .05), estimated carcass fat (P less than .05), fat thickness (P less than .01) and marbling score (P less than .01). Reciprocal effects were inconsequential. Results illustrate the importance of dam breed-type effects in formulating breeding strategies for commercial beef herds.  相似文献   

4.
Birth, weaning, feedlot and carcass traits were evaluated on 1,181 calves sired by Charolais and Limousin bulls out of eight crossbred dam groups (Hereford X Angus, Angus X Hereford, Simmental X Angus, Simmental X Hereford, Brown Swiss X Angus, Brown Swiss X Hereford, Jersey X Angus, Jersey X Hereford). Calves were born in the spring over a 4-yr period during which dams ranged from 3 to 8 yr of age. Charolais-cross calves were 2.7 kg heavier (P less than .01) at birth and had a 9.9% higher (P less than .01) incidence of difficult calvings and 4.6% greater (P less than .05) preweaning death loss than did Limousin crosses. Charolais-sired calves out-gained Limousin-sired calves by 31 g/d (P less than .01) from birth to weaning and were 9 kg heavier (P less than .01) at weaning. After weaning, calves were self-fed a finishing diet and slaughtered as each animal attained an estimated carcass grade of low Choice. Charolais-cross calves gained 60 g/d faster (P less than .01) than Limousin crosses, were fed 6.8 fewer d and were 17.3 kg heavier (P less than .01) at slaughter. Feed efficiency was similar for both sire breeds. On a grade-equivalent basis, Charolais crosses produced 7 kg heavier (P less than .01) carcass and had 22 g more carcass weight per day of age (P less than .01). Charolais crosses had slightly less internal and external fat. Dressing percentage was higher for Limousin cross calves (64.6 vs 63.9%, P less than .01). Longissimus muscle area and carcass cutability were similar for crosses of both sire breeds.  相似文献   

5.
Reproductive traits and preweaning growth of progeny from young Hereford, Red Poll, Hereford X Red Poll, Red Poll X Hereford, Angus X Hereford, Angus X Charolais, Brahman X Hereford and Brahman X Angus dams were evaluated. First-calf heifers were mated with Red Angus bulls; Santa Gertrudis sires were used for each cow's second and third breeding season. Herefords, Red Polls and Hereford-Red Poll crosses were below average in percentage of calves weaned, whereas Angus-sired and Brahman-sired dams exceeded the overall mean. Angus X Charolais (P less than .10), Brahman X Hereford (P less than .01) and Brahman X Angus (P less than .10) dams weaned a higher percentage of calves than straightbred Herefords. None of these breed types differed from young Angus X Hereford females in reproductive performance. Angus X Charolais calves ranked highest in 180-d calf weight, exceeding progeny from both Hereford (P less than .01) and Angus X Hereford (P less than .10) dams. Brahman X Hereford dams weaned heavier (P less than .05) calves than Herefords, but their progeny did not differ at weaning from those reared by Angus X Herefords. Calves from Brahman X Angus dams weighed 12.7 kg less (P less than .01) than Angus X Hereford progeny. Analysis of the Hereford-Red Poll diallel showed evidence of (P less than .10) maternal heterosis in 180-d calf weight.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

6.
Two unselected herds of purebred Hereford and Angus cattle were created and their progeny evaluated during a 4-yr period (1964 to 1967) for 168-d postweaning gain when they were fed either a high- or medium-energy diet. Birth weight and 200-d adjusted weaning weight also were measured and the importance of sire x diet interactions for postweaning gain examined. Year effects were significant (P less than .001) for all traits in Herefords and for postweaning gain in Angus. Postweaning gain of both breeds increased in successive years, but no trend was observed for birth and 200-d weights. Bulls were heavier than heifers (P less than .05) for all three traits in both breeds. Hereford and Angus calves receiving the high-energy diet gained more (P less than .001) than their contemporaries fed the medium-energy diet. Sire differences were significant for birth weight in Herefords and for all three traits in Angus. Sire x diet interactions were not significant for postweaning gain in either breed. Genetic correlations were calculated by two methods: the two-way ANOVA approach using sire and sire x diet interaction variance components and the one-way ANOVA approach in which gains by progeny of each sire on each diet were considered to be two distinct traits. The genetic correlations for gain in Herefords could not be estimated by either method because of negative sire variance component estimates. The genetic correlations for gain in Angus were 1.08 for the two-way ANOVA method and 1.43 +/- .64 for the one-way ANOVA method. These results indicate that sires ranked the same based on progeny performance when fed either diet.  相似文献   

7.
Simmental and Hereford bulls were individually fed varying levels of the same diet to determine the effect of energy intake after weaning on rate of sexual development. For 200 d, 29 Simmentals were fed an average of 14.6, 19.2 or 23.8 Mcal and 27 Herefords were fed 13.4, 17.5 or 22.2 Mcal metabolizable energy per bull daily. Higher energy did not hasten sexual development, as measured by serum testosterone, age at first mating or age at puberty. As energy level increased, weight at puberty increased (P less than .05) for both breeds, and scrotal circumference at puberty increased (P less than .05) for Simmentals. When adjusted for breed and energy level, bulls that were heavier at 1 yr of age had larger scrotal circumference (P less than .05) and were younger at puberty (P less than .01). Bulls that had higher serum testosterone at 1 yr of age reached puberty earlier (P less than .01). At a constant age there was no relationship between testosterone and scrotal circumference. Although higher levels of energy increased scrotal circumference of Simmentals, it did not hasten sexual development for either breed.  相似文献   

8.
Two hundred and fifty-one Aberdeen Angus, Horned Hereford, Polled Hereford, and Charolais bulls were examined at the time of sale (sale) and again from 10 to 85 days later (test) to determine the effect of amount of body fat and loss of fat on semen quality. Sale and test measurements included body weight, backfat depth, and scrotal circumference. Breeding soundness evaluations were done at test. For all bulls, over all years, the positive correlations of body weight loss vs. backfat loss, weight loss vs. scrotal circumference loss, and backfat loss vs. scrotal circumference loss were highly significant. Aberdeen Angus, Horned Hereford, Polled Hereford, and Charolais bulls lost weight at a mean rate of 1.77, 2.19, 1.94, 1.16 kg per day, respectively, in the interval from sale to test. Bulls classified as unsatisfactory lost significantly more weight than satisfactory bulls. However, bulls classified as unsatisfactory did not differ significantly from satisfactory bulls in the amount of backfat at sale and test and in the amount of backfat lost. No significant relationship could be demonstrated between increments of backfat and classifications of breeding soundness evaluations. Bulls with satisfactory semen quality had significantly larger scrotal circumference measurements than those with questionable or unsatisfactory classifications. Backfat data at bull sales may be helpful in selecting bulls with desirable growth characteristics, as well as reducing the risk of purchasing bulls with poor semen quality due to excessive body fat.  相似文献   

9.
The objective of the study was to characterize body growth, testicular development, and puberty from 8 to 14 mo of age in bulls (n = 120) produced by mating sires from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu breeds to MARC III ((1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) cows. Traits evaluated were birth weight, weaning weight (at 215 d), yearling weight, ADG from 8 to 14 mo of age, paired testicular volume growth from 8 to 14 mo of age, age at puberty (determined by production of 50 x 10(6) sperm with 10% motility), age at freezable semen (determined by production of 500 x 10(6) sperm with 50% motility), and, at 15 mo of age, paired testicular weight and daily sperm production per testis pair. There was an effect of sire breed (P = 0.03) for age at puberty; animals with Wagyu and Swedish Red and White inheritance reached puberty at a later date (302 and 302 d of age, respectively) compared with Angus-sired bulls (268 d). Age at puberty for Hereford-, Norwegian Red-, and Friesian-sired bulls was 270, 271, and 278 d, respectively. Differences in BW were observed (P = 0.03) at birth; bulls with Hereford and Friesian were heavier at birth (43 and 41 kg, respectively) compared with those with Norwegian Red, Swedish Red and White, and Wagyu inheritance (39, 38, and 38 kg, respectively). Differences in BW were also observed at 1 yr of age (P = 0.001), where the heaviest animals were those sired by Angus (450 kg), whereas the lightest animals were those sired by Wagyu (403 kg). Bulls with Wagyu inheritance had the lowest (P = 0.04) ADG (1.12 kg/d) compared with bulls with inheritance from Hereford (1.22 kg/d), Angus (1.28 kg/d), Norwegian Red (1.24 kg/d), Swedish Red and White (1.25 kg/d), and Friesian (1.27 kg/d). Differences in scrotal growth rate were not significant (P = 0.99). They ranged from 1.95 in Angus-sired to 1.66 cm3/d in Wagyu-sired bulls. There were no differences (P = 0.80) for age at freezable semen (335 +/- 10 d). At slaughter (15 mo of age), there were no differences (P = 0.62) for paired testicular weight (603 +/- 28 g) and daily sperm production (10.6 x 10(9) +/- 0.9 x 10(9) per testis pair). Growth of bulls with Wagyu inheritance was slower, and bulls with Wagyu or Scandinavian inheritance reach puberty at an older age than bulls with Angus inheritance.  相似文献   

10.
Three groups of 1/2 Simmental X 1/4 Brahman X 1/4 Hereford bull calves were used during two different years to study effects of zeranol on sexual development. At 154 d of age, half the calves were implanted with 36 mg zeranol and half, not implanted, served as controls. Implanted calves were reimplanted at 90-d intervals throughout the trial (9 mo) each year. Trial 1 was conducted with 24 calves and Trial 2 was conducted the following year with 10 bulls. Twenty-four days after weaning (200 d of age) and at 28-d intervals thereafter, bulls in drylot in Trial 1 were weighted, scrotal circumference (SC) was measured and an ejaculate of semen was collected by electroejaculation to determine puberty. At these times, bulls were given 200 micrograms of GnRH i.m. and blood was collected at 0, 1, 2, 3, 4 and 5 h after GnRH. Serum concentrations of LH and testosterone (TEST) were determined. At slaughter, testis weight, length and circumference and pubertal status were recorded. Bulls implanted with zeranol had smaller SC than control bulls during the entire 9-mo period (P less than .0001). More control bulls reached puberty than did implanted bulls (82.4 vs 23.5%, respectively; P less than .001). Control bulls had larger testis measurements at slaughter (P less than .0001). Implants did not alter total weight gain or ADG (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

11.
Growth and testicular development between 7 and 15 mo of age were evaluated in bulls produced by mating sires of six breeds (Hereford, Angus, Belgian Blue, Brahman, Boran, and Tuli) to Angus, Hereford, and MARC III (four-breed composite) cows. At 12 mo of age, Angus- and Hereford-sired bulls had the heaviest body weight (P < 0.08 to 0.001), whereas Brahman- and Belgian Blue-sired bulls were intermediate, and Boran- and Tuli-sired bulls weighed the least. Bulls sired by European breeds grew more rapidly after weaning (P < 0.01) than did Brahman-, Boran-, and Tuli-sired bulls, and these differences in growth rate were maintained through 15 mo of age, indicating that offspring of heat-adapted sire breeds (Brahman, Boran, and Tuli) have lower postweaning rates of gain, particularly during winter months, than do offspring of nonheat adapted sire breeds. Testis size was smaller initially (P < 0.01) and remained smaller in offspring of heat-adapted sire breeds through yearling age. By 15 mo of age, testis size was largest (P < 0.06 to 0.001) in Angus-sired bulls and had become similar among Hereford-, Brahman-, Boran- and Belgian Blue-sired bulls but remained smaller (P < 0.02 to 0.001) in Tuli-sired bulls. Thus, offspring of heat-adapted sire breeds had delayed testicular development compared with that of nonheat adapted sire breeds, particularly through yearling age. At puberty, Angus-sired bulls were 23 to 82 d younger (P < 0.05 to 0.001) than all other sire breeds except Hereford, and Brahman-sired bulls were older at puberty (P < 0.05 to 0.001) than were bulls of all other sire breeds except Boran. Testis size at puberty was quite similar among breeds of bulls (scrotal circumference = 27.9 +/- 0.1 cm) despite large breed differences in age, body weight, and hip height. Thus, measurement of yearling testis size was a reliable indicator of age at puberty among widely divergent breeds of bulls. In addition, the lower postweaning rates of gain and the smaller and slower testicular development in offspring of heat-adapted sire breeds should be noted by cattle producers considering use of such breeds in crossbreeding and breed improvement programs.  相似文献   

12.
Mid-rib hair coat samples (n = 577) were obtained from 9- to 10-mo-old Hereford and Angus bulls and heifers to examine diet and breed differences in hair coat characteristics and their relationship to 168-d postweaning gain. Each sample was cleaned and subdivided into guard hairs and undercoat. Dependent variables included the number, weight, length, diameter and percentage of medullation of guard hairs and undercoat. Sources of variation included breed, sire nested within breed, year (1965 or 1966), sex of calf, diet fed during the postweaning gain test (2 parts rolled grain:1 part chopped hay vs all chopped hay) and the linear regression on age of calf as a covariate. Factor analysis was used to transform the 10 hair coat variables into a set of four factors that accounted for 71% of the total variance of the original variables. Angus cattle tended to have shorter, less medullated coats (Factor 1), shorter, larger diameter undercoat hairs and guard hairs with less medullation than Herefords. Sire within breed differences existed for weight, length, and diameter of both types of hairs and all four factors. Compared with the medium-energy-diet, the high-energy diet reduced hair weight per unit of surface area, undercoat number and guard hair medullation. Undercoat density (Factor 3) was reduced by the higher-energy diet (P less than .001), whereas guard hair density (Factor 2) was not changed.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

13.
Alkaline phosphatase (APase) activity in tissue samples, with adherent bacteria, was measured from two sites in the rumen and from two sites in the abomasum of 57 yearling Angus and Hereford bulls and heifers fed a high or a low energy diet. In the rumen, APase activity was higher at the caudoventral blind sac than at the dorsal sac in animals of both breeds fed the high energy diet and in Angus bulls fed the low energy diet, but the reverse was observed in Hereford bulls fed the low-energy diet (P less than .01). In the abomasum, APase levels were higher for bulls than heifers (P less than .01) and higher at the fundic than at the pyloric region (P less than .01). Morphological studies also showed that rumen samples from animals fed a high energy diet exhibited a more widely distributed APase activity and an increase in the digestive recycling of epithelial cells that produced some "pitting" of the tissue. The higher APase activity of the epithelial tissue of animals fed the high energy diet may be explained by the greater rate of cell death and renewal indicated by the higher mitotic index reported by other researchers who have studied the cell cycle of the rumen epithelium in ruminants fed high and low energy diets.  相似文献   

14.
The effect of bull exposure on the resumption of estrous activity following parturition was studied in an experiment using mature Hereford and Hereford X Angus beef cows. In the spring of 1981 and 1982, cows were assigned by breed and calving date to one of two treatment groups. Cows were exposed to bulls either from 3 to 85 d postpartum (BE; n = 45, 1981; n = 35, 1982) or from 53 to 85 d postpartum (NE; n = 39, 1981, n = 36, 1982). Blood samples were collected from all cows once weekly from calving until 85 d postpartum to determine progesterone concentrations. The first increase in progesterone, which indicated onset of estrous cycles occurred at 43 +/- 2 vs 63 +/- 2 d (P less than .01) in 1981 and at 39 +/- 2 vs 61 +/- 3 d (P less than .01) postpartum in 1982 in BE cows and NE cows, respectively. Early postpartum exposure of cows to bulls reduced the postpartum anestrous interval.  相似文献   

15.
This study was conducted to evaluate the influence of age, breed, epididymectomy and semen processing on the concentration of estradiol-17 beta (E2) in bovine semen. Semen was collected either by electroejaculation or with an artificial vagina. Neat semen samples were stored at -20 C until analysis. Processed, frozen semen and an egg yolk-citrate semen extender were obtained from a commercial semen processing firm and stored in liquid nitrogen at -196 C. The concentration of E2 in semen was determined by radioimmunoassay. Semen from mature (greater than 24 mo), fertile Brahman (n = 19), Brangus (n = 16), Charolais (n = 29), Holstein (n = 15) and Santa Gertrudis (n = 25) bulls was analyzed for E2 concentration, and no difference (P greater than .10) between breeds was found. There was no difference (P greater than .10) in seminal E2 concentration between mature, fertile bulls (n = 104) and epididymectomized bulls (n = 22). In semen collected from prepuberal (12 to 16 mo, n = 21), peripuberal (17 to 20 mo, n = 17) and mature (greater than 24 mo, n = 19), Brahman bulls, the mature bulls had a lower (P less than .01) semen E2 concentration than peripuberal and prepuberal bulls. There were no differences (P greater than .10) in seminal E2 concentration among peripuberal Angus (n = 8), Hereford (n = 8) and Brahman (n = 17) bulls.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

16.
Angus and Angus x Hereford heifer calves born in spring or fall seasons were allotted by weight at weaning to be exposed to bulls for calving at either 24 or 30 mo of age. Comparisons were made 1) within birth season--heifers born in the same season were first exposed to bulls at either 14 to 16 or 19 to 22 mo of age and 2) within breeding season--heifers born in different but consecutive seasons (spring-fall or fall-spring) were exposed to bulls during the same season but at different ages. Spring-born heifers exposed for 30-mo calving were heavier (336 vs 302 kg) and taller (P less than .01) at breeding than those exposed for 24-mo calving. Also, more were observed in estrus and became pregnant (P less than .01) during a 21-d AI breeding period, but season-long (63 d) pregnancy rates were not different (86%). Fall-born heifers exposed for 24- or 30-mo calving were similar for weight, hip height, and body condition score (BCS) at breeding, but season-long pregnancy rates were 71 and 94%, respectively (P less than .01). Although fall-born heifers were heavier at weaning (P less than .01), spring-born heifers were heavier, taller, and had higher BCS at breeding (P less than .01), regardless of age. Within spring breeding seasons, breeding weight and initial reproduction were not affected by heifer age. Within fall breeding seasons, older heifers were larger (P less than .01) and had greater reproductive performance (P less than .05) than younger heifers. Age at breeding, irrespective of season, consistently affected (P less than .01) both hip height (116 vs 113 cm) and pelvic area (209 vs 178 cm2) for older vs younger heifers, respectively. These data indicate that heifers exposed for 30-mo first calving are heavier, taller, have larger pelvic area, and have greater reproductive performance than those exposed for 24-mo first calving.  相似文献   

17.
To determine the effects of location and season on growth of bulls, Hereford bulls from Montana (MH; n = 15) and Nebraska (NH; n = 15) and Brahman bulls from Texas and Louisiana (BB; n = 18) were moved to three locations: Montana (MT), Nebraska (NE) or Texas (TX). Each location received 5 NH, 5 MH and 6 BB. Control bulls (not relocated) were maintained at each location. All bulls were pubertal at the time of relocation in May 1984. At 28-d intervals, body weight, hip height, testis length and scrotal circumference were recorded for each bull for 22 mo after relocation. Paired testes volume (PTV) was calculated. Among Hereford bulls, body weights were similar (P greater than .10) in all control and relocated bulls by the end of the study, except that MH bulls moved to TX had lower body weights (P less than .01). Brahman bulls moved to northern locations had dramatically reduced body weights, compared to control Brahmans kept in TX; body weight of Brahman bulls in MT remained lower (P less than .01) at the end of the study. Brahman bulls in NE and MT had smaller scrotal circumference and PTV (P less than .01) than did control Brahmans in TX during the 1st yr after relocation. Relocated BB exhibited marked seasonal fluctuations in testis size, with increases during the summer and decreases during the winter (P less than .01); seasonal changes were not apparent in control Brahmans in TX. These results indicate that moving Brahman bulls to northern environments reduced body weight gain and caused dramatic seasonal changes in testis size; these effects were more pronounced in Brahman bulls moved to the most northern location.  相似文献   

18.
Testes were obtained from 34 Hereford or Angus bulls at about 1.5 yr of age and were used to investigate the relationship between the absolute number of Sertoli cells vs testicular size and daily spermatozoal production (DSP). Quantitative determination of DSP was based upon enumeration of elongated spermatids in testicular homogenates. The ratio of step 8 spermatids to Sertoli cells (S:SC) was established by direct counts of these cells in each of 20 round stage VIII seminiferous tubular cross sections for each bull. The number of Sertoli cells per paired testes was calculated as (total spermatids divided by S:SC)/.394, where total spermatids equalled the number of homogenization-resistant spermatids. The factor of .394 adjusted for the fact that the latter cells are present for only 39.4% of the spermatogenic cycle. All data were subjected to simple linear and second-order regression analyses. A positive linear relationship (P less than .005) was found between testicular weight (Y, in grams) and the absolute number of Sertoli cells per paired testes (X, in billions), which was characterized by the equation Y = 315.2 + 10.74X and a coefficient of correlation (r) of .56 (P less than .01). A similar relationship was observed between DSP (Y, in billions) and Sertoli cell numbers (X, in billions). This was characterized by the equation Y = 1.36 + .222X (P less than .005) and a coefficient of correlation of .70 (P less than .01). Daily sperm production was unrelated to the S:SC ratio (P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

19.
Females representing Hereford, Red Poll, F1 Hereford x Red Poll, F1 Red Poll x Hereford, F1 Angus x Hereford, F1 Angus x Charolais, F1 Brahman x Hereford, and F1 Brahman x Angus breed types were evaluated from birth until 10 yr of age. Of 308 females born alive, 35.7% died or were culled because of injury, serious illness, or reproductive failure. Breed types differed (P less than .01) in total number of mating seasons per cow and total number of progeny born and weaned. Values for lifetime total number of calves weaned were as follows: Hereford, 4.54; Red Poll, 5.45; Hereford x Red Poll, 4.45; Red Poll x Hereford, 5.49; Angus x Hereford, 5.98; Angus x Charolais, 5.57; Brahman x Hereford, 6.96; and Brahman x Angus, 6.22. Brahman crosses (P less than .01) and Angus x Charolais (P less than .10) exceeded Hereford dams in lifetime total number of calves weaned but did not differ from Angus x Herefords. Analysis of the Hereford-Red Poll diallel showed no evidence of heterosis in life span traits. Results indicate that breed type was a major source of variation in reproductive life span of beef-type females. F1 Bos indicus crosses and Angus x Herefords were outstanding in longevity.  相似文献   

20.
Mature dams representing Hereford, Red Poll, F1 Hereford x Red Poll, F1 Red Poll x Hereford, F1 Angus x Hereford, F1 Angus x Charolais, F1 Brahman x Hereford and F1 Brahman x Angus breed types were evaluated. All cows were bred to Limousin sires to produce two-way or three-way-cross progeny. Mature Brahman x Hereford dams produced a higher (P less than .05) percentage of live calves than Herefords, but dam breed differences in percentage of calves weaned relative to the number of cows exposed for mating were not statistically significant. Progeny of Angus x Charolais and Red Poll dams were outstanding in weaning weight, but Hereford and Brahman-cross calves were below average. Planned comparisons showed that Angus x Charolais calves were heavier (P less than .01) at weaning than Hereford (23.0 +/- 3.8 kg) or Angus x Hereford (9.6 +/- 3.2 kg) progeny. Mature Angus x Hereford mothers weaned heavier calves than did Brahman x Herefords (7.4 +/- 3.2 kg, P less than .05) or Brahman x Angus (10.9 +/- 3.0 kg, P less than .01). Analysis of the Hereford-Red Poll diallel showed evidence of maternal heterosis in calf weaning weight (4.0 +/- 2.6 kg, P less than .05), but there was no difference in the percentage of calves weaned by crossbred vs straightbred dams.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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