Measurements at calving for straightbred and crossbred cows of diverse types

Reproductive and calving records of 611 cows from F1 and F2 generations from a diallel mating system with Angus, Brahman, Hereford, Holstein and Jersey were examined. The inter se matings were by artificial insemination, and each cow had three or four parturitions. Dependent variables included weight, hip weight at first calving, age at first calving, gestation length and calving interval. Brahmans were the heaviest, tallest and oldest purebred at first calving. Crossbred Brahman females tended to be older than other crosses at first calving. Purebred Brahmans and one-half Brahman crosses also had the longest gestation lengths and calving intervals. First-gestation (F1) crossbred cows were 18 kg heavier (P less than .05), 2.0 cm taller (P less than .01) and 35 d younger (P less than .05) at first calving than contemporary straightbreds. Average maternal heterosis for height at calving was significant (1.4 cm; P less than .05); however, estimates of specific and average maternal heterosis for measurements taken at first calving were generally nonsignificant. Estimates of specific and average individual and maternal heterosis were generally small and nonsignificant for gestation length and calving interval.     

Production characters of first-generation cows of a five-breed diallel: reproduction of young cows and preweaning performance of inter se calves

Data from cows of a five-breed diallel involving Angus, Brahman, Hereford, Holstein and Jersey were analyzed. Females were used in inter se matings to produce three second-generation parturitions per cow. Crossbred (CB) cows were 43 d younger (P less than .05), 14 kg heavier (P less than .05) and 2 cm taller (P less than .05) at first calving than straightbred (SB) cows; however, no differences were detected (P greater than .10) between the two groups for pelvic measurements. Although large differences among breed types existed for gestation length, crossbreds generally did not differ from straightbreds for this character. Crossbred cows exhibited a 7.5 d shorter (P less than .05) interval from parturition to first service, but did not exhibit a shorter interval from parturition to conception (P greater than .10). The dairy breeds (Holstein and Jersey) and their crosses exhibited similar postpartum and calving intervals as Angus, while Brahman and their crosses had longer intervals. Crossbred calves were 1.3 kg heavier (P less than .01) and had greater (P less than .01) shoulder and hip dimensions at birth than SB calves, but no difference in the amount of calving difficulty was detected (P greater than .10) between the two groups. Higher (P less than .01) rates of survival to 24 h (3.7%) and to weaning (8.7%) were observed for CB calves compared with SB calves. Heterotic effects for weaning weight (15.2 kg), weaning height (2 cm) and preweaning average daily gain (68 g) were large and illustrate the importance of individual and maternal heterosis for these characters. These results suggest that substantial amounts of heterosis may be retained for survival and weaning characters of calves in early generations of inter se mating of CB.     

Heterosis retention for birth and weaning characters of calves in the third generation of a five-breed diallel.

Data were 876 birth records and 727 weaning records of straightbred and F3 crossbred calves produced in the third generation of a five-breed diallel. Among straightbreds at birth, Holstein calves were heaviest and widest at the shoulders and hips. Jersey calves were lightest and narrowest at the hips, and Brahman calves were narrowest at the shoulders. Holstein crosses tended to be larger at birth than crosses among other breeds. Among straightbreds at weaning, Holstein calves were heaviest and tallest, and Hereford calves were lightest and shortest. Angus calves had the highest survival to weaning rate, and Holstein calves had the lowest survival rate. Among crossbred calves, Holstein crosses tended to be larger at weaning. Estimates of average heterosis retained for birth characters were not significant. Significant breed mean heterosis retention was observed for birth weight, shoulder width, and hip width of Hereford calves and for shoulder width and hip width of Holstein calves. Estimates of average heterosis retained for weaning weight and height were 6.1 kg (P less than .01) and 1.02 cm (P less than .05), respectively. In general, estimates of specific and average heterosis retained for survival to weaning were nonsignificant. Significant breed mean heterosis was observed for weaning weight and height of Brahman, Hereford, and Holstein calves and for survival to weaning of Hereford, Holstein, and Jersey calves.     

Genotype x environment interactions involving proportion of Brahman breeding and season of birth. II. Postweaning growth, sexual development and reproductive performance of heifers

Postweaning growth, sexual development and reproductive traits were evaluated over a 3-yr period on 201 spring-born and 180 fall-born crossbred heifers with 0, 1/4 or 1/2 Brahman breeding. The proportion of Brahman breeding X season of birth interaction was significant for five traits (average daily gain weaning to yearling, yearling condition score, percentage of heifers detected in estrus, prebreeding condition score and percentage of heifers that became pregnant) and was not significant for six traits (yearling weight, hip height and conformation score, age and weight at puberty and prebreeding weight. Among spring-born heifers, 1/4 and 1/2 Brahman heifers outgained (P less than .05) 0 Brahman heifers from weaning to yearling by 50 and 66 g/d, respectively; among fall-born heifers, 1/4 and 1/2 Brahman heifers outgained (P less than .05) 0 Brahman heifers by 41 and 104 g/d, respectively. Yearling weight of 1/2 Brahman heifers was 13 and 10 kg heavier (P less than .05), respectively, than 0 and 1/4 Brahman heifers. Yearling hip height of 1/4 and 1/2 Brahman heifers were 1.9 and 5.7 cm taller (P less than .05), respectively, than 0 Brahman heifers. Weight prior to the start of the breeding season were similar among crossbred heifer groups and spring-born heifers were 66 kg heavier (P less than .05) than fall-born heifers. The percentage of heifers that became pregnant was similar among spring-born crossbred heifer groups, whereas among fall-born heifer groups 1/4 and 1/2 Brahman heifers were 25.2 and 49.4 percentage points lower (P less than .05), respectively, than 0 Brahman heifers.     

Comparison of cattle of a five-breed diallel: size, growth, condition and pubertal characters of second-generation heifers

Monthly weights, heights and condition scores and measurements taken at the time of puberty were utilized to estimate effects of breed-type and heterosis on characters related to growth, size and puberty of second-generation heifers of a five-breed diallel involving Angus, Brahman, Hereford, Holstein and Jersey. One group of heifers was maintained on pasture with supplemental feed; two other groups were fed in individual pens starting at weaning and 1 yr of age, respectively. A model including main effects of breed-type, sire within breed-type, management, parity of dam and birth-season was used for analyzing all characters. Breed-type tested with sire within breed-type was significant for all characters except ADG from 360 to 450 d. Straightbred and crossbred means were larger for the second generation than for the first, presumably due to management and(or) year effects. Heterosis generally was positive and, when expressed as a percentage, decreased with age, which is in agreement with other research reports. Holsteins and Brahmans were largest for growth and size characters, whereas Jerseys were smallest. Jerseys were the youngest, lightest and shortest at puberty, whereas Brahmans were oldest, heaviest and tallest.     

Two-, three- and four-breed rotational crossbreeding of beef cattle: reproductive traits

Reproductive data were collected on 4,596 cow exposures in a rotational crossbreeding study that spanned four generations (1970 through 1988). Angus (A), Brahman (B), Charolais (C) and Hereford (H) breeds were included in three two-breed (A-B, C-B and H-B), three three-breed (A-B-C, A-B-H and C-H-B) and one four-breed (A-B-C-H) rotational mating system. Contemporary straightbreds were produced each generation. Reproductive traits of interest were calving rate, calf survival, weaning rate, calf birth date and calving assistance. Overall means and standard errors for calving rate, calf survival, weaning rate, calf birth date and calving assistance were 82.1 +/- .6%, 92.8 +/- .4%, 76.2 +/- .6%, 50.4 +/- .3 d and 4.2 +/- .3%, respectively. Rotational mating systems had similar calving and calf survival rates that were greater (P less than .01) than those of straightbreds. Three- and four-breed rotation systems had similar weaning rates (81.5 +/- 1.1 and 80.8 +/- 2.0%) that were higher than those for two-breed rotations (77.1 +/- 1.2%). Two- and three-breed rotation systems had fewer assisted births (3.5 +/- .6 and 2.2 +/- .6%) than straightbreds (5.5 +/- .6%) and the four-breed rotation (5.4 +/- 1.0%). Three-breed rotation calves were born earlier in the calving season (46.8 +/- .6 d; P less than .05) than straightbred, two-breed or four-breed rotation calves (51.8 +/- .6, 52.1 +/- .6 and 51.1 +/- 1.0 d). Hereford-Brahman two-breed rotation cows had higher (P less than .05) calving and weaning rates than A-B or C-B two-breed rotation cows (87 +/- .4 vs 81.9 +/- 1.9 and 81.5 +/- 1.8%; 81.7 +/- 2.0 vs 76.4 +/- 2.1 and 74.1 +/- 2.0%). All three-breed rotation combinations had similar calving, calf survival and weaning rates, assistance at calving and calf birth dates. Rotational combinations tended to be more superior (P less than .05) to weighted purebred means for calving, calf survival and weaning rates than for calf birth date and calving assistance.     

Factors affecting the relationship between calving interval of cows and weaning weights of calves

Characters related to production and reproduction were observed on 744 straightbred and F2 calves and their dams produced in a five-breed diallel with Angus, Brahman, Hereford, Holstein and Jersey breeds. These data were analyzed to estimate the effects of these characters on the relationship between weaning weight and calving interval. The model used for analysis of postpartum conception and calving interval included breedtype, season of conception, parity and management of the dam as main effects; condition of dam nested within parity; and age, weight and weight change of dam and weaning weight of previous calf as covariates. All effects and covariates were significant sources of variation in conception and calving interval. Brahman cows exhibited the longest conception and calving intervals, whereas Hereford X Jersey F1 cows had the shortest intervals. Heterotic effects for these intervals were low and nonsignificant. Weaning weight of the previous calf was positively correlated with postpartum conception and calving interval, but to determine the magnitude of the relationship the need to adjust for differences in breedtype, condition, parity, early management, age, weight and weight change of the dam was apparent.     

Characterization of straightbred and crossbred rabbits for milk production and associative traits

Two hundred twenty-five lactation and litter performance records from 82 does representing four genetic groups and two diets were analyzed to quantify breed, heterosis, reciprocal F1 cross and diet effects for milk production and associative traits. Doe genetic groups were New Zealand White (NN) and Californian (CC) straightbred and Californian X New Zealand White (CN) and New Zealand White X Californian (NC) reciprocal crossbreds. Pelleted diets fed to does and litters were either a commercial control or a 74% alfalfa diet. Three sire breeds of litters included NN, CC and Flemish Giant (FG) straightbreds. Doe genetic group and diet were important sources of variation (P less than .05) for all traits examined except for litter milk efficiency (litter gain/milk intake) and doe feed efficiency (milk yield/feed intake). The sire breed of litter effect did not influence (P greater than .05) lactational performance of does nor associative preweaning traits. Straightbred NN does were heavier at kindling, yielded more milk, reared a heavier litter by 21 d and were more efficient in converting feed into milk than were straightbred CC does (P less than .01). Significant heterosis was detected for milk production and for litter size and weight at 21 d. Reciprocal differences between crossbred doe groups were observed (P less than .05) for litter milk efficiency and doe feed intake. The 74% alfalfa diet was superior to the commercial control diet for effects on milk production and litter size and weight at 21 d, although doe feed intake was increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production characters of first generation cows of a five-breed diallel: reproduction of mature cows and preweaning performance of calves by two third-breed sires

The fourth through sixth parity of 5- to 10-yr-old cows were used to evaluate trade-offs involved with sires of large mature size vs medium mature size in a terminal sire crossbreeding program and to characterize five breeds and their crosses for their potential as dam lines. Charolais and Red Poll bulls, representing large (L) and medium (M) mature size, respectively, were mated to cows representing Angus (An), Brahman (Br), Hereford (He), Holstein (Ho) and Jersey (Je) and their crosses (reciprocals pooled). Cows were randomly assigned for mating to either an L or M bull for each breeding. Size of calf sire did not influence (P greater than .10) the subsequent calving interval of cows. Calving intervals for the straightbred (SB) dairy breeds (Ho and Je) were longer than for SB An and He, but the difference did not exist among the respective crossbred (CB) cows. As a group, Br crosses had shorter intervals than the other CB groups. Crossbred cows exhibited intervals that were 16 d shorter (P less than .05) than SB. Calves sired by L bulls were larger (P less than .01) and faster gaining (P less than .01) for all measures of size and growth studied, but exhibited lower (P less than .01) survival rates to weaning than M-sired calves. Calves of CB dams were 1.5 kg heavier (P less than .01) at birth than calves of SB dams and slightly greater (nonsignificant) hip and shoulder measurements were observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Time of zeranol implantation on growth, reproduction and calving of beef heifers

Zeranol implants were administered to 250 crossbred heifer calves at 1, 6 or 9 mo of age to evaluate growth, reproduction and calving performance. Heifers were assigned to eight treatment groups with 25 animals per group. Two additional groups of 25 heifers each were used to study the effects of multiple implants at two levels of nutrition on heifer performance. Implants at 1 mo of age (branding) increased heifer weights at 6 mo of age (weaning) by 5 kg (P = .08). Heifers receiving a combination of two implants gained faster (P less than .05) from weaning to breeding (6 to 13 mo) than controls or heifers implanted three times. Implants at either 6 or 9 mo increased (P less than .05) precalving pelvic areas (247 vs 241 cm2 and 248 vs 240 cm2 over controls, respectively). Implants did not affect the percent of heifers reaching puberty prior to breeding season. Conception rates in 62 d of breeding were comparable for implanted and control heifers (93 vs 96%), with the exception of heifers receiving implants at both 1 and 6 mo of age (56%). Calf birth weight, dystocia score, cow rebreeding rate and calf weaning weight were not affected by implant treatments. Heifers that received three implants and were fed at a high nutritional level (gained .62 vs .49 kg/d for regular level after weaning) tended (P greater than .10) to reach puberty at a higher rate prior to breeding and to have a higher total conception rate than implanted heifers on the regular nutrition level.     

Effect of selection for growth traits on age and weight at puberty in bovine females

This 20-yr study, using 584 beef heifers born in the spring of 1984 or 1985, was conducted to determine whether selection for growth traits affected age and weight at puberty. Heifers were from three Hereford lines selected for weaning weight, final weight, and final weight plus muscling score, a control line and a line of Angus cattle. In addition, heifers from reciprocal crosses among the selection lines, control and Angus groups were evaluated. Intact bulls and androgenized heifers fitted with marking harnesses were used to aid in detection of estrus for heifers born in 1984 and 1985, respectively. The time of puberty was identified by the first behavioral estrus. During both years, heifers were weighed at 56-d intervals; these weights were used to calculate weight at puberty. Mean age at puberty was determined using survival analysis; percentages of heifers that were pubertal by the end of the study were transformed to logits for analysis. Heifers born in 1985 were heavier (P less than .05) at puberty than those born in 1984. Heifers in lines selected for growth traits were younger at puberty (P less than .05; 20 d) than were heifers in the control line because of combined direct and maternal genetic effects. Heifers from the final weight, control (P less than .05) and weaning weight lines (P less than .10) weighed less at puberty than Angus heifers; selection line x Angus crossbred heifers were heavier at puberty (P less than .05) than their respective pureline or purebred contemporaries due to heterotic effects. Selection for weaning weight, final weight or final weight plus muscling score did not have a detrimental effect on age at puberty in heifers.     

Productive longevity of first-cross cows produced in a five-breed diallel: I. Reasons for removal

Data from 498 cows of 15 breed-types produced in a five-breed diallel (reciprocals pooled) including Angus, Brahman, Hereford, Holstein and Jersey were analyzed for differences in productive longevity, mean life span and reasons for removal from the herd over approximately 14 yr. The only culling related to production was of cows that did not give birth to at least one live calf every 24 mo. Otherwise, cows were only removed when they appeared to be incapable of weaning another live calf. The average age at removal, estimated from linear regression, was 3,470 d, with values ranging from 2,174 d (Jersey) to 4,087 d (Angus-Brahman). Longevity of crossbred cows was greater than that of purebred cows (P less than .001). Purebred cows usually had higher initial rates of removal than crossbred cows. Estimates of mean longevity from the nonlinear regression resembled the results of the linear regression analysis; mean life spans ranged from 6.2 yr (Jersey) to 14.6 yr (Angus-Brahman). The major reason for removal of Brahman and Brahman-cross cows was for reproductive reasons. Angus and Angus-cross cows were culled more frequently for structural unsoundness; Hereford cows had a higher incidence of cancer eye, calving difficulty and mammary problems; cows with 100% dairy breeding had exceptionally high susceptibility to diseases and mineral imbalance.     

Production characters of straightbred, F1 and F2 cows: birth and weaning characters of terminal-cross calves

Records of 2,449 births and 2,120 weanings of terminal-cross calves were used to characterize maternal productivity of first- and second-generation cows from a diallel of Angus, Brahman, Hereford, Holstein and Jersey when mated to third-breed sires. Third- and later-parity cows were randomly assigned after each parturition to Charolais and Red Poll bulls in multiple-sire pastures. Calves were weaned at approximately 7 mo of age; males were not castrated. A mixed model was assumed for data analysis. Effects included in the model were breed-type of dam, cow within breed-type of dam (random), breed of sire of calf, season of record, year of record, age of dam group, sex of calf and age of calf (covariate). Age of dam groups were 4- and 5-yr-olds, 6- and 7-yr-olds, 8-, 9- and 10-yr-olds, and those greater than 10 yr of age. Dependent variables were calf weight, shoulder width and hip width at birth, weaning weight, weaning height and survival to weaning. Holstein and Holstein crosses tended to produce the largest calves at birth and weaning. Among straightbred dams, the smallest calves were born to Brahman, whereas Hereford weaned the smallest calves. Brahman-Jersey dams produced the smallest calves at birth among crossbreds; Angus-Hereford cows weaned the smallest calves. Average maternal heterosis estimates for birth weight were small and non-significant. Calves of F1 crossbred dams were 17.4 kg heavier (P less than .01) and 1.70 cm taller (P less than .01) at weaning than calves of first-generation straightbred dams.(ABSTRACT TRUNCATED AT 250 WORDS)     

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)     

Comparison of crossbred cows containing various proportions of Brahman in spring- or fall-calving systems: IV. Effects of genotype x environment interaction on lifetime productivity of young cows.

Lifetime productivity of young (2 to 6-yr-old) crossbred cows containing various proportions (0, 1/4, or 1/2) of Braham breeding was evaluated using 188 spring-calving and 154 fall-calving cows. Cows were mated to Limousin sires to produce 1983 through 1986 calf crops. The 1987 calf crops were produced using Limousin and Salers sires. Significant (P less than .10) genotype (crossbred cow group) x environment (season of calving) interactions were found for age at first calf and lifetime calving percentage and mature cow weight. Within the spring calving group, no differences were found between crossbred groups for age at first calf or lifetime calving percentage. However, within the fall-calving group, 0 and 1/2 Braham cows from Angus dams calved earlier than did those from Hereford dams. Age at first calf also tended to increase as proportion of Brahman increased in the fall-calving group. Within the fall-calving group, lifetime calving percentage for 0 and 1/2 Brahman cows from Hereford dams was lower than for those from Angus dams. The opposite was true for the 1/4 Braham crosses. In general, as the proportion of Brahman breeding increased, productivity, measured as weight per calf or weight weaned per year, increased; however, age at first calving increased also as proportion of Brahman increased. All spring-calving groups calved earlier in life (P less than .05) than their respective fall-calving counterparts and with the exception of the 0 Brahman groups, which were similar, spring-calving groups produced a higher (P less than .05) percentage of calves than did the fall groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Crossing beef x beef and beef x Brown Swiss: pregnancy rate, calf survival, weaning age and rate

October pregnancy rate, calf survival to weaning, weaning age, weaning rate and actual kg of calf weaned/cow exposed were determined in a 4-yr study involving 880 matings of Angus (A), Hereford (H) and Charolais (C) sires to A, H, C and Brown Swiss (BS) dams. Cows were mated in single-sire herds for 45 or 60 d under pasture conditions; heifers were bred to produce their first calf at 3 yr of age. Pregnancy rate of lactating dams was 9.4% higher (P less than .01) than for non-lactating dams. Pregnancy rates for straightbred matings were 87.5%, 80.6% and 75.4%, respectively, for A, H and C groups (P less than .05). No differences (P greater than .10) due to sire breed were found for any of the traits studied except for calf age at weaning. Calves from C sires were younger (P less than .01) at weaning than calves from H and A sires. Breed-of-dam differences (P less than .05 to P less than .01) were found for all traits studied except calf survival rate. All BS dams produced crossbred calves and had lower pregnancy and weaning rates (both P less than .01), calves were younger at weaning (P less than .05), had lower kg of calf weaned/cow exposed (P less than .05) than for beef-breed dams producing crossbred calves. Crossbred calves from BS dams were 4.9, 11.0 and 3.4 d younger (P less than .05 to P less than .01) at weaning, respectively, than crossbred calves from H, A and C dams.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maternal heterosis and grandmaternal effects in beef cattle: preweaning traits

Crossbred progeny from females, 3 yr old and older, representing Brown Swiss (B), Red Poll (R), Hereford (H) and Angus (A) maternal grandsires and maternal granddams in a diallel crossing experiment were evaluated to estimate breed mean maternal heterosis (mean hMi) for each breed, maternal heterosis for specific breed cross females (hMij), average maternal heterosis for all crosses (mean hM) and breed grandmaternal effects (gM'i) for preweaning calf traits. Estimates of mean hM were significant for birth date and weight, 200-d weight and 200-d weight/cow exposed. Even though calves with crossbred dams weighed more at birth, they did not differ from calves with straightbred dams in frequency of calving assistance. The estimates of hMij were similar for most crosses and most traits, except 200-d weight and 200-d weight/cow exposed. The largest heterotic advantage was exhibited by progeny of BH reciprocal cross females, which exceeded crossbred progeny from BB and HH females for 200-d weight/cow exposed by 35.9 kg. The smallest heterotic effect was exhibited by crossbred progeny of RA reciprocal cross females. Progeny with R maternal granddams exhibited a higher (P less than .05) live calf born and weaned percentage than progeny with H maternal granddams. Progeny with B maternal granddams were born later (P less than .05) in the calving season than progeny with R maternal granddams. Progeny with A maternal granddams exhibited a lower frequency of calving assistance than progeny with H maternal granddams, and progeny with H maternal granddams were heavier (P less than .05) at 200 d than progeny with R maternal granddams. There was a tendency for estimates of breed grandmaternal effects (gMi) to exhibit an inverse relationship with estimates of breed maternal effects (gMi).     

Relationship between haemoglobin types and productivity of Thai indigenous and Simmental × Brahman crossbred cattle

The relationship between the haemoglobin (Hb) type and reproduction and body weight was estimated in two different cattle breeds including 59 Thai indigenous and 51 Simmental × Brahman crossbred cows. Haemoglobin type was measured using cellulose acetate electrophoresis. Five haemoglobin types were present in indigenous cattle: HbAA (35.59%), HbAB (28.81%), HbAC (20.34%), HbBB (11.6%) and HbBC (3.39%). In the Simmental × Brahman crossbred cattle, three haemoglobin types, 50.98% HbAA, 45.10% HbAB and 3.92% HbBB, were present. The results revealed that Thai indigenous cows with HbAB type were heavier at birth, however, the best growth performance was recorded in HbAC animals. In contrast, calves carrying HbBB type were the lightest animals at birth and were the youngest group at first calving. This group of Thai indigenous cows was more than 4 months younger at first calving than the heifers with HbAA type. Simmental × Brahman crossbred cows with HbAA type were significantly (P < 0.05) heavier than the animals with HbAB type at birth as well as on days 200, 400 and 600 of age. Whereas, the animals with HbAB type gave birth to their first calf at a significantly (P < 0.05) younger age than those with HbAA type.     

Influence of genotype and yield and composition of milk on interval to first postpartum ovulation in milked beef and dairy cows.

Our objectives were to investigate the effects of genotype, yield and composition of milk, and changes in BW and body condition on the initiation of cyclic ovarian activity in nonsuckled beef and dairy cows milked twice daily. Nulliparous heifers were selected from three breeds, 12 Angus, 13 Simmentals, and 26 Holsteins, based on their EBV for milk yield. Cows were machine-milked twice daily, and daily milk yield was recorded; composite samples of milk were collected twice weekly for analyses of milk components. Blood was collected from all cows thrice weekly for 75 d postpartum, and concentrations of progesterone in serum measured by RIA were used to estimate day of first postpartum ovulation. Holstein cows produced more (P less than .05) milk (unadjusted or 3.5% fat-corrected) than Angus or Simmental cows during the first 30 d of lactation. Holstein cows had higher (P less than .01) peak yield of milk than Simmental and Angus cows. Days to peak milk yield were similar for Simmental and Holstein cows, and both were more (P less than .05) than those for Angus cows. Percentages of fat, protein, and total solids in milk were highest (P less than .05) for Simmental cows, whereas milk of Holstein cows had the highest (P less than .05) percentage of lactose and lowest (P less than .05) concentration of somatic cells. Average BW at ovulation differed (P less than .05) among breeds. Estimated daily changes in BW from calving to first ovulation were different (P less than .05) for Holstein and Simmental cows but were similar to those of Angus cows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine corpus luteum regression and estrous response following treatment with alfaprostol

Two trials evaluated bovine corpus luteum (CL) regression and estrous response following treatment with alfaprostol (AP), a prostaglandin F2 alpha analogue. Expression of at least one estrous cycle (16 to 26 d) and a palpable mid-cycle CL were required prior to random assignment of females to receive 0, .38, .75, 1.50 or 2.25 mg AP/100 kg body weight. Alfaprostol was evaluated in Brahman cows and heifers that were treated on d 11 to 13 (trial 1) and in Simmental X Brahman-Hereford (crossbred) heifers that were treated on d 8 to 10 or d 11 to 13 of the estrous cycle (trial 2). In trial 1, Brahman heifers appeared to require a higher AP dose (greater than .38 mg/100 kg body weight) to elicit luteolysis and expression of estrus than Brahman cows. Alfaprostol treatment (greater than or equal to .75 mg/100 kg body weight) induced (P less than .0001) luteolysis followed by estrus in Brahman cows and heifers. In trial 2, crossbred heifers that received AP on d 8 to 10 appeared to require a higher dose of AP (greater than .38 mg/100 kg body weight) to elicit luteolysis and estrus than heifers that received AP on d 11 to 13 of the estrous cycle. Alfaprostol treatment greater than or equal to .75 mg/100 kg body weight on d 8 to 10 and d 11 to 13 of the estrous cycle induced (P less than .0001) luteolysis followed by estrus in crossbred heifers.(ABSTRACT TRUNCATED AT 250 WORDS)