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1.
R E Sacco J F Baker T C Cartwright C R Long J O Sanders 《Journal of animal science》1989,67(8):1972-1979
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) 相似文献
2.
Maternal performance of 134 Hereford (H), Brangus (B), and reciprocal crossbred (H x B and B x H) cows from 2 to 7 yr of age was evaluated under semidesert conditions in this study. Calves produced by 2- and 3-yr-old cows were sired by Brangus and Hereford bulls. Calves produced by 4- to 7-yr-old cows were sired by Charolais bulls. Breed of sire and breed of dam of cow affected kilograms of weaning weight, 205-d weight, weaning weight as a percentage of cow weight, and 205-d weight as a percentage of cow weight produced annually. Brangus (either as sire or dam of cow) was superior to Hereford in all cases. Observed maternal heterosis on 2- to 3-yr-old cows was 23.0, 20.1, 30.0, 29.1, 23.9, and 23.0% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Observed maternal heterosis from mature cows was 19.8, 12.8, 21.0, 18.7, 17.4, and 15.4% for calf birth date, weaning percentage, weaning weight per year, 205-d weight per year, weaning weight as a percentage of cow weight per year, and 205-d weight as a percentage of cow weight per year, respectively (P less than .01). Results indicate large heterotic effects on annual cow productivity and an adaptive advantage for cows with Brangus sires and(or) dams under semidesert conditions. 相似文献
3.
Angus (A), Santa Gertrudis (S), and Gelbvieh (G) sires were mated to A and S dams to produce five mating types (A X A, S X S, S X A, A X S and G X A) in each of four calf crops. The study involved 501 matings. Overall means for the traits measured (calves born/cows exposed, Julian birthdate, calving ease, percentage of live calves at 24 h, birth weight, survival to weaning and gestation length) were 74.2%, 48.8 d, 96.4%, 33.2 kg, 95.4% and 283.8 d, respectively. Angus dams had a 14 percentage point (P less than .05) advantage over S dams for percentage of calves born/cows exposed. The effect of heterosis in crosses of A and S for percentage of calves born/cows exposed was negative (-11.1%) and approached significance. The percentage of calves born/cows exposed were 84.4, 70.4, 76.1 and 62.3 for the A X A, S X S, S X A and A X S mating types, respectively. Matings involving A sires and dams produced calves significantly earlier in the calving season than did matings involving S sires and dams. Matings involving S sires and dams produced calves with significantly longer gestation periods than matings of A sires and dams. Calving ease score and survival to weaning were not affected by breed of sire, breed of dam, age of dam, sex of calf, or the interaction of breed of sire X breed of dam. Percentage of live calves at 24 h indicated that straightbred S calves were significantly less viable at birth than the other four mating types.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
《Livestock Production Science》1993,33(1-2):55-66
Angus (A), Hereford (H), Jersey (J), Simmental (S) and Brahman (B) bulls (202), were mated to A and H cows (855 cow-years) to produce F1 calves. Cows were randomly assigned within age and breed to two pasture programs. The two pasture programs were expected to differ in particular with respect to the energy level offered to the cows during winter (tall fescue hay versus corn silage). Effects of genotypes, pasture program and of their interactions on preweaning traits were studied. Differences (P< 0.05) between pasture programs were found only for frame and muscle scores. Marginal means for A dams were higher (P<0.05) than those for H cows for all traits, except birth weight. Calves sired by B bulls were heavier (P<0.01) at birth than those sired by S, A and H, and J bulls. For the other traits, S-sired calves tended to have the largest estimated means, followed by calves of B bulls, then by the average of calves sired by A and H bulls and finally by J-sired offspring. Significant (P< 0.05) breed of sire × breed of dam interactions involved only extreme sire breeds. All hypotheses involving pasture program × breed of sire interactions were not significant. Muscle score was the only trait affected (P< 0.05) by a pasture × breed of dam interaction. However, its effect was only magnitudinal. Birth weight was the only trait not affected at all by the pasture program × breed of sire × breed of dam interaction. In the other traits, significant interactions reflected changes in the magnitude of the response rather than in the ranking of genotypes across pasture programs. 相似文献
5.
The performance of 264 contemporary 2-yr-old straightbred and crossbred dams during 1978 to 1981 was studied and maternal heterosis was estimated. Dam breed groups were Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H). Differences among dam breed groups were nonsignificant for length of gestation, calving difficulty and late milk production but were important (P less than .01) for calf weights (birth, early and late milking periods and weaning), calf average daily gains during various intervals from conception to weaning, early milk production and other calf traits at weaning (height, weight/height and visual condition score). Dam breed group means (HH, AH, 1S3H, 1S1H and 3S1H, respectively) for representative calf traits were .37, .39, .39, .42 and .42 kg/d for estimated average daily gain the last 3 mo of gestation; 33.6, 34.7, 35.7, 37.6 and 37.1 kg for birth weight; 191, 205, 209, 228 and 228 kg for weaning and 7.5, 8.4, 8.3, 9.5 and 10.0 kg for 24-h early milk production. Therefore, 2-yr-old crossbred dams raised calves that were generally larger for the preweaning gain traits than HH dams. Differences among dam breed groups were significant for traits involving reproduction; means (HH, AH, 1S3H, 1S1H and 3S1H, respectively) were .58, .92, .72, .91 and .79 for proportion calving and 105, 179, 126, 182 and 154 kg for actual calf weaning weight per cow exposed to breeding. Estimates of percentage maternal heterosis were 6.3, 12.9, 9.0 and 7.6% for calf weights at birth, 40 d, 130 d and weaning, respectively; 1.8, 5.7 and 5.7% for calf hip height, height/weight and condition score at weaning, respectively; and 43.1 and 34.6% for proportion calving and actual calf weaning weight per cow exposed to breeding. The dominance model explained most (greater than 95%) of the variation observed among dam breed group means for most traits. 相似文献
6.
Records of Jersey-sired (Jx), Santa Gertrudis-sired (Sx), Charolais-sired (Cx) and straightbred Hereford (H) cows were examined to determine culling rates, birth dates, weaning weights and average daily gains of their first, second and third calves. Culling categories were defined on the basis of number of calves weaned before removal from the herd. Calf performance data were analyzed by cow breed group and cow culling category. A second-degree polynomial model fit the data of all breeds, and accounted for a greater proportion of variation in percentage culled than did the linear model (P less than .05). Total percentage culled through the study were 71, 67, 54 and 53 for the H, Sx, Cx and Jx cows, respectively. Culling rates in the H and Sx cows tended to be higher at earlier ages than in the Cx and Jx cows. Cow-culling category was a significant source of variation only on birth date of first calves. Cows culled after one calf had calves that were born later than cows in the other two categories (P less than .05). Birth date, weaning weight and average daily gain of first calves varied with cow breed in that Jx cows had calves that were born earlier, gained faster and weaned heavier than first calves from the other breed groups (P less than .05). First calves from Sx and Cx cows gained faster (P less than .05) than calves from H cows.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
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
8.
Growth patterns from birth to maturity were compared for 92 straightbred Herefords (H) and 299 Hereford crossbred (XB) cows. Crossbred cows were out of Hereford dams and were sired by bulls of two British [Angus (A) and Shorthorn (Sh)], two Continental [Charolais (C) and Simmental (S)] and two American dairy breeds [Brown Swiss (B) and Holstein (F)]. British XB and H cows differed only slightly in weight but both weighed less than Continental and dairy XB cows. Body condition also differed significantly among breed types; dairy XB were thinnest. Among XB individuals SH calves were heaviest (34 kg) and AH calves were lightest (30 kg) at birth. Birth weights of Continental XB were 2.6 kg more than those of British XB and 1.7 kg more than those of dairy XB. At weaning, all XB calves were heavier than straightbred H calves, but differences among XB types were not significant. However, on the average, Continental XB and dairy XB calves were heavier (28 kg) than British XB at 19 mo. At 32 mo, Continental and dairy XB weighed 41 and 23 kg more, respectively, than British XB. Although differences between the British XB and the Continental and dairy XB at some ages were not significant, no case existed where the latter two groups weighed less than British XB. Adjusting weight to a common condition score reduced phenotypic variance at all ages and changed the ranking of some breed types for weight, primarily by increasing predicted weights of dairy XB. Differences in growth curves were reflected by differences in mature weight and maturing rate. Asymptotic weights of Continental XB were highest, followed by those of dairy XB. British XB and H weighed least at maturity (average of 509 kg). The CH cows matured more slowly but grew to a heavier mature weight (592 kg) than SH cows (552 kg). Generally animals reached 95% of their mature weight between 68 and 80 mo of age. 相似文献
9.
Measures of maternal productivity and reproduction of Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H) dams were studied. Half of each dam breed group was bred to Tartentaise and half to Charolais sires to produce 706 calves at weaning from 930 exposures to breeding in a Montana range environment. Data were analyzed according to a model that included the fixed effects of year, dam breed group, dam age, calf sex, calf sire breed, plus appropriate two-way interactions, linear partial regression on calf birth date and random effects of sire within dam breed group (maternal grandsire of the calf) and sire within calf sire breed. Calf sex interacted with calf sire breed for several traits, but interactions were due to changes of magnitude of differences between sexes. There were no significant interactions of dam breed group with other main effects for calf growth traits, except for the interaction with calf sire breed for some calf growth traits. This interaction was due to a change in magnitude; it suggested that larger sire breeds should be matched to larger dam breeds with greater potential for milk production. The only significant interaction for traits that included reproduction of the dam was dam breed group X age of dam. Ranking of dam breed groups depended on age at measurement. Differences among dam breed groups were significant for most traits. Calf weaning weights for HH, AH, 1S3H, 1S1H and 3S1H dams were 211, 223, 227, 237 and 243 kg, respectively; calf weaning weights per cow exposed were 157, 163, 179, 189 and 169 kg; calf weaning weights per unit of dam weight were .40, .41, .43, .44 and .42, respectively. Thus, dam breed groups that weaned the largest calves were not necessarily the most productive under Montana range conditions. 相似文献
10.
The objectives of this study were to determine if percentage Bos taurus (0 or 50%) of the cow had an effect on ME requirements and milk production, and to compare cow/calf efficiency among 3 mating systems. Metabolizable energy requirements were estimated during a feeding trial that encompassed a gestation and lactation feeding trial for each of 2 groups of cows. Cows were 0 or 50% Bos taurus (100 or 50% Nellore) breed type: Nellore cows (NL; n = 10) mated to Nellore bulls, NL cows (n = 9) mated to Angus bulls, Angus x Nellore (ANL; n = 10) and Simmental x Nellore (SNL; n = 10) cows mated to Canchim (5/8 Charolais 3/8 Zebu) bulls. Cows were individually fed a total mixed diet that contained 11.3% CP and 2.23 Mcal of ME/kg of DM. At 14-d intervals, cows and calves were weighed and the amount of DM was adjusted to keep shrunk BW and BCS of cows constant. Beginning at 38 d of age, corn silage was available to calves ad libitum. Milk production at 42, 98, 126, and 180 d postpartum was measured using the weigh-suckle-weigh technique. At 190 d of age, calves were slaughtered and body composition estimated using 9-10-11th-rib section to obtain energy deposition. Regression of BW change on daily ME intake (MEI) was used to estimate MEI at zero BW change. Increase in percentage Bos taurus had a significant effect on daily ME requirements (Mcal/d) during pregnancy (P < 0.01) and lactation (P < 0.01). Percentage Bos taurus had a positive linear effect on maintenance requirements of pregnant (P = 0.07) and lactating (P < 0.01) cows; during pregnancy, the ME requirements were 91 and 86% of those in lactation (131 +/- 3.5 vs. 145 +/- 3.4 Mcal x kg(-0.75) x d(-1)) for the 0 and 50% B. taurus groups, respectively. The 50% B. taurus cows, ANL and SNL, suckling crossbred calves had greater total MEI (4,319 +/- 61 Mcal; P < 0.01) than 0% B. taurus cows suckling NL (3,484 +/- 86 Mcal) or ANL calves (3,600 +/- 91 Mcal). The 0% B. taurus cows suckling ANL calves were more efficient (45.3 +/- 1.6 g/Mcal; P = 0.03) than straightbred NL (35.1 +/- 1.5 g/Mcal) and ANL or SNL pairs (41.0 +/- 1.0 g/Mcal). Under the conditions of this study, crossbreeding improved cow/ calf efficiency and showed an advantage for cows that have lower energy requirements. 相似文献
11.
R. Browning Jr. M.L. Leite-Browning A.W. Lewis R.D. Randel 《Domestic animal endocrinology》1996,13(6):511-517
The literature indicates that sire breed of calf influences beef calf performance. However, there is little information concerning sire breed of calf effects on reproduction in beef cows. In this experiment, Angus (A), Brahman (B), or Tuli (T) bulls were bred to 136 Brahman (B) cows to examine sire breed of calf influence on peripartum hormone profiles and the length of postpartum anestrus. Cows were bled from 7 d prepartum to 28 d postpartum to determine peripartum hormone concentrations. Cows carrying AB calves had greater (P < 0.05) prepartum estradiol-17β concentrations than did cows carrying BB and TB calves. Prepartum and postpartum progesterone concentrations did not differ between cows with AB, BB, and TB calves. Cows with TB calves had lower (P < 0.01) 13,14-dihydro-15-keto-prostaglandin F2 (PGFM) concentrations than did cows with AB and BB calves during the early postpartum period. Adjusting for birth weight removed the sire breed of calf effect on postpartum PGFM concentrations, but not prepartum estradiol-17β. Postpartum anestrus was shorter (P < 0.05) for cows nursing BB calves (84 ± 6 d) than for cows nursing AB (101 ± 6 d) or TB calves (110 ± 7 d). Adjustment for estradiol or PGFM concentrations did not reduce sire breed of calf effects on the length of postpartum anestrus. Further work is needed to determine how calf genotype may modulate the postpartum reproductive function of the dam. 相似文献
12.
From 1979 through 1987, British breed and crossbred cows were mated to Simmental, Pinzgauer or Tarentaise bulls or to Hereford-Angus crossbred bulls. Beginning in 1982, continental European crossbred females also entered the herd, to be mated for first calving to Hereford-Angus or Angus bulls and as cows to continental European or Hereford-Angus bulls. In progeny of British breed and crossbred cows, dam breed effects on birth and weaning weight were not important, but continental European crossbred calves were heavier than British crossbred contemporaries at birth and weaning. Pinzgauer- and Simmental-sired calves were heavier at birth than Tarentaise crosses, but calves sired by each of the continental breeds had similar weaning weights. Maternal heterosis was greater than direct heterosis effects on weaning weight (8% vs 5%), but only direct heterosis (13%) influenced birth weight. Within progeny of continental European crossbred cows, calves with a Tarentaise maternal grandsire were lighter at birth, with no significant difference among other maternal grandsire breeds. Maternal breed effects on weaning weight were not significant. Nevertheless, in contemporary years, continental European crossbred cows reared calves that were 10% heavier than calves reared by British crossbred cows. Pacific Northwestern cattle producers could achieve substantial increases in weaning weight from introducing inheritance from continental European dual-purpose breeds into cow herds and calf crops of British ancestry. 相似文献
13.
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) 相似文献
14.
Cows (n = 116) sired by Angus, Gray Brahman, Gir, Indu-Brazil, Nellore, and Red Brahman bulls and from Hereford dams were evaluated (when bred to the same breed of bull) for reproductive performance and cow weight and height and their calves (n = 1,161) were evaluated for birth and weaning weight in central Texas (temperate winters and subtropical summers). Cows were born from 1982 to 1985 and their calves were born from 1985 to 1999. Crossbred cows sired by Angus had a higher (P < 0.10) occurrence of calving difficulty than Gir, Indu-Brazil, Nellore, and Red Brahman crossbreds. Calves from Gir crossbreds had lighter (P < 0.10) birth weight (34.8 kg) than calves from Angus and Red Brahman crossbreds (39.4 and 37.2 kg). Calves from Angus crossbreds cows had lighter (P < 0.001) weaning weight (227.0 kg) than calves from Bos indicus crossbreds. Cows sired by Angus were lighter (P < 0.10) as mature cows (520.69 kg) than Gray Brahman, Indu-Brazil, and Red Brahman crossbreds (585.6, 571.9, and 577.6 kg, respectively). They also had smaller (P < 0.05) hip height (124.7 cm) than Bos indicus crossbreds. Mature cows sired by Indu-Brazil had greater (P < 0.05) hip height (138.3 cm) than Gir crossbreds (133.8 cm). Differences among sire breeds were noted within cow age categories (2 through 14 yr of age) for pregnancy rate, calf crop born, calf survival rate (as a trait of cow), and calf crop weaned. Angus and Indu-Brazil crossbred cows were lower (P < or = 0.10) than Gir and Nellore crossbreds for pregnancy rate, calf crop born, and(or) calf crop weaned at some, but not all, ages. Indu-Brazil crossbreds had a lower (P < or = 0.10) calf survival rate than most other breed groups at ages 11 to 14 yr. The results of this study indicate that Nellore and Gir crossbreds, but not Indu-Brazil, could perform as well or better than breeds traditionally used in cross-breeding programs of U.S. cow-calf production. 相似文献
15.
《The Professional Animal Scientist》2001,17(3):160-165
Progeny (n = 861) of tropically adapted breeds [Tuli (TU), Senepol (SE), and Brahman (BR)] and temperate breeds [Angus (AN) and Polled Hereford (HP)] were evaluated for birth and weaning traits in each of 5 yr. Multiparous crossbred cows representing three genetic types [British (Bt), ½BR½Bt, and ¾Bt¼BR] were mated to AN, HP, TU, SE, and BR sires, with the exception that BR sires were not mated to ½BR½Bt cows. Calving season was January through early March. Following calving, cows were provided bermudagrass hay and bahiagrass hay and had limited access to rye and ryegrass pastures. Cow and calf pairs grazed bermudagrass and bahiagrass pastures as available until weaning without access to creep feed. Male calves were castrated at birth and were not implanted. Data included birth weight, cannon bone length at birth, weaning weight, weaning hip height, ADG from birth to weaning (ADGBW), ADG from birth to April (ADGBA), ADG from April to weaning (ADGAW), and weight per day of age (WDA). Data were analyzed by PROC Mixed using a model that included calf genetic type, calf sex, calf birth day of year, and calf genetic type × calf sex interaction. Random effects were cow age, birth year, and sire and dam of calf. Calf genetic type and calf sex were significant sources of variation for all characteristics. Linear contrasts revealed that BR-sired calves were heavier at birth, had longer cannon bones at birth, and were taller at weaning (P<0.01). Tuli- and SE-sired calves were similar to AN- and HP-sired calves for birth weight, cannon bone length at birth, and weaning hip height. Angus-, HP-, and BR-sired calves were heavier at weaning compared with TU-sired calves, and SE-sired calves were intermediate for weaning weight (P<0.01). In conclusion, the TU-sired calves were smaller at birth and at weaning when compared with BR-sired calves. The TU- and SE-sired calves appear to offer more moderate size and growth rate through weaning than do the BR-sired calves. 相似文献
16.
Angus, Polled Hereford and Santa Gertrudis bulls from ages 1 through 5 and 7 yr were assigned to 26 two-sire breeding groups. Each year, straightbred and crossbred cows of these breeds were allotted at random within breed composition, age of dam and calving date to breeding groups on pasture. Sires within each breeding group or pair were the same age at breeding and were two of the three breeds of sires. Neither calving rate nor the proportion of calves born by one vs the other sire in the two-sire breeding groups was affected by sire age among breeding groups. For a given breed, there was no uniformity among the sires in the proportion of calves they sired in their two-sire breeding groups. The proportion of calves born for the 26 sire pairs averaged .64 vs .36 (SE = 0.4 for either high or low value) for one vs the other sire in a sire pair with no indication that calving rate was affected by unequal proportions of calves by sires within sire pairs. Cows calved significantly earlier in the calving period (b = -.775 +/- .127) as calving rate increased among sire pairs. The number of days from the start of the breeding period to calf birth was affected by differences between sires in sire pairs for 8 of the 26 pairs, but there were no significant differences due to sire pair or breed of sire because of interaction between these two variables. 相似文献
17.
The reproductive performance of Angus (A), Polled Hereford (PH) and Santa Gertrudis (SG) bulls was compared when exposed to 40 cows/bull vs 80 cows/two bulls during a 90- to 95-d breeding period on pasture. Cows were A, PH and SG straightbreds and crossbreds of these breeds. Each year, cows were allotted at random within breed composition and age of dam to breeding groups. A replicate consisted of two 40-cow single-sire units with bulls of two breeds and an 80-cow two-sire unit with two bulls of the same breeds and all four bulls of the same age. There were eight replicates of PH and SG bulls and five replicates of PH and A bulls. At breeding time, 20, 16, 12 and 4 bulls were 2-, 3-, 4- and 5-yr-olds, respectively. Reproductive performance of bulls was evaluated in terms of calving rate (CR) of cows exposed to them and number of days (NOD) from the beginning of the breeding period until calf birth. The 80-cow groups calved 3.7 d earlier (P less than .05) in the calving period and had a similar CR compared with the 40-cow groups. The PH-A replicates calved 3.5 d earlier (P less than .05) and had 7.3 percentage units higher (P less than .01) CR than PH-SG replicates. Results of this study indicated that 80-cow two-sire breeding groups had an advantage over the 40-cow single-sire groups in terms of calves born earlier in the calving period, with no reduction in CR. 相似文献
18.
A deterministic model was developed that accounted for all biological inputs and outputs for a theoretical herd of F1 females at age equilibrium mated to produce three-way terminal-cross calves and for the required proportion of straightbred cows needed to produce replacements. Two Bos indicus x Bos taurus vs two Bos taurus x Bos taurus types of crossbred cows were compared in the production environment of south-central Nebraska. The four types of F1 females were from Hereford (H) or Angus (A) dams and by H or A (HA), Pinzgauer (Pz), Brahman (Bm), or Sahiwal (Sw) sires. The crossbred females were assumed mated to Red Poll (R) sires for their first calving and to Simmental (S) sires thereafter. Two evaluations of efficiency for each of the four breeding systems were total cow and calf feed energy input 1) per unit of only weaned calf weight output (CALFEFF, Mcal/kg) and 2) per unit of weaned calf plus .55 x cull cow weight output (TVALEFF, Mcal/kg). Results for a terminal age of 7 yr in systems using HA, Pz, Bm, and Sw crossbred cows, respectively, were 64.9, 64.5, 60.9, and 59.3 Mcal/kg for CALFEFF and 45.7, 46.4, 44.1, and 43.7 Mcal/kg for TVALEFF. Changing terminal age to 11 yr reduced CALFEFF about 6% but increased TVALEFF about 7%, because total inputs increased more than output value (10 vs 3%) from 7 to 11 yr terminal ages. These results suggest differences in efficiency among these breed crosses favoring the Bos indicus crossbred cows by over 4% in this particular environment. 相似文献
19.
Milk production in Hereford cows was studied utilizing 2,487 lactation records on 926 cows. Data were collected over 17 yr (1968 to 1984) from two related herds. Estimates of daily milk yield were obtained at bimonthly intervals by the calf suckling technique. The sum of three monthly measures (TMY), a predicted sum of seven monthly observations (PMY) and 205-d weight of the calf were studied. Year, age of cow, age of dam at cow's birth and calf birth weight affected (P less than .05) all traits. Birth weight affected all measures of milk, with heavier calves obtaining more milk. Age of cow effects were significantly curvilinear, with PMY and TMY increasing for cows from 2 to 5 yr of age, but not differing for cows 6 yr and older. Age of cow effects on 205-d weight were similar to those for milk. As age of cow increased from 2 to 4 yr, 205-d calf weight increased. A leveling off in 205-d weight was observed for calves of cows 5 yr and older. Effects of age of dam of cow also were significant for all milk traits studied. As age of dam increased, PMY and TMY decreased. Highest milk yields were for cows born to and reared by 2-yr-old dams, intermediate milk yields for those by 3- and 4-yr-old dams and lowest yields by daughters of mature dams. Cows born to and reared by older dams produced less milk and weaned lighter calves. There were no interactions between age of cow and age of dam. This suggests a lasting detrimental effect of older cows on lactation yield of daughters. Thus, it appears that age of dam should be considered in evaluation of cow performance. 相似文献
20.
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