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Review: The Issue of Dystocia Expressed when Sires Varying in Percent Bos indicus Inheritance Are Mated to Bos taurus Females1
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et al. The ProfessionalThrift Animal Scientist 18:18–25
REVIEWS
: The Issue of Dystocia RExpressed when Sires Varying in EVIEW
Percent Bos indicus Inheritance Are Mated to Bos taurus Females1 F. A. THRIFT*,2, PAS, D. E. FRANKE†, PAS, and T. A. THRIFT‡ of Animal Sciences, University of Kentucky, Lexington, KY 40546-0215; †Louisiana State University Agricultural Center, Baton Rouge, LA 70803-4210; and ‡Department of Animal Sciences, University of Florida, Gainesville, FL 32611-0910
*Department
Abstract
contributors to the increased dystocia observed when Brahman bulls are mated This review reveals that dystocia, with to Bos taurus females, especially in associated increased mortality and(or) situations involving late-born, male reduced survival rate, can be a problem calves. when sires varying in percent Bos indicus inheritance are mated to Bos taurus (Key Words: Bos indicus, Dystocia, females. The fact that male calves Cattle.) resulting from these matings are gestated longer and have considerably heavier birth BW than heifer calves is a major Although sires varying in percent contributor to this increased dystocia. A Bos indicus inheritance are utilized small number of studies involving Brahman sires have indicated larger birth widely in crossbreeding programs BW for late-born calves in spring calving throughout the Southeast and Gulf Coast areas (21, 36, 37, 53, 89, 93) programs. Furthermore, several studies and to a lesser extent in temperate have documented poor reproductive areas (32, 75, 76), dystocia, especially performance of Brahman bulls, which contributes to subsequent delayed birth of when Bos indicus bulls are mated to Bos taurus females, can be a serious their calves. When combined with the problem. The purpose of this review longer gestation length as well as the is to summarize studies that have positive direct additive and heterotic reported incidence of dystocia effects of the Brahman breed for birth and(or) mortality(survival) rate when BW, these factors appear to be major sires varying in percent Bos indicus inheritance were mated to Bos taurus females and to relate this dystocia to birth BW and gestation length 1Published with approval of the director of differences. The interaction between the Kentucky Agricultural Experiment Station sire breed and sex of calf, as a conas Journal Article 01-07-93. tributing factor to the increased 2To whom correspondence should be addystocia, is also examined.
Introduction
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Materials and Methods Previous reviews have dealt directly (60, 78) or indirectly (48) with the general issue of dystocia in cattle. The present review deals specifically with the problem of dystocia (cows requiring some degree of assistance during calving) expressed when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. Increased gestation length and birth BW and the interaction between sire breed and sex of calf for each of these traits are also examined as contributing factors to this increased dystocia. Lastly, the possible relationships among reproductive performance of Brahman bulls, subsequent birth date of their calves, and heavier birth BW of late-born calves are examined as a contributing factor to the increased dystocia observed when Brahman bulls are mated to Bos taurus females. In some of the studies reviewed, it was not possible to ascertain statistical significance of specific differences. Thus, in situations in which differences are presented with no indication of statistical significance, the differences are 1) either nonsignificant or 2) impossible to determine
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
significantly based on information presented in the original manuscripts.
Results and Discussion Dystocia (Increased Mortality/ Reduced Survival Rate). Dystocia has been demonstrated to have a negative impact on calf survival (1, 3, 43, 48, 55, 56, 60, 72, 87, 99) and subsequent rebreeding performance of the cow herd (5, 9, 15, 18, 26, 56, 72). Additional studies have addressed other aspects of dystocia in cattle (6, 8, 11, 20, 26, 27, 33, 54, 61– 64, 83, 86, 87). Brahman vs Bos taurus sire breeds. In a Nebraska study, Laster (54) reported dystocia values (P<0.01) of 22, 39, 37, 65, and 70%, respectively, for 2-yr-old cows that were mated as yearlings to Angus, Hereford, Devon, Holstein, and Brahman sires. Notter et al. (68), in a later study involving these same sire breeds, reported dystocia values (P<0.01) of 27, 67, 47, and 34%, respectively, for 2-yr-old cows that were mated as yearlings to Hereford/ Angus, Brahman, Holstein, and Devon sires. Although not significant, the sire breed × sex of calf interaction revealed that dystocia for male and female calves differed by sire breed with results that were 18, 40, 30, and 31% greater in male calves sired, respectively, by Hereford/Angus, Brahman, Holstein, and Devon sires. Total calf mortality during the preweaning period (P<0.01) was 10, 21, 15, and 7%, respectively, for the Hereford/Angus-, Brahman-, Holstein-, and Devon-sired calves. Compared with 26, 27, and 0%, respectively, for Hereford/Angus- Holstein-, and Devon-sired calves, 52% of deaths (P<0.01) of Brahman-sired calves occurred shortly after parturition. In a Florida study (24), the percentages (P<0.01) of unassisted calvings were 86.8, 97.6, and 100%, respectively, for Angus dams mated to Brahman, Senepol, and Tuli sires. Corresponding values for the percentages (P<0.10) of calves that survived
to weaning were 90.4, 94.1, and 97.8%, respectively. The greater dystocia expressed by Brahman-sired calves tended to be reflected in poorer calf survivability to weaning, with most losses (7.2%) within 3 d of birth. In a Louisiana study involving the mating of Brahman and Continental sires (Chianina, Maine Anjou, Simmental) to Angus and Hereford cows, Williamson and Humes (98) detected no difference among the sire breeds for percentage of assisted births or survival rate; however, survival rate tended to be least for Brahman-sired (90.7%) compared with Chianina- (92.1%), Maine Anjou- (93.4%), and Simmental-sired (96.6%) calves. Incidence of dystocia was similar for Hereford, Red Poll, Red Poll × Hereford, Hereford × Red Poll, Angus × Hereford, Brahman × Hereford, Brahman × Angus, and Angus × Charolais calves at a Nevada location (5). In a later study at the same location involving the same genetic types, Bailey (4) did not report dystocia values but did conclude that survival of Brahman × Hereford calves, which averaged 94%, was less (P<0.05) than for Angus × Hereford calves (100%). Weaning rates for Hereford cows bred to Hereford, Red Poll, and Angus sires were approximately 11% greater (P<0.10) than for Hereford cows bred to Brahman bulls. In a Georgia study (27) involving diallel mating of Brahman, Hereford, Limousin, and Simmental breeds, Brahman-sired calves required more (P<0.05) assistance at birth and had a lesser (P<0.05) 24-h survival rate. Noteworthy were calving ease scores of 1.02 (essentially no difficulty) and 1.57, respectively, for Hereford 么 × Brahman 乆 and Brahman 么 × Hereford 乆 crosses. Corresponding 24-h survival rates for these two crosses were 94.7 and 88.2%, respectively. The sire breed × sex of calf interaction was not significant for calving ease score or 24-h survival rate. In another diallel study involving the Angus, Brahman, Hereford, Holstein, and Jersey breeds, Texas workers (59) reported that straight-
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bred Brahman matings resulted in 0.0% dystocia; however, dystocia values were 5.0 (P<0.05), 4.0, 0.3, and 1.9%, respectively, for BrahmanAngus, Brahman-Hereford, BrahmanHolstein and Brahman-Jersey inter se matings. In an Arkansas study (18) in which Angus and Brahman females were mated to Angus and Brahman sires, dystocia was 12.6, 12.9, and 40.0% (P<0.01), respectively, for Angus cows mated to Angus sires, Angus cows producing Brahman-sired heifer calves, and Angus cows producing Brahman-sired bull calves. Peacock et al. (74), in a Florida study involving the mating of Angus, Brahman, and Charolais sires to Angus, Brahman, and Charolais dams, reported that calf survival was not significantly affected by sire breed (95.5, 93.3, and 94.1%, respectively, for Angus, Brahman, and Charolais sires); however, breed of dam had an influence (P<0.01) with Angus, Brahman, and Charolais dams having calf survival rates of 88.7, 97.2, and 96.9%, respectively. Low calf survival for Angus dams was the result of a high death loss of F1 progeny sired by Brahman (13.0%) and Charolais (13.5%) sires. A second phase of this study (73) also revealed that sire breed did significantly impact calf survival rates, which were 94, 93, and 91%, respectively, for Angus, Brahman, and Charolais sires. A Louisiana study (97) involving rotational crossing of Angus, Hereford, Charolais, and Brahman breeds revealed that Brahman-sired rotational calves required more assistance at birth in some generations. A Florida rotational crossbreeding study (31) involving the Angus, Brahman, and Hereford breeds revealed that calf survival rates were similar for the three sire breeds. A Georgia study (66) indicated that dystocia score was essentially the same for Angus- and Polled Hereford-sired crossbred heifers mated to Angus and medium-frame Brahman sires. In general, results of these studies indicate that relative to Bos taurus sires, dystocia is increased when Bos
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indicus sires (most notably Brahman) are mated to Bos taurus females. Brahman vs Other Bos indicus vs Bos taurus Sire Breeds. A Texas study (71), involving one Bos taurus and five Bos indicus sire breeds, revealed calving ease scores (0 = no assistance; 1 = assisted birth) of 0.05, 0.11, 0.06, 0.22, and 0.14, respectively, for multiparous Hereford cows mated to Angus, Brahman (Gray/Red Brahman combined), Gir, Indu-Brazil, and Nellore bulls; these differences were nonsignificant. Dystocia was 5.9, 13.0 (P<0.05), 9.2, 9.3, and 9.0% for Hereford and Angus dams mated, respectively, to Angus/Hereford, Brahman, Sahiwal, Pinzgauer, and Tarentaise sires at a Nebraska location (44). A significant breeding group × sex of calf interaction indicated that the greater the average level of dystocia for a breeding group, the greater the observed difference in dystocia between male and female progeny. For example, in the Brahman × Angus breeding group, dystocia was 19.0 and 5.7%, respectively, for male and female calves. Although Brahman-sired calves expressed the greatest level of perinatal mortality (5.6%), differences among the sire breeds were not significant for this trait. In a Kenya study (91) involving two Bos indicus breeds, calf survival rate was similar for the Boran (94%) and Sahiwal (96%). In a study (92) conducted at the same location involving diallel mating of the Boran and Red Poll breeds, calf survival rate was similar for the Boran (92.3%) and Red Poll (93.0%) breeds. In a later study (45) at this location, which involved cows resulting from mating of Angus, Red Poll, and Boran bulls to Ankole, Boran, and Zebu cows, percentage of preweaning viability was 94.0, 85.4, 99.2, 93.1, and 94.9%, respectively, for Boran-, Red Poll-, Friesian-, Brown Swiss-, and Simmental-sired calves; these differences were not significant. In a related study, Gregory et al. (46) reported percentage of preweaning viability values of 80.4, 91.7, 83.9, 90.4, and 95.9%, respectively, for
Thrift et al.
calves from Ankole, Boran, Zebu, Boran × Ankole, and Boran × Zebu cows when mated to Friesian, Brown Swiss, and Simmental sires; these differences were also not significant. These studies also indicate that, relative to Bos taurus sires, Brahman sires increase the incidence of dystocia, but the level of dystocia expressed by Brahman-sired calves is not expected to be greater than that expressed by calves sired by other Bos indicus sire breeds, such as Indu-Brazil and Nellore. Brahman vs Bos indicus-Derivative vs Bos taurus Sire Breeds. In a study involving the mating of Angus, Brahman, Brangus, and AfricanderAngus sires in various combinations with Angus, Brahman, Brangus, and Africander-Angus dams, Louisiana workers (82) reported that dystocia was not a problem for any of the sire × dam mating groups. In a Georgia study (42) involving mating of Angus, Santa Gertrudis, and Gelbvieh sires to Angus and Santa Gertrudis females, calving ease values were 95.1, 98.1, and 98.3%, respectively, for females bred to Angus, Santa Gertrudis, and Gelbvieh sires; these differences were nonsignificant. Corresponding values by sire breed for percentage of calves alive at 24-h after birth were 98.6, 94.9, and 98.3%, respectively; these differences were also nonsignificant. Percentage of live calves at 24 h indicated that straightbred Santa Gertrudis calves (90.9%) were less (P<0.05) viable at birth than the other four mating types (98.6%). At another Georgia location, a grading-up and rotational crossing study (65) involving the Angus, Polled Hereford, and Santa Gertrudis breeds revealed that Santa Gertrudis sires were associated with a lesser (P<0.05) proportion of cows that had a live calf and that weaned a calf. A later study (67) at the same location revealed that the proportion of Polled Hereford females that weaned a calf was 0.82, 0.74, 0.81, and 0.78, respectively, when mated to Angus, Santa Gertrudis, Angus × Santa Gertrudis, and Santa Gertrudis ×
Angus bulls; these differences were nonsignificant. For both of these studies, the authors did not indicate how much of the observed differences between the Santa Gertrudis and the other genetic types were attributed to differences in dystocia. In a Florida study (6) involving the mating of Brangus, Simbrah, and Braford primiparous heifers to Angus bulls selected for light birth BW and calving ease during a 2-yr period, dystocia score and dystocia incidence were similar for the three dam genetic types. The dam breed × sex of calf interaction was not significant for dystocia incidence during either year or for dystocia score during yr 1, but the interaction approached significance for the latter trait during yr 2 of the study. This interaction for dystocia score seemed to be caused by the magnitude of the difference between sexes within the dam breeds (Brangus, 1.33 vs 1.00; Simbrah, 1.17 vs 1.12; Braford, 1.08 vs 1.09; male vs female, respectively). Some of these studies reveal that dystocia levels were similar for calves sired by Brahman, Santa Gertrudis, and Bos taurus bulls; other studies revealed similar dystocia levels for calves sired by Santa Gertrudis and Bos taurus bulls, but weaning rate tended to be less for females exposed to Santa Gertrudis bulls. Increased Birth BW and Gestation Length as Contributors to Increased Dystocia (Increased Mortality/Reduced Survival Rate). Birth BW. Bellows et al. (10) indicated that birth BW is a major contributor to dystocia in cattle (relative numerical ranking of four major factors affecting dystocia: calf sex = 1.00, dam precalving BW = 1.10, dam precalving pelvic area = 1.16, and calf birth BW = 3.05). Because the direct additive (17, 35, 38, 70, 84, 100) and heterotic (17, 27, 34, 36, 38, 84) effects for the Brahman breed are positive for birth BW, increased birth BW is expected to be a major contributor to increased dystocia observed when Brahman sires are mated to Bos taurus females.
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
In a study based on data collected at several locations in the Southern Region, Kincaid (51) reported that Brahman-sired calves were 1.9 kg heavier (P<0.05) than British-sired calves. Similarly, McCormick and Southwell (58) reported that Brahman-sired calves were 3.8 kg heavier (P<0.01) than Angus-sired calves, and Ellis et al. (34) reported that Brahman-sired calves were 2.2 kg heavier (P<0.01) than Hereford-sired calves. Similarly, Roberson et al. (84) reported that Brahman-sired calves were 2.3 kg heavier (P<0.01) than Hereford-sired calves. Bolton et al. (12) reported that ¼ and ½ Brahman calves were 1.4 and 3.8 kg heavier (P<0.05), respectively, than 0 Brahman calves. The results of Comerford et al. (27) indicated that Brahman-sired crossbred calves were 4.3, 5.6, and 5.9 kg heavier (P<0.05), respectively, than Simmental-, Limousin-, and Polled Hereford-sired crossbred calves. Gregory et al. (44) reported that Brahman-sired calves were 5.2, 2.9, 1.7, and 3.4 kg heavier (P<0.05), respectively, than Hereford/ Angus-, Sahiwal-, Pinzgauer-, and Tarentaise-sired calves. A Texas study (47) revealed that Brahman-sired calves were 3.7 and 7.6 kg heavier (P<0.05), respectively, than Boranand Tuli-sired calves. Another Texas study (71) indicated that Brahmansired (Gray/Red Brahman combined) calves were 5.5 (P<0.05), 4.3 (P<0.05), and 0.6 kg heavier, respectively, than Angus-, Gir-, and Nellore-sired calves, but were 1.8 kg lighter than Indu Brazil-sired calves. Crockett et al. (29) reported that Brahman-sired calves were 5.0 (P<0.01), 2.9 (P<0.01), 1.3, 0.3, and 1.5 (P<0.01) kg heavier, respectively, than Brangus-, Beefmaster-, Limousin-, Maine-Anjou, and Simmental-sired calves. Gotti et al. (42) reported that Santa Gertrudissired calves were 3.0 kg heavier (P<0.05) than Angus-sired calves, but similar to Gelbvieh-sired calves. The results of Chapman et al. (22) revealed that Santa Gertrudis-sired calves were 3.8 and 2.7 kg heavier (P<0.01), respectively, than Angusand Polled Hereford-sired calves;
however, Neville et al. (67) reported that Santa Gertrudis-sired calves were 2.8 kg lighter (P<0.05) than Angussired calves. Brown et al. (16) reported that birth BW of Brahman- and Beefmaster-sired calves were similar: 37 and 39 kg, respectively. To examine further the dystocia problem observed when sires varying in percent Bos indicus inheritance are mated to Bos taurus females, some studies have examined the interaction between sire breed and sex of calf for birth BW. A previous review (48) of factors affecting calf birth BW suggested that differences between sexes for birth BW were relatively constant across breeds. Several studies indicate that this is not the case when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. One study indicated that the sire breed × sex of calf interaction was nonsignificant for birth BW (82); however, most studies have indicated the interaction was important (19, 24, 68, 71, 90, 94, 101). Two studies indicated that the interaction was significant but did not elaborate on the nature of the interaction (27, 44). In the study of Browning et al. (19), which involved Brahman, Tuli, and Angus sires, a sex difference was detected only in Brahman-sired calves; Brahman-, Angus-, and Tulisired male calves were 4.5 (P<0.01), 1.0, and -1.0 kg heavier, respectively, than female calves. In a similar study, Chase et al. (24) revealed that Brahman-, Tuli-, and Senepol-sired male calves were 5.1 (P<0.05), 2.8, and 1.7 kg heavier, respectively, than female calves. In the study of Notter et al. (68), the interaction was important in 2-yr-old cows because of greater sexual dimorphism for birth BW in Brahman-sired calves. The mean sex difference for all crosses was 2.1 kg, but the sex difference was 4.4 kg (P<0.01) in Brahman-sired calves. A Texas study (71) involving one Bos taurus and five Bos indicus sire breeds revealed that Angus-, Brahman(Gray/Red Brahman combined), Gir-, Indu Brazil-, and Nellore-sired male calves were 2.6, 4.9 (P<0.05), 4.9
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(P<0.05), 6.8 (P<0.05), and 7.0 (P<0.05) kg heavier, respectively, than heifer calves. In the study by Gregory et al. (44), as quoted by Paschal et al. (71), Brahman-sired male calves of Hereford and Angus dams were 4.5 and 5.7 kg heavier, respectively, than heifer calves; corresponding differences in Sahiwal-sired calves were 6.2 and 5.5 kg, respectively. For the Bos taurus-sired calves, the corresponding sex differences were 2.9 and 2.0 kg in Pinzgauer crosses and 3.7 and 4.4 kg in Tarentaise crosses, respectively; in the Hereford-Angus crosses, the sex difference was 2.5 kg in Angus-sired calves and 2.0 kg in Hereford-sired calves. A Louisiana study (94) revealed that Angus-, Brahman-, Brangus-, and Hereford-sired male calves were 1.2, 4.1, 3.0, and 1.0 kg heavier, respectively, than heifer calves. A more recent Louisiana study (101) revealed that Angus-, Brahman-, Charolais-, and Hereford-sired male calves were 0.9 (P<0.05), 5.0 (P<0.01), 1.4 (P<0.01), and 1.4 (P<0.01) kg heavier, respectively, than heifer calves. Expressing results as a deviation from Angus-sired calves, Nebraska workers (95) reported that Brahman-sired male calves were 3.8 kg heavier (P<0.05) than heifer calves; however, for 10 other Bos taurus sire breeds, male calves exceeded heifer calves by an average of only 0.6 kg. A Kentucky study (90), which involved two data sets, indicated that Angus and Brahman male calves exceeded (P<0.05) Angus and Brahman heifer calves by 1.9 and 2.2 kg, respectively. In contrast, Brahman 么 × Angus 乆 male calves exceeded (P<0.05) Brahman 么 × Angus 乆 heifer calves by 4.5 kg. A similar pattern was observed in the second data set. Hereford and Brahman male calves exceeded (P<0.05) Hereford and Brahman female calves by 1.7 and 2.2 kg, respectively; Brahman 么 × Hereford 乆 male calves exceeded (P<0.05) Brahman 么 × Hereford 乆 heifer calves by 5.5 kg. Similar results were observed in a Georgia study (58); Angus 么 × Hereford 乆 male calves were 0.2 kg heavier than heifer calves; however,
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Brahman 么 × Hereford 乆 calves male calves were 2.8 kg heavier than heifer calves. Most studies reveal that Bos indicus-sired calves are heavier at birth than Bos taurus-sired calves. Also, most studies that have examined the interaction between sire breed and sex of calf reveal a larger birth BW difference between male and female Bos indicus-sired crossbred calves than for Bos taurus-sired crossbred calves. Gestation Length. A positive relationship exists between gestation length and birth BW in cattle (2, 13). Reynolds et al. (82) reported that for each 1-d increase in gestation length, calf birth BW increased by an average of 0.25 to 0.30 kg (P<0.01). Several studies have reported longer gestation length for Bos indicus cows (59, 77, 80, 82, 85). Thus, because Bos indicus cattle express a longer gestation length, it is logical to assume that the increased birth BW resulting from mating of sires varying in percent Bos indicus inheritance with Bos taurus females are due in part to calves being gestated longer. Paschal et al. (71) reported that Bos indicus-sired calves were gestated 7 to 12 d longer (P<0.05) than Angus-sired calves. The sire breed × sex of calf interaction was significant; however, the authors concluded that the interaction was probably caused by sampling error associated with the Angus sires, because Angus-sired heifer calves were gestated 2.4 d longer than Angussired bull calves. For the Bos indicussired calves, Brahman- (Gray/Red Brahman combined), Gir-, Indu Brazil-, and Nellore-sired male calves were gestated 6.0 (P<0.05), 3.4, 2.2, and 6.8 (P<0.05) d longer, respectively, than heifer calves. In the study by Gregory et al. (44), Hereford-Angus-, Brahman-, Sahiwal-, Pinzgauer-, and Tarentaisesired calves were gestated 284, 291, 294, 286, and 287 d, respectively; all sire breed groups except Pinzgauer and Tarentaise were different (P<0.01) from each other; male calves were gestated 2 d longer (P<0.01) than
Thrift et al.
heifer calves. In a Louisiana study (98), Brahman-sired calves were gestated the longest (291 d; P<0.01) followed by Chianina- (289 d), Maine-Anjou- (286 d), and Simmental-sired (286 d) calves; male calves were gestated 2.1 d longer (P<0.01) than heifer calves. A Georgia study (42) indicated that Angus-sired calves were gestated shorter (284 d; P<0.05) than Santa Gertrudis- (286 d) or Gelbvieh-sired (287 d) calves; male calves were gestated only slightly longer (0.7 d) than heifer calves. A Texas study (47), which involved Brahman, Boran, and Tuli sires, indicated that sire breed was not significant for gestation length even though Boran- and Brahman-sired calves were gestated 3 and 2 d longer, respectively, than Tuli-sired calves; male calves were gestated 1.9 d longer (P<0.05) than heifer calves. Similarly, a Louisiana study (98) revealed that male calves were gestated 2.1 d longer (P<0.01) than heifer calves. In another Texas study (19), Brahman-, Angus-, and Tuli-sired calves were gestated 293.7, 284.0, and 288.4 d, respectively; all sire differences were significant (P<0.01). The sire breed × sex of calf interaction was significant. Within sire breeds, only the Brahman group exhibited a sex difference in gestation length, as male calves were gestated 5 d longer (P<0.01) than heifer calves. In contrast, Tuli- and Angus-sired male calves were gestated 0.2 and 2.6 d longer, respectively, than heifer calves. In a Florida study (24), Brahman-, Tuli-, and Senepolsired calves were gestated 283.6, 282.0, and 281.8 d, respectively; however, these differences were not significant. Male calves tended to be gestated slightly longer (1 d) than heifer calves; the sire breed × sex of calf interaction was not significant. Reynolds et al. (82) also reported that male calves were gestated 0.6 d longer (P<0.01) than heifer calves and that the sire breed × sex of calf interaction was not significant. These studies reveal that Bos indicus-sired calves are gestated longer than Bos taurus-sired calves. Also,
relative to Bos taurus-sired calves, Bos indicus-sired male calves are gestated longer than female calves. Reproductive Performance of Brahman Bulls and Subsequent Calf Birth Date as Contributing Factors to Increased Birth BW and Dystocia. Neville et al. (66) reported that the number of days from start of the breeding period to birth of calf was similar for Angus (308 d) and Brahman (306 d) sires; however, most studies (4, 30, 38, 42, 58, 67, 69, 80– 82, 96, 97, 101) have indicated that, relative to Bos taurus-sired calves, Brahman- or Brahman-derivativesired calves are born later in the calving season. Increased gestation length attributed to the Brahman breed and the fact that some Brahman sires express poor reproductive performance (5, 25, 40, 79), some tend to clump together in multi-sire breeding units (21), and some show preferential mating habits (23, 52, 81) all contributed to the later birth date of the Brahman-sired calves. In two studies (47, 66) involving Brahman sires, calves born late in spring calving programs had larger birth weights. Thus, based on these results, increased dystocia would be expected, especially in situations involving Brahman-sired male calves that are late-born. Also, because it has been demonstrated that birth weights are increased 2 to 4 kg with increased nutrition of the cow herd during late gestation (7, 14, 28, 39, 49, 54), latecalving cows involved in a spring calving program would be expected to contribute to the slightly heavier birth BW because of their improved nutritional state relative to earlycalving cows.
Implications Dystocia is increased when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. Male calves resulting from these matings express a higher incidence of dystocia than heifer calves because male calves are gestated longer and have considerably larger birth BW.
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
The increased incidence of dystocia expressed by calves resulting from mating of sires varying in percent Bos indicus inheritance with Bos taurus females and the fact that Bos indicussired calves are more susceptible to cold, moist conditions within 24 h after birth (41, 50, 52, 57, 68, 82, 88, 93, 98), contributes greatly to increased calf mortality and constitutes a serious problem for producers utilizing sire breeds varying in percent Bos indicus inheritance.
Livest. Range Res. Lab., Miles City, MT. 11. Berger, P. J., A. C. Cubas, K. J. Koehler, and M. H. Healey. 1992. Factors affecting dystocia and early calf mortality in Angus cows and heifers. J. Anim. Sci. 70:1775. 12. Bolton, R. C., R. R. Frahm, J. W. Castree, and S. W. Coleman. 1987. Genotype × environment interactions involving proportion of Brahman breeding and season of birth. I. Calf growth to weaning. J. Anim. Sci. 65:42. 13. Bourdon, R. M., and J. S. Brinks. 1982. Genetic, environmental and phenotypic relationships among gestation length, birth weight, growth traits and age at first calving in beef cattle. J. Anim. Sci. 55:543. 14. Boyd, G. W., T. E. Kiser, and R. S. Lowery. 1987. Effects of prepartum energy intake on steroids during late gestation and on cow and calf performance. J. Anim. Sci. 64:1703.
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REVIEW: Dystocia in Bos indicus × Bos taurus Matings
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et al. The ProfessionalThrift Animal Scientist 18:18–25
REVIEWS
: The Issue of Dystocia RExpressed when Sires Varying in EVIEW
Percent Bos indicus Inheritance Are Mated to Bos taurus Females1 F. A. THRIFT*,2, PAS, D. E. FRANKE†, PAS, and T. A. THRIFT‡ of Animal Sciences, University of Kentucky, Lexington, KY 40546-0215; †Louisiana State University Agricultural Center, Baton Rouge, LA 70803-4210; and ‡Department of Animal Sciences, University of Florida, Gainesville, FL 32611-0910
*Department
Abstract
contributors to the increased dystocia observed when Brahman bulls are mated This review reveals that dystocia, with to Bos taurus females, especially in associated increased mortality and(or) situations involving late-born, male reduced survival rate, can be a problem calves. when sires varying in percent Bos indicus inheritance are mated to Bos taurus (Key Words: Bos indicus, Dystocia, females. The fact that male calves Cattle.) resulting from these matings are gestated longer and have considerably heavier birth BW than heifer calves is a major Although sires varying in percent contributor to this increased dystocia. A Bos indicus inheritance are utilized small number of studies involving Brahman sires have indicated larger birth widely in crossbreeding programs BW for late-born calves in spring calving throughout the Southeast and Gulf Coast areas (21, 36, 37, 53, 89, 93) programs. Furthermore, several studies and to a lesser extent in temperate have documented poor reproductive areas (32, 75, 76), dystocia, especially performance of Brahman bulls, which contributes to subsequent delayed birth of when Bos indicus bulls are mated to Bos taurus females, can be a serious their calves. When combined with the problem. The purpose of this review longer gestation length as well as the is to summarize studies that have positive direct additive and heterotic reported incidence of dystocia effects of the Brahman breed for birth and(or) mortality(survival) rate when BW, these factors appear to be major sires varying in percent Bos indicus inheritance were mated to Bos taurus females and to relate this dystocia to birth BW and gestation length 1Published with approval of the director of differences. The interaction between the Kentucky Agricultural Experiment Station sire breed and sex of calf, as a conas Journal Article 01-07-93. tributing factor to the increased 2To whom correspondence should be addystocia, is also examined.
Introduction
dressed: [email protected]
Materials and Methods Previous reviews have dealt directly (60, 78) or indirectly (48) with the general issue of dystocia in cattle. The present review deals specifically with the problem of dystocia (cows requiring some degree of assistance during calving) expressed when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. Increased gestation length and birth BW and the interaction between sire breed and sex of calf for each of these traits are also examined as contributing factors to this increased dystocia. Lastly, the possible relationships among reproductive performance of Brahman bulls, subsequent birth date of their calves, and heavier birth BW of late-born calves are examined as a contributing factor to the increased dystocia observed when Brahman bulls are mated to Bos taurus females. In some of the studies reviewed, it was not possible to ascertain statistical significance of specific differences. Thus, in situations in which differences are presented with no indication of statistical significance, the differences are 1) either nonsignificant or 2) impossible to determine
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
significantly based on information presented in the original manuscripts.
Results and Discussion Dystocia (Increased Mortality/ Reduced Survival Rate). Dystocia has been demonstrated to have a negative impact on calf survival (1, 3, 43, 48, 55, 56, 60, 72, 87, 99) and subsequent rebreeding performance of the cow herd (5, 9, 15, 18, 26, 56, 72). Additional studies have addressed other aspects of dystocia in cattle (6, 8, 11, 20, 26, 27, 33, 54, 61– 64, 83, 86, 87). Brahman vs Bos taurus sire breeds. In a Nebraska study, Laster (54) reported dystocia values (P<0.01) of 22, 39, 37, 65, and 70%, respectively, for 2-yr-old cows that were mated as yearlings to Angus, Hereford, Devon, Holstein, and Brahman sires. Notter et al. (68), in a later study involving these same sire breeds, reported dystocia values (P<0.01) of 27, 67, 47, and 34%, respectively, for 2-yr-old cows that were mated as yearlings to Hereford/ Angus, Brahman, Holstein, and Devon sires. Although not significant, the sire breed × sex of calf interaction revealed that dystocia for male and female calves differed by sire breed with results that were 18, 40, 30, and 31% greater in male calves sired, respectively, by Hereford/Angus, Brahman, Holstein, and Devon sires. Total calf mortality during the preweaning period (P<0.01) was 10, 21, 15, and 7%, respectively, for the Hereford/Angus-, Brahman-, Holstein-, and Devon-sired calves. Compared with 26, 27, and 0%, respectively, for Hereford/Angus- Holstein-, and Devon-sired calves, 52% of deaths (P<0.01) of Brahman-sired calves occurred shortly after parturition. In a Florida study (24), the percentages (P<0.01) of unassisted calvings were 86.8, 97.6, and 100%, respectively, for Angus dams mated to Brahman, Senepol, and Tuli sires. Corresponding values for the percentages (P<0.10) of calves that survived
to weaning were 90.4, 94.1, and 97.8%, respectively. The greater dystocia expressed by Brahman-sired calves tended to be reflected in poorer calf survivability to weaning, with most losses (7.2%) within 3 d of birth. In a Louisiana study involving the mating of Brahman and Continental sires (Chianina, Maine Anjou, Simmental) to Angus and Hereford cows, Williamson and Humes (98) detected no difference among the sire breeds for percentage of assisted births or survival rate; however, survival rate tended to be least for Brahman-sired (90.7%) compared with Chianina- (92.1%), Maine Anjou- (93.4%), and Simmental-sired (96.6%) calves. Incidence of dystocia was similar for Hereford, Red Poll, Red Poll × Hereford, Hereford × Red Poll, Angus × Hereford, Brahman × Hereford, Brahman × Angus, and Angus × Charolais calves at a Nevada location (5). In a later study at the same location involving the same genetic types, Bailey (4) did not report dystocia values but did conclude that survival of Brahman × Hereford calves, which averaged 94%, was less (P<0.05) than for Angus × Hereford calves (100%). Weaning rates for Hereford cows bred to Hereford, Red Poll, and Angus sires were approximately 11% greater (P<0.10) than for Hereford cows bred to Brahman bulls. In a Georgia study (27) involving diallel mating of Brahman, Hereford, Limousin, and Simmental breeds, Brahman-sired calves required more (P<0.05) assistance at birth and had a lesser (P<0.05) 24-h survival rate. Noteworthy were calving ease scores of 1.02 (essentially no difficulty) and 1.57, respectively, for Hereford 么 × Brahman 乆 and Brahman 么 × Hereford 乆 crosses. Corresponding 24-h survival rates for these two crosses were 94.7 and 88.2%, respectively. The sire breed × sex of calf interaction was not significant for calving ease score or 24-h survival rate. In another diallel study involving the Angus, Brahman, Hereford, Holstein, and Jersey breeds, Texas workers (59) reported that straight-
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bred Brahman matings resulted in 0.0% dystocia; however, dystocia values were 5.0 (P<0.05), 4.0, 0.3, and 1.9%, respectively, for BrahmanAngus, Brahman-Hereford, BrahmanHolstein and Brahman-Jersey inter se matings. In an Arkansas study (18) in which Angus and Brahman females were mated to Angus and Brahman sires, dystocia was 12.6, 12.9, and 40.0% (P<0.01), respectively, for Angus cows mated to Angus sires, Angus cows producing Brahman-sired heifer calves, and Angus cows producing Brahman-sired bull calves. Peacock et al. (74), in a Florida study involving the mating of Angus, Brahman, and Charolais sires to Angus, Brahman, and Charolais dams, reported that calf survival was not significantly affected by sire breed (95.5, 93.3, and 94.1%, respectively, for Angus, Brahman, and Charolais sires); however, breed of dam had an influence (P<0.01) with Angus, Brahman, and Charolais dams having calf survival rates of 88.7, 97.2, and 96.9%, respectively. Low calf survival for Angus dams was the result of a high death loss of F1 progeny sired by Brahman (13.0%) and Charolais (13.5%) sires. A second phase of this study (73) also revealed that sire breed did significantly impact calf survival rates, which were 94, 93, and 91%, respectively, for Angus, Brahman, and Charolais sires. A Louisiana study (97) involving rotational crossing of Angus, Hereford, Charolais, and Brahman breeds revealed that Brahman-sired rotational calves required more assistance at birth in some generations. A Florida rotational crossbreeding study (31) involving the Angus, Brahman, and Hereford breeds revealed that calf survival rates were similar for the three sire breeds. A Georgia study (66) indicated that dystocia score was essentially the same for Angus- and Polled Hereford-sired crossbred heifers mated to Angus and medium-frame Brahman sires. In general, results of these studies indicate that relative to Bos taurus sires, dystocia is increased when Bos
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indicus sires (most notably Brahman) are mated to Bos taurus females. Brahman vs Other Bos indicus vs Bos taurus Sire Breeds. A Texas study (71), involving one Bos taurus and five Bos indicus sire breeds, revealed calving ease scores (0 = no assistance; 1 = assisted birth) of 0.05, 0.11, 0.06, 0.22, and 0.14, respectively, for multiparous Hereford cows mated to Angus, Brahman (Gray/Red Brahman combined), Gir, Indu-Brazil, and Nellore bulls; these differences were nonsignificant. Dystocia was 5.9, 13.0 (P<0.05), 9.2, 9.3, and 9.0% for Hereford and Angus dams mated, respectively, to Angus/Hereford, Brahman, Sahiwal, Pinzgauer, and Tarentaise sires at a Nebraska location (44). A significant breeding group × sex of calf interaction indicated that the greater the average level of dystocia for a breeding group, the greater the observed difference in dystocia between male and female progeny. For example, in the Brahman × Angus breeding group, dystocia was 19.0 and 5.7%, respectively, for male and female calves. Although Brahman-sired calves expressed the greatest level of perinatal mortality (5.6%), differences among the sire breeds were not significant for this trait. In a Kenya study (91) involving two Bos indicus breeds, calf survival rate was similar for the Boran (94%) and Sahiwal (96%). In a study (92) conducted at the same location involving diallel mating of the Boran and Red Poll breeds, calf survival rate was similar for the Boran (92.3%) and Red Poll (93.0%) breeds. In a later study (45) at this location, which involved cows resulting from mating of Angus, Red Poll, and Boran bulls to Ankole, Boran, and Zebu cows, percentage of preweaning viability was 94.0, 85.4, 99.2, 93.1, and 94.9%, respectively, for Boran-, Red Poll-, Friesian-, Brown Swiss-, and Simmental-sired calves; these differences were not significant. In a related study, Gregory et al. (46) reported percentage of preweaning viability values of 80.4, 91.7, 83.9, 90.4, and 95.9%, respectively, for
Thrift et al.
calves from Ankole, Boran, Zebu, Boran × Ankole, and Boran × Zebu cows when mated to Friesian, Brown Swiss, and Simmental sires; these differences were also not significant. These studies also indicate that, relative to Bos taurus sires, Brahman sires increase the incidence of dystocia, but the level of dystocia expressed by Brahman-sired calves is not expected to be greater than that expressed by calves sired by other Bos indicus sire breeds, such as Indu-Brazil and Nellore. Brahman vs Bos indicus-Derivative vs Bos taurus Sire Breeds. In a study involving the mating of Angus, Brahman, Brangus, and AfricanderAngus sires in various combinations with Angus, Brahman, Brangus, and Africander-Angus dams, Louisiana workers (82) reported that dystocia was not a problem for any of the sire × dam mating groups. In a Georgia study (42) involving mating of Angus, Santa Gertrudis, and Gelbvieh sires to Angus and Santa Gertrudis females, calving ease values were 95.1, 98.1, and 98.3%, respectively, for females bred to Angus, Santa Gertrudis, and Gelbvieh sires; these differences were nonsignificant. Corresponding values by sire breed for percentage of calves alive at 24-h after birth were 98.6, 94.9, and 98.3%, respectively; these differences were also nonsignificant. Percentage of live calves at 24 h indicated that straightbred Santa Gertrudis calves (90.9%) were less (P<0.05) viable at birth than the other four mating types (98.6%). At another Georgia location, a grading-up and rotational crossing study (65) involving the Angus, Polled Hereford, and Santa Gertrudis breeds revealed that Santa Gertrudis sires were associated with a lesser (P<0.05) proportion of cows that had a live calf and that weaned a calf. A later study (67) at the same location revealed that the proportion of Polled Hereford females that weaned a calf was 0.82, 0.74, 0.81, and 0.78, respectively, when mated to Angus, Santa Gertrudis, Angus × Santa Gertrudis, and Santa Gertrudis ×
Angus bulls; these differences were nonsignificant. For both of these studies, the authors did not indicate how much of the observed differences between the Santa Gertrudis and the other genetic types were attributed to differences in dystocia. In a Florida study (6) involving the mating of Brangus, Simbrah, and Braford primiparous heifers to Angus bulls selected for light birth BW and calving ease during a 2-yr period, dystocia score and dystocia incidence were similar for the three dam genetic types. The dam breed × sex of calf interaction was not significant for dystocia incidence during either year or for dystocia score during yr 1, but the interaction approached significance for the latter trait during yr 2 of the study. This interaction for dystocia score seemed to be caused by the magnitude of the difference between sexes within the dam breeds (Brangus, 1.33 vs 1.00; Simbrah, 1.17 vs 1.12; Braford, 1.08 vs 1.09; male vs female, respectively). Some of these studies reveal that dystocia levels were similar for calves sired by Brahman, Santa Gertrudis, and Bos taurus bulls; other studies revealed similar dystocia levels for calves sired by Santa Gertrudis and Bos taurus bulls, but weaning rate tended to be less for females exposed to Santa Gertrudis bulls. Increased Birth BW and Gestation Length as Contributors to Increased Dystocia (Increased Mortality/Reduced Survival Rate). Birth BW. Bellows et al. (10) indicated that birth BW is a major contributor to dystocia in cattle (relative numerical ranking of four major factors affecting dystocia: calf sex = 1.00, dam precalving BW = 1.10, dam precalving pelvic area = 1.16, and calf birth BW = 3.05). Because the direct additive (17, 35, 38, 70, 84, 100) and heterotic (17, 27, 34, 36, 38, 84) effects for the Brahman breed are positive for birth BW, increased birth BW is expected to be a major contributor to increased dystocia observed when Brahman sires are mated to Bos taurus females.
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
In a study based on data collected at several locations in the Southern Region, Kincaid (51) reported that Brahman-sired calves were 1.9 kg heavier (P<0.05) than British-sired calves. Similarly, McCormick and Southwell (58) reported that Brahman-sired calves were 3.8 kg heavier (P<0.01) than Angus-sired calves, and Ellis et al. (34) reported that Brahman-sired calves were 2.2 kg heavier (P<0.01) than Hereford-sired calves. Similarly, Roberson et al. (84) reported that Brahman-sired calves were 2.3 kg heavier (P<0.01) than Hereford-sired calves. Bolton et al. (12) reported that ¼ and ½ Brahman calves were 1.4 and 3.8 kg heavier (P<0.05), respectively, than 0 Brahman calves. The results of Comerford et al. (27) indicated that Brahman-sired crossbred calves were 4.3, 5.6, and 5.9 kg heavier (P<0.05), respectively, than Simmental-, Limousin-, and Polled Hereford-sired crossbred calves. Gregory et al. (44) reported that Brahman-sired calves were 5.2, 2.9, 1.7, and 3.4 kg heavier (P<0.05), respectively, than Hereford/ Angus-, Sahiwal-, Pinzgauer-, and Tarentaise-sired calves. A Texas study (47) revealed that Brahman-sired calves were 3.7 and 7.6 kg heavier (P<0.05), respectively, than Boranand Tuli-sired calves. Another Texas study (71) indicated that Brahmansired (Gray/Red Brahman combined) calves were 5.5 (P<0.05), 4.3 (P<0.05), and 0.6 kg heavier, respectively, than Angus-, Gir-, and Nellore-sired calves, but were 1.8 kg lighter than Indu Brazil-sired calves. Crockett et al. (29) reported that Brahman-sired calves were 5.0 (P<0.01), 2.9 (P<0.01), 1.3, 0.3, and 1.5 (P<0.01) kg heavier, respectively, than Brangus-, Beefmaster-, Limousin-, Maine-Anjou, and Simmental-sired calves. Gotti et al. (42) reported that Santa Gertrudissired calves were 3.0 kg heavier (P<0.05) than Angus-sired calves, but similar to Gelbvieh-sired calves. The results of Chapman et al. (22) revealed that Santa Gertrudis-sired calves were 3.8 and 2.7 kg heavier (P<0.01), respectively, than Angusand Polled Hereford-sired calves;
however, Neville et al. (67) reported that Santa Gertrudis-sired calves were 2.8 kg lighter (P<0.05) than Angussired calves. Brown et al. (16) reported that birth BW of Brahman- and Beefmaster-sired calves were similar: 37 and 39 kg, respectively. To examine further the dystocia problem observed when sires varying in percent Bos indicus inheritance are mated to Bos taurus females, some studies have examined the interaction between sire breed and sex of calf for birth BW. A previous review (48) of factors affecting calf birth BW suggested that differences between sexes for birth BW were relatively constant across breeds. Several studies indicate that this is not the case when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. One study indicated that the sire breed × sex of calf interaction was nonsignificant for birth BW (82); however, most studies have indicated the interaction was important (19, 24, 68, 71, 90, 94, 101). Two studies indicated that the interaction was significant but did not elaborate on the nature of the interaction (27, 44). In the study of Browning et al. (19), which involved Brahman, Tuli, and Angus sires, a sex difference was detected only in Brahman-sired calves; Brahman-, Angus-, and Tulisired male calves were 4.5 (P<0.01), 1.0, and -1.0 kg heavier, respectively, than female calves. In a similar study, Chase et al. (24) revealed that Brahman-, Tuli-, and Senepol-sired male calves were 5.1 (P<0.05), 2.8, and 1.7 kg heavier, respectively, than female calves. In the study of Notter et al. (68), the interaction was important in 2-yr-old cows because of greater sexual dimorphism for birth BW in Brahman-sired calves. The mean sex difference for all crosses was 2.1 kg, but the sex difference was 4.4 kg (P<0.01) in Brahman-sired calves. A Texas study (71) involving one Bos taurus and five Bos indicus sire breeds revealed that Angus-, Brahman(Gray/Red Brahman combined), Gir-, Indu Brazil-, and Nellore-sired male calves were 2.6, 4.9 (P<0.05), 4.9
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(P<0.05), 6.8 (P<0.05), and 7.0 (P<0.05) kg heavier, respectively, than heifer calves. In the study by Gregory et al. (44), as quoted by Paschal et al. (71), Brahman-sired male calves of Hereford and Angus dams were 4.5 and 5.7 kg heavier, respectively, than heifer calves; corresponding differences in Sahiwal-sired calves were 6.2 and 5.5 kg, respectively. For the Bos taurus-sired calves, the corresponding sex differences were 2.9 and 2.0 kg in Pinzgauer crosses and 3.7 and 4.4 kg in Tarentaise crosses, respectively; in the Hereford-Angus crosses, the sex difference was 2.5 kg in Angus-sired calves and 2.0 kg in Hereford-sired calves. A Louisiana study (94) revealed that Angus-, Brahman-, Brangus-, and Hereford-sired male calves were 1.2, 4.1, 3.0, and 1.0 kg heavier, respectively, than heifer calves. A more recent Louisiana study (101) revealed that Angus-, Brahman-, Charolais-, and Hereford-sired male calves were 0.9 (P<0.05), 5.0 (P<0.01), 1.4 (P<0.01), and 1.4 (P<0.01) kg heavier, respectively, than heifer calves. Expressing results as a deviation from Angus-sired calves, Nebraska workers (95) reported that Brahman-sired male calves were 3.8 kg heavier (P<0.05) than heifer calves; however, for 10 other Bos taurus sire breeds, male calves exceeded heifer calves by an average of only 0.6 kg. A Kentucky study (90), which involved two data sets, indicated that Angus and Brahman male calves exceeded (P<0.05) Angus and Brahman heifer calves by 1.9 and 2.2 kg, respectively. In contrast, Brahman 么 × Angus 乆 male calves exceeded (P<0.05) Brahman 么 × Angus 乆 heifer calves by 4.5 kg. A similar pattern was observed in the second data set. Hereford and Brahman male calves exceeded (P<0.05) Hereford and Brahman female calves by 1.7 and 2.2 kg, respectively; Brahman 么 × Hereford 乆 male calves exceeded (P<0.05) Brahman 么 × Hereford 乆 heifer calves by 5.5 kg. Similar results were observed in a Georgia study (58); Angus 么 × Hereford 乆 male calves were 0.2 kg heavier than heifer calves; however,
22
Brahman 么 × Hereford 乆 calves male calves were 2.8 kg heavier than heifer calves. Most studies reveal that Bos indicus-sired calves are heavier at birth than Bos taurus-sired calves. Also, most studies that have examined the interaction between sire breed and sex of calf reveal a larger birth BW difference between male and female Bos indicus-sired crossbred calves than for Bos taurus-sired crossbred calves. Gestation Length. A positive relationship exists between gestation length and birth BW in cattle (2, 13). Reynolds et al. (82) reported that for each 1-d increase in gestation length, calf birth BW increased by an average of 0.25 to 0.30 kg (P<0.01). Several studies have reported longer gestation length for Bos indicus cows (59, 77, 80, 82, 85). Thus, because Bos indicus cattle express a longer gestation length, it is logical to assume that the increased birth BW resulting from mating of sires varying in percent Bos indicus inheritance with Bos taurus females are due in part to calves being gestated longer. Paschal et al. (71) reported that Bos indicus-sired calves were gestated 7 to 12 d longer (P<0.05) than Angus-sired calves. The sire breed × sex of calf interaction was significant; however, the authors concluded that the interaction was probably caused by sampling error associated with the Angus sires, because Angus-sired heifer calves were gestated 2.4 d longer than Angussired bull calves. For the Bos indicussired calves, Brahman- (Gray/Red Brahman combined), Gir-, Indu Brazil-, and Nellore-sired male calves were gestated 6.0 (P<0.05), 3.4, 2.2, and 6.8 (P<0.05) d longer, respectively, than heifer calves. In the study by Gregory et al. (44), Hereford-Angus-, Brahman-, Sahiwal-, Pinzgauer-, and Tarentaisesired calves were gestated 284, 291, 294, 286, and 287 d, respectively; all sire breed groups except Pinzgauer and Tarentaise were different (P<0.01) from each other; male calves were gestated 2 d longer (P<0.01) than
Thrift et al.
heifer calves. In a Louisiana study (98), Brahman-sired calves were gestated the longest (291 d; P<0.01) followed by Chianina- (289 d), Maine-Anjou- (286 d), and Simmental-sired (286 d) calves; male calves were gestated 2.1 d longer (P<0.01) than heifer calves. A Georgia study (42) indicated that Angus-sired calves were gestated shorter (284 d; P<0.05) than Santa Gertrudis- (286 d) or Gelbvieh-sired (287 d) calves; male calves were gestated only slightly longer (0.7 d) than heifer calves. A Texas study (47), which involved Brahman, Boran, and Tuli sires, indicated that sire breed was not significant for gestation length even though Boran- and Brahman-sired calves were gestated 3 and 2 d longer, respectively, than Tuli-sired calves; male calves were gestated 1.9 d longer (P<0.05) than heifer calves. Similarly, a Louisiana study (98) revealed that male calves were gestated 2.1 d longer (P<0.01) than heifer calves. In another Texas study (19), Brahman-, Angus-, and Tuli-sired calves were gestated 293.7, 284.0, and 288.4 d, respectively; all sire differences were significant (P<0.01). The sire breed × sex of calf interaction was significant. Within sire breeds, only the Brahman group exhibited a sex difference in gestation length, as male calves were gestated 5 d longer (P<0.01) than heifer calves. In contrast, Tuli- and Angus-sired male calves were gestated 0.2 and 2.6 d longer, respectively, than heifer calves. In a Florida study (24), Brahman-, Tuli-, and Senepolsired calves were gestated 283.6, 282.0, and 281.8 d, respectively; however, these differences were not significant. Male calves tended to be gestated slightly longer (1 d) than heifer calves; the sire breed × sex of calf interaction was not significant. Reynolds et al. (82) also reported that male calves were gestated 0.6 d longer (P<0.01) than heifer calves and that the sire breed × sex of calf interaction was not significant. These studies reveal that Bos indicus-sired calves are gestated longer than Bos taurus-sired calves. Also,
relative to Bos taurus-sired calves, Bos indicus-sired male calves are gestated longer than female calves. Reproductive Performance of Brahman Bulls and Subsequent Calf Birth Date as Contributing Factors to Increased Birth BW and Dystocia. Neville et al. (66) reported that the number of days from start of the breeding period to birth of calf was similar for Angus (308 d) and Brahman (306 d) sires; however, most studies (4, 30, 38, 42, 58, 67, 69, 80– 82, 96, 97, 101) have indicated that, relative to Bos taurus-sired calves, Brahman- or Brahman-derivativesired calves are born later in the calving season. Increased gestation length attributed to the Brahman breed and the fact that some Brahman sires express poor reproductive performance (5, 25, 40, 79), some tend to clump together in multi-sire breeding units (21), and some show preferential mating habits (23, 52, 81) all contributed to the later birth date of the Brahman-sired calves. In two studies (47, 66) involving Brahman sires, calves born late in spring calving programs had larger birth weights. Thus, based on these results, increased dystocia would be expected, especially in situations involving Brahman-sired male calves that are late-born. Also, because it has been demonstrated that birth weights are increased 2 to 4 kg with increased nutrition of the cow herd during late gestation (7, 14, 28, 39, 49, 54), latecalving cows involved in a spring calving program would be expected to contribute to the slightly heavier birth BW because of their improved nutritional state relative to earlycalving cows.
Implications Dystocia is increased when sires varying in percent Bos indicus inheritance are mated to Bos taurus females. Male calves resulting from these matings express a higher incidence of dystocia than heifer calves because male calves are gestated longer and have considerably larger birth BW.
REVIEW: Dystocia in Bos indicus × Bos taurus Matings
The increased incidence of dystocia expressed by calves resulting from mating of sires varying in percent Bos indicus inheritance with Bos taurus females and the fact that Bos indicussired calves are more susceptible to cold, moist conditions within 24 h after birth (41, 50, 52, 57, 68, 82, 88, 93, 98), contributes greatly to increased calf mortality and constitutes a serious problem for producers utilizing sire breeds varying in percent Bos indicus inheritance.
Livest. Range Res. Lab., Miles City, MT. 11. Berger, P. J., A. C. Cubas, K. J. Koehler, and M. H. Healey. 1992. Factors affecting dystocia and early calf mortality in Angus cows and heifers. J. Anim. Sci. 70:1775. 12. Bolton, R. C., R. R. Frahm, J. W. Castree, and S. W. Coleman. 1987. Genotype × environment interactions involving proportion of Brahman breeding and season of birth. I. Calf growth to weaning. J. Anim. Sci. 65:42. 13. Bourdon, R. M., and J. S. Brinks. 1982. Genetic, environmental and phenotypic relationships among gestation length, birth weight, growth traits and age at first calving in beef cattle. J. Anim. Sci. 55:543. 14. Boyd, G. W., T. E. Kiser, and R. S. Lowery. 1987. Effects of prepartum energy intake on steroids during late gestation and on cow and calf performance. J. Anim. Sci. 64:1703.
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24. Chase, C. C., Jr., A. C. Hammond, and T. A. Olson. 2000. Effect of tropically adapted sire breeds on preweaning growth of F1 Angus calves and reproductive performance of their Angus dams. J. Anim. Sci. 78:1111. 25. Chenoweth, P. J. 1994. Bull behavior, sexdrive and management. In Factors Affecting Calf Crop. M. J. Fields and R. S. Sand (Ed.). p 319. CRC Press, Boca Raton, FL. 26. Colburn, D. J., G. H. Deutscher, M. K. Nielsen, and D. C. Adams. 1997. Effects of sire, dam traits, calf traits, and environment on dystocia and subsequent reproduction of two-year-old heifers. J. Anim. Sci. 75:1452. 27. Comerford, J. W., J. K. Bertrand, L. L. Benyshek, and M. H. Johnson. 1987. Reproductive rates, birth weight, calving ease and 24-h calf survival in a four-breed diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. J. Anim. Sci. 64:65.
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29. Crockett, J. R., F. S. Baker, Jr., J. W. Carpenter, and M. Koger. 1979. Preweaning, feedlot and carcass characteristics of calves sired by Continental, Brahman and Brahmanderivative sires in subtropical Florida. J. Anim. Sci. 49:900.
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