Growth and pubertal development in Brahman-, Boran-, Tuli-, Belgian Blue-, Hereford- and Angus-sired F1 bulls

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

Birth and weaning traits in crossbred cattle from Hereford, Angus, Brahman, Boran, Tuli, and Belgian Blue sires

The objective of this study was to characterize breeds representing diverse biological types for birth and weaning traits in crossbred cattle. Gestation length, calving difficulty, percentage of unassisted calving, percentage of perinatal survival, percentage of survival from birth to weaning, birth weight, BW at 200 d, and ADG were measured in 2,500 calves born and 2,395 calves weaned. Calves were obtained by mating Hereford, Angus, and MARC III (one-fourth Hereford, one-fourth Angus, one-fourth Pinzgauer, and one-fourth Red Poll) mature cows to Hereford or Angus (British breed), Brahman, Tuli, Boran, and Belgian Blue sires. Calves were born during the spring seasons of 1992, 1993, and 1994. Sire breed was significant for all traits (P < 0.002). Offspring from British breeds and the Belgian Blue breed had the shortest gestation length (285 d) when compared with progeny from other sire breeds (average of 291 d). Calving difficulty was greater in offspring from Brahman sires (1.24), whereas the offspring of Tuli sires had the least amount of calving difficulty (1.00). Offspring from all sire breeds had similar perinatal survival and survival from birth to weaning (average of 97.2 and 96.2%, respectively), with the exception of offspring from Brahman sires, which had less (92.8 and 90.4%, respectively). Progeny of Brahman sires were heaviest at birth (45.7 kg), followed by offspring from British breed, Boran, and Belgian Blue sires (average of 42.4 kg). The lightest offspring at birth were from Tuli sires (38.6 kg). Progeny derived from Brahman sires were the heaviest at 200 d (246 kg), and they grew faster (1.00 kg/d) than offspring from any other group. The progeny of British breeds and the Belgian Blue breed had an intermediate BW at 200 d (238 kg) and an intermediate ADG (average of 0.98 kg/d). The progeny of Boran and Tuli sires were the lightest at 200 d (227 kg) and had the least ADG (0.93 kg/d). Male calves had a longer gestation length, had a greater incidence of calving difficulty, had greater mortality to weaning, were heavier, and grew faster than female calves. Sire breed effects can be optimized by selection and use of appropriate crossbreeding systems.     

Preweaning efficiency for mature cows of breed crosses from tropically adapted Bos indicus and Bos taurus and unadapted Bos taurus breeds

Production data were collected on mature cows produced by mating Angus and Hereford (pooled AH), Brahman (Bh) and Boran (Br), and Tuli, a tropically adapted Bos taurus, sires by AI or natural service to Angus and Hereford cows. These cows were mated to Charolais bulls for the purpose of this study. Within each sire breed of cow, cows were assigned randomly to one of three feeding rates, 49 or 76 g of DMI/ BW0.75 or ad libitum (10 to 12 cows/feeding rate group), with weekly individual animal feed consumption recorded. Lactation yields were recorded via the weigh-suckle-weigh protocol at approximately 14, 28, 56, 84, 112, 140, 168, and 196 d postpartum for each cow/calf pair. Means for milk yield at peak lactation, total milk yields, calf birth weight, age-adjusted weaning weights, preweaning daily gain, and feed efficiency were estimated. Peak yield (kg/d) for Bh (10.3 +/- 0.36) was greater (P < 0.05) than for Tuli (9.0 +/- 0.31). Total yield (kg, 212 d) for Bh (1802 +/- 68) was greater (P < 0.05) than for Tuli (1532 +/- 59). Birth weight of AH (44 +/- 0.9) was heavier than for Bh and Br (P < 0.05). Preweaning daily calf gain (g/d) and adjusted weaning weight (kg) of Bh (813 +/- 28, 212 +/- 6.1) and Br (766 +/- 24, 202 +/- 5.1) differed (P < 0.05) from AH (589 +/- 24, 169 +/- 5.2) and Tuli (634 +/- 24, 176 +/- 5.3). Efficiency estimates (grams of adjusted weaning weight/kilograms DMI of the cow) for Bh (88 +/- 2.5) and Br (85 +/- 2.1) exceeded (P < 0.05) those for Tuli (74 +/- 2.1) and AH (73 +/- 2.1). Bos indicus breed crosses exhibited greater peak and total yield, lower birth weight, greater daily gain and adjusted weaning weight, and higher feed efficiency than did Bos taurus breed crosses (P < 0.05). Total yield, daily gain, adjusted weaning weight, and feed efficiency were higher (P < 0.05) for cows sired by bulls from tropically adapted breeds, and the peak yield was less (P < 0.10). Tuli exhibited lower total yield and birth weight than did Angus/Hereford (P < 0.05). The efficiency of crossbred Tuli cows did not differ from Angus/Hereford F1 females, but neither equaled the efficiency of crossbred cows produced using Bos indicus breeds.     

Growth and pubertal development of F1 bulls from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu sires

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

Birth and weaning traits in crossbred cattle from Hereford, Angus, Norwegian Red, Swedish Red and White, Wagyu, and Friesian sires

The objective of this study was to characterize breeds representing diverse biological types for birth and weaning traits in crossbred cattle (Bos taurus). Gestation length, calving difficulty, percentage of unassisted calving, percentage of perinatal survival, percentage of survival from birth to weaning, birth weight, weaning weight, BW at 205 d, and ADG was measured in 1,370 calves born and 1,285 calves weaned. Calves were obtained by mating Hereford, Angus, and MARC III (1/4 Hereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) mature cows to Hereford or Angus (British breeds), Norwegian Red, Swedish Red and White, Wagyu, and Friesian sires. Calves were born during the spring of 1997 and 1998. Sire breed was significant for gestation length, birth weight, BW at 205 d, and ADG (P < 0.001). Offspring from Swedish Red and White and Friesian had the shortest gestation length (282 d), whereas offspring from Wagyu sires had the longest gestation length (286 d). Progeny from British breeds were the heaviest at birth (40.5 kg) and at 205 d (237 kg), and grew faster (0.97 kg/d) than offspring from other breeds. Offspring from Wagyu sires were the lightest at birth (36.3 kg) and at 205 d (214 kg), and had the slowest growth (0.91 kg/d). Dam breed was significant for gestation length (P < 0.001), birth weight (P = 0.009), BW at 205 d, and ADG (P < 0.001). Offspring from Hereford cows had the longest gestation length (284 d), whereas offspring from Angus cows had the shortest (282 d). Offspring from MARC III cows were the heaviest at birth (39.4 kg) when compared with offspring from Hereford (38.2 kg) and Angus (38.6 kg) cows. Progeny from Angus cows were the heaviest at 205 d (235 kg) and grew faster (0.96 kg/d), whereas offspring from Hereford cows were the lightest at 205 d (219 kg) and were the slowest in growth (0.88 kg/d). Sex was significant for gestation length (P = 0.026), birth weight, BW at 205 d, and ADG (P < 0.001). Male calves had a longer gestation length (284 d) when compared with female calves (283 d). Males were heavier than females at birth and at 205 d, and grew faster. Sire breed effects can be optimized by selection and use of appropriate crossbreeding systems.     

Maternal and reproductive performance of Brahman x Angus, Senepol x Angus, and Tuli x Angus cows in the subtropics

To determine the maternal and reproductive performance of F1 cows in the subtropics, 42 Brahman x Angus, 34 Senepol x Angus, and 50 Tuli x Angus cows were bred to Angus bulls to calve first and subsequently bred to Charolais bulls to calve as 3- to 8-yr-olds. Age at first calving did not differ among crossbred cows. Angus-sired calf birth weights were heavier (P < 0.01) from Senepol x Angus than either Brahman x Angus or Tuli x Angus cows. Weaning weights of Angus-sired calves were heavier (P < 0.01) from Brahman x Angus (213.5 kg) than either Senepol x Angus (194.9 kg) or Tuli x Angus (191.5 kg) cows. As 3- to 8-yr-old cows, calf birth weights were heavier (P < 0.05) from Senepol x Angus compared with Brahman x Angus but not Tuli x Angus cows. Weaning weights of Charolais-sired calves were heaviest (P < 0.05) from Brahman x Angus cows (268.9 kg), lightest from Tuli x Angus cows (233.4 kg), and intermediate from Senepol x Angus cows (245.0 kg). Calf crop born and calf crop weaned were lowest (P < 0.05) for Senepol x Angus cows (76.9 and 70.2%) and did not differ between Brahman x Angus (89.0 and 86.1%) and Tuli x Angus (94.7 and 86.5%) cows. Tuli x Angus cows tended (P < 0.10) to have a lower percentage of unassisted births and lower (P < 0.10) calf survival to weaning than Brahman x Angus cows but not Senepol x Angus cows. As 3- to 8-yr-olds, weaning weight per cow exposed was greatest (P < 0.05) for Brahman x Angus (234.2 kg), least (P < 0.05) for Senepol x Angus (173.0 kg), and intermediate (P < 0.05) for Tuli x Angus (209.1 kg) cows. Also as 3- to 8-yr-olds, efficiency (205-d calf weight per 100 kg of cow exposed) was similar for Brahman x Angus (42.2) and Tuli x Angus cows (40.7), and both were greater (P < 0.01) than for Senepol x Angus cows (33.8). These data indicate that, in the subtropics, maternal and reproductive performance of Tuli x Angus cows, but not Senepol x Angus cows, was comparable to Brahman x Angus cows, except for lower calf survivability and weaning weight.     

Characterization of topcross progenies from Hereford, Limousin, and Piedmontese sires

Breeds of larger mature size tend to grow more rapidly and be older when attaining a given level of fatness. Hereford, Limousin, and Piedmontese are of approximately equal mature size and yet may vary in body composition at a given degree of maturity. However, direct comparisons among these three breeds were not found. Therefore, the objective of this research was to compare Hereford, Limousin, and Piedmontese progenies for economically important traits. Crossbred cows were bred to Hereford (n = 23), Limousin (n = 24), or Piedmontese (n = 24) sires. Male calves were either left intact or castrated at approximately 2 mo of age. Calves remained with their dams until weaning at an average age of 179 d. Male calves were then individually fed a growing ration until they reached 386 kg and then fed a finishing ration either 90 or 132 d. They were then slaughtered at a commercial abattoir and carcass data were collected. Female calves were group-fed and used to examine nutritional effects on age at puberty. Data were analyzed using REML and linear contrasts among the breed-of-sire effects evaluated. Herefordsired calves had shorter gestation periods and weighed less at birth than either Limousin- or Piedmontese-sired calves. Calving difficulty of Hereford- and Limousin-sired calves was less than that of Piedmontese-sired calves. Limousin-sired calves tended to grow more rapidly than Hereford-sired calves. By the finishing phase, Limousin- and Hereford-sired calves had greater average daily gains than Piedmontese-sired calves. Differences in dry matter intake among breeds of sire were relatively small. Differences in carcass weight, longissimus muscle area, fat depth, and percentage kidney, pelvic, and heart fat resulted in a clear stratification of USDA yield grade between breeds of sire. Differences in percentage primal cuts were similar to those for USDA yield grade. Hereford-sired calves had more marbling than progeny of Limousin or Piedmontese sires. However, the force necessary to shear cores from steaks of Piedmontese-sired calves was less than for progeny of Limousin or Hereford sires. Hereford- and Piedmontese-sired heifers were younger at puberty than Limousin-sired heifers. Within breeds of similar mature size and growth rate, ample variation exists in age at puberty and body composition at an approximately equal degree of maturity.     

Characterization of biological types of cattle (Cycle V): carcass traits and longissimus palatability

Carcass (n = 854) and longissimus thoracis palatability (n = 802) traits from F1 steers obtained from mating Hereford, Angus, and MARC III cows to Hereford or Angus (HA), Tuli (Tu), Boran (Bo), Brahman (Br), Piedmontese (Pm), or Belgian Blue (BB) sires were compared. Data were adjusted to constant age (444 d), carcass weight (333 kg), fat thickness (1.0 cm), fat trim percentage (21%), and marbling (Small00) end points. Results presented in this abstract are for age-constant data. Carcasses from BB- and HA-sired steers were heaviest (P < 0.05) and carcasses from Bo- and Tu-sired steers were lightest (P < 0.05). Adjusted fat thickness was greatest (P < 0.05) on carcasses from HA-sired steers and least (P < 0.05) on carcasses from BB- and Pm-sired steers. Numerical USDA yield grades were lowest (P < 0.05) for carcasses from Pm- and BB-sired steers and highest (P < 0.05) for carcasses from HA- and Br-sired steers. Marbling scores were highest (P < 0.05) for carcasses from HA- and Tu-sired steers and lowest (P < 0.05) for carcasses from Br-, BB-, and Pm-sired steers. Longissimus thoracis from carcasses of HA-, Pm-, and Tu-sired steers had the lowest (P < 0.05) 14-d postmortem Warner-Bratzler shear force values. Carcasses from HA-sired steers had longissimus thoracis with the highest (P < 0.05) tenderness ratings at 7 d postmortem. Longissimus thoracis from carcasses of Br- and Bo-sired steers had the highest (P < 0.05) Warner-Bratzler shear forces and the lowest (P < 0.05) tenderness ratings at 7 d postmortem. Adjustment of traits to various slaughter end points resulted in some changes in sire breed differences for carcass traits but had little effect on palatability traits. Carcasses from BB- and Pm-sired steers provided the most desirable combination of yield grade and longissimus palatability, but carcasses from HA-cross steers provided the most desirable combination of quality grade and longissimus palatability. Tuli, a breed shown to be heat-tolerant, had longissimus tenderness similar to that of the non-heat-tolerant breeds and more tender longissimus than the heat-tolerant breeds in this study.     

Effects of Tuli,Senepol, Brahman,Angus, and Polled Hereford Sire Breeds on Birth and Weaning Traits of Offspring

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.     

Maternal grandsire,granddam, and sire breed effects on growth and carcass traits of crossbred cattle

Postweaning growth, feed efficiency, and carcass traits were analyzed on 1,422 animals obtained by mating F1 cows to F1 (Belgian Blue x British breeds) or Charolais sires. Cows were obtained from mating Hereford, Angus, and MARC IIIHereford, 1/4 Angus, 1/4 Pinzgauer, and 1/4 Red Poll) dams to Hereford or Angus (British breeds), Tuli, Boran, Brahman, or Belgian Blue sires. Breed groups were fed in replicated pens and slaughtered serially in each of 2 yr. Postweaning average daily gain; live weight; hot carcass weight; fat depth; longissimus area; estimated kidney, pelvic, and heart fat (percentage); percentage Choice; marbling score; USDA yield grade; retail product yield (percentage); retail product weight; fat yield (percentage); fat weight; bone yield (percentage); and bone weight were analyzed in this population. Quadratic regressions of pen mean weight on days fed and of cumulative ME consumption on days fed were used to estimate gain, ME consumption and efficiency (Mcal of ME/kg of gain) over time (0 to 200 d on feed), and weight (300 to 550 kg) intervals. Maternal grandsire breed was significant (P < 0.01) for all traits. Maternal granddam breed (Hereford, Angus, or MARC III)was significant (P < 0.05) only for fat depth, USDA yield grade, retail product yield, fat yield, fat weight, and bone yield. Sire breed was significant (P < 0.05) for live weight, hot carcass weight, longissimus area, and bone weight. Sex class was a significant (P < 0.001) source of variation for all traits except for percentage Choice, marbling score, retail product yield, and fat yield. Interactions between maternal grandsire and sire breed were nonexistent. Sire and grandsire breed effects can be optimized by selection and use of appropriate crossbreeding systems.     

Calving and weaning characteristics of Angus-, Gray Brahman-, Gir-, Indu-Brazil-, Nellore-, and Red Brahman-sired F1 calves

Calving and weaning data from crossbred calves sired by five Bos indicus breeds and one Bos taurus breed were evaluated. Data included calving and weaning records of F1 calves out of multiparous Hereford cows and sired by Angus, Gray Brahman, Gir, Indu-Brazil, Nellore, and Red Brahman bulls. At calving, Angus-sired calves had shorter gestations and lower (more desirable) calving ease scores and were smaller than Bos indicus-sired calves. Among the Bos indicus crosses, Gir calves had the shortest gestations, lowest calving ease scores, lightest birth weights (P less than .05), and smallest cannon bone lengths and heart girths. Nellore calves had the longest gestations (P less than .05) and largest heart girths. Calves by Indu-Brazil sires had the highest calving ease scores, highest birth weights (P less than .05), and greatest cannon bone lengths (P less than .05). Gray Brahman- and Red Brahman-sired calves were similar and intermediate for all calving characters. At weaning, Angus-sired calves had gained slightly faster than the Gir crosses and weighed more but were shorter at the hip than Gir crosses. Gir calves gained the least preweaning, weighed the least, and were shortest at weaning of the Bos indicus crosses. The Nellore and Indu-Brazil crosses were intermediate in preweaning gain and weaning weight to the Gir and the Red and Gray Brahman but were tallest at weaning. Gray Brahman and Red Brahman calves gained the most and were heaviest at weaning but were not as tall as the Nellore and Indu-Brazil.     

Daily dry matter intake to sustain body weight of mature, nonlactating, nonpregnant cows

To quantify the relationship between DM consumption, the ability to sustain BW per unit of DMI (BW stasis), and days to reach BW equilibrium among diverse cattle breeds, weekly individual cow BW and DMI data were recorded for mature, nonpregnant, and nonlactating cows sampled from Angus, Braunvieh, Charolais, Hereford, Gelbvieh, Limousin, Pinzgauer, Red Poll, and Simmental breeds. Within each breed, cows were assigned to receive 1 of 4 daily DM allowances (56, 76, 93, or 111 g.BW(-0.75, kg)) of a ground alfalfa hay-corn grain-based diet. Cows were housed in pens (space for 4 animals/pen) in open-front barns and fed individually using head gates. During the first 60 d of the experiment, BW were recorded every 28 d, after which BW were recorded on a weekly basis until the cows were determined to have attained BW equilibrium. Individual cows were determined to be at BW equilibrium when the rate of weekly BW change did not differ from 0 over an 8-wk period. The number of days to reach BW equilibrium was not affected (P > 0.79) by breed but was affected by the daily DM allowance (P < 0.003). The number of days required to attain BW equilibrium was greater as the rate of feeding (g of DM fed.BW(-0.75)) increased and ranged from 103 to 136 d. Within breed linear and the pooled quadratic regressions were significant for BW. Observed breed differences varied with feeding rate. Weight stasis estimates for mature Red Poll cows (68.3 +/- 3.8) differed (P < 0.05) from estimates for all the breeds, with the exception of Limousin (72.0 +/- 3.8), Braunvieh (74.0 +/- 4.8), and Pinzgauer (75.5 +/- 3.8) cows at the lowest feeding rate. At the 111 g.BW(-0.75) daily DM allowance, the estimates for Limousin (82.2 +/- 3.8) were greater (P < 0.05) than for the other breeds, with the exception of the Pinzgauer (81.0 +/- 4.3) and Braunvieh (75.7 +/- 3.9), which were similar to the remaining breeds in the study (P > 0.05). The change in rank of breed estimates for BW stasis suggests a breed x nutrition interaction for BW stasis.     

Maternal characteristics of young dams representing Bos taurus and Bos indicus x Bos taurus breed types

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)     

Serum leptin and its adipose gene expression during pubertal development,the estrous cycle,and different seasons in cattle

Circulating concentrations of leptin and IGF-I, leptin gene expression, and serum binding of [126I]ovine leptin in cattle during pubertal development, as well as leptin gene expression and circulating concentrations of leptin during the estrous cycle and different calendar seasons, were investigated. Multivariate regression analysis was utilized to evaluate temporal changes in BW, leptin mRNA, and serum concentrations of IGF-I and leptin normalized to the week of puberty (Exp. 1). Body weight accounted for most of the variation associated with the onset of puberty in the full regression model (R2 = 0.99; P < 0.01). However, serum leptin was closely related to changes in BW (r = 0.85; P < 0.02) and in the absence of BW was most predictive of pubertal onset (r2 = 0.73; P < 0.01). Mean concentrations of leptin increased (P < 0.0001) linearly from 16 wk before until the wk of pubertal ovulation in yearling heifers reaching sexual maturation from early spring to midsummer. Leptin mRNA transformed to a percent of the value at puberty increased (P < 0.02) as puberty approached, but serum leptin and leptin mRNA values were not well correlated. We found no evidence of leptin-binding proteins in serum of developing heifers. Combined mean serum concentrations of IGF-I (ng/mL) during periods III and IV (-9 wk to wk of puberty; 216.6 +/- 9) were 21% higher (P < 0.0001) than combined mean concentrations of IGF-I during periods I and II (-19 to wk of puberty; 193 +/- 10). In mature heifers and cows (Exp. 2), serum leptin tended to decrease (P = 0.10) during the late luteal/early follicular phase of the estrous cycle, which corresponded to a reduction (P < 0.03) in adipocyte leptin gene expression. In mature ovariectomized cows, serum concentrations of leptin increased (P < 0.001) by 34% from early winter to the summer solstice and remained unchanged throughout the remainder of the year (Exp. 3). Results from these studies indicate that marked increases in both circulating leptin and leptin gene expression occur in developing heifers during pubertal development and are associated with increases in serum IGF-I and BW. Seasonal effects on circulating leptin observed in mature cows from winter to summer could also plausibly account for a portion of the prepubertal rise in serum leptin observed in heifers.     

Growth, puberty, and carcass characteristics of Brahman-, Senepol-, and Tuli-sired F1 Angus bulls

Postweaning growth, sexual development, libido, and carcass data were collected from two consecutive calf crops using 31 Brahman x Angus (B x A), 41 Senepol x Angus (S x A), and 38 Tuli x Angus (T x A) F1 bulls. Following weaning (by mid-September) and preconditioning, at the start of the study (late September) bulls were fed concentrate (three times each week at a rate equivalent to 4.5 kg/d) on bahiagrass pasture for approximately 250 d. At the start of the study and at 28-d intervals, BW, hip height, and scrotal circumference (SC) were measured. Concurrently at 28-d intervals, when the SC of a bull was > or = 23 cm, semen collection was attempted using electroejaculation. Ejaculates were evaluated for presence of first spermatozoa (FS), 50 x 10(6) sperm with at least 10% motility (PU), and 500 x 10(6) sperm with at least 50% motility (PP). After all bulls reached PP they were subjected to two libido tests. Carcass data were collected on all bulls (n = 110) and Warner-Bratzler shear (WBS) force values were assessed on a subset (n = 80). For both years, B x A bulls were heavier (P < 0.05) and taller (P < 0.05) than S x A and T x A bulls at the start and end of the study. However, breed type did not influence (P > 0.10) gain in BW or hip height during the study. Scrotal circumference of T x A bulls was larger (P < 0.05) than that of B x A or S x A bulls at the start of the study, but there was no effect (P > 0.10) of breed type by the end of the study. At PU and PP, B x A bulls were older (P < 0.05), heavier (P < 0.05), and taller (P < 0.05) and had larger (P < 0.05) SC than S x A and T x A bulls. Tuli x Angus bulls were younger (P < 0.05) than S x A bulls at PU and PP but had similar SC. Libido scores tended (P < 0.10) to be lower for B x A than for S x A and T x A bulls. Breed type affected (P < 0.05) carcass traits; B x A bulls had the heaviest (P < 0.05) hot carcass weight, greatest (P < 0.05) dressing percentage, larger (P < 0.05) longissimus muscle area than S x A bulls, and higher (P < 0.05) USDA yield grade than T x A bulls but greatest (P < 0.05) WBS force values. Breed type did not affect (P > 0.10) USDA quality grade. In conclusion, tropically adapted F1 bulls produced from Senepol (Bos taurus) and Tuli (Sanga) sires bred to Angus cows in Florida had lighter BW, shorter hip heights, and smaller carcasses than those from Brahman sires but reached puberty earlier and had higher libido scores and lower WBS force values.     

Genetic and environmental factors associated with incidence of infectious bovine keratoconjunctivitis in preweaned beef calves

Infectious bovine keratoconjunctivitis (IBK) is one of the most economically important diseases in preweaned calves. This study examined the health records of 45,497 calves over a 20-yr period to determine environmental and genetic factors influencing the incidence of IBK. Three data sets were analyzed with an animal model. The first data set (n = 41,986) evaluated environmental factors and genetic differences among nine purebred (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental) and three composite breeds (MARC I, MARC II, and MARC III). Weaning weights of calves diagnosed with IBK were 8.9 kg lighter (P < 0.05) than weights of healthy calves. Incidence of IBK was related to age of the calf and the seasonal life cycle of the face fly (Musca autumnalis). Incidence of IBK increased in the spring (June), peaked during the summer months (July to September), and then decreased in the fall. Herefords were the most susceptible breed (P < 0.05) compared with all other purebreds and composites. Estimates of direct heritability for the incidence of IBK were generally low and ranged from 0.00 to 0.28 by breed. The maternal permanent environmental and genetic effects of the dam on the incidence of IBK were not significant for most breeds. The second data set (n = 9,606) was used to estimate heterosis for the incidence of IBK from a Hereford and Angus diallel design. The heterosis effect for the incidence of IBK in reciprocal Hereford/Angus crossbred calves was slightly negative (P = 0.12) but not large. The higher incidence of IBK in Angus x Hereford calves compared with Hereford x Angus calves (13.3 vs. 8.9%) suggests a maternal effect related to the incidence of IBK. Incidence of IBK in crossbred calves sired by tropically adapted breeds (Brahma, Boran, Tuli) compared with purebred and crossbred Bos taurus types was investigated in the third data set (n = 2,622). Crossbred calves sired by tropically adapted breeds had a lower incidence of IBK than most Bos taurus types (P < 0.05), but they were not different than either reciprocal crosses of Hereford and Angus or purebred Angus calves. Response to selection for decreasing the incidence of IBK is likely to be slow because of low heritability and low incidence in most breeds. Significant breed differences for incidence of IBK may be important to some producers and management systems.     

Effects of varying energy intake and sire breed on duration of postpartum anestrus, insulin like growth factor-1, and growth hormone in mature crossbred cows

Objectives of this study were to evaluate effects of seven sire breed groups and three levels of daily ME intake (DMEI = 132 or 189 kcal ME/kg BW(0.75) or ad libitum), beginning 5 mo prepartum, on BCS, length of postpartum anestrus, and circulating concentrations of IGF-1 and GH in F1 cows (six to eight cows per sire breed in each DMEI group) out of Angus or Hereford dams. At the initiation of the study, BW were 522, 530, 548, 572, 575, 577, and 595 kg for cows sired by Longhorn, Galloway, 1960s Hereford or Angus, 1980s Hereford or Angus, or Nellore, Salers, and Shorthorn bulls, respectively (SE = 13; P < 0.001 for sire breed). After 4 mo on DMEI treatment during the pre-partum period, cows fed 132 kcal of ME/kg BW(0.75)gained little to no BW; cows fed 189 kcal ME/kg BW(0.75) gained 50 kg; and cows fed ad libitum gained 70 kg (all groups differ P < 0.05). Concentrations of progesterone in weekly blood samples collected 2 to 14 wk after calving were used to establish when normal luteal function resumed to predict length of postpartum anestrus. Length of anestrus was affected by level of DMEI in cows sired by Galloway, Longhorn, and Nellore bulls, but not other breeds (P < 0.02 for interaction of sire breed and DMEI). Level of DMEI, but not sire breed, affected (P < 0.01) BCS at wk 2 postpartum. Concentrations of IGF-1 at wk 2 postpartum differed (P < 0.001) due to sire breed, and changes in concentrations of IGF-1 from wk 2 to 14 were influenced (P < 0.03) by the interaction of sire breed and level of DMEI; which was primarily the result of differences in rate of decrease over time among different sire breed x level of DMEI groupings. Concentrations of GH did not differ due to sire breed but varied (P < 0.001) due to the interaction of DMEI and week postpartum, for which concentrations of GH did not differ at wk 2 but increased over time at rates that were inversely proportional to level of DMEI. Length of anestrus was negatively associated (P < 0.05) with day of calving, BCS, and BW. When effects of sire breed and level of DMEI were accounted for (residual correlation), length of anestrus was inversely associated (P < 0.01) with IGF-1 concentrations. Breed of sire influenced length of postpartum anestrus and energy balance, as predicted by IGF-1, in crossbred cows fed varying levels of DMEI.     

Influence of lasalocid level on forage intake, digestibility, ruminal fermentation, liquid flow and performance of beef cattle grazing winter range

Three experiments were conducted to study the effects of lasalocid level on performance, intake, digestibility, ruminal fermentation and fluid flow of beef cattle grazing dormant, tallgrass prairie. In Exp. 1, 120 pregnant, mature beef cows of primarily Hereford breeding (avg wt = 471 kg) were randomly assigned to received 0, 100, 200 or 300 mg lasalocid X head-1 X d-1 in 1.82 kg supplement. Weight changes at 30, 60 or 90 d, condition score change and calf birth weight were not affected (P greater than .10) by lasalocid level. In Exp. 2, estimates of intake and digestibility were obtained with 40 pregnant, mature Hereford cows (avg wt = 474 kg) and 12 esophageal-cannulated, Hereford X Angus steers (avg wt = 225 kg), using Yb and indigestible acid detergent fiber as markers for fecal output and digestibility, respectively. Levels of lasalocid provided to cows and steers were similar, on a body weight (BW) basis, to those in Exp. 1 and corresponded to approximately 0, .22, .44 or .66 mg lasalocid/kg BW. Total diet and forage organic matter digestibility for beef cows decreased (P less than .01) at the .22 mg/kg BW level, but increased at the .44 and .66 mg/kg BW levels. Organic matter intake was not influenced (P greater than .10) by lasalocid addition. In Exp. 3, 16 ruminal-cannulated, Hereford X Angus steers (avg wt = 227 kg) were given the same lasalocid dosages per kg BW as in Exp. 2, and were used to study the effects of lasalocid on ruminal fermentation and fluid flow characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between terrain use and performance of beef cows grazing foothill rangeland

A study was conducted on foothills rangeland to determine whether grazing patterns differed among cow breeds and to determine whether there was a relationship between individual grazing patterns and performance of beef cows. Hereford (HH), Tarentaise (TT), 3/4 Hereford x 1/4 Tarentaise (3H1T), 1/2 Hereford x 1/2 Tarentaise (HT), and 1/4 Hereford x 3/4 Tarentaise (1H3T) cows were observed during the summers of 1997 (n = 183) and 1998 (n = 159). Locations of individual cows were recorded two to three times per week during 1.5- to 2.5-h periods in the morning by observers on horseback. Statistical models included cow breed, age, and nursing status. Data from each year were analyzed separately. During 1997 and 1998, nonlactating cows were located at greater (P < 0.05) vertical distances from water than lactating cows. In 1998, nonlactating cows used steeper (P < 0.05) slopes than lactating cows. However, nonlactating cows did not travel as far horizontally from water (P < 0.05) as lactating cows in 1997. Younger cows (3 yr) traveled further (P < 0.05) from water both vertically and horizontally than older cows (5+ yr) in 1997, but not during 1998. Tarentaise and 1H3T cows were observed at greater (P < 0.05) vertical distances from water than HH cows during both years of the study. During 1998, TT and 1H3T cows used steeper (P < 0.05) slopes than HH cows. Using residual correlations, there were no consistent relationships between topographic aspects of individual grazing locations and cow weight, height, and body condition score. In 1997, cows with earlier calving dates and correspondingly heavier calf weaning weights used areas that had greater vertical distances to water; however, in 1998 there were no relationships (P > 0.05) of calving date and weaning weight with cow location. During both years, pregnant and nonpregnant cows used terrain similarly (P > 0.05), which suggests that cow reproductive performance was not related to terrain use. Grazing patterns in foothills rangeland varied among cow breeds. Performance of cows that used more rugged topography was similar to cows using gentler terrain.     

Whole soybean supplementation and cow age class: effects on intake, digestion, performance, and reproduction of beef cows

Two experiments were conducted to determine the effects of whole soybean supplementation on intake, digestion, and performance of beef cows of varying age. Treatments were arranged in a 2 x 3 factorial with 2 supplements and 3 age classes of cows (2-yr-old, 3-yr-old, and mature cows). Supplements (DM basis) included 1) 1.36 kg/d of whole raw soybeans, and 2) 1.56 kg/d of a soybean meal/hulls supplement. Supplements were formulated to provide similar amounts of protein and energy, but a greater fat content with the whole soybeans. Supplements were individually fed on Monday, Tuesday, Thursday, and Saturday mornings. During the treatment period, cows had free choice access to bermudagrass hay [Cynodon dactylon (L.) Pers.; 8.4% CP; 72% NDF; DM basis]. In Exp. 1, 166 spring-calving Angus and Angus x Hereford crossbred beef cows were individually fed supplements for an average of 80 d during mid to late gestation. During the first 50 d of supplementation, cows fed soybean meal/hulls gained more BW (10 kg; P < 0.001) and body condition (0.18 BCS units; P = 0.004) than cows fed whole soybeans. However, BW change (P = 0.87) and BCS change (P = 0.25) during the 296-d experiment were not different between supplements. Although calves from cows fed soybean meal/hulls were 2 kg heavier at birth, there was no difference in calf BW at weaning between supplements. Additionally, first service conception rate (68%; P = 0.24) and pregnancy rate (73%; P = 0.21) were not different between supplements. In Exp. 2, 24 cows from Exp. 1 were used to determine the effect of supplement composition on forage intake and digestion; cows remained on the same supplements, hay, and feeding schedule as Exp. 1. Crude fat digestibility was the only intake or digestibility measurement influenced by supplement composition; fat digestibility was higher for cows fed whole soybeans compared with cows fed the soybean meal/hulls supplement (58.1 vs. 48.8%). Hay intake and DMI averaged 1.63 and 1.92% of BW daily, respectively. Dry matter, NDF, and CP digestibility averaged 54.1, 55.1, and 63.2%, respectively. Compared with supplementation with soybean meal/ hulls, whole soybean supplementation during mid to late gestation resulted in reduced BW weight gain during supplementation, inconsistent effects on reproduction, no effect on calf weaning weight, and no effect on forage intake or digestion.