Fixed effects in the formation of a composite line of beef cattle: I. Experimental design and reproductive performance.

Red Angus (RA) dams were mated to Charolais (C) or Tarentaise (T) sires to produce crossbred (F1) progeny. Members of the F1 generation, differing in breed direct effects, were mated to produce an F2 generation with an expected breed composition of 1/2 RA, 1/4 C, and 1/4 T. Two breed groups within the F2 generation differing in breed maternal effect ([C x RA] x [T x RA] and [T x RA] x [C x RA]) were identified separately. These breed groups were crossed to produce an F3 generation and, likewise, the two resulting F3 generation breed groups were crossed to produce an F4 generation. No distinction was made among breed groups subsequent to the F3 generation. Pregnancy rates averaged 90.9% over 11 yr, with 82.0% of cows exposed weaning a calf. Among formative generations of this composite population, F2 had greatest pregnancy, calving, and weaning rates. Age of dam significantly affected pregnancy rate, calving difficulty, and gestation length. Older cows tended to express higher pregnancy rates and longer gestation lengths than did younger cows (P < .01). Males calves had a 1.7% greater weaning rate than female calves (P < .05), but matings producing male calves had longer gestation lengths (P < .05) and were 8.5% more likely to experience calving difficulty (P < .01). Individual breed additive effects (calves from C or T sires mated to RA dams) were important for calving difficulty only (P < .05), where C-sired matings experienced greater calving difficulty. Differences between C x RA and T x RA dams, indicative of maternal breed additive effects, were not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Fixed effects in the formation of a composite line of beef cattle: II. Pre- and postweaning growth and carcass composition.

Generation, age of dam, sex of calf, and certain covariates were studied to elucidate their effect on traits related to growth and carcass characters measured on individuals from a stabilized three-breed composite (1/2 Red Angus [RA], 1/4 Charolais [C], 1/4 Tarentaise [T]). There was evidence that sires had been selected for yearling weight. Thus, an animal model was fitted to the data to estimate the effects free of bias due to selection. Differences between generations were not different from zero (P > .05) for birth weight, weaning weight, and preweaning ADG. There were few important differences between generations for carcass traits as well. This may have been caused by confounding of individual and maternal heterotic effects with direct and maternal components of the model, or the partial confounding of years, age of dam, and generation. Birth weight was curvilinear with respect to calving day (P < .01). Age of dam was important for all growth traits except postweaning ADG. In general, growth of calves increased with increasing age of dam, as did carcass weight and predicted retail product. Individual breed additive effects (differences between calves sired by C and T sires mated to RA dams) were positive for birth weight (P < .01), weaning weight (P < .05), carcass weight (P < .05), and predicted retail product (P < .05). Maternal breed additive effects (differences between calves out of C x RA or T x RA dams) were also positive for weaning weight (P < .05), carcass weight (P < .05), and fat depth (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Paternal half-sib heritabilities and genetic, environmental, and phenotypic correlation estimates from randomly selected Hereford cattle.

Growth and carcass data were collected during 10 yr at the Fort Keogh Livestock and Range Research Laboratory in Miles City, MT from a Hereford herd selected at random. The objective was to compare genetic parameter estimates from this randomly selected herd with estimates from published selection studies. Only bulls were included in the data set. Bulls were slaughtered between 14 and 17 mo of age. Genetic parameters were estimated by the paternal half-sib procedure. Data were subdivided into three subgroups: 1) all bulls that had birth weights, 2) bulls with complete records for growth traits, and 3) bulls with complete carcass and growth records. The heritability estimate for birth weight on 736 progeny from 86 sires was .18. The second group included 616 progeny representing 85 sires and heritability estimates were weaning weight, .17; daily gain from birth to weaning, .20; final test weight, .42; and daily gain on test, .47. The third group included 401 progeny from 75 sires and heritability estimates were carcass weight, .38; longissimus muscle area, .51; marbling, .31; slaughter weight, .42; and dressing percentage, .25. Thus, these estimates of heritability were in quite good agreement with previously published values, with a tendency for these estimates to be lower for early growth weights. Phenotypic and environmental correlations were in good agreement and genetic correlations were in general agreement with the data reviewed. Estimates of heritabilities from this herd selected at random were not larger than previous estimates from selected herds.

Maternal breed of sire effects on postweaning performance of first-cross heifers and production characteristics of 2-year-old heifers.

Postweaning growth rates from weaning to 18 mo, fall condition score, pregnancy rates, and production to 2 yr of age were evaluated in a study of Angus (A)-, Pinzgauer (P)-, Red Poll (R)-, Simmental (S)-, and Tarentaise (T)-sired females from Hereford dams. First-cross heifers from the different sire breeds did not differ (P greater than .10) in initial weight. During a 140-d feed test, S gained 98.6 kg, exceeding (P less than .05) gains of P, 92.3; A, 91.4; and R, 87.3 kg but not T, 94.1 kg. Red Poll-sired heifers weighed less at the end of the 140-d test (P less than .05) than the other crosses, which did not significantly differ from each other. No breed of sire differences were found in gain from 140 d to fall weight. Simmental-sired heifers weighed more (P less than .05) than A- and R-sired heifers at 18 mo. Breed of sire and year interacted to affect pregnancy rate of the yearling heifers when mated to Shorthorn sires for 45 d. Percentage of dystocia varied from a low of 26.3 and 28.9% for T- and A-sired heifers, respectively, to 54.4 and 60.8% for P- and S-sired heifers, respectively (P less than .05). Age of dam of heifers affected (P less than .05) weight at the different period end points but not gains after weaning. Age of dam also affected incidence of dystocia. Two-year-old heifers from young dams had more dystocia than heifers from older dams. Shorthorn-sired calves from 2-yr-old heifers with different sire breeds differed in birth weight (P less than .05) but not survival from birth to weaning, ADG from birth to weaning, weaning age, or weaning condition score. Average 200-d weight of calves from P-, S- and T-sired heifers exceeded those from A- and R-sired heifers by 10.7 kg, or 5.7%.

Maternal breed of sire effects on postweaning performance of heifer and steer progeny: postweaning growth and carcass characteristics.

Heifer and steer progeny of 2-yr-old first-cross (F1) heifers and 3- to 6-yr-old F1 cows, from Hereford dams and five sire breeds, were evaluated for postweaning feedlot growth and carcass composition. Breeds of sire of dam were Angus (A), Red Poll (RP), Tarentaise (T), Simmental (Sm), and Pinzgauer (P). Calves from 2-yr-old heifers were sired by Shorthorn, and calves from 3- to 6-yr-old dams were sired by Charolais. Breed of sire of dam was significant (P less than .05 to P less than .01) for total gain and final weight for female progeny from 2-yr-old dams. At all weights, Sm, P, and T ranked above A and RP. Progeny of A, P, Sm, and T F1 2-yr-old dams were not significantly different but were higher (P less than .05) than RP heifers in total feedlot gain. Breed of sire of dam was significant (P less than .05) for carcass weight and longissimus muscle area; T ranked highest and RP lowest. Breed was not significant for any growth traits of steer progeny of 2-yr-old dams. Breed was significant for marbling score; A ranked highest and exceeded (P less than .01) both RP and Sm steers. Breed was significant (P less than .05) for most growth traits in the heifer progeny of the 3- to 6-yr-old dams bred to Charolais sires. Heifer calves of the Sm group were heavier (P less than .05) than all other groups for most weights and total gain. For total gain, P and T were intermediate and A and RP lowest. For heifer carcass traits from 3- to 6-yr-old dams, breed was significant (P less than .05 to P less than .01) for carcass weight, longissimus muscle area, percentage of cutability, and estimated kidney, heart, and pelvic fat. Heifers from Sm-sired dams were heavier (P less than .05) than those from all other groups but ranked second to heifers from P for percentage of cutability. Marbling scores of RP heifer carcasses ranked highest of all groups. Breed was not significant (P greater than .05) for any of the weights or gains in steer progeny of 3- to 6-yr-old dams; however, the Sm and P groups ranked above A and RP for all feedlot test weights.(ABSTRACT TRUNCATED AT 250 WORDS)

Heritabilities and genetic correlations for postweaning growth and feed intake of beef bulls and steers.

Data from studies conducted at Miles City, MT and Lethbridge, AB were pooled to evaluate genetic and environmental variation in feed intake (MEI), growth rate (ADG), MEI-to-gain ratio (M/G), final weight (FWT), and fat thickness (FAT). A total of 124 sires with an average of 4.25 progeny each were represented in the data. Restricted maximum likelihood methods were used to estimate within and between paternal half-sib estimates of variance and covariance. Heritabilities and genetic, phenotypic, and environmental correlations with inference to populations at 365 d of age were calculated from the estimates. Heritabilities were as follows: ADG, .38 +/- .16; MEI, .45 +/- .17; M/G, .26 +/- .15; FWT .25 +/- .15; and FAT .52 +/- .17. The genetic correlation of MEI with ADG was large (.73 +/- .13) and antagonistic to genetic improvement of M/G through selection for ADG. Efficient genetic improvement in M/G was found to depend on using either MEI or an indicator of composition of gain as selection criteria in addition to ADG. Selection to improve M/G using an index that included FWT and FAT, in addition to MEI and ADG, resulted in greater predicted response in ADG and lesser predicted response in MEI than the index of ADG and MEI alone.

Genetic parameters by son-sire covariances for growth and carcass traits of Hereford bulls in a nonselected herd.

Growth rates and weights at weaning, 365 d, and at slaughter were obtained on 616 bulls in a nonselected Hereford herd over a 10-yr period beginning in 1978. Carcass data were obtained for 401 of these bulls at 16 mo of age and on 101 that were sires or alternates and slaughtered at 30 mo of age. Fifty-five bulls slaughtered at 30 mo of age sired 301 male offspring on which growth data were obtained and 30 sired 169 male offspring on which carcass data were obtained. Bulls gained an average of .75 kg/d preweaning and 1.16 kg/d postweaning on a 168-d feed test. Rate of daily gain from the end of feed test to slaughter ranged from .7 to 1.2 kg/d. Time from the end of the feed test to slaughter ranged from 48 to 140 d. Slaughter weight, marbling score (Small = 12, Traces = 6), longissimus muscle area, fat covering over the 12th rib, percentage of kidney, pelvic and heart fat (KPH), and dressing percentage for bulls slaughtered as yearlings were 470 kg, 7.6 score, 82.5 cm, 8.2 mm, 1.0%, and 58.8%, respectively. The 30-mo-old bulls were slaughtered directly from range pastures. Marbling was devoid or practically devoid and fat covering over the 12th rib and KPH fat were insufficient to measure or estimate accurately. Sufficient variation was not available for statistical analyses of these traits. Slaughter weight, longissimus muscle area, and dressing percentage of 30-mo-old bulls were 583 kg, 91.8 cm, and 54.0%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological type effects on postweaning growth, feed efficiency and carcass characteristics of steers.

Postweaning growth, feed consumption and carcass characteristics of 259 individually fed F1 Angus-, Red Poll-, Pinzgauer-, Simmental- and Tarentaise-sired steers from Hereford dams were compared. Average daily gain to 382 d of age for Simmental-sired steers exceeded (P less than .05) the ADG for Red Poll, Angus and Pinzgauer, which were not different. Tarentaise-sired steers were intermediate in growth rate. Simmental-sired steers required less (P less than .05) feed per kilogram of gain than Red Poll- and Angus-sired steers to reach either 382 d of age or 400 kg. Feed conversion (FC) by Simmental, Pinzgauer and Tarentaise-sired steers did not differ (P greater than .05), nor did FC by Red Poll- and Angus-sired steers to reach 382 d or 400 kg. Angus-sired steers required less ME per kilogram of gain to reach 12.7 mm of carcass backfat than did Red Poll-, Pinzgauer- or Tarentaise-sired steers, which were similar. Simmental-sired steers were intermediate in feed conversion to 12.7-mm fat depth and did not differ from the other breed groups. Rankings of breed groups for traits indicative of lean tissue growth were similar to rankings for live animal growth traits. At age- and weight-constant endpoints, Angus-sired steers had more (P less than .05) fat cover and marbling than did steers sired by the other breeds. At these endpoints, Red Poll-sired steers also had more (P less than .05) fat cover than did Pinzgauer-, Simmental- and Tarentaise-sired steers, which were similar.

Biological type effects on gestation length, calving traits and calf growth rate.

Gestation length, birth weight calving difficulty, calf mortality rate at birth, calf mortality rate from birth to weaning, preweaning calf growth rate and calf 200-d weight were evaluated in a biological type study in which four sire breeds were bred by AI to Hereford dams. Angus and Red Poll sires represented breeds of medium size, and Pinzgauer and Simmental sires represented large breeds. Angus and Pinzgauer represented breeds with medium milk production, and Red Poll and Simmental represented breeds with high milk production. Dams mated to large sire breeds had longer (P less than .01) gestation lengths (.95 d) and higher calving difficulty scores than dams mated to medium-sized sire breeds. Calves from large sire breeds had heavier birth weight (P less than .01) and 200-d wt (6.1 kg; P less than .01) than calves from medium-sized sire breeds. Calf death loss and ADG to weaning were similar (P greater than .10) for all breeds of sire. Calves from the higher milk level sire breeds exceeded the medium-milk breeds in birth weight (1.3 kg; P less than .01) but did not (P greater than .10) in other traits. Calves from the higher milk level sire breeds exceeded the medium-milk breeds in birth weight (1.3 kg; P less than .01) but not (P greater than .10) in other traits. Interaction between size and milk production of sire breed existed for gestation length, birth weight, ADG from birth to weaning and 200-d calf weight (P less than .01). In general, mature size of sire breed was a good indication of expected performance traits not easily influenced by environment. Not all differences, however, could be explained by size and milk production of the size breed.

Comparison of two- and three-way rotational crossing, beef x beef and beef x Brown Swiss composite breed production: postweaning growth and carcass traits.

Data collected from steer and bull progeny, fed to a constant final feedlot weight over 11 yr, were used to estimate heterosis in post-weaning feedlot growth and carcass traits in two-way and three-way rotational crossing systems and a breed composite from crossing Hereford, Angus and Charolais breeds. Steer and bull progeny from matings of beef x Brown Swiss-cross sires and dams also were compared with the straight beef breeds and beef crosses. Growth traits evaluated were initial weight on test, 112-d weight, total feedlot average daily gain and total days from initial to final weight. Carcass traits included hot carcass weight, dressing percentage, rib eye area, 12th-rib fat thickness, kidney, pelvic and heart fat, yield grade and marbling score. Heterosis estimates for calves of all crossing systems were significant for initial and 112-d weight and for saving of days in the feedlot, but not for average daily feedlot gain. Heterosis estimates were small and nonsignificant for most carcass traits except for fat traits in specific crosses. Males from Hereford and Angus sires mated to Angus x Hereford dams had higher (P less than .10) backfat than did the parental average. Male progeny from Charolais ranked higher (P less than .10 to P less than .01) than calves from Hereford and Angus sires for most growth traits. Progeny from Charolais sires were more desirable (P less than .10 to P less than .01) for traits related to cutability, but they had less (P less than .05 to P less than .01) marbling than calves of Angus sires.(ABSTRACT TRUNCATED AT 250 WORDS)

Heritabilities and genetic correlations of growth and reproductive measurements in Hereford bulls.

Weight, hip height, heart girth, pelvic height, pelvic width and scrotal circumference were measured at 403 and 490 d on 427 Hereford bulls. The bulls were members of a random-selection herd so estimates of genetic parameters should have a minimum of bias due to selection. Heritabilities and genetic correlations were estimated by normal paternal half-sib (PHS) correlation procedures. In addition, 256 son-sire pairs (RSS) were used to estimate heritabilities and genetic correlations by regression and covariance methods. The PHS method produced heritability estimates in the range of .41 to .58 for all measures at both ages, with the exceptions of hip height at 403 d (.24) and pelvic height at 490 d (.23). The estimates derived in the RSS method ranged from .10 to .60. The RSS relationship would contain a portion of any maternal X direct covariance effects. A difference in heritability estimated by the two methods could be a reflection of this covariance. Genetic correlations tended to be larger than phenotypic and, in several cases, were negative. The difference in the correlation between two measurements taken at 403 d vs the same correlation estimated at 490 d was not readily explainable but may be evidence for differences in maturation rates or maternal effects. Scrotal circumference had a positive genetic correlation with weight and heart girth and near 0 or negative genetic correlations with pelvic measures. Hip height had positive genetic correlations with weight and heart girth at 403 and 490 d and with pelvic measurements at 403 d, but the correlations were not as large at 490 d.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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

Genetic variance components of birth weight in a herd of unselected cattle.

Two replicates of a randomly selected herd of Hereford cattle have been developed at the Livestock and Range Research Station in Miles City, Montana. Dams were first bred to a random selection of bulls in 1976. For this study, birth weights of 1,012 calves born in 1977 through 1983 were adjusted for sex, age of dam and year effects. Analyses were on the entire data set and a series of subsets. Subsets were determined by parental birth weights, either above (H) or below (L) the overall mean for parents of that sex. Subsets were: H sires X random dams; L sires X random dams; random sires X H dams; random sires X L dams; H sires X H dams; H sires X L dams; L sires X H dams and L sires X L dams. Two additional subsets were termed assortative (H X H and L X L) and disassortative (H X L and L X H) matings. Genetic variance components including additive direct effects (sigma 2A), additive maternal effects (sigma 2M) and a covariance between transmitted and maternal effects (sigma AM) were estimated by solving simultaneous equations after estimating coefficients for offspring-sire, offspring-dam and offspring-midparent mean regressions and a paternal half-sib covariance. Estimates for heritability of direct effects, heritability of maternal effects and the genetic correlation between transmitted and maternal effects (h2 A, h2M and rAM) were .36, .82 and -.51, respectively, in the overall data set but varied considerably when estimated in the subsets.(ABSTRACT TRUNCATED AT 250 WORDS)

Preweaning growth rate and weaning traits of Angus, zebu and zebu-cross cattle.

A 4-yr study was conducted on the preweaning growth rate and weaning traits of 620 calves from: (1) Angus (A), Brahman (B), Brangus (BR) and Africander-Angus (AF) dams sired by A and B bulls; (2) BR dams mated to BR sires and (3) AF dams mated to AF sires. Heifers were placed in the breeding pastures as 2-yr-olds and exposed to bulls for 75 d. Breed groups differed (P less than .01) in weaning age (WA), average daily gain to weaning (ADG), 205-d weight (WW), conformation score and condition score. The reciprocal (A x B and B x A) crossbred calves exceeded (P less than .01) the straightbred A and B calves by 161 g (25.2%) in ADG, 36.6 kg (23.1%) in WW and 1.3 (16.7%) in condition score, but were not different in WA or conformation score. The WW of the A x B and B x A crossbred calves were similar, 194.6 and 194.2 kg, respectively. Calves sired by A bulls were born earlier (P less than .01) in the year and had higher conformation and condition scores than calves sired by B bulls. Calves sired by B bulls from BR and AF dams exceeded (P less than .01) the ADG and WW of calves sired by A bulls by 50 g and 15.6 kg, respectively. Calves from A dams were older (P less than .01) at weaning and had higher conformation scores but gained less rapidly than calves from B dams. The BR calves exceeded (P less than .01) the AF calves in WW by 14.5 kg, and the crossbred calves from BR dams exceeded (P less than .01) the crossbred calves from AF dams by 12.3 kg. Mating BR or AF dams to A sires to obtain crossbred calves did not improve calf rate of gain or weaning weight.

Factors influencing gestation length, birth weight and calf survival of Angus, Zebu and Zebu cross beef cattle.

Day of birth in a calendar year (DB), gestation length (GL), birth weight (BW) and survival rate of calves (SR) were recorded for 4 years for single-sire matings of (1) Angus (A) and Brahman (B) sires to A, B, Brangus (BR) and Africander-Angus (AF) dams; (2) BR sires to BR dams, and (3) AF sires to AF dams, a total of four straightbred and six crossbred breed groups. Sex (S) differences were found for GL, BW and SR (P less than .05 to P less than .01), but not for DB (P greater than .05). Age of dam had no effect on GL but influenced DB (P less than .01), BW (P less than .01) and SR (P less than .05). Precalving weight of the dam influenced BW (P less than .01) but not GL. Birth weight was influenced by GL (P less than .01). Differences among breed groups were found for all traits. Purebred A had the shortest GL and the earliest BD, while purebred B had the longest GL, the latest BD, th lightest BW and the lowest SR of any of the breed groups. The BR and AF had higher BW but were generally intermediate to the A and B in other traits. Combined breed of sire and dam effects acccounted for most of the breed differences. The response and percentage heterosis obtained for such traits as DB and SR depended upon characteristics of the breeds involved and environmental factors such as date of breeding season and weather at calving. Heterosis calculated as a percentage of the A and B average was not significant for DB or GL but was 15% for BW and 14% for SR.