Sire breed effects in matings with Angus cows: I. Fertility, calf survival and performance to 18 months

Over six calf crops, 524 exposures of Angus cows to three sire breeds resulted in 432 weaned calves for an 82.4% calf crop. Least-squares means for weaning rate by sire breed were 81.8, 80.5 and 83.9% for Angus, Charolais and Holsteins, respectively. Sire breed effect was not significant for calving rate, calf mortality or overall weaning rate, but was significant for all growth traits from birth to 18 mo. Angus-sired calves were smallest at birth, grew at a slower rate and were lightest in weight at all ages. Charolais-sired calves were heaviest at all weigh periods and Holstein-sired calves were intermediate. Holstein-sired calves scored significantly lower for both grade and condition than did Angus- and Charolais-sired calves. Charolais-sired calves had the highest grade. Calving rate tended to be influenced by the effect of cow (P less than .10) and sire breed X year (P less than .001). Calving rate was highest for 3-yr-old and for 6- to 10-yr-old cows and was also 1.5 percentage units higher for crossbred matings. Cow productivity (kg of calf weaned/cow exposed) is a combined measure of fertility, calf survival and weaning weight. Although sire breed did not significantly affect cow productivity (P less than .20), actual values favored cows producing crossbred calves by 14 and 9 kg for Charolais and Holstein crosses, respectively. Likewise, weight differences at 18 mo favored these crosses by 50 and 32 kg for heifers and 72 and 62 kg for steers. Among the two crossbred types, Charolais X Angus heifers were 28 kg heavier (P less than .05) than Holstein X Angus heifers at 18 mo but the 10 kg difference in steers was not significant. The fact that the large sire breeds produced calves with heavier weaning weights without demonstrating significant increases in overall productivity points out the importance of high weaning rates.     

Effect of muscle type, sire breed, and time of weaning on fatty acid composition of finishing steers

Thirty-three steer calves were used to determine the effect of sire breed (Angus or Charolais), time of weaning [normal weaned at approximately 210 d of age (NW) or late weaned at approximately 300 d of age (LW)], and muscle type [LM and semitendinosus muscle (STN)] on fatty acid composition. The whole plot consisted of a 2 (sire breed) × 2 (time of weaning) treatment arrangement, and the subplot treatment was muscle type. Body weights were recorded at 28-d intervals to determine animal performance. Muscle biopsies were collected on d 127 and 128 of finishing. All calves were slaughtered on d 138, and carcass data were collected. Angus-sired steers had lighter initial BW (271 vs. 298 kg; P = 0.02), and LW steers were heavier (351 vs. 323 kg; P = 0.03) on d 28, but no other differences in BW were noted. Charolais-sired steers had larger LM area (P = 0.03), reduced yield grades (P = 0.01), less 12th-rib fat (P < 0.01), and less marbling (P < 0.01) than Angus-sired steers. Carcass measures overall indicate Angus-sired steers were fatter. Hot carcass weight was heavier (348 vs. 324 kg; P = 0.04) in LW steers than NW steers. No other differences (P > 0.05) were observed for feedlot performance or carcass characteristics. Total lipids were extracted from muscle biopsies, derivatized to their methyl esters, and analyzed using gas chromatography. The LM had greater SFA (43.94 vs. 35.76%; P < 0.01) and decreased unsaturated fatty acids (UFA; 56.90 vs. 66.19%; P < 0.01) compared with the STN. Percent total MUFA was greater in STN than LM (51.05 vs. 41.98%; P < 0.01). Total SFA, UFA, and MUFA did not differ due to sire breed or time of weaning. Total PUFA differed (P = 0.04) due to a sire breed × time of weaning interaction but did not differ due to muscle type, with greater PUFA in NW Charolais than any other sire breed × time of weaning combination. Observed changes in percent MUFA may be a result of greater Δ(9)-desaturase activity. The calculated desaturase index suggests STN has a greater Δ(9)-desaturase activity than LM, but no differences (P > 0.05) between sire breed or time of weaning were observed. These results indicate that sire breed, time of weaning, and muscle type all affect fatty acid composition in beef. This information provides insight into factors for manipulation of beef fatty acids. More research is needed to identify beef cuts based on fatty acid profile and healthfulness.     

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.     

Comparison of Charolais and Limousin as terminal cross sire breeds

Birth, weaning, feedlot and carcass traits were evaluated on 1,181 calves sired by Charolais and Limousin bulls out of eight crossbred dam groups (Hereford X Angus, Angus X Hereford, Simmental X Angus, Simmental X Hereford, Brown Swiss X Angus, Brown Swiss X Hereford, Jersey X Angus, Jersey X Hereford). Calves were born in the spring over a 4-yr period during which dams ranged from 3 to 8 yr of age. Charolais-cross calves were 2.7 kg heavier (P less than .01) at birth and had a 9.9% higher (P less than .01) incidence of difficult calvings and 4.6% greater (P less than .05) preweaning death loss than did Limousin crosses. Charolais-sired calves out-gained Limousin-sired calves by 31 g/d (P less than .01) from birth to weaning and were 9 kg heavier (P less than .01) at weaning. After weaning, calves were self-fed a finishing diet and slaughtered as each animal attained an estimated carcass grade of low Choice. Charolais-cross calves gained 60 g/d faster (P less than .01) than Limousin crosses, were fed 6.8 fewer d and were 17.3 kg heavier (P less than .01) at slaughter. Feed efficiency was similar for both sire breeds. On a grade-equivalent basis, Charolais crosses produced 7 kg heavier (P less than .01) carcass and had 22 g more carcass weight per day of age (P less than .01). Charolais crosses had slightly less internal and external fat. Dressing percentage was higher for Limousin cross calves (64.6 vs 63.9%, P less than .01). Longissimus muscle area and carcass cutability were similar for crosses of both sire breeds.     

Pleiotropic effects in Hereford, Limousin, and Piedmontese F2 crossbred calves of genes controlling muscularity including the Piedmontese myostatin allele

Objectives were to determine 1) effects on traits measured from birth to slaughter in F2 cross calves from sire breeds that differ in potential for lean tissue growth but have similar mature BW and 2) the gene action of the mutant Piedmontese myostatin allele. Hereford (normal muscling, H), Limousin (moderate increase in muscling, L), and Piedmontese (muscular hypertrophy, P) sires (20 to 25 per breed) were bred at random to crossbred cows to produce F1 calves that were inter se-mated within sire breed to produce F2 calves that were grown out, finished, and slaughtered. Piedmontese-cross calves were genotyped for the G-A transition mutation at the myostatin locus characteristic of P (msP). Genotypes were classified on the basis of having zero (P0), one (P1), or two (P2) copies of msP (H, n = 227; L, n = 207; P0, n = 40; P1, n = 107; and P2, n = 37). Limousin-cross F2 calves had heavier birth (but dystocia was not affected) and weaning weights, gained faster, had more muscle, less fat, larger pelvic area, and more efficient feed conversion than Hereford-cross F2 calves. Normal-muscled Piedmontese-cross F2 calves (P0) were similar to Hereford-cross F2 calves except that they required less assistance at birth in heifer dams, had less fat, gained slower, were less efficient, and had larger pelvic area. Addition of msP alleles (P1 and P2) consistently increased muscle through hyperplasia, decreased fat, and increased adjusted efficiency, but many of those changes were not linear. Residual variances for breed were heterogeneous for most traits related to muscularity. This heterogeneity was caused by increased variances for L and P and(or) lower variances for H. Accounting for the msP alleles decreased the variance for P in most traits, but heterogeneity remained for most traits among the five genotypes because L remained high, H was low, and(or) P2 was low. We conclude that differences in muscularity affect most traits, and when differences in muscularity include the msP allele, there is an incremental, but not equal, change in most traits with the addition of each copy of the msP allele. Advantages of L could be captured through normal crossbreeding and selection schemes but with some caution because of potential problems from increased variability. Advantages of P could be best captured through more complex breeding and selection programs that would lessen potential negative impacts and through marketing systems that do not penalize for very low fat.     

Effects of stair-step nutrition and trace mineral supplementation on attainment of puberty in beef heifers of three sire breeds.

A study was conducted to evaluate the influence of nutrition and sire breed on age at puberty and first lactation milk yield in crossbred beef heifers. After weaning, 208 heifers sired by Hereford, Limousin, or Piedmontese bulls were assigned to either a control (CG) or stair-step gain (SSG) dietary regimen plus a mineral supplement with or without Cu, Zn, and Mn top-dressed onto the feed. Heifers on the SSG regimen were fed a diet intended to supply energy to support gains at a rate of 120% of the CG diet for 55 d and then were switched to a diet formulated to produce an ADG at 70% of the rate of the CG diet for 84 d. They then switched back to the 120% diet for the last 30 d before breeding. Total weight gain and overall rate of gain did not differ among dietary treatments. Hereford- and Limousin-sired heifers gained at similar rates, and Piedmontese-sired heifers gained an average of .10 kg/d slower than the other two sire breed groups. During one period, Piedmontese-sired heifers on the CG diet gained .19 kg/d faster ( P < . 01) when supplemented with mineral than when not. During that same period, there was no influence of mineral supplementation on weight gains for Hereford- or Piedmontese-sired heifers on the high SSG diet, but Limousin-sired heifers tended (P = .07) to gain faster (1.00 vs .85 kg/d) when supplemented with Cu, Zn, and Mn than when not. Piedmontese-sired heifers reached puberty at the earliest age (P = .03), followed by Hereford- and then Limousin-sired heifers. There were no treatment effects on milk yield at an average of 70 d of lactation. However, at approximately 120 d of lactation, Piedmontese-sired heifers were producing less milk (P < .05) than Limousin- but not Hereford-sired heifers. Hereford-sired heifers had lower (P < .05) plasma Cu concentrations than Piedmontese-sired heifers. There were no treatment effects on plasma Zn concentrations. Heifers sired by bulls of breeds that differ in potential muscularity differed in growth, reproduction, milk yield, and plasma mineral concentrations, but dietary treatments resulted in little to no differences in these variables.     

Feed intake, weaning weight and net returns comparisons for four breeding systems

Feed intake, weaning weight and direct and maternal contributions to weaning weight were estimated for four breeding systems using data collected between 1979 and 1986 from 773 cow-calf pairs at the Elora Beef Research Centre. Breeding systems included purebred Hereford (HE), small rotational dual purpose (SR) (a four-way rotational crossing system utilizing Tarentaise, Angus, Gelbvieh and Pinzgauer breeds), large rotational beef (LR) (composed of Maine-Anjou, Simmental and Charolais) and Angus-sired large rotational beef (AL) utilizing Angus as the sire breed and LR as the maternal breed. Large rotational dams had the highest feed intakes for both dry (8.9 kg DM/d) and lactation (11.5 kg DM/d) periods. Conversely, HE calves consumed the greatest amounts of creep feed (309 kg DM), followed by AL, SR and LR. The large rotational system had the highest weaning weights (265 kg) and direct (12.3 kg greater than average of observations) and maternal (9.6 kg greater than average of observations) contributions to weaning weight, followed by AL, SR and HE for all three traits. An equation was derived for net returns that included parameters for feed intake and direct and maternal weaning weight. A linear programming model was designed to incorporate this equation as the objective function and determine the breeding system(s) that maximized net returns under various production conditions. In general, LR produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size) included in the model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Tuli,Brahman, Angus,and Polled Hereford Sires on Carcass Traits of Steer Offspring

Steer progeny (n = 122) of tropically adapted breeds [Tuli (TU) and Brahman (BR)] and temperate breeds [Angus (AN) and Hereford (HP)] was evaluated for carcass traits for 3 yr. Multiparous British (Bt) cows were bred to each sire breed. Following weaning in the fall, steers were provided bermudagrass hay and a supplement until rye was available, which they grazed until March. Steers were fed for 100 to 110 d beginning in March. Live weight (LWT); hot carcass weight (HCW); longissimus area (LEA); percentage kidney, pelvic, and heart fat (KPH); actual fat thickness (ACT); adjusted fat thickness (ADJ); marbling score(MARB); maturity score(MAT); quality grade (QG); yield grade (YG); dressing percentage(DP); and LEA per unit of LWT (LEACWT) were collected. Data were analyzed by Proc MIXED using a model that included year, sire breed, and year × sire breed. Sire breed was a significant source of variation for all traits except LEA. The effect of year was significant for all traits, and year × sire breed was significant for only LWT. Least square means for LWT and HCW ranked the breeds similarly; the AN-sired calves (576 kg, 333 kg) and BR-sired calves (574 kg, 334 kg) were heavier than the TU-sired calves (526 kg, 304 kg), and the HP-sired calves had intermediate LWT and HCW (562 kg, 320 kg). The actual and adjusted fat means were larger (P<0.02) for AN-sired calves, HP-sired cavles were intermediate, and the BR- and TU-sired steers were similar with less external fat. The TU-sired calves had the largest LEA relative to weight. The AN- and TU-sired groups had a similar percentage grading Choice (26 and 21%, respectively), and the percentage grading Choice for the other two sire breed groups was 12% for BR and 18% for HP. In conclusion, carcass merit of TU-sired calves provides an acceptable alternative to BR-sired calves for producers desiring a tropically adapted sire breed, but they will likely produce smaller slaughter BW than BR sires if managed similarly.     

Effect of tropically adapted sire breeds on preweaning growth of F1 Angus calves and reproductive performance of their Angus dams

The objective of this study was to determine the effect of tropically adapted sire breeds on preweaning growth performance of F1 calves and on reproductive performance of their Angus dams. Angus (A) cows were bred in two consecutive years (1992 and 1993) by AI using semen from Brahman (B; Bos indicus; n = 10), Senepol (S; Bos taurus; n = 10), and Tuli (T; Sanga; n = 9) bulls. A total of 82 B x A, 85 S x A, and 91 T x A calves were born. The statistical model included the fixed effects of year, sire breed, calf sex, sire breed x calf sex, and cow parity and the random effect of sire within sire breed. Birth weight, weaning weight, 205-d adjusted weaning weight, ADG from birth to weaning, and hip height at weaning were greater (P < .001) for B x A calves than for S x A or T x A calves. Greater differences were detected between sexes for B x A than for S x A and T x A (for all traits sire breed x calf sex, P < .05). Sire breed affected (P < .01) the percentage of unassisted calvings (B x A, 87%; S x A, 98%; and T x A, 100%) and tended (P < .10) to affect the percentage of calves that survived until weaning (B x A, 90%; S x A, 94%; and T x A, 98%). Sire breed of calf did not affect (P > .10) length of gestation, and sire breed did not affect the interval from calving to first observed estrus or pregnancy in Angus dams. These results demonstrate that preweaning growth performance of B x A calves was greater than that of either S x A or T x A calves. However, use of Brahman sires on Angus dams led to calving problems and tended to reduce the percentage of calves that survived until weaning. Thus, heavier weaning weights of B x A calves would be an advantage for cow-calf producers marketing calves, but heavier birth weights and calving difficulty attributed to Brahman sires would be a disadvantage.     

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.     

Interactions in postweaning production of F1 cattle from Hereford, Limousin, or Piedmontese sires

A 2-yr study was conducted to evaluate the interactions of castration, feeding length, and dietary CP on growth and carcass characteristics of male cattle (bulls and steers) that vary in expression of muscular hypertrophy. Crossbred cows were bred by AI to Hereford, Limousin, or Piedmontese bulls, which represented genotypes with normal, moderate, and hypermuscularity, respectively, but with similar mature weights. Male calves (131 in yr 1 and 120 in yr 2) were placed in pens with individual electronic feeding gates. Calves were fed growing diets until they reached 386 kg BW and then were individually switched to finishing diets for 90 or 132 d. Interactions were observed among sire breed, gender, and feeding length on carcass composition. Bulls were more efficient than steers in producing live weight gain. Length of finishing period accounted for a larger source of variation than gender for weight characteristics, whereas gender was the larger source of variation for carcass composition. Concentration or degradability of dietary CP influenced rate of gain from weaning to 386 kg. Interactions resulting from varying management on carcass characteristics among calves of different sire breeds indicate that unique strategies may be beneficial for the production of meat from these breeds.     

Across-breed expected progeny differences: use of within-breed expected progeny differences to adjust breed evaluations for sire sampling and genetic trend.

Data on 2,034 F1 calves sired by Angus, Hereford, Polled Hereford, Charolais, Limousin, Simmental, Gelbvieh, and Tarentaise bulls with Hereford or Angus dams and data on 3,686 three-breed-cross calves with 700 F1 dams of the same breed crosses were used for this study. Traits analyzed were birth, weaning, yearling, and 420-d weights (BWT, WW, YW, and W420, respectively) of F1 calves and WW of three-breed-cross calves. Expected progeny differences from national cattle evaluation programs for sires of F1 calves and cows for BWT, WW, YW, and net maternal ability (milk) were used to assess their value in prediction of crossbred performance. Regressions of actual F1 calf performance on sire EPD were positive for BWT (1.09 +/- .12 kg/kg of BWT EPD), WW (.79 +/- .14 kg/kg of WW EPD), YW (1.44 +/- .16 kg/kg of YW EPD), and W420 (1.66 kg/kg of YW EPD). These regression coefficients were similar to the expected value of 1.0 for BWT and WW but were larger than expected for YW and W420. Regressions of actual three-breed-cross calf WW on milk and WW EPD of their maternal grandsires were .95 +/- .14 and .42 +/- .10 kg/kg, respectively, and differed little from their expectations of 1.0 and .5, respectively. Observed breed of sire means for each trait were adjusted for sire sampling by using EPD regressions to adjust them to the average EPD of all sires of each breed born in 1970.(ABSTRACT TRUNCATED AT 250 WORDS)     

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

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

Performance of crosses among Hereford, Angus and Simmental cattle with different levels of Simmental breeding: V. Calf production, milk production and reproduction of three- to eight-year-old dams

Measures of maternal productivity and reproduction of Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H), 50% Simmental-50% Hereford (1S1H) and 75% Simmental-25% Hereford (3S1H) dams were studied. Half of each dam breed group was bred to Tartentaise and half to Charolais sires to produce 706 calves at weaning from 930 exposures to breeding in a Montana range environment. Data were analyzed according to a model that included the fixed effects of year, dam breed group, dam age, calf sex, calf sire breed, plus appropriate two-way interactions, linear partial regression on calf birth date and random effects of sire within dam breed group (maternal grandsire of the calf) and sire within calf sire breed. Calf sex interacted with calf sire breed for several traits, but interactions were due to changes of magnitude of differences between sexes. There were no significant interactions of dam breed group with other main effects for calf growth traits, except for the interaction with calf sire breed for some calf growth traits. This interaction was due to a change in magnitude; it suggested that larger sire breeds should be matched to larger dam breeds with greater potential for milk production. The only significant interaction for traits that included reproduction of the dam was dam breed group X age of dam. Ranking of dam breed groups depended on age at measurement. Differences among dam breed groups were significant for most traits. Calf weaning weights for HH, AH, 1S3H, 1S1H and 3S1H dams were 211, 223, 227, 237 and 243 kg, respectively; calf weaning weights per cow exposed were 157, 163, 179, 189 and 169 kg; calf weaning weights per unit of dam weight were .40, .41, .43, .44 and .42, respectively. Thus, dam breed groups that weaned the largest calves were not necessarily the most productive under Montana range conditions.     

Genetic and phenotypic relationships of serum leptin concentration with performance, efficiency of gain, and carcass merit of feedlot cattle

Leptin is the hormone product of the obese gene that is synthesized and predominantly expressed by adipocytes. This study estimated the genetic variation in serum leptin concentration and evaluated the genetic and phenotypic relationships of serum leptin concentration with performance, efficiency of gain, and carcass merit. There were 464 steers with records for serum leptin concentration, performance, and efficiency of gain and 381 steers with records for carcass traits. The analyses included a total of 813 steers, including those without phenotypic records. Phenotypic and genetic parameter estimates were obtained using SAS and ASREML, respectively. Serum leptin concentration was moderately heritable (h2 = 0.34 +/- 0.13) and averaged 13.91 (SD = 5.74) ng/mL. Sire breed differences in serum leptin concentration correlated well with breed differences in body composition. Specifically, the serum leptin concentration was 20% greater in Angus-sired steers compared with Charolais-sired steers (P < 0.001). Consequently, ultrasound backfat (27%), carcass 12th-rib fat (31%), ultrasound marbling (14%), and carcass marbling (15%) were less in Charolais- than Angus-sired steers (P < 0.001). Conversely, carcass LM area (P = 0.05) and carcass lean meat yield (P < 0.001) were greater in Charolais- compared with Angus-sired steers. Steers with greater serum leptin concentration also had greater DMI (P < 0.001), greater residual feed intake (P = 0.04), and partial efficiency of growth (P = 0.01), but did not differ in feed conversion ratio (P > 0.10). Serum leptin concentration was correlated phenotypically with ultrasound backfat (r = 0.41; P < 0.001), carcass 12th-rib fat (r = 0.42; P < 0.001), ultrasound marbling (r = 0.25; P < 0.01), carcass marbling (r = 0.28; P < 0.01), ultrasound LM area (r = -0.19; P < 0.01), carcass LM area (r = -0.17; P < 0.05), lean meat yield (r = -0.38; P < 0.001), and yield grade (r = 0.32; P < 0.001). The corresponding genetic correlations were generally greater than the phenotypic correlations and included ultrasound backfat (r = 0.76 +/- 0.19), carcass 12th-rib fat (r = 0.54 +/- 0.23), ultrasound marbling (r = 0.27 +/- 0.22), carcass marbling (r = 0.76 +/- 0.21), ultrasound LM area (r = -0.71 +/- 0.19), carcass LM area (r = -0.75 +/- 0.20), lean meat yield (r = -0.59 +/- 0.22), and yield grade (r = 0.39 +/- 0.26). Serum leptin concentration can be a valuable tool that can be incorporated into appropriate selection programs to favorably improve the carcass merit of cattle.     

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.     

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.     

Preweaning growth of F1 tropically adapted beef cattle breeds x Angus and reproductive performance of their Angus dams in arid rangeland

The objective of this study was to determine the preweaning performance of F1 Brahman (Bos indicus)-, Senepol (Bos taurus)-, and Tuli (Sanga)-Angus calves under semiarid south Texas conditions and to evaluate the reproductive performance of their Angus dams. Four hundred eighty-nine records collected over 4 yr were analyzed. The statistical model for performance traits included the effects of breed of sire, year, sex, age of dam, and breed of sire x year. Year effects were important (P < 0.05) for performance traits but could be explained, at least partially, by differences between years in rainfall patterns. Brahman F1 calves were 13% less (P < 0.05) vigorous at birth, 4.7 kg heavier (P < 0.05) at birth, 13.5 kg heavier (P < 0.05) at weaning, 0.25 units lower (P < 0.05) in body condition score (BCS) at weaning, and 1.75 units greater (P < 0.05) in frame score (scores of 1 to 9) at weaning than Tuli and Senepol F1 calves. Senepol F1 calves were intermediate (P < 0.05) between the Brahman and Tuli F1 calves for birth and weaning weight but had 11% more (P < 0.05) vigor at birth than the other two crossbreds. Tuli and Senepol F1 were similar (P > 0.05) in BCS and frame size at weaning. Males were 3.3 kg heavier (P = 0.12) at birth than females, especially for the F1 Brahman males that were 4.5 kg heavier (P < 0.05) than their counterparts. Brahman F1 weaned 19.9 kg heavier (P < 0.05) than the average of the other two F1 in the year of the greatest rainfall (1994), whereas the average advantage in other years was 11.4 kg. This difference gave rise to a breed of sire x year interaction (P < 0.003). Brahman F1 were heavier at every measurement and appeared to be later-maturing and more able to excel under good forage conditions than the other two F1 breed types; Senepol and Tuli F1 were similar (P > 0.05) in these respects but appeared to be more competitive in relative growth rate to the Brahman F1 calves in years of greater nutritional stress. Angus females were observed to have a relatively low reproductive rate and high apparent fetal loss at the first (27.5%) and second (19.2%) compared with the third or later pregnancy (11.2%). Angus females that gave birth to Brahman F1 calves had 20.1% lower (P < 0.05) pregnancy rates in the succeeding year than those that had given birth to the other two breeds.     

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.     

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)