Performance of crosses among Hereford, Angus, and Simmental cattle with different levels of Simmental breeding: VI. Maternal heterosis of 3- to 8-year-old dams and the dominance model.

Data from Hereford, 25% Simmental-75% Hereford, 50% Simmental-50% Hereford, and 75% Simmental-25% Hereford dams were used to estimate maternal heterosis and level of agreement with the dominance model. Cows were located at the Northern Agricultural Research Center near Havre, MT and were managed consistent with practices for western range environments. Sample halves of dam breed groups were bred to Charolais and Tarentaise sires to produce calves at 3 to 8 yr of age. There were 766 exposures to breeding that resulted in 581 calves. Breed group means for most traits supported the dominance model. Maternal heterosis was estimated by regression techniques for 22 cow and calf traits. Maternal heterosis was not significant for day of conception, number of services, gestation length, or calving difficulty. Estimates of maternal heterosis for calf growth traits ranged from .7% for weaning height to 5.2% for weaning weight and 7.5% for weaning condition score. Calf weight per unit of cow weight at weaning showed significant maternal heterosis (7.1%). Higher levels of maternal heterosis were exhibited for milk production (8.2 to 11.1%) and the negative, but nonsignificant, estimate of maternal heterosis for early minus late milk production suggested more persistent lactation for crossbred cows. Maternal heterosis was 11.5% for proportion of dams that calved and 10.4% for proportion of dams that weaned calves. Calf weaning weight per cow exposed to breeding, a characteristic combining calf growth and dam reproduction, exhibited 17.9% maternal heterosis.     

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.     

Performance of crosses among Hereford, Angus and Simmental cattle with different levels of Simmental breeding. III. Heifer postweaning growth and early reproductive traits

Postweaning growth and early reproductive traits in heifers whose potential for milk production differed were studied during the years 1976 through 1979. Data were collected on 230 heifers raised by greater than or equal to 3-yr-old Hereford dams. Heifers were comprised of the following breed groups: Hereford (HH), Angus-Hereford (AH), 25% Simmental-75% Hereford (1S3H) and Simmental-Hereford (SH). Postweaning growth rate during a 140-d period was greatest for SH heifers (.75 kg/d), intermediate for AH and 1S3H groups (.70 and .68 kg/d, respectively) and slowest for HH heifers (.64 kg/d). At 1 yr of age, SH heifers were heavier, taller and had larger pelvic areas than all other groups (P less than .01). Least-squares means for yearling weight, hip height and pelvic area for HH, AH, 1S3H and SH heifers were 283, 303, 298 and 317 kg; 111, 112, 114 and 118 cm, and 132, 136, 139 and 148 cm2, respectively. Ninety-one percent of the heifers reached puberty by the end of the breeding period. Crossbred heifers reached puberty at younger ages and had higher pregnancy rates than HH heifers (P less than .01). Least-squares means for pubertal age, weight and height for HH, AH, 1S3H and SH breed groups were, respectively, 407, 371, 382 and 368 d; 300, 302, 305 and 313 kg, and 115, 114, 117 and 119 cm. Percentage of heifers reaching puberty by 14 mo of age was 64, 99, 85 and 94 for HH, AH, 1S3H and SH, respectively. Respective pregnancy rates were 59, 90, 77 and 86%, but were not significantly different among breed groups when only heifers reaching puberty by the end of the breeding period were studied. No differences among breed groups were found for date of pregnancy.     

Performance of Hereford and two-breed rotational crosses of Hereford with Angus and Simmental cattle: I. Calf production through weaning

Cow size, reproductive traits and calf performance through weaning were evaluated in a range environment for Simmental (S) x Hereford (H) and Angus (A) x H crosses in two-breed rotations and straightbred H. Data were grouped into seven dam breed categories: straightbred Hereford (H), crossbred F1 S x H cows (SH), S x H cows of low percentage H (SHS), S x H cows of high percentage H (HSH), F1 A x H cows (AH), A x H cows of low percentage H (AHA) and A x H cows of high percentage H (HAH). Straightbred H, SH, AH, SHS and AHA cows were mated to H bulls, HSH cows were mated to S bulls and HAH cows were mated to A bulls. Cows in the SHS and AHA groups ranged from 1/4 to 3/8 H and their calves from 5/8 to 11/16 H. Cows within the HSH and HAH groups ranged from 5/8 to 3/4 H and their calves from 5/16 to 3/8 H. Cow age ranged from 3 to 10 yr. Simmental-cross cows were heavier and taller and produced heavier calves at birth and weaning than A-cross. Pregnancy rate, calf birth date and percentage of difficult births did not vary significantly among dam breed groups. Within the A x H and S x H rotations, dam breed group rankings for calf birth weight were inverse to rankings for proportion of H in the breed makeup of the calf.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heterosis retained in advanced generations of crosses among Angus and Hereford cattle

Data from 1,909 purebred, F1, backcross and F2 and F3 inter se combinations of Angus and Hereford were used to estimate average individual, maternal and grandmaternal genetic effects, individual and maternal heterosis, dominance and epistatic genetic effects. Models for evaluating heterosis and epistatic or recombination effects were discussed. Average individual effects indicate that Angus, compared with Hereford, had calves that were born earlier, had lighter birth weights, lower pre- and postweaning gains and lower pregnancy rates. Angus also produced lighter weight carcasses with more fat cover and marbling. Maternal effects of Angus were in the direction of reduced birth weight, greater calving ease, higher preweaning but lower postweaning growth rate and increased fatness when contrasted with Hereford. There was a tendency for opposite direction of maternal and grandmaternal effects for traits influenced by preweaning maternal environment. When additive X additive effects were ignored, total heterosis was significant for earlier day born, heavier birth weight, preweaning and postweaning gain, and heavier and fatter carcasses. Heterosis retained in F3 inter se vs F1 generation crosses indicated that net epistatic effects were relatively negligible for date of calving, birth weight, weaning gain and fat cover. There was a greater reduction of heterosis effects than expected from dominance alone for survival, pregnancy and marbling score. Loss of heterosis in F3 was less than expected for postweaning gain, carcass weight and rib eye area. Except for survival, pregnancy and marbling, these deviations from dominance expectations, or lack of them, are favorable for F3 composite populations.     

Growth patterns of Angus, Hereford and shorthorn cattle. II. Relationship of growth patterns of dams with progeny performance

Relationships between estimated growth curve parameters of dams and performance traits of their progeny were studied in Angus, Hereford and Shorthorn herds, each divided into four inbred and two noninbred lines. Growth curve parameters were calculated from the growth function Yt=A(1-Be-Kt), where Yt was weight at age t, A was estimated mature weight, B was an estimate related to early life weight changes and provided for a Y-intercept term and K was estimated general rate of maturing. Least-squares analyses of progeny variables were calculated separately for each breed and sex. Line differences did not influence any of the progeny variables except weaning type score of Shorthorn males (P less than .01). Birth year exerted a curvilinear effect on birth weights of Angus female progeny (P less than .01), a linear influence on 205-d weights of Shorthorn male progeny (P less than .05) and a curvilinear effect on weaning type scores of Angus and Shorthorn male progeny (P less than .01). Regression coefficients on weaning age indicated that calves born earlier in the calving season had lighter birth weights and that older calves at weaning received higher type scores. Inbreeding of the progeny negatively influenced (P less than .05) birth weights of Angus male and Hereford female progeny. Hereford male and Shorthorn female 205-d weights were negatively affected (P less than .05) by inbreeding, while weaning type scores of Shorthorn female progeny were negatively influenced (P less than .001) by inbreeding. Regression coefficients of all progeny variables on inbreeding in all analyses indicated negative trends.(ABSTRACT TRUNCATED AT 250 WORDS)     

Testicular development, epididymal sperm reserves and seminal quality in two-year-old Hereford and Angus bulls: effects of two levels of dietary energy

The effect of high (HED) and medium energy diets (MED), fed to Hereford (H) and Angus (A) bulls from 6 through 24 mo of age, on scrotal circumference (SC), paired testes weight (PTW), epididymal sperm reserves (ESR) and seminal traits were examined. Over 3 yr, 120 bulls were involved. Angus exceeded H for both SC and PTW. Hereford bulls in yr 2 had smaller SC than in yr 1 or 3 but the response for A was consistent. Year affected PTW. In yr 2 Hereford bulls fed HED had 75% fewer ESR than MED-H bulls (9.3 vs 37.2 X 10(9]. Comparably treated A bulls had similar ESR numbers (29.2 vs 33.4 X 10(9]. In yr 3, epididymal sperm reserves of HED-H were depressed by 35% compared with MED-H (23.1 vs 35.7 X 10(9], whereas HED-A had 14% fewer ESR than did MED-A bulls (28.6 vs 33.1 X 10(9]. It was not obvious why H bulls were more susceptible to the effects of HED. Seminal quality of HED bulls was inferior to that of MED bulls, particularly with respect to progressive motility and the incidence of sperm in which a crater defect of the head was present at 2 yr of age. In yr 2 all seminal traits were severely depressed in 2-yr-old HED-H. Feeding HED to young H and A bulls reduced their reproductive potential.     

Reproductive rates, birth weight, calving ease and 24-h calf survival in a four-breed diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle

Calving and weaning rates, birth weight, calving ease, and 24-h calf survival were evaluated in a four-breed diallel of Simmental (S), Limousin (L), Polled Hereford (H) and Brahman (B) beef cattle in five calf crops. Limousin dams tended to have the highest calving and weaning rates because they were able to have heavier calves with less calving difficulty and higher survival rates. Brahman-sired calves were the heaviest at birth (P less than .05) and B dams produced the lightest calves (P less than .001). Lower birth weights tended to be the limiting factor on survival of these calves. A linear comparison among means to evaluate purebred, additive, maternal and specific combining ability effects showed most of the reduction in birth weight from B dams was due to maternal effects. Breed of dam accounted for a higher proportion of variation in calving ease than did sire breed. Simmental sires had significantly heavier calves at birth and S and H dams tended to have more calving difficulty and lower survival rates. Heterosis for these traits was generally not significant. Correlations were generally positive and significant for birth weight and calving ease, but were more variable for birth weight and survival. Linear regressions of calving ease on birth weight both within years and within dam-breed-year subclasses were very similar in that the association of these two traits was reduced as dam age increased.     

Economic evaluation of heterosis and culling policies for lifetime productivity in Hereford, Angus, shorthorn, and crossbred cows.

Experimental lifetime performance data obtained from 156 straightbred Hereford, Angus, and Shorthorn and 172 first-cross heifers were used to estimate heterosis for economic efficiency in a 100-cow herd at age equilibrium under three culling policies and at terminal ages from 6 to 12 yr. All nonpregnant heifers and cows greater than 9 yr of age were culled. The culling policy for removal of nonpregnant cows from second parity through 9 yr of age were 1) no culling, 2) after two consecutive years (actual), and 3) all (imposed). Efficiency was calculated as input cost per unit of output value. A 10-yr average was used for costs of replacement heifers, cow units, and the ratio of calf:cull cow prices (PR), plus higher and lower PR. Input included costs for both cow units and purchased replacements. Output value included both weaned calves and cull cows. Optimum terminal age was mainly a function of PR: 9 yr for average and high PR, but 6 through 9 yr when PR was low, regardless of culling policy or breed groups. Efficiency differences among culling policies were small for high or average PR, but more culling for infertility was beneficial when PR was low. Estimated reductions in unit costs of output value under any culling policy or terminal age were approximately 6% from crossbred cows plus another 6% from crossbred calves, or a total of 12% from specific three-breed crossing of these British breeds. Cost reductions would be somewhat less for rotation crossbreeding but greater for mating smaller crossbred cows with sires of superior growth-carcass breeds.     

Evaluation of performance characteristics in a diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. II. Carcass traits

Evaluations of steer and heifer progeny from a diallel mating design of Simmental, Limousin, Polled Hereford and Brahman beef cattle over 5 yr are presented. Traits evaluated included final weight, hot carcass weight, ribeye area, 12th rib fat thickness, marbling score, yield grade, dressing percentage and percentage of kidney, pelvic and heart fat. Progeny of Simmental sires were heavier at slaughter than those with Brahman sires (P less than .05), but no differences were found for carcass weight. Dressing percentage was higher for Limousin crosses compared with progeny of other sire breeds (P less than .05). Similar results were found for dam breeds, except that progeny of Limousin dams had heavier carcasses with a higher dressing percentage (P less than .05) than Brahman crosses. Crosses of Limousin and Simmental had larger ribeye areas (P less than .05) compared with calves of the other breeds. Progeny of Polled Hereford dams had higher marbling scores and were fatter than progeny of dams of other breeds (P less than .05). Heterosis estimates were significant for all Brahman crosses for final weight, carcass weight and ribeye area, but these contrasts were negligible for other traits. Estimates of general combining ability were positive and significant for Simmental for final weight, carcass weight, ribeye area and marbling score and were significant and negative for Limousin for final weight, fat thickness and yield grade. Maternal values were generally small.     

Mineral concentrations of plasma and liver after injection with a trace mineral complex differ among Angus and Simmental cattle

To examine the effects of cattle breed on the clearance rate of an injectable mineral product, 10 Angus and 10 Simmental steers were blocked by breed and initial BW (332 ± 33 kg) and injected with either Multimin 90 (MM) or sterilized saline (CON) at a dose of 1 mL/45 kg BW. Multimin 90 contains 15 mg Cu/mL (as Cu disodium EDTA), 60 mg Zn/mL (as Zn disodium EDTA), 10 mg Mn/mL (as Mn disodium EDTA), and 5 mg Se/mL (as sodium selenite). Steers received a corn-silage-based diet, and inorganic sources of Cu, Zn, Mn, and Se were supplemented at NRC recommended amounts. Jugular blood was collected immediately before injection and at 8 and 10 h post-injection and on days 1, 8, and 15 post-injection. Liver biopsies were collected 3 d before injection and on days 1, 8, and 15 post-injection. Liver and plasma mineral concentration and glutathione peroxidase (GSH-Px) activity data were analyzed as repeated measures. Plasma concentrations of Zn, Mn, and Se were greater (P = 0.01) and Cu tended to be greater (P = 0.12) post-injection in MM steers compared with the CON steers. Regardless of treatment, Simmental cattle had lower plasma concentrations of Cu, Zn, and Se (P ≤ 0.05) when compared with Angus cattle. Erythrocyte GSH-Px activity was greater (P = 0.01) in MM steers compared with CON steers. Liver concentrations of Cu, Zn, and Se were greater (P = 0.05) in MM steers compared with CON steers post-injection. Liver Mn concentrations tended to be greater (P = 0.06) in MM steers compared with CON steers in the days post-injection. Interestingly, Simmental cattle exhibited greater (P = 0.01) liver Mn concentrations in the days after injection compared with Angus cattle (7.0 and 6.0 mg Mn/kg for Simmental and Angus cattle, respectively), regardless of treatment. It is unclear if this breed difference is biologically relevant; however, these data may suggest that differences in liver excretion of Mn exist between the two breeds. Overall, use of an injectable trace mineral increased liver concentrations of Cu and Se through the 15-d sampling period, suggesting that this injectable mineral is an adequate way to improve Cu and Se status of cattle through at least 15 d.     

Evaluation of performance characteristics in a diallel among Simmental, Limousin, Polled Hereford and Brahman beef cattle. I. Growth, hip height and pelvic size

Progeny of a diallel among Simmental, Limousin, Polled Hereford and Brahman breeds of cattle were evaluated over 5 yr for preweaning and postweaning growth, hip height and pelvic size. Calves from Brahman and Simmental dams had the highest preweaning gains and weaning weights, and those from Polled Hereford dams had the lowest (P less than .05). Differences in the availability of milk and postpartum compensatory gains in progeny of Brahman dams could have contributed to these results. However, calves from Simmental, Limousin and Polled Hereford dams had significantly greater feedlot daily gains than those from Brahman dams. Yearling hip height and pelvic area were lower for progeny of Polled Hereford dams, whereas calves from Simmental, Limousin and Brahman dams were not different for these traits. A series of linear comparisons among these four breeds using least-squares means to estimate general and specific combining ability and maternal effects found significant, negative maternal effects for Polled Hereford for preweaning gain and weaning weight. A positive maternal effect (P less than .05) for Limousin was found for feedlot gain. General combining ability and maternal estimates were significant and variable in most comparisons for yearling hip height and pelvic area. Heterosis estimates were positive and significant in all crosses with Brahman for preweaning gain, weaning weight, yearling weight, hip height and pelvic area. Significant, positive heterosis was also found in Polled Hereford crosses with Limousin and Simmental for preweaning gain, weaning weight and yearling weight.     

Testicular development, daily sperm production and epididymal sperm reserves in 15-mo-old Angus and Hereford bulls: effects of bull strain plus dietary energy

Bull calves (n = 143) were obtained from two strains of Angus and two strains of Hereford cattle for which replacements were selected on the basis of superior feedlot growth performance on either high- or medium-energy diets. From weaning to slaughter at 15 mo of age, bulls were fed either the high-energy (80% grain + 20% forage) or medium-energy diet (100% forage) corresponding to their strain. Bulls in high-energy diet groups had a greater (P less than .05) scrotal circumference at 12 mo, but not 15 mo of age, than bulls in medium-energy diet groups. Compared with Hereford bulls, Angus had greater (P less than .01) scrotal circumference (36.1 vs 33.9 cm) and greater (P less than .05) paired testes weight (570 vs 464 g) at 15 mo of age. Daily sperm production per gram testicular parenchyma (DSP/g) was affected by strain-diet (P less than .01) but not by breed. Bulls in medium-energy diet groups had 12% greater DSP/g than did high-energy diet bulls (17.4 X 10(6) vs 15.5 X 10(6)). Daily sperm production (DSP) was 9% and 30% greater (P less than .01) for medium-energy diet bulls in 1980 (8.2 X 10(9) vs 7.5 X 10(9)) and 1981 (8.0 X 10(9) vs 6.2 X 10(9)), respectively, compared with high-energy diet bulls. The effect (P less than .01) of breed on DSP was attributed to breed differences in paired testes weight.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth patterns of Angus, Hereford and shorthorn cattle. I. Comparison of inbred and noninbred lines, changes in patterns over time and effects of level of inbreeding and reproductive performance

Mature weight (A) and rate of maturing (K) were estimated for 283 Angus, 140 Hereford and 280 Shorthorn cows utilizing the asymptotic regression equation Yt=A(1-Be-Kt). The Yt was weight of the individual at age t; and B was an estimate related to early life weight changes and provided for a Y-intercept (A-B). Each breed consisted of four inbred and two noninbred lines. Regression of estimated growth curve parameters on levels of inbreeding of the individuals and of their dams and effects of early reproductive performance (EREPRO) were studied as sources of variation in addition to line differences and trends in line values over years. Considered jointly with inbreeding of the dam and with EREPRO, inbreeding of the individual was negatively related (P less than .01) to estimates of A in the three breeds and unrelated (P greater than .10) to estimates of K. Each 1% increase in inbreeding of the individual was associated with about 2 kg decrease in estimated mature weight. An increase in inbreeding of the dam of an individual was negatively related to estimates of K in Angus (P less than .01) and Shorthorns (P less than .05). Inbreeding of dams was positively related to estimates of A in the three breeds, but only in Shorthorns could the relationship be declared significant. Estimates of A were about 46 kg heavier and estimates of K about .010 less for each year an individual failed to produce a calf during her first three opportunities. In general, A values declined in all three breeds during the study. Significant changes were observed in all Hereford analyses and after inbreeding was included in the Angus analysis, while inclusion of inbreeding in the Shorthorn analysis caused the change to become unimportant. The K values increased in all three breeds during the study; however, the change could be declared significant only in Herefords.     

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.     

Twinning in cattle: III. Effects of twinning on dystocia, reproductive traits, calf survival, calf growth and cow productivity

An evaluation of natural twinning in beef cattle revealed that cows birthing twins had shorter (P less than .01) gestation lengths, more (P less than .01) retained placentas, more (P less than .01) dystocia, more (P less than .01) days to estrus, lower (P less than .01) conception rates and more (P less than .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of calves reared (1 vs 2) in cows birthing twins. Survival at birth was greater (P less than .01) for single- than for twin-born calves, but twins and singles did not differ (P greater than .05) in postnatal survival. When dystocia was experienced, calf survival at birth was 95% vs 73% for singles vs twins compared with 99% vs 92% when no dystocia was experienced. Calves born twins were lighter (P less than .01) at birth, 100 d and 200 d, but twins and singles did not differ in postweaning gains. Total calf weights at 100 d per cow calving were 12% greater (P less than .01) in cows birthing twins vs singles when twin calves reared by foster dams were excluded. The potential increase in cow productivity for total calf weight at 100 d is 40% if calf survival rates of twins with dystocia relative to survival rates of twins without dystocia were comparable to survival rates of singles with and without dystocia, and if cows birthing twins were fed and managed to obtain conception rates equal to those of cows birthing singles. Identification of cows gestating twins to provide for their higher prepartum nutritive requirements and calving assistance at parturition is necessary to make twinning in cattle an economically viable technology.     

Effects of different dietary energy and protein levels and sex on growth performance,carcass characteristics and meat quality of F1 Angus x Chinese Xiangxi yellow cattle

Background：The experiment evaluated the effect of nutrition levels and sex on the growth performance,carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle.Methods：During the background period of 184 d,23 steers and 24 heifers were fed the same ration,then put into a2×2×2 factorial arrangement under two levels of- dietary energy（TON：70/80%DM）,protein（CP：11.9/14.3%DM）and sex（S：male/female） during the finishing phase of 146 d.The treatments were-（1） high energy/low protein（HELP）,（2） high energy/high protein（HEHP）,（3） low energy/low protein（LELP） and（4） low energy/high protein（LEHP）.Each treatment used 6 steers and 6 heifers,except for HELP- 5 steers and 6 heifers.Results：Growth rate and final carcass weight were unaffected by dietary energy and protein levels or by sex.Compared with the LE diet group,the HE group had significantly lower dry matter intake（DMI,6.76 vs.7.48 kg DM/d）,greater chest girth increments（46.1 vs.36.8 cm）,higher carcass fat（19.9 vs.16.3%） and intramuscular fat content（29.9 vs.22.8%DM）.The HE group also had improved yields of top and medium top grade commercial meat cuts（39.9 vs.36.5%）.The dressing percentage was higher for the HP group than the LP group（53.4 vs.54.9%）.Steers had a greater length increment（9.0 vs.8.3 cm）,but lower carcass fat content（16.8 vs.19.4%） than heifers.The meat quality traits（shear force value,drip loss,cooking loss and water holding capacity） were not affected by treatments or sex,averaging 3.14 kg,2.5,31.5 and 52.9%,respectively.The nutritive profiles（both fatty and amino acid composition） were not influenced by the energy or protein levels or by sex.Conclusions：The dietary energy and protein levels and sex significantly influenced the carcass characteristics and chemical composition of meat but not thegrowth performance,meat quality traits and nutritive profiles.