Predicting dystocia in heifers

The relationship of heifer size, calf size and sire on dystocia was studied in approximately one thousand Angus, Hereford X Angus and Charolais heifers bred to Angus, Hereford and Charolais bulls. Heifers were weighed and pelvic measurements taken 35 days post breeding, at midgestation, and on a random group of 135 heifers two weeks prior to calving. Dystocia score, calf birth weight, calf body length, calf hip width and calf sex were recorded at calving.Correlation coefficients for calf traits indicate that birth weight and birth weight to body measurement ratios were the most highly correlated variables with dystocia score. For traits of the dam, pelvic area was the most highly correlated variable to dystocia score, while dam weight had a low and nonsignificant correlation.Sires experiencing a higher than average incidence of dystocia had calves that were larger for all measures of body size. Individual sire differences for dystocia indicate a large number of calves and an accurate randomization of heifers bred to each bull is necessary to make precise judgements as to a bull's potential for siring easy-calving offspring.Calf size measurements were positively correlated with heifer weight and pelvic area; however, correlations tended to be low. Breed of calf, sire, heifer weight I and II and pelvic area I, II and III accounted for only 23.6% of the variation in calf birth weight.Charolais calves were larger (P<.05) and had more dystocia (P<.05) than Hereford or Angus sired calves. Hereford sired crossbred calves were larger (P<.05) and had more dystocia than Angus crossbred or straightbred calves. Angus crossbred calves were larger (P<.05) but had no more dystocia than Angus straightbred calves.Heritability estimates for calf body length (0.35) and calf hip width (0.42) indicate calf skeletal measurements were more heritable than calf birth weight (0.28).Pelvic area measurements were correlated (P<.01) with heifer weight; however, heifer weight I and II accounted for only 37% and 30% of the variability in pelvic area I and II, respectively. Average pelvic area was largest in Charolais heifers, followed by Crossbred and Angus heifers. Pelvic area growth was .275 cm²/day in Angus, .254 cm²/day in Crossbred, and .250 cm²/day in Charolais heifers.Dystocia score was most highly related to calf size and pelvic area I. Pooled over all breeds, a regression analysis showed 37% of the variability in dystocia score being accounted for by the ratio of calf birth weight to calf body length and pelvic erea I. Very little increase in the R² value occurred by the addition of the other independent variables.Histogram analyses demonstrates that a constant level of dystocia can be maintained only if pelvic area increases in proportion to calf size. However, regardless of the size of calf, heifers that had very small pelvic openings had a high rate of dystocia, just as heifers having very large calves experienced high rates of dystocia even when they had large pelves.     

内蒙古白绒山羊若干数量性状遗传参数的研究

本研究应用女母回归法、公畜内女母回归法、半同胞相关法和单元内半同胞相关法对内蒙古阿尔巴斯白绒山羊的产绒量、绒厚、毛长、体重、绒伸直长度和细度等六个性状的遗传参数进行了估测。结果表明：（1）绒量遗传力介于0.26～0.45之间;绒厚遗传力介于0.33～0.56之间;毛长遗传力介于0.23～0.32之间;体重的遗传力介于0.1 6～0.36之间;绒伸直长度遗传力为0.24;绒细度的遗传力为0.14。（2）产绒量与绒厚、绒厚与毛长、长度与绒厚、长度与毛长的遗传相关分别介于0.33～0.79、0.51～0.69 、0.38～0.60、0.74～0.90之间,存在较强的正向遗传相关;绒量与毛长、绒量与体重、绒厚与体重、细度与绒厚、细度与绒量、细度与体重的遗传相关分别为0.11～0.38、0 .06～0.17、0.15～0.36、0.02～0.11、0.24～0.35、0.13～0.32之间,存在较弱的正向遗传相关;毛长与体重、长度与绒量、长度与体重、长度与细度、细度与毛长之间的遗传相关介于-0.14～-0.28、-0.09～-0.20、-0.18～-0.23、-0.27～-0.31、-0 .17～-0.28之间,存在中等偏弱的负向遗传相关。（3）绒量、绒厚、毛长、体重的重复率分别为0.42、0.27、0.59、0.18。     

Phenotypic relationships of scrotal circumference to frame size and body weight in performance-tested bulls

The objective of this study was to determine if frame size (height) is related to scrotal circumference. A total of 695 bulls (425 Angus, 65 Hereford, 70 Charolais, 135 Simmentals) were tested for postweaning gain in five stations over a period of 1 to 3 years. Variables examined included hip height, weight and scrotal circumference at beginning and completion of a 140-d feeding period. Correlations among these traits, adjusted for age (7 to 10 months at entry), year, station and management were estimated for each breed. Both height and weight were correlated positively with scrotal circumference at the start and the end of the test period in all four breeds. When height and scrotal circumference were adjusted for weight, correlations were negligible, with the exception of end-of-test values for Charolais bulls (-0.26). Negative correlations were obtained between the scrotal circumference at the start of the test and the change in height during the test after adjustment for weight in Angus bulls (-0.18) and in Charolais bulls (-0.15). These small negative phenotypic relationships indicate that a bull's fertility is not seriously reduced by large frame size at the completion of a feedlot performance test. For maximum fertility in bulls, scrotal circumference needs to be evaluated independently of frame size.     

(Co)Variance components and genetic parameter estimates for growth traits in Moghani sheep

Genetic parameters were estimated for birth weight (BW), weaning weight (WW), yearling weight (YW), average daily gain from birth to weaning (ADG1) and average daily gain from weaning to yearling (ADG2) in Moghani sheep. Maximum number of data was 4237 at birth, but only 1389 records at yearling were investigated. The data was collected from 1995 to 2007 at the Breeding Station of Moghani sheep in Jafarabad, Moghan, Iran. (Co)Variance components and genetic parameters were estimated with different models which including direct effects, with and without maternal additive genetic effects as well as maternal permanent environmental effects using restricted maximum likelihood (REML) method. The most appropriate model for each trait was determined based on likelihood ratio tests and Akaike's Information Criterion (AIC). Maternal effects were important only for pre-weaning traits. Direct heritability estimates for BW, ADG1, WW, ADG2 and YW were 0.07, 0.08, 0.09, 0.09 and 0.17, respectively. Fractions of variance due to maternal permanent environmental effects on phenotypic variance were 0.08 for ADG1. Maternal heritability estimates for BW and WW were 0.18 and 0.06, respectively. Multivariate analysis was performed using the most appropriate models obtained in univariate analysis. Direct genetic correlations among studied traits were positive and ranged from 0.37 for BW–ADG2 to 0.85 for ADG1–YW. Maternal genetic correlation estimate between BW and WW was 0.33. Phenotypic and environmental correlation estimates were generally lower than those of genetic correlation. Low direct heritability estimates imply that mass selection for these traits results in slow genetic gain.     

Joint analysis of beef growth and carcass quality traits through calculation of co-variance components and correlations

A joint growth-carcass model using random regression was used to estimate the (co)variance components of beef cattle body weights and carcass quality traits and correlations between them. During a four-year period (1994-1997) of the Australian "southern crossbreeding project", mature Hereford cows (N = 581) were mated to 97 sires of Jersey, Wagyu, Angus, Hereford, South Devon, Limousin, and Belgian Blue breeds, resulting in 1141 calves. Data included 13 (for steers) and 8 (for heifers) body weight measurements approximately every 50 days from birth until slaughter and four carcass quality traits: hot standard carcass weight, rump fat depth, rib eye muscle area, and intramuscular fat content. The mixed model included fixed effects of sex, sire breed, age (linear, quadratic and cubic), and their interactions between sex and sire breed with age. Random effects were sire, dam, management (birth location, year, post-weaning groups), and permanent environmental effects, and their interactions with linear, quadratic and cubic growth, when possible. Phenotypic, sire and dam correlations between body weights and hot standard carcass weight and rib eye muscle area were positive and moderate to high from birth to feedlot period. Management variation accounted for the largest proportion of total variation in both growth and carcass traits. Management correlations between carcass traits were high, except between rump fat depth and intramuscular fat (r = 0.26). Management correlations between body weight and carcass traits during the pre-weaning period were positive except for intramuscular fat. The correlations were low from birth to weaning, then increased dramatically and were high during the feedlot period.     

Multiple linear and nonlinear regression analyses of factors causing calving difficulty

Calving difficulty (CD) was analyzed as the dependent variable from observations on 592 first-calf, 2-year-old heifers that were either Angus X Hereford (AH), Charolais X AH or Simmental X AH. Independent variables were birth weight (BW), pelvic area (PA), BW.(33), PA.(5), cow weight (CW), cow condition score (CS) and sex of calf (S). CD was analyzed as score (1 = no difficulty through 4 = extreme difficulty) CD-I, % CD (1 vs 2 + 3 + 4 , CD-II) or % high CD (1 + 2 vs 3 + 4 , CD-III). R(2) values from CD-II and CD-III multiple correlation (R) analyses were consistently lower (.10 to .13) than from the CD-I analysis. When only BW and PA were included in the model, R(2) values for CD-I were .36, .39 and .39 for the linear, quadratic and cubic analyses, respectively. When BW, PA, CW, CS and S were included in the model, the R(2) values for CD-I were .40 and .42 for the linear and quadratic analyses (cubic effects were not tested). In the linear analysis with BW.(33) and PA.(5), the R(2) for CD-I was .36. In all analyses, the order of importance of the factors studied was BW and PA, with a much lower contribution from CW and S. CS did not account for a significant increase in R(2) in any analysis. CD remained below 50% whenever the PA BW ratio exceeded 8.4. This ratio is a convenient practical method to relate PA and BW to CD. Conclusions are that the linear effects of BW and PA account for the majority of the identified variation in CD (R(2)) and that small increases in R(2) can be obtained by adding CW, CS and S to the model and/or by expanding the model to include quadratic effects.     

Genetic and phenotypic parameter estimates for scrotal circumference and semen traits in young beef bulls

Estimated in this study were heritabilities and genetic and phenotypic correlations involving scrotal circumference (SC), percent live sperm, sperm number, sperm concentration, sperm motility, and an overall measure of a bull's potential breeding efficiency. Potential breeding efficiency is a composite trait based on a consideration of sperm concentration, sperm motility, sperm morphology and scrotal circumference. Data used were from three sources. Records on 863 Angus, 753 Polled Hereford, and 302 Simmental bulls were made available through the Missouri Performance-Tested Bull Sale and records on 1169 Polled Hereford bulls came from the American Polled Hereford Association. Information from these first two data sets were used to estimate heritability of scrotal circumference. The third data set was provided by Nichols Farms of Bridgewater, Iowa, and included information from the records of 465 yearling Polled Hereford and 264 yearling Simmental bulls. This latter data set was used to estimate all of the above mentioned parameters. Each data set was kept separately for the purpose of statistical analysis. Parameters were estimated using components from paternal half-sib analysis of variance and covariance. Pooled estimates of heritability for SC, sperm concentration, sperm motility, percent live sperm, sperm number and potential breeding efficiency were 0.51 +/- 0.09, 0.20 +/- 0.13, 0.11 +/- 0.12, 0.00, 0.19 +/- 0.14 and 0.13 +/- 0.12, respectively. Phenotypic correlations involving the six traits were very consistent for the two breeds. Combined across breeds their values ranged from 0.47 for SC and percent live sperm to 0.96 for sperm concentration and potential breeding efficiency. Corresponding genetic correlations were generally positive and high and ranged from 0.65 for SC and sperm motility to 1.14 for sperm number and potential breeding efficiency.     

Genetic parameter estimates for pre-weaning performance and reproduction traits in Markhoz goats

Genetic parameters for growth, mortality and reproductive performances of Markhoz goats were estimated from data collected during 1993–2010 at Markhoz goat Performance Testing Station in Sanandaj, Iran. For kid performance traits 3763 records were available for birth weight (BW), 2931 for weaning weight (WW), average daily gain (ADG) and Kleiber ratio (KR) (approximated as ADW/WW^0.75) and 3032 for pre-weaning mortality (PWM). For doe reproductive performance traits there were 2920 records available for litter size at birth (LSB), litter size at weaning (LSW), total litter weight at birth (TLWB) and litter mean weight per kid born (LMWKB), and 2182 for total litter weight at weaned (TLWW) and litter mean weight per kid weaned (LMWKW). Genetic parameters were estimated with univariate and bivariate models using restricted maximum likelihood (REML) procedures. Random effects were explored by fitting additive direct genetic effects, maternal additive genetic effects, maternal permanent environmental effects, the covariance between direct and maternal genetic effects, and common litter effects in different models for pre-weaning traits of kids. Also, in addition to an animal model, sire and threshold models, using a logit link function, were used for analyses of PWM. Models for LSB, LSW, TLWB, TLWW, LMWKB, and LMWKW included direct additive genetic effects, permanent environmental effects due to the animal as well as service sire effects. Estimated direct heritabilities were moderate for pre-weaning traits (0.22 for BW, 0.16 for WW, 0.21 for ADG, and 0.27 for KR and 0.29 for PWM), and low for reproduction traits (0.01 for LSB, 0.01 for LSW, 0.02 for TLWB, 0.03 for TLWW, 0.07 for LMWKB, and 0.06 for LMWKW). The estimates for the maternal additive genetic variance ratios were lower than direct heritability for BW (0.07) and KR (0.04). The estimate for the maternal permanent environmental variance ratios (c²) varied from 0.01 for KR to 0.07 for WW and ADG. The magnitude of common litter variance ratios (l²) was more substantial for BW (0.46) than the PWM (0.19) and KR (0.16). The estimate for the permanent environmental variance due to the animal (c²) ranged from 0.03 for LMWKB to 0.07 for TLWB and LMWKW, whereas service sire effects (s²) ranged from 0.02 to 0.04. The correlation between direct and maternal genetic effects were negative and high for BW (?0.51) and KR (?0.62). The genetic correlations between pre-weaning growth traits were positive and moderate to strong, as were genetic correlations between reproductive traits. Between BW and PWM the correlation was ?0.35. Phenotypic and environmental correlations for all traits were generally lower than genetic correlations.     

(Co)variance components and genetic parameters for growth traits in Arabi sheep using different animal models

The objective of the present study was to estimate genetic parameters for body weight at different ages in Arabi sheep using data collected from 1999 to 2009. Investigated traits consisted of birth weight (N = 2776), weaning weight (N = 2002) and weight at six months of age (N = 1885). The data were analyzed using restricted maximum likelihood analysis, by fitting univariate and multivariate animal models. All three weight traits were significantly influenced by birth year, sex and birth type. Age of dam only significantly affected birth weight. Log-likelihood ratio tests were conducted to determine the most suitable model for each growth trait in univariate analyses. Direct and total heritability estimates for birth weight, weaning weight and weight at six months of age (based on the best model) were 0.42 and 0.16 (model 4), 0.38 and 0.13 (model 4) and 0.14 and 0.14 (model 1), respectively. Estimation of maternal heritability for birth weight and weaning weight was 0.22 and 0.18, respectively. Genetic and phenotypic correlations among these traits were positive. Phenotypic correlations among traits were low to moderate. Genetic correlations among traits were positive and higher than the corresponding phenotypic correlations. Weaning weight had a strong and significant correlation with weight at six months of age (0.99). We conclude that selection can be made in animals based on weaning weight instead of the present practice of selection based on weight at six months.     

Genetic parameters and relationships between growth traits and scrotal circumference measured at different ages in Nellore cattle

Records from 106,212 Nellore animals, born between 1998 and 2006, were used to estimate (co)variance components and genetic parameters for birth weight (BW), average weight gains from birth to weaning (GBW), average weight gains from weaning to after yearling (GWAY), weaning hip height (WHH), postweaning hip height (PHH) and scrotal circumferences at 9 (SC9), 12 (SC12) and 15 (SC15) months of age. (Co)variance components were estimated by an animal model using multi-trait analysis. Heritability estimates for BW, GBW, GWAY, WHH, PHH, SC9, SC12 and SC15 were 0.31 ± 0.01; 0.25 ± 0.02; 0.30 ± 0.04; 0.51 ± 0.04; 0.54 ± 0.04; 0.39 ± 0.01; 0.41 ± 0.01 and 0.44 ± 0.02, respectively. Genetic correlations between growth traits ranged from 0.09 ± 0.01 to 0.88 ± 0.01, thereby implying that, at any age, selection to increase average weight gains will also increase stature. Genetic correlations between BW and average weight gains with scrotal circumferences were all positive and moderate (0.15 ± 0.03 to 0.38 ± 0.01). On the other hand, positive and low genetic associations were estimated between hip height and scrotal circumference at different ages (0.09 ± 0.01 to 0.17 ± 0.02). The results of this study pointed out that selection to larger scrotal circumferences in males will promote changes in average weight gains. In order to obtain Nellore cattle with the stature and size suitable for the production system, both weight gain and hip height should be included in a selection index.     

Body development in sows, feed intake and maternal capacity. Part 2: gilt body condition before and after lactation, reproductive performance and correlations with lactation feed intake

Data on sow body weight (BW) and fatness (n = ~2250 pregnant sows) and reproductive data (including historical: n = ~18 000) were used to examine the genetic and phenotypic associations between body condition before and after farrowing, gestational outcomes, lactation feed intake and the gilts' ability to survive unculled to farrow in the second parity. Within-trait genetic correlations were very high between weight (0.77 ± 0.06) and fat depth (0.91 ± 0.04) recorded before farrowing and at weaning. Litter size traits were generally uncorrelated genetically with aspects of sow BW and body condition. However, genetic correlations indicated that sows producing heavier piglets at birth had litters with increased gain (0.36 ± 0.16), and were characterised by greater weight (-0.72 ± 0.08) and fat change (-0.19 ± 0.15) during lactation, reflected to a lesser extent by lower weight (-0.12 ± 0.11) and fatness (-0.17 ± 0.10) at weaning. Genetic correlations (r(a)) between reproductive traits and lactation feed intake were generally low, but favourable. However, lactation intake was positively correlated with measures of sow size (r(a) = ~0.55), such that selection for lactation feed intake would likely be accompanied by increased mature sow size. Phenotypic correlations (r(p)) showed that sow survival to the second parity (FAR12) was positively influenced by litter size and fat depth at weaning, supporting attributes of increased fatness before farrowing, less weight loss during lactation and an increased lactation intake.     

Heritability of plasma cholesterol and triglyceride concentrations in swine

Three-hundred and eighteen female swine representing contemporary commercial swine breeds (34 Chester White, 43 Large White, 42 Landrace, 40 Yorkshire, and 159 four-breed crossbreeds) were used to evaluate genetic variation between and within breeds for levels of plasma cholesterol and plasma triglycerides. Blood was sampled from all pigs after a 16-hr fast at 154 days of age. Plasma cholesterol was measured in all pigs and triglycerides were measured in 232 pigs. Paternal half-sib heritabilities (h2) for plasma cholesterol and plasma triglycerides were 0.45 +/- 0.23 and 1.04 +/- 0.32, respectively. Breed differences were not apparent for either trait. Phenotypic and paternal half-sib genetic correlations between the two traits were 0.16 and 0.66, respectively. Neither body weight nor backfat depth were important in affecting the estimate of h2 for either trait. The relatively high h2 of total plasma cholesterol and of total triglycerides offers the possibility of developing, through selection, populations of hypercholesterolemic or hypertriglyceridemic swine useful as models for studies directed toward further understanding of human cardiovascular disease.     

Analysis of female reproductive traits in Angus beef cattle divergently selected for blood serum insulin-like growth factor I concentration

Insulin-like growth factor-I (IGF-I) is an anabolic polypeptide involved in reproductive performance in several species. The objectives of this study were to determine relationships of pregnancy rate, and age of heifers at puberty and at first calving with serum IGF-I concentration in Angus beef cattle. Data were obtained from an ongoing divergent selection experiment for IGF-I concentration involving purebred Angus cows. The IGF-I concentrations measured at Days 28, 42, and 56 of the 140-day postweaning test are abbreviated as IGF28, IGF42, and IGF56, respectively. Pregnancy rate did not differ between high and low IGF-I line females (P=0.95; n=2618), but high line heifers tended to be 4.02+/-2.18 days younger (P=0.07; n=281) at first calving. Residual correlations of age of heifers at first calving (AFC) with IGF-I measurements were not significant. The linear and quadratic terms for regression of AFC on IGF-I concentrations were also non-significant. Contrast analysis showed no difference in age at puberty between the high and low IGF-I line heifers (5.3+/-6.4 days earlier in the high line; P=0.43; n=51). Residual correlations of age of heifers at puberty with IGF28, IGF42, IGF56, and mean IGF-I were -0.30 (P=0.03), -0. 22 (P=0.12), -0.35 (P=0.01), and -0.34 (P=0.01), respectively. The observed relationships between female reproductive traits and IGF-I concentration in Angus beef cattle suggest complex and multiple roles for IGF-I in reproduction.     

Calving difficulty and calf survival in beef cows fed two energy levels

Angus and Hereford yearling heifers (469) were bred to either Hereford or Angus bulls and fed either a high level (13.3 Mcal of ME) or a low level of nutrition (7.3 Mcal of ME) for the last 116 days of pregnancy. The level of calving difficulty did not differ between heifers receiving the high (H) and low (L) level of nutrition the first year (36% and 34%) but was significantly higher (P < .01) in heifers receiving H the second year (33% vs. 16%). Calves born to heifers receiving H weighed at birth 2.7 kg more (P < .01) both years than calves born to heifers receiving L. In the first year of the study the size of the pelvic opening was 10 cm larger 1 week before calving (P < .01) in heifers receiving H than in heifers receiving L. Calf survival was not related to level of nutrition, breed of dam or breed of sire either year of the study.     

Pelvic growth, calf birth weight and dystocia in Holstein x Hereford heifers

The pelvic area was measured in 129 Holstein x Hereford heifers at 10, 16 and 22 months of age. The heifers were fed an all forage diet. Pelvic growth was not linear over time, changing from an increase of 0.27 +/- 0.2 cm(2)/day during the first 6 months of the study to 0.13 +/- 0.13 cm(2)/day during the last 6 months (P<0.01). The relationship of pelvic area to body weight, height at hooks, and distance from hooks to pins did not change with age, and a moderate correlation between the pelvic area and these other measures (R=0.20 to 0.80) was noted. The pelvic area was measured within 24 hours after calving in 76 of the heifers. The rate of increase of pelvic area/day increased significantly (P < 0.01) in the month prior to calving from 0.14+/-0.13 cm(2) to 1.15 +/- 0.88 cm(2). As a result, the pelvic area at calving had a moderate correlation (R=0.29 to 0.52) to the pelvic area prior to calving. Logistic regression and discriminant analysis techniques were used to model the influence of the pelvic area and calf birth weight on the incidence of dystocia. Ratio of the pelvic area at calving to calf birth weight significantly (P < 0.01) influenced the incidence of dystocia. Logistic regression techniques were not superior to discriminant analysis; both correctly predicted 73% of the cases. Pelvic area measurement at any time other than calving was not associated with dystocia (P >0.05). Pelvic area and calf birth weight are important determinants of dystocia in heifers. The high degree of variation noted in pelvic growth, in particular during the month prior to calving, resulted in low correlation between pelvic area at calving and the precalving measurement. Therefore, we were not able to predict dystocia by measuring the pelvic area prior to calving.     

Scrotal circumference of two-year-old bulls of several beef breeds

Scrotal circumference (SC) was measured on 7,918 2-yr-old Angus, Charolais, horned and polled Herefords, Limousin, Shorthorn, and Simmental bulls presented to culling committees at six show/sales between 1977 and 1983. Only SC data from bulls within the age range of 24 +/- 4 mo were used. Scrotal circumference data were corrected across breeds for the effects of location-year and sire and were adjusted to a common bull age of 730 d. The adjusted mean SC (+/- SE) for 2-yr-old beef bulls was Simmental, 38.8 +/- 0.10 cm (n = 540); Aberdeen Angus, 37.2 +/- 0.09 cm (n = 629); Charolais, 36.3 +/- 0.09 cm (n = 499); horned Hereford, 36.1 +/- 0.03 cm (n = 3,769); polled Hereford, 35.6 +/- 0.04 cm (n = 2,170); Shorthorn, 34.9 +/- 0.11 cm (n = 231); and Limousin, 32.2 +/- 0.18 cm (n = 80). The authors' recommendations of minimum acceptable SC for 2-yr-old beef bulls are Simmental, 36.0 cm; Angus and Charolais, 35.0 cm; horned and polled Herefords and Shorthorn, 34.0 cm; and Limousin, 33.0 cm.     

Estimates of phenotypic and genetic parameters for reproductive traits in Kermani sheep

Phenotypic and genetic parameter estimates for reproductive traits in Kermani sheep were estimated using reproductive records of 860 ewes. Data were collected during 1995–2007 at the experimental breeding station of Kermani sheep, south-east of Iran. Investigated traits were litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB) and litter mean weight per lamb weaned (LMWLW) as basic traits, total litter weight at birth (TLWB) and total litter weight at weaning (TLWW) as composite traits. Quantitative genetic analyses were performed applying restricted maximum likelihood (REML) procedure under repeatability models. Ewe age had significant effect on LMWLB, LMWLW, TLWB and TLWW (P < 0.01). However, LSB and LSW were not affected by age of the ewe. All the studied traits were significantly affected by lambing year (P < 0.01). Direct heritability estimates for LSB, LSW, LMWLB, LMWLW, TLWB and TLWW were 0.01, 0.03, 0.13, 0.22, 0.06 and 0.18, respectively, while the corresponding repeatabilities were 0.08, 0.10, 0.17, 0.29, 0.09 and 0.23, respectively. Genetic correlation estimates between the investigated traits ranged from ?0.94 for LSB–LMWLB and LSW–LMWLW to 0.99 for LSB–TLWW. Phenotypic and environmental correlations were generally lower than those of genetic correlations. Phenotypic correlations ranged from ?0.34 for LSB–LMWLB to 0.58 for TLWB-TLWW. Environmental correlations ranged from ?0.33 for LSB–LMWLB and LSW–LMWLB to 0.33 for LMWLB–LMWLW. The results suggested that selection based on TLWW could be more effective than the other traits on improvement of reproductive performance in Kermani ewes.     

Influence of slaughter age and carcass suspension on meat quality in Angus heifers

This study investigated the effects of pelvic suspension and slaughter age on longissimus thoracis et lumborum (LTL) from 40 heifers with at least 75% Angus breeding. A total of 20 heifers were slaughtered directly from pasture at 18 months of age, and carcass sides were hung either by the Achilles tendon or the pelvic bone. The other 20 heifers were assigned to an additional winter housing period and slaughtered at 22 months of age; carcass sides were hung only by Achilles suspension. All carcasses were electrically stimulated and assessed according to the EUROP carcass classification system. In addition, the LTL muscles were aged for 7 or 14 days before meat quality was evaluated for intramuscular fat (IMF), drip loss, colour, shear force, compression and sensory analysis. The 22-month-old heifers were heavier, fatter and had more IMF than 18-month-old heifers. Conformation scores (muscling) did not differ between the two slaughter groups. Pelvic suspension reduced both between- and within-animal variation for peak force, total energy and compression peak force. For the 18-month-old heifers, pelvic suspension also decreased peak force, total energy and compression variables for the LTL muscles from both ageing periods, whereas Achilles-suspended samples had lower shear force values only at day 14. Sensory analysis showed that pelvic-suspended sides had greater tenderness, lower bite resistance, less threadiness, higher juiciness and meat flavour and less visible marbling than meat from Achilles-suspended sides. Pelvic-suspended sides at 18 months of age were similar in peak force and total energy values to the 22-month-old heifers. The importance of ageing the Achilles-suspended sides was more obvious for samples from 18-month-old heifers than from the 22-month-old animals. The correlations between the different instrumental measurements and sensory tenderness were considerably higher for carcasses suspended by the Achilles tendon (r = −0.55 to 0.20) than for those hung by the pelvic bone (r = −0.25 to 0.19). More correlations between sensory-evaluated tenderness and shear variables were significant after 7 days (n = 6) of ageing than after 14 days (n = 4) of ageing. This study clearly shows the benefits of pelvic suspension, which reduces the need for additional feeding after pasture.     

Heritability estimates and adjustment factors for the effects of bull age and age of dam on yearling testicular size in breeds of bulls

Scrotal circumference, testicular length and body weight were measured in 3,090 yearling bulls of 12 breed groups finishing growth performance tests during a 5 yr period. Breeds were Limousin, Hereford, Charolais, Angus, Red Poll, Simmental, Pinzgauer, Brown Swiss, Gelbvieh and three crossbred breed groups. All bulls were born during a 60-d calving season starting in late March of each year and were subjected to similar management and environmental influences during the study. The bulls were the progeny of 307 sires averaging approximately 26 sires per breed group and 10 sons per sire. Breed group, sire within breed group, year and age-of-dam effects were important (P<0.01) for all testicular traits at both a constant age (354 d) and constant body weight (418 kg). Paternal half-sib estimates of heritability were 0.41 +/- 0.06 for ageconstant scrotal circumference, 0.34 +/- 0.06 for testicular length and 0.37 +/- 0.06 for calculated paired testicular volume, respectively. Age-constant genetic correlations between yearling body weight and testicular traits were small, indicating that testicular growth and body growth rates are largely independent, regardless of breed. Testicular size of bulls from 2-yr-old dams was smaller than that of bulls from older dams. Most of these age-of-dam effects on testicular size were removed when testicular size was adjusted for the effects of body weight, suggesting that age-of-dam effects on testicular size are primarily the result of age-of-dam effects on body weight. Age adjustment factors for yearling scrotal circumference did not differ (P>0.20) among breed groups and averaged 0.032 cm per day of age. Adjustment factors for age of dam were +1.3, +0.8, +0.4, and +0.0 cm for sons of 2-, 3-, 4- and 5-yr-old dams, respectively.     

Genetic parameters for carcass weight,conformation and fat in five beef cattle breeds

Profitability of beef production can be increased by genetically improving carcass traits. To construct breeding value evaluations for carcass traits, breed-specific genetic parameters were estimated for carcass weight, carcass conformation and carcass fat in five beef cattle breeds in Finland (Hereford, Aberdeen Angus, Simmental, Charolais and Limousin). Conformation and fat were visually scored using the EUROP carcass classification. Each breed was separately analyzed using a multitrait animal model. A total of 6879–19 539 animals per breed had phenotypes. For the five breeds, heritabilities were moderate for carcass weight (h²=0.39 to 0.48, s.e.=0.02 to 0.04) and slightly lower for conformation (h²=0.30 to 0.44, s.e.=0.02 to 0.04) and carcass fat (h²=0.29 to 0.44, s.e.=0.02 to 0.04). The genetic correlation between carcass weight and conformation was favorable in all breeds (r_G=0.37 to 0.53, s.e.=0.04 to 0.05), heavy carcasses being genetically more conformed. The phenotypic correlation between carcass weight and carcass fat was moderately positive in all breeds (r_P=0.21 to 0.32), implying that increasing carcass weight was related to increasing fat levels. The respective genetic correlation was the strongest in Hereford (r_G=0.28, s.e.=0.05) and Angus (r_G=0.15, s.e.=0.05), the two small body-sized British breeds with the lowest conformation and the highest fat level. The correlation was weaker in the other breeds (r_G=0.08 to 0.14). For Hereford, Angus and Simmental, more conformed carcasses were phenotypically fatter (r_P=0.11 to 0.15), but the respective genetic correlations were close to zero (r_G=−0.05 to 0.04). In contrast, in the two large body-sized and muscular French breeds, the genetic correlation between conformation and fat was negative and the phenotypic correlation was close to zero or negative (Charolais: r_G=−0.18, s.e.=0.06, r_P=0.02; Limousin: r_G=−0.56, s.e.=0.04, r_P=−0.13). The results indicate genetic variation for the genetic improvement of the carcass traits, favorable correlations for the simultaneous improvement of carcass weight and conformation in all breeds, and breed differences in the correlations of carcass fat.