Multiple-trait Derivative-free Restricted Maximum Likelihood Research Articles

Genetic assessment of productive and reproductive traits in Friesian, native, and crossbred cattle in Egypt

This study utilized a dataset comprising 3023 lactation records for Friesian cows, 596 records for Native cows (Baladi), and 1189 records for Crossbred cows spanning from 1994 to 2015. The objective was to estimate and assess genetic and phenotypic parameters and breeding values for 305-day milk yield (305-DMY), lactation period (LP), calving interval (CI), and days open (DO) within the Egyptian dairy context. The motivation for this research stemmed from the need to understand the genetic potential of different cattle genotypes in Egypt and identify opportunities for enhancing dairy production. Data were analyzed using the linear mixed model least squares and maximum likelihood (LSMLMW) and multiple-trait derivative-free restricted maximum likelihood (MTDFREML) programs. The analytical model included fixed effects such as season and year of calving, parity, and genotype groups, while random effects included animal and error. Unadjusted means for 305-DMY, LP, CI, and DO were calculated for each genotype group. Genotype groups significantly impacted all studied traits. Heritability estimates varied across genotype groups, with higher estimates observed in Crossbred (0.32, 0.26, 0.25, 0.23) and Native cows (0.26, 0.28, 0.28) compared to Friesian cows (0.24, 0.22, 0.16, 0.17) for productive and reproductive traits, respectively. Genetic correlations among traits ranged from 0.10 to 0.86 for the three genotype groups, while corresponding phenotypic correlations were generally small to moderate and positive. Regarding breeding values, the accuracy estimates suggested that both sires and cows could contribute to genetic improvement. This indicates the potential for enhancing dairy production through selective breeding strategies.

Genetic parameters in traits of productive importance in lines of Bombyx mori L.

In the textile industry, complex cocoon traits are closely related to silk production. The aim of the present study was to estimate genetic parameters of economic importance traits—cocoon length (CL), cocoon weight (CW) and shell weight (SW)—in three B. mori lines—Chinese (C6), Japanese (J7) and Indian (C. Nichi)—reared under different temperature and photoperiod conditions. For each of these lines, data were collected from several generations with a full‐sibling family structure and variance‐covariance component were obtained via restricted maximum likelihood (REML) estimates based on a bi‐trait animal model analysed through the multiple‐trait derivative‐free restricted maximum likelihood (MTDFREML) software. Genetic parameters of the traits varied between the silkworm lines were evaluated. Heritabilities were highest in J7 line (0.71, 0.89 and 0.93 for CL, CW and SW, respectively) followed by C6 (0.48, 0.54 and 0.50 for CL, CW and SW, respectively) and C. Nichi (0.36, 0.43 and 0.40 for CL, CW and SW, respectively). Phenotypic correlations among these lines were positive, with values ranging between 0.36 and 0.767. Similarly, genetic correlations between the analysed silkworm lines were observed to be positive, with high values ranging from 0.86 to 0.94. The evidence for environmental correlation in these lines was found only between CW‐SW traits with moderate to high values ranging from 0.600 to 0.940. The magnitude of heritability and genetic correlations implies that phenotypic variations of the CL, CW and SW traits depend mainly on genotypic variation within the J7, C6 and C. Nichi lines, and that simultaneous genetic gains are possible by implementing selection processes for any of the evaluated traits.

Alternative models for genetic evaluation of feed intake by Afrikaner cattle

The objectives of this study were to evaluate statistical models of potential utility for genetic evaluation of feed intake and to estimate the (co)variance components and genetic parameters that would be necessary for their use in a national cattle evaluation scheme. Data were from Afrikaner bulls that were tested between 1974 and 2016 in Phases C (n = 1 250) and D (n = 11 083) of the National Beef Recording and Improvement Scheme. Statistical analyses in which the number of traits varied and contemporary group effects were considered either random or fixed were conducted using multiple-trait derivative-free restricted maximum likelihood. Contemporary group effects were important. When they were considered random, the estimated phenotypic variance of feed intake increased and its heritability reduced from approximately 0.43 ± 0.09 to approximately 0.30 ± 0.06. Use of average daily gain, recorded either concurrently with the feed intake measure (ADGC) or from related bulls reared on-farm (ADGD), had relatively little effect on estimated heritability of feed intake. Thus, considering contemporary group effects random consistently increased the accuracy of the estimated breeding values. Relatively small genetic correlations between ADGC and ADGD complicated the ultimate application of data recorded in Phase C and the use of data recorded in Phase D in decoupling the phenotypes for feed intake and growth in an evaluation of feed efficiency. Some modification of testing procedures may be necessary to facilitate this application of the results.Keywords: accuracy, contemporary group, genetic parameters, performance testing

Estimation of Genetic Parameters for Peak Yield, Yield and Persistency Traits in Murciano-Granadina Goats Using Multi-Traits Models.

Simple SummaryThe Murciano-Granadina goat is a local breed of importance, not only for the economic and social impact of the breeders but also for its conservation. Estimates of the genetic parameters of peak and persistency traits (not commonly used in breeding schemes) using multivariate models is a feasible tool in early lactation (could genetically modify lactation curves) for improving sustainable production in dairy goats, specifically when more data are available. The genetic variability for the parameters of the lactation curve (peak yield, yield and persistency studied traits) is low. The heritability was low to intermediate in all the traits, being between 0.08 for persistency and 0.17 for yield. The genetic correlations were high for peak yield and yield (0.94), indicating that the selection for both peak production and persistence is feasible, with no detrimental response in either. Murciano-Granadina should be a guide dairy goat, and the result could provide a general strategy applicable to other local breeds.This paper studies parameters of a lactation curve such as peak yield (PY) and persistency (P), which do not conform to the usual selection criteria in the Murciano-Granadina (MG) breed, but are considered to be an alternative to benefit animal welfare without reducing production. Using 315,663 production records (of 122,883 animals) over a period of 24 years (1990–2014), genetic parameters were estimated with uni-, bi- and multivariate analysis using multiple trait derivative free restricted maximum likelihood (MTDFREML). The heritability (h2)/repeatability (re) of PY, yield (Y) and P was estimated as 0.13/0.19, 0.16/0.25 and 0.08/0.09 with the uni-trait and h2 of bi- and multi-traits analysis ranging from 0.16 to 0.17 of Y, while that of PY and Y remained constant. Genetic correlations were high between PY–Y (0.94 ± 0.011) but low between PY–P (–0.16 ± 0.054 to –0.17 ± 0.054) and between Y–P (–0.06 ± 0.058 to –0.05 ± 0.058). Estimates of h2/re were low to intermediate. The selection for Y–PY or both can be implemented given the genetic correlation between these traits. PY–P and Y–P showed low to negligible correlation values indicating that if these traits are implemented in the early stages of evaluation, they would not be to the detriment of PY–Y. The combination of estimated breeding values (EBVs) for all traits would be a good criterion for selection.

Estimation of genetic and environmental parameters for milk traits in jersey cows

The aim of this study was to estimate the genetic parameters and environmental factors for test day milk yield (TDMY), lactation milk yield (LMY), 305-day milk yield (305-DMY), milk fat percentage (FP) and milk protein percentage (PP) of Jersey cows raised on Karaköy Agricultural State Farm in Samsun province of Turkey. The data were obtained from 279 milk yield records of 170 heads cows calved from 2011 to 2013 years. Parity, calving season and calving year were considered as fixed effects. Heritability, additive genetic variance and phenotypic variance were estimated by multiple trait derivative free restricted maximum likelihood (MTDFREML) with the animal model. Variance analysis results showed that except for FP, the effects of parity and calving year on TDMY, LMY, 305-DMY and PP were significantly important (P<0.05). However, calving season did not affect TDMY, LMY, 305-DMY, FP and PP (P>0.05). Heritability estimates for TDMY, LMY, 305-DMY, FP and PP were 0.38, 0.30, 0.28, 0.19, and 0.36, respectively. Repeatability for TDMY, LMY, 305-DMY, FP and PP were ranged from 0.35 to 0.45. The results indicate that these traits can be used as a selection criteria in genetic improvement of Jersey cattle this herd.

CLIMATE SPATIALIZATION AND GENOTYPE-ENVIRONMENT INTERACTION EFFECTS ON WEANING WEIGHTS OF NELLORE CATTLE IN EXTENSIVE SYSTEMS IN TROPICAL REGIONS OF BRAZIL

Abstract Depending on the environmental differences among the regions, the phenotypic expression in beef cattle may significantly vary between the progenies of the same sire, and this is an important rule to identify the best animal. Thus, this study was carried out to spatialize environmental factors that may help to compare and discriminate the states of Maranhão, Pará, and Tocantins and also to check for genotype x environment interaction (G x E interaction) in these regions. The environmental variables analyzed were: maximum temperature; minimum temperature; mean temperature; precipitation; normalized difference vegetation index; relative humidity; altitude; and index of temperature and humidity. Records of weaning weight of Nellore cattle raised on pasture were collected between the years of 1997 and 2007. The dataset was constituted of 21.117 animals, progenies of 161 sires. (Co)variance components and breeding values were estimated using the multiple-trait derivative-free restricted maximum likelihood method. Multivariate spatialization revealed clear distinction among the States of Maranhão, Pará, and Tocantins and allowed the identification of important environmental variables for discrimination. The estimate for direct heritability showed moderate magnitudes and were 0.22±0013, 0.26±0.021, and 0.29±0023, for the States of Maranhão, Pará, and Tocantins, respectively. The estimates of correlation between the breeding values, predicted in different States, as well as the genetic correlation for weaning weight showed that sire ranks changed among the States, indicating G x E interaction. There was a variation of the genetic response of the progeny, depending on the sire and on the State. Thus, the G x E interaction should be accounted for in the genetic evaluation of sires and the performance of Nellore cattle under extensive breeding systems in tropical regions of Brazil.

Estimation of Genetic Parameters for 305 Days Milk Yields and Calving Interval in Xinjiang Brown Cattle

This study was conducted to estimate variance components and genetic parameters for 305 days mature equivalent milk yields (MEM) and calving interval (CAI) of registered Xinjiang Brown cattle. The total records were 3940 including 2579 for 305-day MEM and 1970 for CAI, which were collected from Xinjiang Urumqi Cattle Breeding farm in China with calving records from 1990 to 2008. Genetic parameters were obtained by multiple trait derivative-free restricted maximum likelihood (MTDFREML) using animal model. The model included year, season, parity and calving interval of calving for 305 days MEM, and year, season and parity of birth for CAI as fixed effects. Heritability for 305 days MEM was moderate (0.39) and in the same range of parameters estimated in management systems with medium production levels. Heritability of calving interval was small (0.02) as fertility traits for Xinjiang Brown cattle. Estimates of genetic and environmental correlations between 305 days MEM and CAI were 0.47 and 0.37, respectively. Estimates of genetic variation and heritability indicated that selection would result in genetic improvement of production traits. Estimates of both heritability and genetic variation for CAI were small, which indicates that genetic improvement would be difficult.

Estimation of the genetic parameters of semen quality in Beijing-You chickens

By estimating the genetic parameters of various semen quality traits in Beijing-You chickens, this study aims to elucidate the inheritance patterns of these traits and the correlations between them to facilitate setting up appropriate breeding strategies for enhanced semen quality. Semen samples were collected from 518 Beijing-You roosters at 43 wk of age from 3 selection lines related to meat flavor traits. Seven semen quality traits, consisting of semen volume, pH, and color, and sperm viability, motility, percent deformity, and concentration, were determined. Sizeable variations (18-24% CV) were observed for all traits, except for semen pH. The effects of semen collection time and origin of the chickens (line) were analyzed to optimize the proper models for estimating genetic parameters for each trait. The multiple-trait derivative-free restricted maximum likelihood method was used for estimating variance components. The results revealed that sperm viability, motility, and percent deformity exhibited high heritabilities (h(2) = 0.52, 0.85, and 0.60, respectively). Semen volume, semen color, and sperm concentration had moderate heritabilities (h(2) = 0.28, 0.19, and 0.12, respectively). Semen pH showed low heritability (h(2) = 0.03). Genetic and phenotypic correlations between sperm motility and viability were positive and high (rA = 0.88 and rP = 0.59). In addition, these 2 traits were genetically negatively correlated with percent deformity. This implied the possibility of reducing sperm deformity, which is difficult to measure, by indirect selection. It is concluded from this study that semen quality can be improved by selection. The traits with high variations and heritabilities such as semen volume are promising traits for selection to improve semen quality and likely reproductive performance of native chicken breeds.

Estimates of phenotypic and genetic parameters for birth weight of Brown Swiss calves in Turkey using an animal model

A study was conducted to assess the influence of genetic and environmental factors on Brown Swiss calf birth weight, and to estimate variance components, genetic parameters, and breeding values. Data were collected on 1,761 Brown Swiss calves born from 1990 to 2005 in the Konuklar State Farm in Turkey. Mean birth weight for all calves was 39.3 ± 0.09 kg. Least squares mean birth weights for male and female Brown Swiss calves were 40.3 ± 0.02 and 39.0 ± 0.02 kg, respectively. Variance components, genetic parameters, and breeding values for birth weight in Brown Swiss calves were estimated by restricted error maximum likelihood (REML)-best linear unbiased prediction(BLUP) procedures using an MTDFREML (multiple trait derivative free restricted maximum likelihood) program employing an animal model. Direct heritability (h(d)(2)), maternal heritability (h(m)(2)), total heritability (h(T)(2)), r(am) and c(am) estimates were 0.12, 0.09, 0.23, -0.58, and -0.06, respectively. The estimated maternal permanent environmental variance expressed as a proportion of the phenotypic variance (c(2)) was 0.05. Breeding values were estimated for the trait and used to evaluate genetic trends across the time period investigated. The genetic trend linear regression was not different from zero. No genetic trend for birth weight was expected, since there had been no direct selection pressure on the trait. Absence of a trend confirms that there was no change due to selection pressure on correlated traits. Genetic and environmental parameter estimates were similar to literature values indicating that effective selection methods used in more developed improvement programs would be effective in Turkey as well.

9 EVALUATION OF FERTILITY TRAITS OF HOLSTEIN CATTLE IN ARGENTINA

Impaired fertility is the primary reason for culling in the United States (26.5% of all disposals) and fertility rates have steadily declined during the past 30 years. The objectives of this study were 1) estimate genetic parameters and evaluate genetic correlations for fertility traits based on data from milk recording programs, and 2) evaluate genetic fertility trends in Holstein cattle in Argentina. Data representing 3 282 843 lactations and 1 622 088 animals (cows and bulls from 1936 to 2007) were used for the analysis and obtained from official records maintained by the Argentinean Holstein Association (ACHA). Lactations were standardized to 305 DIM for milk, protein, and fat. Days open (DO), calving interval (CI), age to first calving (AFC), and daughter pregnancy rate (DPR) were selected for genetic parameter estimation. Daughter pregnancy rate was calculated as described by (Kuhn et al. 2004 J. Dairy Sci. 87, 2277–2284). Animal models by lactation for each fertility trait included contemporary group (dairy herd and calving year), calving month, animal effect, milk production as a covariate, and error term. Multiple-trait derivative-free restricted maximum likelihood (MTDFREML) was used to estimate covariance components. Solutions for fixed effects, breeding values, and sampling variances (accuracies) were obtained for each trait. The fertility index ($F = –0.28 × AFC ± 4.9 × CI) was calculated using the economic rates as reported by (Gonzalez-Recio et al. 2004 J. Dairy Sci. 87, 3053–3061). First lactation/parities were utilised for estimating correlations among BLUPs for DO, CI, DPR, AFC, and $F. In general, moderate and high genetic correlations were observed (from 0.238 to 0.999; P < 0.001). Days open and calving interval showed high negative associations with DPR (–0.999, –0.648) and $F (–0.612, Q0.981). Results from the correlation analysis suggest that CI and $F are qualified indicators of fertility in lactating dairy Holstein and relate well with all the other traits. The index, $F, benefits by including AFC as a measure of initial reproductive efficiency followed by the inclusion of CI which measures success of inseminations. Genetic trend for AFC showed a decrease of 2.76 days per year between 1970 and 2000 for sires. Similarly, trends for CI resulted in decreases of 0.45 days per year between 1970 and 2000 for sires. During the same period, DPR increased by 0.02 percent per year in sires. Using current dollars values, $F increased 2.99 dollars per year for sires. Results indicate progress in the genetic trend for fertility traits in the Holstein population of Argentina, with higher improvement in sires compared with dams. Trends visually showed faster improvement after 1980, possibly due to extensive importation of US and Canadian bulls and semen (72% of bulls born after 1986) and selection for productive life introduced in 1993. Supported by Asociacion Criadores de Holando Argentino (ACHA).

21 GENETIC APPROACH TO IMPROVE FERTILITY IN CATTLE

In spite of the economic importance of fertility and increased knowledge of reproductive biology in the cow, efficiency of reproductive performance has continued to decline in dairy cattle. Improvements in fertility through genetic selection may be a possible approach to increase reproductive efficiency in dairy cattle. Although progress may be slow because of low heritabilities, ignoring fertility in genetic improvement programs has contributed to the current fertility problems. The objectives of this study were to (1) estimate genetic parameters and breeding values for fertility traits based on data from milk recording programs on a Holstein population and (2) develop a multi-trait selection index (dollar fertility value; $F) based on estimated breeding values. Data representing 3,282,843 lactations and 1,622,088 animals (cows and bulls from 1936 to 2007) were used for the analysis and obtained from official records maintained by the Argentinean Holstein Association (ACHA). Data were collected from official milk records, and lactations were standardized to 305 DIM for milk, protein, and fat. Gestation period was considered to be 282 days and restrictions were applied to ensure the quality of data (days open <40 and >350 days; calving interval <300 and >600 days; and contemporary groups with <25 lactations were eliminated). Days open (DO), calving interval (CI), age to first calving (AFC), and daughter pregnancy rate (DPR) were traits chosen for genetic parameter estimation. Daughter pregnancy rate was calculated from DO as PR = 0.25 × (233 DO); Kuhn et al. 2004 J. Dairy Sci. 87, 2277-2284. Animal models by lactation for each fertility trait included contemporary group (dairy herd and calving year), calving month, animal effect, milk production as a covariate and error term. Multiple-trait derivative-free restricted maximum likelihood (MTDFREML) was used to estimate covariance components (Boldman et al. 1995 ARS, USDA). Solutions for fixed effects, breeding values, and sampling variances (accuracies) were obtained for each trait. The proposed selection index ($F) included AFC and CI, with economic weights from -0.28 and -4.9 $/year per cow for AFC and CI, respectively (Gonzalez-Recio et al. 2004 J. Dairy Sci. 87, 3053-3061). Heritabilities for DO and DPR ranged from 2 to 7%; CI ranged from 3 to 8%; and AFC was 16%. Predicted transmitting ability values across different lactations ranged from -18.5 to 15.8 days, -23.15 to 16.0 days, -4.0 to 4.6%, and -120.3 to 76.2 days for DO, CI, DPR, and AFC, respectively. Values for $F ranged from -$89.16 to $147.12 in this Holstein population. Results indicate substantial variation in fertility traits, suggesting that genetic selection may be effective in improving declines in fertility. Asociacion Criadores Holando Argentino (ACHA).

PHENOTYPIC AND GENETIC PARAMETERS OF MILK PRODUCTION AND REPRODUCTIVE PERFORMANCE OF HOLSTEIN CATTLE UNDER THE INTENSIVE PRODUCTION SYSTEM IN EGYPT

SUMMARY Cow productivity in Holstein-Friesian cattle was analyzed in fourteen commercial private herds. All herds belong to members of the General Cooperative for Developing Animal Wealth and Products, Egypt. A total number of 4120 lactation records for 1085 cows sired by 290 bulls were used. The records covered the period from 1999 to 2003. Traits studied were 305 day milk yield (305d MY), total milk yield (TMY), lactation period (LP), dry period (DP), age at first calving (AFC) and calving interval (CI). Data were analyzed by Multiple Trait Derivative Free Restricted Maximum Likelihood (MTDFREML) procedure using repeatability multiple trait Animal Model analysis. Means of 305d MY, TMY, LP, DP, AFC and CI were 9038 kg, 12054 kg, 407 days, 63.6 days, 29.2 months and 470 days, respectively. Heritability estimates for the same traits were 0.27, 0.22, 0.07, 0.05, 0.23 and 0.05, respectively. Also, repeatability and phenotypic and genetic correlations between traits were estimated. The results indicated that raising high yielding Holsteins in commercial farms in Egypt is technically feasible. Additive genetic variance showed large contribution to total variation in milk yield traits indicating possibility of improving these traits by genetic selection. Selection based on first lactation could be used satisfactorily to improve milk yield traits.

A Comparison of Different Selection Indices for Genetic Improvement of Some Dairy Milk Traits in Holstein Friesian Cows in Turkey

Atil, H., Khattab, A.S. and Gevrekci, Y. 2005. A comparison of different selection indices for genetic improvement of some dairy milk traits in Holstein Friesian cows in Turkey. J. Appl. Anim. Res., 27: 117–120. A total of 1680 first lactation records of Holstein Friesian cows sired by 206 bulls maintained at five herds in Turkey were used to estimate phenotypic and genetic parameters for 305 day milk yield (305 dMY), lactation period (LP) and age at first calving (AFC). Data were analysed using Multiple Trait Derivative Free Restricted Maximum Likelihood (MTDFREML). The model included the fixed effects of herd, season and year of calving and parity, AFC as a covariate and individual and residual as random effects. Genetic correlations between 305 dMY and AFC; and LP and AFC were 0.90 and −0.95, respectively. Phenotypic correlations among all traits studied were generally similar to the corresponding genetic correlations. Index I1 incorporating 305 dMY, LP and AFC was the best (RIH=0.75). It is recommended that selection should be exercised at the end of the first lactation.

Heritabilities and genetic correlations of size traits at harvest size in sexually dimorphic Pacific white shrimp (Litopenaeus vannamei ) grown in two environments

A captive population of Pacific white shrimp (Penaeus vannamei) replicated in two environments was evaluated for genetic variability and covariability of size traits. A total of 37 full-sib families, each with an average of 16–20 individuals within family, were used for the analysis. There was no family by environment interaction for any of the traits. However, both fixed effects, sex and environment, were significant. The shrimp grown in environment ‘B’ (Sinaloa) grew larger and heavier than those grown in environment ‘A’ (La Paz), possibly because of the higher temperatures and lower densities in the first one during grow-out. The females were significantly larger than the males for all traits, except for abdominal (tail) length and weight. The heritabilities, estimated through MTDFREML (multiple-trait derivative-free restricted maximum likelihood) after introducing environment and sex as fixed effects, were total length 0.22±0.07, abdominal length 0.23±0.07, cephalothorax length 0.17±0.06, total weight 0.17±0.06, abdominal weight 0.18±0.06, cephalothorax weight 0.15±0.06, and width of the first abdominal segment (0.14±0.05). Genetic correlations (rg) were high between the length and weight (total and abdominal), but lower for cephalothorax weight or length with the other traits. The width of the first abdominal segment correlations with other traits was intermediate.

Peso adulto de matrizes em rebanhos de seleção da raça Nelore no Brasil

O objetivo deste trabalho foi avaliar a variabilidade fenotípica e genética do peso adulto de matrizes da raça Nelore. As informações trabalhadas foram provenientes de 34 rebanhos, de onze diferentes regiões brasileiras. Foram consideradas na análise vacas das variedades mocha e de chifres, criadas em regime de pasto, de rebanhos com no mínimo 50 matrizes. Com estas restrições, formou-se um conjunto de dados que totalizou 6.867 vacas e uma matriz de parentesco de 17.039 animais. O peso corporal indicador do peso adulto (PA) foi definido como o primeiro peso (kg) observado dentro do limite de quatro a doze anos de idade. Estes pesos foram aferidos em uma das três seguintes condições: normal, nas pesagens de rotina, em abril e outubro de cada ano, de acordo com o calendário estabelecido pelo programa, ao parto ou à desmama do produto. O tratamento de dados e as análises estatísticas foram feitos pela aplicação de procedimentos contidos no Sistema de Análise Estatística (SAS). Fazenda, ano de nascimento, ano de realização da pesagem, situação à pesagem, estação da pesagem e as interações ano*estação de nascimento e ano*estação da pesagem foram as principais causas de variação para PA. A média geral do PA foi 447 kg, com coeficiente de variação de 11%. As análises genéticas foram feitas pela aplicação do modelo animal, utilizando-se o aplicativo MTDFREML, tendo sido formados previamente 1.126 grupos de contemporâneas, reunindo-se as vacas provenientes da mesma fazenda, nascidas no mesmo ano e pesadas no mesmo ano e estação, sob a mesma condição, por ocasião da pesagem. As estimativas dos componentes genético aditivo (537,78 kg²), residual (1.553,22 kg²) e fenotípico (2.090,59 kg²), resultaram em uma estimativa de herdabilidade de 0,26. As predições dos valores genéticos para peso adulto variaram entre -41,9 a +61,4 kg, com acurácias de 0 a 0,95.

Association of a genetic marker with blood serum insulin-like growth factor-I concentration and growth traits in Angus cattle.

The objective of this research was to evaluate a biallelic genetic marker identified in the first promoter region of the bovine IGF-I gene. The point mutation was identified as a T-to-C transition by sequencing the polymorphic fragments. A PCR-RFLP procedure was developed for determining the marker genotypes. Marker genotypes were determined for 760 Angus calves from divergent lines that were created by selection for high or low serum IGF-I concentration (allele A: 63.9%, B: 36.1%). Data were analyzed using the multiple-trait derivative-free restricted maximum likelihood computer programs with animal models. The full animal model included fixed effects of marker genotype, birth year, season of birth, sex, age of dam, and selection line; random effects of animal, maternal genetic, and maternal permanent environmental effects; and a covariate for age of calf. Traits analyzed included blood serum IGF-I concentrations on d 28, 42, and 56 of the postweaning test, mean IGF-I concentration, birth weight, weaning weight, on-test weight, off-test weight, off-test hip height, postweaning gain, and weight gain during the 20-d period immediately after weaning. Results from the analysis across selection lines showed a significant association of the BB genotype with higher weight gain during the first 20 d after weaning and a slight dominance effect of the marker on postweaning gain. Analysis within the low IGF-I line also showed a significant association of the BB genotype with higher weight gain during the first 20 d after weaning and with on-test weight, although analysis within the high IGF-I line did not show any significant association. The associated effects of the marker need to be verified in other cattle populations.

Genetic parameter estimates for serum insulin-like growth factor-I concentration and carcass traits in Angus beef cattle.

Divergent selection for serum insulin-like growth factor-I (IGF-I) concentration began at the Eastern Ohio Resource Development Center (EORDC) in 1989 using 100 spring-calving (50 high line and 50 low line) and 100 fall-calving (50 high line and 50 low line) purebred Angus cows. Following weaning, bull and heifer calves were fed in drylot for a 140-d postweaning period. At the conclusion of the postweaning test, bulls not selected for breeding were slaughtered and carcass data were collected at a commercial abbatoir. At the time of this analysis, IGF-I measurements were available for 1,283 bull and heifer calves, and carcass data were available for 452 bulls. A set of multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML) computer programs were used for data analysis. Estimates of direct heritability for IGF-I concentration at d 28, 42, and 56 of the postweaning period, and for mean IGF-I concentration were .32, .59, .31, and .42, respectively. Direct heritabilities for carcass traits ranged from .27 to 1.0, .26 to 1.0, and .23 to 1.0 when the age-, fat-, and weight-constant end points, respectively, were used, with marbling score having the smallest heritability and longissimus muscle area having the highest heritability in each case. Maternal heritability and the proportion of phenotypic variance due to permanent environmental effect of dam generally were < or = .21 for IGF-I concentrations and for carcass traits other than longissimus muscle area. Additive genetic correlations of IGF-I concentrations with backfat thickness, longissimus muscle area, hot carcass weight, marbling score, quality grade, and yield grade averaged -.26, .19, -.04, -.53, -.45, and -.27, respectively, when carcass data were adjusted to an age-constant end point. Bulls with lower IGF-I concentrations had higher marbling scores and quality grades, but also had higher backfat thickness and yield grades regardless of the slaughter end point. Serum IGF-I concentration may be a useful selection criterion when efforts are directed toward improvement of marbling scores and quality grades of beef cattle.

Repeatability and heritability of response to superovulation in Holstein cows

The objective of this study was to estimate the relative effects of genetic and phenotypic factors on the efficacy and efficiency of superovulation for Holstein-Friesian cows reared in Brazil. A database, established by the Associação Brasileira de Criadores de Bovinos da Raça Holandesa, consisting of a total of 5387 superovulations of 2941 cows distributed over 473 herds and sired by 690 bulls was used for the analysis. The records were analyzed by MTDFREML (Multiple Trait Derivative-Free Restricted Maximum Likelihood), using a repeatability animal model. The fixed effects included in the model were contemporaneous group (veterinarian, herd, year and season of the superovulation); number of semen doses; cow age; and superovulation order. The estimated repeatability of the number of the transferable embryos was low (0.13), and the estimated heritability was 0.03. These results indicate that environmental factors play a critical role in the response of a cow to a superovulation treatment. There is little evidence that future responses to superovulation by individual females can be predicted by previous treatment(s) or that superovulation response is an heritable trait.

Repeatability and heritability of response to superovulation in holstein cows

The objective of this study was to estimate the relative effects of genetic and phenotypic factors on the efficacy and efficiency of superovulation for Holstein-Friesian cows reared in Brazil. A database, established by the Associação Brasileira de Criadores de Bovinos da Raça Holandesa, consisting of a total of 5387 superovulations of 2941 cows distributed over 473 herds and sired by 690 bulls was used for the analysis. The records were analyzed by MTDFREML (Multiple Trait Derivative-Free Restricted Maximum Likelihood), using a repeatability animal model. The fixed effects included in the model were contemporaneous group (veterinarian, herd, year and season of the superovulation); number of semen doses; cow age; and superovulation order. The estimated repeatability of the number of the transferable embryos was low (0.13), and the estimated heritability was 0.03. These results indicate that environmental factors play a critical role in the response of a cow to a superovulation treatment. There is little evidence that future responses to superovulation by individual females can be predicted by previous treatment(s) or that superovulation response is an heritable trait.

Selection response for feed conversion and growth traits in polled Hereford cattle (1999)

Direct and correlated responses to selection for improved feed conversion were estimated from performance records of 1459 Polled Hereford cattle born from the spring of 1967 through the spring of 1979. Data were analyzed using a multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML) procedure. A full animal model was used to calculate genetic and phenotypic (co)variances. The withinherd breeding values that resulted from the solution of the mixed model equations were regressed on year to create selection response curves. Feed conversion was shown to respond favorably to direct selection, with feed/gain changing -.005 per year.