Additive Breed Effects Research Articles

Genetic parameters for carcass and meat quality traits in Jinhua, Duroc, and their crossbred pigs.

Jinhua pigs have excellent meat quality and intramuscular fat content (IMF). Crossbreeding of Jinhua with Duroc pigs with high productivity was conducted to develop a new composite breed that possesses the beneficial characteristics of both breeds. The objective of this study was to estimate the crossbreeding parameters (additive breed, dominance, and epistatic loss effects) using the Kinghorn model and genetic parameters (heritability and genetic correlation) for carcass and meat quality traits by analysing the phenotypic data of Jinhua, Duroc, and their crossbred pigs. Backfat thickness at the thinnest point above the 9th to 13th thoracic vertebrae (BF), longissimus muscle area between the 4th and 5th thoracic vertebrae (LMA), meat shear force value (SFV), and IMF were measured. The additive breed effects were significant for all traits: 1.59 cm, -8.30 cm2 , -6.38 lb/cm2 , and 1.76% for BF, LMA, SFV, and IMF, respectively. The dominance effect was significant for LMA (7.41 cm2 ) and IMF (-2.46%), whereas the epistatic loss effect was significant for only LMA (-15.18 cm2 ). The estimated heritability values were high, ranging from 0.58 for IMF to 0.76 for LMA. A negative but non-significant genetic correlation of -0.11 was estimated between BF and IMF; however, previous studies have reported that the genetic correlation between these traits is moderately positive in modern western pigs. Our results imply that, with the estimation of crossbreeding and genetic parameters, genetic improvement could be implemented to produce a new composite breed with good meat quality and productivity, to meet Japanese market requirements, by crossbreeding Jinhua and Duroc pigs.

Comparison of three maternal composite sheep breeds managed under pasture lambing and purebred or terminal mating systems: ewe body weight, reproductive efficiency, and longevity.

Extensive sheep systems have lower inputs (e.g., feed, labor, infrastructure) but, generally, lower outputs per ewe than intensively managed flocks. Average ewe prolificacy is low (< 1.1 lambs per ewe) across the United States and traditional expectation is that costs required to support larger litters will not be recovered due to greater lamb mortality. The Composite-IV (C-IV) is a 50% Romanov, 25% Katahdin, and 25% White Dorper hair sheep developed and selected for enhanced reproductive efficiency at the U.S. Meat Animal Research Center. Objectives of the current study were to compare productivity of C-IV ewes (N = 404) to Katahdin (N = 342) and Polypay (N = 390), two popular maternal composite breeds, in a lower-input system. Experimental ewes were exposed to either rams of their own breed or Texel rams for the first time at 7 mo of age and remained in the same mating system for up to 4 yr. Ewes lambed on pasture from May to June and were expected to rear their lambs in the absence of supplemental feed and with minimal intervention. The ewe age × breed interaction effect impacted all annually recorded traits (P < 0.01) including number and total weight of lamb marketed at 25 wk per ewe exposed to mating (LS25 and LW25, respectively). Within all ages, LS25 of C-IV was greater (1.2 to 1.63 lambs; P < 0.01) than Katahdin (0.71 to 1.17 lambs) and Polypay (0.68 to 1.26 lambs) which were similar. At 1, 2, and 3-yr of age, C-IV ewes had, on average, 12 to 17 kg greater LW25 (P ≤ 0.01) than other breeds. Polypay LW25 was similar to Katahdin at 1 yr of age, but 8 to 13 kg greater (P < 0.01) at older ages. At 4 yr of age, LW25 was similar for C-IV and Polypay (63 and 62 kg, respectively). Overall, Texel mating improved LW25 by 3 kg compared to purebred mating (P < 0.01). Twin litters were most common within mature ewes (> 1 yr) of all breeds (52% to 65%); however, the proportion of triplet litters was numerically greater for C-IV (13%) than Katahdin (1%) or Polypay (4%). The frequency of mature ewes that gave birth to and reared twins (75% to 82%) was high for all breeds. Most triplet-bearing mature C-IV ewes reared twins (43%) though many reared triplets (39%). Ewe reproductive efficiency can be enhanced in lower-input systems by utilizing additive breed effects and heterosis in a complimentary crossbreeding program. More research is needed to identify indicator traits associated with lamb survival and to derive appropriate levels of prolificacy to fit specific management constraints.

Breed and crossbreeding effects on growth, fitness and reproduction of commercial sheep in South Africa

The study aimed to assess additive breed effects for growth (birth, weaning and ewe adult weight), fitness (lamb survival and tick count under natural challenge) and ewe reproduction traits per ewe mated in Dorpers, the most common meat breed in South Africa (SA), and the SA Mutton Merino (SAMM) a prominent dual-purpose breed in SA extensive environments. Additionally, the reciprocal crosses between the two breeds were used to estimate dam breed effects and heterosis. No conclusive additive breed differences were found for lamb weight traits, lamb survival or tick counts. There was a suggestion that lamb survival of Dorpers was higher than that of their SAMM contemporaries, but significance could not be demonstrated. Crossbred progeny outperformed the midparent value by 7.1% for weaning weight. As far as mature ewes were concerned, mating weight was affected by breed combination with the mating weights of purebred SAMM ewes as well as crossbred ewes exceeding that of purebred Dorpers. Number of lambs born per ewe lambed was independent of the genetic group. The SAMM x Dorper group outperformed the pure breeds for number of lambs weaned per ewe mated (NLW). Contrasts for additive breed and maternal heterosis were not significant for NLW, but direct heterosis amounted to 32.5%. Crossbred ewes performed better than the pure breeds for total weight of lamb weaned per ewe lambed, direct heterosis amounting to 38.4%. The other contrasts were not significant. A lack of additive effects for traits, barring ewe mating weight suggested that the breeds performed similarly under the conditions of the study. Significant heterosis effects for weaning weight as well as number and weight of lamb weaned suggest a role for crosses between Dorpers and SAMMs in commercial lamb production enterprises.

Estimates of breed additive, heterosis and epistasis genetic effects on milk production and reproductive traits from indigenous Borena and crosses with Holstein Friesian dairy cows at Holetta dairy research farm, Ethiopia

Estimates of breed additive, heterosis and epistasis genetic effects on milk production and reproductive traits from indigenous Borena and crosses with Holstein Friesian dairy cows at Holetta dairy research farm, Ethiopia

Nasljeđivanje porodne mase kod križanaca Istarske, Awassi, Istočnofrizijske i Travničke pasmine ovaca u Hrvatskoj: studija sa jedne farme

The purpose of the study was to estimate the influence of the additive and non-additive genetic effects on the birth weight, using two different crossbreed models. Data on 1176 birth weights were collected. The animals were crosses, with different ratios of Awassi, East-Friesian, Istrian, and Travnik Pramenka sheep breed. The focal breed in this study was Istrian, which is an autochthonous breed in Croatia. In both models mixed procedure was used with random effect of sire and fixed effects of sex, year and month of birth, litter size, and direct inbreeding. The first model contained the additive breed effects, while the second model additionally included non-additive effects of heterosis and recombination loss. Sex, litter size, year and month of birth significantly affected birth weight in both models. Effect of direct inbreeding was negative and significant only in second model. Significant positive additive breed effect was estimated for Awassi breed in both models. The East-Friesian additive breed effect was positive in both models, but it was significant for the first one only. The positive and significant heterosis effect for the birth weight was estimated for the crosses between East-Friesian and Travnik Pramenka, as well as between Travnik Pramenka and Istrian breed. Same crosses showed significant and positive effect of recombination loss. The negative effect of recombination loss was estimated for the crosses of Awassi breed.

Breed direct, maternal and heteros is effects due to Angus, Caracu, Hereford and Nelore on carcass and meat quality traits of cull cows

• The Caracu breed can be used in crossbreeding with Angus to take heterosis and also to improve meat tenderness. • The carcass weight and meat tenderness can be obtained by crossing taurine breeds. • The cross between taurine and Zebu breeds leads to higher carcass yield and ribeye area. Meat is an end-of-life by-product from cows that fail to reproduce. Thus, the objective of this study was to determine breed additive and heterosis effects on carcass traits and characteristics of the meat from beef cows raised in southern Brazil. Angus (A), Hereford (H), Nelore (N), A × H (AH), H × A (HA), A × N (AN), N × A (NA) and Caracu (C) × A (CA) cows were slaughtered when they did not become pregnant for a second season. Slaughter weight (SW), hot carcass weight (CW), carcass yield (CY), ribeye area (REA), pH value, water holding capacity (WHC), tenderness (MT), moisture (MM), ether extract (EE), carcass fat score (CFS), marbling score (MS), subcutaneous fat thickness (SFT) and L*, a* and b* measures of color of the fat and meat color were evaluated. Taurine x taurine heterosis effects increased SW and to a lesser degree CW, and improved MT. Taurine x indicine heterosis increased REA, a* and b*, and decreased L* and EE. Direct breed additive effects attributable to A increased SW but decreased CY and thus had no detectable effect on CW. Direct breed additive effects of C decreased CFS, SFT, CY and MM. Finally, direct breed additive effects of H and C similarly decreased CFS and SFT. Maternal breed additive effects were generally unremarkable except for slight effects of H reducing a* and b*. Thus, SW and MT may be increased by crossbreeding with taurine breeds, while CY and REA can be increased by using zebu-influenced cattle. The desirable carcass composition of CA cows and their MT and color comparable to taurine crossbred cows make this crossbred cow a viable alternative for producers in southern Brazil.

Genetic effects from an Afrikaner, Bonsmara, and Nguni three-breed diallel and top-crosses of Angus and Simmental sires

Individual and maternal breed additive effects and heterosis exist for most economically important traits in cattle. Crossbreeding may therefore be valuable for emerging and commercial beef farmers in improving the productivity of their herds. Calves were produced by mating Afrikaner, Bonsmara and Nguni cows to Afrikaner, Bonsmara, Nguni, Angus and Simmental bulls. The cows used were from Vaalharts Research Station or were purchased from other herds. Data were collected over three years. Individual and maternal additive effects and individual heterosis were estimated simultaneously as continuous linear variates. The estimated genetic effects were then used to predict production levels that may be achieved through implementation of top-cross, two-breed rotation, and terminal sire crossbreeding systems. The individual estimates of the genetic effects were relatively small and in most cases were not different from zero, with the exception of the maternal additive effects of Nguni on preweaning traits and their individual additive effect on cow weight, which were less than those of Bonsmara. However, the alternative crossbreeding systems differed across traits. The straight-bred breeding system was least efficient, followed by the crisscross system (+2%) and the terminal sire system that utilized Simmental (+4%), with the terminal sire system utilizing Angus being on average most efficient (+8%). The inter-generational genetic differences in cow weight that resulted from the use of different breeds of sire increased its standard deviation by 5 to 6% in rotational crossing. Despite the relatively small magnitude of the genetic effects, advantages of crossbreeding systems became evident.Keywords: breed additive, crossbreeding, heterosis, post-weaning, pre-weaning

Inbreeding affects racing performance negatively in the Standardbred trotter

ABSTRACT We estimated the effect of inbreeding on racing performance in the Standardbred trotter. A random sample of 1,217 horses with organized pedigree was utilized to calculate individual proportions of French and American ancestry and their heterozygosity and inbreeding coefficients. Average earnings per start for the 807 raced horses summarized between three and five years of age were analysed, after first applying a fourth-root transformation followed by standard-normalization within their birth-year group (1988 and 2006/2007). The resulting variable was analysed using a linear model with fixed effects of sex, additive breed effect and a regression on the squared inbreeding coefficient. The model was expanded with a fixed effect of birth-year and a random effect of animal. In both models, the regression coefficient for the squared inbreeding coefficient was found negative (P < 0.04). Breed effect was not significant. Heritability was estimated as 0.227 ± 0.106.

Estimation of breed and heterosis effects for cow productivity, carcass traits and income in beef × beef and dairy × beef crosses in commercial suckler cow production

ABSTRACT This study aims to investigate calving difficulties, birth-, weaning- and carcass weight, herd life of cow, age at slaughter, average daily carcass gain, carcass conformation, carcass fatness and carcass income per carcass, kg or day, in Aberdeen Angus (A), Hereford (H), Charolais (C), Limousin (L), Simmental (S), Norwegian red (N) and their crosses, in order to evaluate crossbreeding strategies. Direct and maternal breed additive and heterosis effects and predicted phenotypic means were estimated with multiple regression using SAS. Crosses with N resulted in higher weaning weight and less calving difficulties than beef purebreds. Due to favourable maternal additive effects of N on carcass weight and -income, crosses with British breeds had higher performance than the purebreds. (A × C) × C had overall high performance due to beneficial maternal heterosis effects on calving difficulties and carcass weight. In conclusion, utilising profitable heterosis effects have potential in commercial production, but are dependent on production systems.

Crossbreeding effects on growth and efficiency in beef cow-calf systems: evaluation of Angus, Caracu, Hereford and Nelore breed direct, maternal and heterosis effects.

The objective of this study was to determine breed additive and heterosis effects on growth curves, total milk yield (TMY), calf weaning weight (WW), predicted energy intake (EI), and cow efficiency (CE) of purebred and crossbred beef cows raised in Southern Brazil. The data were from 175 purebred and crossbred cows representing eight genetic groups: Angus (A), Hereford (H), Nelore (N), A × H (AH), H × A (HA), A × N (AN), N × A (NA), and Caracu (C) × A (CA). Growth of the cows was modeled using the nonlinear Brody function and machine milking was used to assess TMY. WW was linearly adjusted to 210 d. EI was predicted with an equation in which the independent variables were estimates of parameters of the Brody function and TMY. The ratio of WW to EI estimated CE. Taurine–indicine heterosis effects were significant for all traits, and greater than those for taurine breed crosses. In general, crossbred cows were heavier at maturity, matured earlier, produced more milk, weaned heavier calves, and were predicted to consume more energy. Thus, they were more efficient than purebred cows, despite their greater predicted feed intake. Among the purebreds, A cows matured most rapidly, weighed the least at maturity, produced the most milk, weaned the heaviest calves, were predicted to consume the least energy; and were therefore most efficient among the breeds that were evaluated. These results are useful as inputs to bioeconomic models that can be used to predict productive and economic outcomes from crossbreeding and to facilitate recommendations for beef producers of southern Brazil and other similar subtropical climatic regions.

Estimates of genetic parameters and genetic trends for growth, reproduction, milk production and milk composition traits of Awassi sheep

Genetic parameters and genetic trends for growth, reproduction, milk production and composition traits were estimated for Syrian (S) and Turkish (T) Awassi sheep and their crosses maintained at the International Center for Agricultural Research in the Dry Areas Tal Hadya station, Aleppo, Syria (now in Terbol station in Lebanon). The data were spread over 9 years. The individual breed additive effects of T were positive and significant (P<0.05) for birth weight (BW). However, the values for weaning weight (WW) and pre-weaning weight gain (WG) were negative, even though they were significant (P<0.05). These estimates were positive and significant (P<0.05) for all reproduction and milk traits, except for litter weight at birth (LWB). The additive contributions of T were 60.72±0.94 days, 1.643±0.359 kg, 13.09±0.89 days, 16.13±0.89 kg, 1.12±0.44 kg, 0.71±0.26 kg, 2.80±0.72 kg and 0.83±0.32 kg for lambing interval (LI), litter weight at weaning (LWW), lactation length, milk yield, fat yield, protein yield, total solids yield and lactose yield, respectively. The heterosis effects, both individual and maternal, were non-significant (P>0.05) for most growth traits. Crossing of T with S, however, resulted in desirable and significant (P<0.05) individual heterosis effects for all the reproduction, milk production and constituent yields. The heritability (h²) estimates, both direct and maternal, were low for BW, WW, WG and all reproductive traits indicating major influence of environmental factors, whereas milk yield and composition had medium values. Birth weight had moderate genetic correlation with WW and WG. The genetic correlation between WW and WG was high (0.724±0.951). Lambing interval had large negative genetic correlation with LWB and LWW. However, LI had medium significant correlations with all the milk production and composition traits. Larger litter weights at birth had high and negative influence on milk yield of the dam and its constituents. Genetic changes over years for all traits were non-significant. The lack of genetic change in the studied traits calls for systematic and organized selection scheme.

Modelling non-additive genetic effects using ridge regression for an Angus–Nellore crossbred population

Data from 294045 records from a crossbred Angus × Nellore population were used to estimate fixed genetic effects (both additive and non-additive) and to test different non-additive models using ridge regression. The traits studied included weaning gain (WG), postweaning gain (PG), phenotypic scores for weaning (WC) and postweaning (PC) conformation, weaning (WP) and postweaning (PP) precocity, weaning (WM) and postweaning (PM) muscling and scrotal circumference (SC). All models were compared using the likelihood-ratio test. The model including all fixed genetic effects (breed additive and complementarity, heterosis and epistatic loss non-additive effects, both direct and maternal) was the best option to analyse this crossbred population. For the complete model, all effects were statistically significant (P &amp;lt; 0.01) for weaning traits, except the direct breed additive effects for WP and WM; direct complementarity effect for WP, WM, PP and PM and maternal epistatic loss for PG. Direct breed additive effect was positive for weaning traits and negative for postweaning. Maternal breed additive effect was negative for SC and WP. Direct complementarity and heterosis were positive for all traits and maternal complementarity and heterosis were also positive for all traits, except for PG. Direct and maternal epistatic loss effects were negative for all traits. We conclude that the fixed genetic effects are mostly significant. Thus, it is important to include them in the model when evaluating crossbred animals, and the model that included breed additive effects, complementarity, heterosis and epistatic loss differed significantly from all reduced models, allowing to infer that it was the best model. The model with only breed additive and heterosis was parsimonious and could be used when the structure or amount of data does not allow the use of complete model.

Evaluation of Rambouillet, Polypay, and Romanov–White Dorper × Rambouillet ewes mated to terminal sires in an extensive rangeland production system: Lamb production1,2

Ewe productivity (i.e., total number or weight of lambs weaned per breeding ewe) is a key indicator of lamb production efficiency. This study compared various measures of ewe productivity and ewe and lamb performance among ewes of 3 breed types mated to rams of 4 terminal-sire breed types in an extensive rangeland production system. Purebred Rambouillet (n = 212), purebred Polypay (n = 236), and crossbred Romanov–White Dorper × Rambouillet (RW-RA; n = 231) ewes were produced from locally adapted Polypay and Rambouillet ewes and then annually mated to Columbia, Suffolk, Columbia × Suffolk, or Suffolk × Columbia sires for up to 4 yr, beginning at 1 yr of age. The cumulative number and weight of lambs weaned through 4 yr were greater for RW-RA (5.9 lambs and 153 kg, respectively) and Polypay ewes (4.9 lambs and 123 kg, respectively) than for Rambouillet ewes (2.9 lambs and 99 kg, respectively) and also were greater for RW-RA ewes than for Polypay ewes (all P < 0.001). Greater productivity of RW-RA and Polypay ewes, compared with Rambouillet ewes, was driven by greater lambing rates (ewes lambing per ewe exposed) as ewe lambs (87 and 77 vs. 31%, respectively; P < 0.001) and greater (P < 0.001) litter sizes as ewe lambs (1.3, 1.3, and 1.0, respectively) and adult ewes (2.1, 2.0, and 1.6, respectively). The RW-RA ewes also had greater longevity (P < 0.01) and cumulative lambing rates (P < 0.001) than Polypay and Rambouillet ewes. Lamb BW at birth and weaning in adult ewes favored less-prolific Rambouillet ewes (P < 0.001), but after adjustment for type of birth and rearing and weaning age, differences in weaning BW among ewe breed types were small and not significant (P = 0.08). Effects of sire breed type on measures of cumulative ewe productivity were not significant (P > 0.74), but Suffolk-sired lambs had the heaviest adjusted birth weights (P = 0.01) and Columbia-sired lambs tended to have the lightest adjusted weaning weights (P = 0.12). Combined effects of heterosis and additive breed effects were associated with greater lambing rates in ewe lambs, larger litters at all ages, and substantially greater number and weight of lambs weaned for Polypay and RW-RA ewes than for Rambouillet ewes.

Estimation of genetic parameters and heterosis for longevity in crossbred Danish dairy cattle.

Crossbreeding has been shown to improve the longevity of dairy cattle in countries across the world. The aim of this study was to estimate heterosis, breed effects, and genetic parameters for longevity in crossbred dairy cattle among Danish Holstein (DH), Danish Red (DR), and Danish Jersey (DJ) breeds. Data were provided from 119 Danish commercial herds that use systematic crossbreeding (i.e., rotational crossbreeding). Additional data from 11 mixed-breed herds with DH and DJ were included to estimate reliable breed effects for DJ. Survival information on 73,741 cows was analyzed with a linear animal model using the artificial insemination-REML algorithm in the DMU package. Five longevity (L) traits were defined: days from first calving until the end of first lactation or culling (L1), days from first calving until the end of second lactation or culling (L2), days from first calving until the end of third lactation or culling (L3), days from first calving until the end of fourth lactation or culling (L4), and days from first calving until the end of fifth lactation or culling (L5). Heritabilities ranged between 0.022 and 0.090. Additive breed effects in units of days were estimated relative to DH for DR as -0.5 (L1), +10.5 (L2), +18.5 (L3), +11.9 (L4), and +28.6 (L5), and corresponding figures for DJ were +2.0, +0.5, +14.2, +27.7, and +44.0. Heterosis effects in L1 were low (1.2%) but favorable in crosses between DH and DR, whereas negative heterosis effects were estimated for crosses between DH and DJ (-2.5%) and DR and DJ (-1.2%). The largest heterosis effects for L2, L3, L4, and L5 were found in DH × DR and were favorable (+3.3, +5.7, +7.7, and +8.5%, respectively). Corresponding figures for heterosis effects in DH × DJ and DR × DJ were favorable as well: +2.3, +4.1, +5.6, and +6.2% in DH × DJ and +3.1, +7.3, +6.9, and +7.2% in DR × DJ. The favorable heterosis effects show that crossbreeding is an efficient tool for improving longevity in Danish dairy cattle.

Evaluation of Rambouillet, Polypay, and Romanov-White Dorper × Rambouillet ewes mated to terminal sires in an extensive rangeland production system: Lamb production.

Ewe productivity (i.e., total number or weight of lambs weaned per breeding ewe) is a key indicator of lamb production efficiency. This study compared various measures of ewe productivity and ewe and lamb performance among ewes of 3 breed types mated to rams of 4 terminal-sire breed types in an extensive rangeland production system. Purebred Rambouillet ( = 212), purebred Polypay ( = 236), and crossbred Romanov-White Dorper × Rambouillet (RW-RA; = 231) ewes were produced from locally adapted Polypay and Rambouillet ewes and then annually mated to Columbia, Suffolk, Columbia × Suffolk, or Suffolk × Columbia sires for up to 4 yr, beginning at 1 yr of age. The cumulative number and weight of lambs weaned through 4 yr were greater for RW-RA (5.9 lambs and 153 kg, respectively) and Polypay ewes (4.9 lambs and 123 kg, respectively) than for Rambouillet ewes (2.9 lambs and 99 kg, respectively) and also were greater for RW-RA ewes than for Polypay ewes (all < 0.001). Greater productivity of RW-RA and Polypay ewes, compared with Rambouillet ewes, was driven by greater lambing rates (ewes lambing per ewe exposed) as ewe lambs (87 and 77 vs. 31%, respectively; < 0.001) and greater ( < 0.001) litter sizes as ewe lambs (1.3, 1.3, and 1.0, respectively) and adult ewes (2.1, 2.0, and 1.6, respectively). The RW-RA ewes also had greater longevity ( < 0.01) and cumulative lambing rates ( < 0.001) than Polypay and Rambouillet ewes. Lamb BW at birth and weaning in adult ewes favored less-prolific Rambouillet ewes ( < 0.001), but after adjustment for type of birth and rearing and weaning age, differences in weaning BW among ewe breed types were small and not significant ( = 0.08). Effects of sire breed type on measures of cumulative ewe productivity were not significant ( > 0.74), but Suffolk-sired lambs had the heaviest adjusted birth weights ( = 0.01) and Columbia-sired lambs tended to have the lightest adjusted weaning weights ( = 0.12). Combined effects of heterosis and additive breed effects were associated with greater lambing rates in ewe lambs, larger litters at all ages, and substantially greater number and weight of lambs weaned for Polypay and RW-RA ewes than for Rambouillet ewes.

Breed genotype effect on ewe traits during the pre-weaning period in hair sheep under the tropical Mexican conditions

The present study was carried out on a commercial farm in southwest of Mexico to determine breed group effects of hair sheep (Pelibuey, Dorper, Katahdin, and Blackbelly and their crosses) and their genetic components (breed additive, breed maternal and heterosis effects on litter weight at birth, adjusted litter weaning weight at 60 days, and lambing interval. The dataset included records from 1821 four-purebred ewes and crossbreed groups (representing 9 different crosses between the four pure breeds). In total, there were 6371 lambing events from 2007 to 2013. The first model included the effects of breed, parity, litter size, season of lambing, year of lambing and season×year interaction. Those significant effect (P<0.05) were included in the models to estimate the breed additive, breed maternal and heterosis effects. Breed additive and breed maternal effects were expressed as deviations from the Pelibuey breed. Breed, parity and litter size were significant sources of variation for all the traits (P<0.05), but season and year interaction were significant only for litter birth and weaning weight (P<0.05). Heterosis effect was only observed for adjusted litter weaning weight at 60 days of age for the Pelibuey×Katahdin crossbred ewes (P<0.05). Under the conditions of this study, direct heterosis and maternal effects between the four breeds studied has shown no significant effect on these traits. Non-genetic factors had a greater influence on the traits studied than the genetic makeup of the ewe.

Modeling breed additive and non-additive genetic effects using a Angus x Nellore crossbred population

The objectives of this study were to estimate fixed genetic (both additive and non-additive) effects and test different non-additive models. These effects included direct and maternal joint breed additive effects, direct and maternal complementarity (or profit heterosis), direct and maternal heterosis (dominance) and direct and maternal epistatic loss non-additive effects. A large crossbred Angus x Nellore population with approximately 300,000 records for weaning gain (WG) and 150,000 records for post-weaning gain (PG) was used. Phenotypic scores for weaning (WC) and post-weaning (PC) conformation, weaning (WP) and post-weaning (PP) precocity, weaning (WM) and post-weaning (PM) muscling and scrotal circumference (SC) were also used. All models included the fixed contemporary group effect and random animal, maternal genetic and permanent environment effects. Each model was tested against all other models for all nine traits using the likelihood ratio test. The complete model, including all additive and non-additive effects and the model without complementarity, were seen to be the best options to analyze this crossbred population. However, least squares may not be the best methodology due to possible collinearity among estimates that may inflate the variance. In the complete model most effects were statistically significant (P<0.01) for weaning traits, except for direct and maternal breed additive effects and direct complementarity effect for WM. For post-weaning traits, the direct complementarity effect for phenotypic scores (PC, PP and PM) and the maternal heterosis effect for PG, PC, PM, were not statistically significant. For scrotal circumference the maternal complementarity, direct and maternal heterosis and maternal epistatic loss effects were not statistically significant. All other effects were statistically significant (P<0.01). For the model without complementarity, the direct breed additive effect for PG and PP was not statistically significant, including the maternal breed additive effect for WC, WD, PP and PM and maternal heterosis, direct and maternal epistatic loss effects for SC. Considering all models, significant direct breed additive effect was mostly positive for weaning traits and was negative for all post-weaning and SC. The significant maternal breed additive and maternal complementarity effects for SC were all negative. The significant direct and maternal epistatic loss effects were negative for all traits and for all models, except for PG in the complete model and for weaning traits in the model including only breed additive and epistatic loss effects. We conclude that the fixed genetic effects are mostly significant, thus it is important to include them in the model when evaluating crossbreed animals and the models including breed additive effects, heterosis and epistatic loss with or without complementarity were the more appropriate.

Crossbreeding to increase beef production: additive and non-additive effects on weight traits

Using breed differences effectively facilitates high productivity and profitability. Thus, the objective of the study was to estimate direct and maternal additive and heterosis effects for growth traits (birth weight, weaning weight, 19-month weight of heifers and cow weight) from five purebred and 24 crossbred breed types. Afrikaner (A), Brahman (B), Charolais (C), Hereford (H) and Simmentaler (S) were evaluated as purebreds and as sire breeds on A and F1 BA, CA, HA and SA females. Breed additive effects were expressed as deviations from A. Effects of intra-breed genetic trend were assumed to be zero throughout. Solutions for the breed additive and heterosis effects were used to predict performance of the crossbred breed types to verify the adequacy of the genetic model. Correlations of observed and predicted means ranged from 0.87 for weaning weight to 0.94 for 19-month weight. Breed direct effects were consistently greatest for C and least for A across all traits, and maternal effects were greatest for S (except for 19-month weight) and least for C. Direct and maternal heterosis, on average, were positive for all weights. The indicus x sanga and indicus x taurus direct heterosis effects on all weight traits were greater than either the taurus x sanga or taurus x taurus effects, whereas the indicus x sanga maternal heterosis effect was consistently less than the estimated taurus x sanga maternal heterosis effect.Keywords: Direct effects, heterosis, maternal effects, taurus, indicus, sanga

Genetic analysis of somatic cell score in Danish dairy cattle using random regression test-day model

The objective of this study was to estimate the genetic and permanent environmental (PE) covariance functions for test-day records of logarithm of somatic cell count (SCS) of the first lactation for Danish Holstein cattle, and to test the hypotheses that: genetic and environmental variances change over first lactation, genetic correlations are near unity between any time points in first lactation, and including a Wilmink term will improve the likelihood of more than an extra order Legendre polynomial.Ten data sets, consisting of 1,190,584 test day somatic cell count (SCC) records from 149,233 Danish Holstein cows, were extracted from the national milk recording database. Each data set was analyzed with random regression models using AI-REML. Fixed effects in all models were age at first calving, herd test day, days carrying calf, effects of germ plasm importation (e.g. additive breed effects and heterosis) and stage of lactation as a fifth order normalized Legendre polynomial (LP) combined with a Wilmink term (exp(−0.09*DIM)). Random effects were co-variance functions for PE and additive genetic effects. The first and second data sets were analyzed using two classes of models. In the first class, PE and genetic effects were modeled by 1st to 4th order LPs combined with a Wilmink term. In the second class, 1st and 5th order LPs for PE effect and for genetic effect were modeled without Wilmink term. Of the models tested, the model with fifth order LP for both PE and genetic effects had the lowest −2ln(L). Furthermore, based on a likelihood ratio test, this model was not significantly better than a model with fifth order LP for PE effect and a fourth order LP for genetic effects. The last two models were applied to the other data sets (set 3 to set 10). In all ten data sets, the model with fifth order LP for PE effect and genetic effect were adequate to fit the data. The average heritability differed over the lactation and was lowest at the beginning (0.098) and higher at the end of lactation (0.138 to 0.151). Genetic correlations between daily SCS were high for adjacent tests (nearly 1) and low between the beginning and the end of lactation. The estimated environmental correlations were lower than the genetic correlations, but the trends were similar. Based on test-day records, the accuracy of genetic evaluations for SCC should be improved when the variation in heritabilities and correlations are taking into account.

Componentes de variância e parâmetros genéticos em uma população multirracial Nelore-Angus sob enfoque Bayesiano

Os objetivos neste estudo foram utilizar um modelo animal multirracial para verificar a presença de heterogeneidade de variância genética entre as raças Angus e Nelore, avaliar a importância da variância devida à segregação entre essas duas raças e estimar os efeitos genéticos aditivos de raça, dominância e epistasia aditiva × aditiva. Foram utilizados neste estudo 4.016 registros de ganho de peso pós-desmame do rebanho de formação da raça Brangus-Ibagé da Embrapa Pecuária Sul, analisados por três modelos distintos: modelo animal multirracial com segregação, modelo animal multirracial sem segregação; e modelo animal tradicional. A heterose reduziu substancialmente em cruzamentos avançados. A variância genética média a posteriori da raça Angus (189 ± 26 kg²) foi maior que o dobro da obtida para a raça Nelore (82 ± 23 kg²) e a variância da segregação entre essas raças foi de 11 ± 5 kg². A alteração das estimativas das variâncias genéticas raciais foi insignificante quando a variância da segregação foi fixada em zero. Critérios bayesianos de escolha apontam o modelo multirracial sem segregação entre raças como uma alternativa parcimoniosa adequada para avaliação genética dessa população.