Effect of lactation length adjustment procedures on genetic parameter estimates for buffalo milk yield

The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank.

Estudo genético quantitativo da qualidade da carcaça e da carne e suas associações com as características de avaliação visual na raça Nelore

Brazil is the largest beef exporter and the second beef producer in the world. However, the Brazilian cattle composite is mostly Bos indicus, which produces meat with less quality than Bos taurus. Despite the importance of carcass (CARC) and meat quality (MQ) traits for the beef production cycle, its selection is not applied. Genetic evaluation after harvest is expensive because it requires a long period of time for the trait to be evaluated and consequently, also requires a progeny test. Therefore, the indirect selection through the traits which are commonly applied on breeding programs is feasible. Within this context, the visual evaluation using scores has been used on breeding programs, aiming to improve the carcass traits. The objective of the present study was to evaluate the genetic parameters of CARC and MQ, as well as their genetic associations with visual scores in Nellore cattle. For CARC and MQ traits were used only males, from animals that were born between 2008 and 2010, raised on grazing system and kept around 90 days in feed lot system for finishing. Records of 36,600, 36,550, 36,550, 1,442, 1,441, 1,435, 1,533, 1,535, 1,535, 1,534, 1,533 and 1,522 for yearling conformation (C), yearling finishing precocity (P), yearling muscling (M), rib eye area (REA), hot carcass weight (HCW), fat thickness (FT), Warner - Bratzler shear force (SF), marbling score (MS), lightness (L*), redness (a*), yellowness (b*) and intramuscular lipid (IL), respectively, were used. The (co)variance components were estimated by the restricted maximum likelihood method using tri and multitrait animal model. For the visual scores the model included the genetic additive and residual random effects, the contemporary group (CG) as a fixed effect and age of the animal (linear and quadratic) as covariate. For CARC and MQ the model included the genetic additive effect and residual effect as random effects, and ...O Brasil destaca-se mundialmente como o maior exportador e o segundo maior produtor de carne bovina. Entretanto, o rebanho brasileiro é composto majoritariamente por animais de raças Zebuínas, que produzem carnes de menor qualidade sensorial, quando comparados com os animais de raças Taurinas. Apesar da importância dessas características para a cadeia produtiva, a seleção ainda é pouco praticada, uma vez que as mesmas são difíceis de serem medidas, dependendo do abate dos animais e, consequentemente, de realização de testes de progênie para avaliação dos touros, atrasando o processo seletivo. Desta forma, a seleção indireta por meio de características comumente empregadas nos programas de seleção apresenta-se como alternativa. Neste contexto, as avaliações visuais por escorestêm sido incluídas nos programas de melhoramento genético de bovinos de corte, com o objetivo de melhorar características de carcaça. Objetivou-se com o presente trabalho estudar os parâmetros genéticos para as características da carcaça e carne, bem como suas relações com mensurações de avaliação visual. Os dados são provenientes de animais da raça Nelore, machos e fêmeas, que pertencem a dois programas de melhoramento genético – DeltaGen e Paint. Os animais com registros de dados fenotípicos para as características da carcaça e carne foram somente machos, nascidos entre 2008 e 2010, criados em sistemas de pastejo e confinados apenas na fase de terminação, por período ao redor de 90 dias. Foram utilizados registros de 36.660, 36.550, 36.550 e 36.550 animais machos e fêmeas, respectivamente, para peso à desmama (PD), conformação ao sobreano (C), precocidade ao sobreano (P) e musculatura ao sobreano (M) e, para as características da carcaça e da carne foram utilizados 1.442, 1.441, 1.435, 1.533, 1.535, 1.535, 1.534, 1.533 e 1.522 para área de olho de lombo (AOL), peso ..

Estimativas de parâmetros genéticos de características de carcaça, medidas por ultrassonografia, e suas relações com escores visuais na raça Nelore

O objetivo deste trabalho foi estudar a variabilidade genética das características de carcaça obtidas por ultrassom e de escores visuais, bem como suas associações genéticas em bovinos da raça Nelore. Foram utilizados registros de 13.285, 13.061, 12.811, 3.484, 3.484, 3.483 e 3.303 animais, para área de olho de lombo (AOL), espessura de gordura subcutânea (EG), espessura de gordura subcutânea na garupa (EGP8), estrutura (E), precocidade (P), musculosidade (M) e umbigo (U), respectivamente. Considerou-se nas análises como o efeito fixo o grupo de contemporâneos, o efeito aleatório genético aditivo direto, além das covariáveis idade da vaca ao parto (efeitos linear e quadrático) e idade do animal (efeitos linear e quadrático), dependendo da característica. Foi utilizado como âncora nas análises 46.157 observações de peso padronizado aos 120 dias (P120). As estimativas dos componentes de (co)variâncias foram obtidas pelo método da máxima verossimilhança restrita aplicando um modelo animal em análise multicaracterística. As estimativas de herdabilidade para as características AOL, EG, EGP8, E, P, M e U foram de 0,33 ± 0,028, 0,24 ± 0,024, 0,28 ± 0,027, 0,24 ± 0,039, 0,38 ± 0,054, 0,29 ± 0,048 e 0,38 ± 0,063, respectivamente. As correlações genéticas entre os escores visuais e a área de olho de lombo foram positivas e moderadas, variando de 0,37 a 0,44. Estes valores indicam que a utilização da AOL como critério de seleção poderá produzir animais com maiores escores para essas características. As correlações entre P e M com as espessuras de gordura (EG e EGP8) apresentaram resultado semelhante. Entretanto, as correlações genéticas entre as espessuras de gordura e E variaram de -0,02 a 0,12. As correlações genéticas entre umbigo e estrutura, e umbigo e as características de carcaça indicam que as mesmas não são geneticamente associadas...The objective of this work was to study the genetic variability for carcass traits obtained by ultrasound and visual scores traits, and their genetic relationship in Nelore cattle. A total of 13,285; 13,061; 12,811; 3,484; 3,484; 3,483 and 3,303 records of longissimus muscle area (LMA), backfat thickness (BF), obtained between the 12th and 13th ribs, rump fat thickness (RF), body structure score (E), precocity score (P), muscle score (M) and navel score (U) were utilized. The model included the fixed effect of contemporary group, the age of dam at calving and age of animal as covariable (linear and quadratic effects). The direct additive genetic effect was included as random effect in the model. The (co)variance components and genetic parameters estimates were obtained by the restricted maximum likelihood method, applying an animal model in multi-trait analyses. The heritability estimates for LMA, BF, RF, E, P, M and U were 0.33 ± 0.028, 0.24 ± 0.024, 0.28 ± 0.027, 0.24 ± 0.039, 0.38 ± 0.054, 0.29 ± 0.048 and 0.38 ± 0.063, respectively. The genetic correlation estimates between LMA with visual scores were positive and moderate, varying from 0.37 to 0.44. The genetic correlation estimates between backfat and rump fat with visual scores shown the same trend. However, the genetic correlation estimates between E with BF and RF were low, -0.02 to 0.12, respectively. These results shown that applying LMA as selection criteria will increase the visual scores. The genetic correlation estimates between U and E, and between U and carcass traits pointed out a weak relationship between these traits. Selection to improved carcass traits and E would not affect the navel score. Visual scores would not replace the carcass traits as selection criteria to improve the meat and carcass qualityCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Genomic analysis of stayability in Nellore cattle.

Stayability, which can be defined as the probability of a cow calving at a certain age when given the opportunity, is an important reproductive trait in beef cattle because it is directly related to herd profitability. The objective of this study was to estimate genetic parameters and to identify possible genomic regions associated with the phenotypic expression of stayability in Nellore cows. The variance components were estimated by Bayesian inference using a threshold animal model that included the systematic effects of contemporary group and sexual precocity and the random effects of animal and residual. The SNP effects were estimated by the single-step genomic BLUP method using information of 2,838 animals (2,020 females and 930 sires) genotyped with the Illumina High-Density BeadChip Array (San Diego, CA, USA). The variance explained by windows formed by 200 consecutive SNPs was used to identify genomic regions of largest effect on the expression of stayability. The heritability was 0.11 ± 0.01 when A matrix (pedigree) was used and 0.14 ± 0.01 when H matrix (relationship matrix that combines pedigree information and SNP data) was used. A total of 147 candidate genes for stayability were identified on chromosomes 1, 2, 5, 6, 9 and 20 and on the X chromosome. New candidate regions for stayability were detected, most of them related to reproductive, immunological and central nervous system functions

Descriptive statistics of the dataset.

<p>Descriptive statistics of the dataset.</p

Manhattan plot of the variance explained by windows formed by 200 consecutive SNPs for stayability in Nellore cattle.

<p>Manhattan plot of the variance explained by windows formed by 200 consecutive SNPs for stayability in Nellore cattle.</p

Chromosome (Chr), position, candidate genes and proportion of variance (Var) explained by the top 10 SNP windows with higher effects for stayability.

<p>Chromosome (Chr), position, candidate genes and proportion of variance (Var) explained by the top 10 SNP windows with higher effects for stayability.</p

Gene network linked to biological process related to stayability in Nellore cattle.

<p>The size of nodes represents the statistical significance of the terms. (P-value adjusted to Bonferroni statistics).</p