Inbreeding depression for global and partial economic indexes, production, type, and functional traits

peer reviewedThe objective of this research was to examine the effects of inbreeding in the population of Holstein cattle in the Walloon region of Belgium. The effects of inbreeding on the global economic index and its components were studied by using data from the genetic evaluations of February 2004 for production, somatic cell score (SCS), computed from somatic cell counts and type. Inbreeding coefficients for 956,516 animals were computed using a method that allows assigning an inbreeding coefficient to individuals without known parents. These coefficients were equal to the mean inbreeding coefficient of contemporary individuals with known parents. The significance of inbreeding effects on the different evaluated traits and on the different indexes were tested using a t-test comparing estimated standard errors and effects. The inbreeding effect was significantly different from zero for the vast majority of evaluated traits and for all of the indexes. Inbreeding had the greatest deleterious effects on production traits. Inbreeding decreased yield of milk, fat, and protein during a lactation by 19.68, 0.96, and 0.69 kg, respectively, per each 1% increase in inbreeding. The regression coefficient of SCS per 1% increase in inbreeding was +0.005 SCS units. The inbreeding depression was thus relatively low for SCS, but inbred animals had higher SCS than non-inbred animals, indicating that inbred animals would be slightly more sensitive to mastitis than non-inbred animals. Estimates of inbreeding effects on evaluated type traits per 1% increase were small. The most strongly affected type traits were chest width, rear leg, and overall development on a standardized scale. For several type traits, particularly traits linked to the udder, the estimates suggested a favorable effect of inbreeding. The global economic index was depressed by around 6.13 Euro of lifetime profit per 1% increase in inbreeding for the Holstein animals in the Walloon region of Belgium

Linear and curvilinear effects of inbreeding on production traits for walloon Holstein cows

The nonlinear effects of inbreeding were studied by comparing linear and curvilinear regression models of phenotypic performances on inbreeding coefficients for production traits (milk, fat, and protein yields) of Holstein cows in their first lactation. Three different regression models (linear, quadratic, and cubic) were introduced separately into a single-trait, single-lactation, random regression test-day model. The significance of the different regression coefficients was studied based on a t-test after estimation of error variances and covariances associated with the different regression coefficients. All of the tested regression coefficients were significantly different from 0. The traditional regression coefficients of milk, fat, and protein yields on inbreeding were, respectively, -22.10, -1.10, and -0.72 kg for Holstein cows in their first lactation. However, the estimates of 305-d production losses for various classes of animals based on inbreeding coefficients showed that the effect of inbreeding was not a linear function of the percentage of inbreeding. The 305-d milk yield loss profiles attributable to inbreeding, obtained by the various regression models, were different. However, for inbreeding coefficients between 0 and 10%, these differences were small

Development of a genomic evaluation for milk production for a local bovine breed

DairySN

Understanding and utilizing genetic diversity in Dual-Purpose Blue: genome‐wide association for type traits

peer reviewedDual-Purpose Blue in Belgium and northern France is a local breed that is currently in the focus in order to understand its genetic distinctiveness and its use for local products. Its genomic evaluation systems are evolving, and its specific genetic distinctness was here studied for type traits. Results showed that throughout the 23 traits, there were two distinguishable genomic regions (BTA2 and BTA26) where BTA26 was associated with development traits and BTA2 was associated with muscularity traits, but also with associated traits as overall rump, udder depth, overall udder, and rear udder. Given these results future genomic evaluation systems should consider the segregating MSTN (myostatin), which is located on BTA2

Genetic parameters for direct and maternal calving ease in Walloon dairy cattle based on linear and threshold models

Calving ease scores from Holstein dairy cattle in the Walloon Region of Belgium were analysed using univariate linear and threshold animal models. Variance components and derived genetic parameters were estimated from a dataset including 33,155 calving records. Included in the models were season, herd and sex of calf age of dam classes group of calvings interaction as fixed effects, herd year of calving, maternal permanent environment and animal direct and maternal additive genetic as random effects. Models were fitted with the genetic correlation between direct and maternal additive genetic effects either estimated or constrained to zero. Direct heritability for calving ease was about 8% with linear models and about 12% with threshold models. Maternal heritabilities were about 2% and 4%, respectively. Genetic correlation between direct and maternal additive effects was found to be not significantly different from zero. Models were compared in terms of goodness of fit and predictive ability. Criteria of comparison such as mean squared error, correlation between observed and predicted calving ease scores as well as between estimated breeding values were estimated from 85,118 calving records. The results provided few differences between linear and threshold models even though correlations between estimated breeding values from subsets of data for sires with progeny from linear model were 17% and 23 % greater for direct and maternal genetic effects, respectively, than from threshold model. For the purpose of genetic evaluation for calving ease in Walloon Holstein dairy cattle, the linear animal model without covariance between direct and maternal additive effects was found to be the best choice

Relationship between proxies of energy states and nitrogen use efficiency for Holstein cows in early lactation

peer reviewedThe purposes of this study were to estimate the genetic parameters of the energy status indicator (C18:1 cis-9) of Holstein cows in early lactation and its relationship with nitrogen use efficiency (NUE) (predicted NUE and milk urea concentration). After editing, the data included 143,517 records within 5 to 50 days in milk from 52,198 cows, and 3,546 animals in the pedigree with 28,427 SNPs. Two multiple-trait repeatability models were used in this study. In early lactation, the average C18:1 cis-9 was gradually decreasing and was highest in May. The heritabilities of C18:1 cis-9 for primiparous and multiparous cows were 0.12 and 0.09, respectively. The C18:1 cis-9 had positive genetic correlations with predicted NUE (from 0.28 to 0.67), and weak genetic correlations with milk yield, milk urea concentration (from-0.15 to 0.14). This study suggests that breeding for NUE alone may enhance energy troubles in early lactation

LA RADIOTHÉRAPIE DANS LE CANCER DU RECTUM : quand, comment et pourquoi ?

peer reviewedDepuis plusieurs décades, la radiothérapie préopéra - toire ou postopératoire joue un rôle important dans le contrôle local de l’adénocarcinome du rectum. Cette dernière décennie, avec la systématisation de la chirurgie d’exérèse en totalité du mésorectum (TME), le profil de récidive locale du cancer du rectum a été fortement modifié. Dans un tel contexte, la place de la radiothérapie doit être réévaluée en tenant compte de ces modifications. Dans cet article, nous proposons de faire la revue des différentes grandes études concernant les techniques et les indications d’un traitement de radiothérapie pré- ou post opératoire dans le contexte d’une chirurgie rectale TME

Genome-wide association study for selected cheese-making properties in Dual-Purpose Belgian Blue cows

peer reviewedThis study aimed to estimate genetic parameters and identify genomic region(s) associated with selected cheese-making properties (CMP) in Dual-Purpose Belgian Blue (DPBB) cows. Edited data were 46,301 test-day records of milk yield, fat percentage, protein percentage, casein percentage, milk calcium content (CC), coagulation time (CT), curd firmness after 30 min from rennet addition (a30), and milk titratable acidity (MTA) collected from 2014 to 2020 on 4,077 first-parity (26,027 test-day records), and 3,258 secondparity DPBB cows (20,274 test-day records) distributed in 124 herds in the Walloon Region of Belgium. Data of 28,266 SNP, located on 29 Bos taurus autosomes (BTA) of 1,699 animals were used. Random regression test-day models were used to estimate genetic parameters through the Bayesian Gibbs sampling method. The SNP solutions were estimated using a single-step genomic BLUP approach. The proportion of the total additive genetic variance explained by windows of 25 consecutive SNPs (with an average size of ~2 Mb) was calculated, and regions accounting for at least 1.0% of the total additive genetic variance were used to search for candidate genes. Heritability estimates for the included CMP ranged from 0.19 (CC) to 0.50 (MTA), and 0.24 (CC) to 0.41 (MTA) in the first and second parity, respectively. The genetic correlation estimated between CT and a30 varied from −0.61 to −0.41 and from −0.55 to −0.38 in the first and second lactations, respectively. Negative genetic correlations were found between CT and milk yield and composition, while those estimated between curd firmness and milk composition were positive. Genome-wide association analyses results identified 4 genomic regions (BTA1, BTA3, BTA7, and BTA11) associated with the considered CMP. The identified genomic regions showed contrasting results between parities and among the different stages of each parity. It suggests that different sets of candidate genes underlie the phenotypic expression of the considered CMP between parities and lactation stages of each parity. The findings of this study can be used for future implementation and use of genomic evaluation to improve the cheese-making traits in DPBB cows

Genome-wide association study for mid-infrared methane predictions in Walloon dairy cows

peer reviewedThis study aimed to identify genomic regions associated with two mid infrared-based CH4 traits [predicted daily CH4 emission (PME, g/d), and log-transformed predicted CH4 intensity (LMI)] in Walloon dairy cows. The data consisted of 1,529,282 test-day records from 229,465 cows distributed in 1,530 herds collected from 2006 to 2021. Random regression test-day models were used to estimate variance components. The proportion of genetic variance explained by windows of 50 consecutive SNPs was calculated and regions accounting for at least 1.0% of the total genetic variance were identified. Mean (SD) daily h2 estimated for PME and LMI were 0.14 (0.05) and 0.24 (0.05), respectively. Two regions on BTA14 (positions 1.86 to 2.12, and 1.48 to 1.68 Mb) were associated with both PME and LMI. A region between 144.38 to 144.46 Mb on BTA1 was associated with PME; and the region between 2.68 and 2.94 Mb on BTA14 was associated with LMI. Results showed potential for genome-enhanced advisory systems to reduce methane emissions