Márton Demény

Despite the growing use of k-means clustering in cattle breeding research, its application to weaning performance traits in Limousin young bulls remains limited. This study evaluated the effectiveness of k-means clustering for identifying distinct groups based on age, live weight and morphometric records in a Hungarian Limousin nucleus herd. A total of 146 bulls weaned at an average age of 213 ± 2.03 days and live weight of 263 ± 3.31 kg (mean ± S.E.M.) were analysed. Age, live weight, withers height, rump height, back length, shoulder width, hip width and pin width were evaluated using k-means clustering. The optimal number of clusters was determined using the Elbow method, Average Silhouette Width analysis, the Calinski–Harabasz index, and the Davies–Bouldin index. Three clusters were identified, representing low (213 kg), intermediate (260 kg), and high (309 kg) body size groups. Live weight showed the strongest contribution to clustering (F = 387.3), followed by rump height (F = 85.6) and withers height (F = 82.8). Back length (F = 13.7) and pin width (F = 12.6) contributed the least. The greatest separation was observed between Cluster 1 and Cluster 3 (Euclidean distance = 99.26). Cluster 3 showed the highest within-cluster homogeneity, with no outliers and the lowest dispersion (SD = 10.67). These findings support data-driven phenotypic preselection strategies; however, future research should incorporate additional herds, economically relevant traits, and genomic data to enhance generalisability.

Nowadays, public opinion is determined by economic and environmental considerations, so when selecting beef cattle for breeding, the aim is to achieve the largest possible body size while reducing feed costs and methane emissions. Computer-controlled automatic feeding systems can measure the exact amount of feed consumed by animals, enabling the RFI value to be determined. This value expresses the difference between the amount of feed actually consumed by the animal and the amount expected based on its live weight and body weight gain.In 2024, we studied 29 Blonde d'Aquitaine breeding bulls that were fed using the Vytille system and housed in two pens in Taliándörögd. The animals were divided into four groups based on their RFI values and average daily weight gain, and their production data were analysed using a multivariate generalised linear model (GLM) method.Based on our results, it was not necessary to take pen effect into account, as the husbandry technology was perfectly suited to the purpose. The four groups were sufficient for selection based on feed conversion and daily weight gain. Taking all the measured values into account, the young bulls in the group with favourable RFI and above-average daily weight gain are the most promising.

A testméretek elemzése fontos szerepet játszik mind az élősúly becslés mind pedig a tenyészállat kiválogatás és minősítés szempontjából. Minden olyan módszer mely segíti a korai tenyészállat kiválogatást, nem csak hatékony eszköz a tenyésztői munkában, de költségmegtakarítást is jelent. Jelen tanulmányban egy limousin törzstenyészetből származó összesen 311 (146 bika és 165 üsző) választott borjú testméreteit (marmagasság, farmagasság, háthosszúság, marszélesség, csípőszélesség, ülőgumótávolság) elemezzük (2021 és 2022 év között) döntési fa eljárással. Vizsgálataink során azt találtuk, hogy az életkor és a testméretek között a korrelációs értékek rrang = 0,02-től, rrang = 0,36 -ig változtak (n=311, P≤0,01). Ugyan akkor az élősúly vonatkozásban, ugyan ezek az értékek az alábbiak voltak: rrang = 0,32; rrang = 0,77 (n=311, P≤0,01). Megállapíthatjuk, hogy ebben az életkorban, a választott borjak esetében az egyes testméretek alakulására az élősúly nagyobb befolyással bírt, az életkorhoz képest. Az is megállapítható, hogy a CHAID elemzés alkalmas a testméretek és az élősúly közötti összefüggéseinek feltárására, melynek külön előnye, hogy megjeleníti a homogén csoportok jellemzőit.

The aim of this study was to analyse how body measurements, live weight and age in young Limousin bulls are interrelated, and what ratio of the phenotype variance can be explained by a group of them, so what traits should be considered in early selection. Body measures of 8-9 months old Limousin young bulls (n=610) in two consecutive years from 32 Hungarian farms were registered, and their covariance structure was studied by principal component analysis. Two components were defined, explaining 71.58% of the total variance. The first component was composed of live weight and body measures; the second component contained age. Live weight, withers’ height and hip height measures had highly definitive effect in the first component. Length of back, width at shoulders, and width at hip bone measurements had lower, but still significant effects. Eigenvalue of the first component had been very high, with 58.36% eigenvalue variance. Only effect of age proved to be highly significant in the second component, with an eigenvalue variance 13.22%. As age contributes less, if correction is needed for transforming results of individuals comparable, then it is advised to be based on live weight. Registered body measurements could be considered together in selection decisions, not needless to take all separately.