Abstract
The use of genetic evaluations in the Water Buffalo by means of a Best Linear Unbiased Prediction (BLUP) animal model has been increased over the last two-decades across several countries. However, natural mating is still a common reproductive strategy that can increase the proportion of missing pedigree information. The inclusion of genetic groups in variance component (VC) and breeding value (EBV) estimation is a possible solution. The aim of this study was to evaluate two different genetic grouping strategies and their effects on VC and EBV for composite (n = 5) and linear (n = 10) type traits in the Italian Mediterranean Buffalo (IMB) population. Type traits data from 7,714 buffalo cows plus a pedigree file including 18,831 individuals were provided by the Italian National Association of Buffalo Breeders. VCs and EBVs were estimated for each trait fitting a single-trait animal model and using the official DNA-verified pedigree. Successively, EBVs were re-estimated using modified pedigrees with two different proportion of missing genealogies (30 or 60% of buffalo with records), and two different grouping strategies, year of birth (Y30/Y60) or genetic clustering (GC30, GC60). The different set of VCs, estimated EBVs and their standard errors were compared with the results obtained using the original pedigree. Results were also compared in terms of efficiency of selection. Differences among VCs varied according to the trait and the scenario considered. The largest effect was observed for two traits, udder teat and body depth in the GC60 genetic cluster, whose heritability decreased by −0.07 and increased by +0.04, respectively. Considering buffalo cows with record, the average correlation across traits between official EBVs and EBVs from different scenarios was 0.91, 0.88, 0.84, and 0.79 for Y30, CG30, Y60, and CG60, respectively. In bulls the correlations between EBVs ranged from 0.90 for fore udder attachment and udder depth to 0.96 for stature and body length in the GC30 scenario and from 0.75 for udder depth to 0.90 for stature in the GC60 scenario. When a variable proportion of missing pedigree is present using the appropriate strategy to define genetic groups and including them in VC and EBV is a worth-while and low-demanding solution.
Highlights
The Water Buffalo (Bubalus bubalis) is a large bovid mainly distributed in the Asian continent where the 97% of its world population is concentrated [Food and Agriculture Organization (FAO), 2020]
The estimated genetic variance was highest for five linear traits (STAT, fore udder attachment (FUA), rear udder width (RUW), udder depth (UD), and teat length (TL)), intermediate for body depth (BD), body length (BL), foot angle (FA), and teat placement (TP), while the lowest were for composite traits and body condition score (BCS)
Italian Mediterranean Buffalo (IMB) is facing a situation where phenotypic data are available for many animals, but some animals lack complete genealogical data
Summary
The Water Buffalo (Bubalus bubalis) is a large bovid mainly distributed in the Asian continent where the 97% of its world population is concentrated [Food and Agriculture Organization (FAO), 2020]. The rest of the water buffalo world population (3%) is raised in the Mediterranean area historically characterized by the same optimal rearing conditions. In 2019, 34,990 lactating buffaloes have been registered to the official herd book. Thanks to the physical-chemical properties of its milk—high concentration in protein and fat (FC ∼ 8%) and favorable coagulation (Costa et al, 2020b)—the main zootechnical interest of the Italian Mediterranean Buffalo (IMB) is the production of the iconic traditional dairy products like the Mozzarella di Bufala Campana (Boselli et al, 2020), which has a great economic impact on the Italian food industry (ISMEA, 2020). The economic interest in this specie makes it necessary to develop new innovative tools to improve the breeding process
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