A genetic evaluation of productive herd life in dairy cattle

English: The length of productive life is of major economic importance in dairy cattle production. Simple breeding objectives such as selection for increased production in dairy cattle have led to a significant decline in fitness traits. A multi-purpose breeding objective that includes other traits such as length of productive life should be considered. Herd life reflects the ability of a cow to avoid being culled for low production, low fertility, or illness. Herd life can be used in breeding programs if genetic parameters are known. The objectives of the study were to: (1) estimate genetic parameters for functional herd life for the South African Jersey breed using a multiple trait linear model, (2) develop a prototype breeding value for functional herd life for the South African Jersey breed, (3) estimate genetic relationships between functional herd life and conformation traits in the South African Jersey breed and (4) assess inbreeding depression for functional herd life in the South African Jersey breed based on level and rate of inbreeding. A measure of herd life called functional herd life was considered in the current study. Functional herd life refers to herd life adjusted for milk production in the first lactation. In this study functional herd life was defined as survival in each of the first three lactations. Functional herd life was denoted by a 1 if a cow survived and 0 otherwise. Analyses to estimate genetic parameters for functional herd life were carried out as follows. Data and pedigree records on purebred Jersey cows that participated in National Milk Recording and Improvement Scheme were analyzed. Data before editing comprised test-day and lactation yields on milk, fat and protein yields from 252 629 Jersey cows born between 1968 and 2005. After editing, 181 269 cow records from 636 herds recorded over 16 years were available for analysis. Estimates of genetic parameters for herd life were obtained using REML procedures fitting a multiple-trait
Afrikaans: Die produktiewe leeftyd van melkkoeie is van groot ekonomiese belang in melkbeesproduksiestelsels. Eenvoudige teeltdoelwitte, soos seleksie vir verhoogde produksie in melkbeeste, het tot ‘n betekenisvolle afname in fiksheidseienskappe gelei. ‘n Veeldoelige teeltdoelwit, wat ander eienskappe soos die lengte van produktiewe lewe insluit, behoort oorweeg te word. Kuddeleeftyd weerspieël die vermoë van koeie om nie weens lae melkproduksie, lae vrugbaarheid of siekte uitgeskot te word nie. Kuddeleeftyd kan, indien die genetiese parameters bekend is, in teeltprogramme gebruik word. Die doelwitte van die studie was om: (1) genetiese parameters vir funksionele kuddeleeftyd vir Suid-Afrikaanse Jerseys te beraam, deur van ‘n meervoudige-eienskap-liniêre model gebruik te maak, (2) ‘n prototipe teeltwaarde vir funksionele kuddeleeftyd vir Suid-Afrikaanse Jerseys te ontwikkel, (3) die genetiese verwantskappe tussen funksionele kuddeleeftyd en bouvormeienskappe vir Suid- Afrikaanse Jerseys te bepaal en (4) die afname in funksionele kuddeleeftyd in die Suid- Afrikaanse Jerseys populasie is gebaseer op die vlak- en tempo van inteling. In die huidige studie is kuddeleeftyd beskryf as funksionele kuddeleeftyd. Funksionele kuddeleeftyd verwys na kuddeleeftyd wat vir eerste laktasiemelkproduksie aangepas is. In hierdie studie is funksionele kuddeleeftyd gedefinieer as oorlewing gedurende elkeen van die eerste drie laktasies. Funksionele kuddeleeftyd is met ‘n 1 aangedui indien ‘n koei die laktasie oorleef het en met ‘n 0 (nul) indien nie. Om die genetiese paramaters vir funksionele kuddeleeftyd te beraam, is die beramings as volg uitgevoer: Die melkproduksie- en stamboomrekords van suiwergeteelde Jerseykoeie wat aan die Nasionale Melkaantekening en Verbeteringskema deelgeneem het, is in die analise gebruik. Voor die redigering van die data, het dit bestaan uit die toetsdag- en laktasierekords vir melk-, vet- en proteïenproduksie van 252 629 Jersey koeie wat tussen 1968 en 20
Agricultural Research Council
National Research Foundation (NRF)
South African Jersey Breed Society