£PLI – Profitable Lifetime Index
£PLI – Profitable Lifetime Index
Replacement heifers for the 180 cow CAFRE Dairy Herd are bred from sires selected initially on £PLI (Profitable Lifetime Index) and then on several individual genetic index traits including milk protein %, milk fat %, fertility index, lifespan and somatic cell count (SCC). The aim of the CAFRE dairy herd breeding programme is to improve the overall genetic merit of the herd through both sire and female selection. All replacements have been genotyped since 2017. The genetic merit of the CAFRE Dairy Herd and the annual sire selection criteria are published on the CAFRE website to demonstrate to students and farmers the benefits of genetic improvement and the use of breeding technologies such as the increasing number of new genetic indices which have been added to £PLI in recent years.
£PLI is a ‘within breed’ sire ranking index. The £PLI value represents the additional profit a high £PLI bull is expected to return from each of its milking daughters over her lifetime compared with an average bull of £0 PLI. The £PLI reflects the latest UK market and farming conditions. The £PLI is a weighted economic index with different weights given to a wide range of sub-indices or Predicted Transmitting Abilities (PTAs) for genetic parameters, ranging from milk yield and milk quality through to lifespan, fertility, mastitis and TB resistance. The Agricultural and Horticultural Development Board (AHDB) is the UK organisation responsible for maintaining and updating £PLI three times each year.
More information on £PLI and important sub-indexes from which £PLI is derived can be found on the AHDB website through clicking on each parameter below:
Profitable Lifetime Index (£PLI)
Sire selection within the CAFRE Dairy Herd
The starting point for sire selection each year is to review the Herd Genetic Report. This report is available to dairy farmers that milk record and have sire and dam information uploaded. Herd Genetic Reports allow farmers to evaluate the genetic potential of their dairy herd through reviewing the genetic merit for production and health traits for either individual animals or lactation number groups. Analysis of the Herd Genetic Report will indicate if the key breeding indices are improving and/or whether more selection pressure needs to be applied to particular breeding sub-indices. Following a review of the Herd Genetic Report, selection criteria are set for £PLI and for several breeding sub-indices including calving ease, fertility, lifespan, milk protein % SCC, enviro-cow and feed advantage. The list of UK available Holstein sires and available Holstein genomic young sires is downloaded from the AHDB website.
The spreadsheets are screened initially by £PLI and then for each of the breeding sub-indices to determine which sires meet the selection criteria. A shortlist is then drawn up of potential sires for milking cows and sires for maiden heifers that are available with sexed semen. The bull linear traits are also assessed with emphasis on udders, legs/feet, teat length, size, locomotion and as result some bulls will be deselected from the initial list. The availability of semen from sires on the shortlist of sires is then checked with the semen supply companies. The shortlist of sires is also run through the AHDB inbreeding checker to ensure that the sires chosen will not increase inbreeding.
More recently heifer recessive genes (haploids) have been determined for each animal. This has added greatly to bull selection to minimise the likelihood of replacement heifers having a deleterious genetic condition that may be fatal or decrease health/fertility.
The AHDB inbreeding checker has proven to be a very useful tool to check the inbreeding percentage of any potential mating, (once females available to breed from have been selected and sire selection has been made). The sire with the lowest inbreeding percent from a potential mating is selected as number one choice and the next lowest as number 2 choice if required. Any mating with an inbreeding percentage greater than 10 is excluding from the breeding program.
Within the CAFRE Dairy Herd, analysis of breeding records across several breeding seasons has demonstrated a positive correlation between sire fertility index on conception rates and calving interval. This analysis carried out several years ago reinforced the benefit of breeding for daughter fertility to the CAFRE dairy team with the result that Fertility Index continues to be a key parameter for selecting sires for replacement breeding replacement heifers on an annual basis. Moving forward, with other sub-indexes being added such as enviro-cow, feed advantage and maintenance, these will help enable a more feed efficient animal to be produced.
Whilst many dairy farmers usually have a purebred herd (often Holstein), but it may not necessarily be pedigree registered, there is interest amongst some farmers in crossbreeding. This can be for a multitude of reasons such as perceived better health and fertility, longer lasting, better cull cow values, better calf prices. A technology investigation on crossbreeding has been undertaken with the report available below. One of the issues with crossbreeding is that it is harder to get PTA figures/genomic data for the crossbred offspring, which could be used to aid breeding decisions.
