27/11/2024
In an exclusive article in this weeks Scottish Farmer, Bernicia Media's Bruce Jobson traces the acceleration of inbreeding coefficients and predicts the level of inbreeding within the Holstein breed will reach 10% by the end of 2025. How did inbreeding get to this level?
INBREEDING
The traditional view held by geneticists remains that inbreeding levels are preferable at a 6% or below threshold. It is at the 6% level and above, geneticists raise concerns inbreeding levels have a detrimental effect on numerous animal health and welfare traits such as fertility; reproduction, disease, longevity and general well-being.
However, letโs back-track 40-years to review the warning signs that have been ignored by the cattle-breeding industry in its never-ending quest for faster generation turnover and ever-increasing genetic advancement. This period also coincided with the AI industry taking greater โcontrolโ over the direction of traditional breeding programmes previously the domain of registered cattle breeders.
Dr John Hinks (Edinburgh) wrote a forward-thinking paper on โCentralised Breeding Schemesโ (to generalise) and proposed a more structured system of sire procurement via use of nucleus herd schemes. Dr Hinksโ paper was followed-up by incorporating the use of embryo transfer technology using multiple ovulation techniques known by the genetic acronym, MOET.
MOET THEORY
Co-author of the MOET theory was Prof. Charlie Smith (Edinburgh and later the University of Guelph, Canada) The MOET theory aimed to reduce sire generation intervals by half, from approximately seven-plus years, the time taken for a bull to be fully randomly progeny-proven through an official testing scheme, based upon daughter performance records against contemporary daughters of other sires.
During this time, unproven young bulls were laid-off at stud for at least five years, in itself, a lengthy and expensive period, until progeny-proven. Selection intensity was generally accepted to be one-in-ten sires (1:10) returning to active service following performance assessments, with the other nine sires discarded.
The MOET theory proposed multiplying male and female progeny from elite females; with the daughterโs performance records being assessed on first lactation records, against other contemporary female sibling groups in the nucleus herd scheme. The male progeny siblings were โprovenโ on the basis of their female sibling performance โ due to close sibling genetic correlation. All animals were under the same environmental and management conditions without preferential treatment.
Male progeny semen was to be distributed through sibling-brother โbull teamsโ - four or five male siblings to reduce โrisk.โ On this basis, genetic performance could be assessed between 36-48 months. In writing the critique on the MOET theory (Jobson 1987) numerous concerns became apparent, including, calculations not carried forward through five generation faster turnover.
The generations were speeded-up and progeny born could be in generation three before generation one was โprogeny-proven.โ This also resulted in increasing inbreeding concerns. Charlie Smith confirmed the MOET critique was correct at the Third World Congress on Genetics at Edinburgh in 1990.
However, Charlie stated the MOET โtheoryโ was in fact an โacademic exerciseโ and had not expected MOET to be developed from an academic theory into practical establishment. Another MOET critique concern; the conclusion after extensive calculations; the sheer cost involved made the programme โfinancially unaffordable.โ
Third World Congress on Genetics Edinburgh 1990
At the Third World Congress on Genetics (Edinburgh 1990) Dr Ted Burnside, Department of Animal Science, University of Guelph, offered prophetic warnings in relation to the increasing level of in-breeding within Holstein cow populations. The esteemed audience of geneticists, leading academics and AI industry representatives were stunned into silence. Almost 35 years later, the concerns expressed by Dr Burnside are stronger than ever.
The average level of inbreeding within the Holstein population in 1970 was recorded at 0.5%. At the time of the MOET theory critique (1987) the level of inbreeding was 2% and when Dr Burnside raised his concerns three-years later at the Third World Congress, inbreeding had risen to 2.5%. Within ten years (2000) the inbreeding rate in the Canadian Holstein population had doubled to 5%.
The 2019 data reveals inbreeding levels at 8.13% for Holsteins and an annual average increase of .25%. With a degree of accuracy, having accurately predicted inbreeding levels (2021) in Holsteins would increase to 8.63% and likewise, Jersey inbreeding levels (2019) increasing to 6.9% (.10% annual increase for 2021) to rank Jersey inbreeding levels of 7.1%.
Over the past 30-40 years, the use of ET technology allied to genetic population changes have helped alter, slow down and increase the level of inbreeding. This has been easier to track through the Canadian one-year rolling base system with the annual average increase in the Canadian population between 1970 -1980 being 0.12%. At that time, there was little genetic influence from US sires and none from Europe.
Hanoverhill Starbuck
From 1980 - 1990 the annual inbreeding rate decreased to 0.07% due to US bloodlines being introduced, and thereby providing an outcross to traditional Canadian bloodlines, allied to the increasing influence of Hanoverhill breeding. From 1990โ2000; the annual trend fluctuated by increasing to 0.27; as the influence of Hanoverhill Starbuck, and his son, Madawaska Aerostar, and his sons, accelerated change. Outcross bloodlines from the US and Europe began to increase in influence and between 2000-2010; the inbreeding rate dropped back to 0.07%.
From 2009, the introduction of genomic technology resulted in the further reduction of the generation interval and the annual rate of inbreeding increased to 0.21%. Other major cow populations accelerated inbreeding rates as international breeding programmes competed more aggressively, using similar bloodlines; ET and Invitro technology allied to genomic sire identification technology.
The collective technology resulted in further increasing inbreeding levels predominantly within the Holstein breed. Having attended conferences in Canada dating back to 1991 on the research and development of genomics โ then known as DNA markers โ one of the proposed emerging benefits of DNA technology was to find genetic โoutliersโ โ both male and female.
The theory being an outlier female, from outside mainstream bloodlines, could be identified as a potential high genetic bullmother. This would result in an outcross mating and reduce inbreeding levels across a broad population. Paradoxically, the result was greater intensive genetic selection of high merit parents and further narrowing of the bloodlines.
There is a misconception the Holstein breed is disadvantaged through inbreeding levels when compared to other breeds but statistics suggest otherwise. Jersey inbreeding levels (2019โ2020 base) increased to 6.9% (.10% annual increase for 2021) to rank 2022 inbreeding levels at 7.1%. Having previously predicted the 2022 inbreeding levels in 2019 (see box) these calculations are close to the official 2022 Canadian figures - with all major dairy breeds identified above the recommended 6% level.
Breed 2022 predicted 2022 Actual Predicted 2025
Ayrshire 6.72% 6.73% 7.33%
Brown Swiss 7.15% 7.09% 7.84%
Guernsey 7.24% 7.50% 8.0%
Holstein 8.63% 8.86% 10.16%
Jersey 7.10% 7.10% 7.7%
Calculating forward to the end of 2025, the Holstein breed will have 10% inbreeding levels or above. Inbreeding depression can result in reduced production; increases reproduction problems, increase susceptibility to disease and can increase metabolic disorders, which all reduce an animalโs utility, profitability and lifespan.
GENOMICS
Breeders often relate to modern Holsteins having the above-mentioned concerns. From a phenotype perspective, due to genomic unproven sires being constantly used on genomic unproven sires; breeders cannot correct negative type and production traits and consider animals are often narrow-chested; lacking in strength throughout, display poor rump-structure and lack vigour. Udders and leg traits concerns are also cited.
Within a 50-year timescale, Holstein inbreeding has increased from 0.5% to 10% or over a tighter 35-year period (1990) of 2% to 10%. This is an alarming rate, due to faster generation turnover and intensive genetic selection, to which sections of the cattle-breeding industry appear oblivious. Some programmes are so far over the genetic horizon, strategic direction and vision has been lost โ and the consequences continue.
There are always individual sire exceptions to the norm, one being show winning specialist, Braedale Goldwyn. Born in 2000, the bullโs inbreeding levels peaked at 16% with a 17% relationship to the Holstein breed. Looking back at some of the famous Canadian Holstein sires, it is possible to track inbreeding levels and percentage relationship to the population.
Roybrook Starlite
One of the most famous Holstein sires of the 1970s was Roybrook Starlite (born 1968) that had an inbreeding rating of 0.93 and 3% population relationship. By the end of the decade, Hanoverhill Starbuck (born 1979) would subsequently emerge as a sire of sons and grandsons, and have an inbreeding rating of 3.79% and 19% relationship.
Starbuckโs greatest son, Madawaska Aerostar (born 1985) would help propel the bloodline forward and offered 7.39% inbreeding ratings and 20% population relationship. Two of Aerostarโs most popular sons were born in 1991, Startmore Rudolph (2.30% and 16% relationship) and Maughlin Storm (1.35% and 17%) These bulls included outcrosses to US bloodlines including Mattador and Valiant son, Hanoverhill Inspiration.
In the modern genomic era, a young โprogeny unprovenโ bull has a genomic index rating equivalent to 30 milking daughters. Therefore, more female progeny โ often thousands of daughters - are born at the start of a young Holstein bullโs AI career; rather than after traditional progeny testing methodology whereby a sire had a first evaluation based upon 70 randomly tested daughters.
Once progeny proven, semen was then released for widespread distribution with the elite bulls achieving production of one-million units and marketed world-wide. With thousands of genomic daughters now being born at the start of an AI career, rather than after progeny-proven, this accelerates inbreeding levels due to faster generation turnover.
Today, there is not 1:10 genetic intensity; in fact, there is not any genetic intensity; with all genomic bulls already assessed as โprovenโ albeit, numerous sires fail to live up to original genomic evaluations. Many sires would not return to โactiveโ service under the previous first-crop evaluation system.
The cattle breeding industry, should consider specific breeding goals and breeding strategy, rather than merely compete in a faster generation genomic race. The one-dimensional approach carries the previously identified โLaws of Unintended Consequencesโ such as further increased levels of inbreeding, allied to numerous animal health and welfare concerns.
HETEROSIS
Identifying specific dams or cow families, identifying selective breeding goals, including a more โbalancedโ approach by using outliers or outcrosses from international cow populations, will result in positive benefits and reduce inbreeding. Rather than turning over faster generation increases โ it is possible to capitalise and deliver advancement by within-breed heterosis effects (hybrid vigour) as in the UK imported cases of Linmack and Adema 88 from Canada and Holland, respectively.
Capitalising on the positive effects of step-by-step heterosis within individual strains (within breed) will result in healthier, longer-lasting, more profitable cattle by specific bloodlines developed for increases in fertility, disease resistance, production traits and conformation.
Additional information drawn from Bruce Jobsonโs Moet Theory Critique (1987) and his paper at the 104th US National Holstein Convention, Minnesota (1989) entitled: โAdvanced Genetic Advancement in Relation to Economic Milk Production by Incorporating Various Strains of Cattle within National and International Breeding Programmes.โ
