Inbreeding

Extinction of a breed is the inevitable destination of an inbreeding blind alley. Some  geneticists believe that commercial Holstein farmers  will, like the pig industry,  be cross breeding within 10-20 years.

The average 5% inbred US cow loses an estimated US$72 - 45 and 75 days herd life

Each 1% inbreeding cuts  Lifetime Profit (LP)  by 1US$24 - 15, yield by 30Kg a lactation & survival (PL) by 13 days. Thats for starters before any increased lethal or debilitating recessive genes (BLAD, Factor X, DUMPS, Bull Dog, Mule Foot etc) are considered.

Inbred bulls mated to unrelated cows cancels out previous inbreeding. BUT the average US cow is already inbred at the 5% level. 

Despite the UK's relatively late deployment of N. American genetics, the black and white breed is predominantly Holstein via one country or another's N. American derived sires. The diversity of the breed is shrinking at an unprecedented rate.

ADVICE

Set avoidance of inbreeding as a first priority over any other breeding decision

Widening selection of breeding companies will help maintain genetic progress and minimise inbreeding. 

As the UK Holstein herd inevitably becomes more inbred,  mating decisions will have to tolerate a certain level of inbreeding and any predicted financial loss weighed against genetic gain.  

Without breeding software, good records going back to the dam's grand sire are essential to minimise inbreeding below 3% ( Grandson x Granddaughter ). This is quite easy to do for the 150 cow herd, larger herds need DIY software eg RedBook . or an independent mating service such as Selectabull

Mating software should be set for a maximum inbreeding level of 3% (derived from a minimum 3 generation pedigree) and selection of sires should be from all companies.  In countries that have been US derived Holstein for many years - eg Italy, France, Holland, inbreeding levels are similar to if not higher than the US and Canada. A 3% inbreeding target will be difficult to achieve
 
A breeding companies strategy for sire selection is very successfully focused by the Animal Model.   This model considers all a sire's recorded relatives in estimating a PTA (Predicted Transmitting Ability) prior to a 1st Lactation widespread proof. This is backed up with genetic testing for productive markers and lethal recessive genes.  The Animal Model's weakness, if there is one, is that it concentrates attention on close relatives thus decreasing diversity.  Diversity is further reduced by concentrating on first crop daughter tests.  Sometimes it is not until the second calving results appear that we truly know a sire's worth. Several potential sires of sons have been overlooked in the race for the commercially important first crop tests. 


 

 

Consequences of Inbreeding in the US Herd

Relatives at Mating   Milk1 Fat1 Pro1 SCS2* Mor* PL2 Lifetime Loss 1
Coefficient of Inbreeding  % Kg Kg Kg Score % Days $
1 30 1 1 0 2 13 24 15
Suggested Maximum Level 2 59 2 2 0.01 4 26 48 30
Grandson x Granddaughter 3 89 3 3 0.01 6 39 72 45
4 119 4 4 0.02 8 52 96 60
Current US  Inbreeding 5 148 5 5 0.02 10 66 120 75
Son x Granddaughter 6.25 178 6 6 0.02 12 79 144 90
Grandson x Daughter 7 207 8 7 0.03 14 92 168 105
8 237 9 8 0.03 8 105 192 120
9 267 10 9 0.04 18 118 192 135
10 296 11 10 0.04 20 131 216 150
11 326 12 11 0.04 22 144 240 165
Son x Daughter 12.5 356 13 12 0.05 24 157 288 180
1/2 brother x 1/2 sister (1/2 sibs) 13 385 14 13 0.05 26 170 312 195
14 415 15 14 0.06 28 183 336 210
15 445 16 15 0.06 30 197 360 225
Sire x Daughter 25 741 27 24 0.1 50 328 600 375
Son x Mother (Dam)
Brother x Sister (full sibs)

Notes:  Surprisingly in Smith et al's  2,600,000 cow study observed a negligible impact on Somatic Cell Score.  Effects on fertility however are more pronounced ie one days loss in calving interval for every 1% level of inbreeding.
*SCS = Somatic (Mastitis) Cell Score on a range of 0-4
*Mor = is the percentage increase over average expected herd mortality
*PL    = Productive Life in days

Advanced Technical Reading

1 Wiggans et al. JDS 78:1584-1590 
2 Smith et el. JDS 80 (Suppl. 1):226 (Abstr.) 
3 Hansen, L. '99 in proc. WCDS


Extinction is when Montbeillard, Normande, Friesian, Brown Swiss, or Swedish Red, become sires of Holstein sons. Some workers (3) believe this will happen within 10-20 years.  Cross breeding is an emerging reality for different reasons in true milk from grass situations.  Is it possible to imagine, rather like the pig industry, nucleus herds maintaining pure inbred lines which are then cross bred to provide sires or indeed embryo's to the commercial producer?

Extinction can be delayed by the individual herd owner focusing on individual matings which as a first priority avoid inbreeding.  This demands independent mating programs which cover a least 3 pedigrees, and limit inbreeding to a maximum 3%

Extinction maybe avoided if the industry as a whole is given clear messages about what needs to be done and the tools to do the job.