Effects of inbreeding on production and survival in Holsteins

Responses of registered Holstein cows to various levels of inbreeding were examined with pedigree data supplied by the Holstein Association USA and te st-day production data from 1970 through 1998 obtained from the Animal Bree ding Center at Cornell University. Rate of increase in level of inbreeding has been accelerating over time, making it more difficult for producers to make matings that avoid the potentially deleterious effects of inbreeding. Milk production losses per lactation caused by inbreeding were generally 35 kg per percentage inbreeding level >0.01 but increased to 55 kg per percen tage inbreeding level from 0.07 to 0.10. Somatic cell score was not affecte d by level of inbreeding. Inbreeding had the greatest effect on production at ages <22 mo and early in lactation. Early onset of the deleterious effec ts of inbreeding resulted in larger net present value losses than when effe cts of inbreeding occurred later. Losses were likely enhanced due to the ne ed to freshen animals as early as possible to maximize net present value re turns. Survival decreased as level of inbreeding increased and was likely t o have a greater negative impact on the financial health of the dairy enter prise than production losses.