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Title: TIMELINESS AND EFFECTIVENESS OF PROGENY TESTING THROUGH ARTIFICIAL INSEMINATION

Author
item Norman, H
item Powell, Rex
item Wright, Janice
item SATTLER, C - NAAB

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Artificial insemination has been the technology identified as making the greatest contribution to improving the efficiency of the dairy industry. However, little information is available to document characteristics of the program. Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, i.e. bull age at semen distribution, PT daughter birth, and PT daughter calving by breed for bulls that entered AI service since 1960. Also examined were PT daughter distribution, rate of return of PT bulls to widespread service, and yield and genetic merit of daughters of PT bulls compared to those from proven and natural service bulls. Mean Holstein bull age at semen distribution (16 mo) changed little over time, but SD decreased. Mean Holstein bull age at PT daughter birth and calving declined by 4 mo from the 1960s to the 1990s; SD of means decreased by 3 mo during the period shortening generation interval. Percentage of Holstein herds with PT daughters has increased over time, from 15% in 1965 to 61% in 1998, permitting more bulls to be sampled. Percentage of PT bulls returned to extensive AI service has declined dramatically and is currently about 14% for Holsteins and 20% for the other breeds, indicating returned bulls are more highly selected than in the past. The percentage of milking daughters sired by PT bulls has increased while those sired by natural service bulls has declined. Daughters of AI proven bulls gave from 110 to 180 kg more milk than daughters of PT bulls and 360 to 450 kg more milk than daughters of natural service bulls. More extensive and rapid sampling and increased selection intensity have helped bring genetic gains. Substituting remaining natural service for AI would lead to even bigger genetic gains.

Technical Abstract: Progeny-test (PT) programs of US artificial-insemination (AI) organizations were examined to determine timeliness of sampling, PT daughter distribution, rate of return of PT bulls to widespread service, and merit of PT bulls compared to proven and natural service bulls. Means, standard deviations (SD), and deciles for bull age at semen distribution, PT daughter birth, and PT daughter calving were calculated by breed for bulls that entered AI service since 1960. Mean Holstein bull age at semen distribution (16 mo) changed little over time, but SD decreased from 4.0 to 2.4 mo. Mean Holstein bull age at PT daughter birth and calving declined by 4 mo to 29 mo and 56 mo, respectively; SD of means decreased from 6 to 3 mo. Usually for other breeds, bulls were older at PT daughter birth and calving, and SD of means were larger. Percentage of herds with PT daughters has increased over time. For Holsteins, herds that had usable PT daughters increased from 15% in 1965 to 61% in 1998. Percentage of Holstein PT bulls returned to AI service declined from >40% for bulls with PT entry near 1965 to 14% for bulls with PT entry around 1990; for other breeds, about 20% of recent bulls returned to service. The percentage of milking daughters sired by PT bulls has increased between 1984 and 1998 from 10 to 18%, while those sired by natural service bulls declined from 14 to 7%. Daughters of AI proven bulls gave from 110 to 180 kg more milk than the daughters of PT bulls and 360 to 450 kg more milk than the daughters of natural service bulls in every year examined. More extensive and rapid sampling and increased selection intensity have helped bring genetic gains. Replacing remaining natural service with AI would lead to even bigger genetic gains.