Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2006
Publication Date: 7/9/2006
Citation: Norman, H.D., Wright, J.R., Powell, R.L. 2006. Domestic versus imported artificial-insemination semen for Holstein graziers in the United States [abstract]. Journal of Dairy Science. 89(Suppl. 1):136(abstr. 157). Interpretive Summary:
Technical Abstract: In recent years, interest has increased in the United States regarding grazing of dairy cows in order to reduce machinery, feed, and labor costs. Success with grazing requires that cows begin lactations when pasture is ready. This places a premium on fertility, a trait that has been declining. Grazing has been the general practice in New Zealand (NZ) for many years. Use of NZ bulls in the US assumes that bulls selected for good daughter performance in NZ will be good choices for US graziers. The objective of this study was to compare the US performance of daughters of NZ AI bulls with that of US-sired contemporaries. Data were milk, fat, protein, SCS, and days open (DO) from 161 US herds having daughters of 26 NZ Holstein-Friesian bulls. For each of these 565 daughters, the difference in standardized phenotype from 6,506 US-sired herd contemporaries was computed for parities 1, 2, and 3. Daughters of the 1,168 US bulls were significantly higher for milk (473-545 kg) and protein (5-6 kg) yield in each parity and significantly lower for SCS (0.2 units) in first and second parity. Daughters of the NZ bulls were slightly higher (1-2 kg) for fat yield (not significant). First-parity days open were significantly lower (7 d) for NZ daughters. The difference in second parity (1 d) and third parity (8 d favoring daughters of US bulls) were not significant. Differences favored US bulls for milk, protein, and SCS. NZ bulls were favored for first-parity days open. Bulls were compared to all AI bulls in their own countries born in 1994-96 and were generally above the 50th percentile (47th to 76th) for most traits, being higher for NZ bulls, as expected because imported bulls are selected based on the foreign progeny test. To date, results for these traits do not suggest that importation of semen from bulls selected under NZ conditions is advantageous for US grazing operations.