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Domestic vs. imported AI semen for Holstein graziers in the US

Domestic vs. imported AI semen for Holstein graziers in the US. Background. Increasing interest in grazing to reduce costs (machinery, feed, labor) Increased importance of fertility to synchronize calvings and pasture availability

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Domestic vs. imported AI semen for Holstein graziers in the US

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  1. Domestic vs. imported AI semenfor Holstein graziers in the US

  2. Background • Increasing interest in grazing to reduce costs (machinery, feed, labor) • Increased importance of fertility to synchronize calvings and pasture availability • New Zealand (NZ) has used grazing as the standard practice for many years

  3. Assumptions • US producers have used semen from some NZ bulls • Usage may be intended to capitalize on selection for grazing conditions • Value of NZ bulls might be for yield on pasture or better fertility

  4. Objective • To compare US performance of daughters of NZ Holstein-Friesian AI bulls with that of contemporaries with US Holstein AI sires • Traits • Milk, fat, and protein yields • Somatic cell score • Days open • Conformation

  5. Data • 159 US herds with daughters of 26 NZ bulls and US-sired contemporaries • 552 daughters of NZ bulls and 6,266 daughters of US bulls • Phenotypes for yield, SCS, and days open for parities 1, 2, and 3 and first conformation scores (79 NZ-sired vs. 308 US-sired cows)

  6. Method • In addition to studying all herds using NZ bulls, a “grazing” subset was defined by seasonal calvings • More than 3 times as many calvings for March—May as for September—November for 3 consecutive years during 2002—2005 • 11 herds had 25 reported calvings/year

  7. Results Performance of NZ vs. US daughters(NZ minus US)

  8. Results Conformation of NZ vs. US daughters(NZ minus US)

  9. Results • But are these grazing herds? • Only 11 met seasonal calving requirement • Only 7% of herds, but 25% of NZ daughters • Although yield was lower for those 11 herds (8,647 vs. 9,418 kg milk), likely there was a grain-supplemented diet

  10. Grazing Results Performance of NZ vs. US daughters(NZ minus US)

  11. Conclusions • Some (much?) NZ semen likely used for reasons other than grazing characteristics • For all NZ daughters, milk and protein yields were lower, SCS higher, but days open less • For seasonal herds, NZ daughters again lower for milk yield, higher for SCS, higher for 3rd-lactation protein yield, and no longer significantly lower for days open

  12. Conclusions • To the degree that NZ semen was used to improve performance on pasture, only fertility was improved in first and second lactations • Daughters of NZ bulls were lower for final score and stature and had lower udders, perhaps because sire selection in NZ was at a much lower level of nutrition and production

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