title: A systems comparison of once- versus twice-daily milking of pastured dairy cows.
abstract: The objective of this study was to compare the effect of milking frequency (once vs. twice-daily milking) and breed (Holstein-Friesians vs. Jerseys) on milk and milk solids (MS; milk fat + milk protein), yield per cow, milk composition, somatic cell count and lactation length; cow body weight, body condition score, and reproductive performance over a 4-yr period. Total cow numbers in each herd were 30, 35, 36, and 42 for Holstein-Friesians milked once or twice daily, and Jerseys milked once or twice daily, respectively. Forty hectares of pasture were subdivided into 4 smaller pastures of 10 ha each. Stocking rates for the once-daily herds were 16.7% greater than the twice-daily herd in their respective breed. An increased stocking rate was chosen to achieve equal milk and MS per ha from the 2 milking frequencies. Annual milk, fat, protein, and lactose yields per cow were less for once-daily than for twice-daily milking. Interactions were detected between milking frequency and breed for annual milk, fat, protein, and lactose yields per cow, because Jerseys were relatively less affected by once-daily than by twice-daily milking than Holstein-Friesians. Holstein-Friesian cows milked once daily produced 31.2% less milk and 29.4% less MS per cow than their twice-daily counterparts. In contrast, Jersey cows milked once daily produced 22.1% less milk and 19.9% less MS per cow than their twice-daily counterparts. Milk per ha was 17.7 and 9% less for the once-daily Holstein-Friesians and once-daily Jersey herds, respectively, compared with their twice-daily counterparts, because the greater stocking rate for the once-daily herds did not fully compensate for the milk loss per cow. Milking once daily increased somatic cell count throughout the year in both breeds. Cows milked once daily conceived 3 d earlier, took 5 d less from calving to conception, and needed 11% fewer controlled internal drug release devices than those milked twice daily. Milking once daily is a viable milking option for New Zealand farmers who are prepared to trade-off loss of MS income for increased time to accomplish other non-milking activities.
authors.affiliation: Dexcel, Private Bag 3221, Hamilton, New Zealand. dave.clark@dexcel.co.nz
authors.forename: D A
authors.initials: DA
authors.lastname: Clark
authors.forename: C V C
authors.initials: CV
authors.lastname: Phyn
authors.forename: M J
authors.initials: MJ
authors.lastname: Tong
authors.forename: S J
authors.initials: SJ
authors.lastname: Collis
authors.forename: D E
authors.initials: DE
authors.lastname: Dalley
mesh_terms: D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D002452:Cell Count; D003612:Dairying / Q000379:methods*; D004032:Diet; D005223:Fats / Q000032:analysis; D005260:Female; D007774:Lactation; D007785:Lactose / Q000032:analysis; D008892:Milk / Q000737:chemistry / Q000166:cytology; D008894:Milk Proteins / Q000032:analysis; D011247:Pregnancy
chemical_list: D005223:Fats; D008894:Milk Proteins; D007785:Lactose