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Effect of breed and parity on performance responses in early lactation dairy cows.

G. I. Zanton




Effect of breed and parity on performance responses in early lactation dairy cows.
G. I. Zanton*. USDA-ARS, US Dairy Forage Research Center Madison, WI.

The objective of this study was to characterize breed and parity effects on production and feed efficiency (FE) in first (1P) and second (2P) parity Holstein (H) and Jersey (J) cows. Cows were randomly selected from the research herd based on expected calving dates, enrolled into the study at calving (n = 13/group, except for 1P-J cows where n = 12), and studied for 12 wk. Cows were housed in tie-stalls and individually fed a total mixed ration once daily (formulated to contain 28.5% NDF, 17% CP, and 27% starch), milked thrice daily, and had free access to water throughout the study. Feed intake and milk yield were measured daily, BW was measured and each milking was sampled for composition semiweekly, and body condition score (BCS) and structural measurements were collected during wk 1, 4, 8, and 12. Data were analyzed as a completely randomized design with a 2 � 2 factorial combination of independent variables and evaluated for main effect (breed = Br, parity = Pa) and interaction (Br � Pa) responses with P < 0.05 signifying significant differences. A Br � Pa interaction existed for initial BW and structural measurements (2P-H > 1P-H > 1P-J = 2P-J), whereas calving BCS was not different among groups (3.85 � 0.44 SD). Maximum losses of BCS and BW (% of initial BW) were greater for 2P than 1P, but did not differ between Br. DMI was affected by Br � Pa with 2P-H > 1P-H > 1P-J = 2P-J, however Br was the only factor affecting DMI when expressed as a % of BW with J > H. Protein concentration was greater for J than H and lactose concentration was greater for H than J, whereas Pa was without effect on these responses. Fat concentration was affected by Br � Pa with 1P-J = 2P-J > 2P-H > 1P-H; the difference between 1P-H and 2P-H was most pronounced before wk 7. Yields of fluid milk, components, and net energy were greater for H than J and for 2P than 1P, although Br � Pa affected the magnitude of these differences among groups. FE (milk net energy / DMI) was unaffected by Br and greater for 2P than 1P although these differences disappeared after wk 7. Under these conditions, Br, Pa, and Br � Pa affected production responses, however FE was only transiently affected by Pa.

Keywords: breed, efficiency, parity.