Hormones, Metabolites, and Reproduction in Holsteins, Jerseys, and their crosses
Brown, Karen Leigh
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Cows in first (n = 163) and second (n = 101) lactation were studied to determine if reproduction, progesterone (P4), IGF-I, insulin, NEFA, and milk production differed between genetic groups. Thirty-five cows were Holstein-Jersey (HJ) crosses, 48 were Jersey-Holstein (JH) crosses, 51 were Holsteins (HH), and 29 were Jerseys (JJ). Days open (DO) was affected by genetic group. HH had 168.6 Â± 9.6 DO which was different from HJ (142.9 Â± 11.3 d), JJ (132.1 Â± 12.1 d), and JH (127.2 Â± 9.3 d). HH had 2.4 Â± 0.1 services per conception which was different from JH (1.9 Â± 0.1), but not different from HJ (2.1 Â± 0.2) or JJ (2.1 Â± 0.2). In HH P4 concentrations (1.6 Â± 0.11 ng/mL) were not different from HJ (1.5 Â± 0.12 ng/mL), but lower than JH (1.8 Â± 0.10 ng/mL) and JJ (1.8 Â± 0.13 ng/mL). NEFA concentrations were greater in lactation 2 (0.52 Â± 0.02 mEq/L) than in lactation 1 (0.45 Â± 0.02 mEq/L). Insulin in HH (0.83 Â± 0.03 ng/mL) was not different from HJ (0.87 Â± 0.04 ng/mL) or JH (0.76 Â± 0.03 ng/mL), but was greater than JJ (0.66 Â± 0.04 ng/mL). IGF-I gradually increased over the 10 wk period. The HH produced 10,348 Â± 208 kg of milk, which was greater than the HJ (9,129 Â± 230 kg), the JH (9,384 Â± 192 kg), and the JJ (7,080.9 Â± 261 kg). Reproductive measures, milk yield, hormones and metabolites were affected by genetic groups.
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