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 ± 9.6 DO which was different from HJ (142.9 ± 11.3 d), JJ (132.1 ± 12.1 d), and JH (127.2 ± 9.3 d). HH had 2.4 ± 0.1 services per conception which was different from JH (1.9 ± 0.1), but not different from HJ (2.1 ± 0.2) or JJ (2.1 ± 0.2). In HH P4 concentrations (1.6 ± 0.11 ng/mL) were not different from HJ (1.5 ± 0.12 ng/mL), but lower than JH (1.8 ± 0.10 ng/mL) and JJ (1.8 ± 0.13 ng/mL). NEFA concentrations were greater in lactation 2 (0.52 ± 0.02 mEq/L) than in lactation 1 (0.45 ± 0.02 mEq/L). Insulin in HH (0.83 ± 0.03 ng/mL) was not different from HJ (0.87 ± 0.04 ng/mL) or JH (0.76 ± 0.03 ng/mL), but was greater than JJ (0.66 ± 0.04 ng/mL). IGF-I gradually increased over the 10 wk period. The HH produced 10,348 ± 208 kg of milk, which was greater than the HJ (9,129 ± 230 kg), the JH (9,384 ± 192 kg), and the JJ (7,080.9 ± 261 kg). Reproductive measures, milk yield, hormones and metabolites were affected by genetic groups. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/34746 |
| Date | 06 September 2010 |
| Creators | Brown, Karen Leigh |
| Contributors | Dairy Science, Hanigan, Mark D., Cassell, Bennet G., Gwazdauskas, Francis C. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | Brown_KL_T_2010.pdf |
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