title: Hormones, metabolites, and reproduction in Holsteins, Jerseys, and their crosses.
abstract: Holsteins (HH), Jerseys (JJ), and their crosses in first (n=157) and second (n=107) lactation were used to determine if reproduction, progesterone (P4), insulin-like growth factor 1 (IGF-1), insulin, nonesterified fatty acids (NEFA), and milk production differed between genetic groups. Thirty-four cows were Holstein-Jersey (HJ) crosses, 46 were Jersey-Holstein (JH) crosses, 48 were purebred Holsteins (HH), and 29 were purebred Jerseys (JJ) in first lactation, whereas the second-lactation animals included 23 HJ, 35 JH, 35 HH, and 14 JJ. Blood samples were collected weekly for the first 10 wk postpartum. Analyses were conducted using the MIXED, chi-square, and GLIMMIX procedures (SAS Institute Inc., Cary, NC). Seasons of calving were cold (November to May) and hot (June to October) and were combined with year to form 8 year-seasons. Days open and number of services were affected by genetic group. The HH were open 169±8 d, which was greater than HJ (143±9 d), JJ (132±10 d), and JH (127±8 d). The HH had 2.4±0.1 services per pregnancy, which was greater than JH (1.9±0.1), but not different from HJ (2.1±0.2) or JJ (2.1±0.2). Concentrations of NEFA were greater in lactation 2 (0.52±0.02 mEq/L) than in lactation 1 (0.45±0.02 mEq/L) and decreased over the 10-wk period. Concentrations of NEFA were greater in the cold season except in yr 3. Insulin in lactation 1 (0.81±0.03 ng/mL) was greater than in lactation 2 (0.72±0.03 ng/mL); insulin decreased to wk 2 then gradually increased. The HJ had the greatest insulin concentrations (0.87±0.04 ng/mL) and the JJ had the lowest (0.66±0.04 ng/mL), and IGF-1 gradually increased over the 10-wk period. Milk production (actual yield in the first 305 d, not adjusted for fat and protein) was affected by genetic group, lactation number, year-season, and wk 1 insulin. The HH produced 10,348±207 kg of milk, which was greater than the HJ (9,129±230 kg), the JH (9,384±190 kg), and the JJ (7,080±240 kg). Milk production in lactation 2 (9,676±163 kg) was greater than that in lactation 1 (8,294±160 kg). The JJ (10.3±4.7%) had the highest frequency of mastitis. The chance of getting mastitis for HH (1.1±0.9%) differed from that for HJ (9.4±4.1%), JH (8.1±3.4%), and JJ (10.3±4.7%). Genetic group affected hormones and metabolites, which may partially explain differences in reproductive measures and milk yield.
authors.affiliation: Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Brown
authors.forename: B G
authors.initials: BG
authors.lastname: Cassell
authors.forename: M L
authors.initials: ML
authors.lastname: McGilliard
authors.forename: M D
authors.initials: MD
authors.lastname: Hanigan
authors.forename: F C
authors.initials: FC
authors.lastname: Gwazdauskas
mesh_terms: D000818:Animals; D001947:Breeding; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007774:Lactation / Q000502:physiology; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012098:Reproduction / Q000502:physiology*; D013045:Species Specificity
chemical_list: D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011374:Progesterone; D007334:Insulin-Like Growth Factor I