title: Effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and postpartum resumption of ovulation.
abstract: The aim of this study was to determine the effect of prepartum somatotropin injection in late-pregnant Holstein heifers on metabolism, milk production and resumption of postpartum ovulation. For this study, 31 late-pregnant Holstein heifers were used. The heifers were assigned randomly into two treatments: (1) 500 mg sc injections of somatotropin (somatotropin treatment, n = 15) at -35 and -21 days, and, if pertinent, at -7 days from expected calving date and (2) no treatment (control group, n = 16). Blood samples were collected weekly from -5 to 7 weeks after calving. Heifers with progesterone concentrations in plasma above 1 ng/ml in two consecutive postpartum samples were considered as having resumed ovarian activity. A higher proportion (P = 0.04) of heifers treated with somatotropin resumed ovarian activity in the first 7 weeks post partum (73.3%; 11/15) compared with the control group (37.5%; 6/16). A higher number (P = 0.02) of heifers in the somatotropin treatment group also ovulated during the first postpartum follicular wave (53.3%; 8/15) compared with the control group (12.5%; 2/16), as indicated by the number of heifers ovulating in the first 3 weeks post partum. Pregnancy rate was not affected by treatments (P > 0.10) and averaged 40.0% (6/15) in somatotropin-treated and 25.0% (4/16) in control heifers when evaluated up to 150 days in milk. Somatotropin treatment increased the average daily milk production by 2.8 kg/cow per day (P < 0.0001) and reduced the somatic cell count (P = 0.009). Plasma IGF-I was higher (P < 0.05) for somatotropin-treated heifers in the prepartum period. Insulin and body condition score were higher (P < 0.05) and non-esterified fatty acids were lower (P < 0.05) for somatotropin-treated cows in the early postpartum period. In conclusion, somatotropin injection during the prepartum period in late-pregnant Holstein heifers was able to increase the proportion of heifers resuming ovarian activity early post partum, inspite of higher milk production.
authors.affiliation: Department of Veterinary Clinics, Veterinary College, Federal University of Pelotas, Campus Universitário, CEP 96010-900 Pelotas, RS, Brazil. augusto.schneider@live.com
authors.forename: A
authors.initials: A
authors.lastname: Schneider
authors.forename: E
authors.initials: E
authors.lastname: Schwegler
authors.forename: P
authors.initials: P
authors.lastname: Montagner
authors.forename: L T
authors.initials: LT
authors.lastname: Hax
authors.forename: E
authors.initials: E
authors.lastname: Schmitt
authors.forename: L F M
authors.initials: LF
authors.lastname: Pfeifer
authors.forename: F A B
authors.initials: FA
authors.lastname: Del Pino
authors.forename: I
authors.initials: I
authors.lastname: Bianchi
authors.forename: G R
authors.initials: GR
authors.lastname: Paludo
authors.forename: M N
authors.initials: MN
authors.lastname: Corrêa
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D002417:Cattle / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage* / Q000097:blood; D007279:Injections, Subcutaneous / Q000662:veterinary; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000145:classification; D007774:Lactation; D008892:Milk / Q000378:metabolism*; D010053:Ovary / Q000502:physiology*; D049590:Postpartum Period; D011247:Pregnancy; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; C073294:growth hormone, bovine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone