title: Ovarian activity and reproductive performance of dairy cows fed different amounts of phosphorus.
abstract: Fifty-four multiparous Holsteins were utilized to determine the effect of dietary P on ovarian activity and reproductive performance. Cows were assigned at calving to diets containing 0.35 or 0.47% P. Ovarian activity was monitored 3 times weekly by ultrasonography, beginning 10 d after parturition until the end of a 60-d voluntary waiting period. After this period, cows were synchronized and bred using the Ovsynch protocol. During wk 2 of lactation, the number of small (3 to 5 mm in diameter) and large (>9 mm) follicles was similar between groups, but the number of medium (6 to 9 mm) follicles was lower for 0.35% P than for 0.47% P (1.2 vs. 1.9). Dietary P did not affect the number of days to first postpartum ovulation or the diameter of dominant and ovulating follicles. The multiple ovulation rate and the proportion of cows that were anovulatory or developed follicular cysts did not differ between groups. Dietary P amount did not influence corpus luteum development or blood progesterone concentration during the voluntary waiting period. The first service conception rate and pregnancy loss from 30 to 60 d after breeding were not affected. The overall pregnancy rate during the first 200 d of lactation (60.9 and 60.0%) and the number of services per pregnancy (2.1 and 1.9) did not differ between groups. Serum inorganic P was elevated from 6 to 7 mg/dL during the first 3 mo postpartum as dietary P was increased. Fecal P content measured during the first 16 wk of lactation averaged 0.63 and 0.89%, 29% lower for the 0.35% P group. Mean milk yield during the first 40 wk of lactation did not differ, averaging 40.5 and 39.0 kg/d for the 0.35 and 0.47% P groups, respectively. Overall, varying dietary P from 0.35 to 0.47% did not affect postpartum ovarian activity, reproductive performance, or milk production.
authors.affiliation: Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Tallam
authors.forename: A D
authors.initials: AD
authors.lastname: Ealy
authors.forename: K A
authors.initials: KA
authors.lastname: Bryan
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002118:Calcium / Q000097:blood; D002417:Cattle / Q000502:physiology*; D004032:Diet; D030762:Estrous Cycle / Q000502:physiology; D005243:Feces / Q000737:chemistry; D005260:Female; D009751:Nutritional Requirements; D006080:Ovarian Follicle / Q000502:physiology; D010053:Ovary / Q000000981:diagnostic imaging / Q000502:physiology*; D010060:Ovulation; D036801:Parturition; D010758:Phosphorus / Q000032:analysis / Q000097:blood; D016226:Phosphorus, Dietary / Q000008:administration & dosage*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D012098:Reproduction / Q000502:physiology*; D013997:Time Factors; D014463:Ultrasonography
chemical_list: D016226:Phosphorus, Dietary; D010758:Phosphorus; D011374:Progesterone; D002118:Calcium