title: Factors affecting fertility according to the postpartum period in crossbred dual-purpose suckling cows in the tropics.
abstract: To determine the relationship between first service conception rate (FSC) and the postpartum period (PP), 6160 calvings from 2250 crossbred dual-purpose cows were analysed. The effects of breed predominance (BT: Bos taurus and BI: Bos indicus), season of service (dry, intermediate and humid), parity (1 or 2 and more), agroecological region (Sub-humid and Dry Tropical Forest) and milk production were studied. The postpartum period was grouped according to the calving-first service interval as G1 < or = 60 days (n = 1889); G2 > 60 < or = 90 days (n = 1436); G3 > 90 < or = 120 days (n = 1030); and G4 > 120 days (n = 1805). Data were analysed by chi-squared test. The overall mean for FSC was 58.2% and was lower in G1 (p < 0.01). All PP showed a breed effect on FSC, with mean values of 61.6% and 53.3% for BI and BT, respectively. Season of service also affected FSC, which was significantly lower during the humid period: 51.2% versus 57.4% and 61.5% for the intermediate and dry periods (p < 0.01), respectively. Parity and environmental effects were not observed on FSC. Levels of milk yield did influence the FSC, which decreased from 66.7% and 61.0% for milk yields of < 1500 kg and between 1501 and 2000 kg to 46.0% in milk yields > 2000 kg (p < 0.01).
authors.affiliation: Departamento de Ciencias Agrarias, Universidad de los Andes, Trujillo, Estado Trujillo. ferromi@ula.ve
authors.forename: F
authors.initials: F
authors.lastname: Perea-Ganchou
authors.forename: E
authors.initials: E
authors.lastname: Soto Belloso
authors.forename: C
authors.initials: C
authors.lastname: González Stagnaro
authors.forename: G
authors.initials: G
authors.lastname: Soto Castillo
authors.forename: H
authors.initials: H
authors.lastname: Hernández Fonseca
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D002417:Cattle / Q000502:physiology*; D003433:Crosses, Genetic; D003612:Dairying / Q000379:methods; D005260:Female; D005298:Fertility / Q000502:physiology*; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000378:metabolism; D010298:Parity; D049590:Postpartum Period; D011247:Pregnancy; D012621:Seasons; D013391:Sucking Behavior / Q000502:physiology*; D014329:Tropical Climate