Abstract

DOMINGUEZ, Carlos et al. Efecto de la condición corporal al parto y del nivel de alimentación sobre la involución uterina, actividad ovárica, preñez y la expresión hipotalámica y ovárica de los receptores de leptina en vacas doble propósito. Rev. Fac. Cienc. Vet. [online]. 2008, vol.49, n.1, pp.023-026. ISSN 0258-6576.

Effect of Body Condition at Calving and Feeding Level on Uterine Involution, Ovarian Activity, Pregnancy and the Hypothalamic and Ovarian Expression of Leptin Receptors in Dual Purpose Cows Abstract  To evaluate the effect of body condition at calving (BCAC) and different feeding levels (FL) on uterine involution (UI), ovarian activity (OA), pregnancy (PR), and hypothalamic and ovarian leptin receptor expression (LEPEXP) in postpartum cows, twenty seven crossbred cows (Bos taurus x Bos indicus) were randomly assigned in a 2 x 2 factorial design into four treatments (T): T1, low body condition (LBC; < 2.5) + low FL (LBCLFL; n = 6); T2, LBC (< 2.5) + high FL (LBCHFL; n = 7); T3, high BC (> 2.5) + low FL (HBCLFL; n = 7) and; T4, high BC (>2.5) + high FL (HBCHFL; N = 7). Basal diet was made of hay from Cynodon nlemfluensis  (11% crude protein, CP) plus supplement (23% CP) at a 70:30 ratio. To assess uterine involution (UI), the following was considered: characteristic of uterine secretion (CUS), uterine horn simmetry (UHS), cervix diameter (CD), and uterine position (UP). Weekly, from 15 to 45 days postpartum (DPP), the reproductive tract was evaluated by transrectal palpation, ultrasonography, and RIA of plasma progesterone (P₄). The OA was assessed through the ovarian follicles (OF), which were classified as :  C1 (≤ 5 mm), C2 (6-9 mm), C3 (≥ 10 mm); and the presence of corpora lutea (CL). The PR was verified by rectal palpation, ultrasound, and  P₄. Metabolic changes were measured as total cholesterol (TC) and fructosamine (FRTS) at 3, 15, and 45 DPP. The hypotalamic and ovarian LEPEXP were determined by Western blot from tissue samples of 8 cows slaughtered at 45 DPP. Data were statistically analyzed by multivariate multiple regressions, ANOVA for repeated measurements on time, Cox’s multiple regression and a Kruskal and Wallis test. Results show a correlation between T and C3 and between C3 and CUS at 22 and 30 DPP. Also, a correlation was detected between CL and CUS at 37 DPP. No association between C1 and T or C1 and UI was found. The multivariate multiple regressions detected a significant effect (P<0.05) of T and CD on OA. The BCAC influenced OA (P < 0.01). Cox value for CL depended on CUS and UHS (P<0.01). The effect of T and BCAC over accumulated P₄ was significant (P<0.05) and BCAC had an effect on P₄ from 30 DPP. FRTS was different among T (P<0.05), but were not among sample times. The LEPEXP for hypothalamus was higher for cows with  high BCAC, independently from FL. The PR was different among T (P<0.01). Values for PR at 120 DPP were: T3: 75% and T4: 60% vs T2: 0% and T1: 20%. In summary, T, BCAC, CUS and UHS exerted a positive effect on OA. The LEPEXP at the hypothalamus levels corroborated the response of BCAC on OA. Consequently, there was a high pregnancy rate before 120 DPP in T with better BCAC.

Keywords : Livestock; multipurpose breeds; body condition; parturition; diet; oestrous cycle; weight gain; leptin; Aragua.

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