Dinámica de la asignación forrajera durante el último tercio de gestación y hasta el destete: efecto sobre los perfiles endócrino-metabólicos de vacas de cría primíparas y sus terneros

Uruguay's livestock systems are sustained on a pastoral basis, whose production fluctuates in quantity and quality throughout the year. In this context, late gestation and the beginning of lactation coincide with periods when forage production decreases, which forces pregnant animals to reprogram the intrauterine growth trajectory. The aim of the present work was to study the effect of the dynamic change in forage allocation in the period between the last third of gestation and weaning on productive behavior and metabolism of primiparous cows and their calves, grazing natives pastures. For this, two treatments were used: a) high supply of forage (AOF, last third: decrease from 8 to 4 kg DM / 100 kg LW, calving to weaning: rise from 4 to 12 kg DM / 100 kg LW) and b) low supply of forage (BOF, last third of gestation, was maintained, 4 to 4 kg DM / 100 kg BW, parturition to weaning: rise from 4 to 8 kg DM / 100 kg BW). The trial was carried out at the Bernardo Rosengurtt Experimental Station, Cerro Largo, Uruguay. No treatment effects were observed on maternal metabolites, glucose (3.15 ± 0.06 vs. 3.23 ± 0.07 mmol / L, P = 0.4453), urea (28.43 ± 0.80 vs. 27.44 ± 0.88, total protein (64.11 ± 0.77 vs. 65.68 ± 0.81, P = 0.1756), albumin (30.81 ± 0.39 vs. 31.26 ± 0.41, P = 0.4300) g / L, P = 0.4170), BHB (0.60 ± 0.05 vs. 0.61 ± 0.05, P = 0.7992) mM, AOF vs. BOF, respectively. Neither treatment effects were observed on the calf metabolites, glucose (4.49 ± 0.16 vs. 4.41 ± 0.17, P = 0.7440), urea (21.93 ± 0.71 vs. 20.46 ± 0.79, P = 0.1785), total protein (56.48 ± 0.82 vs. 57.68 ± 0.90, P = 0.3377), alumina (33.02 ± 0.45 vs. 33.90 ± 0.49, P = 0.1966) g / L, AOF vs. BOF, respectively, except immunoglobulins (22.16 ± 0.91 vs. 24.91 ± 1.03, P = 0.0574) g / L and BHB (0.10 ± 0.03 vs. 0.24 ± 0.041, P = 0.0231) m / M, AOF vs. BOF, respectively. The PV of the calves at birth did not show significant differences, however, at weaning, the BOF calves had a PV 10% higher than the AOF calves. The study of the morphological characteristics of the placenta indicated that the BOF placentas had a greater cotyledonary surface. Nutritional restriction during pregnancy did not significantly affect maternal metabolites or their offspring, except for immunoglobulins. This could indicate that the body starts up adaptive metabolic and placental mechanisms in such a way that physiological processes continue under the new prevailing conditions.