Abstract The restriction of nutrient intake by beef cows during pregnancy may influence the progeny postpartum growth potential, therefore, the objective of the present study was to evaluate the effects of nutritional restriction and adequate nutrition or overfeeding during the final third of gestation of the crossbred cows (Charolais x Nellore) kept in the Pampa biome, on the productive performance of the progeny up to 15 mo of age. Eighty-three (83) cows were divided into: control cows on natural pasture under nutritional restriction (RES); Supplementation to meet 100 % of requirements (REQ); Supplementation above requirements (HIGH). REQ and HIGH calves had higher body weight at birth compared to calves from RES cows (39.28, 39.13 vs 34.58 kg), without influences on postnatal performance. Females from REQ and HIGH cows presented better postnatal performance and consequently higher weight at 12 mo of age in compared to offspring RES cows (300.71 and 311.79 vs 259.47 kg). These female calves reached 60 % of early adult weight (358 and 345 vs 405 d) and had a higher percentage of breeding at twelve months of age (73.98 and 84.08 vs 34.08 %) than females from RES cows. Supplementing cows to meet 100% requirements, as well as overfeeding during the final third of gestation, improves offspring performance at twelve months of age, with males and females responding differently to maternal nutritional insults during this period.

Resumen La restricción de la ingesta de nutrientes por parte de las vacas de carne durante la gestación puede influir en el potencial de crecimiento posparto de la progenie, por lo que el objetivo del presente estudio fue evaluar los efectos de la restricción nutricional y de la nutrición adecuada o la sobrealimentación durante el último tercio de la gestación de las vacas cruzadas (Charolais x Nellore) criadas en el bioma pampeano, sobre el rendimiento productivo de la progenie hasta los 15 meses de edad. Ochenta y tres (83) vacas se dividieron en tres tipos de tratamiento: vacas de control en pastos naturales bajo restricción nutricional (RES); suplementación para satisfacer el 100 % de las necesidades (REQ); suplementación por encima de las necesidades (ALTO). Los terneros nacidos de vacas con tratamiento REQ y ALTO tuvieron un mayor peso corporal al nacimiento que los terneros de las vacas con tratamiento RES (39.28, 39.13 vs 34.58 kg), sin que esto haya influido en el rendimiento postnatal. Las hembras de las vacas con tratamiento REQ y ALTO presentaron un mejor rendimiento postnatal y, en consecuencia, un mayor peso a los 12 meses de edad en comparación con las crías de las vacas con tratamiento RES (300.71 y 311.79 frente a 259.47 kg). Estos terneros alcanzaron el 60 % del peso adulto temprano (358 y 345 vs 405 d) y tuvieron un mayor porcentaje de reproducción a los doce meses de edad (73.98 y 84.08 vs 34.08 %) que las hembras nacidas de las vacas con tratamiento RES. La suplementación de las vacas para satisfacer el 100 % de las necesidades, así como la sobrealimentación durante el último tercio de la gestación, mejora el rendimiento de las crías a los doce meses de edad, y los machos y las hembras responden de forma diferente a los insultos nutricionales de la madre durante este periodo.

Abstract Bioelectrical impedance analysis (BIA) is a method based on the different levels of opposition to the flow of an ionic current through the different body tissues. Results are expressed by primary measures of resistance (Rs) and reactance (Xs). From such measures, equations are applied to determine the phase angle (PA) and impedance (Z). Bioimpedance analysis has been indicated as a reliable and precise method to determine the body composition and nutritional status in humans. BIA has recently been adapted to be applied on animal production. Therefore, the aim of this review is to provide an analysis on the potential use of bioelectrical impedance on zootechnical production. Through BIA, correlations among bioelectrical measures and tissue composition of swine, bovine, ovine, bubaline and fish carcasses can be established. In this regard, a growing number of demands were led by more precise and cost-effective methods to evaluate the body composition in the zootechnical sector, in which the analysis of bioelectrical impedance proved to be a promising and minimally invasive technology to replace traditional methods.

Resumen El análisis de impedancia bioeléctrica (AIB) es un método basado en los diferentes niveles de oposición al flujo de una corriente iónica a través de los diversos tejidos corporales. Los resultados se expresan mediante medidas primarias de resistencia (Rs) y reactancia (Xs). A partir de estas medidas, se aplican ecuaciones para determinar el ángulo de fase (AF) y la impedancia (Z). El análisis de bioimpedancia ha sido indicado como un método fiable y preciso para determinar la composición corporal y el estado nutricional en los seres humanos. El AIB se ha adaptado recientemente para ser aplicado en la producción animal. Por lo tanto, el objetivo de esta revisión es proporcionar un análisis sobre el uso potencial de la impedancia bioeléctrica en la producción zootécnica. A través del AIB se pueden establecer correlaciones entre las medidas bioeléctricas y la composición de los tejidos de los cadáveres de los cerdos, los bovinos, los ovinos, los bufalinos y los peces. En este sentido, entre el número creciente de demandas destaca la de contar con métodos más precisos y rentables para evaluar la composición corporal en el sector zootécnico, entre los que el análisis de la impedancia bioeléctrica demostró ser una tecnología prometedora y mínimamente invasiva para reemplazar los métodos tradicionales.

The response of energy supplementation was evaluated on the development and reproductive performance of beef heifers on temperate grasslands. Twenty-eight Charolais × Nellore heifers, with initial average age of 18 months and initial live weight of 274.9 kg were utilized. The animals were maintained on oat + ryegrass pasture and distributed in the following treatments: no supplementation (NS): heifers kept exclusively on pasture; MEG: supplementation with protected fat Megalac®; BRM: supplementation with brown rice meal; BRM+MEG: supplementation with BRM + protected fat. The average final weight of the heifers was of 403.4 kg and corresponded to 89.5% of the adult weight. The body condition of heifers increased linearly with daily increase of 0.012 points, correlating positively with the final weight. There was interaction between treatment and period for average daily weight gain. The highest daily weight gain, 1.395 kg, occurred in the first period when the animals were supplemented with BRM+MEG. In the last period, the NS animals presented the lowest daily weight gain, 0.888 kg. Supplementation with brown rice meal and/or protected fat does not interfere in the intake of pasture by heifers or increase the total intake of dry matter, not changing, therefore, the average daily weight gain at the end of the period of grazing. The daily weight gain does not change during supplementation. The use of temperate pasture with and without supplementation promotes the proper development of the structure and reproductive tract of heifers, benefiting the animal performance indexes in the first mating at 25-27 months of age.

Avaliaram-se as características da carcaça de novilhos Aberdeen Angus super jovens de biótipos pequeno e médio, terminados em confinamento e abatidos com semelhante espessura de gordura subcutânea. A idade e o peso vivo médio de ingresso no confinamento foram de 298 dias e 202 kg. Os animais foram confinados durante 158 dias, abatidos com espessura de gordura subcutânea média de 6,4 mm. A alimentação foi composta por silagem de sorgo e concentrado, na razão volumoso:concentrado de 60:40 na matéria seca, nos primeiros 63 dias e após, 50:50 até o abate. O biótipo foi calculado utilizando a fórmula B=-11,548 + (0,4878xh) - (0,0289xID) + (0,0000146xID²) + (0,0000759xhxID), em que h representou a altura e o ID idade em dias. Novilhos com biótipo médio apresentaram superioridade nos aspectos importantes de comercialização, como o peso de carcaça quente (p < 0,0001) e fria (p < 0,0001). As medidas de musculosidade da carcaça como a área de longissimus dorsi em relação ao peso de carcaça fria (p = 0,0477) e de corpo vazio (0,0419) foram menores nos novilhos de biótipo médio. A conformação da carcaça, área de longissimus dorsi em cm² e espessura de coxão foram semelhantes entre os biótipos. Os cortes comerciais, dianteiro (p < 0,0001), costilhar (p = 0,009) e traseiro especial (p = 0,0003) em kg foram superiores nos de biótipo médio. Em percentagem, o corte traseiro diminuiu 0,18% com o aumento no biótipo (p = 0,0404). Em peso, os tecidos constituintes da carcaça aumentaram com o biótipo do novilho, já quanto à percentagem o tecido muscular apresentou queda de 0,57% (p = 0,0410).

Carcass characteristics of small and medium-frame Aberdeen Angus young steers, finished in feedlot and slaughtered with similar subcutaneous fat thickness are evaluated. The average age and live weight at the start of feedlot were respectively 298 days and 202 kg. The steers were confined during 158 days, and slaughtered with average subcutaneous fat thickness of 6.4 mm. The feed consisted of sorghum silage and concentrate at 60:40 ratio of dry matter during the first 63 days and 50:50 afterward. The frame was calculated by formula F =-11.548 + (0.4878xh) - (0.0289xID) + (0.0000146xID²)+(0.0000759xIDxh), where h is the height and ID the age, in days. Steers with medium frame showed superiority in important marketing aspects such as warm (p < 0.0001) and cold carcass (p < 0.0001) weights. Muscularity measurements such as longissimus dorsi area in relation to cold carcass (p = 0.0477) and empty body (p = 0.0419) weights were lower for medium-frame steers. Carcass conformation, longissimus dorsi area and cushion thickness were similar in both frame. The commercial cuts, forequarter (p < 0.001), flank (p = 0.009) and saw cut (p = 0.0003) in kg were higher for medium-frame steers. Saw cut decreased 0.18% with an increase in frame (p = 0.0404). Weight of the carcass tissues increased with the steers frame, whereas the percentage of muscle tissue decreased 0.57% (p = 0.0410).