Bioestimulação e comportamento reprodutivo de novilhas de corte Biostimulation and reproductive performance of beef heifers

O objetivo do presente trabalho foi determinar se a bioestimulação é capaz de alterar favoravelmente o comportamento reprodutivo de novilhas de corte em sua primeira estação reprodutiva. Para isso, 50 dias antes do início da inseminação artificial (IA), 60 novilhas de dois anos (Hereford x Nelore) foram divididas ao acaso em dois grupos: bioestimuladas (BE), através do uso de rufiões, ou não (NE). As taxas de novilhas cíclicas antes do início da IA foram de 76 e 56% para BE e NE, respectivamente. As taxas de prenhez foram de 90 e 73% para BE e NE, respectivamente. A bioestimulação determinou diferenças nos percentuais acumulados de novilhas inseminadas por subperíodos de 21 dias de IA, sem alterar a data média de concepção. Foi observado efeito de idade/desenvolvimento corporal na resposta à bioestimulação.<br>The goal of this experiment was to evaluate if biostimulation may favourably change the reproductive performance of beef heifers on their first breeding season. For this purpose, 50 days before the artificial insemination (AI) period, 60 two-year-old heifers (Hereford x Nelore) were randomly distributed into two treatment groups: biostimulatated (BE) using a ruffian or not biostimulated (NE). The rates of cycling heifers before AI were 76 and 56% for BE e NE, respectively. Conception rates were 90 and 73% for BE e NE, respectively. Biostimulation changed accumulated percents of inseminated heifers by the end of 21 days periods during AI, without changing mean conception day. It was observed the effect of age/body development in the responses to biostimulation

Sistemas de Alimentação Pós-Desmama de Bezerras de Corte para Acasalamento com 14/15 Meses de Idade Post Weaning Feeding Systems for Beef Heifers to be Bred at 14/15 Months of Age

Este trabalho foi conduzido com o objetivo de avaliar o desempenho de bezerras de corte submetidas a sistemas alternativos de alimentação, no primeiro período outono/inverno pós-desmama, por 88 dias, e, após este período, mantidas sobre pastagem melhorada, até o final do seu primeiro acasalamento, com 14-15 meses de idade. Os sistemas utilizados foram: pastagem- pastejo contínuo em pastagem cultivada de azevém (Lolium multiflorum Lam); suplementação- pastejo contínuo em pastagem natural e suplementação energético-protéica; confinamento- confinamento, a céu aberto, com silagem de sorgo + nitrogênio não-protéico (NNP). Após esse período, as bezerras pastejaram em conjunto pastagens naturais melhoradas compostas por azevém, trevo branco (Trifolium repens) e cornichão (Lotus corniculatus). Os dados foram coletados em uma Empresa Agropecuária, localizada em Dom Pedrito, RS, em 395 bezerras de corte pertencentes a três grupos genéticos: Hereford; 3/4 Hereford-1/4 Nelore; 5/8 Hereford-3/8 Nelore. Foram tomados registros de peso vivo (PV), ganho de peso médio diário (GMD) e condição corporal (CC). As bezerras mostraram comportamento semelhante quanto ao PV e GMD. A CC foi maior nos animais do grupo confinamento. No início e final da estação de acasalamento, novilhas alimentadas exclusivamente em pastagens tiveram maior PV e CC do que novilhas dos grupos suplementação e confinamento, que não diferiram entre si.<br>The experiment evaluated the performance of beef heifers submitted to three alternatives of autumn-winter feeding systems, during 88 days, and after this period on improved pastures all together until the end of theirs first mating season, with 14-15 months of age. The systems were: Pasture- continuous grazing on cultivated annual ryegrass (L. multiflorum Lam); supplementation- continuous grazing on natural pasture plus energy and protein supplementation; feedlot - feedlot, with sorghum silage plus non- proteic nitrogen (NNP). After this period, all heifers grazed together on improved natural pastures with annual ryegrass, white clover (Trifolium repens) and birdsfoot trefoil (Lotus corniculatus). These data were collected in a farm located in Dom Pedrito, RS, from 395 beef heifers from three genetic groups: Hereford; 3/4 Hereford -1/4 Nellore; 5/8 Hereford- 3/8 Nellore. Live weight (LW), body conditions score (BCS) and live weight daily gains (LDG) were recorded. No differences could be detected among systems for LW and LDG. Feedlot heifers had greater BCS. At the beginning and end of the mating season, heifers from pasture group were heavier and had greater BCS than heifers from feedlot and supplementation

Development and reproductive performance of beef heifers supplemented with brown rice meal and/or protected fat on temperate grasslands

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