Strategic feeding supplementation: An alternative for sustainability of beef production in native pastures

Abstract

The present study aimed to evaluate the effects of a strategic feeding supplementation protocol on reproductive and economic results of exclusively fixed timed artificial inseminated (FTAI) beef cows from a southern Brazilian herd. The experiment was carried out over 2 consecutive breeding seasons (2016 and 2017, from October to January). Two-hundred, 3 and 4 years old, non-suckled, Angus cows (n=100/year), were divided into two homogeneous groups (by weight and body condition score) 25 days before the first FTAI of the breeding season (First FTAI=Day 0). As a representation of traditional management of herds grazing on natural pastures from Rio Grande do Sul Province, Brazil, cows from control group (CG; n=100; 50 cows in each year) received basic mineral supplementation (without protein an energy) ad libitum during the entire experimental period. As an alternative feeding protocol, supplemented group (SG; n=100; 50 in each year) received a mineral supplementation enriched with protein (23%), energy (44% NDT) and sodium monensin (0.25%) ad libitum from days: –25 to 80 of breeding season. Cows were maintained in 2 separated paddocks of native pasture with similar forage composition and availability. All cows were submitted to a progesterone/estradiol-based estrus synchronization protocol on day -10, and cows not pregnant at diagnosis were resynchronized on days 28 and 76 using the same hormonal treatment. There was no year effect (P>0.1) on weight gain and reproductive results, data from both breeding seasons were polled together for further analyzes. Cows from SG presented higher average daily weight gain and gained more weight than cows from CG (p<0.001). Conception rate was higher for SG than CG at the first FTAI cycle (p<0.05). No differences between groups were detected on final pregnancy rates (CG=80% and SG=88%; p>0.1). Cows from SG became pregnant earlier (p<0.01) during the breeding seasons. Also, the feeding supplementation provided an opportunity to increase gross margin. In conclusion, strategic feeding supplementation of beef cows grazing in natural pasture and submitted exclusively to fixed timed artificial insemination increases cows’ weight gain, anticipates pregnancies during the breeding season and can increase profit margin when compared to traditional management adopted in southern Brazil.