Cow-calf intensification through the feeding of rice straw

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This study evaluated the effect of rice straw supplementation on cow-calf systems and the effect of increasing stocking rates on bio-economic efficiency. Three production systems were compared in which pregnant females were supplemented with different levels of rice straw in the prepartum: 1) 20 cows in 9 hectares (ha) of natural pasture without rice straw supplementation and stocking rate of 1,000 kg of body weight (BW)/ha (RSH0); 2) 30 cows in 13.5 ha of natural pasture receiving 5 kg of rice straw/animal/day and 1,000 kg BW/ha stocking (RSH5); and 3) 60 cows in 14 ha of natural pasture with 10 kg of rice straw/animal/day and stocking rate of 2,000 kg BW/ha (RSH10). The body condition score (BCS), cow weight at calving (CWC), and calf birth weight (CBW) were recorded on the first day and every 30 days. After calving, cows were moved to oat pasture (Avena strigosa) and ryegrass (Lolium multiflorum) with mineral supplementation where BW and BCS were evaluated every 30 days, and a transrectal ultrasound was performed every 15 days to determine the interval of parturition ovulation (IPO). Cows were separated in two groups and a fixed-time artificial insemination was performed (d130 and d165), followed 61 days of natural mating (d140-d175) and a gestation diagnosis 30 days after natural breeding (d231-d266) to verify the pregnancy rate (PR). Data comparison was performed by SPSS and productivity and gross margin (GM) were analyzed. We observed no difference in BCS between the beginning of prepartum until the parturition, nor in CWC, BW, IPO, and PR. The productivity and GM of RSH10 were 44.2 and 40.2% higher than RSH0 and 46.8 and 45% higher than RSH5, respectively. Thus, rice straw in the final third of gestation for cows in natural pasture allows the maintenance of cow's productive and reproductive parameters, as well as increased productivity while intensifying the system.