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.

这项研究评估了补充稻草对牛犊牛系统的影响以及增加放养率对生物经济效率的影响。比较了三种生产系统，在这些生产系统中，孕妇在产前补充了不同水平的稻草：1）9公顷（ha）天然牧场中的20头母牛没有稻草的补充，放养速度为1000公斤体重（BW） / ha（RSH0）; 2）在13.5公顷的天然牧场中，有30头母牛接受5千克稻草/动物/天和1,000千克体重/公顷的放养（RSH5）；3）在14公顷的天然牧场中放牧60头奶牛，每头动物/天的秸秆为10公斤，放牧率为2,000公斤体重/公顷（RSH10）。在第一天和每30天记录一次身体状况评分（BCS），犊牛体重（CWC）和犊牛出生体重（CBW）。产犊后Avena strigosa）和黑麦草（黑麦草），每30天评估一次BW和BCS，然后每15天进行一次直肠超声以确定分娩排卵的间隔（IPO）。将母牛分为两组，并进行固定时间的人工授精（d130和d165），然后进行自然交配61天（d140-d175），并在自然繁殖30天后（d231-d266）进行妊娠诊断以验证妊娠率（PR）。通过SPSS进行数据比较，并分析生产率和毛利率（GM）。我们观察到从分娩开始到分娩前的BCS均无差异，CWC，BW，IPO和PR也无差异。RSH10的生产率和GM分别比RSH0高44.2和40.2％，比RSH5高46.8和45％。从而，