Soares Letícia Carolina Bortolanza, Marques Rodrigo S, Vaz Pires Alexandre, Cruz Vinicius Alves, Limede Arnaldo Cintra, Maia Kauê Dos Santos, Baggio Marcelo, Barroso José Paulo Roman, Biava Janaina Sokolovski, Maia Ferreira Evandro, Ferraz Marcos Vinicius de Castro, Polizel Daniel Montanher
Department of Nutrition and Animal Production, FMVZ, University of São Paulo, Pirassununga, SP 13635-000, Brazil.
Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA.
Transl Anim Sci. 2021 Jul 21;5(3):txab125. doi: 10.1093/tas/txab125. eCollection 2021 Jul.
The study aimed to evaluate if the frequency of narasin supplementation impacts dry matter intake, ruminal fermentation parameters, and apparent digestibility of nutrient in Nellore () steers fed forage-based diets. A total of 32 rumen-cannulated Nellore steers (initial body weight [BW] = 317 ± 27 kg; age =18 ± 1 mo) were assigned to individual pens in a randomized complete block design according to their initial shrunk BW. Within block, steers were randomly assigned to 1 of 4 treatments: 1) forage-based diet without the addition of narasin (CON; = 8), 2) CON diet plus 13 ppm of narasin every 24 h (N24; = 8), 3) CON diet plus 26 ppm of narasin every 48 hours (N48; = 8), or 4) CON diet plus 39 ppm of narasin every 72 hours (N72; = 8). The experimental period lasted 30 d, with 18 d for diet adaptation and 12 d for sample collection. The experimental diets contained 95% of Tifton-85 ( spp.) haylage and 5% ground corn used as a delivery vehicle for narasin. Ruminal fluid was obtained from d 25 to 30 at 6 h after feeding to determine ruminal fermentation parameters. Narasin supplementation frequency did not affect ( ≥ 0.22) nutrient intake and total tract apparent digestibility. Steers fed N24 and N48 had reduced ( = 0.02) ruminal acetate concentration compared with CON and N72. Daily supply of narasin increased ( = 0.01) the molar proportion of propionate compared with CON and N72, and it did not differ between N24 vs. N48, N48 vs. N72, and N72 vs. CON. Also, N48 steers had greater ( = 0.01) rumen propionate concentration compared with CON. The N24 treatment decreased the Ac:Prop ( = 0.01) and AcBut:Prop ( = 0.02) ratio compared with CON and N72, while N48 had reduced ( = 0.01) Ac:Prop and AcBut:Prop ratio when compared with CON steers. Steers fed N24 and N48 had greater ( = 0.04) ruminal short-chain fatty acids compared with CON, but it did not differ ( 0.11) between N24, N48, and N72. Supplementing narasin to steers fed forage-based diets decreased ( < 0.01) ruminal ammonia concentration compared with CON steers regardless of supplementation frequency, being the least result observed for N24 steers. Collectively, narasin supplementation frequency affected fermentation parameters without altering the nutrient intake and total tract apparent digestibility. Hence, decreasing frequency of narasin supplementation to Nellore steers fed a forage-based diet did not reduce the capacity to modulate rumen fermentation parameters.
本研究旨在评估纳拉辛补充频率对以粗饲料为基础日粮饲养的内洛尔阉牛干物质采食量、瘤胃发酵参数和养分表观消化率的影响。总共32头安装有瘤胃瘘管的内洛尔阉牛（初始体重[BW]=317±27千克；年龄=18±1月龄）根据其初始收缩体重，以随机完全区组设计分配到各个栏舍。在每个区组内，阉牛被随机分配到4种处理中的1种：1）不添加纳拉辛的以粗饲料为基础的日粮（对照组；n=8），2）对照组日粮加每24小时13 ppm纳拉辛（N24；n=8），3）对照组日粮加每48小时26 ppm纳拉辛（N48；n=8），或4）对照组日粮加每72小时39 ppm纳拉辛（N72；n=8）。试验期持续30天，其中18天用于日粮适应，12天用于样本采集。试验日粮包含95%的蒂夫顿85（雀稗属）青贮料和5%的玉米粉，后者用作纳拉辛的载体。在饲喂后6小时从第25天至30天采集瘤胃液，以测定瘤胃发酵参数。纳拉辛补充频率对养分摄入量和全消化道表观消化率没有影响（P≥0.22）。与对照组和N72相比，饲喂N24和N48的阉牛瘤胃乙酸浓度降低（P=0.02）。与对照组和N72相比，纳拉辛的每日供应量增加了丙酸的摩尔比例（P=0.01），且在N24与N48、N48与N72以及N72与对照组之间没有差异。此外，与对照组相比，N48阉牛的瘤胃丙酸浓度更高（P=0.01）。与对照组和N72相比，N24处理降低了乙酸：丙酸（P=0.01）和乙酸丁酸：丙酸（P=0.02）比例，而与对照组阉牛相比，N48的乙酸：丙酸和乙酸丁酸：丙酸比例降低（P=0.01）。与对照组相比，饲喂N24和N48的阉牛瘤胃短链脂肪酸含量更高（P=0.04），但在N24、N48和N72之间没有差异（P>0.11）。无论补充频率如何，与对照组阉牛相比，给以粗饲料为基础日粮的阉牛补充纳拉辛均降低了瘤胃氨浓度（P<0.01），N24阉牛的结果最低。总体而言，纳拉辛补充频率影响发酵参数，但未改变养分摄入量和全消化道表观消化率。因此，降低给以粗饲料为基础日粮的内洛尔阉牛补充纳拉辛的频率不会降低调节瘤胃发酵参数的能力。
