Warner Andrea L, Beck Paul A, Foote Andrew P, Pierce Kaitlyn N, Robison Colton A, Stevens Nicole E, Wilson Blake K
Department of Animal and Food Sciences, Oklahoma State University, Stillwater, OK.
J Anim Sci. 2020 Sep 1;98(9). doi: 10.1093/jas/skaa257.
Cotton byproducts can be an economical source of protein, fat, and fiber in cattle finishing diets. The objectives of this study were 1) to assess the effects of including whole cottonseed (WCS) and cotton gin trash (CGT) in finishing diets on in situ ruminal degradability and 2) to determine the effects of including cotton byproducts in a finishing diet on rumen fluid pH, lactate, and volatile fatty acid concentrations. Six ruminally cannulated steers were used in a crossover design. Treatments included a control diet (CON; 7% prairie hay [PH], 15% Sweet Bran, 67.25% rolled corn, and 5% liquid supplement) and a cotton byproduct diet (CTN; 7% CGT, 15% WCS, 72.25% rolled corn, and 5% water). Both diets included 0.75% urea and 5% dry supplement. In situ bags containing individual diet ingredients and whole diet samples were incubated in the rumen for up to 96 h. Rumen fluid samples were collected over a 24-h period. No treatment × substrate interactions were detected for any fraction of dry matter (DM) or organic matter (OM) degradability for individual ingredients or whole diets (P ≥ 0.14). The A, B, and C fractions, disappearance rate (Kd), and effective degradability of DM and OM differed between diet ingredients (P ≤ 0.04) but were not different between CON and CTN substrates (P ≥ 0.25). A treatment × substrate interaction (P = 0.04) was detected for the effective degradability of neutral detergent fiber (NDF) of CGT and PH but there was no interaction for other fractions (P ≥ 0.27). The A fraction of NDF was greater (P < 0.001) for CGT than PH; however, the B fraction of NDF tended to be greater (P = 0.08) for PH than CGT. No differences (P ≥ 0.37) were detected for the % NDF disappearance at 48 h between CON and CTN substrates. A tendency for a treatment × substrate interaction (P = 0.10) was observed for the effective degradability of starch among diets; however, when the CON substrate was incubated in steers consuming the CON diet, effective degradability of starch was not different (P = 0.84) from when the CTN diet was incubated in steers consuming the CTN diet. There was no treatment × time interaction or treatment effect for rumen pH; however, there was a time effect (P = 0.03). Steers consuming the CTN diet had greater molar proportions of acetate and decreased molar proportions of propionate compared with CON steers (P < 0.01). This experiment suggests that there are minimal differences between the digestibility of finishing diets containing cotton byproducts and those comprised of traditional finishing diet ingredients.
棉副产品可以成为肉牛育肥日粮中蛋白质、脂肪和纤维的经济来源。本研究的目的是：1）评估在育肥日粮中添加全棉籽（WCS）和棉籽壳（CGT）对瘤胃原位降解率的影响；2）确定在育肥日粮中添加棉副产品对瘤胃液pH值、乳酸和挥发性脂肪酸浓度的影响。采用交叉设计，选用6头装有瘤胃瘘管的阉牛。处理组包括对照日粮（CON；7%的苜蓿干草[PH]、15%的甜麸皮、67.25%的压片玉米和5%的液体补充料）和棉副产品日粮（CTN；7%的CGT、15%的WCS、72.25%的压片玉米和5%的水）。两种日粮均含有0.75%的尿素和5%的干补充料。将装有各日粮成分和全日粮样本的原位袋在瘤胃中孵育长达96小时。在24小时内采集瘤胃液样本。对于单个成分或全日粮的干物质（DM）或有机物（OM）降解率的任何部分，均未检测到处理×底物相互作用（P≥0.14）。日粮成分之间的DM和OM的A、B和C组分、消失率（Kd）和有效降解率不同（P≤0.04），但CON和CTN底物之间没有差异（P≥0.25）。检测到CGT和PH的中性洗涤纤维（NDF）有效降解率存在处理×底物相互作用（P = 0.04），但其他组分没有相互作用（P≥0.27）。CGT的NDF的A组分高于PH（P < 0.001）；然而，PH的NDF的B组分往往高于CGT（P = 0.08）。CON和CTN底物在48小时时的NDF消失百分比没有差异（P≥0.37）。日粮之间淀粉的有效降解率观察到有处理×底物相互作用的趋势（P = 0.10）；然而，当CON底物在采食CON日粮的阉牛中孵育时，淀粉的有效降解率与在采食CTN日粮的阉牛中孵育CTN日粮时没有差异（P = 0.84）。瘤胃pH值没有处理×时间相互作用或处理效应；然而，存在时间效应（P = 0.
