Eight multiparous Holstein cows (632±12 kg BW; 135±16 DIM) were used in a replicated 4×4 Latin square design to evaluate the effects of forage sources on rumen fermentation characteristics, performance, and microbial protein (MCP) synthesis. The forage portion of the diets contained alfalfa hay (AH), oat hay (OH), Leymus chinensis (LC), or rice straw (RS) as the primary source of fiber. Diets were isonitrogenous and isocaloric, and cows were fed four corn silages based total mixed rations with equivalent nonfiber carbohydrate (NFC) and forage neutral detergent fiber (NDF). Dry matter intake was not affected by the source of dietary forages, ranging from 18.83 to 19.20 kg/d, consequently, milk yield was similar among diets. Because of the numerical differences in milk fat and milk protein concentrations, 4% FCM and ECM yields were unchanged (p>0.05). Mean rumen pH, NH3-N content, and concentrations of volatile fatty acids in the rumen fluid were not affected by the treatments (p>0.05). Dietary treatments did not affect the total tract apparent digestibility of dry matter, organic matter, and crude protein (p>0.05); however, digestibility of NDF and acid detergent fiber in RS diet was higher compared with AH, OH, and LC diets (p<0.05). Total purine derivative excretion was higher in cows fed AH, OH, and LC diets compared with those fed RS diet (p<0.05), consequently, estimated MCP synthesis was 124.35 g/d higher in cows fed AH diet compared with those fed RS diet (p<0.05). The results indicated that cows fed AH, OH, LC, and RS diets with an equivalent forage NDF and NFC have no unfavourable effect on the ruminal fermentation and productive parameters.

This study was carried out to determine the effect of replacement of forage fiber sources from alfalfa and Leymus chinensis with nonforage fiber sources (NFFS) from dried distillers grains with solubles and corn germ meal on calves growth, rumen development and blood parameters. Forty eight female and twelve male calves (110.55±15.36) kg of body weight and 12 weeks of age) were assigned randomly to four dietary treatments (15 calves/treatment) in a completely randomized design. Experimental diets were: 0% NFFS (control), 9% NFFS (group 1), 18% NFFS (group 2), 27% NFFS (group 3), and contained equivalent neutral detergent fiber and total digestible nutrients, respectively. The dry matter intake was similar among diets, averaging 3.33 kg d-1 , and no differences were detected for body weight, withers height, body length, and heart girth. In addition, the development of rumen, reticulum, omasum, and abomasum also were similar among diets. Dry matter, crude protein, and neutral detergent fiber digestibilities increased with the increasing levels of NFFS in the experimental diets, but had no significant effect. Blood urea nitrogen, total protein, and glubulin were not affected by the dietary treatment, but group 3 resulted in the highest (P<0.05) concentrations of glucose and lowest (P<0.05) concentrations of triglycerides and albumin. In conclusion, DDGS and CGM were available and alternative fiber sources for Holstein calf diets.