Effects of urea-calcium mixture in concentrate containing high cassava chip on feed intake, rumen fermentation and performance of lactating dairy cows fed on rice straw

摘要

New rumen slow-release urea products were made by mixing urea with calcium chloride (U-Cal) or calcium sulphate (U-Cas) in concentrate mixtures containing a high level of cassava chip and were subsequently evaluated on feed intake, rumen fermentation, rumen microbes, microbial protein synthesis, and performance of lactating dairy cows. Three, multiparous Holstein crossbred dairy cows in early-lactation with an initial body weight of 380 15 kg were randomly allocated to 3 dietary treatments of UCM products [T1 = urea (control); T2 = urea-CaCl2 mixture product (U-Cal); and T3 = urea-CaSO4 mixture product (U-Cas)1 according to a 3 x 3 Latin square design. Each experimental period lasted for 21 days during which feeds, rumen fluid, and blood were collected as well as milk yield. The findings revealed significant improvements in intake of OM and ME and apparent digestibilities of OM and NDF by using U-Cas in concentrate diets (P<0.05). Ruminal NH3-N and blood urea N in U-Cal and U-Cas, were found significantly lower as compared with the urea supplemented group (P<0.05), while milk urea nitrogen resulted in normal ranges. Volatile fatty acid concentrations especially those of propionic acid were increased (P<0.05) in cows fed with U-Cas products than those in other treatments. Total viable bacteria, fungal zoospores, and cellulolytic bacteria were significantly different among treatments and were greatest in U-Cas supplementation (8.5 x 10(11), 8.1 x 10(4), and 2.1 x 10(9) cfu/mL, respectively). Moreover, the use of real-time PCR technique provided that the population of Fibrobacter succinogenes was relatively higher than those of Ruminococcus flavefaciens and Ruminococcus albus. Efficiency of rumen microbial N synthesis based on OM truly digested in the rumen was enriched by U-Cas supplementation. Milk yield was additionally increased by respective treatments, while 3.5% fat-corrected milk was highest; ranking from U-Cas, U-Cal, and urea alone treatment fed groups, respectively. Based on this study, it could be concluded that supplementation of U-Cas in concentrate supplementation containing a high level of cassava chip significantly improved apparent digestibility, rumen fermentation, and milk yield in lactating dairy crossbreds fed on rice straw