Effects Of Forage To Concentrate Ratio On Digestion Metabolism And Milk Fatty Acid Composition In Dairy Cows

The effects of different forage to concentrate ratio on rumen fermentation, digestion and milk production were investigated. Four ruminally and duodenally cannulated primiparous Holstein cows in mid lactation (BW: 483 21kg, DIM: 175 6d) were used in 4x4 Latin square design with 23-d each period. Diets were 30:70CW(forage was composed of Chinese wildrye,CW), 30:70CCA (forage was composed of corn silage, Chinese wildrye and alfalfa, CCA ) , 50:50CCA and 65:35CCA, respectively. Treatments had no effect (P>0.10) on degradability coefficients of feed. Efficient degradability rate of concentrate was the highest, Chinese wildrye was lowest (P<0.01). Degradability of alfalfa at 12h(P<0.05) and corn silage at 12h(P<0.10) were the lower in Diets with 30:70CW, degradability of Chinese wildrye at 4-24h was lower in 65-.35CCA diet (P<0.10) .Rumen pH value in 4-6h was lower than 6.1 and cellulose enzyme activity trended to decrease in 30:70CCA. Rumen pH value and ammonia nitrogen concentration (P<0.05) increased with decreasing forage level. Acetate concentration tended to be higher in 30:70CW (P=0.10), acetate to propionate ratio and butyrate in rumen were significantly different (P<0.01). Milk fat percentage, milk yield, milk protein percentage, and solid non-fat (SNF) were significant difference (P<0.01). DM, OM and energy intakes were lower in 30:70CCA (P<0.05) than the other treatments, Energy intake for cows fed 30:70CW was lower than for the other diets (P<0.01). Ruminal and total tract digestibility of DM, OM and Energy was lower for cows fed 30:70CW diets than the other diets (PO.05). No differences were detected (P>0.10) in digestibility of NDF and ADF. Eating time and chewing time in 30:70CCA were longer than other diets (P<0.01); 65:35CCA had decreased eating time, ruminanting, chewing time (P<0.01) and Chewing time unit DM/NDF per day (P<0.05). Range of peNDF intake was 17.71% to 37.32% of DM.Fatty acid intakes were significantly different in the treatments (P<0.01). Flow of trans-C18:1 to the duodenum was higher 65:35CCA (P<0.10) than other diets. Biohydrogenation rate of C18:1 in rumen reduced dramatically in cows fed 30:70 CCA diets (P<0.01). The Cows fed 30:70(CW and CCA) diets had lower extent of biohydrogenation cis-C18:1 compared with 50:50CCA and 65:35CCA (PO.01). Biohydrogenation rate C18:2, C18: 3 and total unsaturated C18 FA was not affected by treatment (P>0.05). Biohydrogenation rate of cis-C18:1 was lower compared with C18:2, C18:3. The concentration of C14:1(P<0.05), trans-C18:1 (P<0.10) FA in milk was higher for cows fed 65:35CCA diet. C,6:0 concentration was lower for cows fed 65:35CCA than the other diets. Percentage of saturated fatty acids and unsaturated (mono/poly unsaturated) fatty acids were different among feed, duodenal digesta, feces and milk.