Effects of dietary n-3 polyunsaturated fatty acids and ... - FINS

1 st WorkshopXIII International Feed Technology Symposiumincreasing milk yield, there were no effect on milk fat percentage, until total time ofchewing activity (intake and rumination) were significantly greater.Effects of chop length of forage and particle size of total mixed rations for lactatingcows on milk fat content, appears when content of NDF is under minimal requirement,(25% NDF, and 19% forage NDF in dietary DM, NRC,2001).Using of fine chopped alfalfa haylage (2.1 mm, theoretical chop length 0.48 cm) insteadof coarse chopped haylage (3.1 mm, theoretical chop length 0.95 cm) in TMR (forage toconcentrate 55:45 % in dietary DM) for Holstein cows in early lactation (3-8 weeks),depressed milk fat content (3.8 and 3.0 %), decreased daily yield of 4 % FCM, as alsofeed conversion (Grant et al. 1990). Rumination time and total chewing time weresignificantly decreased, as also ruminal pH and acetate to propionate ratio. It wasdetermined increasing of glucose and insulin concentration in blood plasma and serum.Table 3. Effects of different chop length of alfalfa haylage in TMR, on somephysiological and production parameters of cows in early lactation (Grant etal. 1990)ItemChop lengthFine Middle CoarseIntake of DM, kg/day 22.4 22.0 22.24% FCM, kg/day 27.52 30.28 29.49Milk fat, % 3.0 3.6 3.8Milk protein, % 3.0 3.0 3.1Chewing activity, min/24 hIntake 195.3 204.4 204.7Rumination 374.4 466.3 530.7Total chewing activity 569.7 670.7 735.4pH 5.3 5.9 6.0VFA, mM/lAcetic 73.96 70.61 76.29Propionic 39.19 30.80 26.09Butyric 8.78 15.05 17.47Acetate : Propionate 2.77 3.13 3.52Glucose in blood plasma, mg/dl 65.9 54.0 44.9Insulin in blood serum, ng/ml 0.30 0.26 0.20Rustomo et al. (2006) reported that increasing chop length of corn silage and alfalfahaylage in ratio that characterized higher acidity potential of his concentrate part,showed tendency of increasing milk fat content by 0.32 % (3.87 and 4.19 %). Using finechopped alfalfa haylage (3.02 mm) instead of coarse chopped alfalfa haylage (9.57 mm)in TMR for primiparous cows in early lactation, decreased milk fat percentage (3.73 and3.41 %), as also production of 4 % FCM (26.54 and 24.81 kg/day). The same effect ofdepressed milk fat was determined for multiparous lactating cows (3.69 and 3.49 %),(Fischer et al. 1994).Although intake of diet with deficit of effective fiber cause disturbance of ruminalfunction, and ruminal fermentation, excessive content of long and coarse forage particles225