Corine Bayourthe

Avoparcin and monensin effects on digestive function in cows fed a high forage diet

Three non-lactating cows with ruminal, duodenal, and ileal cannulas were used in a 3 x 3 Latin square design to evaluate the effect of oral avoparcin and monensin on fibre, starch, and nitrogen (N) digestion. Cows were fed three high forage diets ; the control diet had no additive, and the others contained 33 mg kg -1 DM of either avoparcin or monensin. Neither additive affected apparent total tract digestibilities of organic matter, fibre, starch or N. Avoparcin and monensin reduced the ruminal breakdown of fibre, starch and dietary N. Efficiency of bacterial N synthesis was unchanged, and passage of bacterial N to the small intestine was not modified. Compared with the control, additives caused a greater proportion of feed starch, N, and total amino acid to be digested in the small intestine than in the rumen. Diets containing avoparcin or monensin increased availability of total essential amino acid in the small intestine compared with that of control diets. Post-ruminal digestion of fibre was greater for diets supplemented with antibiotics, because the cows compensated digestion in the lower forestomach.

Effect of extruded lupin seeds as a protein source on lactational performance of dairy cows

Twelve multiparous and eight primiparous Holstein dairy cows, averaging 70 days in milk, were used to examine the effect on feed intake and lactational performance of replacing a conventional protein supplement by extruded lupin seeds (ELS). The diets were composed of 68% forage (corn silage and alfalfa hay) and 32% concentrate on a dry matter (DM) basis. In the control diet (C), the protein supplement supplied 34% of total crude protein; in the ELS diet, lupins provided 40% of total crude protein. Cows were fed twice daily during the experimental period (14 weeks). Total dry matter intake (DMI) was lower (P<0.05) with the inclusion of ELS (21.3 vs. 21.6 kg day−1). The ELS diet increased milk yield (36.0 vs. 32.6 kg day−1) and lowered milk protein (2.80 vs. 3.00%). Milk fat content and yields of fat and protein were not affected by the treatment. Daily body weight (BW) gain averaged 0.55 kg for the ELS diet which was not different from the 0.45 kg for the C diet.

Effect of particle size on in situ ruminal disappearances of pea (Pisum sativum) organic matter, proteins and starch in dairy cows.

Ruminal disappearance characteristics of OM, CP and starch relative to particle size of dehulled pea seeds were determined using the in sacco method. Fine grinding (≤502 µm) highly increased the rapidly CP and starch degradable fractions and the rate of degradation of these nutrients. Key words: Pea flour, particle size, rumen degradation, crude protein, starch