Orchardgrass versus Alfalfa for Lactating Dairy Cattle: Production, Digestibility and Nitrogen Balance

Abstract

Jonker, J.S., Cherney, D.J.R., Fox, D.G., Chase, L.E. and Cherney, J.H. 2002. Orchardgrass versus alfalfa for lactating dairy cattle: production, digestibility and nitrogen balance. J. Appl. Anim. Res., 21: 81–92.

Effects of forage fiber source on milk production, digestibility and nitrogen balance were studied for three hay forages: early bloom alfalfa (ALF), early bloom orchardgrass (OG-E) and late bloom orchardgrass (OG-L). Multiparous mid-lactation Holstein cows were used in a 3x3 Latin square design replicated four times (12 cows) for the production trial and replicated three times (9 cows) for in vivo digestibility and nitrogen balance. Cows were fed one of three isonitrogenous and isocaloric rations containing 9.5 g kg⁻¹ NDF per kg BW from forage. Cows consumed similar quantities of NDF (14.7±0.8g kg⁻¹ BW) and the ALF, OG-E and OG-L diets produced 29.1, 30.1 and 32.5 kg d⁻¹ of milk, respectively. Apparent digestibility for NDF and DM was higher for the orchardgrass rations than the alfalfa based ration. Higher N intake resulted in higher N output in both urine and milk, but N excretion in feces was not different between diet treatments. Efficiency of conversion of N to milk was 25.9%. Home grown forage accounted for 78.8% of N in the ALF diets, while only 47.8% and 22.7% of N came from OG-E and OG-L, respectively. Balanced orchardgrass dairy rations can be well utilized by lactating dairy cattle and can clearly have a place in nutrient management systems, provided grass is harvested at a high yield and quality.

Key words:

• Neutral detergent fiber
• orchardgrass
• digestibility
• nitrogen balance