Energy and protein content of pastures eaten by dairy cattle in New South Wales.

Abstract

Proc. Aust. Soc. Anim. Prod. Vol. 19 ENERGY AND PROTEIN CONTENT OF PASTURES EATEN BY DAIRY CATTLE IN NEW SOUTH WALES E. J. HAVILAHA, A. ANDREWSC, S. ORRC, R. TASSELLB, S. SRISKANDARAJAHC and R. KELLAWAY *NSW Agriculture, Pasture Research Unit, Berry, N.S.W. 2535. *University of Sydney, Camden, N.S.W. 2570. CUniversity of Western Sydney, Richmond, N.S.W. 2753. B Energy and protein contents of pastures selected by grazing cows determine levels of milk yield. Little published information is available on seasonal changes in these parameters for pastures actually eaten. Measurement of these changes facilitates selection of supplements. Contents of metabolisable energy (ME) and crude protein (CP) in dry matter (DM) of pastures consumed by dairy cattle were estimated monthly on dairy farms at Camden, Berry and Richmond in New South Wales. ME contents were estimated as 0.16 x digestible organic matter in dry matter (DOMD) using near infrared spectroscopsy, calibrated from samples on which DOMD was measured in vitro using cellulase and pepsin. The in vitro technique was calibrated with in vivo standards. CP was analysed as nitrogen using a Kjelfoss analyser. Nutrient contents of pasture eaten were calculated from nutrient contents of pasture samples collected before and after grazing, together with estimates of pasture mass before and after grazmg. There were strong seasonal trends in energy content and all farms were deficient in ME in summer and autumn. Pasture eaten on the Berry farm was very low in ME from December to May. CP in pasture eaten did not show a regular seasonal pattern but was consistently low at Camden where protein supplements would have been beneficial. NRC (1989). Nutrient requirements of dairy cattle 6th Edn. (National Research Council, Washington D.C.) 123