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Effect of Harvest Date on Meadow Hay Quality. I. Nutritional Attributes, Voluntary Intake and Rate of Passage in Growing Cattle¹

University of Nebraska⁴, North Platte 69101

Abstract

Six ruminal-cannulated (Angus x Hereford) steers (average initial weight 340 kg) were fed Sandhills meadow hay harvested from initial growth of a mixture of native cool- and warm-season species at three different times during the growing season (June, August or September). Steers were randomly assigned to one of two 3 x 3 Latin squares with each of the squares replicated in time. Steers were given ad libitum access to the hays in an intake trial in which voluntary intake was measured. Additionally, rate of passage, pool size, retention time of forage particles of differing sizes [1,680 µm (1,680), 850 but <1,680 µm (1,680/850), and <850 µm (850)] and in vitro organic matter and neutral detergent fiber disappearance were measured. Digestible organic matter intake decreased (74.71 to 50.96 g/kg body weight⁷⁵; P<.01) from the early to the later harvests. Rate of passage estimated by a time dependent-time independent model tended to decrease with advancing forage maturity for the larger particles (1,680 and 1,680/850) and was significant (P<.1) for the 850 particles. Pool sizes of the three particle groups estimated from a time-dependent model increased (P<.05) from the June to the September harvest. Estimations of pool sizes from a two-compartmental model showed similar (P<.1) trends but tended to be smaller than those estimated by the one-compartmental model. Retention times of the three particle groups were less (P<.05) for the June harvest than for the later harvests when estimated from either the one- or two-compartmental model. The data collected in this study support the concept of declining quality with advancing plant maturity and suggest that model parameters derived from mathmetical descriptions of ruminal dynamics are sensitive to chanages in forage quality and may be useful in the characterization of forage quality.

¹ Journal paper no. 7907 Univ. of Nebraska Agr. Exp. Sta.

² Present address: Edisto Res. and Educ. Center, Clemson Univ., Blackville 29817.

³ Dept. of Biometrics, Univ. of Nebraska, Lincoln 68583.

⁴ West Central Res. and Ext. Center.