Animal Science Journal (2005) 76, 387–390 387 Blackwell Science, LtdOxford, UKASJAnimal Science Journal1344-39412005 Blackwell Publishing Asia Pty LtdAugust 2005764387390Original Article Effect of the last diet on food selectionM. Fukasawa et al. Correspondence: Michiru Fukasawa, National Institute of Livestock and Grasslands Science, Nasushiobara-shi, 329- 2793, Japan. (Email: shakecat@affrc.go.jp) *Present address: School of Agriculture, Ibaraki University, Ami-machi, Ibaraki-ken, 300-0393, Japan Received 21 December 2004; accepted for publication 2 March 2005. ORIGINAL ARTICLE Effect of the last diet on the selective feeding behavior of heifers Michiru FUKASAWA, Hideharu TSUKADA, Takami KOSAKO and Daisuke KOHARI National Institute of Livestock and Grasslands Science, Nasushiobara-shi, Japan ABSTRACT The present study examined and discussed the way the basal diet (BD) during the preliminary phase and the last diet (LD) before the food selection test affected the selective feeding behavior of heifers. For the BD and LD, oat hay and concen- trate were used. Three different levels of roughage content (low, medium and high) were prepared by changing the mix ratios of oat hay and concentrate. Low and high roughage diets were used for the BD, and all three of the roughage levels were used for the LD. A mixture of orchard grass and white clover (MIX), and Japanese pampas grass leaf (JP) were used as testing foods. In the preliminary phase, all heifers were fed the BD three times per day. In the test phase, heifers were fed the LD for the first meal (06.00–12.00 hours), and food selection under different BD and LD was examined during the second meal (13.00–16.00 hours) of the day. The effects of the BD were significant for MIX dry matter intake (DMI), JP DMI and the rate of MIX DMI for total DMI. Under the high roughage BD condition, heifers ingested more MIX than under the low roughage BD condition. The effect of the LD was significant on JP DMI, whereas the rate of MIX DMI for total DMI was not significant. Selective feeding behavior was strongly affected by the BD and slightly by the LD. KEYWORDS: basal diet, cattle, last diet, selective feeding behavior. INTRODUCTION A better understanding of the selective feeding behav- ior of ruminants will improve animal production. Foods containing inadequate or excessive levels of nutrients may be avoided more strongly in the follow- ing meal than foods containing adequate nutrients (Provenza 1996). Villalba and Provenza (1999) insisted that animal-state dependent food choice should also be considered for a better understanding of selective feeding behavior. Ruminants eat various foods to meet their physiological requirements (Westoby 1978; Kyriazakis & Oldham 1993). Wang and Provenza (1996) hypothesized that selec- tive feeding behavior is affected by aversion, which is the decrease in the preference for a food as a result of sensory inputs (taste, odor, texture) and postingestive effects (nutrients and toxins on chemoreceptors, osmoreceptors and mechanoreceptors). Even when a nutritionally balanced diet is eaten to satiety, it may result in an aversion and ruminants will seek another diet (Early & Provenza 1998). Sheep (Wang & Provenza 1996) and calves (Fukasawa et al. 2005) pre- fer foods that complement the macronutrient compo- sition of their basal diet (BD). Parsons et al. (1994) also suggested that a recent diet could exert lasting effects on the selective feeding behavior of ewes. Provenza (1996) suggested that lambs develop a transient aver- sion to food eaten in the last diet. All of these results demonstrate that the selective feeding behavior of ruminants may be affected not only by long-term diet conditions but also by short- term diet conditions. In the present study, we exam- ined and discussed how the BD and the most recent previous diet affected the selective feeding behavior of heifers.