Evaluation of Hay Feeding Strategies on Feed Sorting Behavior of Dairy Heifers Fed Mock Lactation Diets

Five different physical methods of incorporating hay into mock lactating dairy cow diets were developed to explore possible differences in nutrient intake and feed sorting behavior. Diets were fed to 80 gravid Holstein heifers (433 ± 39 kg) that were randomly assigned to 10 pens in a 5 x 5 Latin square experimental design. Experimental diets included 1) incorporation of long hay (LH) in a total mixed ration (TMR) mixer; 2) incorporation of bale cut hay (BC) in a TMR mixer; 3) incorporation of chopped hay (CH) in a TMR mixer; 4) top-dressing (TD) LH without TMR incorporation, and 5) TD BC hay without TMR incorporation. Top-dressing LH (P < 0.10) or BC hay (P < 0.02) to heifers resulted in a suppression (0.5 kg/d) of DMI as compared with heifers fed TMR diets in which hays were incorporated in the TMR. Heifers fed TD diets refused (P < 0.002) particles approximately 10 mm longer than heifers fed diets where hays were incorporated in the TMR. The greatest particle sorting occurred for particles retained on screens >6.35 mm, indicating that heifers preferred particles of smaller size. When a TMR mixer capable of incorporating LH is available, fully incorporating LH in the diet resulted in greater DMI and less particle sorting by heifers. In situations where a TMR mixer is incapable of incorporating LH, using BC in a TMR produced similar and acceptable results. Trial results indicate that feed intake and feed sorting behaviors are influenced by dietary hay incorporation methods.