Effects of feeding hay and baleage to prepubertal dairy heifers during the grower period1

Ensiled and dry forages are commonly included in growing dairy heifer diets, yet little research has compared the effects of feeding these different types of forages on dairy heifer performance. The objective of this study was to evaluate the effects of feeding baleage to dairy heifers on growth, feed efficiency, diet digestibility, and rumen parameters when transitioning to higher-forage diets during the growing period. In the 28-d transition period between arrival and the growing period, 60 Holstein heifers (141.9 ± 1.2 kg of BW) were randomly assigned to 1 of 12 pens and fed a 40% forage diet (DM basis) containing either hay or bale-age as the only forage source. Apparent digestibility of the diets was determined using 12 individually fed heifers. In the 56-d growing period, 36 heifers from the transition period remained on previous treatments and were fed a 60% forage diet (DM basis) with the same forages. In the transition period, ADG was greater for hay than for baleage (P < 0.05); however, DMI and G:F were similar between treatments. Plasma urea N was greater for hay on d 14 and 28, and rumen NH3 was greater for hay on d 14 (P < 0.01). Apparent DM, NDF, and CP digestibility were similar among treatments. In the growing period, heifers fed hay were 6.7 kg heavier than were heifers fed baleage at the conclusion of the study (P < 0.01). Heifers fed hay consumed more DM (P < 0.01) and tended to have greater G:F than did heifers fed baleage (P < 0.10). Diets containing hay resulted in greater ADG during both the transition and growing periods.