Growth performance and total tract nutrient digestion for Holstein heifers precision-fed diets high in distillers grains with different forage particle size

Abstract Text: This study evaluated dairy heifer growth performance and total tract nutrient digestion when fed diets high in dried distillers grains with solubles (DDGS) with different forage particle size, achieved by utilizing alfalfa hay that was processed differently. An 8-wk randomized complete block design study was conducted using twenty-two Holstein heifers (123±32 d of age; initial body weight (BW) of 140±23.5 kg). Treatments were either 15% chopped (CHOP) or 15% pelleted (PELL) alfalfa hay on a dry matter (DM) basis. Both diets also contained 30% DDGS, 53.75% corn silage, and 1.25% mineral mix. Rations were precision-fed for a dry matter intake (DMI) of 2.3% of BW. Frame sizes, BW, and body condition scores (BCS) were taken on two consecutive days during wk 0, 2, 4, 6 and 8. During wk 8, titanium dioxide was fed and fecal grab samples were collected to measure total tract nutrient digestion.  Heifer DMI increased (P<0.01) when fed CHOP versus PELL (4.42 and 4.19 kg/d for CHOP and PELL, respectively). Body weights (167.4 and 164.0 kg) and average daily gain (0.83 and 0.96 kg/d) were similar (P>0.05) between treatments. Gain to feed was less (P<0.01) in CHOP versus PELL (0.21 and 0.25). Hip height (110.7 and 110.9 cm), wither height (106.7 and 106.6 cm), and body length (95.1 and 94.9 cm) were similar between treatments. Paunch girth (153.6 and 150.4 cm), heart girth (122.4 and 120.4 cm), and hip width (30.2 and 29.6 cm) were greater (P<0.05) for CHOP versus PELL. Body condition score was less (P<0.01) for CHOP compared to PELL (3.03 and 3.09). For growth measurements there were no significant treatment by week interactions or differences in average daily changes. Total tract digestibility of DM (67.5 and 67.3 %), neutral detergent fiber (51.2 and 50.1 % of DM), and crude protein (68.3 and 67.9 % of DM) were similar between treatments. Heifers fed diets containing 30% DDGS with 15% chopped or pelleted alfalfa hay had similar total tract nutrient digestion and growth performance, with some very minor differences in frame growth and feed to gain. Overall, this study demonstrated that feeding dairy heifers diets with different forage particle sizes, achieved by inclusion of chopped or pelleted alfalfa hay, does not affect utilization of DDGS.

Keywords: dairy heifer, distillers grains, particle size