Effect of corn residue composition on DMD of crossbred wether lambs

Abstract Text: This project was conducted to determine the digestibility of corn residue from different harvest methods. Modern harvest technologies allow the corn plant residue to be deposited in a windrow at the rear of the combine. The residue includes the husks, cobs, and some leaves that pass through the combine plus 2 to 8 rows of the stems that are cut and windrowed. In this study 4 or 8 rows of stems were windrowed, and husks were obtained from seed corn harvest. These residues were fed to 18 crossbred wether lambs (BW 26.1 kg SD 4.48 kg) over three 15 d periods. Lambs were divided into 3 blocks in a 6x3 row-column transformation with 6 treatments, 3 periods, and 3 independent squares (n=9). Lambs were fed treatment diets in an 8 d adjustment period, and total fecal collections were completed over 7 d. DM, OM, and NDF were determined for both the fecal composite of each lamb and diet components of each period. The corn stem is known to be less digestible and the corn husk most digestible relative to other plant parts.  It was hypothesized that the husk would have greater dry matter digestibility (DMD) than both 4 row and 8 row residues. It was further hypothesized that the 4 row would have greater DMD than the 8 row due to lower amount of corn stem gathered in the 4 row residue. A mixture of Sweet Bran, brome grass hay, and sheep supplement was used in all diets to supplement protein and increase palatability. During period 4, only the SB, brome, and supplement mixture was fed. Residue DMD could then be determined by difference. Husks were 17.4 percentage units more digestible than 4 row. This demonstrates that the harvest method that increases the amount of husk will increase the digestibility. The small numerical difference between 4 row and 8 row digestibility supports the hypothesis that stem decreases digestibility and husk increases digestibility. However, this was not confirmed statistically.

	Husk	4 Row	8 Row	SE	P-Value
DM Intake, %BW	1.39%	1.36%	1.39%	0.10	0.9173
DMD	68.14%a	50.74%b	48.66%b	2.0	<0.01

Keywords: lambs, corn residue, digestibility