The objective of this study was to evaluate alkali treatment of whole plant corn and stalks fractionated from the whole plant at harvest as feeds for lactating dairy cows. A forage harvester with a 6-row modified ear-snapping head was setup to snap the corn ear from 2 rows and cut 4 rows at a height of 82 ± 5cm, resulting in a feed product called toplage. The toplage used in this study was 82% of the DM yield from the field and contained 44% starch. The remaining stalks were harvested with a forage harvester at a height of 12 ± 2 cm on a second pass. Stalks were treated with calcium hydroxide at a rate of 70 g·kg⁻¹ DM and ensiled. A second treatment was comprised of whole plant corn harvested at 28 ± 3cm and treated with calcium hydroxide at a rate of 70 g·kg⁻¹ DM, then ensiled. Conventional corn for the negative control diet (CON) was harvested at 26 ± 3cm from the same fields. BMR corn for the positive control diet was harvested from an adjacent field at a height of 26 ± 5cm. One hundred twenty-eight Holstein cows were stratified among 4 treatments in a randomized complete block design. Data were analyzed using the MIXED procedure of SAS, with treatment, week, and relevant interactions as fixed effects. Diets were TMR containing 40% corn silage, 20% alfalfa silage, and 40% concentrate. Treatments were complete substitution of corn silage with a negative control (CON), positive control (BMR), treated whole plant (TRTCS), and a combination of toplage (82% of corn silage) and stalklage (18% of corn silage) (TOP). The TOP and BMR diet resulted in a similarly increased ECM over the CON diet (P < 0.01), and the TRTCS resulted in the highest ECM. Table 1. Effects of treatment on DMI, production, and rumination

Item	CON	BMR	TOP	TRTCS	SED	P-value
DMI	23.6c	24.2bc	24.8ab	25.5a	0.5	0.02
Milk, kg·d−1	43.1b	47.1a	45.6a	48.0a	1.0	<0.01
Fat, %	3.40	3.30	3.32	3.37	0.13	0.84
Fat, kg·d−1	1.47b	1.55b	1.54b	1.66a	0.05	<0.01
Protein, %	2.97a	2.96a	2.94a	2.84b	0.04	0.02
Protein, kg·d−1	1.29b	1.40a	1.38a	1.39a	0.03	<0.01
ECM	41.9c	45.0b	44.7b	47.0a	0.8	<0.01
ECM DMI−1	1.79	1.85	1.77	1.83	0.04	0.31
BW change, kg·wk−1	0.30	0.29	0.36	0.35	0.23	0.99
BCS	2.79	2.80	2.86	2.84	0.03	0.26
Rumination, min·d−1	510a	474bc	487ab	459c	10	0.01