Introduction:
Baleage production has become widely accepted as a forage conservation method by dairymen in southern Mississippi and Louisiana. The most widely used forage crop for baleage production is annual ryegrass presumably because of its ease of establishment, high nutritive value and the inherently long drying time required for hay production. Many dairy producers have had good success with ryegrass baleage but have sought other forage sources to use for baleage production to offset grazing shortfalls or to supply forage for herd expansions.
Research at this unit has shown that summer perennials such as bahia and bermudagrass will store acceptably as baleage if harvested at the proper maturity stage and dry matter, but often nutritional value is low and milk production is inferior to that obtained with ryegrass baleage. Alfalfa is a premier forage crop in much of the United States, but disease and weed pressures limit stand longevity to less than three years in Louisiana. However, it may be possible to interseed some alfalfa into existing bahiagrass sods, which may improve the nutritional value of the harvested crop and at a reasonable alfalfa-establishment cost.
Another forage crop that has shown potential in plot and heifer palatability trials is brown mid rib (BMR) sorghum. When BMR sorghum is harvested in the vegetative state, lab analysis indicates digestible-energy levels approaching that of corn silage with higher protein concentrations. In addition, in recent years BMR sorghum yields have been similar to traditional forage sorghum types such as NK-300, a forage sorghum variety widely accepted by local dairymen.
Objectives: 1) To determine the value of interseeding alfalfa into bahiagrass when stored as bale silage (contrast pure bahiagrass baleage to bahiagrass baleage containing approximately 25% alfalfa). 2) To determine the milk production potential of high-digestibility sorghum bale silage (BMR) compared to high-energy corn silage, i.e. will the best-quality sorghum baleage generate milk at levels comparable to high quality corn silage?
Protocol (forages): In late fall 2005, Amerigraze 702 alfalfa was no-till planted in 12-inch rows into an existing 12-acre field of Argentine bahiagrass. Planting rate was 7 lbs of live-inoculated alfalfa seed per acre. Recommended levels of lime, phosphate, potash, sulfur and boron fertilizer were applied. In June 2006 the bahiagrass-alfalfa forage (78:22 ratio of each) was cut, allowed to field wilt 24 hours,and baled in 4x4-foot round bales. Bales were immediately wrapped in six layers of white stretch film. Another pure stand of bahiagrass was handled similarly to provide the 100% bahiagrass baleage. A 20-acre field was no-till planted (12 lbs seed/acre) in 36-inch rows to BMR 106 forage sorghum in early June 2006. Phosphate and potash were applied according to soil test, and 100 units of N fertilizer were applied. The forage sorghum was harvested approximately 8 weeks later at 4-5 feet height. Following a 48-hour drying period, the sorghum was baled and wrapped in six layers of stretch wrap.
Protocol (animals). Forty-eight lactating Holstein cows were used to evaluate the following forages 1) bahia baleage, 2) bahia-alfalfa baleage, 3) BMR-sorghum baleage and 4) corn silage (positive control). Cows were stratified based on lactation number, days in milk and daily milk yield and randomly assigned to experimental forages. Experimental forages were fed as TMRs, and diets were individually fed in the Calan Gate Research Barn. Milk production and TMR intake data were obtained daily, and milk composition and cow weights were measured weekly.
Results: The forage quality and lactation performance responses for the experimental baleage crops are presented in Table 1 (Averages with different superscript letters differ statistically). The dry-matter content of the bahia and bahia-alfalfa baleages was near the recommended 50% level, but the high moisture content of the BMR sorghum stems resulted in a relatively wet baleage crop. Protein content of the bahia interseeded with alfalfa was slightly higher, and NDF was several units lower than the pure bahiagrass baleage. The lower NDF content in bahia-alfalfa likely caused the improvement in digestibility and increased intake which translated into a 5.9-pound increase in daily milk yield. The BMR sorghum was higher in digestibility than either of the bahiagrass baleages, and milk yield followed a similar trend. The corn silage had the lowest ADF concentration, the highest digestibility and the highest TMR intake of all the ensilages, which led to the highest milk yield of all crops. In summary, alfalfa interseeding in bahiagrass improved lactation performance of Holstein cows even at modest (22%) inclusion rates, and BMR sorghum-fed cows performed at nearly the same rate as cows receiving an excellent corn silage-based TMR.
Table 1. Forage Quality and Lactation Performance Related to Ensilage Source.
|
Ensilage Crops |
|
Item |
Bahia Baleage |
Bahia-Alfalfa Baleage |
BMR Sorghum Baleage |
Corn Silage |
|
Dry matter, % |
57.2a |
52.6a |
35.2b |
29.2b |
|
Protein, % |
10.1b |
11.4c |
12.9d |
8.6a |
|
Acid detergent fiber, % |
38.4a |
37.7a |
38.8a |
24.0a |
|
Neutral detergent fiber, % |
69.5a |
64.8b |
61.7c |
41.4d |
|
Water soluble carbohydrate, % |
2.2a |
3.7a |
8.0b |
10.2b |
|
In vitro digestibility, % |
71.6a |
73.9a |
79.6b |
81.2b |
|
pH |
5.7a |
5.4a |
4.5b |
3.8c |
|
Intake, lbs dry matter/hd/d |
43.6a |
48.2c |
46.6b |
56.7d |
|
Milk yield, lbs/hd/d |
56.7a |
62.6b |
67.4c |
72.9d |
|
Milk fat, % |
3.88a |
3.92a |
3.63b |
3.82a |
|
Milk protein, % |
3.02a |
3.07a |
3.07a |
3.23b |
|
Milk urea N, mg/dl |
16.4a |
15.8a |
17.4a |
14.8b |