Corn Silage vs Alfalfa for Dairy Cattle: What Each Feed Actually Does

The short version

Corn silage supplies energy. Alfalfa supplies protein, calcium and effective fibre. Neither is a complete forage on its own.

• Feed only corn silage and you are short of protein, short of calcium, and you will buy both in from concentrates and minerals.
• Feed only alfalfa and you are short of fermentable energy. Rumen ammonia climbs, nitrogen is excreted rather than converted into milk, and you pay for protein you never capture.
• Feed both and each covers the other's gap. That is why the standard high-producing dairy ration in most of the world uses a corn silage base with a legume forage alongside it.

The rest of this article is the evidence for that.

What each feed actually is

Corn silage: an energy and starch feed

Corn silage is the whole maize plant — stover, cob and grain — chopped at around 30-35% dry matter and fermented. The grain is still on the plant, so roughly a third of the dry matter is starch. That starch is what makes it an energy feed.

Harvest timing controls almost everything. Feedipedia's guidance is that maize forage should be cut at 30-35% dry matter, with the milk line of the grain between one third and two thirds down from the top of the kernel. Below 30% dry matter, the risk of bacterial and fungal spoilage rises and dry matter, sugars and protein are lost in leachate. Penn State Extension puts the half milk line stage at around 66% moisture — 34% dry matter — with whole-plant digestibility averaging 80% and crude protein around 9.2% at that stage.

Penn State also make the point that matters agronomically: corn silage produces more energy per acre than any other crop grown in Pennsylvania. The same holds in most maize-growing regions, including Punjab. If your constraint is energy per acre of land or per acre-foot of water, maize silage is hard to beat.

Alfalfa (lucerne): a protein, fibre and mineral feed

Alfalfa is a perennial legume, cut several times a year, dried and baled. It fixes its own nitrogen, which is why it carries two to three times the crude protein of corn silage. It is also very high in calcium.

The trade-off is energy. Alfalfa stems lignify quickly as the plant matures. Feedipedia records organic matter digestibility falling from 77% at the vegetative stage to 60% at flowering. Cut it late and you have bulk, not feed. This is why alfalfa hay is the most variable feed most dairies buy — published crude protein spans 11.3% to 25.3% of dry matter across samples. "Alfalfa" on an invoice tells you very little on its own.

Side-by-side composition

All values below are general published averages and ranges from Feedipedia (INRAE, CIRAD, AFZ and FAO), for maize silage in the 30-35% dry matter category and for alfalfa hay. They are industry reference values, not measurements of any particular consignment.

Both figures come from the same database and the same methodology, so the energy comparison is like for like.

Reading the table: five things that matter

1. Energy

Corn silage carries 10.8 MJ ME/kg DM against 8.4 for alfalfa hay. That is about 29% more metabolisable energy per kilogram of dry matter. Organic matter digestibility is 71.7% against 61.8%. On energy, corn silage wins clearly, and it wins on land and water use too because it packs that energy into a single 100-120 day crop.

2. Protein — and what kind

Alfalfa carries 18.2% crude protein against 6.9%. That is 2.6 times as much. It is also better quality nitrogen: 72% nitrogen digestibility against 55-66% for corn silage.

But alfalfa protein is highly rumen-degradable. Feedipedia records nitrogen degradability at 79% at a passage rate of 6%/h. In plain terms, most of alfalfa's protein is broken down to ammonia in the rumen within hours. If there is no fermentable energy arriving at the same time, the rumen bugs cannot build that ammonia into microbial protein. It is absorbed, converted to urea in the liver, and passed out in urine. You bought it and you threw it away.

This is the single most important point in this article. Corn silage starch is exactly the fermentable energy that captures alfalfa ammonia. That is not a theory — the trial data below show it directly.

3. Fibre looks similar; it is not

NDF is almost identical: 44.3% against 44.8%. Do not read that as equivalence.

Alfalfa's fibre is far more lignified — 7.6% lignin against roughly 3% — and its ADF is much higher at 33.4% against 23.3%. Lignin is indigestible. So alfalfa NDF is less digestible overall. What it does do is ferment and clear the rumen faster than grass-type fibre, and it is usually fed in longer particles, so it stimulates chewing and rumination well. That is physically effective fibre, and it is what keeps rumen pH stable on a high-starch diet.

Corn silage fibre is more digestible but shorter and softer. A ration built heavily on corn silage with a fine chop can end up low on effective fibre even while total NDF looks fine on paper.

4. Starch

Corn silage carries around 29% starch. Alfalfa carries essentially none. Starch drives propionate production, glucose supply and milk volume. It also drives rumen acidosis risk if you overdo it, and it depresses milk fat.

5. Calcium

Alfalfa carries 16.8 g/kg DM calcium — 1.68% of dry matter. Corn silage carries 1.9 g/kg — 0.19%. That is nearly a nine-fold difference.

The arithmetic matters. Alfalfa at 20% of ration dry matter contributes about 0.34 percentage points of calcium to the ration. Corn silage at 40% of ration dry matter contributes about 0.08. A corn silage-based ration needs bought-in calcium; an alfalfa-based one often does not.

The reverse applies to dry cows. High-calcium, high-potassium alfalfa is normally restricted in close-up dry cow rations because it works against milk fever prevention and DCAD management. Corn silage and straw are the usual base there.

What the feeding trials show

Three peer-reviewed studies, all in the Journal of Dairy Science, tested this directly by varying the ratio of alfalfa to corn silage.

Dhiman and Satter (1997) ran a full-lactation study at a 50:50 forage-to-grain ratio. The forage portion was either all alfalfa silage, two thirds alfalfa with one third corn silage, or one third alfalfa with two thirds corn silage. Over 305 days, multiparous cows produced 9,593 kg, 10,170 kg and 10,024 kg respectively. Both mixed diets beat all-alfalfa. Nitrogen excretion to the environment fell 6-15% on the corn silage diets, and rumen ammonia was lower. Their conclusion: corn silage should make up one third to two thirds of dietary forage dry matter when fed with alfalfa silage.

Groff and Wu (2005) tested alfalfa-to-corn-silage ratios of 100:0, 75:25, 50:50 and 25:75 across four trials, at analysed dietary crude protein levels averaging 15.7%, 16.9%, 18.0% and 19.2% of dry matter. Milk yield was similar across protein levels in each trial at 35.2-36.1 kg/day. Pushing protein higher simply pushed nitrogen out the back: total nitrogen excretion rose from 484 to 571 g/day and the conversion of feed nitrogen into milk nitrogen fell from 0.27 to 0.22. Their conclusion: about 17% crude protein was sufficient for cows producing 38 kg/day across a range of alfalfa and corn silage proportions.

Hassanat et al. (2013) replaced alfalfa silage with corn silage at 0%, 50% and 100% of forage in a 60:40 forage-to-concentrate diet. Dry matter intake and milk yield both increased as corn silage went up. Dry matter digestibility rose linearly. Rumen ammonia and manure nitrogen fell. Milk fat content dropped and milk protein rose — the standard response to a higher-starch, lower-effective-fibre diet.

Read together, the message is consistent. Adding corn silage to an alfalfa-based diet raises intake, raises yield and improves nitrogen efficiency. Going all the way to 100% corn silage starts to cost you milk fat and effective fibre. The productive zone is in the middle.

Cost per unit of energy vs cost per unit of protein

Comparing forages on price per tonne is meaningless because they carry different amounts of water and different nutrients. Compare them on cost per unit of what you are actually buying.

First, convert the composition table to a per-tonne and per-maund basis, as fed.

Then use two formulas:

• Cost per MJ of energy = delivered price per tonne ÷ MJ of ME per tonne
• Cost per kg of crude protein = delivered price per tonne ÷ kg of crude protein per tonne

Worked example with invented numbers, purely to show the method. These are not quotes, not our prices, and not market data.

In that illustration, corn silage is the cheaper energy and alfalfa is the cheaper protein — which is the usual outcome, and the reason both appear in the same ration. Substitute your own delivered prices, your own tested dry matter and your own tested protein, and the answer will be specific to your farm.

Two cautions. First, use tested figures, not table averages, for anything you are actually buying. Second, use delivered prices — freight is a large share of forage cost and it does not scale with nutrient content.

Freight arithmetic, and why hay dominates long-distance forage trade

This is the honest reason the Gulf imports alfalfa hay rather than silage.

A tonne of alfalfa hay is 894 kg of dry matter. A tonne of corn silage at 32.5% dry matter is 325 kg. Per tonne on a truck or in a container, hay carries 2.7 times the dry matter, about 2.1 times the energy and about 7 times the protein. The rest of what you are shipping in silage is water.

A 40 ft container is typically limited to somewhere around 26-28 tonnes of payload, depending on the shipping line and on road weight limits at both ends. At those limits, a container of alfalfa hay carries roughly 23-25 tonnes of dry matter. A container of corn silage at 32.5% dry matter carries roughly 8.5-9 tonnes. That gap is why baled dry hay, not silage, moves across oceans.

The counter-arguments are real but they are about distance and form, not about biology:

• Freight cost per MJ falls sharply on short sea legs. Silage exported from Pakistan ships from Karachi, typically to Jebel Ali — a few days' sailing. It is not comparable to hay shipped from the US Pacific Northwest, South America or southern Europe.
• Wrapped baled silage arrives fermented and ready to feed. There is no soaking, no chopping line, no ensiling risk taken by the buyer.
• Silage supplies starch. Hay does not. If your ration gap is energy, importing more hay does not fill it.

Any buyer comparing the two should do the sum on delivered cost per MJ and delivered cost per kg of crude protein at their own gate, using their own freight quotes. We would rather you ran that number than took a claim on trust.

The Gulf context

Gulf dairying runs on imported forage. The reasons are simple: negligible rainfall, high evaporative demand, and groundwater that is finite, often saline and increasingly restricted by policy. Regional agricultural policy over the last decade has moved consistently against water-intensive field crops, and forage is among the most water-intensive things you can grow.

Alfalfa is a perennial. Under Gulf irrigation it grows and transpires year-round across multiple cuts, so its annual water use per hectare is high relative to a single maize silage crop of 100-120 days. That combination — very high water demand, very high domestic production cost — is what pushed forage sourcing offshore.

So Gulf herds run high-alfalfa, high-concentrate rations, often with imported rhodes grass or straw for fibre. The structural gap in that ration is fermentable forage energy. It is currently filled with grain and by-products, which are themselves imported and priced against global commodity markets.

That is the opening for regionally produced corn silage. Not as a replacement for alfalfa — the herd still needs alfalfa's protein, calcium and long fibre — but as a starch-bearing forage on a short freight leg.

A buyer importing silage into the Gulf should expect the normal feed-import apparatus to apply: an import permit from the competent authority, a phytosanitary certificate issued by the exporting country's national plant protection organisation, and a commercial and analytical document set with the consignment. Ask any supplier which of those they issue themselves and which they arrange.

your current export position — whether you are shipping to Gulf buyers today or preparing to — and any buyer profile or case example you are willing to publish here

The Pakistani context

Pakistani dairying is buffalo-dominant and green-chop-dominant. The typical smallholder and mid-size ration is seasonal green fodder plus wheat straw (bhoosa) plus whatever concentrate the milk price justifies. Berseem carries the winter, maize and sorghum fodder carry the summer, and there are two well-known lean periods where fodder is short and milk falls.

Lucerne is grown here, but on a far smaller area than berseem, and quality is inconsistent because cutting is usually driven by feed shortage rather than by growth stage.

Corn silage changes two things in that system. It removes the seasonality — a fermented feed made in season and fed year-round. And it puts starch into a ration that is usually fibre-heavy and energy-short.

What it does not do is fix protein. A buffalo herd moved onto a heavy corn silage base still needs a protein source: berseem or lucerne where available, or oilseed cake, or a formulated concentrate. Selling silage as a complete answer would be dishonest and it would cost the farmer milk.

One further point specific to Pakistan. Most milk here is bought on fat. The trial evidence is clear that high-starch, low-effective-fibre rations depress milk fat percentage. If you move a buffalo herd hard onto corn silage without maintaining long fibre in the ration, you can raise litres and lose value. Keep the straw or long hay in.

Practical ration guidance

The figures below are general industry starting points, not a formulation. Every herd needs its own ration built on its own tested feeds by someone competent.

Starting points

High-producing herd on a mixed ration. Forage commonly makes up 50-60% of ration dry matter. Within that forage, the trial evidence supports corn silage at one third to two thirds of forage dry matter, with a legume forage making up the balance. Diet crude protein around 16-17% is sufficient for cows at 35-40 kg/day; Groff and Wu found no yield benefit above that, only higher nitrogen excretion.

Buffalo herd moving from green chop and straw. Introduce silage gradually, replacing part of the green chop and part of the straw. Keep a long-fibre source in the ration. Keep or add a protein source. Watch dung consistency and rumination for the first two weeks.

Dry cows and heifers. Corn silage is easy to over-feed on energy to this group. Dilute it with straw. Restrict alfalfa in close-up dry cows for calcium and DCAD reasons.

Rules of thumb

• Add corn silage, add protein. Every kilogram of silage dry matter you add displaces roughly 0.11 kg of crude protein compared with the alfalfa it replaced.
• Add alfalfa, check fermentable energy. Protein without starch leaves the farm as urine.
• Most lactating rations sit somewhere around 22-28% starch of ration dry matter. Corn silage at high inclusion can take you there on forage alone, before any grain.
• Long-standing minimums for total NDF of roughly 25% of ration dry matter, with about 19 points of that coming from forage, remain a sensible floor. Particle length matters as much as the number.
• Test both feeds. The published range for alfalfa crude protein is 11.3% to 25.3%. The published range for corn silage starch is 16.8% to 40.6%. Formulating on averages within ranges that wide is guesswork.

What to watch after a change

Milk fat percentage, rumination time or cud-chewing counts, dung consistency, and feed refusals. A drop in milk fat with a rise in milk protein is the classic signature of too much starch and not enough effective fibre. It is fixable by adding long fibre before it is fixable by cutting silage.

Where our silage fits

We breed our own hybrid corn genetics, grow the crop on our own farms in Punjab, and harvest at milk-line stage. We chop, bale and wrap ourselves: 60-70 kg bales in multi-layer (6-8 layer) UV-resistant film, which is what allows the feed to be handled, stored and moved as discrete units rather than as a bulk pit.

We sell silage domestically across Pakistan, and the baled and wrapped format is built for the kind of freight leg described above rather than for a bunker on the farm that made it.

We are not going to publish numbers here that we have not measured on the consignment you would receive.

• Dry matter: your measured dry matter % range at delivery
• Crude protein: your measured crude protein % of DM range
• Starch: your measured starch % of DM range
• NDF: your measured NDF % of DM range
• Fermentation pH: your measured pH range
• Laboratory and testing arrangement: which lab you use, what is tested per batch, and whether a report accompanies each consignment
• Bales per 40 ft container: bales per 40 ft HC container and the resulting payload in tonnes
• Minimum order quantity: MOQ for domestic and for export
• Pricing: how you quote — per bale, per tonne, ex-farm or delivered — and current price basis
• Lead time and delivery coverage: domestic delivery areas and lead times, and — if you are quoting export — your current export status and the lead time you can commit to
• Export status: state plainly whether you are shipping export consignments today or are set up and building toward it, and which markets
• Certifications and export documentation: which phytosanitary or other certifications you hold or can arrange, who issues them, and what documentation you can supply with a consignment

If you want to run the cost-per-MJ and cost-per-kg-protein comparison against the alfalfa you are currently buying, send us your delivered alfalfa price and its test report and we will run the arithmetic with you. Message us on WhatsApp at +92 310 4603311 or email [email protected].

Sources

• Feedipedia, Maize silage — INRAE, CIRAD, AFZ and FAO feed database. Composition, energy values, digestibility and ensiling guidance.
• Feedipedia, Alfalfa (Medicago sativa) — INRAE, CIRAD, AFZ and FAO feed database. Alfalfa hay composition, energy values, digestibility and nitrogen degradability.
• Penn State Extension, Corn Silage Production and Management — harvest moisture targets, half milk line stage, digestibility and energy per acre.
• Dhiman, T.R. and Satter, L.D. (1997). Yield response of dairy cows fed different proportions of alfalfa silage and corn silage. Journal of Dairy Science. PMID 9313149.
• Groff, E.B. and Wu, Z. (2005). Milk production and nitrogen excretion of dairy cows fed different amounts of protein and varying proportions of alfalfa and corn silage. Journal of Dairy Science. PMID 16162536.
• Hassanat, F. et al. (2013). Replacing alfalfa silage with corn silage in dairy cow diets: effects on enteric methane production, ruminal fermentation, digestion, N balance, and milk production. Journal of Dairy Science. PMID 23684039.
• Dairy One Forage Laboratory Feed Composition Library — cumulative feed analysis statistics, useful for checking your own results against a large sample population.