First, I walk along the bunk and look at the cows that are eating — and look over to the cows lying in their stalls. I’ll also pick up a handful of lactation diet and pick through it.

In these short five minutes, these observations give me a ballpark idea as to how much lactating diet is being eaten on an as-fed and dry-matter intake basis.

When the dairy producer walks with me, I often fine-tune these observations by asking specific questions about the cows or something about the diet. By getting a handle on the dry matter intake of the lactation barn, I am really getting an idea of the amount of dietary energy intake that drives milk production — which in most cases is almost a perfect correlation.

With the advent of more robot milking systems, the dry matter intakes of lactating dairy cows have dramatically increased, and milk production follows along. For example, I can design a PMR (partial mixed ration) to be fed in the bunk at 50 kg on an as-fed basis (25 kg, dmi) and another five kg of robot pellets fed at the milking stations.

As a result, the dairy cows are cleaning up about 30 kg of actual feed on a dry matter basis to produce 40-45 kg of milk per day. Such intake and performance were really unheard of 10 years ago in the traditional parlour milking systems.

Whether lactating cows are milked in a parlour or robot barn, high-quality forages have always promoted high dry matter intakes. The science is simple: more kilos of a well-balanced lactation diet tend to pass through the cows’ rumen, because its fibre portion tends to be more efficiently digested by the resident rumen microbes, which also speeds up its rate of passage throughout the whole digestive tract. Naturally, there are many chemical restraints in the rumen that kick in along the way, which also help maintain such good rumen function.

Based on these broad-based nutritional principles, here is a set of dairy barn suggestions that in my experience help achieves optimum feed intake among lactating dairy cows.

Set up a close-up dry cow feeding program

Close-up dry cows (three weeks before calving), which consume about 12 kg of dry feed daily, have been shown to have greater DMI as early lactating cows and fewer post-partum metabolic problems.

Promote good rumen fermentation

Typical rations for lactating dairy cows should be formulated to contain 19-21 per cent acid detergent fibre (ADF), 28-32 per cent neutral detergent fibre (NDF) (with 75 per cent coming from effective forage fibre) and limitations of 35-42 per cent placed on non-structural carbohydrates.

Know DMI and as-fed intake

A weekly schedule of DMI and as-fed intake of the lactation herd, as well as the moisture content of the diet, should be recorded. A friend of mine, who milks 350 dairy cows, measures their DMI and as-fed intake every few weeks and their dietary moisture levels about once per week. In doing so, he has significantly decreased the incidence of ketosis in his fresh cow group.

Formulate healthy rumen diets

Feed a portion of the grain that has slower rates of starch digestion, such as grain corn, to prevent acidosis. Avoid feeding too much bypass palm fat. Make sure to limit feed unpalatable feed ingredients. Lastly, check forages and grains for visible mould and other contaminants.

Use a direct-fed microbial (DFM)

I often formulate a DFM into lactation diets. It contains bacteria, grain and forage enzymes and yeasts, which have been shown to improve feed digestibility and prevent sub-acidosis rumen acidosis. Fed at 10 g per head per day, it costs about 25 cents per head per day.

Most of these suggestions take time to implement, but sometimes it only takes five minutes of common sense to promote dry matter intake in lactating dairy cows.

At one farm I visited recently, the bunk ration seemed to be very dry. All it took was adding 100 litres of water to the PMR that helps increase its consumption and subsequent milk production — just a little bite.

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There was more than just talk about growing more peas in Western Canada in which an offshoot would be feeding more field peas and pea byproducts to livestock. Now it seems nearly everything in that market segment is at a standstill, with a few bankruptcies along the way. Yet as a dairy nutritionist, I want to revisit the feeding of peas to lactating dairy cows, which means determining the crop’s local availability as well as nutrition and economic viability.

Geographic variability

Field peas are not grown as much in the eastern Prairies compared to the more western provinces. Although there was a bit of an uptick in its acres a few years ago, Manitoba grew only about 160,000 acres of field peas in 2023, compared to about 1.5 million acres of soybeans. Saskatchewan and Alberta sowed in the opposite way: 1.6 million and 1.3 million acres of peas, compared to only 68,000 and 6,500 soy acres, respectively.

Such geographic disparity does not dissuade me from investigating the nutritional value of field peas for dairy cows. Like corn or barley, peas can be fed to high-milk producing dairy cattle as a good dietary energy source. It derives its megacalories (Mcal) from highly available and readily digestible starch, which drives consistent milk production. For example, a routine laboratory analysis reveals peas contain 52 per cent starch compared to 72 per cent starch found in corn, and 60 per cent starch cited in barley grain. Non-fibre carbohydrate (NFC) levels are about 64 per cent versus 65 per cent in barley and 75 per cent in grain corn. As a result of these starch and NFC values, the NEL (net energy of lactation) of peas yields a good 2.02 Mcal/kg.

Peas are also a good source of dietary protein for dairy cows. Unlike the above-mentioned grains, field peas have a higher content of about 22-24 per cent crude protein. This is about half the value of soybean meal (47 per cent) and canola meal (36 per cent) and slightly lower than corn distillers’ grains (28 per cent). Pea protein is highly degraded in the rumen like soybean meal and often has to be balanced with highly bypass (that is, undegradable) protein ingredients, such as DDGS, if it is formulated in dairy lactation diets.

Substitution

In the table shown here, I formulated a typical corn silage-based diet for lactating dairy cows milking about 40 kg milk, 4.3 per cent milkfat at 150 days-in-milk. Barley was used as the primary energy concentrate source, while a combination of soybean meal, canola meal and DDGS achieved total/bypass protein requirements of these lactating dairy cows.

One kilo of peas easily replaced a half kilo of barley and half kilo of soybean meal, with no significant adjustment made to the other feed ingredients such as DDGS (bypass protein).

As a result, I would expect the same milk or milkfat yields, similar to animal science research testing peas as a replacement for corn/soybean meal in dairy diets.

Similarly, I found out by adding one kg of peas for 0.5 kg of barley and 0.5 kg of soybean meal didn’t significantly change the average cost of feeding a typical lactating dairy cow. My control diet cost $9.80 per cow compared to $9.84 per cow fed peas. Note: I priced in barley at about $5.50 per bushel, soybean meal at $590 per tonne and peas at $10.50 per bushel. I encourage any dairy producer to use their own on-farm prices to determine such diets possibly used at their dairy farm.

A friend milks 165 dairy lactating cows and harvests about 1,500 acres of field peas each year. A few years ago, he followed an exercise similar to mine, adding about two kg of ground peas, and substituted out soybean meal and hammered corn and barley.

As a result, he found it took these milking cows a few days to get used to the peas in their TMR, as well as one or two of them bloated on it. Like university trials, he didn’t see any milk or milkfat response. Nor did he save any money on feed costs, despite peas worth about $6 per bushel at the time.

Nothing was gained or lost — nutritionally or economically — but my friend demonstrated field peas are a good substitution for other common feedstuffs for lactating dairy cows. We can only hope one day the pea industry returns, which would likely earn his further support and the attention of more dairy producers across the entire Canadian Prairies.

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When I ask dairy producers why they feed them over conventional ones, they often say they don’t know or their nutritionist thinks it’s a good idea.

There is nothing technically wrong with feeding chelated trace minerals to lactating dairy cows, but I also believe feeding them in such a broad way is costly and is likely not necessary. That’s why I take a practical approach and recommend feeding chelated trace minerals to lactating dairy cows in specific situations.

Chelation is a type of biological bonding of specific molecules to metal ions. The former is usually an organic molecule such as an amino acid bound to the latter, but not necessarily. This results in a chelation effect, which yields greater bioavailability, superior absorption, retention and general metabolizable properties to the resident metal in dairy nutrition, as compared to inorganic “rock” trace minerals.

Chelated examples include positive-charged trace mineral bound to an amino acid: zinc methionine, copper lysine and manganese methionine. It should be noted, a negative-charged trace mineral such as selenium cannot be truly chelated. Rather, organic selenium is produced by feeding inorganic selenium to yeast, which incorporates it into their body proteins.

Before I decide to formulate chelated trace minerals into a lactation dairy diet, I often take a step back and ask: what trace minerals are going to be required in the first place, and at what dietary levels?

For example, the National Research Council (NRC) recommends the copper requirement to support these functions in dairy cattle is 10 mg/kg of diet (on a dry matter basis) which, given a dry matter intake of 25 kg (dry matter basis), means we need to supply about 250 mg per head per day.

Research also dictates feeding higher amounts of copper (as well as essential zinc, manganese and selenium) does not produce a beneficial response, as widely believed. In fact, the opposite may be true: isolated dairy cases of copper toxicity have been reported at dietary levels as little as 400 mg per head per day.

Consequently, I implement inorganic “rock” trace minerals in my own lactation feeding programs for dairy producers, largely based on NRC recommendations. That’s because inorganic copper sulphate, zinc oxide, manganese sulphate and sodium selenite have a suitably high degree of digestive, absorption and retention rates.

Where these trace mineral rock sources tend to fail is when certain environmental situations arise, which significantly reduce their dairy bioavailability properties, to the point where animals cannot meet respective nutrient requirements. In situations such as these, I then switch to comparable chelated trace minerals:

Antagonistic minerals in forages

It’s well documented that high molybdenum in forages binds inorganic copper sources when both are ingested by the average dairy cow. Molybdenum is classic when it combines with this copper sulphate in the rumen and the rest of the digestive tract to form insoluble complexes, which are easily excreted. Since chelated copper lysine cannot be bound by molybdenum, its natural metabolism to meet the lactating cows’ copper requirement remains uninterrupted.

Build trace mineral status

Trace mineral status is very important in the workings of immune function and reproduction, especially ovulation.

Deficient levels of copper, manganese, zinc and selenium are known to cause anestrus in fertile cattle. Ohio State University animal scientists reported that cystic ovaries were diagnosed in 19 per cent of a split group of dairy cows injected with organic selenium compared to a 47 per cent incidence of cystic ovaries in untreated cows.

Strengthening hooves

Zinc methionine strengthens cattle hooves. About 10 years ago, I balanced the dry cow and lactation diets for a 100-cow dairy herd. The dairy herd had a high incidence of foot rot, and white-line sole separation. I suggested we feed zinc-methionine (a specific chelated zinc) at four grams per head, daily. After six months, most of these hoof issues were almost non-existent. The hoof-trimmer even commented that the cowherd’s hoof-horn became much harder during trimmings. No other significant changes were implemented in their diet during this time.

These are three personal testimonials that demonstrate the strategic use of chelated trace minerals in lactation dairy diets. Whether dairy producers do use them in such defined ways or in mainstream dairy nutrition is really a matter of choice. In both ways, they should satisfy respective lactating dairy cow trace mineral requirements.

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This practice maintains a 13-month calving interval. Unfortunately, the onslaught of cystic ovaries in 30 per cent of all breeding cows makes it a challenge. Yet, there is hope that good nutrition, prior to and right-after they calve, can eliminate a significant number of cystic ovaries from occurring in the first place.

Energy status in lactating dairy cows is the first limiting nutrient that most affects the incidence of cystic ovaries.

The actual energy requirement for successful follicular ovulation is very low, at three megajoules (MJ); it also takes on an extremely low priority, compared to 60 MJ for vital body needs and up to 250 MJ for milk production during early lactation days.

Early-lactation dairy cows do not consume enough dietary energy to meet such high levels of milk production and thus are in a “negative energy balance” (NEB) for about six weeks after calving, which adds to the energy challenge.

As a result, one can speculate that being in a NEB makes cows even more susceptible to higher incidence of ovarian cysts.

Reproductive research dictates NEB in dairy cows can adversely affect normal development of follicles by disrupting the production of essential tissue-specific and systematic hormones.

For example, it has been proven that when a cow has poor energy intake there is a significant decrease in the levels of follicular and corpus luteum hormones that complete her normal estrus cycles after calving. Other similar studies demonstrate that the release of large amounts of fatty acids from the breakdown of body fat during NEB is also poisonous to fertile egg cells, even if they are released during the ovulation process.

What to do?

Over the years, there have been several hormone protocols using GnRH, progesterone and prostaglandins to treat cystic ovaries in chronic cows. Subsequent research suggests they are highly effective to induce ovulation, but often retain lower conception rates.

Although I know of several dairy producers who have complete reliance upon periodic hormone treatments, I suggest they shouldn’t give up on a good nutrition program that could help reduce ovarian cysts in their early-lactation cows. My dietary suggestions:

Pre- and post-partum feed

Implement proper transition/early lactation diets (three weeks before and three weeks post-partum). This should be done to promote good dry matter intake, optimum body condition (see below) and reduce NEB during early lactation. Close-up dry cow diets should dovetail into early 60- to 90-day lactation rations.

Both diets should provide adequate dietary energy, as well as provide enough forage fibre to maintain excellent rumen health. Another of the goals is to build up feed intake to about 3.5 to four per cent of cows’ body weight by nine to 10 weeks post-partum.

BCS at its best

Maintain a body condition score (BCS) of 3 to 3.5. Existing research demonstrates that over-conditioned cows (on a BCS scale where 1 = emaciated and 5 = obese) are 2.5 times more likely to develop ovarian cysts during the first 60 days, post-partum, compared to lactating cows with an optimum BCS of 3 to 3.5.

A direct link to cystic ovaries has yet to be proven, but thin lactating dairy cows of less than 2.5 BCS have been shown to have a high incidence of silent heats and lower conception rates.

Serve up supplements

Feed adequate levels of trace minerals and vitamins. Deficient levels of copper, manganese, zinc and selenium and inadequate vitamins A, D and E are known to cause anestrus in female cattle.

For example, Ohio State University animal scientists reported cystic ovaries were diagnosed in 19 per cent of a split-group of dairy cows injected with selenium, compared to a 47 per cent incidence of cystic ovaries in an untreated control group.

Avoid mouldy feeds

Zearalenone, a mycotoxin produced in mouldy corn, has estrogen-like properties and has caused many reproductive problems including a higher incidence of ovarian cysts in dairy cattle. The poisonous threshold of zearalenone is 200 p.p.b. in lactation dairy diets.

These are only a few good suggestions I believe can reduce the incidence of cystic ovaries in many dairy herds. Regimens such as good early-lactation nutrition — which can affect the matrix of 30 to 40 reproductive hormones for successful release of an ovum — should be seriously examined and implemented.

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My takeaway thought was that not enough effective forage fibre was being fed in all three. However, that was quickly contradicted by a few weeks of high milkfat records in good milk volume shipments in each case. Despite my initial bewilderment, in hindsight I still maintain there was a lack of effective forage fibre in these lactation diets. That type of feed will not sustain good long-term performance on these or any other dairy farm.

One of the pillars of dairy lactation science is that effective forage fibre is not a true nutrient like energy and protein, but there is a strict requirement for it in the lactating dairy cow’s diet. It stimulates nerves in their inner rumen wall into regurgitating the dairy diet back into the cow’s mouth.

In turn, she chews large forage particles into smaller pieces and swallows them again. Cud chewing not only aids the dietary fermentation process by the ruminal microbes, but repeats itself until large forage particles are either digested in the rumen or become small enough (10-11 mm) to leave the rumen and enter the omasum and later the abomasum.

For example, about 50 to 60 per cent of milkfat structure is built from such ruminal volatile fatty acids and other metabolites. They are generated by rumen-microbial fermentation of effective forage fibre. The other 50 per cent milkfat portion is drawn off from fatty acids absorbed directly from the bloodstream. It is here where added palm fat bypasses the rumen and become a direct support of milkfat levels.

Three rules for fibre

I use three mainstream “effective fibre” rules to assure cows remain healthy by properly chewing their cud:

1. The diet contains 28 per cent NDF.
2. 75 per cent of this NDF comes from forage or equivalent sources (21-22 per cent eNDF)
3. Forages are chopped to provide 15-20 per cent of the dietary particles being more than 1.5 inches long, creating a good floating mat in the rumen.

As I ponder the significance of these three effective fibre rules in all lactating dairy diets, I cannot help wonder how the above dairies seemingly circumvent them. Another group of three producers that feed similar lactation diets may offer plausible explanations:

• Producer No. 1 keeps non-fibre-carbohydrate levels well below 38 per cent of the total lactation diet (dm basis). A couple of years ago, he fed highly digestible corn silage with 33 per cent starch levels. At least 1.5 kg of grain corn per cow was removed in the associated grain mix.
• Producer No. 2 feeds highly digestible corn silage and about eight pounds of alfalfa hay per head, decreased from 12 pounds in a previous diet. He also quit adding three to four pounds of brome grass hay because extra hay led to uncontrollable sorting, which was followed by sub-clinical acidosis (SARA) in the lactating herd.
• Producer No. 3 told me that he watches the daily manure from all his milk cows. If it’s getting a little loose (a sign of SARA), he increases the alfalfa-grass portions by about one kilogram and removes about three kilograms of high-quality corn silage.

As a footnote, all these producers, and the former dairies, feed palm fat at 500 grams per head per day. It seems on each farm that adding this amount of palm fat leads to a 0.2-0.4 per cent increase response in milkfat, regardless of in-diet effective forage fibre levels.

Not to diminish the value of palm fat in lactating dairy diets, but whenever I visit these latter three producers, most of their resting lactating cows are rhythmically belching and chewing without a care in the world. Therefore, I’m confident that dietary fibre levels in each of these dairy diets are adequate for good long-term milk/milkfat production. It also makes me think a more concrete investigation is needed into the lack of cud-chewing cows in the first group of dairies.

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Effective forage fibre, not palm fat, is the foundation of all good milk fat levels in milk and must be included in all well-balanced lactation diets. Unlike energy and protein, effective forage fibre is not a true nutrient, but there is a requirement for it in milking cows. Its biggest job, which is clearly associated with milk fat yield, is to maintain a healthy population of rumen microbes, which in turn drives optimum fermentation of the dairy diet and essential nutrient metabolism.

Using the checklist

Recently, I visited a 150-lactating free-stall operation (production figures: milk, 37 kg, milk fat, 3.9 per cent, DIM = 173) and it had some underlying issues with inconsistent milk fat production. And this was despite most of the cows chewing their cud in the lactation barn and 400 g per head of palm fat was fed in their TMR. It really gave me an opportunity to use the major points of an “effective-fibre” checklist that I carry around in my head, so I might spot a few troublesome factors, as follows:

• Look at the cows. It is my understanding from the producer that all the early-lactation cows come into lactation in a BCS of 3.0-3.5, yet many of the cows had a hard time retaining body condition by the end of lactation. A quick look at the close-up cows (21 days before calving), showed me that they would have a hard time achieving good dry matter intake, well into 100-days post-calving.
• Scoop up a handful of TMR. It was freshly laid down in the bunk, which looked like it had enough effective forage fibre, but using a Penn State Shaker box, which separates TMR particle size, showed me differently. It showed a lot of forage fibre in the top screen (20-22 per cent), 55 per cent in the bottom tray and the remainder (20-25 per cent) in the middle. A lab analysis also revealed that the entire lactation diet provided the standard 28 per cent NDF (neutral detergent fibre) with an adequate 75 per cent of this fibre coming from forage sources. Yet the NFC (non-fibre-carbohydrates) of the ration exceeded a threshold of 40 per cent and starch stood at 24.7 per cent. Moisture of the entire dairy diet stood at 52.3 per cent. (You can learn more about the shaker box in this video.)
• Investigate bunk management. Each day, the producer makes up only one batch of lactation ration and lays half down in the morning before milking and the other half before the afternoon milking. The feed is pushed up every 2 ½ hours by a robot. Current DMI intake ranged from 50-54 lbs.

After putting all the evidence together, I suspected that this lactation dairy herd suffered from an underlying mild-acidosis condition, despite most of the cows chewing their cud during my initial observations. It was the shaker box that convinced me that a lot of long-stem indigestible fibre from rather coarse first-cut alfalfa haylage (high in indigestible lignin-fibre) and the high level of NFC of the lactation diet both limited optimum rumen function — one of the leading causes of erratic milk fat yield.

Recommendations

So I made the following dietary friendly milk fat recommendations:

1. Increase the proportion of corn silage (a rich source of hemicellulose; leads to consistent rumen function) and lower the amount of first-cut alfalfa haylage in a final 2/3 to 1/3 ratio.
2. Limit the amount of barley from 8.5 to 7.0 kg, which reduces excessive NFC.
3. Switch out 300 grams of palm fat with a 50/50 tallow-palm bypass fat to help recover lost body condition in later lactation cows.
4. Review the close-up diet and take corrective action to promote dry matter intake before and after calving.

It took about three weeks to see results, which included a slight drop in milk fat, but it largely recovered as soon as the cows adjusted to these major dietary changes. As a footnote — we initially thought of just increasing the bypass palm fat to 500 grams to correct original bouts of milk fat depression, but quickly realized that improving effective forage fibre in the diet was the best way to go.

— Peter Vitti is an independent livestock nutritionist and consultant based in Winnipeg. To reach him call 204-254-7497 or by email.

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As a result many metabolic and physical problems are also avoided, as she gives birth to a healthier calf and it helps her prepare for her next lactation. That is why I still advocate these basic principles in my consulting work.

I believe a good 40-day faraway feeding (and management) program should have three underlying objectives:

The program

1. Allow the udder to rest. During a 10-month lactation cycle there is a 50 per cent decline in the number of secretory cells within the mammary gland. During the faraway dry period, the number of secretory cells is restored to its full complement needed in the next lactation. However, the extent of milk-cell rejuvenation is complete by 25 days into the dry period (University of Maryland).

2. Restore organ health. The high-forage diet allows the cow’s rumen to rebound, regrowth of the essential papillae tissue, restoration of healthy pH levels and resets muscle tone. All of these are compromised by feeding high-energy (starch) lactation diets. The 40-day faraway program also allows the cow’s liver some time to recover from metabolic problems such as ketosis and fatty liver syndrome.

3. Restore hormonal and immune function. Lactating cows milking at high production levels have a lot of hormonal changes going on that affects natural dry matter intake of feed, feed digestion/metabolism, bodyfat and bone mobilization as well as fertility. The 40-day program also helps restore the cows’ immune function, which is very active during lactation to combat mastitis and other infections.

Proper body condition

With these objectives, I also keep them in mind the cow’s immediate nutritional status after months of lactation. A dairy cow should be brought into dry period with a body condition score (BCS) at 3.0-3.5 (1 = thin, and 5 = fat). And it should be fed for the next 40 days (dovetails into the close-up feeding program) with a ration that either maintains optimum BCS or builds up thin=BCS cows until calving.

To maintain/build such optimum BCS in faraway dry cows as well as support their growing fetus (when 65-75 per cent of fetal growth occurs), a faraway dry cow diet should be made up of bulky good-quality grass-type forage by which the cow consumes 1.8-2.2 per cent of her bodyweight (DM basis).

On an absolute basis, this means the whole diet should supply about 14-16 Mcal of dietary energy (or TDN = 60-62 per cent), and 13-14 per cent crude protein. A dry cow premix ought to be provided to round-out these forages; 0.50 per cent calcium, 0.30 per cent phosphorus, 0.5 per cent salt and trace minerals (copper, zinc, selenium) and vitamins (A = 100,000, D = 3,000 and E = 1,000 iu/head). Lastly, 10 g per head per day of commercial yeast would be included.

Some dairy specialists advocate that cows really don’t need this seven-week period to prepare for lactation. They point out that many high milk-producing cows could produce more milk of significant economic benefit by allowing an extra 25 lactation days (325-day lactation cycle, instead of the standard 305 days), which is then offset by a new modified 30-35-day dry-cow program. But the results of university research performed on proposed short faraway dry cow periods have been mixed. Mature cows are largely unaffected while first-calf heifers have consistently reduced milk yields.

About 10 years ago a friend who milks 300 Holstein cows tried to reduce his faraway dry cow program by 10 days. After about a couple of months, he returned to his previous program. He discovered that many of his dairy cows often come into the dry period in a relatively thin body condition. On the new (shorter) program, they did not recover this bodyweight, as well as they did on the longer faraway program. He also speculated that his older program pushed the dry cows’ “reset button,” leading to better long-term cow herd longevity.

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Dairy nutritionists like myself and dairy producers now have access to modern BHB (Beta-hydroxybutyrate) milk tests through regular Canwest DHI testing or from on-farm keto-testing kits. By detecting ketosis in problematic cows and implementing strong transition cow-feeding and management programs, we should be able to reduce early lactation ketosis, which is detrimental to long-term dairy cow health and performance.

Don’t ignore it

Ignoring a ketosis cow doesn’t solve the problem, either. Untreated clinical ketosis include a rapid drop in body condition, loss of appetite, decreased milk production, and yes, acetone-smelling breath. Most veterinarians will tell us that such clinical ketosis is relatively rare in dairy cows with the majority of ketosis symptoms in afflicted cows being hidden or subclinical in nature.

Rather, these latter cows will suffer from a higher incidence of displaced abomasums, retained placentas, mastitis, or weaken immune system. Subclinical ketosis has also been linked to milk fever and reproductive problems. Cows with subclinical ketosis lose about 25 per cent of their potential milk production per lactation.

Early lactation cows are the most vulnerable to either type of ketosis because, by nature, they cannot meet all their energy requirements of maintenance and high milk production from just their diet. Therefore they are drawn into a state of “negative energy balance” (NEB) for about five to six weeks after calving.

Even well-transitioned cows experience a period of NEB, but they tend to have good post-partum dry matter intakes, which draws a lot of energy from their diets and as a result mobilize a health amount of body fat. This fat energy helps bridge this NEB gap during their early period of peak milk production. By comparison, ketosis-affected cows often have limited feed intakes or energy-unbalanced diets, which leads to high life-threatening rates of fat-breakdown.

Serum (blood) concentrations of NEFAs and ketone bodies such as Beta-hydroxybutyrate (BHB), can determine a potential ketosis threat (and associated severity of NEB) in a chosen group of early lactation cows.

It’s this BHB concept that also underlies the milk keto-screen available by DHI testing as an indicator of ketosis in dairy cows. Since, the first few weeks is considered the highest ketosis risk period in early lactation cows, DHI tests the milk samples of cows between five to 21 days in milk (DIM) and DIM 22 to 42 days. They mark and report “positives” of these samples, which exceed a BHB threshold of 0.15 mmol/l. Their report also shows the percentage of cows that have elevated BHB levels for that reported month as well as those from past three-month increments.

Indicator test

As a general indicator of subclinical ketosis, DHI suggests if 20 per cent or more cows’ milk samples in a particular herd test “positive,” it is designated a high ketosis status and might indicate a possible ketosis problem in any individual herd. On a similar note, Ontario DHI records (43,321 milk samples from June to September, 2014) have illustrated herd level prevalence of subclinical ketosis of 30.5 per cent in cows five to 21 DIM and of 14.7 per cent of cows DIM 22 to 42. Similar Quebec DHI results were reported.

Although identification of subclinical ketosis in lactating dairy cows is helpful and warrants corrective actions, preventing ketosis in any given herd is strongly recommended. One should implement a proper transition diet (three weeks before calving and three weeks post-partum) in order to promote optimum dry matter intake and body condition scores in susceptible dairy cows.

Initially, a good close-up dry cow diet should be palatable which ensures that pre-partum cows are consuming about 12 kg of dry feed daily. The diet should contain moderate energy forages with some room for lead-feeding grain. Close-up dry cows (even fat cows) should not be allowed to lose bodyweight in this period.

Once cows calve, early lactation rations should promote good rumen function (re: effective forage fiber) and yet carry enough available dietary energy to support increasing milk production. The goal is to build up dry matter intake in early lactation cows to about 3.5 to 4.0 per cent of their bodyweight at about nine to 10 weeks after calving.

Tying it together is good bunk management with all good feeding programs set up for both the close-up and early lactation dairy cows. This means that each transition cow should have enough bunk space and adequate time to eat. Matching the energy demands with a dairy cow’s energy needs in the close-up and early stages of lactation is critical in minimizing rapid body fat mobilization and ketosis. Alongside, we should have a ketosis monitoring program (such as DHI) that identifies subclinical cases as well as our progress in reducing ketosis.

Your program might even include my glue-breath test!

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Adding safe amounts of edible fat to total mixed rations (TMRs) of early-lactation cows has been common advice given by dairy nutritionists and veterinarians for years. It is effective in eliciting positive milk and milk fat persistency and often slows down rapid weight loss in dairy cattle during the first 100 days of milk production.

That’s because dietary fats contain more than 2-1/4 times the calories of those found in carbohydrates (barley or corn starch). Common fat sources include oilseeds such as full fat soybeans and whole sunflower seeds (20 to 40 per cent fat) and 100 per cent fat sources, namely pork tallow and canola oil. A third group of dietary fats are commercial manufactured “bypass” fats.

The overall rule for adding these fat supplements to an early-lactation dairy ration is take in account all the natural sources of fat already present and add in these latter fats; making sure not to exceed five to six per cent total fat of the entire dairy diet. One can follow this rule by breaking the dairy diet down into three sections:

• 50 lbs. of forages mixed with defatted proteins (soybean or canola meal) and grains contains three per cent natural fat — 1.5 lb.
• Supplement vegetable oil or tallow (100 per cent) — 0.75 lb.
• Supplement inert rumen-protected fat (99 per cent) — 0.75 lb.

Total = 3.0 lb. or 6.0 per cent total fat

The chemical structures of unadulterated fats found in forages, grains, and pork tallow and canola oil are very similar. Long chains of fatty acids are linked to a triglyceride molecule or exist as free fatty acid chains. The fatty acid chains are of two types, either saturated or unsaturated.

Saturated fatty acids are “saturated” with hydrogen atoms, while unsaturated chains have one or two hydrogen atom pairs missing. Saturated fatty acid chains pass through the cow’s rumen largely untouched, and are digested in the lower gut. Pork tallow contains about 50 per cent saturated and 50 per cent unsaturated fatty acids while canola oil is almost completely made up of unsaturated fatty acids.

There is a limit

Generally unsaturated fatty acids such as found in canola oil are relatively toxic to rumen microbes, particularly forage-fibre digesting species, but that doesn’t mean that canola oil and other unsaturated vegetable oils should not be fed to dairy cows. Fortunately, most rumen microbes have the ability to detoxify and reduce the toxic effects of unsaturated fats through a process known as “bio-hydrogenation” (re: hydrogen is added to the unsaturated fats and turns them into rumen-protected saturated fats). However, excessive amounts of unsaturated fats and oil added to a dairy diet (re: over one pound or 450 g/head/d) often overwhelm this process and as a result interfere with rumen fermentation.

To compliment added saturated and unsaturated from natural feedstuffs in early lactation diets, commercial “rumen bypass” fats are designed to be chemically inert in the rumen, to be digested and absorbed as energy source in the cow’s lower gut. One group of bypass fats achieves protection by locking the fatty acids chains to a calcium molecule to form a ruminal insoluble calcium salt. This bond is broken during digestion in the small intestine. Another group of bypass fats hydrolyzes normally unsaturated fatty acids (such as palm oils) into rumen inert saturated fatty acids.

Regardless, the kind of fat supplement finally chosen and added to the dairy diet, it is important to avoid overfeeding fat in one capacity or another to lactation dairy cows. It is also important that these dairy diets still be balanced with available carbohydrates such as sugar, starch and effective forage fibre (20 to 22 per cent eNDF) in the diet as well as protein, minerals and vitamins in order to support health and normal activities of the resident microbes in the rumen.

Problems to avoid

Here are problems that might be experienced when feeding excessive fat to lactating cows:

• Inconsistent and/or low dry matter intake — Some research indicates overfeeding fat to dairy cows may quickly satisfy their natural appetite for feed (much like us eating a greasy hamburger and fries). Some speculation may also involve reduction in the rate of feed digestion and passage (bypass fats) in the lower gut. Other explanations might involve digestive upsets in the rumen (unsaturated fat toxicity).
• Milk fat depression (MFD) — As mentioned, unsaturated fats are toxic to many fibre-digesting rumen bacteria; cause reduction in acetate/butyrate production that contributes to milk fat production. It is also believed too much tallow or vegetable oil can coat forage fibre particles in the rumen and allow incomplete fermentation. On a different note: University of Illinois demonstrated that two to four per cent tallow caused acidotic conditions in the rumen of dairy cows fed corn silage and MFD, but both conditions were alleviated when corn silage was replaced with an alfalfa-based diet.
• vHigh milk urea nitrogen (MUN) — It is conceivable that supplying too much bypass fat to the lower gut, while literarily starving the rumen microbes of available starch energy could cause incomplete protein digestion and large amounts of urea to be released in the rumen. High MUN levels are linked to lower conception rates in dairy cattle.

Such quantifiable adversity might not occur if dairy diets are well balanced with just the right amount of fats coming from different edible sources. Adding any fats should also complement the rest of the dairy diet, particularly for early lactation cows, which helps them get a good start with milk and milk fat production. Such success should contribute to the profitability of the dairy barn.

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Some of these specialists took note of the more extensive university and extension dairy trials, which report that maximum feed intake is still very important, but it means a lot more than just dumping a total mixed ration (TMR) containing essential nutrients in front of milk cows.

Many dairy producers are striving to feed nutritious diets that high-producing cows like to eat, optimize consistent everyday feed intake, produce exceptional rumen health and also require a shovel-full of common sense right at the cows’ feed bunk.

Know the basics

One of the first things that producer might do before making any substantial changes to existing lactation diets to optimize DMI/increase milk production, is to be particularly aware of the natural laws of general feed consumption by dairy cows.

This means that early high-milk-producing cows should be on target to consume 3.5 to 4.0 per cent of their bodyweight in dry matter feed by nine to 10 weeks after calving. This target sets the tone for the rest of the lactation cycle — for every extra kilo of DMI that a cow eats at peak milk production (i.e. accounting for the natural lag between maximum milk yield and maximum dry matter intake) yields an extra 2.0 to 2.5 kilos of milk per day until she is dried-off at 10 months post-partum. And most large (600 to 700 kg) mature cows will consume about 22 to 27 kg of dry matter feed at peak feed intake. Smaller and growing first-calf heifers should eat about 20 to 25 kilos (DMI, basis).

Regardless of these prime DMI targets, dairy cows will only eat so much “as fed” feed, because moisture content adds simple bulk to the dairy diet. Large and early lactation mature cows consume about 43 to 47 kilos of the feed that is put in front them, while younger and smaller cows often eat no more than 40 to 44 kilos of the same diet.

By keeping DMI and “as fed” values in perspective, farmers should be able to estimate how much total ration to feed to the herd daily. They should also be monitoring how many old and young early-lactating cows are entering the herd as well as counting the remainder of the herd milking in mid- and late lactation.

Similarly, consistent everyday DMI/as fed feed intake should be viewed as another important signal to the dairy producer that the rumen of each high-producing cow is working efficiently. Rumen microbes digest forage fibre and grain starch, turning them into available energy for body maintenance functions, reproduction and high milk performance. They also break down dietary protein into simple compounds, incorporate them into their own bodies, and inadvertently supply the cow with most of the cows’ protein needs. Unbalanced dairy diets, poor feed quality and rapid feed changes upset such sensitive feed fermenters and can quickly derail optimum feed intake.

Maintaining proper rumen function

Dairy producers can manage good rumen function in their cows and therefore achieve optimum and consistent feed intake among their cows by applying the following dairy barn suggestions:

• Feed high-quality feed. Forage quality is the foundation of all good feeding programs. High-quality forage supports higher and more consistent DMI due to their lower unusable fibre content and greater in-depth digestion by the microbes that provides essential nutrients for milk production. Avoid feeding mouldy or spoiled forage and grains.
• Provide adequate “effective forage fibre.” The dairy diet should contain 28 to 32 per cent NDF with 75 per cent of this NDF coming from the forages. Effective forage fibre promotes natural “cud chewing” in the herd to buffer the pH of the rumen and helps prevent detrimental acidosis. If you have difficulty finding cud chewing cows; not enough effective fibre is being fed.
• Formulate a palatable and “rumen-friendly diet.” This point goes beyond merely feeding enough “effective forage fibre.” For example: feed a portion of the grain that has slower rates of starch digestion (re: corn versus barley) as well as avoid feeding excessive amounts of unsaturated fats and/or bypass fats. Make sure to limit feed unpalatable feed ingredients such as blood meal (bypass protein source).
• Know DMI and “as-fed” intake. A spot check or even weekly schedule of DMI and as-fed intake of the lactation herd, the moisture content of the diet, and milk fat bulk tests should be recorded. These are indicators of healthy rumens and underlie optimum dry matter intake/milk production. Actual emerging patterns from this data should be periodically reviewed.
• Impose “common sense” bunk management. TMR should be delivered at the same time of the day and should be pushed up at least three to four times during the day. Dairy producers should never allow bunks to go empty or force cows to wait to be fed, or until all feed (including feed refusal) to be eaten before more fresh feed is provided.
• Check your mixer wagon. Make sure your feed mixer is working properly to deliver a consistent TMR mix at every feeding. Although mixing times can vary for a number of reason, most producers target three to five minutes to make a homogenous feed mix.
• Do a daily barn walk. It is important that average body condition of most lactation cows ranges from 3.0 to 3.5 out of five. Beware of possible acidotic cows in your herd (watch out for gaunt cows, cows not chewing their cud, cows not going to the feed bunk, nutritional lameness). Check out the manure. It should be generally of porridge-like “consistency” (indicator of consistent feed intake and digestibility).

These recommendations are practical points in an all-inclusive action plan for optimal DMI and ‘as fed’ intake of a well-balanced and mixed dairy diet consumed by good milk cows. Ideally, if they eat dairy diets with vigour every day, they should consume essential nutrients, remain healthy and fill the bulk tank.

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