Recovering from Heat Stress

Rick Grant, William H. Miner Agricultural Research Institute

As summer fades into fall and ambient temperatures drop, the negative consequences of heat stress on the dairy herd often linger. Lameness, poor reproduction, low milk production efficiency, and elevated incidence of health issues may continue on a dairy even after summer’s heat is past. Understanding what nutritional and management factors influence the severity of heat stress carryover effects, and how to mitigate these factors is crucial for the herd to move successfully into the fall feeding cycle.

An over-riding point is that high-producing cows experience heat stress whenever THI reaches 68, so be sure to keep cooling cows into late summer and fall – don’t stop heat stress abatement too soon! Even mild heat stress can be damaging to cow health in both the long- and short-term. Continue reading

Boosting Milk Components and De Novo Fatty Acids

Rick Grant, William H. Miner Agricultural Research Institute, Chazy, NY

Producing more milk fat and protein is a sure-fire way to enhance herd profitability. And, the best way to boost milk fat and protein is to enhance rumen fermentation with a particular focus on fiber digestion. Over the past 18 months or so, a group of scientists led by Dr. Dave Barbano at Cornell University, scientists from Miner Institute, in collaboration with the St. Albans Coop have been studying the link between on-farm management, nutrition, and milk composition with a focus on bulk tank milk sampling. Continue reading

Measuring Fiber Digestiblity

Rick Grant, William H. Miner Agricultural Research Institute

To make milk from forage, we must understand the role of 1) fiber digestibility and indigestibility, and 2) fiber particle size and fragility. These forage-fiber characteristics are highly related to eating, ruminating, rate of particle breakdown and passage from the rumen, dry matter intake, and ruminal digestive efficiency. Over the past year or two, the focus has been squarely on how to best measure fiber digestibility. As we look forward to the 2016 forage season, where does this conversation sit? Continue reading

Milk Component Price Variation – Should I Change Ration Formulation?

Amaferm and Milk Fat

Milk fat prices recently have been significantly higher than the historical average.  It is important to understand this critical milk component and the income opportunity it represents.  Rumen fermentation and health are quite important in the regulation of milk fat yield as noted by Dr. Juan Marquez in his article below.  Maximizing fiber digestion results in more acetate and butyrate, which are the major precursors of de-novo milk fat.  Amaferm is the most researched and validated product in the marketplace to increase and maximize the digestion of forage fiber.

Milk Component Price Variation – Should I Change Ration Formulation?

Juan Castro Marquez, PhD

Federal Milk Marketing Order (FMMO) milk fat prices have steadily risen over the course of the past year, 2015, and were $3.18/lb. and $2.91/lb. in November and December, respectively.  The 7-year average for the FMMO milk fat price (years 2009 to 2015) is $1.90/lb.  Given the relatively high prices for milk fat recently, should ration formulation change in response to rising prices?

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Nutritional Concepts for Feeding New Corn Silage

Rick Grant, William H. Miner Agricultural Research Institute, Chazy, NY

Across the US, corn harvest is either underway or completed. Most dairy farms will now have two sources of corn silage to feed: last year’s carryover silage which has fully fermented and steeped plus new-crop corn silage. Some farmers may be faced with feeding immature corn silage which adds yet another feeding challenge. Minimizing variations in herd productivity with changing sources of corn silage requires a good understanding of what happens to the nutritive value of silage with time in the silo.

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TTNDFD: A new test for evaluating forages for high producing dairy cows

Dr. Dave Combs, Professor, Department of Dairy Science, UW-Madison

Fiber is an essential component of diets for dairy cattle. In high producing dairy cows, about 20 to 25% of the energy for milk production comes from digested fiber in the ration. Neutral detergent fiber (NDF) is a forage test that measures the total amount of fiber in a feed.  NDF represents a ‘bulky’, slow to digest feed component, which can restrict feed intake and milk production. Forages are tested for NDF and lactating dairy cow diets are typically formulated to contain 28-35% NDF.

The digestibility of NDF also profoundly affects intake and milk production. Fiber digestibility can have a much greater impact on milk production than the digestibility of any other feed component. For example, kernel processing can improve starch digestibility of corn silages by as much as 8 to 10 percentage units. This improvement in starch digestion can increase milk production by 2 to 5 lbs. NDF digestibility in a forage like alfalfa or corn silage will vary from around 20% to over 60%. In a dairy ration containing about 35% corn silage, a doubling of fiber digestibility would increase the digestible energy enough to support up to 7 lbs more milk per day. Fiber digestibility is affected by growing conditions, plant genetics and forage maturity.

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How does variation in NDFd affect your ration balancing?

The lower milk prices of 2015 likely have you reviewing your rations and looking for areas to cut costs.  An important question, as part of your review, is how accurately are you at predicting or supplying nutrient demand relative to the degree of variation in digestion that occurs on the dairy?  It may be greater (or less) than you think, but until you know you could be over feeding expensive supplements such as rumen protected amino acids.

There is not a lot of research in this area, but over the last couple of years we have been looking at available data that may help nutritionists reduce cost – while maintaining milk production.  For this newsletter, we will reiterate pertinent points from past newsletters, as-well-as other research to assist you with WHY the variation is costly and WHAT you can do to reduce it.

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Heat Stress and Forage Feeding Approaches – Part 2

Rick Grant
William H. Miner Agricultural Research Institute


Feeding Management during Heat Stress

Feeding more of the ration at night during heat stress is a common recommendation, but recent research suggests it may be counterproductive. When a higher percentage of feed is offered at night during heat stress, cows tend to eat quickly – essentially slug feed – according to recent research from Penn State University. When a substantial portion of the daily feed is offered at night, cows have a greater rate of intake and insulin response. Perhaps cows want to eat quickly so they can lie down because resting is the normal dominant behavior at night. Actually, some nutritionists recommend greater dietary forage content at night to slow the eating rate which ought to lessen the risk of sub-acute acidosis.

Multiple nighttime feedings may be better, but are likely not practical. Aharoni et al. (2005) found that the energy expenditure of nighttime fed cows was lower than daytime-fed cows and their efficiency of energy use for milk production was greater. Presumably, cows produced less metabolic heat during the daytime and more during the cooler evening hours. Daytime-fed cows were fed at 30% of their daily allocation at 6:15 am, 20% at 10:00 am, 25% at 3:30 pm, and 25% at 7:00 pm. In contrast, the night-fed cows received 20% of their daily feed at 6:15 am, 30% at 3:30 pm, 25% at 7:00 pm, and 25% at 9:00 pm. We need to learn more about timing of feed delivery to heat-stressed cows.

Perhaps the best advice for now can be found in recent Italian research that showed that cows fed primarily in the morning – although most common – was actually least suitable for cow comfort during heat stress. Compared with cows fed in the evening or either in the morning and evening, cows fed in the morning only were more heat stressed and had higher rectal temperatures and breathing rates. This makes sense. Feeding early in the morning or evening avoids stacking digestive and ambient heat loads on the cow.

Forage and Nonforage Sources of Fiber

We all know that cows require adequate fiber for proper rumination, rumen function and VFA production. Cows require a physically effective NDF content of 21 to 24% of dietary dry matter, or about 75% of total NDF from forages. Adequate fiber is essential to help prevent rumen acidosis and high quality forages are critical. Highly digestible forage NDF will help to reduce the overall heat load on the cow and provide the proper amounts and ratios of VFA to maintain milk and milk component synthesis. When high quality forage is not available, some research has also indicated that substituting byproduct NDF for the lower digestibility forage NDF can improve milk production during heat stress (i.e. soybean hulls, beep pulp, and similar nonforage sources of fiber). Forage NDF can be reduced from 75% to 60% of total NDF under heat stress and still achieve efficient fiber fermentation.

Recent Asian research with cows under extreme heat stress conditions (THI of 86-92 during day, 74-81 at night) found that Continue reading

Heat Stress and Forage Feeding Approaches – Part 1

Rick Grant
William H. Miner Agricultural Research Institute

Summer’s heat and humidity are fast approaching. As always, we need to be prepared with effective heat abatement systems. Unless a cow is properly cooled, adjusting dietary ingredients and feeding highly digestible forages will not result in the expected responses in rumen fermentation, feed intake, or milk production. Our modern dairy cows have been selected based on heat-producing processes such as milk synthesis and consequently heat abatement has become ever more critical. Recent research indicates that cows become heat stressed at a temperature-humidity index (THI) of only 65 to 68.

Heat Stress Makes Cows Stand and Ruminate Less

As air temperature increases from the mid-70s to about 100oF, eating decreases by 46%, ruminating decreases by 22%, standing increases by 34%, and drinking increases by 30%. Higher producing cows (>70 lb/cow/day) are typically more sensitive to heat stress than lower producing cows, especially for resting, ruminating, and standing activity. Unabated heat stress can easily reduce intake by 10-15% or more and seriously compromise forage digestion.

Body temperature mediates the cow’s standing and lying response to heat stress. Cornell researchers found that during heat stress conditions, core body temperature appears to control whether the cow lies down or stands. The cow will stand up once her temperature reaches ~102.0oF and won’t lie back down again until her core body temperature reaches ~100.9oF. Research published in 2015 by Arizona and Missouri researchers confirmed that cows with elevated core body temperatures stood longer in an effort to dissipate heat and rested less. The bottom line is that cooled cows lie down longer, ruminate more, and have rumen conditions more conducive to efficient fermentation.

Heat Production and Forage Digestion

The cow’s total heat production consists of the heat increment from digestive fermentation and nutrient metabolism plus heat from basal metabolism and activity. For the lactating dairy cow, the heat increment comprises about 67% of the heat generated. Heat generated by fermentation is substantial and it varies with diet – especially the forage component. This heat load is an energetic burden to the heat-stressed cow because otherwise productive energy must be used to cool the cow’s body temperature.

With heat stress, we must focus on high NDF digestibility of forage and nonforage feeds to reduce the heat increment per unit of net energy supplied to the cow. Over the range in diets that might commonly be fed to dairy cows, from high to low heat increment, we can easily observe changes in metabolic heat loads that equate to 3 to 6oF – which means the cow consuming the more digestible diet has far less heat load to dissipate (Chandler, 1994). Basically, forages that contain more undigested NDF (uNDF) plus relatively more slow-digesting than fast-digesting NDF, will result in greater heat production during fermentation.

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How Much NDF Can a Cow Consume?

Rick Grant
William H. Miner Agricultural Research Institute


NDF Intake System and Optimal NDF Intake

Consumption of NDF by dairy cows is related to rumen fill and intake potential of a forage or ration. Dr. Dave Mertens developed the NDF Intake System to account for both forage quality and cow productivity, and it determines the maximum proportion of forage in the ration that does not limit intake or performance of the cow. Optimal NDF intake occurs at the point of maximum milk production and is ordinarily about 1.25 ± 0.10 % of body weight per day (mean ± standard deviation). It is important to understand that the optimal NDF intake is not the maximum NDF intake, but instead it is the NDF intake that maximizes milk production. Mertens (2009) provides a complete discussion of the NDF Intake System, its assumptions, and applications in ration formulation for dairy cows.

NDF Intake Targets and Time Budgets

The target of 1.25% of body weight applies to cows in mid-to late lactation. This target NDF intake varies with parity and stage of lactation. For example, first-lactation cows have a smaller ability to process NDF than mature cows. Table 1 was developed by Dave Mertens to provide more specific NDF intake targets for various stages of lactation.

Table 1. NDF intake targets throughout lactation and the dry period (Mertens, 2009).


We also know that the NDF amount and digestibility will influence NDF intake for cows at a given stage of lactation. In Table 2, we have some data from a study conducted at Miner Institute in which we compared lower forage diets (49 to 53% of ration DM) to higher forage diets (64 to 67% of ration DM). Continue reading