Real Science Exchange - Potential for low-forage diets to maintain milk production in forage-limited situations with Dr. Adam Lock, Michigan State University; Dr. Bill Weiss, Professor Emeritus, The Ohio State University

Potential for low-forage diets to maintain milk production in forage-limited situations with Dr. Adam Lock, Michigan State University; Dr. Bill Weiss, Professor Emeritus, The Ohio State University

02/25/25 • 48 min

In times of limited forage, dairy producers may need to feed diets lower in forage than is typical but would like to maintain milk production. In this study, two diets similar in neutral detergent fiber (NDF), starch, and crude protein with different amounts of forage were fed to 32 mid-lactation Holstein cows in a crossover design. The control diet (CON) contained high forage (55.5% of diet dry matter) with no supplemental fatty acids or amino acids. The low-forage diet (LF) contained 36.6% forage along with supplemental fat and rumen-protected methionine and lysine. As forage was removed from the LF diet, it was replaced with byproducts and high-moisture corn was replaced with dry corn. (4:42)

Dr. Lock added fat and amino acid supplements to the LF diet to not lose milk production. The fat supplement was a palmitic-acid-rich prill. Dr. Lock does not think the response would have been the same if a different fat supplement had been used. The LF diet was higher in fat and palmitic acid, but most other fatty acids were fairly similar between the two diets. (16:25)

Milk yields were similar between the two diets. Cows on the LF diet consumed about 1 kg more dry matter each day than CON-fed cows. Cows fed the LF diet also had higher milk fat and milk protein yields and content which led to an approximately 2 kg increase in energy-corrected milk compared to cows fed the CON diet. Dr. Lock believes the fat and amino acid supplementation were a key part of achieving these results, and they would not have seen the same response if those supplements had not been added to the LF diet. The LF diet spared around 5.5-6 kg of forage per day, and cows gained body condition. (22:03)

Dr. Weiss asks Dr. Lock to speculate if low-forage diets fed for longer periods would have negative health impacts. Dr. Lock feels that usually production would be negatively impacted by cow health issues, which was not the case here. However, if high-moisture corn had been used in the LF diet, he predicts they would have seen negative impacts. (27:18)

What about low-forage diets for early lactation cows? Dr. Lock suggests looking at diets in other parts of the world where forage is limited and see how dairy producers manage diets in those instances. He speculates that lower forage could be successfully implemented in early lactation cows after the fresh period. (31:09)

Dr. Weiss and Dr. Lock discuss the apparent improved digestibility of the LF diet given the increased production. While byproduct ingredients are often more fermentable in vitro, the results don’t always translate in vivo. Palmitic acid supplementation has been shown to improve fiber digestibility, so that may have happened in this experiment. (32:12)

On the protein side, we’ve moved away from talking about crude protein in the diet and toward amino acid concentrations. Dr. Lock would like to see the same trend in the industry for fat in the diet. A good leap was made recently from ether extract to total fatty acids, and he hopes to see individual fatty acids as the next step in that evolution. He recommends two questions be asked when considering a new fatty acid supplement. What is the fatty acid profile? What is the total fat content? The appropriate fatty acid profile is going to depend on the basal diet and what type of cow is being fed. Dr. Lock’s preference is a palmitic: oleic acid blend around 70:20 or 60:30 early in lactation, with a higher palmitic blend later in lactation. He expects the current work with different oilseeds to provide some good recommendations for feed ingredients to incorporate to increase dietary fat. (35:53)

As genetics continue to improve and nutrient requirements of cows continue to increase, is it conceivable that someday we are going to purposefully decrease fiber in the diet? While that may be the case, Dr. Lock reminds listeners that about half of milk fat comes from acetate and butyrate produced in the rumen, so fiber is still going to be critical. While we may lower the forage in a diet, forage quality is going to remain very important. (39:45)

The panel wraps up with their take-home messages from this paper. Clay looks forward to more research with a factorial design to further evaluate low-forage diets. Dr. Weiss reminds listeners there’s no one recipe for diets to achieve high yields of milk components. Lastly, Dr. Lock is excited about the future of research in this area and refining diet formulation in the area of fat supplementation. (43:21)

You can find this episode’s journal club paper from JDS Communications here: https://www.sciencedirect.com/science/article/pii/S2666910223001084

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You can find this episode’s journal club paper from JDS Communications here: https://www.sciencedirect.com/science/article/pii/S2666910223001084

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Previous Episode

Transitioning to Success: The Intersection Between Nutrition, Health and Reproduction with Dr. Jose Santos, University of Florida

This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series. You can find it at balchem.com/realscience.

Dr. Santos begins with a timeline of events that occur during the cow’s transition from the dry period to her exit from the fresh pen. He suggests that cows should be dried off at around 230 days of gestation, then moved to a closeup group at 250-255 days gestation which is around three to three-and-a-half weeks before calving. Dr. Santos recommends keeping multiparous cows separate from primiparous cows and feeding to minimize metabolic disorders in early lactation. After calving, cow health needs to be monitored for early detection and treatment of disease. In addition, diets that do not limit voluntary dry matter intake should be fed. During the early postpartum period, controlling excessive weight loss and lipid mobilization is the goal. (00:27)

What is the association between time spent in the closeup pen and disease? Research shows that around three to four weeks in the prepartum group is associated with the lowest risk of morbidity, maximum milk yield and highest pregnancy rates. How does a change in body condition during the first 65 days in milk impact cyclicity? How does 90-day milk yield impact cyclicity? Cows that lose one or more units of condition are less likely to be cyclic at the end of the voluntary waiting period. There is a small statically positive association between milk yield and cyclicity. Dr. Santos’ first take-home message is to avoid excessive body condition loss after calving. Cows should lose no more than 0.5 body condition units from the week before calving to the first AI. This can be accomplished by minimizing over-conditioned cows at dry-off and reducing the risk of disease in early lactation. (6:13)

What about feed efficiency? Dr. Santos describes experiments comparing the 25% most efficient to the 25% least efficient cows. All cows produced the same amount of energy-corrected milk, but the most efficient cows ate four kilograms less feed each day. The risk of morbidity and the culling rate was the same for both groups, as was reproductive performance. Dr. Santos suggests we should not be afraid of selecting for feed efficiency while still optimizing intake in early lactation. (18:23)

Morbidity negatively impacts intake in early lactation. Around one-third of cows are affected by disease in the first three weeks of lactation and almost 80% of the first disease diagnoses occur during the first three weeks postpartum. The earlier in lactation disease occurs, the longer the legacy effects from that disease can impact cow health and performance. Dr. Santos describes an experiment in beef cattle evaluating how an inflammatory response impacts nutrient partitioning away from performance. Early lactation morbidity not only makes a cow not want to eat, it also may shift nutrients away from production toward survival, resulting in fewer nutrients available for milk production and reproduction. Dr. Santos describes a series of experiments evaluating the impact of early lactation disease diagnosis on reproductive performance. Dr. Santos’ second take-home message is to stimulate dry matter intake and minimize disease in the early lactation period. (22:21)

How can we formulate diets that will improve reproduction? First, we should formulate diets that reduce the risk of disease. Then we should incorporate nutrients that are known to improve reproduction in cows. Dr. Santos describes how supplementation with rumen-protected choline decreases triglyceride accumulation in the liver and improves milk yield. He also details the mechanisms of using acidogenic diets to reduce hypocalcemia. He recommends not using these diets for heifers and feeding them for around 21 days to cows rather than the entire dry period. Dr. Santos feels that forage quality has been neglected in the transition period and details how improved fiber digestibility during the transition period can have longer-term impacts. Lastly, he recommends feeding 1-1.5% supplemental fat in early lactation diets for improved reproduction and milk yield without negative impacts on body condition. In closing, Dr. Santos presents a summary of diet formulation recommendations for transition cows. (34:13)

Dr. Santos leads an engaged question-and-answer session with the webinar audience. (51:11)

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Next Episode

The Benefits of Mitigating Heat Stress in Dairy Cattle with Dr. Lance Baumgard, Iowa State University

This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series. You can find it at balchem.com/realscience.

Dr. Baumgard begins with an overview of the structure and function of the gastrointestinal tract. More than 75% of an animal’s immune system resides in the gut. The focus of this webinar is how heat stress initiates leaky gut, how that leaky gut then influences the immune and hormonal systems, and ultimately, how that reduces productivity. (0:22)

Dr. Baumgard compares the metabolism of a cow 200 days in milk to a cow 10 days in milk. The 200-day cow is experiencing ad libitum intake and gaining weight. Her insulin levels would be high, and NEFAs would be low. On the other hand, the 10-day cow is experiencing suboptimal intake, and her insulin levels are the lowest they’ll ever be during the production cycle. Body tissue is mobilized, and NEFAs will increase. Research shows it takes 72 grams of glucose to make one kilogram of milk. Any disruption to the gluconeogenic pathway has the potential to decrease milk yield. (6:38)

Heat stress is estimated to cost the US dairy industry $1.7 billion each year. Regardless of climate change, heat stress will continue to be an issue because all economically important phenotypes in animal agriculture are heat-producing processes. Dr. Baumgard’s lab has been investigating the biology of heat stress to implement more effective mitigation strategies. (9:09)

How much of the reduction in feed intake during heat stress explains the reduction in milk yield? A pair-feeding experiment comparing thermoneutral to heat-stressed cows showed that about 50% of the reduction in milk yield during a heat wave is due to a reduction in feed intake. The thermoneutral cows lost weight in response to decreased intake, and their NEFAs increased. Heat-stressed cows did not have an increase in NEFA. Heat-stressed animals fail to mobilize adipose tissue despite their endocrine profile predicting that they should. However, insulin is high when we would expect it to be low, and that response to heat stress is highly conserved in all species. (10:43)

Heat-stressed cows produced about 400 grams less lactose per day than their pair-fed thermoneutral controls. This is nearly a pound! Is the liver producing 400 fewer grams of glucose each day? Or is some other extramammary tissue using more glucose per day? Dr. Baumgard’s work suggests that the immune system is where the 400 grams of glucose go in heat-stressed animals. During heat stress, vasodilation at the body surface occurs, with concomitant vasoconstriction in the gut. The gut epithelium is very sensitive to reduced oxygen delivery that would result from the vasoconstriction, and tight junction proteins do not function properly, resulting in a leaky gut. This results in an infiltration of antigens into the body, which causes an immune response. (15:36)

Dr. Baumgard details how insulin fits into these immune responses via the Warburg effect. An activated immune cell prefers glucose and needs it in high quantities. The activated cell switches from the Kreb’s cycle to generate ATP to aerobic glycolysis. This requires high insulin. The immune system requires approximately one gram of glucose per kilogram of metabolic body weight per hour. (25:03)

By far, the biggest impact a dairy producer can make to alleviate heat stress is to modify the environment physically: shade, fans, soakers, misters, etc. Investing in cooling cows improves production efficiency and profitability, summer fertility, animal welfare and health, and sustainability. Other important heat abatement considerations include adequate water availability, reducing walking distance to the parlor and time in the holding pen, and improving ventilation. Dry cows should also be part of any heat abatement strategy, as the benefits of cooling dry cows extends far into lactation. Dr. Baumgard also discusses different dietary management strategies for heat stress situations. (32:43)

In summary, heat stress decreases almost every metric of productivity and costs everyone in the industry. Reduced feed intake is only part of the problem. Heat-induced leaky gut results in biological consequences incredibly similar to any other immune activation, such as mastitis or metritis. For dairy producers, heat stress abatement should by far be their biggest priority. Once those infrastructure improvements are in place, dietary interventions are another good strategy to minimize the negative consequences of heat stress. (47:43)

Dr. Baumgard takes questions from the webinar audience. (49:22)

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