Several cows eating hay in a dairy farm

Evaluation of supplemental carnitine in dairy cows during the pre- and postpartum period

Alvaro Garcia

The transition period is the most challenging time for a dairy cow. Right after calving cows start producing colostrum first and then milk in large amounts, depending on their genetic make-up. At this point in time however, they are in recovery mode from calving, and a combination of general discomfort/pain and hormonal changes results in a significant reduction of feed intake.

This mismatch between nutrient requirements for production and nutrient uptake through feed intake, results in imbalances, with the supply of energy being the more striking. One example of hormonal changes is the decreased production of insulin that leads to decreased glucose utilization by insulin-sensitive organs, which is essential for milk production. Concomitantly, body fat reserves are mobilized to supply additional energy which increases the non-esterified fatty acids (NEFAs) blood concentration.

The abundance of circulating NEFAs leads to increased availability of the product from their degradation, acetyl-CoA, which may exceed the capacity of its incorporation into the carboxylic acid cycle. As a result, end-products normally utilized in ketogenesis will build-up, such as acetone, acetoacetic acid, and beta-hydroxybutyric acid (BHBA).

L-carnitine helps to handle excessive non-esterified fatty acids

The increased circulation of NEFAs leads to triacyl glyceride synthesis later deposited in the liver. To handle the excessive NEFA availability L-carnitine is needed which is essential to transfer fatty acids into the mitochondria for their oxidation. L-carnitine is synthesized endogenously, and it is essential in the initial steps of the ß-oxidation of free fatty acids. When in short supply, all the events described above can happen leading to frequent metabolic problems in transition cows such as fatty liver and/or ketosis.

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Swiss Brown cow, portrait

Betaine allows dairy cows to better cope with heat stress

Alvaro Garcia

Alleviating heat stress is critical to sustain milk production under warm weather conditions. Maintaining optimum nutrient balance and providing highly palatable, digestible feeds and ample supplies of fresh, clean water, along with shade and ventilation, will go far towards keeping cows comfortable and milk production up.

Heat stress from high environmental temperatures can be compounded by mistakes in managing and feeding cows. Water is the first concern during periods of high temperatures. Water physical properties (heat conductivity and latent heat of vaporization) help transfer heat from the body to the environment. Dry matter intake of lactating cattle is affected when ambient temperatures are outside of the cow’s “comfort zone” (5 to 25 ºC). When ambient temperatures increase beyond 25 ºC, the cow typically reduces intake and as temperatures continue to rise it can finally go off-feed.

Less ingestion of dry matter in hot weather

Dry matter intake can decrease by around 150 g of feed for each degree above 25 ºC. This is just a physiological mechanism by which the cow attempts to reduce the heat increment that results from feed fermentation and metabolism. Heat is produced as a result of microbial fermentation in the pre-stomachs. Low quality, stemmy forages generate more heat of fermentation, contributing to the animal’s total heat load.

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Silage balls in a foggy landscape

Baling grass silage with tannins reduces environmental nitrogen load

Alvaro Garcia

The fate of nitrogen (N) ingested by dairy cows is approximately 34% in milk protein synthesis, 34% eliminated in the urine, 27% in the feces, with only 5% retained to be used in other body processes. These figures show that close to 60% of the nitrogen intake ends up being a source of environmental N load.

Not only is N tied-up in urine and feces but it also results in gaseous N losses through nitrous oxide which is also a greenhouse gas nearly 300-fold more potent than carbon dioxide. Ammonia gas production is also of concern since it is hazardous both for humans and livestock. As a result, improving N partitioning will have an effect in the environmental load associated with livestock production as well as air quality.

What is the effect of adding tannins to the silage on cow’s nitrogen metabolism?

Oak tannins applied to forage before baling it for silage improve protein partitioning in the cow lessening the environmental N load. Research has shown that adding tannins to forages before ensiling can lead to a reduction in ammonia production. Tannins have also been used to protect fermentable protein from rumen degradation which is later digested once it is freed from the tannin complex once it reaches the more acidic pH of the abomasum. This latter effect results in less plasma urea N, less milk urea N, and reduced N excretion in the urine.

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Holstein cow feeding grass

Feeding yeast improves performance of dairy cows under heat stress

Alvaro Garcia

Hot summer temperatures are a highly limiting factor for milk production of dairy cows. To maintain body temperature, cows reduce intake, which decreases the heat increment that results from rumen fermentation. In order to improve milk production under these conditions it is necessary to restore intake, and/or improve nutrient digestibility. Since forage fiber requires more time for its degradation in the rumen, it produces more heat of fermentation than concentrates.

Less fiber in the diet however, results in less chewing, reduced saliva production, more grain fermentation, and ultimately a more acidic rumen pH. These changes shift the pattern of fermentation from predominantly acetate to propionate→lactate, risking the appearance of sub-clinical or clinical rumen acidosis. Past research has demonstrated that feeding live yeasts or yeast cultures increases milk production of cows under heat stress.

Could Saccharomyces cerevisiae help cows under heat stress?

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Three cows eating total mixed ration (TMR)

Organic acid-based products can improve milk production

Alvaro Garcia

Mixers and total mixed rations (TMRs) are the feed delivery method of choice in modern dairy operations in confinement. Their greatest advantage is that they allow for more even delivery of nutrients, and a steadier rumen fermentation. In fact, it is this technology that has allowed cows to fully express their genetic potential for production, encouraging greater intakes, and higher milk yields.

Cow response however is associated to the quality of the feedstuffs included in the TMR. Individual feeds can suffer deterioration when exposed to less than ideal conditions (e.g. air, heat, moisture, etc.) that lead to proliferation of microorganisms, toxins, that reduce feed quality. Molds and yeasts for example have been known to consume organic matter in silages, reducing their feeding value and/or producing toxins detrimental to animal performance and health.

Organic acids inhibit the proliferation of bacteria and fungi

Several additives have been researched that inhibit the proliferation of microorganisms. Organic acids for example inhibit the proliferation of bacteria and fungi helping maintain the nutritive value of the feed and reduce potential mycotoxin toxicity. Their mechanism of action has been proposed to be by allowing hydrogen to enter the microorganisms cell membrane, thus reducing the pH in the cell cytoplasm. Propionic acid for example, has been demonstrated to reduce pH and temperature when added to the TMR.

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The Sun in the sky, sunset

Rumen-protected methionine helps in heat stressed cows

Alvaro Garcia

Warm weather in the US varies in length and intensity depending on the state and can lead to heat stress in dairy cows. It has been estimated that dairy production alone accounts for 37.5% (ca. $900 million) of the annual livestock production losses associated with heat stress. These losses are multi-factorial and mostly attributed to milk production, changes in milk composition, less than optimal reproductive performance, and culling rates.

There’s plenty of research on practices to cool-off cows by evaporative heat losses such as shade, fans, sprinklers, and tunnel cooling. Cows cope with excessive environmental heat conditions by several physiologic strategies such as evaporative heat loss (perspiration), increasing respiration rate (panting), reducing heat of fermentation (caloric increment) by cutting-off intake, and feed sorting to choose more easily digestible feed particles. There has been consensus in the past however, that a decrease in intake to reduce the caloric increment is the primary driver leading to decreased milk yield in cows subjected to heat stress.

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Brown cow's eye

Choline in close-up cows enhances immunity after calving

Alvaro Garcia

Early lactation is a challenging and stressful period for dairy cows. Several metabolic diseases happen during this period, which is characterized by a negative energy balance and metabolic imbalance. Most of these issues start as close-ups and result from faulty management and/or feeding practices. Over-conditioning cows during the dry period allows them to mobilize more fat after calving and make them prone to metabolic diseases early in the lactation.

Recently calved cows have reduced appetite and greater energy demands due to the sudden increased milk production. This results in greater fat mobilization and increased hepatic triacylglycerol deposits predisposing to what is known as fatty liver and even ketosis. There are also negative effects of excessive fat mobilization on the metabolism and the immune system (neutrophils). Blood neutrophil phagocytosis has been shown to decrease 14 days post calving in cows overfed during the dry period. Choline helps with lipid transport from the liver in very low-density lipoproteins (VLDL).

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Use of trace-mineral boluses on dairy heifers

Andrés Haro & Fernando Diaz

Among the nutrients required by ruminant animals are trace-minerals such as: iodine (I), cobalt (Co), copper (Cu) and selenium (Se). These minerals are required for several vital functions of the organism, fundamental to optimize dairy cow performance. When deficient they can induce pathologies such as metabolic problems. The uses of boluses for a slow release of some of these minerals in the rumen has recently received greater attention by dairy farmers.

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Types of corn silage and trace minerals affect dairy production

Alvaro Garcia

Forages and their fiber have a large effect on milk production, since they constitute the largest nutrient fraction in dairy cow diets. Their chemical composition together with their physical characteristics help maintain a healthy rumen environment critical to animal health and productivity. Corn silage constitutes the main forage used in dairy cow diets in several parts of the world.

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Calf portrait

Zinc chelates improved diarrhea and intake in young calves

Alvaro Garcia

Diarrhea or scours is the first leading cause of death in un-weaned heifer calves. It occurs most frequently between days 3 and 30 after birth, depending on the susceptibility of the individual animal and the cause of this multifactorial problem. According to the 2011 National Animal Health Monitoring System survey, diarrhea and digestive problems affect 25.3% of pre-weaned heifers and of these, 18.2% are treated. In addition, death rate in pre-weaned heifers is 7.8% with diarrhea accounting for 56.5% of this mortality.

Diarrhea is affected by pathogen exposure, calf management, environmental conditions, nutritional and immune status. Adequate amount and timely intake of colostrum is critical for calves to survive it. Once the intestinal epithelium is “closed” (first 1-2 days) to the initial absorption of large molecules, it then acts as a barrier to pathogens. The intestinal integrity of this epithelium is then critical to protect the young calf from bacterial challenges. It has been suggested that Zn is essential for normal function of this intestinal barrier, and the regeneration of its damaged epithelium.

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