Cows

Risk factors for bovine viral diarrhea virus infection in dairy farms

Lucas Pantaleon

Bovine viral diarrhea virus (BVDV) is a common disease in cattle which causes significant economic losses around the globe. The severity of the negative financial impact of the virus varies based on the immunity status of a given population and the pathogenicity of the viral strain. In populations that are susceptible to BVDV or the introduction of a highly pathogenic strain, understandably will lead to high economic losses in that herd.

In breeding cattle, the virus causes reproduction disorders (abortion, prolonged gestation, reduced fertility) and has a negative impact on productivity because of culling, morbidity, and mortality. The disease could manifest as acute, subclinical, and persistent infection forms. All forms of BVDV cause health issues in affected herds and lead to the presence of persistently or temporarily infected animals. The circulation of the virus in the population is facilitated by the variety of forms that the disease can take, regardless of the presence of high viral antibodies.

The spread of the bovine viral diarrhea virus in dairy herds

The virus can cross the placenta and cause infection of the fetus early during pregnancy, resulting in the birth of persistently infected (PI) cattle. The most important sources of infection are the PI animals. On the other hand, healthy adult cattle or calves that become transiently infected (TI) are normally of a minor significance with regards to disease spreading.

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Cereals

Feeding barley forages in high-concentrate diets for lactating cows

Alvaro Garcia

Growing forages in arid regions of the world is one of the biggest constraints to profitable intensive dairy production. Under these conditions dairy production systems rely heavily on forages that require less water together with mostly imported grain. In addition, dairy rations tend to include higher concentrate to forage ratios since it makes more economic sense to transport energy dense feeds (grain) than roughage.

In Israel for example, total mixed rations (TMR) fed to dairy cows contain 33–36% roughage, a bare minimum needed to supply 18–19 % neutral detergent fiber (NDF) needed in order to minimize the risk of acidosis. As a result, winter forages such as wheat (Triticum spp.) supply nearly 70% of the annual forage, complemented with corn silage during the summer irrigated with recycled water.

Wheat and barley forages

Nearly 40,000 Ha of wheat both for silage and hay are grown yearly as the main winter forage in Israel, followed by barley (Hordeum vulgare L.) with only 2,500 Ha for silage and 3,500 Ha as grain for feeding. Wheat is an important crop in this system since it provides flexibility, switching from grain to forage and vice versa depending on environmental conditions.

Barley’s yield, quality, and nutritive value are less known at the present time particularly of those cultivars grown for silage in the same fields and under similar conditions as wheat. One of the advantages of barley in this semi-arid environment is that it apparently uses water more efficiently, it has early vigor, and matures faster compared to wheat resulting in higher yields per Ha.

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Calf

Oral electrolytes to treat diarrhea can lead to hypernatremia in water-restricted calves

Alvaro Garcia

Diarrhea is the first leading cause of calf losses in dairy production systems. Affected calves soon become dehydrated and lose weight, and if not treated accordingly may soon die. A specific drug therapy to treat the causative agent should thus be accompanied by fluid therapy to reestablish the losses of water and minerals.

As a result, oral electrolyte solutions are very important when dealing with severe diarrhea in baby calves, with several types available in the market. These solutions may differ depending on the main intended purpose (i.e. isotonic solutions, electrolytes plus energy sources, etc.), and knowing which one to choose is critical for a prompt recovery.

The wrong fluid therapy can result in unbalances in the body electrolytes or even further losses aggravating the calf’s condition. One thing to consider however is that most milk replacers are made with cheese whey. As a result, these milk replacers have higher concentrations of sodium (up to 2% or 17–80 mmol/L). In addition, they also contain high concentrations of lactose ranging from 140 to 230 mmol/L.

This results in higher overall solids per liter of solution and greater osmolality resulting in more body fluid passing into the intestinal lumen. If in addition sugar (dextrose) and minerals (electrolytes) are added to the solution, then its osmolality can easily exceed 600 mOsm/kg.

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Factory

Adding molasses to dry cow diets improves intake and health of dairy cows

Alvaro Garcia

The transition period of dairy cows is characterized by changes in behavior, hormonal patterns, and increased metabolic and nutrient demands. Cows in late gestation (2-3 weeks to calving) undergo changes in metabolism and a mismatch between dry matter intake/nutrient uptake and their requirements, which prompts the mobilization of body stores, mainly fat from adipose tissue and glycogen from the liver.

These changes also predispose to metabolic disorders such as ketosis, acidosis, and displaced abomasum. Research has shown that feeding lower dietary energy including more fiber in the diet, promotes intake after calving, and results in less body fat mobilization. It has also been suggested that moderate energy intake pre-calving may positively impact cows’ fertility.

Which is the most suitable diet for dry cows?

Today’s suggestions are to feed dry cows low energy diets [1.30 to 1.39 Mcal of net energy for lactation (NEL)/kg of dry matter (DM)] during the entire dry period. One limitation is that high straw diets result in rumen filling at a stage of the pregnancy where the fetus is already occupying more space, and that they may also increase the risk of feed sorting.

Recent research however has also suggested that high fiber:starch ratios inhibit the expression of the genes regulating rumen papillae growth. The challenge is to feed fibrous roughages while promoting the development of an adequate rumen papillae surface needed to absorb the sudden increase in volatile fatty-acids resulting from the highly digestible feeds available in early lactation.

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Milking cows

Removing S. aureus from teat cup liners using automatic cluster flushing

Alvaro Garcia

Mastitis is an inflammation of the udder caused by microorganisms that enter the gland through the teat canal. Once inside the gland, these organisms find ideal conditions in which to multiply and, in turn damage the lining of the milk ducts, cistern, and alveoli. Contagious bacteria are spread from a cow with an infected udder to a healthy cow.

Transfer of pathogenic bacteria between cows usually occurs at milking time. Milker hands, towels, or the milking machine can all act as reservoirs for contagious bacteria. The major contagious pathogens are Streptococcus agalactiae, Staphylococcus aureus, and Mycoplasma spp.

The most important approach to minimize the transmission is to address potential sources of contagion at milking time. Cleaning the cluster between milkings has been used in commercial farms for quite some time. However, submerging the cluster in hot water (85°C) has been found not very effective in reducing the number of new intramammary infections.

Similarly, flushing has not achieved the complete eradication of new infections. Flushing with just cold water is frequently used in commercial farms since it is less costly, does not damage the equipment that much, and reduces the risk of residues in milk. Adding disinfectants to the water has also been explored as an alternative solution.

Using an iodine solution has been demonstrated to reduce intramammary infections by Corynebacterium bovis and coagulase-positive staphylococci. Given these results it seems that teat cleanliness, teat dipping, and an adequate milking routine are more effective in reducing the spread of infections than the attempts at washing or disinfecting the unit.

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Tractor working with forage

Optimizing nitrogen fertilization in timothy grass

Alvaro Garcia

Timothy grass (Phleum pratense) is a perennial grass originally from northern Europe. It is a tall grass species which can grow up to 1.5 m at the reproductive stage. It performs well in heavy, poor sandy soils, and is resistant to cold weather and dry conditions. As other grass species it requires adequate soil nitrogen for optimal growth.

Timothy and other cool season grasses generally respond well to nitrogen fertilization, with 20 to 25 kg of herbage dry matter produced yearly per kg of nitrogen/hectare. Response is related to the original nitrogen availability in the soil, with a greater response in more deficient areas.

Nitrogen fertilization

The timeline of the nitrogen application also affects the quality of the sward. When applied later into the growing season it leads to more vegetative growth compared to tall, more hardened stems earlier in the season. This is an important consideration depending on the region since vegetative growth is desirable for quality, although it may also lead to more winter damage.

It is important then to optimize fertilization rates such that they not only increase herbage dry matter production, but also result in forage that withstands the cold season while still maintains adequate quality. As with other grasses, nitrogen fertilization increases not only the crude protein content of the plant but also its concentration in nitrates, which could be potentially toxic to ruminants.

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Dairy cows

Fasciolosis in dairy cows

Lucas Pantaleon

Fasciolosis in a zoonotic disease. The infection is caused by Fasciola hepatica and Fasciola gigantica flukes and juvenile forms affecting the liver parenchyma, as well as adult forms that migrate to the bile ducts. The disease is responsible for significant economic losses to dairy cattle producers, such as liver condemnation during slaughter.

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Cotton harvester

Inclusion of hydrolyzed cottonseed protein in calf starters

Alvaro Garcia

Young heifer calves represent the future of a dairy farm and need to be fed so they can express their full genetic potential during their productive life. Many challenges can impair their optimal development such as management flaws, disease, and sub-optimal nutrition. Despite the farmer’s efforts some of these stressors may show-up and compromise their well-being, negatively impacting their development.

Vitamin deficiencies for example (i.e. vitamin E), affect their ability to cope with oxidative stress and hamper the development of their acquired immunity. Taking adequate measures to reduce stress spares natural antioxidants needed for other important body functions. Some feeds possess antinutritional factors, and when included in the ration can further challenge normal metabolism.

Cottonseed meal is a traditional feedstuff commonly used in mature dairy cows. Its competitive price compared to other meals of plant origin makes it an attractive feedstuff. It is however a relatively poor source of the amino acids lysine and methionine, and contains gossypol, a phenolic aldehyde that permeates cells and inhibits several dehydrogenase enzymes.

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Sunflower

Crushed sunflower seeds modify milk fatty acid profile in dairy cows

Alvaro Garcia

It is currently accepted that acetate produced from fiber fermentation in the rumen, supplies nearly 40% of the building blocks for de-novo milk fatty acid synthesis in the mammary gland. Of the remaining milk fat, 10 % comes from circulating fatty acids mobilized from fat stores, and 50% coming arises from the diet.

Dietary phospholipids have health-promoting effects in humans such as inhibition of colorectal cancer, reduce the prevalence of gastric ulcers, and decrease the absorption of cholesterol. The latter likely results from the physical intestinal interaction between phospholipids and cholesterol, decreasing the absorption of both.

The fatty acid (FA) composition of phospholipids influences this bonding since their long-chain saturated FA interact more strongly with cholesterol than the unsaturated form. These phospholipids are in the milk fat globule membrane and dairy products rich in this membrane (i.e. buttermilk) are good sources of these phospholipids.

Dairy cows’ milk fat has 0.2 to 1% phospholipids with sphingomyelin constituting approximately 20% of them. Since sphingomyelin has a high proportion of long-chain saturated FA, this allows for a better interaction with cholesterol. These strong sphingomyelin-cholesterol bonding is essential for cell function. They are also present in the milk fat globule membrane, suggesting that this complex may play a role in the hydrolysis and absorption of milk fat by the calf.

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Vineyards

Feeding grape pomace reduces methane emissions from lactating dairy cows

Alvaro Garcia

The wine industry leaves behind an interesting coproduct which is called grape pomace. It consists of the solids that remain of grapes after they are pressed to remove its juice, and it contains the skins, pulp, seeds, and stems. In the alcohol beverage industry, water is added and allowed to ferment to produce “grappa”, a well-known alcoholic beverage originating in Italy.

Grape pomace is also used nowadays as a feedstuff for cattle, fertilizer, or to extract from its bioactive compounds such as polyphenols. Nearly nine million tons are produced annually around the world, with well-known wine regions being the main source of it. Its availability is not to be discounted since they constitute one fourth of the grape weight before its fermented into wine.

The dairy industry is well known for producing highly valued dairy products however it is also blamed for increasing the carbon footprint of agriculture. Industry coproducts such as grape pomace which are relatively inexpensive and need to be disposed-off in an environmentally friendly way are often used as feedstuffs in dairy cow diets. In addition, they are also considered not contributing significant volumes of greenhouse gases, since any emitted are mostly assigned to the primary product, in this case the alcohol beverages.

Grape pomace is rich in condensed tannins which have been shown to reduce methane production when fed to ruminants. In addition, these coproducts reduced in milk fat with higher proportions of polyunsaturated fatty acids which are beneficial to human health. In countries with grass-fed dairy systems and a strong wine industry, such as Australia, this coproduct is used to stretch the forage supply and not overgraze pastures during the dry months of the year.

In the US and particularly in the wine region of the west coast, the use of grape pomace has been also a tradition, mostly to reduce feed costs. There is not much information though on its nutritional value and its variability depending on the types of grapes used to make wine. As a result, there is also not enough research performed on its effect on dairy cow milk production. There’s not much research on its relatively high concentration of polyphenols and their impact on methane production emissions.

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