Aspergillus-flavus

Aspergillus flavus and aflatoxins prevalence in feeds and raw milk

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Alvaro Garcia

Molds that produce mycotoxins are present in the environment and will grow readily on feedstuffs given the right conditions. The production of these mycotoxins in feeds is expressed mainly under conditions of environmental stress. The three more prevalent genus of molds are Aspergillus, Fusarium, and Penicillium.

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A little herd of cute Holstein calves on the grass

Trace minerals injection increases immunity in young dairy calves

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Alvaro Garcia

Diarrhea and respiratory disease are the two leading death losses in un-weaned heifer calves. Respiratory problems have increased in the last 20 years, causing more than 20% percent of all dairy calf losses. Heifers that survive continue to perform poorly as adult cows.

Calf deaths within the first 48 hours of life are significant and greatly influenced by nutrition, environment, and management. One of the most prevalent reason for these death losses is the inadequate passive transfer of immunity through colostrum received from the dam. Current guidelines suggest calves should receive 3–4 quarts of high-quality colostrum within 1 hour of birth and 3 additional quarts within the next 12 hours.

If colostrum ingestion is inadequate, esophageal feeders can be used making sure that 3–4 quarts are administered within 1 hour of birth. Pooling colostrum is also becoming popular with large farms because it increases the immune competence of the calves (or their ability to respond to a more diverse pool of pathogens).

Have you fed your calf enough colostrum?

One way to find out if colostrum has supplied adequate amounts of immunoglobulins (IgG) is to measure either IgG directly or serum total protein in blood serum. Serum total protein measured with a refractometer is highly correlated with serum IgG levels. Measuring serum total protein in a group of calves is more meaningful than individual readings; at least 80% of a group of calves should have serum protein levels of 5.5 g/dL or higher.

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A farm tractor spreading glyphosate on a crop

Glyphosate does not cause adverse effects in dairy cows

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Fernando Diaz

Glyphosate (N-phosphophonmethyl-glycine) is the most widely used herbicide, particularly in crops intended for animal feed. Given the controversy over its toxic effects, a German research group, led by K. Schnabel (2017 and 2020) conducted a feeding experiment to address these issues.

Since it is known that energy modulates the ruminal environment with possible consequences on glyphosate metabolism and effects on the animal, a first phase (2017) of the study focused on glyphosate’s effects in vivo on the productive performance and health of dairy cows fed rations with different concentrate feed proportions.

The objective of the second phase (2020) was to complete the above data by analyzing factors that could potentially be influenced by glyphosate such as hematological variables, immune cell phenotypes, oxidative status, and genotoxicity.

Experimental design

A total of 64 German Holstein cows were used in an experiment that lasted 17 weeks. After a week of adaptation in which all cows received the same feed, they were then separated in two groups: a GL group (GL) that received a ration including peas, wheat grain and wheat straw with glyphosate and a control group (CON) which received the same diet, but without glyphosate.

Both groups were in turn subdivided into one that received a diet with low concentrate inclusion (LC) composed on a dry matter (DM) basis of 21% corn silage, 42% grass silage, 7% straw and 30% concentrate, and another with a high concentrate level (HC) consisting of 11% corn silage, 22% grass silage, 7% straw and 60% concentrate.

Overall health

The first experiment recorded body condition score (BCS), weight, DM intake and milk production. Blood serum was analyzed for ß-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA) and glucose, with the energy balance calculated. Milk was tested for glyphosate residues. It is worth noting that although the plants were grown on a plot that did not receive glyphosate for at least three years, the time of disintegration of the substance was not enough to have it completely disappear so that glyphosate residues were observed even in the control group. The average consumption of glyphosate in the groups CONLC and CONHC was 0.8 mg/d for both, whereas in the GLLC and GLHC groups was 73.8 and 84.5 mg/d, respectively.

The results indicated that BCS, body weight, net energy intake (NE) and NE balance were all affected by the proportion of concentrate in each ration, but glyphosate did not influence the parameters of either one. With regards to milk production, there were no changes in milk yield and composition in GL groups compared to CON groups.

The absence of glyphosate on dairy components could be related to the absence of its residues in milk, demonstrating that milk is not a major excretion pathway for this substance. Conversely, and not surprisingly, different energy concentration in the diet significantly influenced milk protein concentrations and yield, fat content, lactose, urea, somatic cell count and fat:protein ratio.

Overall, energy metabolism was not adversely affected by dietary treatments, since NEFA, BHB and blood glucose concentrations were all within normal reference values. The overall health of the cows was assessed by two veterinarians using a modified clinical score performed in five areas (cardiovascular, respiratory, gastrointestinal, locomotive, and udders). The clinical examination showed no adverse effect of glyphosate on cows’ health condition.

Hematological parameters

In the second experiment, blood serum was used for white and red blood cell counts. The following were recorded: subpopulations of T cells, oxidative burst capability of leukocytes, rate of apoptosis, phagocytic activity, superoxide dismutase and glutathione peroxidase activities, total non-enzymatic antioxidant capacity, viability and stimulation of peripheral blood mononuclear cells and micronucleus and comet test (to detect DNA damage).

The average daily consumption of glyphosate in the groups CON, GLLC and GLHC was 1.2, 112.6 and 132.8 μg/kg/day, respectively. The results showed that glyphosate residues in feed did not affect either the composition of the leukocyte population, including T-cell phenotypes, or the characteristics of cow erythrocytes. No significant influence of glyphosate on oxidative stress or neutrophil apoptosis was detected.

Unlike glyphosate, the concentrate levels of diets exerted marked effects on various parameters of red and white blood cell counts. The comet test did not reveal genotoxic effects and that of micronucleus also did not suggest any adverse effects of glyphosate.

Conclusions

  1. In the first experiment consumption of glyphosate (79.1 mg/d) did not affect the production and composition of milk or the metabolism and health of dairy cows.
  2. No glyphosate was detected in milk.
  3. In the second experiment an average daily exposure of cows to glyphosate of 122.7 g/kg did not induce adverse effects on the functional parameters of blood cells, redox status and genotoxic parameters.
  4. In both studies the proportion of concentrate and the time affected most parameters.

According to these results, the adverse effects of glyphosate on dairy cows can be dismissed with respect to the parameters considered in this study, and the conditions of this experiment.

References

  • Schnabel, K., Schmitz, R., von Soosten, D., Frahm J., Kersten, S., Meyer, U., Breves, G., Hackenberg, R., Spitzke, M., Dänicke, S. 2017. Effects of glyphosate residues and different concentrate feed proportions on performance, energy metabolism and health characteristics in lactating dairy cows, Archives of Animal Nutrition, 71:6, 413-427.
  • Schnabel, K., Schmitz, R., Frahm J., Meyer, U., Breves, G., Dänicke, S. 2020. Functionality and DNA-damage properties of blood cells in lactating cows exposed to glyphosate contaminated feed at different feed energy levels, Archives of Animal Nutrition, 74:2, 87-106.

© 2020 Dairy Knowledge Center. All Rights Reserved.

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Sorghum field

Storing high moisture sorghum reduces tannins and mold contents

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Alvaro Garcia

Sorghum for grain is a popular crop in parts of the world where water availability can hamper adequate corn yields. In addition to better coping with dry conditions, sorghum is also more resistant to the attack of insects, and molds. The reason for this is the presence of tannins in some sorghum varieties.

Tannins are phenolic compounds present in the protein matrix of the endosperm that protect the starch from degradation by enzymes. What is advantageous to the grain, however, is detrimental for cattle performance since it reduces the digestible energy available. Physical methods of processing such as rolling and fine grinding disrupt this protein matrix and help reduce this resistance to starch degradation.

What problems will we have if we store high moisture sorghum?

Another approach is to ensile the crop as high moisture sorghum. Aside from reducing the need for storage of large amounts of dry grain, it also helps increase its degradability. Fungi spores present everywhere in farms (air, soil, farm equipment, etc.) are opportunistic organisms that will attack the grain when it is weakened, stressed or damaged. Similarly, they will also affect during transportation, storage, and feed-out when not using best management practices. One concern then when storing high moisture grains is the development of these molds and their mycotoxins.

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A cute Holstein calf resting on the straw

Dietary calcium propionate improves performance of calves

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Alvaro Garcia

Propionic acid has been used successfully as mold inhibitor in fermented feeds such as silages and high moisture corn. Calcium propionate, the salt of propionic acid, has similar antifungal properties offering the same efficacy as the acid form once ionized in water. Because of its convenience, calcium propionate has been the product of choice when ensiling forages.

The ruminant pre-stomachs, particularly rumen and reticulum, are quite unique and work in a symbiotic relationship between the microorganisms in its fluid, and the ruminant itself. This allows the host to digest fibrous carbohydrates for which it has not developed specific digestive enzymes.

The young calf, however, has not fully developed this capacity and behaves almost like a single-stomached animal, relying mostly in milk and highly digestible concentrates to grow. Dairy farmers have used different approaches to accelerate the transition to a functioning rumen so that growing ruminants can use less expensive forages in their diets. This of course must be done without negatively affecting development and performance.

Effects of calcium propionate on the digestive system of calves

Feed fermentation in the rumen supplies volatile fatty acids (VFA) which are excretion products from rumen bacteria. These VFA are essential to the development of rumen papillae (ultimately responsible for their absorption) but are also precursors of energy to the host once absorbed. Both propionate and butyrate have been demonstrated to stimulate papillae growth, with the latter also showing an effect in intestinal development and growth.

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A charcoal drawing of four Holstein cows

Changes in cow’s competition strategies can predict metritis

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Alvaro Garcia

Two of the main stressors for cows are regrouping and their competition for resources such as bunk space. Cow competition for feeding space at the bunk during the transition period is associated with pre-established hierarchies within the herd. Older and more experienced cows usually exert dominance over their younger herd-mates.

Some authors contend that increased feeding synchrony is associated with reduced competitiveness and cow well-being, particularly in submissive cows. Dominance is also related to the cow’s body mass and health status since part of it is associated to the intensity with which they can shove around their competition. These agonistic interactions are a source of stress that could result in either developing health problems or even worsen the ones that could already be present.

The question is then how cows ponder their need for nutrients vs. the risk of engaging in competitive agonistic behavior. Are cows feeling strong enough to compete at peak feeding time, or do they wait until there is less competition and thus reduce the risk of agonistic interactions?

Could cow’s behavioural changes help us to predict diseases?

Eating what has been left by dominant cows can result worsen health problems for submissive cows if the first group happens to sort feed. Another question is if these strategies depend on the health status of the cow and if they are consistent over time. Furthermore, could these behavioral changes help detect what kind of ailment is currently affecting submissive cows?

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Vaginoscopy in a dairy cow

Capítulo 8: Exploración del útero en la vaca no gestante enferma. Ficha 2: Patología inflamatoria del útero: Etiopatogenia y factores de riesgo

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Vaginoscopy in a dairy cow

El 80-90% de los úteros presentan una elevada contaminación en los días siguientes al parto (hasta los 10-14 días del postparto en la mayoría de las vacas), siendo los microorganismos más comunes: E. coli, Streptococcus, A. pyogenes, B. licheniformis, Prevotella spp, y F. necrophorum.

La relajación de las barreras físicas que normalmente impiden la entrada de microorganismos al útero (principalmente el cérvix) y la existencia dentro del útero de un medio de cultivo idóneo para su crecimiento (sangre, restos de tejidos necrosados, etc..) son los responsables de que esto ocurra.

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A canola yellow field. Landscape

Grazing rape provides high quality forage

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Alvaro Garcia

Livestock production under grazing conditions requires practical knowledge of animal behavior as well as plant growth cycles. Depending on the region of the world, the forage base may not available year-round, and requires management techniques that allow to save it for times of shortages. This has oftentimes consisted of either feeding conserved forages or stockpiling perennial forage that can later be grazed.

Orchardgrass and tall fescue are typical perennial cool season forage species popular in pasture-based operations. They are however not plentiful year-round and need to be supplemented with other plant species. One such companion has been perennial ryegrass which however has some issues of its own, such as a fast decline in nutritive value with maturity. Annual ryegrass however is sensitive to grazing pressure particularly when not grazed at an adequate point in its development, and in regions where climate is relatively adverse.

Rape forage as an alternative to traditional forages

One alternative that has been explored in the US is the use of forage brassicas. Brassicas are cool-season annuals that can help fill the gap with quality forage throughout the grazing season. Once established they grow rapidly, tolerate better the spring-summer warmer temperatures, and maintain a relatively greater proportion of highly nutritious leaves that helps later in the year. Their more widespread adoption has not been widespread because of limited research to understand their management under grazing conditions.

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Sesame flowers

Nutritional value of sesame silage as a livestock feed

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Alvaro Garcia

Sesame silage could be a good alternative to other forages in semi-arid regions. In several parts of the world the dry season severely restricts the availability of forage for livestock. This is particularly true in tropical regions where not only is the herbage mass available the constraint but also its nutrient digestibility. Under these conditions, farmers need to rely on forages harvested and preserved during the rainy season, with hay and silages being the most frequent approaches to conservation.

The quality of the preserved forage is generally never higher than the original fresh material. These losses in nutritive value can arise from inadequate fermentation, heating/oxidation of nutrients, effluent, and growth of undesirable microorganisms. Corn silage has been a staple in the diet for dairy cows across the years since it supplies highly digestible nutrients when preserved right.

The problem with corn, however, is that its success as a crop highly depends on water availability, particularly during critical stages of its development. Other crops that are used in these regions are millet (Pennisetum glaucum) and sunflower (Helianthus annuus L.). Another plant species with potential for silage production in semi-arid regions is sesame (Sesamum indicum L.).

Sesame characteristics as a forage plant

Sesame is a flowering plant with numerous wild relatives occurring in Africa. It is one of the oldest oilseed crops known, domesticated well over 3000 years ago. Its extensive root system allows this crop to be quite tolerant to drought-conditions, growing where other crops fail. It does require however adequate moisture during germination and early growth.

Sesame varieties have adapted to many soil types. The high-yielding crops thrive best on well-drained, fertile soils of medium texture and neutral pH, it does have however less tolerance for saline soils and water-logging conditions. Sesame crops require 90 to 120 frost free days and warm conditions above 23 °C favor its growth and yield.

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Flower of vetch (Vicia sativa L.)

Alternative forage legumes: common vetch is a good one

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Alvaro Garcia

Which alternative forage legumes can be grown if alfalfa production is not acceptable? Forage legumes are important feed components of dairy cow diets. When harvested timely, they add critical nutrients such as protein, energy, and minerals, which help balance the ration while reducing the need for expensive supplements. Since the early days of modern livestock production, when it comes to supplying quality nutrients, alfalfa (Medicago sativa L.) has been labeled the “queen of forages”.

There are however some limitations to its production depending on the region and soil pH. In north-central Mexico for example small grain cereals such as oats, barley, wheat and triticale are used as alternative crops to alfalfa during the fall-winter cycle. One of their disadvantages are their lower crude protein content at harvest time, together with their lower digestibility.

There are other legumes however that can compete fairly with alfalfa and produce not only quality forage but provide an alternative to use in different environments. One such forage is the common vetch (Vicia sativa L.) which not only supplies valuable nutrients such as protein and more digestible fiber, but also helps improve soil structure and fertility. This plant is useful not only for dairy cow feeding but also in other livestock production systems such as beef cattle as well as small ruminants. There is a need however to better understand its management under different regions and conditions.

Advantages of feeding vetch as an alternative forage legume to dairy cows

Vetch has traditionally been used for grazing and hay production with the advantage of tolerating lower temperatures (-10 °C) before going dormant. It also has the same nitrogen-fixating properties when compared to alfalfa which makes it an excellent forage alternative and even a companion crop to cereals in relatively poor soils.

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Typical North American farm. Landscape

Soybean silage as an alternative forage for dairy cows

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Alvaro Garcia

What are the advantages of including soybean silage as an alternative forage in the diet of dairy cows? Soybean plants are well-adapted to dry conditions, have high grain productivity per area, with high protein content, and low fiber to protein ratio. They may be harvested for forage when their yields have shrunk below the economic threshold for oilseed harvest.

As a result, they can help stretch out conventional forages when yields may be compromised. Additional advantages described are increased carbon sequestration, nitrogen fixation, and reduced greenhouse gas emissions during rumen fermentation.

To ferment adequately in the silo, their moisture content is very important, and needs to be like that of alfalfa silage. For soybeans, this ideal moisture occurs right before the pods are full. Waiting until complete maturity results in a drier, lower digestible forage that can lead to fermentation problems due to the high oil content of the seeds.

Nutrients in soybean silage

The nutrient composition of this silage can be expected to range from 16.0 – 20.6% crude protein (CP), 38.3 – 48.3% neutral detergent fiber (NDF), 27.3 – 37.3% acid detergent fiber, 6.0 – 7.4% lignin, 1.36 – 1.49% Calcium, and 0.26 – 0.31% phosphorus. Direct-cut soybeans have a dry matter (DM) contents between 22 and 30% and ensiling at this moisture will result in higher effluent losses and a greater risk of undesirable butyric fermentation.

It is thus better to aim for 35 – 40% DM. Buffering capacity of the forage is relatively high and can result in poor fermentation. Inoculants may help reduce these problems and reduce mold growth. Always verify herbicide restrictions for feeding when attempting to use soybeans for forage.

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Several cows eating hay in a dairy farm

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

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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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Milk collection for a Bengal rose test

Association between teat-end hyperkeratosis and mastitis

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Lucas Pantaleon

What is the relationship between hyperkeratosis and mastitis in dairy cows? Teat-end hyperkeratosis (THK) is a highly prevalent teat pathology affecting dairy cows. It is characterized by a hyperplasia of the keratin layer of the teat orifice as a response to chronic stimuli. Using a severity score from 1 (less severe) to 4 (most severe), studies have found a prevalence between 21% and 46% for grade 3 and between 12% and 19% for grade 4.

Anatomical and physiological mechanisms at the teat orifice play a fundamental role in protecting the mammary gland from pathogens. The stratified squamous cell epithelium acts as a physical barrier, fatty acids have bacteriostatic effects and the muscular layer keeps the teat orifice closed in between milking.

Is hyperkeratosis a risk factor for clinical mastitis?

Different factors at the cow level such as teat shape and position, stage of lactation, parity, … have been associated with the development of THK. Factors at the herd level such as milking management and equipment settings, have also been linked to THK.

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Green cereal field

Economic evaluation of double cropping winter annuals and corn

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Alvaro Garcia

Maintaining acceptable profitability in an environmentally sustainable way are aims of most successful dairy farms. Economies of scale dictate that most farms add cows while either maintaining a similar land base or renting additional area. In order to accomplish this, it is imperative to maximize forage production from their current land base without increasing the environmental footprint.

Double cropping has been suggested as an alternative agricultural practice that reduces the environmental impact and increases forage yield per hectare. Small grain winter annuals, such as rye (Secale cereal L.), triticale (× Triticosecale), wheat (Triticum aestivum L.), and barley (Hordeum vulgare L.) can be double cropped with corn silage.

Increasing DM yields, and improving economic and environmental effects of the farm

Small grain winter annual cover crops are terminated before they reach maturity, double-cropped annuals on the other hand, are harvested as grain or preserved as silage. By doing this a double cropping system can increase the demands for nutrient cycling within the farm and reduce the inputs imported into the system. Double cropping can thus increase the profitability of the dairy enterprise by increasing yearly DM yields and improving the economic and environmental effects.

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Citología obtenida de una vaca con endometritis subclínica, en la que pueden verse numerosas células inflamatorias (polimorfonucleares neutrófilos)

Capítulo 8: Exploración del útero en la vaca no gestante enferma. Ficha 1: Patología inflamatoria del útero: Introducción

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Citología obtenida de una vaca con endometritis subclínica, en la que pueden verse numerosas células inflamatorias (polimorfonucleares neutrófilos)

Las principales alteraciones del útero en la vaca no gestante son las patologías inflamatorias. Estas patologías pueden ser más o menos graves, desde aquellas que producen sintomatología general y afectan a toda la pared uterina, hasta las que solo producen síntomas locales, o incluso pueden cursas de forma subclínica, y que solo afectan a la capa interna del útero (endometrio). Sin embargo, en todos los casos, la reproducción y la producción de nuestra explotación se verá negativamente afectada, ocasionando importantes pérdidas económicas si su incidencia no se mantiene en un nivel adecuado.

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Swiss Brown cow, portrait

Betaine allows dairy cows to better cope with heat stress

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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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Feather

Feather meal increases protein and energy in dairy cow diets

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Alvaro Garcia

Feedstuffs that contribute protein and energy for ruminants are costly all over the world. As a result, feeding usually constitutes the greatest individual cost constituting more than 50% of the cost of production in confined lactating dairy cows. Including byproducts form various industries into the diets is usually an economic alternative to reduce these costs. It also allows for reutilization of “waste” products, increasing the efficiency of production of human food. One example is hydrolyzed feather meal produced by cooking feathers under pressure.

Once dried, their protein content at close to 85%, rivals that of blood meal. It also supplies bypass protein and is rich in sulfur amino acids, usually limiting in dairy cow diets. In addition, hydrolyzed feather meal is rich in crude fat varying from 6 to 14% of the dry matter (DM), which increases its dietary energy content. As if these intrinsic properties were not enough, this basic technology can easily be applied in small family farms by simply using an old pressure cooker.

Advantages of feeding feather meal to dairy cows

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Two Holstein heifers portrait

High water sulfates affect intake and growth in heifers

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Alvaro Garcia

High quality drinking water is indispensable for livestock to express their genetic potential for production. Its availability determines critical bodily functions besides hydration, including promotion of dry matter intake, maintaining osmotic balance, excretion of waste products, and cooling the organism during hot weather among other. Water however can also be a carrier of other elements that are not required and can be even toxic to the animal.

There have been countless research experiments that explored nutrient excesses, deficiencies, and toxicities that can be triggered by inadequate water quality. One typical case has been water with an excess of sulfur which can lead to polioencephalomalacia in calves, diarrhea, impaired growth and reproduction, and other non-specific health issues. Most of these issues usually occur when cattle are offered well water or drink from ponds in areas that are rich in sulfur.

Feeding too much sulfur can interfere with the absorption of copper and selenium

About 0.15% of body weight of cattle is sulfur. It is found in methionine, cysteine, cystine, homocysteine, and taurine; in chondroitin sulfate of cartilage; and in the B-vitamins thiamin and biotin. Methionine, thiamin, and biotin cannot be synthesized in cattle tissues, so they must be supplied in the diet or synthesized by ruminal microbes. The sulfur content of most feed sources reflects the sulfur amino acid content of the proteins in the feed.

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Cute Holstein calf hidden in the grass

Lessening heat stress pre- and post-calving improves dairy calf performance

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Alvaro Garcia

Thermostasis is the process by which animals attempt to keep body temperature constant despite changes in environmental temperatures. Heat stress occurs when cows are incapable of dissipating enough heat to maintain their core body temperature. This increase in body temperature results from the combination of heat from the environment and heat increment produced internally during rumen fermentation and nutrient metabolism. In addition, heat stress increases respiratory frequency (panting) to enhance heat dissipation.

Heat increment is greater at higher feed intakes and milk production, which is why high-producing cows are more sensitive to heat stress than their lower-producing counterparts. While there has been extensive research analyzing these effects in mature cows, comparatively little has been done addressing the potential negative consequences on future productivity, health, and reproduction, of their offspring.

Long-term consequences of suffering heat stress in utero and immediately after birth

Aside for shade, pre-weaned calves are not usually considered a priority when heat abatement strategies are implemented in the farm. The main reasons are that they have a larger surface/mass ratio, and not highly significant heat increment, smaller heat loads, when compared to mature cows. However, heat stress in heifer calves both in utero as well as immediately after birth, can have long-term consequences on their future productivity in the herd.

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Hay balls

Is forage necessary in pre-weaned calves?

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Fernando Diaz

This article was published previously in the Portal de Especialistas en Novillas de Zoetis.

There has been plenty of research during the past decade testing the effects of roughage on the diet of pre-weaned heifers. The results obtained have not been consistent however; while some trials show an increase in total intake of solid feed and average daily gain (ADG), others have reported slower animal growth or simply no effect at all.

The inclusion of roughage in young heifer feeding programs, either free choice or blended with concentrates, reduces the overall energy density of the diet, since the energy concentration of the forage fraction is lower compared to the concentrates. If this approach is going to be considered, there are several factors to consider.

Presentation form of the starter feed determines the need for forage

One of the most important factors is the physical form of the starter ration. In general, pre-weaned heifers show greater dry matter (DM) intake and growth when the forage is included in the feed as meal or pellets. There are no positive results, however when the forage fraction is included in a texturized complete feed a blend of particles, flaked or whole grains.

This is due to starch degradability in the rumen, both the meal and the granular form, since ground cereal grains are fermented rapidly in the rumen and can lead to lower pH and eventually acidosis, similar to adult dairy cows. In this instance, forage intake can increase ruminal pH , since the heifers secrete saliva when chewing the forage (during intake and rumination), which has a buffering effect on the rumen contents. In texturized rations however, starch degradability is slower and rumen pH remains higher, making the supply of forage unnecessary.

Supplying forage in combination with texturized feeds can also be counterproductive. In a recent study published in “Applied Animal Science”, the authors (Hill et al. 2019) reported that lower quality grass hay (5.8% protein and 62.5% fiber) fed to 7 week-old Holstein heifers reduced the digestibility of the DM, organic matter (OM) and protein in 12.2, 11.9 y 11.1%, respectively. Although hay intake did not affect starter intake, the researchers reported a negative linear correlation between hay intake and the digestibility of the OM such that for each 100 g of hay decreased the OM digestibility by 3.7 percentage units.

Amount and type of forage also matter

Other factors to consider are the amount and type of forage included in the diet. When the forage is processed and mixed with the starter, it is advisable for the forage not to exceed 5% of the blend; higher concentrations can reduce DM intake because of rumen fill.

With regards to the type, hay is preferred over fermented forages (silages), and within the former, grass hay is the ideal one, since its palatability in young animals is higher than that of alfalfa hay and cereal grain straws.

About the author

Fernando Diaz is the Dairy Knowledge Center’s Director. Dr. Diaz works as an independent Dairy Nutrition and Management Consultant. He provides consultation to dairies and feed companies including nutrition and feeding management, forage and crop plans, and research and product development of new feedstuffs, additives and technologies for dairy cows. Fernando lives in Brookings, South Dakota and can be reached at fernando@dairykc.com.

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