Dairy Farming
Frequently Asked Questions
Scientific answers based on NRC 2001 and NASEM 2021 standards, prepared by Doç. Dr. Mehmet ÇOLAK
Dry matter intake (DMI) is typically 2.5-3.5% of body weight. A 600 kg cow usually consumes 18-22 kg dry matter per day. In high-yielding cows (>40 L/day), DMI may increase to 3.5-4%. During the transition period (before and after calving), DMI declines, which increases the risk of negative energy balance (NEB). NASEM 2021 discusses the main factors affecting DMI in detail, including ration NDF level, feed quality, environmental temperature, and social stress.
The transition period covers the 3 weeks before calving and 3 weeks after calving. During this time, DMI decreases while energy demand rises, leading to negative energy balance (NEB). NEB increases the risk of ketosis, fatty liver, hypocalcemia, mastitis, metritis, and reduced reproductive performance. In Turkey, transition diseases account for approximately 40-60% of economic losses in dairy herds. Proper DCAD management together with calcium and energy support can reduce these risks substantially.
DCAD (Dietary Cation-Anion Difference) describes the difference between dietary cations (Na+, K+) and anions (Cl-, S2-). Formula: DCAD = (Na + K) - (Cl + S) mEq/kg dry matter. In the dry period, applying a negative DCAD (-50 to -150 mEq/kg) helps prevent subclinical hypocalcemia. Positive DCAD, especially in rations based on high-potassium silages, increases hypocalcemia risk. Because corn silage in Turkey often contains high potassium, DCAD management is especially important. The VetKriter Dairy Cow Ration Calculator computes DCAD automatically.
BCS is evaluated on a 1-5 scale. At calving: 3.0-3.25. Peak lactation (weeks 4-8): 2.5-2.75, because some loss from NEB is expected. Late lactation: 3.0-3.5 as the cow recovers. Dry period: 3.25-3.5. If BCS is >3.75 at calving, the risk of fatty liver rises. If BCS is <2.5, energy reserves are inadequate and fertility may decline. One BCS point corresponds to about 56 kg body weight.
Ketosis develops when NEB becomes more severe during the transition period and ketone bodies accumulate because of excessive fat mobilization. Prevention strategies: 1) Control BCS during the dry period, aiming for 3.0-3.25 at calving. 2) Avoid excessive dietary energy during the dry period, especially in the last 3 weeks. 3) Provide propylene glycol after calving (300-500 mL/day for 5-10 days). 4) Supplement niacin (6-12 g/day). 5) Monitor BHBA early postpartum; >1.2 mmol/L indicates subclinical ketosis. VetKriter includes a detailed article on ketosis management.
Mastitis is the costliest disease in dairy farming, causing about 300-500 USD loss per cow per year. The 5-Point Control Program includes: 1) pre- and post-milking teat dipping, 2) dry cow therapy, either blanket or selective, 3) prompt treatment of clinical mastitis cases, 4) somatic cell count monitoring with a target of <200,000 cells/mL, and 5) culling or segregating chronic cases. Milking machine maintenance and hygiene are also essential. Cows with SCC >400,000 cells/mL are a major source of economic loss.
The traditional dry period is 60 days. However, current evidence from NASEM 2021 suggests that high-producing cows (>10,000 L/lactation) may perform well with a 40-50 day dry period, while low- to moderate-producing cows generally benefit from 45-60 days. A dry period <30 days may reduce milk yield in the next lactation. A dry period >75 days increases the risk of obesity and metabolic disease. Dry period length should therefore be adjusted to production level and body condition.
NRC (National Research Council) published the 2001 edition of Nutrient Requirements of Dairy Cattle, which served as the gold standard for many years. NASEM (National Academies of Sciences, Engineering, and Medicine) published the updated 2021 edition and effectively replaced NRC for dairy nutrition recommendations. Key updates in NASEM 2021 include revised metabolizable protein equations, improved rumen bypass protein calculations, environmental temperature adjustments, and new equations for high-producing cows. The VetKriter Dairy Cow Ration Calculator uses NASEM 2021 standards.
Energy balance = energy intake - energy expenditure. During the first 4-8 weeks of lactation, some negative energy balance (NEB) is expected as the cow mobilizes body fat. The severity of NEB can be tracked by BCS loss: a decline of 0.5-1.0 BCS points from calving to 60 days in milk is generally acceptable. Greater loss increases the risk of ketosis, fatty liver, and fertility problems. The target dietary energy density in early lactation is usually 1.55-1.65 Mcal NEL/kg dry matter.
Rumen pH should ideally remain between 6.0 and 6.8. When pH falls below 5.8, subacute ruminal acidosis (SARA) becomes likely. SARA is one of the most common metabolic problems and may lead to reduced milk fat, diarrhea, lameness, and poor appetite. Factors affecting rumen pH include high starch or sugar in the ration, insufficient NDF, abrupt dietary changes, and inadequate buffering. Prevention includes maintaining ration NDF at 28-32% of dry matter, adding sodium bicarbonate (150-200 g/day), and making gradual dietary transitions.
NDF (Neutral Detergent Fiber) is essential for rumen function and should generally be at least 28-30% of dry matter. Physically effective NDF (peNDF) also matters, so particle size must be adequate. ADF (Acid Detergent Fiber) affects digestibility and is usually best between 17-21%. High ADF lowers energy density, while low NDF raises the risk of SARA. In corn silage, NDF digestibility (NDFD) is also important, because higher NDFD improves energy intake. The VetKriter Ration Calculator checks these values automatically.
Hypocalcemia, or milk fever, is one of the most common metabolic diseases in dairy cows. Subclinical hypocalcemia (blood Ca <2.0 mmol/L) may affect about 25% of first-lactation cows and up to 50% of older multiparous cows. Management strategies include negative DCAD diets during the dry period, careful calcium restriction before calving in selected programs, oral calcium supplementation after calving (such as calcium propionate or calcium chloride), use of vitamin D metabolites such as 25-OH D3, and regular blood calcium monitoring.
According to NASEM 2021, a high-producing dairy cow usually requires 60-80 g phosphorus per day. Dietary phosphorus should generally be 0.32-0.38% of dry matter. Excess phosphorus increases fecal phosphorus excretion and environmental load, may contribute to urinary issues, and can interfere with calcium balance. Deficiency may reduce appetite, milk production, and reproductive performance. Common phosphorus sources include dicalcium phosphate, monosodium phosphate, and bone meal.
Magnesium deficiency is also known as grass tetany. Clinical signs include nervousness, muscle tremors, gait abnormalities, seizures, and sudden death. High-risk periods include spring grazing, when lush grass is high in potassium and low in magnesium, and the start of lactation. Daily magnesium requirement is usually 20-30 g/day. Prevention includes magnesium oxide supplementation (50-60 g/day during risk periods) and avoiding pastures with excessive potassium. Magnesium absorption is impaired by high potassium and ammonium intake.
NASEM 2021 describes two major protein fractions: RDP (Rumen Degradable Protein), which supports rumen microbes and generally accounts for about 60-65% of dietary protein, and RUP (Rumen Undegradable or bypass protein), which escapes rumen degradation and is absorbed in the small intestine, usually about 35-40%. A high-producing cow may require 2500-3000 g metabolizable protein (MP) per day. Lysine and methionine are the main limiting amino acids. Rumen-protected methionine can improve milk protein percentage and support liver health.
Vitamin E and selenium work together as part of the antioxidant defense system. Consequences of deficiency include white muscle disease in calves, retained placenta, increased mastitis risk, and weak immune function. Vitamin E requirement rises during the transition period, and 1000-3000 IU/day is often recommended. Organic selenium, such as selenomethionine, usually has better bioavailability than inorganic selenium sources such as sodium selenate. Because many soils in Turkey are low in selenium, supplementation is often important.
Heat stress (THI >68) reduces milk yield, fertility, and immune function and is a serious issue during summer in Turkey. Nutritional strategies include increasing dietary energy density, using high-quality bypass protein, increasing buffering capacity because SARA risk rises, and increasing potassium and sodium to replace sweat losses. Niacin supplementation (6-12 g/day) may help through vasodilation. Nutritional adjustments should always be combined with cooling systems such as fans and sprinklers.
Fat supplementation is mainly used during the first 100 days of lactation to help cover the energy deficit. Rumen-protected fats, such as calcium soaps or hydrogenated fats, are preferred because they do not disrupt rumen fermentation as much as free fats. Palmitic acid (C16:0) supports milk fat, while oleic acid (C18:1) helps increase energy density. Total supplemental fat should generally not exceed 5-6% of ration dry matter. Excess fat can depress fiber digestion, impair rumen function, and reduce feed intake.
Niacin (nicotinic acid) is a useful supplement in dairy cows. Potential benefits include reducing lipolysis and helping prevent ketosis, improving thermoregulation during heat stress through vasodilation, supporting liver function, and in some studies modestly improving milk yield. The usual dose is 6-12 g/day, with 12 g/day commonly used during the transition period. Rumen-protected niacin is generally more effective. Supplementation is especially useful during the transition period and hot weather.
Choline is critical for liver function and fat metabolism. During the transition period, it helps reduce hepatic lipidosis. Rumen-protected choline should be used, because ordinary choline is broken down by rumen microbes. A common dose is 15-25 g/day of rumen-protected choline during the transition period. Potential benefits include less liver fat accumulation, improved milk yield, better reproductive performance, and lower ketosis risk. In many herds, the cost-benefit ratio is favorable.
Corn silage is the most common forage source in Turkey. Key quality parameters include dry matter of 30-35%, pH of 3.8-4.2, lactic acid making up >65% of total fermentation acids, NDF of 40-48%, ADF of 25-30%, NDF digestibility (NDFD) >50%, and starch of 28-35%. Mycotoxin analysis is also important, especially for aflatoxin B1, which can appear in milk as AFM1. Entering silage analysis data into the VetKriter Ration Calculator helps optimize the ration.
Biotin (vitamin B7) is required for hoof horn synthesis. Research findings show that supplementing 20 mg biotin per day can reduce lameness incidence by 30-50% (Midla et al., 1998; Bergsten et al., 2003). It improves hoof hardness and structural integrity. However, the effect is gradual and usually requires 3-6 months of continuous supplementation. Given that lameness may cost 300-500 USD per cow per year, biotin supplementation is often economically justified.
The dry period can be divided into two phases. Far-off dry period (until 3 weeks before calving): low energy density, about 1.25-1.35 Mcal NEL/kg dry matter, with good-quality forage and a BCS target of 3.25-3.5. Close-up period (last 3 weeks before calving): gradually increase dietary energy density, begin DCAD management, and supplement calcium, phosphorus, magnesium, vitamin E, and selenium as needed. For overconditioned cows (BCS >3.75), controlling energy intake is especially important.
Propylene glycol is a glucogenic compound that is converted to glucose in the liver. Main indications include treatment of subclinical ketosis (BHBA 1.2-2.9 mmol/L) and prophylaxis in high-risk cows, such as overconditioned cows (BCS >3.75), cows carrying twins, or cows with retained placenta. Dose: for treatment, 300-500 mL/day for 5-10 days; for prophylaxis, 200-300 mL/day from about 2 weeks before calving until 2 weeks after calving. It may be given as an oral drench or mixed into the TMR. Doses above 500 mL may be toxic.
TMR is a feeding system in which all ration ingredients are mixed together before feeding. Advantages include less selective eating, more consistent nutrient intake with each bite, better rumen pH stability and lower SARA risk, improved dry matter intake, better labor efficiency, and less feed waste. Disadvantages include higher equipment cost and the risk that incorrect mixing time or sequence can reduce effectiveness. Particle size must be checked, ideally with a Penn State Particle Separator. TMR is increasingly common on larger farms in Turkey.
Urea is a non-protein nitrogen (NPN) source that rumen microbes use to produce ammonia and then microbial protein. It is most appropriate when the ration is short in rumen degradable protein and when enough rapidly fermentable energy is available, especially in high-starch diets. The maximum practical dose is about 150-200 g/day; higher amounts may cause ammonia toxicity. Urea should be fed together with fermentable carbohydrate sources. Slow-release urea products are generally safer. Use in dry cows should be cautious.
Sodium bicarbonate (NaHCO3) is a rumen buffer. Benefits include stabilizing rumen pH, helping prevent SARA, supporting saliva buffering capacity, and helping maintain milk fat percentage, which often falls when rumen pH remains low. It is particularly useful in high-starch, low-fiber diets. The usual dose is 150-200 g/day, or about 0.7-0.8% of ration dry matter. It often works even better when combined with magnesium oxide at a 2:1 ratio. Excessive use may raise urine pH.
These trace minerals are important for reproduction, immunity, and hoof health. Zinc supports hoof integrity, immune function, and fertility and is typically fed at 50-80 mg/kg dry matter. Copper is important for immunity, pigmentation, and enzyme activity and is usually fed at 10-15 mg/kg dry matter. Manganese supports estrus, conception, and skeletal development and is typically fed at 40-60 mg/kg dry matter. Organic sources such as proteinates and amino acid chelates often have better bioavailability than inorganic forms. High iron or sulfur in drinking water can reduce copper and zinc absorption.
Iodine is essential for thyroid hormones (T3 and T4). Signs of deficiency include goiter in cows or calves, stillbirths, weak calves, hair loss, reduced milk yield, and reproductive problems. Iodine deficiency is relatively common in inland areas of Turkey. Prevention involves iodized salt or mineral supplementation. The general requirement is about 0.5-0.8 mg/kg dry matter. Brassica plants such as cabbage or turnip and some water sources may reduce iodine availability because of goitrogenic effects.
All answers on this page are prepared based on NASEM 2021, NRC 2001 and current JDS/JAS articles.
About Us