Effect of selenium supplementation on dairy cattle.

The adequacy of current supplemental dietary selenium allowances for dairy cattle has been reviewed from the literature and by monitoring responses of dairy herds in a veterinary practice specializing in nutritional consultation. Both information sources tend to agree that a reference range of 70 to 100 ng of Se/mL of serum is an acceptable target concentration. This range can be attained most often by providing > 6 mg of supplemental Se.animal-1.d-1, but several factors affect the serum Se responses of different cows to specific Se intakes. These factors may include forage types and sources, ruminal environment, supplemental fat, dietary calcium, trace metals, and genetics. The major benefits, observed experimentally, of maintaining optimal Se intakes include minimizing the incidence of mastitis and preventing calf losses associated with myopathy and(or) respiratory disease.

Inositol as a lipotropic agent in dairy cattle diets.

Fatty liver syndrome or hepatic lipidosis (HL) is a condition thought to contribute to an increased incidence of peripartum disease, reduced response to therapy and decreased fertility in dairy cows. This syndrome is characterized by excess triglyceride (TG) accumulation in the liver and apparent decreased hepatic lipoprotein output. In lactating rats, a similar condition results from feeding an inositol-deficient diet. It is also characterized by excess hepatic TG accumulation and decreased hepatic lipoprotein output. Myo-inositol is a necessary component of the phospholipid phosphatidyl-inositol, which is an important membrane constituent. Myo-inositol occurs in feed mainly as the inositol hexaphosphate phytic acid. Phytic acid is undigestible by the monogastric but rumen phytases are assumed to adequately hydrolyze it. In early lactation dairy cows, lipid mobilization is intense, and the myo-inositol requirement may exceed the dietary supply or availability. Myo-inositol is being tested in a field trial as a potential lipotropic agent for dairy cows. Preliminary results suggest no lipotropic benefit from added myo-inositol.

Inositol and hepatic lipidosis. II. Effect of inositol supplementation and time from parturition on serum insulin, thyroxine and triiodothyronine and their relationship to serum and liver lipids in dairy cows.

Percutaneous liver biopsies and blood samples were obtained from 80 dairy cows in nine Michigan herds over the peripartum period. Thirty-nine cows were fed 17 g of supplemental inositol and 41 were fed a placebo. Liver biopsies were assayed for total myoinositol and triglyceride (TG) concentrations. Blood samples were assayed for serum dextran precipitable cholesterol, nonesterified fatty acids (NEFA), insulin, thyroxine (T4), free (FT4), triiodothyronine (T3) and free T3 (FT3) concentrations. Serum concentrations of insulin and the thyroid hormones decreased near parturition, with lowest concentrations occurring in the immediate postpartum period. Concentrations of T3 correlated well with T4, and the concentrations of free thyroid hormones reflected concentrations of total thyroid hormones. The percentage of hormone in the free fraction remained constant over time. Serum insulin, T3 and T4 were negatively correlated with serum NEFA and liver TG concentrations. Thyroid hormone concentrations were positively correlated with serum dextran precipitable cholesterol concentrations. Inositol supplementation was associated with reduced circulating T3 and FT3 concentrations, but not T4 and FT4 concentrations. Changes in hormone concentrations at parturition and their relationship to liver TG and serum NEFA concentrations were consistent with a metabolic adaptation by the dairy cow to the negative energy balance of early lactation.

Inositol and hepatic lipidosis. I. Effect of inositol supplementation and time from parturition on liver and serum lipids in dairy cattle.

Percutaneous liver biopsies and blood samples were obtained from 80 multiparous dairy cows in nine Michigan herds. Biopsies and samples were obtained serially over the peripartum period. Thirty-nine cows received 17 g of supplemental myoinositol in the diet to test its use as a possible lipotropic substance and 41 received a placebo. Liver biopsies were assayed for triglyceride (TG) and total myoinositol content. Serum was assayed for dextran precipitable cholesterol and non-esterified fatty acids (NEFA). Inositol supplementation had no effect on any of the lipid variables. There was a significant herd effect on liver inositol, serum dextran precipitable cholesterol and NEFA concentrations. Serum NEFA and liver TG concentrations increased in the immediate postpartum period, while dextran precipitable cholesterol decreased. A significant herd X period interaction existed for liver TG and serum dextran precipitable cholesterol concentrations. Liver TG and serum NEFA concentrations were positively correlated. Excessive infiltration of bovine liver with lipid at calving appears to be an exaggerated manifestation of normal metabolic changes.

Reduction of serum triacylglycerol-rich lipoprotein concentrations in cows with hepatic lipidosis.

The hepatic and serum lipid concentrations in 49 dairy cows with displaced abomasum, 7 postpartum cows fasted for 6 days, and 14 healthy postpartum cows were studied. The cows with displaced abomasums were retrospectively allotted to 2 groups: those with greater than 15% liver fat (DAHF) and those with less than 15% liver fat (DALF). Liver total lipid concentrations were high in the DAHF group, exceeding these values in the fasted cows by 30% and in the healthy and DALF cows by 63% on the average. In contrast, the liver phospholipid concentrations were low in the DAHF group, intermediate in the fasted and DALF groups and high in the healthy group. On a group basis, an inverse relationship was observed between serum and liver lipid concentrations. The serum concentrations of both total and dextran-sulfate-precipitable (DSP) lipids were high in the fasted cows and were less in the DALF and healthy cows and in the DAHF cows (lowest). The between-group differences in serum total and serum DSP concentrations of triacylglycerol, cholesterol, and phospholipid followed the same quantitative pattern as the total lipids. However, the relative difference between groups was greater for each of the DSP lipid fractions. These results support the hypothesis that severe hepatic lipidosis in cattle occurs due to impaired hepatic lipoprotein synthesis and secretion.

Use of prostaglandin F2 alpha in the treatment of unobserved estrus in lactating dairy cattle.

A field trial was conducted to evaluate the use of prostaglandin F2 alpha (PGF2 alpha) (lutalyse)a in lactating dairy cattle with unobserved estrus in the presence of a functional corpus luteum (CL) and clinically normal reproductive tract. Seventy-three Holstein and 9 Jersey cows, weighing between 340.0 and 772.7 kg, were allotted to treatment and control groups. All treated cows were inseminated within 80 hours after treatment as assigned by this trial. Control cows were inseminated at the first observed estrus. Of the treated cows, 50% showed estrus within 80 hours after treatment. In this trial, 96% of the treated cows and 92% of the control cows were determined to have at least 1 functional CL on the day of treatment. For the treatment group and the control group, mean serum progesterone concentrations were 4.1 ng and 3.5 ng (P less than 0.2, by Student's t test), respectively, on day of treatment and were 0.4 ng and 5.0 ng (P less than 0.005, by Student' t test) on day 5 after treatment. Pregnancy rates were 57% for treated and 47% for control cows (P = 0.5, by X2). Days from treatment to first-observed estrus, treatment to first service, and treatment to conception were significantly reduced in the treatment group compared with these criteria for the control group (P less than 0.05, 0.005, and 0.01 respectively). It was concluded that induction of luteolysis with PGF2 alpha in lactating dairy cattle with unobserved estrus and a palpable functional CL will be an effective addition to reproductive health programs.

Drug residues in milk after intrauterine injection of oxytetracycline, lincomycin-spectinomycin, and povidone-iodine in cows with metritis.

A study was conducted to document the maximum retention times of antimicrobial residues in milk after their use in intrauterine treatment of metritis in lactating cows and to evaluate several risk factors hypothesized to influence the retention time of these drugs. Oxytetracycline (3 g), lincomycin-spectinomycin (2 g of one-third lincomycin and two-thirds spectinomycin), or povidone-iodine (6 g) were given to cows with metritis by intrauterine route. The Bacillus stearothermophilus var calidolactis disk assay was performed on each milk sample. Of the 61 cows treated with oxytetracycline, 30 had residues in their postinjection milk for variable periods (range, 12.5 to 44.0 hours; mean, 26.6 +/- 10.3). Of the 47 cows treated with lincomycin-spectinomycin, 17 had residues in their postinjection milk for various periods (range, 14.5 to 24 hours; mean, 19.5 +/- 8.9). Povidone-iodine was not detected in milk. Because a high number of cows (n = 61) were treated with oxytetracycline, only data from these cows were used in testing the influence of 3 factors (severity of metritis, time after parturition when cows with metritis were treated, and parity) on maximum retention of the drug in milk. Severity of metritis did not have a significant influence (P greater than or equal to 0.1) on the maximum retention time of the drug. The retention time decreased linearly with the increase of time after parturition when the cow with metritis was treated. First lactation cows had a significantly (P less than or equal to 0.01) shorter retention time than did older cows.

Acute recumbency and marginal phosphorus deficiency in dairy cattle.

Because of a mixing error at a local feed mill, a diet marginally deficient in phosphorus, compared with recommendation from the National Research Council, was fed to a high-producing dairy herd for 5 months. Two mature cows in early lactation became recumbent. Serum phosphorus concentration in 1 cow was low (1.8 mg/dl), but was not measured in the other cow. Ten other high-producing, first-lactation cows in the herd developed severe lameness. Results of analysis of rib bone samples from the recumbent cows were consistent with changes associated with demineralization. Bone ash, calcium, phosphorus, and magnesium concentrations were lower than published ranges for healthy cattle. Serum calcium, phosphorus, and magnesium concentrations in 8 unaffected cows were normal. For 6 unaffected cows, mean serum hydroxyproline concentration was higher during the period that the phosphorus-deficient diet was fed than when an adequate diet was fed. Moderate (15%) restrictions in dietary phosphorus intake, compared with National Research Council recommendations, can possibly result in health problems in high-producing dairy cattle.

Relationship of hepatic lipidosis to health and performance in dairy cattle.

In a field study of 80 cows in 9 dairy herds, serial liver biopsies were performed over the peripartum period to determine degree of hepatic lipidosis. Cattle were separated into categories of mild, moderate, and severe hepatic lipidosis on the basis of maximal amounts of hepatic triglyceride that accumulated during this period. Number of cattle with mild, moderate, and severe hepatic lipidosis were 52, 16, and 12, respectively. Cattle with severe hepatic lipidosis had greater concentrations of hepatic triglyceride before calving and after parturition, and greater serum nonesterified fatty acid concentrations and body condition loss after parturition than cattle with mild hepatic lipidosis. Rate of disease and culling and death rate because of disease were greater in cattle with severe hepatic lipidosis. Cattle with severe hepatic lipidosis had reproductive performance equal to clinically normal cattle; however, cattle with moderate hepatic lipidosis had increased days to conception, possibly related to greater milk production.

Feeding the dry cow to avoid metabolic disease.

The nonlactating period should be regarded as a preparatory phase for the next lactation, rather than a rest phase from the preceding one. During the early dry period, a diet should be provided that meets nutrient requirements for energy, protein, calcium, phosphorus, selenium, vitamins, and other minerals. This can usually be accomplished by feeding a blend of roughages with little or no grain and providing a vitamin and mineral supplement. The diet during the late dry period, or transitional stage, should provide increased energy (an additional 3 to 4 Mcal), and a PP preventive regimen can be instituted at this time. Five to six pounds of concentrate containing 200 gm of an ammonium sulfate and chloride mixture and 6 gm of niacin can be added to the diet to aid in the transition to lactation. Feeding of high-calcium, lactating-cow grain mix should be avoided until after parturition. Stress should be minimized at and after parturition, and a quiet maternity area should be available. The normal depression in dry matter intake at parturition should be minimized; feeding high-quality roughages at this time is beneficial. Concentrate consumption should be increased gradually following parturition, and careful attention to the soluble and undegradable protein fractions of the diet is warranted. In group feeding situations, introduction to the energy-dense, high-lactation ration should probably be avoided for the first 10 to 14 days postpartum, until the cow is acclimated to the forage mix. Body overconditioning should be avoided. However, attempts to manipulate body condition during the dry period tend to be unrewarding and counterproductive. Following these guidelines should reduce the incidence of metabolic diseases in high-producing dairy cattle.

Implementation of nutritional consultation within a dairy practice.

Expansion of services to include nutritional consulting for client herds is a realistic expectation of most dairy practices. In addition to a client base, a commitment to obtaining the knowledge and an expertise in dairy nutrition is necessary. Once some expertise is gained, the most important requirement becomes regarding nutritional advice as an integral part of the practice and devoting the time to provide the service. Most implementation failures result from imprecise estimates of dry matter intake or a failure to maintain an ongoing presence on the farm and monitor results.

Dry cow management for the prevention of ketosis and fatty liver in dairy cows.

Dramatic increases in energy requirements during late gestation and early lactation, superimposed on an animal with a profound drop in DMI just before calving, make the dairy cow highly susceptible to the metabolic diseases ketosis and hepatic lipidosis. Increased serum concentrations of NEFA appear to be causally linked to these problems, and feeding strategies to reduce or avoid this dramatic increase are desirable for optimal health and performance. During the last 3 to 4 weeks prepartum, a diet higher in energy and protein concentration than current NRC recommendations should be fed so that adequate nutrient intake occurs within the limits of the reduced DMI. The additional energy should be provided by glucose precursors, such as starchy concentrates or propylene glycol, and not by lipid. Excessive energy and reduced fiber should be avoided both early in the dry period (more than 28 days prepartum) and immediately postpartum. Attention should be paid to the environment of the cow, especially during the last 3 weeks prepartum, to avoid environmental stressors as much as possible.