Cattle lactation

Some of these compounds could be considered as dietary additives, but various other terms, including pesticides, can also be used. They can have beneficial effects on the environment and this aspect will be discussed later. The ionophore monensin, which is an alicyclic polyether (Figure 1), is a secondary metabolite of Streptomyces and aids the prevention of coccidiosis in poultry. Monensin is used as a growth promoter in cattle and also to decrease methane production, but it is toxic to equine animals. " Its ability to act as an ionophore is dependent on its cyclic chelating effect on metal ions. ° The hormones bovine somatotropin (BST) and porcine somatotropin (PST), both of which are polypeptides, occur naturally in lactating cattle and pigs, respectively, but can also be produced synthetically using recombinant DNA methods and administered to such animals in order to increase milk yields and lean meat production. "... 

Monensin None (not used for lactating animals) Cattle... 

The results of metabolism studies with laboratory animals and livestock indicate that endosulfan does not bioconcentrate in fatty tissues and milk. Lactating sheep administered radiolabeled endosulfan produced milk containing less than 2% of the label. Endosulfan sulfate was the major metabolite in milk (Gorbach et al. 1968). A half-life of about 4 days was reported for endosulfan metabolites in milk from survivors of a dairy herd accidentally exposed to acutely toxic concentrations of endosulfan endosulfan sulfate accounted for the bulk of the residues detected in the milk (Braun and Lobb 1976). No endosulfan residues were detected in the fatty tissue of beef cattle grazed on endosulfan-treated pastures for 31-36 days (detection limits of 10 ppm for endosulfan, 40 ppm for endosulfan diol) the animals began grazing 7 days after treatment of the pastures. Some residues were detected in the fatty tissue of one animal administered 1.1 mg/kg/day of endosulfan in the diet for 60 days. No endosulfan residues were... 

The high demand for glucose by the fetus and fot synthesis of lactose in lactation can lead to ketosis. This may be seen as mild ketosis with hypoglycemia in women, but in lactating cattle and in ewes cattying twins thete may be vety pronounced ketosis and profound hypoglycemia. 

Forsell, J.H., L.R. Shull, and J.R. Kateley. 1981. Subchronic administration of technical pentachlorophenol to lactating dairy cattle immunotoxicologic evaluation. Jour. Toxicol. Environ. Health 8 543-558. 

Whole milk contains, on average, 0.06 mg B6 per 100 g, mainly in the form of pyridoxal (80%) the balance is mainly pyridoxamine (20%), with trace amounts of pyridoxamine phosphate. Concentrations in raw ovine and pasteurized caprine milks are similar to those in cows milk (0.08 and 0.06 mg per 100 g, respectively). The concentration of B6 varies during lactation colostum contains lower levels than mature milk. Seasonal variation in the concentration of vitamin B6 has been reported in Finnish milk levels were higher (14%) when cattle were fed outdoors than when they were fed indoors. Mature human milk contains about 0.01 mg B6 per 100 g. 

Enrofloxacin is another fluoroquinolone antibacterial developed exclusively for animals (146). It is administered either by parenteral route to cattle, swine, sheep and rabbits, or by the oral route to cattle, swine, rabbits, chickens, and turkeys (147). Although it is not allowed for use in dairy cows, enrofloxacin is also used in some countries for treatment of coliform mastitis in lactating cows. In addition, enrofloxacin has received growing attention during the last years for its potential against several fish pathogens (148). 

In lactating cattle, mean residue levels of thiabendazole and 5-hydroxy-thiabendazole in milk were found to be 5007 and 168 ppb, respectively, 12 h after dosing, decreasing to 20 and 25 ppb at 84 h after dosing. In sheep, 7 days after oral administration of thiabendazole, no residues of the drug were found to be present in muscle, liver, and kidney tissues. 

In sheep given a dose of 15 mg/kg bw, a depletion pattern similar to cattle was observed, but total residues in all tissues were lower at all time points, depleting in liver from around 16 ppm 1 day after dosing to 700 and 170 ppb 4 and 20 days after dosing, respectively. In lactating cattle, total residues in milk were nearly 5 ppm 11 h after administration of a 15 mg/kg bw dose, reducing to 640 and 35 ppb after 35 and 72 h, respectively. 

When cattle were given a single intramuscular injection of 3 mg imidocarb/ kg bw, residues in kidney, liver, muscle and at the injection site were 13,600, 16,300, 1500, and 4200 ppb, respectively, at 7 days after dosing, declining to 3200, 3700, 500, and 1700 ppb, respectively, at 28 days after the last dose. In lactating cows given two injections of 3 mg imidocarb/kg bw, 28 days apart, residues in milk were in the range of 604-793 ppb 1 day after the first treatment and these declined to below 10 ppb at 7 days after treatment. 

Residue depletion studies in lactating cattle given a single intramuscular injection of 1 g betamethasone/kg bw showed that the concentrations of the parent drug in milk were in the range 3.82-38.22 nmol/L at the first milking, and lower than 1.6 ppb at the seventh milking. 

Phenylbutazone, the major suxibuzone metabolite, has been approved by the FDA for use in dogs and horses (87). It is not licensed in cattle but its properties make it useful in this species for the treatment of musculoskeletal conditions, mastitis, endotoxemia, and castration. Since there is evidence of extralabel use for treatment of mastitis in lactating cows, residues of this drug may be found in bovine milk. 

Other hormones are used for increasing the milk production and efficiency of lactating dairy cows. In the United States an estimated 63% of all cattle and about 90% of feedlot animals are implanted witli growth hormones. Beef and sheep may be also implanted but not swine. When implants are used in young... 

Diethylstilbestrol (DES) Sulfonamide drugs in lactating dairy cattle (except approved use of... 

Measurement of milk cesium-137 secreted by range beef cattle is not practical because of the limited lactation period and milk production of beef cattle and because of the added handling of the cattle that would be required. 

Knodt, C. B., Shaw, J. C. and White. G. C. 1942. Studies on ketosis in dairy cattle. II. Blood and urinary acetone bodies of dairy cattle in relation to parturition, lactation, gestation and breed. J. Dairy Sci. 25, 851-860. 

Of the seven macro mineral elements required by dairy cattle, five can be considered fertilizer elements (potassium, calcium, phosphorus, magnesium, and sulfur), but sodium and chloride are both toxic lo plants at high concentrations and present practical problems in areas with saline soils. High salt intakes have also been shown lo increase udder edema in heifers. Because of the importance of chloride in nutrition and mclabolisni. research is needed to define the chloride requirements of lactating cows and clarify mineral relationships, especially between chloride and potassium plus sodium-... 

Pirlimycin (PIR) was recently approved by the U.S. Food and Drug Administration (FDA) for the treatment of mastitis in lactating dairy cattle. Regulatory tolerances of 400 yug/L PIR in milk and 500 ig/kg in liver were established. 

WA Moats, KL Anderson, JE Rushing, DP Wesen. Comparison of a radioimmunoassay (Charm-II) test with high-performance liquid chromatography for detection of oxytetracycline residues in milk samples from lactating cattle. Amer J Vet Res 56 795-800, 1995. 

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