Circadian and ultradian rhythms of body temperature and peripheral concentrations of insulin and nitrogen in lactating dairy cows.

To investigate possible circadian and ultradian periodicities for peripheral insulin and urea in lactating dairy cows, integrated 15-min blood samples were taken sequentially over 48 hr from six cows. In addition, radiotelemetry measurements of body temperature were averaged over the same 15-min periods. Cows were housed in an environmental chamber at 19 degrees C with lights on 0700 to 2300 hr; fed daily at 0900 hr; and milked at 0800 and 2000 hr.

Comparison of milk and blood lipids in Jersey and Holstein cows fed total mixed rations with or without whole cottonseed.

Lipids in milk and blood were examined in Holstein and Jersey cows (8 lactating and 4 dry) fed two TMR containing either 10% whole cottonseed or a control concentrate mixture of corn, cottonseed hulls, and cottonseed meal in a switchback experiment. Milk from Jersey cows contained more total lipid than did milk from Holstein cows (4.4 vs.

Circadian and ultradian rhythms of peripheral growth hormone concentrations in lactating dairy cows.

To investigate possible circadian and ultradian periodicities for plasma growth hormone in lactating dairy cows, integrated 15-min blood samples taken sequentially over 48 hr from six cows were analyzed by radioimmunoassay. The cows were housed in an environmental chamber at 19 +/- 0.5 degree C, 50% relative humidity, and 16 hr of light and 8 hr of darkness (lights on at 0700 hr); fed daily at 0900 hr; and milked at 0800 and 2000 hr.

Comparison of lipid composition of milk from half-Danish Jersey cows and United States Jersey cows.

We studied differences in lipid composition of milk from Jersey cows with US sires and from Jersey cows with Danish sires. Milk samples were obtained on DHIA test day from 32 cows with Danish sires and 32 herdmates with US sires in two herds. The Jerseys with US sires were paired with those with Danish sires by parity and stage of lactation.

Circadian and ultradian rhythms of peripheral prolactin concentrations in lactating dairy cows.

To investigate possible circadian and ultradian periodicities for peripheral prolactin in lactating dairy cows, integrated 15-min blood samples taken sequentially over 48 h from six cows were analyzed by radioimmunoassay. Cows were housed in an environmental chamber at 19 degrees C with lights on 0700 to 2300, fed daily at 0900, and milked at 0800 and 2000. Peripheral concentrations exhibited sinusoidal circadian rhythms.

Circadian and ultradian rhythms of plasma thyroid hormone concentrations in lactating dairy cows.

Circadian and ultradian rhythms of thyroxine and triiodothyronine were analyzed by radioimmunoassay on integrated 15-min blood samples collected for 48 h from six lactating dairy cows. Body temperatures were recorded every 1.4 min using radiotelemetry.

Influence of pulsationless milking on teat canal keratin and mastitis.

Twenty-four Holstein cows, producing at least 21 kg of milk/d, were used in two replicate experiments to determine the effect of presence or absence of pulsation on loss of teat canal keratin during machine milking. Left quarters were milked without pulsation and right quarters were milked with pulsation. On d 0 and 10, keratin was collected from one left and from one right teat canal of each cow prior to milking and from the remaining two teat canals after milking.

Circadian and ultradian rhythms of peripheral cortisol concentrations in lactating dairy cows.

To investigate possible circadian and ultradian periodicities for plasma cortisol in lactating dairy cows, integrated 15-min blood samples taken sequentially over 48 h from six cows were analyzed by radioimmunoassay. The cows were housed in an environmental chamber at about 19 degrees C, 50% relative humidity, and 16 h of light and 8 h of darkness (lights on at 0700 h); fed daily at 0900 h; and milked at 0830 and 2000 h. Peripheral concentrations of cortisol for all six cows exhibited weak circadian rhythms--average minima were 3.

Radiotelemetry temperature responses of mammary gland and body to intramammary injection of Escherichia coli endotoxin or Streptococcus agalactiae in lactating dairy cows.

To investigate the feasibility of using changes in body or mammary temperature to detect mastitis, radiotransmitters were implanted midway between rear udder quarters and in the peritoneal cavity of 5 Holstein cows (1 to 3 months in lactation) housed in an environmental chamber (16 +/- 2 C; lights on 7:00 AM to 11:00 PM). After a 6-week control period, Escherichia coli endotoxin (0.5 mg) was injected after the morning milking into left rear teat cisterns via the teat canal.

Human mammary gland function at the onset of lactation: medium-chain fatty acid synthesis.

The onset of medium-chain fatty acid synthesis in the human mammary gland was investigated. Colostrum and serum were collected from 31 healthy women and the fatty acid composition of total lipid was analyzed by gas-liquid chromatography. Although colostrum/serum ratios for most fatty acids range from 0.

Human milk in disease: lipid composition.

Differences in the lipid composition of human milk have been described in maternal diseases known to affect fat metabolism. Diseases such as diabetes, cystic fibrosis, hypobetalipoproteinemia and Type I hyperlipoproteinemia affect the quantity and quality of human milk fat. Increased fatty acid chain elongation and changes in desaturation (especially delta 6 desaturase), as well as changes in lipid class composition, have been shown in diabetes and cystic fibrosis, whereas compensatory increases in medium-chain fatty acids have been described in hypobetalipoproteinemia and Type I hyperlipoproteinemia.

Increased susceptibility to intramammary infection following removal of teat canal keratin.

Influence of teat canal keratin on susceptibility to intramammary infection was investigated in lactating Jersey cows. In each of two replicate trials, keratin was removed from the left teats of 20 cows immediately before milking. Immediately after milking, all teats were exposed to bacterial challenge by immersion in a suspension of Streptococcus agalactiae (5 x 10(7) cfu/ml).

Milk and blood fatty acid composition during two lactations in the same woman.

Fatty acid composition of colostrum, milk, and serum was studied during two consecutive lactations in the same woman. There were marked differences between milk and serum: medium chain fatty acids (C6:0-C14:0) were higher in milk (8.36-21.

Effect of clinical and subclinical mastitis on lipid composition of teat canal keratin.

Two experiments were conducted to investigate lipid composition of teat canal keratin when different conditions of bacterial colonization and quarter inflammation were present. In Experiment 1, 11 multiparous cows with subclinical mastitis (bacteria present but no visible inflammation) in at least one quarter were selected for study. Quarters that were sampled and found negative for bacterial growth were classified as control.

Changes in the lipid composition of the secretions of the bovine mammary gland during the dry period.

To study initiation of milk fat synthesis, lipid composition of mammary secretions at -60, -40, and -10 d prepartum was studied in lactating and nonlactating Holstein cows. Eleven cows were dried off, and 13 cows were milked twice per day throughout the normal dry period. Total neutral lipid was similar in late lactation milk (-60 d) from lactating cows, 2.

Adherence of medium-chain fatty acids to feeding tubes of premature infants fed formula fortified with medium-chain triglyceride.

Adherence of medium-chain triglyceride (MCT) oil to feeding tubes during gavage feeding of Enfamil formula was quantitated. Infants were fed similar volumes of either unfortified formula (n = 11) or MCT oil-fortified formula (0.5 ml/oz); either the MCT oil was mixed with the formula before feeding (n = 11) or the MCT oil was delivered into the feeding tube and then was followed by formula (n = 11).

Effect of lactational intensity on extrathyroidal 5'-deiodinase activity in rats.

Concentrations of thyroxine and triiodothyronine in serum and 5'-monodeiodination activity in liver and kidney were studied in lactating Sprague-Dawley rats with different litter sizes. Litter sizes were adjusted at birth to 0 (postpartum nonlactating group), 4, 8, 12, and 16 pups per lactating rat. Serum and tissue samples were collected from lactating rats and pups on d 12 of lactation and from 6 nulliparous females.

Lipid composition of teat canal keratin collected before and after milking from Holstein and Jersey cows.

In three experiments, keratin was collected from individual teats of 40 Holstein and 20 Jersey cows immediately before and after milking. In Experiments 1 and 2, keratin collected from teats of 20 Holstein cows before milking was compared with keratin collected after milking. In Experiment 3, keratin was collected from two teats of 20 Jersey and 20 Holstein cows before milking and compared to the other two teats of the same cows after milking.

Regeneration of teat canal keratin in lactating dairy cows.

This study was designed to determine the regeneration rate of teat canal keratin in two groups of 10 lactating Holstein cows. The weight of keratin obtained upon successive collections of keratin was determined. Intervals between successive collections were varied between 8 and 72 h.

Changes in milk fat phospholipids during lactation.

Changes in lipid composition were studied in milk obtained on postpartum d 3 (colostrum), 7, 42, and 180 from 12 Holstein cows. Triglycerides, 96 to 97% of total lipids, were relatively constant during lactation. Phospholipids and cholesterol declined with advancing lactation.

Evidence that bovine growth hormone treatment increases the rate of extrathyroidal 5'-monodeiodinase activity in cattle.

This study examined the influence of bovine growth hormone (bGH) on liver and kidney thyroxine-5'-monodeiodinase activity (TMA) in growing beef cattle. In a preliminary trial (trial 1), tissue samples were obtained at slaughter from two placebo-injected and two bGH-injected (29.2 IU/day for 14 days before slaughter) Hereford heifers (398 kg avg slaughter wt), with one heifer on each treatment fed at either 1.

Rhythms in cholesterol, cholesteryl esters, free fatty acids, and triglycerides in blood of lactating dairy cows.

Blood samples from six lactating dairy cows were analyzed to determine whether circulating neutral lipids exhibit rhythmic variations. Plasma neutral lipids were measured by quantitative TLC on every fourth integrated 15-min blood sample taken over 48-h periods. Cows were housed in an environmental chamber at 20 degrees C with 16 h light:8 h dark (lights on at 0700 h), fed daily at 0900 h, and milked at 0830 and 2000 h.

Methods of collection and lipid composition of teat canal keratin in dry and lactating cows.

Methods for collecting keratin from the teat canal were examined to select a procedure to obtain representative samples for lipid analysis. Data obtained by solvent extraction of excised teats were compared with those obtained by scraping keratin from dissected teats of lactating and dry cows. Solvent extraction with petroleum ether or 2:1 chloroform-methanol yielded similar dry weights of material.

Milk composition and volume during the onset of lactation in a diabetic mother.

Milk volume and composition were examined in a diabetic mother on days 3-7 postpartum. By day 5 milk volume produced and concentrations of sodium, potassium, chloride, lactose, protein, calcium, magnesium, and citrate were within limits of a reference population. Fat content of the milk was slightly lower.

Effect of bovine growth hormone on incorporation of [14C]acetate into lipids by co-cultures of bovine mammary, liver, and adipose tissue explants.

Incorporation of [14C]acetate into lipids was measured in 24 hr co-cultures of mammary, liver and adipose tissue from Holstein cows at 53, 210 and 318 d of lactation in the presence or absence of bovine growth hormone. Little (less than 1%) of the labeled lipids appeared in the media relative to that incorporated into the tissue. In mammary tissue, incorporation of [14C]acetate was highest into triglycerides (16,298 cpm/mg mammary tissue), followed by phospholipids (1,887 cpm), free fatty acids (1,252 cpm), diglycerides (708 cpm), free cholesterol (360 cpm) and monoglycerides (93 cpm).