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. For five of the six cows, body temperature showed a circadian rhythm peaking at 2323 hr with an amplitude of 0.34 degree C. For the sixth cow, body temperature was 180 degrees out-of-phase, peaking at 1230 hr with an amplitude of 0.12 degree C. Circadian rhythms for insulin and urea were consistent for all six cows peaking at 1743 hr with an amplitude of 0.74 ng/ml for insulin and at 1034 hr with an amplitude of 3.83 mM for urea. Body temperature and insulin also displayed episodic increases that often exceeded the amplitudes of circadian rhythms. For body temperature, a broad increase in spectral power was seen for periods between 100 and 175 min; time intervals between peaks averaged around 100 min. For insulin, power spectra for individual cows universally indicated rhythms with periods of approximately 45 and 80 min; time intervals between peaks averaged approximately 65 min. For urea, almost all spectral energy was confined to the 24-hr rhythm, although there was evidence of a low-amplitude, 60-min rhythm. In conclusion, when animals are acclimated to a rigidly controlled environment and frequent blood sampling is accomplished with minimal intervention, it is possible to detect rhythms inherent in the regulation of metabolic variables.

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. 3.5 g/dl), had a higher proportion of lipid as triglyceride (97.3% vs. 96.7%), and had a lower proportion of lipid as phospholipid (0.8% vs. 1.0%). Milk from the group fed cottonseed contained fewer medium-chain fatty acids (24.4% vs. 29.4%) and more C18 fatty acids (35.9% vs. 25.8%) than did milk from the control group. Total blood lipids were 234 mg/dl for Holsteins and 168 mg/dl for Jerseys. Total blood lipids were higher for dry cows fed cottonseed (100 vs. 72 mg/dl), particularly Jersey cows. As determined by gravimetric or TLC analysis, milk fat percentages of cows fed cottonseed were not different from those of cows fed control rations. However, as determined by infrared instrumentation, milk fat appeared to be lower (4.3%) for cows fed cottonseed than that (4.6%) for control cows. Changes in milk fatty acids that were related to diets might explain the difference between infrared and gravimetric determinations of milk fat.

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. Peripheral concentrations of growth hormone for all six cows exhibited sinusoidal circadian rhythms with average minima of 4.1 ng/ml at 1820 hr and maxima of 5.3 ng/ml at 0630 hr. Estimated periods of ultradian rhythms for individual cows by spectral analysis, peak identification, and fitting cosine functions using least squares were 71 to 83 min for all cows. No direct relationship between ultradian peaks and milking or feeding was apparent. In conclusion, a circadian rhythm and an ultradian rhythm with a period around 80 min are probably intrinsic to mechanisms regulating peripheral growth hormone concentrations in the lactating dairy cow.

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. Mean percentage of milk fat was 5.7%, for Jerseys with Danish sires and 4.8% for Jerseys with US sires. Total fat per day was the same (.91 kg) for both groups. Detailed analysis of milk lipids indicated that lipid composition of milk was similar for cows with US sires and those with Danish sires. However, milk from Jerseys with Danish sires contained more free cholesterol than milk from Jerseys with US sires, 17.5 versus 14.3 +/- .6 mg/dl. The proportion of polyunsaturated fatty acids was greater for milk from Jerseys with US sires than for milk from Jerseys with Danish sires (2.3 vs. 2.1%). Although lipid composition of milk from both groups was generally similar, the milk of Jersey cows with Danish sires had higher concentrations of free cholesterol and lower proportions of polyunsaturated fatty acids, both of which are possible negative factors for health of consumers.

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. For two cows, a nadir of 15 ng/ml occurred around 1900 and a zenith of 29 ng/ml around 0730. For four cows, circadian rhythms were 180 degrees out of phase, with a nadir of 28 ng/ml around 0840 and a zenith of 40 mg/ml around 1920. Ultradian peaks, which varied in amplitude within and among animals, showed no consistent relationship with either milking or feeding. Spectral analyses indicated rhythms around 100 min for the first two animals and 150 min for the four animals. In conclusion, there were no simple relations between prolactin rhythms and lights on or lights off. Further, results suggest that changes in the phase of circadian rhythms may be associated with changes in the periods of ultradian 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. The cows were housed in an environmental chamber at 19.0 +/- 0.5 degrees C (lights on between 0700 and 2300 h), fed daily at 0900 h, and milked at 0800 and 2000 h. Mean concentrations of plasma triiodothyronine and thyroxine exhibited similar circadian rhythms with minima (0500-1300 h) and maxima (1700-0200 h) separated by 12 h. Triiodothyronine peaked 2 h before thyroxine. The thyroxine circadian rhythm preceded a circadian body temperature rhythm by 2 h. Superimposed on the circadian rhythm was an ultradian rhythm with a 90-min period that was 15-20% of the mean thyroid hormone concentrations. Peak thyroxine and triiodothyronine concentrations were 50 +/- 2 and 1.58 +/- 0.17 ng/ml, and minimal concentrations were 42 +/- 2 and 0.94 +/- 0.17 ng/ml, respectively. Our data indicate that peripheral triiodothyronine is regulated independently of peripheral thyroxine concentration.

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. Milk was collected for assessment of SCC and bacteriological status on d 0 and approximately every 3 d until d 18. Quantity of keratin recovered before milking on d 10 did not differ between teats milked with or without pulsation, but loss of keratin because of milking was greater from teats milked with pulsation. By d 7, 30% (12 of 43) of quarters milked without pulsation had become infected, but no (0 of 47) quarters milked with pulsation were infected. By d 14 to 16, new infections had increased to 68% (28 of 41) of quarters milked without pulsation and 2% (1 of 43) in quarters milked with pulsation; mean SCC in pulsationless quarters increased sevenfold relative to pulsation quarters. Protein and water content of keratin did not differ because of treatment, and changes in lipid composition were minor. Histological analysis of the teats of 4 cows indicated that the mean diameter of the teat canal, within 2 h after milking, was greater without pulsation than with pulsation (680 vs. 483 microns).

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 3.1 ng/ml at 1800 h, maxima were 4.5 ng/ml at 0530 h--and strong ultradian rhythms with periods around 120 min. Peak to trough amplitudes of ultradian rhythms, 1 to 17 ng/ml, varied among and within cows over time. No direct relation between ultradian peaks and milking or feeding was apparent. Spectral analysis indicated that most power (variation) was centered around 1 cycle every 2 h, i.e., around a period of 120 min. This very strong, easily observable, ultradian rhythm indicates that an oscillation with a period around 120 min is probably intrinsic to mechanisms regulating peripheral glucocorticoid concentrations.

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. Wisconsin mastitis test score and somatic cell count in all quarters increased significantly (P < 0.01) by the next milking. Effects were greatest in the endotoxin-exposed quarters. Milk yields for all quarters decreased significantly (P < 0.01) by the first milking after endotoxin injection. Udder and body temperatures at milkings were similar and were not affected by treatment. When temperatures were averaged for the 5 cows for each of 120 time points/d, average temperatures, relative to time of injection of endotoxin, were increased by 0.5 C above baseline at 2.75 hours, peaked at +2.9 C at 6.50 hours, and remained high through 9.25 hours after injection. Power spectra calculated for individual cows on a daily basis universally indicated an increase in power at low frequencies on the day of injection. Subsequently, Streptococcus agalactiae (200 colony-forming units) was injected into right rear teat cisterns. Wisconsin mastitis test score increased at the second milking after injection. Cell count and quarter milk yield decreased by the third milking. As with endotoxin, injection of S agalactiae could not be detected via a change in temperature at milkings.(ABSTRACT TRUNCATED AT 250 WORDS)

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. It is important to realize that these observations were made either on single women or on very small groups of women. In infant diseases, such as breast milk jaundice and ectopic eczema, changes in polyunsaturated fatty acids in maternal milk have been described.

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 0.7-2.4, very low levels of 10:0 and 12:0 were present in serum lipids as compared to much higher concentrations of these fatty acids in colostrum lipids (colostrum/serum ratio 16.23 and 17.11 for 10:0 and 12:0, respectively). We have previously found that medium-chain fatty acid levels are very low in prepartum mammary secretions (6-10 wk before term delivery) but are higher and similar in colostrum of women who deliver preterm (3-14 wk) or at full term. The data indicate that parturition, irrespective of length of pregnancy, is the trigger for medium-chain fatty acid synthesis in the human mammary gland.

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). Bacterial challenge was repeated after the next four milkings. Foremilk samples were obtained for 8 d after keratin removal to determine infection status. A mammary quarter was classified as infected based solely upon the bacteriological criteria outlined by the National Mastitis Council. The rate of infection in quarters from which keratin was removed was greater than that in control quarters. Infection rates were 26.3% for keratin-removed quarters and 8.3% for control quarters in trial 1 and 13.5 and 0%, respectively, in trial 2. When more stringent criteria (recovery of greater than 100 cfu of S. agalactiae/ml in three or more successive milk samples and a SCC of greater than 10(6)) were used to identify a subset of infections that were clearly intramammary, infection rates were 9.3% for keratin-removed quarters and 1.4% for control quarters. Thus, partial removal of keratin from the teat canal compromised the ability of the teat to prevent passage of bacterial pathogens from the external environment into the mammary gland.

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 (8.36-21.37%) than in serum (1.59-9.6%) throughout lactation. The high milk-serum ratio of medium chain fatty acids (up to 28.4, 30.2, and 6.2 for 10:0, 12:0, and 14:0, respectively) indicates synthesis in the mammary gland. Long-chain polyunsaturated fatty acids (C20:1-C22:6) of the n - 3 and n - 6 series were higher in serum (6.76-12.53%) than in milk (1.57-4.42%). With the exception of colostrum, the fatty acid composition of milk and serum changed little during lactation and was similar in two consecutive lactations in the same woman. Comparison of milk and serum fatty acids provides a noninvasive approach for the assessment of the synthetic activity of the human mammary gland.

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. In Experiment 2, 10 multiparous cows with clinical mastitis in one or more quarters were selected. Milk samples from inflamed quarters were cultured to identify mastitis pathogens; these quarters were classified as clinical; all other quarters were classified as control. Teat canal keratin was collected from all quarters just before an a.m. milking, samples were weighed, and lipid determinations were conducted by TLC. Keratin from subclinical quarters compared with keratin from control quarters did not differ in either neutral lipid or fatty acid composition. Total lipid was significantly higher in keratin from teats of clinical quarters than in keratin from control quarters (27.8 vs. 21.5 microgram/mg). Neutral lipid composition of keratin was similar between teats from clinical quarters and teats from control quarters. In Experiment 2, quarter foremilk samples were also obtained to determine lipid composition. The FFA in milk from clinical quarters contained fewer short-chain fatty acids, whereas polyunsaturated fatty acids were significantly higher in milk from clinical quarters.

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, 2.1 g/dl, and in milk from the dry group, 2.2 g/dl. Neutral lipids decreased to 1.3 and .9 g/dl in quarters from dry cows at -40 and -10 d prepartum. In secretions from dry quarters, triglycerides were 97% of total lipids at -60 d and decreased to 85 and 91% at -40 and -10 d, respectively. Conversely, FFA and monoglycerides increased during the dry period. Lipids associated with fat globule membrane components increased during the dry period. These increases were 10 times for cholesterol, 20 times for cholesteryl esters, and twice for phospholipids. In general, the content of fat globule core lipids (triglycerides) exhibited a pattern opposite that of membrane lipids (cholesterol, cholesteryl esters, phospholipids) during the prepartum period. Proportions of core lipids tended to decrease, whereas proportions of membrane lipids increased in prepartum mammary secretions. Lipid composition of prepartum secretions may be influenced by blood lipids, somatic cells, and alterations in mammary lipid synthesis.

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). The fat residue in the feeding sets was quantitated by gravimetry, and individual fatty acids were characterized by gas-liquid chromatography. The data show that only trace amounts of lipid (0.23 +/- 0.04%) adhered to feeding sets during feeding of unfortified formula. Significantly more lipid (p less than 0.0005) adhered when formula was fortified with MCT oil, and the method of feeding greatly affected lipid adherence, i.e., 1.52 +/- 0.21% when the MCT oil was followed by formula versus 10.20 +/- 1.76% when the MCT oil was mixed with formula before feeding. Analysis of the fat residue of fortified formula showed that greater than 90% was composed of C8:0 and C10:0, the major fatty acid components of MCT oil. We suggest that care be exercised when fortifying infant formula with MCT oil.

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. Nulliparous and postpartum nonlactating rats did not differ in serum thyroxine, triiodothyronine concentrations, or in 5'-deiodinase activity in liver and kidney. As litter size increased, maternal serum thyroxine, triiodothyronine concentrations, and 5'-deiodinase activity in liver and kidney decreased. Growth rate of pups was inversely correlated with litter size and positively correlated with concentration of serum thyroxine and liver 5'-deiodinase in mothers. In pups, serum triiodothyronine concentrations decreased as litter size increased, but serum thyroxine concentrations were not affected. Results suggest a relationship between the hypothyroid status of lactating rats and suckling intensity. The thyroid status of the dam may influence thyroid status and growth of offspring.

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. All three experiments yielded similar results. In Holsteins, keratin weight before milking was 1.6 times greater than keratin weight after milking (3.1 vs. 1.9 mg). In Jerseys, only small amounts of keratin were removed during milking (3.5 mg before vs. 3.1 mg after) In Holsteins and Jerseys, neutral lipid concentration was 1.6 times greater after milking than before, suggesting that when keratin was removed during milking, only moderate amounts of lipid were removed. In Holsteins, total lipid collected per teat was similar before or after milking (59.2 vs. 48.5 micrograms). Results demonstrate that keratin collected after milking had a different lipid composition than keratin collected before 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. Following initial collection, the quantity of keratin removed was regenerated within 1 to 2.5 d. The rate of keratin regeneration per teat was approximately 1.5 mg of wet weight or .6 mg of dry weight per 24 h. The concentration (microgram lipid/mg keratin, wet weight) of lipid in keratin samples collected during regeneration was almost twice that present initially or after regeneration was complete. With the exception of free cholesterol, composition (%) of lipid components of keratin did not differ between samples collected initially, those collected early in the process of regeneration, and those collected after the mass of keratin removed had been replaced. Although data suggest that keratin matures during the process of regeneration, maturation appears complete by the time mass of keratin is fully regenerated. Additionally, the quantity of keratin recovered at initial sampling was inversely correlated with milk production. We hypothesize that as milk production increases, more keratin is lost during milking.

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. Concentrations of the fatty acids synthesized within the mammary gland, C10:0 to C16:0, increased about 50% from 7 to 42 d of lactation. During this period, compensatory decreases were observed in C18:1. The phospholipids were separated into five major classes: sphingomyelin, phosphatidyl choline, serine, inositol, and ethanolamine for fatty acid analysis. The changes that occurred in milk total fatty acids were reflected in phosphatidyl phospholipid fatty acid composition: an increase in medium-chain fatty acids and a decrease in polyunsaturated fatty acids of 18, 20, and 22 carbon atom chain length as lactation progressed. These changes are consistent with the theory that milk phospholipids are synthesized de novo entirely in the mammary gland.