Microwave heating of infant formula: a dilemma resolved.

Microwave heating of infant formula is a common practice despite concerns of infant scalding. Beyond the issue of physical safety, little is known about the effects on nutrient content of microwave heating of infant formula. Casein-predominant infant formula in 120- and 240-mL glass and plastic nursing bottles of varying colors were heated for 40 seconds and 60 seconds, respectively. Temperature profiling was monitored during the heating cycle. Analysis of riboflavin and vitamin C was made prior to and after heating. Topmost portions reached a mean temperature of 44.7 +/- 1.7 degrees C and 43.0 +/- 2.4 degrees C for all types of 240-mL and 120-mL bottles, respectively. Topmost temperatures were significantly hotter than temperatures reached at other sites. Routine mixing resulted in formula temperatures which could safely be fed to infants (35.4 +/- 0.3 degrees C and 33.9 +/- 0.2 degrees C for 240-mL and 120-mL bottles, respectively). There was no significant loss of either riboflavin or vitamin C. Protocols for microwave heating are given.

Purification of a growth factor from pigeon milk.

Aqueous extracts of pigeon milk (PM) stimulated the in vitro growth of quiescent CHO cells maintained in culture and caused precocial incisor eruption and eyelid opening in newborn mice. CM-cellulose chromatography of the growth factor of PM enhanced its biologic activity. Rechromatography of CM-active fractions in DEAE-cellulose columns yielded a single peak that was mitogenic both in vivo and in vitro. SDS-PAGE of DEAE-active fractions gave rise to a single band of molecular weight about 6000. This protein, termed as pigeon milk-derived growth factor (PMGF), yielded a single peak on gel filtration in Sephadex G-100 columns. Elution pattern of PMGF was similar to that obtained for epidermal growth factor of mouse submaxillary gland (mEGF). The chromatographic plus electrophoretic pattern, and biologic action of PMGF suggest it to be a EGF-like protein.

Hydrophobic interaction of lysozyme and alpha-lactalbumin from equine milk whey.

From fluorescence measurements on mixtures of bis-ANS and equine lysozyme and from Ca(2+)-dependent hydrophobic interaction chromatography of equine lysozyme, it is demonstrated that Ca2+ binding induces a conformational change upon which hydrophobic regions in the protein become less accessible. Bis-ANS fluorescence titrations in the absence of Ca2+ and in 2 mM Ca2+ are also performed with equine alpha-lactalbumin variants B and C. These variants differ by an amino-acid exchange Asp----Ile at residue 95. The fluorescence titration curves indicate that the accessibility of the probe to the Ca2+ conformers is clearly influenced by the mutation. The Ca(2+)-dependent exclusion of a hydrophobic domain is used in a new and simplified method for preparing lysozyme and alpha-lactalbumins simultaneously from equine milk whey.

Gas chromatographic analysis of volatile sulfur compounds from heated milk using static headspace sampling.

An investigation was conducted to test the feasibility of using gas chromatography with static headspace sampling as an objective tool to measure milk flavor quality. Heated milk off-flavor was chosen for study. Different strategies were tried for increasing the sensitivity of a commercially available headspace method, including salting out with sodium sulfate, cryofocusing during injection, and applying backpressure to the sampling loop. With the aid of a sulfur-specific detector, the resulting system was sufficiently sensitive to detect the sulfur volatiles, H2S and dimethyl sulfide, at the concentrations found in pasteurized skim milk. Milk that was heated to varying degrees was analyzed, and the analytical results were compared with the intensity of heated flavor as determined by a sensory panel. For skim milk, correlations were moderately strong: Spearman's correlation coefficients for H2S and dimethyl sulfide were .75 and .60, respectively. Correlations were weak for whole milk.

Influence of bovine somatotropin on the composition and manufacturing properties of milk.

Three studies (84, 140, and 200 d) were performed to examine the effect of injecting dairy cows with various doses (0, 320, 640, or 960 mg/28 d; 0 or 640 mg/28 d; 0, 320 mg/14 d, or 320 or 640 mg/28 d) of bST on milk production, composition, and manufacturing properties. Mean bST response among studies on milk production varied from 0 (trial 1) to 7.3% (trial 2) and from 8.5 to 14.2% (trial 3) in relation to feeding conditions. Neither milk fat nor protein percentages in milk at time of maximum response were affected by the use of bST. Distribution of casein and protein in the whey was not affected by the treatments at any time. The nature of fatty acids varied more with time after injection than with bST doses. Neither coagulation time, standard curd firmness, nor soft or pressed cheese yields were affected by the treatments.

Polyamines in human and rat milk and in infant formulas.

Polyamines are ubiquitous compounds known to be involved in cell proliferation and differentiation in many tissues. Enteral administration of these compounds has been shown to produce effects in suckling and adult animals. Using HPLC techniques, we verified the presence of putrescine, spermidine, and spermine in human milk and quantitated their concentration in samples collected from the first week up to 4 mo of lactation. Mean values of these compounds ranged (per liter) from 0 to 615 nmol putrescine, from 73 to 3512 nmol spermidine, and from 722 to 4458 nmol spermine. Polyamine concentrations in infant formulas were dependent on the protein source, the particular polyamine, and the protein concentration of the formula. Concentrations of these three compounds in rat milk over the first 3 wk of lactation were higher than in human milk, with spermidine being the polyamine most elevated compared with human milk (almost 20-fold higher). An artificial formula used for the rearing of suckling rats contained trace to immeasurable amounts of polyamines. Our study identifies milk as one vehicle for polyamine delivery to the intestinal mucosa of suckling animals.

Effect of total and rumen undegradable protein on the performance of cows fed low fiber diets.

Twelve multiparous and 18 primiparous Holstein cows were fed a 17.3% CP, 21.0% ADF diet during wk 2 through 6 postpartum. Cows then were assigned from wk 7 through 14 to one of three low fiber (10.7% ADF) dietary treatments containing either 14.4 or 18.7% CP, the latter with or without a soybean meal enhanced with rumen undegradable protein. Treatments had no effect on milk yield or composition in multiparous cows, although milk fat percentage was not depressed in multiparous cows receiving the low fiber diets. The soybean meal diet enhanced with rumen undegradable protein increased yields of milk, 4% FCM, fat, protein, and DMI compared with the 14.4% CP diet in primiparous cows; it also increased yields of 4% FCM and fat versus the 18.7% CP, untreated diet in primiparous cows. Blood urea N concentrations were greater for high CP diets than for the low CP diet in both parity groups. Rumen acetate: propionate ratios were higher for both high CP diets than for the low CP diet in multiparous cows. Soybean meal enhanced with rumen undegradable protein improved yields of milk and its components in primiparous cows fed low fiber diets, even when high protein diets were fed.

Influence of dietary protein and supplemental niacin on lactational performance of cows fed normal and low fiber diets.

Forty-seven cows (24 primiparous) were assigned to one of four normal (20.5%) ADF diets for wk 2 to 5 postpartum. Dietary treatments in a 2 x 2 factorial design were diets of 13.8 versus 18.8% CP and 0 versus 12 g/d of niacin per cow. During wk 6 to 13 postpartum, cows were fed low (11.8%) ADF diets while maintaining CP and niacin treatments. Low CP diets contained solvent-extracted soybean meal; rumen soybean meal with enhanced undegradable protein was used in high CP diets. High CP diets increased milk protein percentage in multiparous cows and yields of milk, 4% FCM, fat, protein, and SNF in primiparous cows during the normal fiber period. High dietary CP also increased yields of 4% FCM, fat, protein, and SNF in primiparous cows fed normal fiber diets. When switched to low fiber diets, primiparous cows fed high CP diets decreased more in 4% FCM and fat yields than those fed low CP. Primiparous cows fed niacin decreased more in 4% FCM than controls. High dietary CP increased DMI in primiparous cows fed normal fiber diets, but those fed low CP diets increased more in DMI when switched to low fiber diets. Supplemental niacin appeared to interact with dietary CP in multiparous cows, increasing blood glucose and decreasing blood beta-hydroxybutyrate and NEFA concentrations with the high CP, normal fiber diet. Increased dietary CP improved yields of milk and milk components in primiparous cows.

Factors affecting skim milk progesterone assay results.

Five studies were performed to determine factors affecting progesterone concentration in skim milk. Results of the first study indicated that progesterone concentration was higher in skim milk of samples kept 16 hours in an ice bath (0 C) than of those left at room temperature (21 C). In the second study, this temperature effect was found to be reversible, with skim milk progesterone concentration increasing when whole milk samples were cooled prior to centrifugation. In the third study, [3H]-labeled progesterone was used to determine the relationship between fat content of foremilk (the first milk obtained from the teats), midmilk (milk obtained midway through milking), and strippings (milk obtained immediately after milking machines have been removed) samples and temperature (4 C and 21 C) on the percentage of progesterone in the skim milk fraction. The relationship between percentage of butterfat and percentage of progesterone in skim milk was linear when the log of these variables was used for calculations. In the fourth study, assayable progesterone in the skim milk fraction of foremilk, midmilk, and strippings was affected by temperature. In the fifth study, a multiple-regression procedure was used to determine the amount of variation in percentage of radioactive progesterone in the skim milk fraction. Independent variables (whole milk butterfat and temperature of incubation [1, 3, 13, 22, 37, and 50 C]) and the natural log of each variable, were entered into a stepwise multiple-regression analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Milk and water intakes of foals sucking grazing mares.

Intakes of milk and milk nutrients were determined for 8 foals at 11-18 days of age and for 10 foals at 30-44 days and 60-74 days of age while sucking grazing mares. Water intakes (sources other than milk) of the foals were determined at 30-44 days and 60-74 days of age. Five of the 10 mares were fed a protein supplement (24% crude protein) in addition to grazing during the stud season. The protein supplement did not influence foal intakes of milk and milk nutrients, milk composition, weight gains of the mares or the growth rate of the foals. Foal milk intakes increased (P less than 0.05) from 16.9 kg/day at 11-18 days to 18.1 kg/day at 60-74 days of age. The water intakes of the foals increased (P less than 0.01) from 3.9 kg/day at 30-44 days to 5.5 kg/day at 60-74 days of age. Total fluid intakes per kg foal liveweight were 246, 202 and 172 g at 11-18, 30-44 and 60-74 days of age, respectively. For each kg of weight gain, foals consumed 12.8, 15.7 and 16.4 kg milk at 11-18, 30-44 and 60-74 days of age. Stage of lactation had a significant effect on the total solids, lactose and protein content of milk. The fat and gross energy content of milk remained constant.

Effect of a prolonged-release formulation of N-methionyl bovine somatotropin (sometribove) on milk fat.

Nine Holstein cows were injected bi-weekly with a prolonged-release formulation of N-methionyl bST, and 9 cows were injected with excipient. Intramuscular injections began at 60 +/- 3 d postpartum and continued at 14-d intervals for the full lactation. Administration of bST increased production of milk, total fat, and all milk fat components measured. Average fatty acid composition of milk fat was not influenced by bST treatment. Stage of lactation had a large influence on production and percentage of individual fatty acids in milk fat from both bST-treated and control cows. The stage of lactation impact on the fatty acid composition of milk fat reflected changes in the relative contributions of body fat mobilization and de novo synthesis of milk fat components in response to changes in energy balance. Initiation of bST treatment caused some transient changes in milk fatty acid composition that were related to energy balance. These changes were small compared with the normal changes because of stage of lactation in all cows. Phospholipid and cholesterol content of milk also changed with stage of lactation but were not influenced by bST treatment. Melting properties of milk fat were influenced greatly by stage of lactation. Bovine somatotropin did not cause any changes in composition or physical properties of milk fat that were outside the range of normal variation.

Effect of a prolonged-release formation of N-methionyl bovine somatotropin (sometribove) on milk composition.

Forty Holstein cows received bi-weekly injections of prolonged-release formulation of bST, and 39 received bi-weekly injections of excipient, in a study to evaluate the effects of long-term bST administration on milk composition and component production. Injections began at 60 +/- 3 d postpartum. Administration of bST increased production of milk and of all measured components. Concentrations of lactose (4.85 and 4.81%), fat (3.76 and 3.67%), total solids (12.57 and 12.44%), SNF (8.83 and 8.75%), casein (2.56 and 2.53%), and true protein (3.13 and 3.08%) were similar in milks from cows receiving bST and excipient, respectively. Percentages of NPN (times 6.38) and total protein were greater in milk from bST-treated cows (.179% NPN and 3.32% total protein) compared with milk from cows injected with excipient (.172% NPN and 3.24% total protein). Use of bST did not change the relative percentages of alpha s-casein, beta-casein, kappa-casein, beta-lactoglobulin, alpha-lactalbumin, or casein proteolysis products. A cyclical pattern of milk production, component production, and composition within each 14-d injection interval was observed. This suggests that a diminishing amount of bST was delivered during the latter third of each injection interval. There were no effects of bST on milk composition that would be of any practical significance to dairy product manufacturers or consumers.

Nonspecific antibacterial factors in milk from cows immunized with human oral bacterial pathogens.

Both the immunoglobulins and non-specific antibacterial factors in milk from cows immunized with pathogenic oral bacteria have the potential to influence the oral microflora during passive immunization studies. The first six milks after calving were collected from 2 cows immunized with adjuvant and from 14 cows immunized with adjuvant and heat-killed strains of periodontopathic Actinomyces, Porphyromonas, Prevotella, and Fusobacterium. Analysis of the products from the first to the sixth milks revealed that the protein and lysozyme content decreased approximately 66 and 72%, respectively; the mean specific activity of the enzyme remained relatively constant. In contrast, the mean lactoperoxidase activity increased 2.3-fold in the second milking and increased further in the fourth and sixth milkings. The mean iron-binding activity increased 1.2-fold from the first to the second milkings and then decreased 3.6-fold through the sixth milking. Cows immunized with adjuvant alone showed similar responses. Per unit volume, the milk contained approximately 150 times less lysozyme than whole human saliva obtained from six subjects but higher concentrations of lactoperoxidase and iron-binding components. Purified bovine nonspecific factors prevented the growth of the bacteria used for immunization when bacteria were tested at concentrations similar to those found in saliva and milk. Because bovine nonspecific antibacterial factors could influence both the pathogenic target bacteria and the indigenous microflora in oral passive immunization studies with bovine immunoglobulins, the presence of these proteins should be considered.

Prediction of mastitis using milk somatic cell count, N-acetyl-beta-D-glucosaminidase, and lactose.

The objectives of this work were 1) to examine the responsiveness of SCC, lactose concentration, and NAGase activity in milk to changes in bacteriological status and 2) to develop models for predicting bacteriological status of mammary glands. Data included 550 cows in 10 commercial herds. Natural logarithm NAGase and log cell count were most responsive to changes in bacterial status. The log NAGase was relatively more effective in identifying major from minor pathogen infections, whereas log SCC was better able to differentiate between infected and uninfected classes. Non-transformed NAGase, SCC, and lactose were considerably less responsive to infection status. Logistic regression of bacterial status on herd, lactation number, milk, log SCC, log NAGase, and stage of lactation was performed. The least significant variables were removed in a stepwise process. Final predictors of infection status were herd, log SCC, and log NAGase. The role of log SCC was to discriminate infection from no infection, whereas log NAGase discriminated major from minor pathogens. The log NAGase, alone or in combination with log SCC, added substantially to the detection power of the model. Chi-square goodness of fit tests found no significant differences between observed and predicted infection probabilities. Substitution of herd averages for log SCC and log NAGase for the herd variables resulted in significant differences between predicted and observed herd infection probabilities.