Effect of stocking density on ewes' milk yield, udder health and microenvironment

Three groups of 12 lactating Comisana ewes were housed in separate rooms of the same building that contained straw-bedded pens with total areas of 12, 18 and 24 m2. The ewes were assigned to groups with different stocking densities: high (HSD, 1 m2/animal), medium (MSD, 1.5 m2/animal) or low (LSD, 2 m2/animal). The LSD treatment resulted in lower air concentrations of total microorganisms and coliform bacteria than the other two. Ewes in the LSD group gave greater yields of milk, total protein and fat than those in the other two groups. LSD treatment increased milk casein content and improved clotting time and clot firmness. LSD also resulted in ewes giving milk with lower somatic cell counts and smaller concentrations of mesophiles, psychrotrophs and faecal coliforms than MSD and HSD. Subclinical mastitis occurred in three ewes of the MSD groups and four ewes of the HSD group, while no cases were recorded in the LSD group. These results indicate that stocking density is a critical factor in dairy sheep housing and suggest that a space allocation < 2 m2/animal may adversely affect the performance and health of the lactating ewe.

Effect of milk proteins on adhesion of bacteria to stainless steel surfaces

Stainless steel coupons were treated with skim milk and subsequently challenged with individual bacterial suspensions of Staphylococcus aureus, Pseudomonas fragi, Escherichia coli, Listeria monocytogenes, and Serratia marcescens. The numbers of attached bacteria were determined by direct epifluorescence microscopy and compared with the attachment levels on clean stainless steel with two different surface finishes. Skim milk was found to reduce adhesion of S. aureus, L. monocytogenes, and S. marcescens. P. fragi and E. coli attached in very small numbers to the clear surfaces, making the effect of any adsorbed protein layer difficult to assess. Individual milk proteins alpha-casein, beta-casein, kappa-casein, and alpha-lactalbumin were also found to reduce the adhesion of S. aureus and L. monocytogenes. The adhesion of bacteria to samples treated with milk dilutions up to 0.001% was investigated. X-ray photoelectron spectroscopy was used to determine the proportion of nitrogen in the adsorbed films. Attached bacterial numbers were inversely related to the relative atomic percentage of nitrogen on the surface. A comparison of two types of stainless steel surface, a 2B and a no. 8 mirror finish, indicated that the difference in these levels of surface roughness did not greatly affect bacterial attachment, and reduction in adhesion to a milk-treated surface was still observed. Cross-linking of adsorbed proteins partially reversed the inhibition of bacterial attachment, indicating that protein chain mobility and steric exclusion may be important in this phenomenon.

Endocrine and metabolic aspects in milk-fed calves

In neonatal calves besides adaptations in organ function there are marked metabolic and endocrine changes. The growth hormone (GH)-insulin-like growth factor (IGF) axis is basically functioning, but needs maturation. Various metabolic and endocrine traits do not exhibit marked ontogenetic changes after the first week of life, but others remain different from the adult stage. Thus, plasma oxytocin or an oxytocin-like substance and nitrate concentrations are elevated for months. The ability to digest colostrum (C) and milk involves great alterations in structure and function of the gastrointestinal (GI) tract. C intake is important for passive immunity, provision of nutrients, minerals and vitamins, and contains biologically active substances. IGF-I, present in C in high amounts, appears to enhance GI tract development and function. For sufficient absorption not only of immunoglobulins, but also of fatty acids and fat-soluble vitamins, C should be ingested immediately after birth. The amino acid pattern and the glutamine/glutamate ratio depends greatly on whether C is fed or not. Effects on insulin, IGF-I, and IGF binding proteins depend on time-point and amounts of C fed. After the colostral period calves are almost exclusively fed milk and milk substitutes or weaned. Low iron intake, required for the production of pale meat, besides anemia causes metabolic and endocrine adaptations, such as enhanced insulin-dependent glucose utilization and appears to reduce IGF-I responses to GH. Metabolic and endocrine changes, such as insulin resistance and disturbed glucose metabolism, can be observed in part in association with high feeding intensity in veal calves.

CRF-deficient mice respond like wild-type mice to hypophagic stimuli

Corticotropin-releasing factor (CRF) has been implicated in physiological processes associated with stress, including changes in feeding behavior. Intracerebroventricular (ICV) administration of CRF and urocortin have been shown to depress feeding, and antagonism of CRF receptors has been reported to attenuate hypophagic responses to many treatments, suggesting that brain CRF may mediate these responses. We have now studied feeding behavior of mice lacking the CRF gene (CRFko), comparing them to wild-type (CRFwt) mice. Feeding was assessed in nondeprived mice by measuring the intake of sweetened milk in a 30-min period and the food pellet intake over 24 h. ICV administration of CRF or urocortin (1 microg, but not lower doses) depressed milk and food pellet intake in normal mice. Physical restraint for 30 min, or administration of mouse interleukin-1beta (mIL-1beta, 100 ng, IP), lipopolysaccharide (LPS, 1 microg, IP), or the serotonergic agonist (d-fenfluramine, 4 mg/kg, IP) reliably reduced milk intake. LPS also reduced food pellet intake. The responses to restraint, IL-1, LPS, and fenfluramine were indistinguishable between the CRFwt and CRFko mice. These results suggest that CRF is not essential for the reduction in sweetened milk intake that occurs following restraint, LPS, IL-1, or d-fenfluramine administration to mice.

Effects of secretion removal on bovine mammary gland function following an extended milk stasis

The objective of this study was to determine whether lactation function could be reinitiated after a period of extended milk stasis. Involution was induced by milk stasis in lactating Holstein cows for a period of 11 d. On d 11, one side of the mammary gland was milked twice daily for 3 d. The contralateral side remained unmilked for the 14-d experimental period. Cows were slaughtered, and mammary tissue was collected from both udder halves for further analysis. Mammary secretion volume was partially restored in the milked udder half, but reestablished milk yields were variable among cows. A partial recovery of lactation function was further indicated by elevated levels of lactose and protein profiles resembling milk in mammary secretions from the milked glands. Lactose and protein profiles from the unmilked glands were similar to those of glands undergoing involution. Lactoferrin levels were elevated in secretions from the milked and unmilked udder halves. Casein and lactoferrin synthesis by mammary explants and beta-casein and lactoferrin mRNA abundance in mammary tissues corresponded to protein profiles from milked and unmilked mammary secretions. alpha-Lactalbumin mRNA was variable but was more abundant in the milked glands compared with the unmilked glands. Lectin fluorescence microscopy for soybean agglutinin preferentially stained the apical surface of the mammary epithelial cells from the milked glands. Staining was absent in the unmilked glands and suggested resumption of lactation function in all such milked glands. These results suggest that mammary involution can be partially reversible after 11 d of milk stasis.

Bovine milk inhibits both adhesion of Helicobacter pylori to sulfatide and Helicobacter pylori-induced vacuolation of vero cells

Adhesion of Helicobacter pylori to gastric mucosal cells is an initial important step in colonization and infection. To study adhesion, we investigated whether milk inhibits the adhesion of Helicobacter pylori to sulfatide, an acidic glycosphingolipid that exists in human gastric mucosa and to which Helicobacter pylori adheres. As a measure of functional significance, we also studied whether milk inhibits Helicobacter pylori-induced vacuolation of Vero cells. We used sulfatide-coated polystyrene plates and studied the effect of bovine milk on the adhesion of Helicobacter pylori to sulfatide. We used Vero cells for Helicobacter pylori-induced vacuolation. Bovine milk 100- to 200-fold diluted significantly inhibited both adhesion of Helicobacter pylori to sulfatide and Helicobacter pylori-induced vacuolation in Vero cells. Bovine milk significantly inhibited adhesion of Helicobacter pylori to MKN-45 cells and Lewis b antigen-coated polystyrene plates. In addition, these results suggest that bovine milk contains active substances that inhibit both adhesion of Helicobacter pylori to mucosa and vacuole formation. Bovine milk may have a protective effect on the gastric mucosa in Helicobacter pylori-associated gastritis.

Supplementary feeding in maternity hospitals and the risk of cow's milk allergy: A prospective study of 6209 infants

BACKGROUND

Early feeding with cow's milk (CM) may increase the risk of cow's milk allergy (CMA).

OBJECTIVE

We sought to examine prospectively whether supplementary feeding of CM at the maternity hospital would increase the risk when compared with feeding with pasteurized human milk or hydrolyzed formula.

METHODS

We studied 6209 unselected healthy, full-term infants, of whom 5385 (87%) required supplementary milk while in the hospital. The infants were randomly assigned to receive CM formula (1789 infants), pasteurized human milk (1859 infants), or whey hydrolysate formula (1737 infants). The comparison group (824 infants) was composed of infants who were exclusively breast-fed. The infants were followed for 18 to 34 months for symptoms suggestive of CMA. The primary endpoint was a challenge-proven adverse reaction to CM after a successful CM elimination diet.

RESULTS

The cumulative incidence of CMA in the infants fed CM was 2.4% compared with 1.7% in the pasteurized human milk group (odds ratio [OR], 0.70; 95% confidence interval [CI], 0. 44-1.12) and 1.5% in the whey hydrolysate group (OR, 0.61; 95% CI, 0. 38-1.00). In the comparison group, CMA developed in 2.1% of the infants. Among the infants who required supplementary feeding at hospital, both exposure to CM while in the hospital (OR, 1.54; 95% CI, 1.04-2.30; P =.03) and obvious parental atopy (OR, 2.32; 95% CI, 1.53-3.52; P <.001) increased the risk of CMA.

CONCLUSIONS

Our data indicate that feeding of CM at maternity hospitals increases the risk of CMA when compared with feeding of other supplements, but exclusive breast-feeding does not eliminate the risk.

[Investigations on the behavior of C-reactive protein, cell count, lactose content as well as electric conductivity in quarter milk samples of subclinically diseased quarters of the udders in relation to bacteriologic results]

Inflammations of the udder influence the amount of somatic cells and lactose as well as electrical conductivity in milk. They are often caused by bacterial agents. Similar reactions are to be seen in relation to C-reactive protein (CRP). The amount of CRP in milk depends on concentration and characteristics of the agents and the phase of inflammation. We found a significant increase of CRP in milk samples with Streptococcus (Sc.) uberis. There was no significant difference in CRP concentrations in samples with coagulase positive Staphylococcus spp. (CPS) and bacteriological negative samples and such with Corynebacterium (C.) bovis, Micrococcus spp. and Staphylococcus (S.) epidermidis. We only found high correlations to the amount of somatic sells and lactose as well as electrical conductivity in samples with Sc. uberis. The results of our investigations show that CRP may be a parameter for better understanding subclinical inflammations of udder.

Calliandra calothyrsus as a supplement for milk production in the Kenya highlands

Two on-farm experiments and one on-station observation were conducted between July 1994 and September 1995 to study the effect of supplementation with fresh fodder of Calliandra calothyrsus on milk production from grade Friesian and Ayrshire cows in the second trimester of their lactations. The cattle were kept under zero-grazing systems on small farms in the coffee-based land use system at altitudes of 1500 to 1800 m on the slopes of Mt Kenya. These cows form a pivotal part of the farming system since they produce both milk for sale and manure for crop production. Milk production is normally in the region of 10 kg/cow per day when the animals are fed on a diet based on Napier grass and crop residues, together with 2-4 kg day of commercial concentrate. In terms of milk production, 3 kg of fresh calliandra had the same effect on yield as 1 kg of additional dairy meal and, at normal production levels, the effects of the two supplements were strictly additive. Calliandra had a marked positive effect (about a 10% increase) on the butterfat content of the milk, a factor that was highly valued by farmers, even though institutional buyers as yet offer no premium price for milk quality. The average small farm can produce enough calliandra fodder to supplement two dairy cows and some additional small stock from relatively underutilized niches along the farm perimeter and terrace risers, without any adverse effect on current levels of crop production.

Type of milk consumed can influence plasma concentrations of fatty acids and minerals and body composition in infant and weanling pigs

Two experiments using 42 crossbred neonatal pigs to compare the effects of caprine and bovine milk on growth, apparent nutrient digestibility and body composition were conducted. At age 72 h, pigs were removed from their dams and randomly divided into two groups, housed separately in stainless steel metabolism cages and were fed a predetermined amount (300 mL/kg body weight) of pasteurized, nonfortified whole, caprine or bovine milk. Body composition was determined using dual energy X-ray absorptiometry (DXA). In Experiment 1, 22 intact male pigs were used for a 31-d experimental period. There was no significant (P > 0.05) dietary effect on growth, apparent nutrient digestibility or body composition. Significant differences (P < 0.05), however, were observed in plasma of C 8:0, C 10:0 and C 12:0 concentrations. In Experiment 2, 20 pigs (10 intact males and 10 females) were used in a 2 x 2 factorial experiment for 52 d. Pigs fed caprine milk had higher (P < 0.05) plasma concentrations of C10:0 and C12:0 as well as Na, Mg and Zn than those fed bovine milk. At Day 52, pigs fed caprine milk had less body fat (P < 0.001) and higher (P < 0.06) bone mineral density than those fed bovine milk. Drymatter, N and total mineral intake of male pigs was higher (P < 0.05) than female pigs. Also, male pigs had higher (P < 0.05) plasma concentrations of C12:0 than females. This study demonstrates that the type of milk consumed can influence plasma concentrations of fatty acids, minerals and body composition in pigs.

Permanent implantation of a reinforced polytetrafluoroethylene vascular graft for treatment of artificial defects of the teat cistern mucosa in cows

OBJECTIVE

To evaluate use of a reinforced polytetrafluoroethylene vascular graft for treatment of an artificial defect of mucosa of the teat cistern in lactating cows.

DESIGN

Prospective study.

ANIMALS

9 clinically normal lactating dairy cows.

PROCEDURE

A 20-mm wide circumferential area of mucosa was sharply excised from the cistern of 1 teat on each cow 10 days after spontaneous calving, and the lesion was covered by a graft. After 14 days of passive milk drainage, routine milking was resumed. Follow-up examinations were performed during the next 2 lactation periods and included evaluation of wound healing, location and sonographic appearance of the implant, milk flow and yield, and somatic cell counts. Cows were slaughtered, and teats and mammary glands were examined microscopically.

RESULTS

Implants had partially to totally collapsed within 30 to 90 days. Milk flow was significantly increased by day 15 of the first lactation, but decreased significantly by day 300 of lactation 1. At the end of lactation 1, milk flow had ceased in 3 out of 7 quarters. Only 3 of 9 quarters drained through grafted teats were milkable at the end of the study. Somatic cell counts of these quarters were significantly increased in the first lactation period. At necropsy, 2 grafts were in the teat cistern, but only 1 was incorporated into the mucosa by connective tissue. The mucosa was thickened in all teats with grafts, and there was epithelial metaplasia and granulation tissue proliferation.

CLINICAL RELEVANCE

Use of a polytetrafluoroethylene graft can preserve patency in the first lactation period. However, the graft may not be sufficiently incorporated into the mucosa if routine machine milking is resumed 2 weeks after implantation. )

Sperm viability in ram semen diluted and stored in three different extenders

Semen was collected with an artificial vagina from 4 one-year-old rams, in order to study the changes in sperm motility and membrane integrity of spermatozoa split-diluted and stored at 5 degrees C during 7 days in sodium citrate, Tris, and milk-based extenders, respectively. Sperm motility was assessed subjectively and sperm membrane integrity was determined using the fluorescent probes Calcein-AM and Ethidium homodimer. Representative samples were studied using scanning electron microscopy (SEM). The average incidence of sperm motility decreased over time in all the extenders (p < 0.001). The incidence of spermatozoa showing progressive motility and intact plasma membrane was significantly higher in semen diluted with sodium citrate than in the other 2 extenders following 4 days of dilution until the end of the study. Evaluation with SEM confirmed the findings obtained with the supra vital fluorescent dyes. The results of the present study indicated that there were no differences between sodium citrate-, Tris- or milk-based extenders when ovine liquid semen was stored at 5 degrees C during a short period (2 days). However, when semen was stored for longer time, spermatozoa in the sodium citrate-based extender sustained its viability better.

Comparison of treatment of mastitis by oxytocin or antibiotics following detection according to changes in milk electrical conductivity prior to visible signs

Mastitis was induced in dairy cows by infusion of 500 cfu of Streptococcus uberis into the mammary gland. Most infections developed to clinical disease, and the majority were predicted by changes in the electrical conductivity of the foremilk. The benefits of clinical prognosis and bacteriological cure were determined for cases that were treated when predicted to develop into clinical mastitis and compared with cases that were allowed to develop until milk clotted or until pyrexia before intramammary antibiotic treatment was used. Treatment prior to clinical mastitis included use of intramammary antibiotic or intramuscular oxytocin to allow stripping of residual milk to remove bacteria. All infections in which treatment was delayed resulted in clinical mastitis that was cured clinically and bacteriologically by sustained treatment using a broad-spectrum intramammary antibiotic preparation once daily but requiring a mean treatment time of 10 d. It was possible to prevent clinical mastitis from developing and to eliminate all infections in cows that were treated early when the developing disease was predicted by changes in the electrical conductivity of quarter foremilk and was treated aggressively by administering an intramammary antibiotic at each milking for 3 d. Treatment of 20 IU of oxytocin at six successive milkings of cows that were predicted to develop disease eliminated 25% of the infections, but 75% of the cows developed clinical mastitis. Those cases were resolved by sustained daily treatment using the same intramammary antibiotic. Elimination (100% clinical and bacteriological cure) of all infections caused by Strep. uberis was possible with early and aggressive or sustained use of the intramammary antibiotic. The early intervention using an intramammary antibiotic, when infection was first indicated by changes in the electrical conductivity of milk, was the most efficient method to achieve cure and led to quicker recovery of milk quality to a saleable standard.

Genetic parameters for the milk coagulation properties and prevalence of noncoagulating milk in Finnish dairy cows

The genetic parameters were estimated for milk coagulation properties and milk production traits, and the prevalence of noncoagulating milk in the Finnish dairy cattle population was investigated. Data were included for 789 Finnish Ayrshire cows and 86 Finnish Friesian cows from 51 herds. The animal model used for estimation included fixed effects for parity, stage of lactation, breed, and herd. Further, effects of milk protein genotypes on phenotypic and genetic variation in the studied traits were examined. Heritability estimates for the milk coagulation properties were moderately high. The kappa-casein B allele was associated with the best phenotypic and genetic values for curd firmness, and the A and E alleles were associated with the poorest. About 24% of the additive genetic variation in the curd firmness was due to milk protein polymorphism. About 8% of the Finnish Ayrshire cows in the present study produced noncoagulating milk. Because of the occurrence of the noncoagulating milk and a possibly unfavorable genetic trend in the milk coagulation properties, it would be important to improve these traits in the Finnish Ayrshire breed. Milk coagulation properties could be improved directly by selecting for these traits or indirectly by favoring the kappa-casein B allele or by selecting against genetic markers associated with poorly coagulating or noncoagulating milk.

Influence of restricted suckling and level of feed supplementation on postpartum reproductive performance of zebu and crossbred cattle in the semi-arid tropics

This study was carried out in central Tanzania on a group of 45 Zebu and 37 crossbred cows which were 4 to 10 years old. At calving time, the animals were allocated to one of the 4 treatment groups. In addition to free access to grazing for all cows in the study, in group H:AR (n = 18), cows were fed a high level of concentrate supplementation (4kg/day) and calves were artificially reared; in group H:RS (n = 24), cows were fed a high level of concentrate supplementation (4kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. In group L:AR (n = 23) cows were fed a low level of concentrate supplementation (2kg/day) and calves were artificially reared; and in group L:RS (n = 17) cows were fed a low level of concentrate supplementation (2kg/day) and calves were only allowed restricted suckling up until the weaning age of 6 months. Milk progesterone was used as a means of determining the postpartum resumption interval (PRI) and the interval from parturition to conception (PCI). The overall PRI was 47.4 +/- 0.4 days and was significantly affected by breed but not by calving season, with crossbred cows exhibiting a shorter PRI than Zebu cows. The effect of the treatments was significant, with cows in the group H:AR displaying a significantly shorter PRI than those in the other groups, while cows in group L:RS showed a significantly longer PRI than those in the other groups. The overall PCI was 149.5 +/- 3.7 days, and was not significantly affected by breed or calving season. The effect of the treatments was significant, with cows in the group H:AR having a significantly shorter PCI than cows in the other groups, while cows in group L:RS showed a significantly longer PCI than those in the other groups. Crossbred cows had higher live weights at calving (299.4 kg) than Zebu cows (272.6 kg), while all cows gained weight during the first 3 months after calving. The treatments had a significant effect on weight gain, with cows in the group H:AR gaining significantly more weight than those in the other groups. Cows which had high live weights at calving exhibited significantly shorter PRI and PCI than the lighter cows. Animals which had gained more than 5 kg during the first month after calving, or which had gained more than 8 kg during the first 3 months after calving, showed significantly shorter PRI and PCI than cows which had gained less weight. The results show that the calf rearing system and the level of feed supplementation interact with each other and can influence the postpartum anoestrous period in Zebu and Zebu crossbred cattle. Increasing the level of nutrition in restricted suckling cows tended to improve the postpartum anoestrous period, but the positive effects of supplementation could not completely compensate for the negative effects of suckling.

The effect of recombinant TGFalpha, human milk, and human milk macrophage media on gut epithelial proliferation is decreased in the presence of a neutralizing TGFalpha antibody

OBJECTIVE

An in vitro model was devised to compare the relative effects of recombinant transforming growth factor-alpha (TGFalpha), aqueous human milk, and human milk macrophage (HMM) medium on human fetal small intestinal cell (FHs-74) proliferation.

METHODS

Recombinant TGFalpha at increasing concentrations (range 0.01-1,000 ng/ml media), the aqueous fraction of human milk (AHM), or HMM medium was added to FHs-74 cells in the presence or absence of a neutralizing TGFalpha antibody (1 microgram/ml medium). At 24 h, cell proliferation was measured and expressed as percent control. The experimental variables were (1) activators of cell growth (TGFalpha, AHM, and HMM medium); (2) increasing concentrations of TGFalpha, and (3) neutralizing antibody to TGFalpha. The dependent variable for all experiments was cell proliferation.

RESULTS

Significant effects for growth stimulators and TGFalpha concentration as measured by cell proliferation were found. Specifically, there was a dose-dependent effect of TGFalpha on cell proliferation to the 5-ng/ml concentration, with a plateau reached in cell proliferation at higher concentrations. The stimulatory effect of TGFalpha was decreased in the presence of TGFalpha antibody (mean +/- SD 22 +/- 7. 1% decline, p < 0.001). In the presence of TGFalpha antibody, there was a 25 +/- 3.1% decline in HM-stimulated growth (p < 0.004), and a 27.6 +/- 3.2% decline in HMM medium-stimulated growth (p < 0.001).

CONCLUSIONS

Neutralization of recombinant TGFalpha and that present in human milk and HMM medium by TGFalpha antibody led to a consistent decrease in in vitro human fetal small intestine epithelial proliferation without affecting cell viability. These results support the hypothesis that TGFalpha, whether derived from human recombinant sources, human milk or HMM medium has a measurable, trophic effect on in vitro human gut epithelial cells.

Endogenous opioids and the first suckling episode in the rat

Endogenous activity at opioid receptors affects the appetitive behavior of Caesarean-delivered rat pups during presentation of a surrogate nipple that provides milk. Blockade of opioid receptors by peripheral injection of naloxone has no effect on responses evoked by the surrogate nipple. Similarly, blockade of caudal brain opioid receptors by injection of naloxone into the cisterna magna has no effect on the pup's behavior in response to the surrogate nipple. However, blockade of rostral opioid receptors by injection of naloxone into the cerebral ventricles increases the latency to the first oral grasp response, decreases total time on the nipple, and virtually eliminates ingestion of milk from the surrogate nipple (Experiment 1). Blockade of endogenous opioid activity does not affect responses to a nipple that provides distilled water (Experiment 2) or to an empty surrogate nipple (Experiment 3). These data indicate that during the initial suckling episode endogenous opioids in rostral brain regions affect the pup's behavioral responses to the nipple. The results are consistent with the hypothesis that milk engages opioid systems during the first suckling and that endogenous opioids play a role in early suckling.

Caprine blastocyst development after in vitro fertilization with spermatozoa frozen in different extenders

The feasibility of using frozen-thawed semen in caprine IVF outside the breeding season was investigated. Electroejaculated spermatozoa from a Nubian buck were washed twice and then frozen in skim milk- or in egg yolk-based extenders. Goat oocytes were matured and inseminated by frozen-thawed spermatozoa selected by swim-up. In vitro fertilization was performed in a modified defined medium (mDM), altered experimentally, for 24 h. Embryos were cultured in 50 microL of c-SOF + NEA for 9 d. The percentages of oocytes exposed to heparin-capacitated spermatozoa, (previously cryopreserved in skim milk-based extender) that cleaved, reached morula, blastocyst and expanded blastocyst stages were 82.8, 57.1, 35.7 and 30.0%, respectively. Without heparin treatment the rates for cleavage, morula, blastocyst and expanded blastocyst stages were 44.3, 31.4, 18.6 and 8.6%, respectively. Therefore, heparin treatment was included in sperm capacitation. Use of spermatozoa with BSA in the IVF medium yielded no cleavage. Although extenders containing 8 to 20% egg yolk enabled good sperm motility after cryopreservation, in vitro fertilizing ability was compromised under our conditions. By contrast, semen commercially processed in season in an egg yolk-based diluent remained effective for IVF. The highest proportion of blastocysts resulted from the use of spermatozoa diluted in a skim milk extender, heparin capacitation, and insemination in medium containing lamb serum.

Effects of level and type of energy source (volatile fatty acids or glucose) on milk yield, composition and coagulating properties in dairy cows

Four fistulated Holstein cows were arranged in a 4 x 4 Latin square design to study the effects of level and type of energy source on milk yield and composition. Treatments consisted of a basal diet fed alone (low energy treatment) or with 3.3 Mcal of net energy for lactation from extra nutrients perfused either into the rumen (either propionic acid or a mixture of volatile fatty acids) or into the duodenum (glucose). Increasing the energy input without changing the volatile fatty acid profile improved milk yield and slightly increased milk protein and fat yields. Compared with the isoenergetic mixture of volatile fatty acids, both propionic acid and glucose infusions significantly decreased fat content (-4.5 g/kg) and yields (respectively, -111 and -160 g/d), but affected fatty acid proportion and yield differently (more elongation process and less C18 with glucose infusion). Protein yield was slightly increased by propionic acid infusion but not by glucose because of the counterbalanced effects on milk yield (-1.3 kg/d) and protein content (1.5 g/kg). The coagulating properties of milk were directly linked to variations in protein, casein and mineral contents. In conclusion, propionic acid or glucose scarcely affected milk protein content, but induced a similar decrease in milk fat content probably through different metabolic pathways.

The coordination and interaction between respiration and deglutition in young pigs

The anatomical pathways for inspired air and ingested food cross in the pharynx of mammals, implying that breathing and swallowing must be separated either in space or in time. In this study we investigated the time relationship between swallowing and respiration in young pigs, as a model for suckling mammals. Despite the high morphological position of the larynx in young mammals, allowing liquid to pass in food channels lateral to the larynx, respiration and swallowing are not wholly independent events. Although, when suckling on a veterinary teat, the swallows occurred at various points in the respiratory cycle, there was always a period of apnea associated with the swallow. Finally, an increase in the viscosity of the milk altered this coordination, changing respiratory cycle length and also restricting the relative rate at which swallows occurred in some parts of the respiratory cycle. These results suggest that the subsequent changes in respiratory activity at weaning, associated with passage of a solid bolus over the larynx, is preceded by the ability of the animal to alter coordination between respiration and swallowing for a liquid bolus.

A bovine mammary endothelial/epithelial cell culture model of the blood/milk barrier

The complex nature of the mammary gland has hampered in-depth studies of the relationship of the circulatory system to cells lining the teat ducts and alveoli of the gland. This study reports an in vitro model of endothelial and epithelial cells separated by a subcellular matrix that simulates the blood milk barrier of the bovine mammary gland. Dual chamber culture dishes with a porous membrane separating the upper and lower chamber were used. Endothelial and epithelial cells were cultured on opposite sides of the porous membrane. A collagen and fibroblast subcellular matrix, separating the 2 cell layers, simulated the in vivo interstitial tissue. Changes in surface binding of anti-bodies to polymorphonuclear neutrophils (PMN) following their migration from the upper to the lower chamber simulated the passage of PMN from blood to milk. Changes in the binding of antibodies to PMN agreed with results observed following the migration of PMN from blood to milk in vivo. This gives credence to the model's potential value for studies where more direct observation of the blood/milk barrier is required. The model will be further tested for its usefulness as an assay for determining: 1) antibiotic diffusion from milk to blood and from blood to milk, 2) cytotoxicity of prophylactic and therapeutic mammary infusion products, 3) factors affecting bacterial adhesion and penetration of mammary epithelial tissue, 4) effectiveness of antibodies present in lacteal secretions in preventing bacterial adhesion, and 5) the feasibility of gene constructs to induce synthesis and secretion of mastitis-preventing compounds and prophylactic and therapeutic compounds for treatment of human disorders.

A QTL affecting milk yield and composition maps to bovine chromosome 20: a confirmation

As part of a whole genome scan undertaken to detect quantitative trait loci (QTL) affecting milk yield and composition, we have genotyped a granddaughter design comprising 1152 sons for six microsatellite markers spanning bovine chromosome 20. An analysis performed across families provided strong evidence (experiment-wise P-values < 0.01) for the presence of a QTL affecting primarily protein percentage towards the telomeric end of the chromosome. A founder sire, shown in a previous study to segregate for a similar QTL in the corresponding chromosome region, was characterized by 29 and 57 sons and maternal grandsons, respectively, in the present design. Sorting corresponding sons and grandsons by paternal or grandpaternal allele provided significant evidence for the segregation of a QTL on chromosome 20. Altogether these results confirm the location of a QTL affecting milk production on bovine chromosome 20.

Metabolic and endocrine traits of neonatal calves are influenced by feeding colostrum for different durations or only milk replacer

Bovine colostrum contains various essential nutrients, antibodies, hormones and growth factors that are important for nutrient supply, host defense, growth and for general neonatal adaptation. We have studied effects of colostrum fed for different durations on selected metabolic and endocrine traits in the first week of life in calves. Calves were fed colostrum twice daily for 3 d (group C6) or colostrum only as their first meal (group C1), followed by milk replacer up to d 7, or they were only fed milk replacer but no colostrum (group M). Plasma concentrations of immunoglobuline G and activities of enzymes (gamma-glutamyltransferase, aspartate-aminotransferase, lactate-dehydrogenase, glutamate-dehydrogenase) increased in groups C6 and C1 after first feeding, but not in group M. Postprandial plasma glucose concentrations on d 2 increased significantly more in groups C6 and C1 than in group M. Plasma triglycerides on d 2 and plasma phospholipid and cholesterol concentrations on d 7 were significantly higher in group C6 than in groups C1 and M. Plasma insulin concentrations on d 2 tended (P = 0.07) to increase more postprandially in group C6 than in group M and postprandial plasma glucagon concentrations on d 1 increased more in groups C6 and C1 than in group M and remained elevated on d 2 only in group C6. Plasma cortisol concentrations decreased postprandially in all three groups and were highest on d 2 and d 7 in group M. Plasma triiodthyronine and thyroxine concentrations decreased in the first week of life in all calves, whereas plasma prolactin concentrations were greatest on d 7 in group C6. In conclusion, various metabolic and endocrine traits were influenced by whether colostrum was fed and the duration of colostrum feeding.

Subclinical mastitis assessed by deviations in milk yield and electrical resistance

Concurrent falls in milk production and electrical resistance of composite milk were examined in Israeli Holstein cows. The cows were milked three times a day by a system that recorded yield and the lowest electrical resistance in the composite milk from the four glands. The study included two groups: cows that experienced on day 0 a decline in resistance and milk production > or = 20% from the mean of the previous 9 d (62 cows, case group) and cows that experienced no such episodes over 9 d before and after a fixed day (118 cows, control group). Bacteriological status and somatic cell count (SCC) or California mastitis test scores were assessed on the fixed day in the control group, and on days 0, 1 and 2 in the case group. California mastitis test scores greater than 2 and SCC thresholds of 5 x 10(5) cells/ml were used to create two classes of leucocytosis. There was no statistically significant difference between the two groups in frequency distributions of pathogens and their types: in 30% of cows infection was not detected, 33% were infected by major pathogens (95% of which were Staphylococcus aureus), and 53.5% by minor pathogens (80% Micrococcus spp.). Cows in the case group had lower milk production during the 8 d following day 0. Mean electrical resistance was lower in infected cows and particularly in cows infected by Staph. aureus. High leucocytosis was associated with reduced electrical resistance in both groups, and was found in 93% of cows in the case group v. 25% in the control group. The results suggest that falls in electrical resistance of milk and in milk production were not linked to a specific pathogen, and were followed by 3-8 d of reduced milk production and electrical resistance. The study suggests that there are episodic aggravations in mammary health that do not evolve into clinical mastitis but may induce significant losses in milk yield and quality.

Filling the gut activates paradoxical sleep in suckling rats

Recent studies with rat pups suggest that suckling and sleeping are coordinated through milk-related events in the gut. Our experiments revealed that suckling rats respond to milk in the upper gastrointestinal tract by displaying more paradoxical sleep (PS) as the volume increases to 4% of the pup's body weight. Conversely, gastric loads larger than 4% reduced PS as a function of the volume. We also discovered that filling the stomach with warm non-nutritive paraffin is as effective as an equivalent volume of warm milk for enhancing PS. Although the temperature of the gut load did not appear to play a major role in the amount of PS displayed, increasing ambient temperature from 22 degrees C to 32 degrees C increased PS significantly. Moreover, a gut load of milk (4% body weight) was more effective than the same volume of water or no load for enhancing PS. Gut loads that stay in the stomach and warm ambient temperature appear to work in an additive manner to enhance PS. The electrophysiological data together with the stomach volume data and behavioral observations of nipple attachment revealed that milk-related stimuli along the gastrointestinal tract, especially gastric distension, alter sleep patterns in predictable ways that permit us to distinguish postingestive satiety from a deprivation state and nimiety in suckling rats.

Diurnal rhythm of melatonin in bovine milk: pharmacokinetics of exogenous melatonin in lactating cows and goats

We investigated whether the melatonin levels in bovine milk exhibit a similar daily rhythm as serum levels. In 4 Ayrshire cows at the beginning of the lactation period in May the nocturnal rise in milk melatonin was moderate (from 7 +/- 2 pg/ml at noon to 15 +/- 1 pg/ml at night; mean +/- SEM) and did not correlate well with the melatonin level in serum (from 7 +/- 2 pg/ml to 27 +/- 7 pg/ml, respectively). On the other hand, 6 cows in a later phase of lactation, studied in February, showed a clear long-lasting nocturnal melatonin increase both in serum (from 9 +/- 1 pg/ml at noon to 26 +/- 3 pg/ml at night) and in milk (from 12 +/- 5 pg/ml to 26 +/- 7 pg/ml, respectively). Melatonin kinetics during lactation was studied in more detail in 4 Ayrshire cows and 4 dairy goats by giving an intravenous bolus injection of melatonin. A 3-compartment model with melatonin elimination from the central compartment was used to describe the data. The values (mean +/- SD) for the cows and the goats were: elimination half-life 27 +/- 4 min and 27 +/- 1 min, mean residence time 24 +/- 4 min and 18 +/- 4 min, steady state distribution volume 1.0 +/- 0.3 l/kg and 0.6 +/- 0.1 1/kg (p < 0.05), and plasma clearance 0.044 +/- 0.004 l/kg/min and 0.035 +/- 0.011 l/kg/min, respectively. Following injection, the melatonin concentration in milk increased rapidly and exceeded the corresponding serum value 15-30 min later, remaining thereafter above the serum level. Our results suggest that milk melatonin levels reflect blood concentrations of melatonin with a short delay.

Experimental study of the first suckling episode: rat pups ingest fluids through a surrogate nipple

The present study reported a new technique in which pups ingested fluids from a surrogate nipple. Cesarean-delivered pups tested before suckling experience showed oral grasp responses and ingested milk from the surrogate nipple. Pups ingested equal amounts of distilled water and milk and rejected saline. After ingesting milk from the surrogate nipple, pups remained attached to an empty surrogate nipple, while pups exposed to distilled water or saline did not show sustained attachment. Brief experience with milk from an oral cannula or from a surrogate nipple elicited sustained attachment to an empty nipple. Pups ingesting milk from a surrogate nipple showed increased intake of water and saline from the nipple when tested subsequently. The surrogate nipple provides a new technique for experimental study of early suckling behavior. The results suggest that initial experiences with milk may reinforce components of early suckling behavior.

Lactose intolerance associated with fractures of weight-bearing bones in Finnish women aged 38-57 years

Lactose intolerance (LI) often results in decreased calcium intake. To test if long-term low intake of calcium affects bone strength, we examined fracture risks related to LI in women aged 38-57 years. The 11,619 Finnish women aged 47-56 years who responded to the baseline postal inquiry of the Kuopio Osteoporosis Risk Factor and Prevention Study in 1989 formed the study population. In all, 896 women reported LI and 1299 women reported a fracture in 1980-1989. Current intake of dairy calcium was lower in women with LI (570 mg/d) than in the other women (850 mg/d) (p < 0.0001). The fracture risk in general was slightly elevated in women with LI compared with the other women, with an odds ratio (OR) (95% CI) of 1.33 (1.09-1.62). However, the fractures at the three most common sites (wrist, ankle, and rib) were not related to LI. In contrast, fractures at the tibia and metatarsal were strongly related to LI with ORs of 3.31 (1.51-7.24) and 2.84 (1.47-5.50), respectively. The adjusted OR for nonankle lower body fractures combined was 2.15 (1.53-3.04), whereas that for all upper body fractures combined was 1.15 (0.88-1.54). The 10 women with LI and a tibial or metatarsal fracture showed a 19% lower femoral BMD than all the other women in the densitometry subsample of 3222 women (p < 0.001). Long-term premenopausal calcium deficiency differentially affects bones with weight-bearing nonankle bones being at the greatest risk of suffering reduced strength.

Comparison of various transport media on human periodontal ligament cell viability

The purpose of this study was to determine the ability of various solutions to maintain human periodontal ligament cell (PDL) viability in vitro. PDL cells were obtained from extracted third molars and premolars of healthy individuals. These cells were placed into 24-well culture plates containing milk, Save-A-Tooth, Save-A-Tooth supplemented with platelet-derived growth factor-BB (PDGF), or Gatorade at a concentration of approximately 80,000/well. Cells left dry served as negative controls, and cells placed in Eagles' Minimal Essential Medium served as positive controls. At 1, 2, 4, 8, and 12 h, cell viability was evaluated using an MTS assay and an ELISA plate reader to determine optical density. ANOVA and Student-Newman-Keuls tests indicated that milk and Save-A-Tooth with PDGF are suitable as transport medium for avulsed teeth and that the addition of PDGF to Save-A-Tooth may enhance its ability to maintain PDL cell viability. They also suggests that Gatorade would be unsuitable as a transport medium.

[A closer look at the milking machine]

Machine milking has changed enormously in the past decades. The simple milking machine developed at the end of the nineteenth century has become a complex appliance which removes milk from the udder in a fast and efficient way. There is no doubt about the importance of a well functioning milking machine as regards milk quality and udder health. This article reviews the literature on the basic mechanics of machine milking, with special emphasis on the action of the cluster during milking. The movement of the teat cup liner is particularly important in influencing the efficiency of milk extraction and udder health. Therefore special attention is paid to the operation of the liner, how it works, and how the opening and closing of the liner affects the milking process. The functioning of the pulsator, the vacuum fluctuations occurring during milking, and the effect of these fluctuations on the opening and closing of the liner are discussed. The maintenance of the milking machine is also described.

Role of milk-borne vs endogenous insulin-like growth factor I in neonatal growth

Neonatal pigs are characterized by a high efficiency of nutrient utilization and rapid growth rate. The utilization of dietary protein for lean tissue growth is particularly efficient in neonatal pigs and is associated with a high rate of skeletal muscle protein synthesis and deposition. In support of these high growth rates, neonatal pigs consume a milk diet that has a high biological value and is abundant in growth factors, including insulin and IGF-I. During the neonatal period, there are developmental changes in the circulating concentrations of, and tissue responsiveness to, hormones, particularly insulin, IGF-I, and growth hormone that play a central role in growth regulation. Our goal has been to characterize the dietary factors and specific aspects of endocrine function that are responsible for the anabolic stimulus that helps to sustain the high rates of protein deposition in neonatal pigs. Our results suggest that, despite the abundance of growth factors in milk and colostrum, the intake of nutrients is the primary anabolic stimulus for protein synthesis and this response declines with age. There is, however, a nonnutritive and as-yet-unidentified component in colostrum that provides a specific anabolic stimulus for skeletal muscle in newborns, but this is probably neither insulin nor IGF-I. Our studies also indicate that circulating concentration of IGF-I are not a primary stimulus of skeletal muscle protein synthesis and that the primary endocrine signal that mediates the response to nutrient intake may be insulin. Future research should address how the local expression of IGF and the function of insulin and IGF receptors affect the responsiveness of anabolic processes to nutrient intake and hence the efficiency of neonatal growth.

Time course of milk accumulation-induced opening of mammary tight junctions, and blood clearance of milk components

Eight cows in early lactation were used to study the effect of milk accumulation on the state of mammary tight junctions and to examine alpha-lactalbumin as an indicator of tight junction permeability in vivo. During three successive periods, the cows were milked twice (4 days), once (6 days), and twice daily (4 days). Plasma lactose, alpha-lactalbumin, and milk sodium concentrations were used as indicators of tight junction permeability. Furthermore, four cows were used to study the clearance of lactose and alpha-lactalbumin from the blood. Milk yield during once-daily milking decreased by 15.4% (P < 0.001). All indicators of mammary tight junction patency increased (P < 0.05) transiently during once-daily milking and indicated that tight junctions opened after approximately 18 h. Plasma alpha-lactalbumin and lactose were highly correlated (r = 0.82, P < 0.001), indicating the suitability of plasma alpha-lactalbumin as an indicator of tight junction status in vivo. Clearance of alpha-lactalbumin and lactose from the blood was best described by a biexponential model. Elimination half-lives for lactose and alpha-lactalbumin were 44 and 40 min, respectively. This study showed that milk stasis during early established lactation induces tight junctions to switch to a leaky state after approximately 18 h and to revert to the closed state shortly after milking.

Milk accumulation triggers apoptosis of mammary epithelial cells

Continuous milk production is a consequence of a complex interplay of lactogenic hormones and it depends on the suckling stimulus during lactation. Involution is associated with a massive engorgement of the gland with milk followed by apoptosis of secretory epithelial cells and a restructing of the gland. Sealing of a single gland during lactation is sufficient to induce an initial engorgement and a subsequent collapse of alveolar structures and massive epithelial cell death while the other glands of the same animal remain morphologically and functionally in a lactating state. Many markers of involution such as sulfated glycoprotein-2, protein kinase A, transcription factor AP-1 and most notably stromelysin are induced in sealed glands. These findings suggest a cell death pathway which is independent of the systemic levels of lactogenic hormones but which is triggered by an accumulation of apoptosis-inducing factors in the milk, in the lobulo-alveolar structures or by a physical distortion of secretory epithelial cells generated by the engorgement.

The effects of early antibiotic treatment following diagnosis of mastitis detected by a change in the electrical conductivity of milk

Mastitis was induced experimentally by infusion of Streptococcus uberis or Staphylococcus aureus into the mammary glands of lactating dairy cows. Clinical mastitis was identified when clots appeared in foremilk (conventional diagnosis) or was predicted by changes in the electrical conductivity of foremilk (early diagnosis). The responses to intramammary antibiotic treatment that was initiated after early diagnosis of mastitis and after conventional diagnosis were compared. Early treatment significantly limited the severity of the disease and, in many cases, prevented the appearance of any visible signs of infection. Milk yield was less depressed, and the somatic cell count (SCC) was lower, when treatment was initiated earlier. The SCC of the quarter at the time mastitis was predicted was approximately 2 x 10(6) cells/ml for both pathogens, which was significantly less than when clots appeared at conventional diagnosis, approximately 4 x 10(6) and 12 x 10(6) cells/ml for Staph. aureus and Strep. uberis, respectively. The time required for SCC to recover to < 4 x 10(5) cells/ml was significantly less, approximately half, for both pathogens following early detection and early initiation of treatment. When treatment was administered in response to early detection, the bacteriological and clinical cure was almost complete, and the amount of antibiotic used was < or = 50% less. Obvious benefits for milk yield and quality and the health of the cow would result when changes in the electrical conductivity of milk are used to predict clinical mastitis and when treatment is initiated early.

Sequence variations in the bovine growth hormone gene characterized by single-strand conformation polymorphism (SSCP) analysis and their association with milk production traits in Holsteins

Sequence variations in the bovine growth hormone (GH) gene were investigated by single strand conformation polymorphism (SSCP) analysis of seven amplified fragments covering almost the entire gene (2.7 kb). SSCPs were detected in four of these fragments and a total of six polymorphisms were found in a sample of 128 Holstein bulls. Two polymorphisms, a T-->C transition in the third intron (designated GH4.1) and an A-->C transversion in the fifth exon (designated GH6.2), were shown to be associated with milk production traits. GH4.1c/GH4.1c bulls had higher milk yield than GH4.1c/GH4.1t (P < or = 0.005) and GH4.1t/GH4.1t (P < or = 0.0022) bulls. GH4.1c/GH4.1c bulls had higher kg fat (P < or = 0.0076) and protein (P < or = 0.0018) than GH4.1c/GH4.1t bulls. Similar effects on milk production traits with the GH6.2 polymorphism were observed with the GH6.2a allele being the favorable allele. The average effects of the gene substitution for GH4.1 and GH6.2 are similar, with +/-300 kg for milk yield, +/-8 kg for fat content and +/-7 kg for protein content per lactation. The positive association of GH4.1c and GH6.2a with milk production traits may be useful for improving milk performance in dairy cattle.

Effects of selenium and vitamin E administration during a late stage of pregnancy on colostrum and milk production in dairy cows, and on passive immunity and growth of their offspring

OBJECTIVE

To determine effects of selenium (Se) and vitamin E (VE) administration in late pregnancy on Se status, plasma immunoglobulin concentrations, and colostrum and milk production of dairy cows, and on Se status, passive immunity, and growth of their offspring.

ANIMALS

25 Holstein cows and their offspring.

PROCEDURE

3 and 1.5 weeks before calving, sodium selenite (5 mg/100 kg of body weight) and d,l-alpha-tocopheryl acetate (25 IU/100 kg) were administered to 13 cows. The other 12 cows were not treated. Se status was assessed by measurement of glutathione peroxidase activity of erythrocytes (GSH-Px-E).

RESULTS

The 13 treated cows had higher (P < 0.01) GSH-Px-E values at calving and during the first 12 weeks of lactation. Changes in plasma immunoglobulin concentrations before or after calving did not differ between the 2 groups of cows. During the first 36 hours after calving (4 milkings), treated cows produced 22% more colostrum than did their nontreated counterparts (P < 0.005). Percentages of colostral immunoglobulins did not differ between the 2 groups. During the first 12 weeks of lactation, treated cows produced 10% more milk than did nontreated cows (P < 0.005). GSH-Px-E values at birth and 28 days of life were significantly higher in calves from treated cows. Plasma immunoglobulin concentrations and body weight during the first 56 days after birth did not differ between calves born to treated or nontreated cows.

CONCLUSIONS AND CLINICAL RELEVANCE

Cows given Se and VE in late pregnancy produce large quantities of colostrum and milk. Colostrum produced from cows given Se and VE is suitable to feed newborn calves and to be stored for later use. Improvement of Se status in calves born to cows given Se and VE in late pregnancy is not beneficial to passive immunity and growth.

Production of active bovine tracheal antimicrobial peptide in milk of transgenic mice

Tracheal antimicrobial peptide (TAP) is a member of the beta-defensin family of antibiotic peptides found in the tracheal mucosa of the cow. TAP gene expression in the bovine airway is inducible by lipopolysaccharide and inflammatory mediators, suggesting that it functions to protect the upper airway from infection. Limited availability of bovine TAP (bTAP) has precluded investigation of its potential utility in agriculture and medicine. To overcome this problem, transgenic mice expressing bTAP using an expression vector driven by control sequences from the murine whey acidic protein (WAP) gene have been generated. The WAP/bTAP transcript was detected in RNA isolated from mammary tissue of transgenic females. bTAP was purified to homogeneity from milk via acid precipitation, reverse-phase HPLC, and ion-exchange chromatography. This milk-derived bTAP had antimicrobial activity against Escherichia coli. Amino-terminal peptide sequencing confirmed the identity of this material as a bTAP isoform. bTAP available from a mammary gland bioreactor will allow evaluation of bTAP for use as an antibiotic in agriculture and medicine.

Cadmium uptake by Caco-2 cells. Effect of some milk components

The effect of some milk components on the cellular uptake of cadmium has been studied using a human intestinal cell line (Caco-2). Cadmium uptake by Caco-2 cells increased with the concentration of this metal in the culture medium, in a saturable way. These cells were exposed to different concentrations of cadmium and the synthesis of metallothionein was studied by a cadmium-saturation method. The levels of metallothionein increased with the cadmium concentration in the medium up to 20 microM of metal. Supplementation of the culture medium with 10% bovine milk caused a 25% decrease in the uptake of cadmium with respect to that internalized by the cells maintained in the culture medium alone. However, the uptake of cadmium from the medium supplemented with 10% human milk was similar to that with serum-free medium. beta-Lactoglobulin interacted with cadmium when studied by equilibrium dialysis, showing a stoichiometric binding constant of 5 x 10(4) l/mol. Interaction of lactoferrin with cadmium, however, was negligible. When Caco-2 cells were incubated in culture medium containing lactoferrin, cadmium uptake decreased with respect to that observed incubating the cells in a medium containing beta-lactoglobulin or in the free-protein medium. The inhibitory effect of lactoferrin on the uptake of cadmium might be due to a reduction of the cell surface charge, through its binding to the membrane.

Effects of vitamin E on mammary and blood leukocyte function, with emphasis on chemotaxis, in periparturient dairy cows

OBJECTIVE

To determine the effect of vitamin E supplementation on the immune system of dairy cows.

DESIGN

The following immune parameters were followed: production of chemotactic factors and superoxide by mammary macrophages and chemotactic responsiveness of blood neutrophils.

ANIMALS

16 healthy Holstein dairy cows.

PROCEDURE

Dairy cows were assigned to 1 of 2 experimental groups: control (no vitamin E supplementation) and vitamin E supplemented. Supplementation of vitamin E started 4 weeks before and continued up to 8 weeks after parturition, and included oral supplementation of vitamin E at the rate of 3,000 IU/cow/d. In addition, the same group of cows received 1 injection of vitamin E (5,000 IU) 1 week prior to the expected date of parturition. Blood samples were collected weekly throughout the experimental period.

RESULTS

Vitamin E supplementation enhanced by 30 to 83% (P < 0.05) chemotactic responsiveness of blood neutrophils beginning 2 weeks before to 4 weeks after parturition, compared with controls. There were no differences in production of superoxide or chemotactic factors by mammary macrophages between control and vitamin E-supplemented cows.

CONCLUSIONS

Vitamin E supplementation prevents the periparturient inhibition of neutrophil chemotaxis. It is unlikely that vitamin E affects directly the function of mammary macrophages.

Role of milk fractions, serum, and divalent cations in protection of mammary epithelial cells of cows against damage by Staphylococcus aureus toxins

OBJECTIVE

To determine the effect of milk and blood serum constituents on cytotoxicity of Staphylococcus aureus on mammary epithelial cells.

DESIGN

In vitro incubation of cells with cytotoxic agents and milk and serum constituents.

SAMPLE POPULATION

Mammary cells, milk, and blood obtained from 3 cows.

PROCEDURE

Staphylococcal alpha-toxin and culture supernatants from S aureus M60 and an alpha-toxin-negative mutant of M60 were incubated with bovine mammary epithelial cells in the presence of milk fractions, serum, and divalent cations. Propidium iodide fluorescence was used as a measure of cell damage.

RESULTS

Skim milk and milk whey inhibited S aureus cytotoxic agents. Skim milk protected against alpha-toxin damage to a greater extent than milk whey. Serum from an adult animal was more protective than was fetal serum. Milk fat and serum albumin had no protective effect. Divalent calcium and Mg2+ were more effective inhibitors of mammary epithelial cell damage caused by alpha-toxin than of damage attributable to M60 culture supernatant. Divalent calcium and Mg2+ at concentrations similar to those of free Ca2+ and Mg2+ in normal bovine milk decreased cytotoxic damage attributable to alpha-toxin. However, concentrations similar to those of total Ca2+ and Mg2+ in normal milk were required to decrease cell damage caused by M60 culture supernatant. The alpha-toxin-negative mutant was less cytotoxic than the M60 parent strain.

CONCLUSIONS

Casein, as well as Ca2+ and Mg2+ in bovine milk, inhibit the cytotoxic effect of S aureus on mammary epithelial cells.

Modulation of proliferation, second messenger levels, and morphotype expression of the rat intestinal epithelial cell line IEC-6 by fermented milk

Trophic effects of milk fermented with Lactobacillus helveticus, Lactobacillus paracasei ssp. paracasei, Bifidobacterium sp., or the combination of Lactobacillus bulgaricus and Streptococcus thermophilus (yogurt) were studied on the IEC-6 intestinal epithelial cell line. Incorporation of [methyl-3H]thymidine, mitochondrial dehydrogenase activities, cyclic AMP production, and differentiation of levels of the IEC-6 strain were evaluated between the 15th and 30th passage in culture. All fermented and unfermented milks enhanced trophic responses of IEC-6 cells in a dose-dependent manner. Compared with the corresponding milks, supernatant fractions were more effective in stimulating mitochondrial dehydrogenase response. Fermented milk supernatants were also more effective than the corresponding unfermented fractions. Increases in DNA synthesis and cyclic AMP confirmed the activation observed with mitochondrial dehydrogenase. Yogurt induced the more trophic response with an increased number of the more differentiated cell morphotype. Fermentation with L. casei also demonstrated an important trophic adaptation of IEC-6 cells. Milk processing by lactic acid bacteria enhanced trophic and proliferation responses of intestinal epithelial cell line IEC-6. These results suggested that IEC-6 cells could represent an accurate and easy in vitro model for testing the trophic quality of various nutrients and for an optimization of physiological digestive functions.

Detection of clinical mastitis by changes in electrical conductivity of foremilk before visible changes in milk

Mastitis was induced by the direct infusion of Staphylococcus aureus or Streptococcus uberis into the mammary gland of lactating cows. Changes in electrical conductivity of foremilk indicated the establishment of bacteria, increased SCC, increased clotting of milk, and, hence, disease, in advance of visible changes in the milk that could be diagnosed by a herdsperson. Clinical mastitis was detectable by changes in electrical conductivity of foremilk, 90% of cases were detectable when clots first appeared in foremilk, and 55% of cases were detectable up to 2 milkings prior to the appearance of clots. All subclinical infections from Staph. aureus were detected, but subclinical infections from Strep. uberis were not detected. The results suggested that clinical mastitis caused by these two major pathogens could be detected earlier by measuring changes in electrical conductivity of milk than by waiting for a herdsperson to detect visible changes in milk. Earlier detection would permit earlier treatment. However, the handheld sensor used in this experiment is impractical for commercial application, and reliable automated sensors and decision-making algorithms are required.

Does the male reproductive performance depend on the early lactation milk in rats?

This study investigated the role of the early lactation milk (ELM) on the male reproductive performance and the participation of GnRH on this effect in Wistar rats. Newborn males were divided into three experimental groups: 1) ELM-deprived pups, 2) ELM-deprived pups treated with exogenous GnRH 1, 7, 25, and 31 h after birth, and 3) non-ELM-deprived and without exogenous GnRH. In relation to the other two groups, the ELM-deprived male rats exhibited as adults: reduced fertility, decreased weight of both vas deferens and seminal vesicle, and reduced levels of fructose in the seminal vesicle and prostate gland. We suggest that the intake of ELM during the neonatal period is important to the later sexual development of rats, and that GnRH is somehow involved in such an effect.

The effect of mammary gland expression of human lysozyme on the properties of milk from transgenic mice

Transgenic mice were used as model systems to evaluate the impact of human lysozyme expression in the mammary gland. We previously generated two lines of transgenic mice that express human lysozyme mRNA in the mammary gland under the tissue-specific and developmentally correct control of the bovine gene promoter for alpha s1-casein. Concentrations of human lysozyme protein in milk of transgenic mice varied from .25 to .71 micrograms/microliters of milk. Human lysozyme secreted into mouse milk retained its antimicrobial activity, as determined by a denaturing polyacrylamide gel activity assay. The physical and functional properties of the milk were also altered, because mouse milk containing human lysozyme had a 35% decrease in rennet clotting time, a smaller median micelle size (157 nm vs. 172 nm), and a 2.5- to 3-fold greater gel strength than control milk. From these results, we conclude that the use of transgenic animals producing lysozyme in the milk is feasible and potentially useful to the dairy industry.

Nutrient-independent and nutrient-dependent factors stimulate protein synthesis in colostrum-fed newborn pigs

We hypothesized that nonnutrient components, including growth factors, present in colostrum contribute to the stimulation of protein synthesis in colostrum-fed neonatal pigs. We studied neonatal pigs fed mature milk, colostrum, or a formula containing a macronutrient composition comparable to that of colostrum for 24 h. We measured the circulating concentrations of insulin, insulin-like growth factor I, glucose, and amino acids at intervals throughout the 24-h period, after which we measured in vivo protein synthesis using a flooding dose of [3H]phenylalanine. The rates of protein synthesis in several tissues measured after 24 h of feeding were greater than those we reported previously after 6 h of feeding. The acute (within 6 h) stimulation of protein synthesis in visceral and skeletal muscle tissues of neonatal pigs fed milk, colostrum, or formula was primarily influenced by nutrient intake and associated with rapid secretion of insulin. Indirect evidence suggests that intestinal absorption of ingested colostral insulin was minimal. However, the sustained increase in tissue protein synthesis between 6 and 24 h coincided with an increase in circulating insulin-like growth factor I. We found a novel, specific stimulation of skeletal muscle and jejunal protein synthesis in colostrum-fed pigs that can be attributed to some nonnutrient component of colostrum.

Involution of mouse mammary glands in whole organ culture: a model for studying programmed cell death

The DNA fragmentation and gene expression patterns of involuting mouse mammary glands were compared to mammary glands in whole organ culture induced to involute by the withdrawal of lactogenic hormones. Non-random DNA degradation was observed both in vivo and in vitro, indicating that the withdrawal of lactogenic hormones triggers a program of epithelial cell death. Similar patterns of gene expression for the milk protein beta-casein and the apoptosis associated factors TGF-beta 1, TGF-beta 2 and TGF-beta 3 were observed in vivo and in vitro. These results indicate that the withdrawal of lactogenic hormones is responsible for decreased milk synthesis, epithelial cell death and tissue restructuring and that whole organ culture of mouse mammary glands is a useful model for studying the molecular events involved in these processes during involution.

Effects of milk and food on the absorption of enoxacin

The effects of milk and a standard breakfast on the oral absorption of enoxacin were evaluated in eight healthy volunteers in a randomized, balanced, four-way crossover study. After an overnight fast, 400 mg enoxacin was given with water, milk, a breakfast or with a breakfast and milk. The extent of enoxacin absorption was not affected by any of the three treatments, and no statistically significant changes were found with respect to peak plasma enoxacin concentration or time to peak. We conclude that enoxacin can be taken together with food and dairy products.

Use of HT-29, a cultured human colon cancer cell line, to study the effect of fermented milks on colon cancer cell growth and differentiation

Epidemiological and in vivo and in vitro experimental studies have suggested that fermented milks may interfere with the emergence and/or the development of colon cancer. The results, however, remain inconclusive. This prompted us to develop a new approach based on the use of HT-29, a cultured human colon cancer cell line, to study at the cellular level the effect of fermented milks on colon cancer cell growth and differentiation characteristics. Undifferentiated HT-29 cells have been grown in the continuous presence of milks fermented by one of the following bacterial populations: Lactobacillus helveticus, Bifidobacterium, L.acidophilus or a mix of Streptococcus thermophilus and L. bulgaricus. Penicillin G was added to the cell culture medium, resulting in a complete blockade of bacterial growth without significant effect on bacterial viability. One out of the four bacteria species studied, namely L.acidophilus, was without effect on both cell growth and differentiation. The three other bacterial strains induced a significant, although variable, reduction in the growth rate of HT-29 cells, which resulted in a 10-50% decrease in the cell number at steady-state (i.e. at cell confluency). The most efficient strains in lowering the HT-29 growth rate were L. helveticus and Bifidobacterium. Concomitantly, the specific activities of dipeptidyl peptidase IV (DPP IV), a sensitive and specific marker of HT-29 cell differentiation, and that of three other brush border enzymes (sucrase, aminopeptidase N and alkaline phosphatase) were significantly increased, thus suggesting that these cells may have entered a differentiation process. Altogether, these results indicate that the use of cultured colon cancer cells may be a useful tool to further study the effect of fermented milks on colon cancer and that bacterial strains may exert a different and specific effect on cancer cell growth and differentiation when used in fermented milk products.

Inhibitory effect of dairy products on the mutagenicities of chemicals and dietary mutagens

The antimutagenic effects of uninoculated milk and milks cultured with Bifidobacterium or Lactobacillus strains towards the mutagenicity induced by two direct mutagens, 4-nitroquinoline N-oxide and 2-nitrofluorene, and three dietary indirect mutagens, aflatoxin B1, benzo(a)pyrene and quercetin, were investigated using the in vitro Salmonella typhimurium test. Each cultured milk sample and control milk had a significant antimutagenic effect, to an extent varying with the mutagen used. Uninoculated milk had a greater inhibitory effect than cultured milks towards dietary indirect mutagens.