Detecting ethanol and acetaldehyde by simple and ultrasensitive fluorimetric methods in compound foods.

There is a need for simple, accurate, and rapid analysis of ethanol (Eth) and acetaldehyde (AA) in a wide variety of beverages and foods. A novel enzymatic assay coupled to formation of fluorescent chromophore is presented. Eth detection was further improved by adding semicarbazide to the reaction mixture, which interacts with AA and prevents its inhibitory effect on Eth oxidation. The limits of detection of Eth (0.5 mg/L) and AA (0.9 mg/L) are comparable with the performance of modern gas chromatography techniques. The repeatability of Eth and AA detection in various foods (9% on average) was lower than that with commercial kits (23%). The high sensitivity of the developed method enables detection of AA in common foods [e.g., bio-yogurt (12.2 mg/L), and the existence of endogenous Eth (1.8 mg/L) and AA (2.0 mg/L) in bacteria-free non-fermented bovine milk], which could not measured so far by enzymatic methods.

Physiological and behavioral basis for the successful adaptation of goats to severe water restriction under hot environmental conditions.

Among domestic ruminants, goats are renowned for their ability to tolerate water deprivation, water restriction and energy restriction. However, some basic questions regarding their ability to endure water restriction under heat stress are still open. Three levels of water restriction (56%, 73% and 87% of the ad libitum) were imposed on 20 cross-bred 3-year-old female goats (75% German Fawn and 25% Hair Goat) distributed into four groups, with five animals per treatment. The experiment was conducted from the beginning of July to the end of August in a farm located in the Eastern Mediterranean region of Turkey (40 m in altitude; 36 59' N, 35 18'E), in which subtropical weather conditions prevail. The average daily temperature during the experiment was 34.2°C, whereas the highest and lowest temperatures were 42°C and 23.1°C, respectively. The average relative humidity was 68.2% and wind speed was 1.2 km/h. Weekly average thermal heat indexes during the experiment were 78.3 (week 1), 79.1 (week 2), 80.1 (weak 3), 79.8 (weak 4), 81.3 (weak 5) and on average 79.7. Feed intake, heart rate, thermoregulatory responses (rectal temperature, respiration rate), blood plasma concentrations of ions (Na, K), antidiuretic hormone (ADH), metabolites (glucose, cholesterol, creatinine and urea) and behavioral aspects (standing, walking, lying) were studied over 30 days. The responses to water restriction were proportional to the level of restriction. The reductions in feed intake (up to 13%), BW (up to 4.6%) and the increases in rectal temperature (0.5°C) and breath rate (10 respirations/min) were moderate and also were far from responses encountered under severe heat and water stresses. The increase in plasma Na (from 119 to 140 mM) and ADH concentrations (from 12.6 to 17.4 pg/ml) indicates that the physiological response to water restriction was in response to mild dehydration, which also explains the increase in blood plasma concentrations of glucose, cholesterol, creatinine and urea. Behavioral responses (reduction in walking from 226 to 209 min/day and increase in lying from 417 to 457 min/day) were associated with conservation of energy or thermoregulation (reducing the exposure to direct radiation).

Effects of intramammary infusions of casein hydrolysate, ethylene glycol-bis(ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and lactose at drying-off on mammary gland involution.

The transition from the lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when involution of mammary glands is completed. Consequently, strategies that accelerate the involution process after drying-off could reduce the incidence of mastitis. The objective of this study was to assess the effect of 3 different treatments on mammary gland involution. Each quarter of 8 Holstein cows in late lactation was randomly assigned at drying-off to an intramammary infusion of casein hydrolysate (CNH; 70 mg), ethylene glycol-bis(ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA; 5.7 g), lactose (5.1g), or saline 0.9% (control) solutions. Milk samples were collected on the last 2 d before and 1, 3, 5, 7, 10, and 14 d after the last milking for determining concentrations of mammary gland involution markers. Lactoferrin, somatic cell counts (SCC), BSA, and Na(+) concentrations, as well as matrix metalloproteinase-2 and matrix metalloproteinase-9 activities gradually increased in mammary secretions during the first 2 wk following the last milking, whereas milk citrate and K(+) concentrations decreased. As involution advanced, the Na(+):K(+) ratio increased, whereas the citrate:lactoferrin ratio decreased. Compared with mammary secretions from control quarters, mammary secretions of quarters infused with CNH had higher SCC on d 1, 3, 5, and 7, and greater BSA concentrations on d 1, 3, and 5. Similarly, the CNH treatment induced a faster increase in lactoferrin concentrations, which were greater than in milk from control quarters on d 3, 5, and 7 after drying-off. Milk citrate concentrations were unaffected by CNH but the citrate:lactoferrin ratio was lower in CNH-treated quarters on d 3 and 5 than in control quarters. Moreover, CNH treatment hastened the increase in Na(+) concentration and in the Na(+):K(+) ratio on d 1. Infusion of CNH also led to an increase in proteolytic activities, with greater matrix metalloproteinase 9 activities on d 1 and 3. The EGTA infusion increased SCC above that of control quarters on d 1 and 3 but it had no effect on the other parameters. Lactose infusion had no effect on any of the involution markers. In this study, intramammary infusions of CNH were the most efficient treatment to accelerate mammary gland involution, suggesting a potential role of CNH as a local milk secretion inhibitor during milk stasis.

Lipopolysaccharide challenge of the mammary gland in cows induces nitrosative stress that impairs milk oxidative stability.

The aim of this work was to study the effects of mastitis induced by intramammary lipopolysaccharide (LPS) challenge on milk oxidative stability, as well as to understand the underlying biochemical processes that cause such changes. LPS challenge was associated with nitric oxide burst from the surrounding mammary epithelial cells and consequently induced nitrosative stress that was induced by the formation of NO2• from nitrite by lactoperoxidase. This response was associated with an ∼3-fold increased formation of hazardous compounds: nitrotyrosines, carbonyls and lipid peroxides. We sustained the involvement of xanthine oxidase as a major source of hydrogen peroxide. In consistent with previous findings, catalase has been shown to play a major role in modulating the nitrosative stress by oxidizing nitrite to nitrate. The current hygienic quality criteria cannot detect mixing of low-quality milk, such as milk with high somatic cells, and nitrite with high-quality milk. Thus, development of an improved quality control methodology may be important for the production of high-quality milk.

Lipopolysaccharide challenge of the mammary gland in bovine induced a transient glandular shift to anaerobic metabolism.

Support of milk production in modern dairy cows demands a large proportion of its own metabolic resources, such as glucose, which might be required under stressful situations. The aim of the experiment was to test the hypothesis that acute immune stress shifts oxidative metabolism to glycolysis. Two mammary quarters in 6 Holstein cows were infused with lipopolysaccharide (LPS), whereas the 2 counter quarters served as controls to the treatment. An additional 6 cows were infused with saline and served as running controls. The LPS challenge induced dramatic transient increases in milk lactate (75-fold) and malate (11-fold) concentrations (both markers of glycolysis) at 24h posttreatment. No significant changes in lactate and malate concentrations were recorded in control quarters and control animals, indicating that the effect of LPS was restricted to the treated gland. The LPS challenge induced a dramatic transient decrease in milk yield, and lactose and citrate (a marker of mitochondrial metabolism) secretion at 24h posttreatment. The kinetics were inversely proportional to those of lactate and malate concentrations. Thus, our data suggest that LPS challenge induces acute conversion of epithelial cell metabolism from principally mitochondrial-oxidative to principally cytosolic (glycolytic), which allows the diversion of metabolic resources normally used to synthesize milk to support the immune system. An in vitro bacterial growth test showed that concentrations of lactate, malate, and lactose equivalent to those found in the in vivo experiment delayed and reduced the growth of a pathogenic Escherichia coli strain, suggesting that they play a role in diminution of bacterial multiplication in the mammary gland.

Concentrations of ganglioside type M1 and immunoglobulin G in colostrum are inversely related to bacterial infection at early lactation in cows.

The levels of IgG and ganglioside type M1 in the colostrum of cows and heifers were analyzed to examine their utility in predicting acquisition of intramammary infection (IMI) during the first weeks postpartum. In general, high levels of IgG and ganglioside type M1 in cows were associated with lower new incidence of IMI, and linear discriminate analysis based on these 2 variables yielded 69.4% successful classification into cows that did or did not acquire new IMI. This analysis was less successful in heifers because a high proportion of them joined the herd when already infected with bacteria in their udders. It is suggested that application of a wider range of measures that reflect the immune status would enable the identification of most cows prone to new IMI.

Expression of albumin in nonhepatic tissues and its synthesis by the bovine mammary gland.

Albumin is a well-characterized product of the liver. In the present study, objectives were to determine if the albumin gene is also expressed in various nonhepatic tissues in the bovine; whether mammary gland epithelial cells synthesize albumin; and how its synthesis is affected by bovine mastitis. Albumin expression was monitored using reverse transcription-polymerase chain reaction. Tissues examined were: liver, mammary gland, tongue, intestine, lymph gland, testicle, ovary, and uterus. All tissues except the ovary expressed the albumin gene, albeit less so than the liver. The highest level of expression (other than liver) was found in the lymph nodes but expression was also found in the mammary gland. Incubation of mammary gland explants with the labeled amino acid L-[(35)S] methionine resulted in formation of labeled immunoprecipitable albumin, newly synthesized in the explant. Immunoprecipitable albumin in the medium verified that newly synthesized albumin was also secreted into the medium. This shows that the gland itself is a source of milk albumin. Albumin mRNA expression was approximately 4 times higher in mammary gland tissue from 6 mastitic cows compared with expression in mammary tissue from 6 healthy glands. Further, secretion of albumin was increased 3.5-fold from explants of mastitic mammary glands compared with secretion from explants of healthy mammary glands. Addition of lipopolysaccharide increased the synthesis and secretion of albumin in mammary gland cells in a dose-dependent manner. Exposure to lipopolysaccharide accelerated albumin synthesis in a time-dependent manner up to 48 h. These results lead us to suggest that the secretion of albumin by the mammary gland is part of the innate nonspecific defense system.

Changes in milk composition as affected by subclinical mastitis in goats.

The mechanism of the effects of subclinical mastitis (SM) at the glandular level in dairy goats on milk yield and its composition as expressed in curd yield (Yc) was studied. Twenty-five Israeli goats of various crossbreeds were chosen; one udder half was naturally infected with identified coagulase-negative staphylococci, and the contralateral gland was free of bacteria. The milk yield of the infected halves was significantly lower than that of the uninfected ones. Somatic cell count and N-acetyl-beta-D-glucosaminidase activity were significantly higher in the infected halves. The lactose concentration in the infected glands was significantly lower than that in the uninfected ones, casein concentrations did not differ, and the whey protein and albumin concentrations were significantly higher in the infected glands. Plasmin activity was significantly higher in the infected glands, whereas plasminogen activity was undetectable. Concentrations of Ca2+ did not differ, whereas Ca2+ activity was significantly lower in the infected glands. The proteose peptone concentration was 1.5 times as great in the infected glands as in the uninfected ones. The Yc was significantly lower in the infected halves, and clotting time was significantly longer. The mechanisms of the effects of SM on milk yield and Yc in goats and sheep are discussed and compared.

Changes in milk composition as affected by subclinical mastitis in sheep.

The mechanism of the effects of glandular-level subclinical mastitis in dairy sheep on milk yield and on its composition as expressed in curd yield was studied. Thirty-six Israeli-Assaf dairy sheep with one udder half infected with identified coagulase-negative staphylococci and the contralateral gland free of bacteria were chosen. The milk yield of the infected halves was significantly lower than that of the uninfected ones (0.36 vs. 0.76 kg/milking). The somatic cell count and N-acetyl-beta-D-glucosaminidase activity were significantly higher in the infected halves than in the uninfected ones. The plasminogen activator and plasmin (PL) activities were significantly higher in the infected glands than in the uninfected ones, whereas plasminogen (PLG) activity and the ratio PLG:PL were significantly lower in the infected glands. Concentrations of Ca2+ did not differ, whereas Ca2+ activity was significantly lower and proteose peptone concentration was 2.4 times as high in the infected glands than in the uninfected ones. Curd yield was significantly lower in the infected glands than in the uninfected ones.

Infusions of casein hydrolyzates into the mammary gland disrupt tight junction integrity and induce involution in cows.

Milk stasis triggers local stimuli, which make the tight junctions leak and trigger involution. The aim of the study was to test the hypothesis that casein hydrolyzates compromise tight junction integrity and dry-off milk secretion in dairy cows. Six repeated doses of casein hydrolyzates after each milking during 3 d caused drastic changes in mammary secretion and composition, which were associated with irreversible cessation of milk secretion. No such changes were recorded in the control glands that had been treated with nonhydrolyzed casein. Treatment with casein hydrolyzates disturbed tight junction integrity within 8 h (as indicated by changes in Na+ and K+ concentrations), reduced the concentrations of lactose precipitously, activated the plasmin activator-plasminogen-plasmin system, and induced the secretion of immunoglobulin type G and lactoferrin. At the end of the 3-d treatments, we stopped milking the experimental and control glands. Milk composition 19 d later was similar in the experimental and control glands and was consistent with the composition expected in fully involuted glands. We conclude that casein hydrolyzates are among the milk-borne factors that cause the disruption of tight junction integrity and induce involution in cows. The process induced by casein hydrolyzate was more rapid and synchronized than the involution induced at drying-off.

Interrelationships among ambient temperature, day length, and milk yield in dairy cows under a Mediterranean climate.

We examined the effect of calving month (CM) on the production of milk and milk protein by Israeli Holstein dairy cows located in the main climatic zone of Israel during their third and fourth lactations, and found it to be significant. Cows that calved in December produced the highest milk and milk protein yields, and those that calved in June produced the lowest, 92.8% of the maximum. The combined effect of the environmental average temperature and day length accounted for 0.96 of the variability in average milk production during lactation and 0.93 of that in average protein production during lactation. Average milk production was reduced by 0.38 kg/degree C and average protein production was reduced by 0.01 kg/degree C. Elongation of daylight increased average milk production by 1.2 kg/h and average protein production by 0.02 kg/h of daylight. Analysis of the temperature pattern effect on milk and protein yield during lactation indicated that cows at the second month (the pike of their milk yield) are more vulnerable to the negative temperature effect than cows on the ninth month of lactation.

Effect of polyethylene glycol on rumen volume and retention time of liquid and particulate matter along the digestive tract in goats fed tannin-rich carob leaves (Ceratonia siliqua).

The present work studied the effects of tannins in carob leaves (CL) on rumen volume and kinetics, and on the retention time of fluid and particulate components of the digesta along the gastrointestinal tract (GIT) in goats. The experimental design was a two factor crossover experiment, i.e. in phase 1, two goats were fed CL and 2 CL and polyethylene glycol (PEG) and in phase 2, the treatments were switched. The main effects of tannins were depression of the rumen fluid and particulate content of the rumen, acceleration of the passage of liquid from the abomasum, and delay of the passage of digesta in the intestine. The overall effect was a delay in the passage of fluid and particulate matter throughout the entire GIT. It is hypothesised that these responses are largely the consequence of the interaction of tannins with digestive enzymes and the epithelium lining of the digestive tract.

Adrenocorticotrophic hormone and dexamethasone failed to affect milk yield in dairy goats: comparative aspects.

The ability of adrenocorticotrophic hormone (ACTH; single i.v. injection of 2.5IU/kg BW) and dexamethasone (single i.m. injection of 36mg/kg BW) to affect milk production was studied in mid-lactating Israeli Saanen goats. None of these treatments produced changes in milk yield and composition of the goats. The effects of ACTH on blood cortisol levels, and the effects of ACTH and dexamethasone on blood plasma concentrations of glucose, however, were consistent with previous reports in goats and cows. These responses suggest that ACTH and dexamethasone treatments produced their expected glucocorticoid effects. It is suggested that obstructing the axis: stress-ACTH-glucocorticoid-down regulation of milk yield, which was demonstrated in dairy cows, reflects the adaptation of goats to harsh conditions, and the selection pressure to produce milk under conditions which are considered stressful for other ruminants.

Stress down regulates milk yield in cows by plasmin induced beta-casein product that blocks K+ channels on the apical membranes.

Stress and stress related hormones such as glucocorticoids inhibit lactation in cows. In the present study we propose a novel mechanism connecting stress with plasminogen-plasmin system (PPS) (an enzymatic mechanism in milk, which leads to the breakdown of the major milk protein casein). We show that stress activates the PPS leading to an increase in plasmin activity, and that a distinct plasmin-induced beta-casein breakdown product (fraction 1-28) is a potent blocker of potassium channels in mammary epithelia apical membranes. The reduction in milk production due to dehydration stress or glucocorticoid (dexamethsone) was correlated with the activities of plasmin and channel blocking activity in the milk of the tested cows. The notion that the axis Stress-PPS-beta-casein fraction 1-28 is responsible for the reduction in milk yield is supported by the results of experiments showing that injecting solution composed of casein digest enriched with beta-casein fraction 1-28 to the udder lumen leads to a transient reduction in milk production. Furthermore, injecting a pure beta-casein fraction 1-28 to the udder lumen of goat's lead also to a transient reduction in milk production with kinetics that was similar to the kinetics observed in cows.

Short-term changes in eating patterns explain the effects of condensed tannins on feed intake in heifers.

Ingestion of condensed tannins decreases feed intake in ruminants. Polyethylene glycol (PEG) forms high-affinity complexes with tannins. In two experiments carried out on Holstein heifers, quebracho (Q) from the Aspidosperma quebracho served as source of condensed tannins. The aims of the study were (i) to quantify the effect of Q on feed intake and eating behaviour in cattle fed complete mixed diets (CMDs); (ii) to clarify if changes induced in ingestive behaviour and feed intake by Q in cattle can be reversed by feeding PEG; and (iii) to clarify if the decrease in feed intake is associated with short-term (astringency, post-ingestive malaise) or longer-term effects. In experiment 1, 500 g/day of Q was found to be the minimal dose that decreased feed intake in heifers. A ratio of PEG:Q equal to 1:12.5 did not fully restore feed intake. In experiment 2, four heifers received a random sequence of four rations in a Latin-square design with feeding cycles of ca. 7 days: CMD containing no supplements (C), or supplemented with 625 g/day of Q without PEG (Q), with 625 g/day of Q and 250 g/day of PEG (Q-PEG), or with 250 g/day of PEG without Q (PEG). Individual rations were continuously weighed in the trough and the behaviour of heifers was observed for 180 min after distribution of CMD. Overall, feeding Q was associated with lowered feed intake and shorter duration of eating bouts, mainly of the first eating bout, immediately after distribution of the diet. A larger portion of the diet was consumed subsequent to 180 min after distribution in Q-fed heifers. Eating rate and the water to food ratio were not affected by Q. The effects of Q on feed intake were attenuated by feeding PEG. Heifers adapted effectively to condensed tannins by increasing the number of eating bouts and the portion of diet consumed subsequent to 180 min after distribution, so that no differences in feed intake were noted on the last day of each feeding cycle. Data are interpreted to show that: (i) negative effects of Q on feed intake derive from astringency of CT and short-term post-ingestive malaise; (ii) the increased number of eating bouts and their wider partition throughout the day are means to preserve the ruminal environment in Q-fed heifers; (iii) PEG has the potential to neutralize negative effects of condensed tannins in cattle.

Preferences for foods varying in macronutrients and tannins by lambs supplemented with polyethylene glycol.

Supplemental polyethylene glycol (PEG) increases intake when animals eat foods high in tannins, but little is known about how PEG affects preference for foods that vary in concentrations of macronutrients and tannin. We investigated how varying macronutrients and tannins (commercially available extracts from quebracho trees) affected food intake, and we assessed the degree to which PEG (MW 3350) affected intake of tannin-rich foods by sheep. From 0715 to 1800 daily, lambs were offered diets that varied in concentrations of macronutrients: high energy/low protein (75% barley/25% alfalfa), medium energy/medium protein (35% barley/65% alfalfa), and low energy/high protein (100% alfalfa). Preference for these diets was determined in the absence of tannin, and then, in Trials 1 to 3, tannin was added in increasing concentrations (from 5 to 20%) to the diets with high and medium levels of energy. In Trial 4, tannin (10%) also was added to the low-energy diet. Lambs were supplemented with either 50 g of PEG mixed with 50 g of ground barley or 50 g of ground barley alone from 0700 to 1715 daily; lambs always consumed all of these supplements. In the absence of added tannins, all lambs preferred high energy/low protein > medium energy/medium protein > low energy/high protein. As tannin levels increased, preference for the high- and medium-energy foods decreased, and all lambs preferred foods that were lower in tannins and higher in protein. Lambs supplemented with PEG ate more macronutrients and tannins than unsupplemented lambs, and the effect became increasingly apparent as tannin levels increased from Trials 1 to 4. We conclude that the effectiveness of supplemental PEG may be low if alternative forages are equal or superior in nutritional quality and contain fewer metabolites with adverse effects. In such cases, animals would likely prefer alternatives to high-tannin foods.

Self-regulation of intake of polyethylene glycol by sheep fed diets varying in tannin concentrations.

Tannins occur in many plant species, and they often suppress intake by reducing nutrient availability or by causing malaise. Polyethylene glycol (PEG) binds to tannins and may thereby increase the availability of macronutrients and decrease malaise. Supplemental PEG increases intake of tannin-containing plants by sheep, goats, and cattle. Given the strong response to supplemental PEG, we speculated that animals might self-regulate their intake of PEG when offered foods high in tannins. The objective of the first experiment was to determine if the amount of supplemental PEG (0, 25, 50, 75, or 100 g; molecular weight, 3,350) affected intake by lambs of a food (milo-tannin mix) containing 20% quebracho tannin. There was a linear relationship (Y = 272 + 1.2X; R2 = .86; P = .023) between the amount of supplemental PEG ingested and the subsequent intake of milo-tannin food by lambs. The objective of the second experiment was to determine whether lambs self-regulated intake of PEG when fed a ration that contained 0, 5, 10, 15, or 20% quebracho tannin and whether they adjusted their intake of PEG when tannin was removed from the diet. There was a positive relationship between the amount of PEG ingested and intake of food and tannin (P = .0001). Lambs fed high-tannin diets ate more PEG than controls (P = .03). Lambs fed the 20% tannin diet ate the most PEG, and controls ate the least PEG. Tannin limited intake of the diets, but PEG attenuated the response to a great degree (P = .065). Immediately after tannin was removed from the ration, lambs that formerly had been fed the 20% tannin ration ate more PEG than lambs fed the other rations (P = .0075). Ten of the lambs (5 from the 20% tannin group, 1 from the 15% tannin, and 2 each from the 10 and 5% groups) continued to eat PEG for 7 d after tannin was removed from their ration. When they were tested again 6 wk after the trial and offered tannin-free diets, their intake of PEG had decreased.

Stunting syndrome in broilers: effect of electrolytes in drinking water on performance and intestinal glucose transport.

Posthatched naive or inoculated male broiler chicks were kept in separate rooms. An inoculum was prepared from intestines of stunting-syndrome affected broiler chicks. Tap water was supplied from 2 L cups, 1 cup per pen. In the Ist experiment, the naive chicks were provided with tap water only and the inoculated ones had free access to tap water or to an electrolyte solution. In the 2nd experiment, the naive and inoculated birds had free access to water in addition to an electrolyte solution. Supplementation was provided up to 3 weeks of age; thereafter all chicks had access to tap water only. Water or electrolyte consumption and body weight (BW) were determined. Total water intake of inoculated chicks was higher than that of naive counterparts (P<0.001). Electrolyte supplementation increased drinking (P<0.001) in inoculated birds more than in naive ones. At 1 week old the weight of the inoculated birds was about 64% of the weight of naive ones; at the age of 4 and 6 weeks it was about 74% and 86% respectively. Compensatory growth was most apparent in the inoculated chicks provided with electrolyte solution. At the age of 6 weeks, the latter exceeded the BW of the exclusively water supplied counterparts by 327 g. Electrolyte supplementation up to the age of 3 weeks had no effect on the naive counterparts. Osmolality was reduced slightly, but very significantly by inoculation; electrolyte supply had no effect on this variable. Sodium concentration in the plasma was higher in the inoculated birds. Plasma albumin was markedly reduced by inoculation on weeks 1 and 2. Whereas the inoculated chicks supplied with electrolytes resumed the level plasma albumin level of the naive chicks on week 3, an over-compensation occurred in the inoculated-water-supplied (IW) group, and they surpassed the naive chicks significantly. Blood hematocrit increased significantly with age; inoculation, age and/or electrolyte supplementation had no effect on this variable. Sodium-dependent glucose transport rates were enhanced in vesicles obtained from inoculated chicks as compared to naive ones. While electrolyte supplementation had no effect on glucose active transport in naive chicks, electrolyte supplementation decreased rates of glucose active transport in inoculated ones. These data demonstrate that electrolyte supplementation during the early age may be used to enhance the tolerance of broiler chicks to stunting-syndrome by improving food and water consumption, and subsequently growth rate during and after cessation of electrolyte supply.

Metabolic and productive responses of dairy cows to increased ion supplementation at early lactation in warm weather.

We found previously that the current recommendations for Na+, K+, and Cl- contents in the diet do not meet the needs of lactating cows. The response of cows receiving a ration with increased amounts of Na+, K+, and Cl- (E cows) were compared with those of cows consuming the same ration with a fixed concentration of these ions (C cows) between weeks 2 and 8 post partum (PP). Milk, protein, fat and lactose yields, and dry matter intake between weeks 2 and 4 PP were higher in E than in C cows. These differences did not occur between weeks 4 and 8 PP, mainly because of a higher incidence of PP complications in E cows. A greater increase in plasma insulin-like growth factor-1 concentration in E than in C animals during weeks 2 and 3 PP was consistent with the milk responses. A reduction in aldosterone concentration in E cows in weeks 2 and 3 PP was a consequence of their Na+ requirements being satisfied as a result of their enhanced Na+ intake. A subsequent elevation in aldosterone concentration in E animals was probably related to a moderate excess in K+ intake. This increase in aldosterone explains the urinary potassium loss that was detected at week 6 PP. The absence of differences between E and C cows in plasma renin activity was consistent with an absence of differences in urine volume and with the apparent utilization of the enhanced ion intake for body functions.

Metabolism of water, sodium, potassium, and chlorine by high yielding dairy cows at the onset of lactation.

We studied the balance of Na+, K+, Cl-, and water in six high yielding (> 39 kg/d of milk) cows between wk 2 to 1 prepartum and at 2 and 7 wk postpartum during winter in Israel. Cows were fed complete diets; Na+ and Cl- contents exceeded dietary recommendations, and K+ content was equal to dietary recommendations. Milk yield was related positively and significantly to retention of Cl- and K+, indicating that ions that are the main constituents of sweat can limit the ability of cows to express full genetic potential. The highest ion retention was recorded for cows that had the highest dry matter intake and, hence, the highest ion intake. Retention of Cl- was highest for cows that were most efficient in retaining Cl- in the kidney. In hot climates, increasing the concentrations of ions in the diet of early lactation cows according to the actual dry matter intake could prevent or reduce the severity of ion deficiencies. Water turnover rate of the cows was dependent on dry matter intake, milk yield, and respiratory-cutaneous water loss. The milk-free water balance (water turnover rate minus water secreted in milk) could be very efficiently predicted for lactating and nonlactating cows by the following equation: milk-free water balance (kilograms per day) = digestible energy intake (megacalories per day) x 0.58 + respiratory-cutaneous loss (kilograms per day) x 0.97 (n = 18; R2 = 0.97). This formula provides a tool to assess the evaporative-cutaneous water loss from feed and water intake measurements to evaluate the severity of heat stress.