Milk processing quality of suckled/milked goats: effects of milk accumulation interval and milking regime.

Milk with a high concentration of fat and casein is required for cheese production, and these components have a major impact for both quality and yield of the curd. Recent observations have shown that suckling can elevate milk fat concentration in goats and our aim was therefore to check the hypothesis that animal welfare and cheese-processing properties of goat milk could be optimised by appropriate management of suckled/milked goats. Twelve Swedish dairy goats were kept together with one kid each in 4 different mixed management-systems (milking combined with partial suckling) in a cross-over design. Two milk accumulation intervals were tested; Short = dams and kids were together for 16 h (T16) and Long = ; dams and kids were together for 8 h (T8 h). In addition, two milking regimes were used; Suckled Before Milking = S and Milked Before Suckling = M. Milk accumulation interval referred to how long dams and kids were separated. The milk yield available for processing (milk offtake), was weighed and analysed from each milking occasion and the suckled milk yield was estimated by a weigh-suckle-weigh method (WSW) in combination with observing the suckling behaviour during the free suckling periods. Milking managements, such as 'suckling before milking (S)', increased milk fat concentration compared to milking before suckling (M) and 'Short accumulation treatments (T16)' gave higher milk fat, casein concentration and individual curd yield (%) compared to the 'Long accumulation treatment (T8)'. The total individual curd yield (g) was the same despite treatment, but the animal welfare was most likely higher in T16 where dams and kids spent more time together.

Milk production and feeding behavior in the camel (Camelus dromedarius) during 4 watering regimens.

Camels survive and produce milk during recurrent prolonged hot and dry periods. The objective was to evaluate how different watering intervals affected milk production and feeding. Eight lactating camels (Camelus dromedarius) were recruited and subjected to 4 watering regimens in a Latin square design experiment performed at Haramaya University in Ethiopia. Each regimen lasted 16 d with 5 d of daily watering between periods: water was offered at 1,315 h once daily (W1); on d 4, 8, 12, and 16 (W4); on d 8 and 16 (W8); and on d 16 (W16). One camel became sick in the second period and its results were excluded. Camels were kept in a pen with minimal shade and a noon temperature of 30.9±0.1°C. They had free access to hay and were offered 2 kg of concentrates 3 times daily. At noon on d 1, 4, 8, 12, and 16, a blood sample was taken from the jugular vein before watering. All calves were kept together in a separate pen. Morning and afternoon calves stimulated milk let-down before the camels were hand-milked, after which the calves suckled, emptying the udder. Camels maintained the milk volume during water deprivation for about 1 wk, but they produced less milk during the second week during W16. Morning milk osmolality increased from 315±3 on d 1 to 333±3 mosm/kg on d 4 during W4 and from 321±3 on d 1 to 342±3 mosm/kg on d 8 during W8. After watering at 1315 h, milk osmolality decreased to 316±3 and 323±3 mosm/kg, respectively, the same afternoon and then increased during recurrent water deprivation to 338±3 (W4) and 347±3 mosm/kg (W8) on d 16, respectively. During W16, osmolality increased from 318±3 to 336±3 mosm/kg during the first 4 d of water deprivation, but during the remaining 12 d the further rise in osmolality was not higher compared with that on d 4. The change in milk osmolality was linearly correlated to plasma osmolality (r=0.8), but milk lactose content did not increase. Contrary to widespread belief, camels did not dilute their milk when dehydrated. Instead milk osmolality increased in parallel to blood osmolality. This study provides further support to earlier observations on camels' adaptation to their environment.

Management of horses with focus on blanketing and clipping practices reported by members of the Swedish and Norwegian equestrian community.

Limited information is available on the extent to which blankets are used on horses and the owners' reasoning behind clipping the horse's coat. Research on the effects of those practices on horse welfare is scarce but results indicate that blanketing and clipping may not be necessary from the horse's perspective and can interfere with the horse's thermoregulatory capacities. Therefore, this survey collected robust, quantitative data on the housing routines and management of horses with focus on blanketing and clipping practices as reported by members of the Swedish and Norwegian equestrian community. Horse owners were approached via an online survey, which was distributed to equestrian organizations and social media. Data from 4,122 Swedish and 2,075 Norwegian respondents were collected, of which 91 and 84% of respondents, respectively, reported using blankets on horses during turnout. Almost all respondents owning warmblood riding horses used blankets outdoors (97% in Sweden and 96% in Norway) whereas owners with Icelandic horses and coldblood riding horses used blankets significantly less ( < 0.05). Blankets were mainly used during rainy, cold, or windy weather conditions and in ambient temperatures of 10°C and below. The horse's coat was clipped by 67% of respondents in Sweden and 35% of Norwegian respondents whereby owners with warmblood horses and horses primarily used for dressage and competition reported clipping the coat most frequently. In contrast to scientific results indicating that recovery time after exercise increases with blankets and that clipped horses have a greater heat loss capacity, only around 50% of respondents agreed to these statements. This indicates that evidence-based information on all aspects of blanketing and clipping has not yet been widely distributed in practice. More research is encouraged, specifically looking at the effect of blankets on sweaty horses being turned out after intense physical exercise and the effect of blankets on social interactions such as mutual grooming. Future efforts should be tailored to disseminate knowledge more efficiently, which can ultimately stimulate thoughtful decision-making by horse owners concerning the use of blankets and clipping the horse's coat.

Housing-related activity in rats: effects on body weight, urinary corticosterone levels, muscle properties and performance.

The cage systems commonly used for housing laboratory rats often result in sedentary and overweight animals, as a consequence of restricted opportunities for physical activity combined with ad libitum feeding. This can have implications both for animal well-being and for the experimental outcome. Physical activity has several known positive effects on health and lifespan, and physical fitness might therefore be incorporated into the animal welfare concept. The aim of this study was to investigate if and how pen housing affects the physical activity and fitness of rats. Thirty-two juvenile male Sprague-Dawley rats were randomly assigned to two different housing systems for a 4-week period. Sixteen rats were kept individually in standard Makrolon type III cages (42x26x18 cm) furnished with black plastic tubes (singly-housed, SI). The remaining rats were kept in groups of eight, housed in large floor pens (150x210 cm), which were furnished with various objects to increase environmental complexity (pen-housed, PH). The body weight gain, and food and water intake of the rats were measured. During weeks 3 or 4, home cage behaviour, urinary cortiosterone/creatinine ratios (CO/CR), and muscle strength on an inclined plane, were measured. Enzyme activities and glycogen content were measured in tissue samples from m. triceps brachii taken after euthanization at the end of the study. There were no significant differences between groups for food and water intake, but PH rats weighed 14% less than SI rats after 4 weeks, and PH rats also had a more diverse behavioural pattern than SI rats. PH rats had significantly higher oxidative capacity (28% more citrate synthase (CS)) and greater glycogen content (28%) in their muscle samples than SI rats. The PH rats performed significantly better on the inclined plane, both in the muscle strength test (mean angle 75+/-0.5 degrees for PH rats and 69+/-0.4 degrees for SI rats) and the endurance strength test (mean time 233+/-22 s for PH rats and 73+/-14 s for SI rats). There was a negative correlation between body weight and results on the inclined plane for the PH rats. There were no significant differences between housing types with respect to CO/CR ratios. In conclusion, the large pen represents an environment that stimulates physical activity and more varied behaviour, which should be beneficial for the welfare of the animal.

Daytime shelter use of individually kept horses during Swedish summer.

In Sweden, no provision for summer shelter to protect horses from heat and insects is required, although access to shelter for horses kept outdoors 24 h during winter is a requirement. This study investigated horses' daytime shelter-seeking behavior in relation to weather conditions and insect activity during a 2-wk period in summer. Eight Warmblood riding horses had access to 2 shelters of different design to test which shelter design is preferred by horses. Furthermore, rectal and skin temperatures and insect-defensive behavior were measured to test whether horses would benefit from the provision of shade. The horses were kept alone in paddocks for 4 d. During 2 d, horses had access to 2 shelters: 1) open shelter with roof and uncovered sides and 2) closed shelter with roof, wind nets on 2 sides, and opaque plastic opposite the entrance. Weather conditions (ambient temperature, relative humidity, solar radiation, wind speed) were recorded every 10 min. The number of insects (flies, mosquitos) was counted from insect traps placed in each shelter and outside. Behavior (shelter use, insect-defensive behavior, locomotion, grazing) was recorded at 5-min intervals between 0900 to 1200 h and 1300 to 1600 h and rectal and skin temperatures were measured at 0800 h, 1200 h, and 1600 h. Data were analyzed with PROC MIXED and GLIMMIX procedure for Generalized Linear Mixed Models. Ambient temperature ranged from 16 to 25°C (average temperature humidity index 65.7 ± 1.4). Five horses preferred the closed shelter and were observed inside up to 2.5 h continuously. Greater wind speed decreased the likelihood of observing horses inside the shelter ( < 0.001), as did lower numbers of flies ( < 0.001). The insect-defensive behaviors, skin shiver and ear flick, were performed less frequently when horses were using the closed shelter ( < 0.001), indicating that they were less disturbed by insects. Thirty-minute shelter use had no effect on rectal and skin temperatures ( > 0.05). Results showed that horses made use of shelters during the summer even when weather conditions were moderate. A shelter with roof and covers on 3 sides was preferred over a shelter with roof only and can reduce insect-defensive behavior.

Effects of feeding frequency and voluntary salt intake on fluid and electrolyte regulation in athletic horses.

The effect of feeding frequency and voluntary sodium intake (VSI) on fluid shifts and plasma aldosterone concentration (PAC) were studied at rest and after exercise in six athletic horses. The horses were fed twice a day (2TD) and six times a day (6TD) for 25 days for each protocol, according to a changeover design. VSI was measured by weighing each horse's salt block daily. Feeding 2TD or 6TD caused no major alterations in fluid shifts, but in the 2TD treatment there was a postprandial increase in plasma protein concentration and osmolality that lasted <1 h. PAC and VSI were not affected by feeding frequency. VSI ranged from 0 to 62 mg x kg body weight-1 x day-1 and caused significant alterations in PAC. At VSI <26 mg x kg body weight-1 x day-1, a diurnal rhythm for PAC was noted. Water intake, fecal concentrations of sodium and potassium, and packed cell volume during exercise were influenced by VSI. The response to exercise did not differ between treatments. In conclusion, VSI, but not feeding frequency, has significant effects on fluid and electrolyte regulation in athletic horses.

Effect of water supply method and flow rate on drinking behavior and fluid balance in horses.

This study investigated three methods of water supply on drinking preference and behavior in six Standardbred geldings (2-9 years, 505+/-9 kg). The water sources were buckets (B), pressure valve (PV), and float valve (FV) bowls. In an initial drinking preference test, PV was tested at three flow rates: 3, 8, and 16 l/min (PV3, PV8, and PV16), and FV at 3 l/min (FV3). Water intake was measured in l and presented as the percentage of the total daily water intake from each of two simultaneously presented alternatives. The intake from PV8 was greater than from both PV3 (72+/-11% vs. 28+/-11%) and PV16 (90+/-4% vs. 10+/-4%). All horses showed a strong preference for B, 98+/-1% of the intake compared to 2+/-1% from PV8. Individual variation in the data gave no significant difference in preference between the two automatic bowls. In the second part of the study, drinking behavior and fluid balance were investigated when the horses drank from FV3, PV8, and B for 7 consecutive days in a changeover design. Despite a tendency for an increase in total daily drinking time from FV3, the daily water intake was significantly lower (43+/-3 ml/kg) than from PV8 (54+/-2 ml/kg) and B (58+/-3 ml/kg). Daily net water gain [intake-(fecal+urinary output)] was only 0.5+/-3 ml/kg with FV3, resulting in a negative fluid balance if insensible losses are included. These results show that the water supply method can affect both drinking behavior and fluid balance in the horse.

Water intake and fluid shifts in horses: effects of hydration status during two exercise tests.

In the present study, the main objective was to study factors affecting postexercise voluntary water intake in horses. Four Standardbred horses (mean +/- s.e. bwt 500 +/- 8 kg) were used to study water intake and effects of altering hydration status before an incremental exercise test (INCR) and a 40 min constant velocity exercise test (CONST) on a treadmill. Exercise was performed during normohydration (N), after dehydration for 24 h (DEH) and after hyperhydration with 12 l water 30 min before exercise (HH). DEH resulted in a bodyweight loss of 3% and there were signs of some fluid uptake prior to exercise in both HH trials. By the end of the INCR, the calculated change in plasma volume (PVcalc) was -13 +/- 1, -21 +/- 1 and -11 +/- 3% in the N, DEH and HH trials, respectively. During the highest exercise velocities a hypotonic shift of fluid was seen in all INCR trials. There was a greater accumulation of plasma lactate (pLA) in HH-than in N-INCR, probably caused by the extra weight to be carried. CONST induced a similar fluid loss (3%) in all trials, but the decrease in PVcalc at the end of exercise was significantly smaller in HH (-7 +/- 2%) than in N (-14 +/- 1%) and DEH (-19 +/- 2%). In DEH-INCR and DEH-CONST, plasma sodium concentration (pNa) was higher than in N until drinking water was offered 1 h postexercise. In the presence of both an increased pNa and a decrease in PVcalc when dehydrated, the horses drank immediately when offered water postexercise. In N-CONST, there was a significant decrease in calculated PVcalc (-10 +/- 2%) but no increase in pNa when water was given and in this trial the horses rehydrated less rapidly. Plasma aldosterone concentration (PAC) had increased to the same magnitude in all trials after about 10 min, irrespective of type of exercise or hydration status. It was concluded that when both an osmotic and hypovolemic thirst stimulus was present, the horses rehydrated more rapidly postexercise.

Changes in plasma atrial natriuretic peptide concentration in exercising horses in relation to hydration status and exercise intensity.

OBJECTIVE: To investigate effects of hydration status and exercise intensity on plasma atrial natriuretic peptide (ANP) concentration in exercising horses. ANIMALS: 4 trained Standardbreds. PROCEDURE: Horses performed a 40-minute exercise test at 65 to 70% maximal heart rate (HRmax; no incline) and a 12-minute test at approximately 90% HRmax (3.5 degrees incline). The 40-minute test was performed with ad libitum access to drinking water (normohydration), after water had been withheld for 24 hours (dehydration), and 30 minutes after 12 L of water at body temperature had been given via nasogastric tube (hyperhydration). The 12-minute test was only performed with normohydrated horses. RESULTS: Plasma ANP concentration was higher toward the end of exercise during hyperhydration than during the other 2 hydration states, and the area under the plasma ANP concentration curve was significantly greater during hyperhydration than during dehydration. The maximal plasma ANP value induced during the 12-minute test was similar to that of the 40-minute test. After the 12-minute test, plasma ANP concentration did not decrease during the first 30 minutes of recovery, whereas after the 40-minute test, plasma ANP concentration decreased by approximately 30% during the same period. CONCLUSIONS: Hydration status can affect plasma ANP concentration in horses during submaximal exercise. Maximal plasma ANP concentration was similar at the 2 exercise intensities studied, but the postexercise return to baseline values differed. CLINICAL RELEVANCE: Changes in hydration status can cause alterations in plasma concentration of ANP, one of the hormones involved in the control of cardiovascular functions during exercise.

Human-animal interactions and animal welfare in conventionally and pen-housed rats.

The main aim of the present study was to explore the significance of large group/greater pen housing (PH) versus standard Makrolon caging (ST) in three behaviour tests related to human-animal interactions in the adult male laboratory rat. The rats' perception of human interaction was tested in three behavioural tests, of which two reflected common practical procedures, capture and restraint, whereas the third was a human approach test in a Y-maze. The rats' anticipatory reactions to handling and the reactions to restraint did not differ between groups, but the ST rats approached a human hand more quickly than did the PH rats (P < 0.01). Although food intake did not differ, ST rats gained more weight (P < 0.01) and had higher total cholesterol values (P < 0.01) than PH rats. In conclusion, this study shows that housing rats in large groups in an enriched environment did not influence their anticipatory reaction to handling in normal handling situations. However, as the PH rats tended to have a longer approach latency than ST rats in the Y-maze there might be underlying differences in appraisal that are not detected in practical situations. In addition, the PH rats weighed less and had lower total cholesterol values than ST rats and their urine corticosterone values were higher. These effects are suggested to be due to higher physical activity in the PH rats, and the implications of this on the animal as a model is discussed.

Report of the Federation of European Laboratory Animal Science Associations Working Group on animal identification.

The primary aim of this report is to assist scientists in selecting more reliable/suitable identification (ID) methods for their studies. This is especially true for genetically altered (GA) animals where individual identification is strictly necessary to link samples, research design and genotype. The aim of this Federation of European Laboratory Animal Science Associations working group was to provide an update of the methods used to identify rodents in different situations and to assess their implications for animal welfare. ID procedures are an indispensable prerequisite for conducting good science but the degree of invasiveness differs between the different methods; therefore, one needs to make a good ethical evaluation of the method chosen. Based on the scientific literature the advantages and disadvantages of various methods have been presented comprehensively and this report is intended as a practical guide for researchers. New upcoming methods have been included next to the traditional techniques. Ideally, an ID method should provide reliable identification, be technically easy to apply and not inflict adverse effects on animals while taking into account the type of research. There is no gold standard method because each situation is unique; however, more studies are needed to better evaluate ID systems and the desirable introduction of new and modern approaches will need to be assessed by detailed scientific evaluation.

Mechanisms of water economy in lactating Ethiopian Somali goats during repeated cycles of intermittent watering.

We investigated the physiological and behavioural strategies by which lactating Ethiopian Somali goats endure repeated periods of water deprivation. The experiment lasted for 32 days and was divided into four periods of 8 days each. Measurements were taken during the first 4 days in each period. Seven does (W1) were watered once daily and seven does (W4) were watered once every 4th day. Rectal temperature was taken at 0800 and 1715 h. Blood samples were taken in the evening and milk samples in the morning. The goats were on pasture between 0900 to 1215 h and 1315 to 1630 h with behaviour recorded every 5 min. The does were supplemented with 300 g of concentrates per head per day. Plasma and milk osmolality were determined by freezing point depression. Plasma total protein was measured on a TS refractometer. Plasma vasopressin concentrations were analysed by radio-immunoassay. The mean daily water intake of W1 was 1897 ml compared with the calculated mean of 1075 ml in W4 (P < 0.001). The mean diurnal variation of the rectal temperature was 3.5°C in both groups. Afternoon rectal temperature in W4 during period 1 was higher than that in the W1 on the days of water deprivation (P < 0.05). With repeated periods, plasma osmolality in W4 increased less over the days of water deprivation. It was 336, 321, 311 and 306 mosm/l on the 4th day at periods 1, 2, 3 and 4, respectively. The corresponding vasopressin concentrations were 10.0, 9.2, 4.2 and 4.4 pmol/l. Total plasma protein concentration during period 1 on days 3 and 4 were higher in W4 than in W1 (P < 0.01). During the subsequent periods, it did not increase more in W4 compared with W1, but it was lower in W4 on the days after watering. W4 milk production decreased by 22% compared with W1 in all periods. With increasing days of water deprivation, the W4 goats spent less time in the sun, grazed shorter time and frequently ate cactus (Opuntia ficus-indica) as compared with W1. Results suggested that dehydrated lactating Ethiopian Somali goats economised on water by diurnal variations of rectal temperature, storing water in the extracellular fluid, by changing behaviour at grazing and by decreasing milk production.

Exercise response, metabolism at rest and digestibility in athletic horses fed high-fat oats.

REASON FOR PERFORMING STUDY: High starch intakes increase the risk for metabolic disorders and therefore alternative feedstuffs are of interest. High-fat oat varieties have a lower starch and higher energy content than regular oats and may therefore be useful in this context. HYPOTHESIS: Feeding high fat oats causes no adverse effects on the response to exercise and that the total amount of oats offered could be reduced compared to feeding with regular oats. METHODS: Twelve Standardbred trotters were fed regular oats (diet C), high-fat oats (F), and a mixture (50:50) of C and F (M), together with haylage (30:70), in a Latin square design trial. High-fat oats replaced regular oats in a 0.9 to 1.0 ratio in diets F and M. On Day 18 in each 21 day experimental period, horses were subjected to a standardised near-maximal treadmill exercise test with collection of blood samples and muscle biopsies before and after exercise. This was followed by a 3 day period of total collection of faeces and urine. RESULTS: There were no significant effects of dietary treatments on bodyweight, heart rate, plasma lactate and glucose, or on muscle glycogen and lactate concentrations following exercise. However, plasma insulin was reduced during exercise on diets F and M compared to diet C. The total tract digestibility of dry matter, fat, protein, NDF and organic matter were higher for diet F than for diet C. CONCLUSION: High-fat oats can replace regular oats in the diet of athletic horses without any adverse effects on metabolism and exercise response. POTENTIAL RELEVANCE: Due to the high energy content and a high digestibility of dietary components in high-fat oats the daily allowance of oats can be reduced and thus the intake of starch.

Effect of temporary food or water deprivation on milk secretion and milk composition in the goat.

When four goats were subjected to total water deprivation for 48 h once in early lactation and once in mid lactation and their voluntary food intake and effects on milk secretion were observed, milk volume decreased and lactose and fat concentration increased during both periods. However, when the goats were then fed the mean of their own food intake at the two previous water deprivation experiments, and were left free access to water, it was found that decreased food consumption had only a minor influence on milk secretion. When six goats were subjected to 48 h of food deprivation and six to 48 h of water deprivation, milk secretion decreased, but the reduction was delayed and of smaller magnitude during water deprivation. During food deprivation lactose concentration decreased and the milk protein and fat increased; the fatty acid composition changed from a greater proportion of short-chain to more long-chain fatty acids. During water deprivation milk fat and lactose concentrations increased, and only after 44 h did a change from short-chain to a larger proportion of long-chain fatty acids become evident. These experiments indicate that not only food intake, but also water intake are concerned with milk production.

Fluid balance in food-deprived lactating goats drinking saline.

Fluid balance was studied in four lactating goats during two 3 week periods, which included 30 h periods of food deprivation. In one period the goats were given 0.9% NaCl to drink, and in the other they were given water. Prior to food deprivation, fluid intake and urinary flow were similar in the two groups, but urinary Na+ excretion was higher in the saline-drinking goats. The plasma renin activity was depressed in saline-drinking goats, while the plasma aldosterone concentration was the same both in saline-drinking and water-drinking animals. Food deprivation depressed fluid intake and urine flow in all goats, but the reduction was more pronounced in goats drinking saline. The urinary Na+ and K+ excretion also decreased, in both groups, as did plasma Na+ concentration and osmolality. The plasma protein concentration increased in both groups, indicating that hypovolaemia had developed. The renin-angiotensin-aldosterone system (r.a.a.s.) became activated in goats drinking water, but not in the group drinking saline. It is suggested that sodium retention may have attenuated the activation of the r.a.a.s. in the latter group. The results of this study show that hyponatraemic hypovolaemia develops during starvation in lactating goats, regardless of the sodium state of the animals. The possibility that the hyponatraemic hypovolaemia is secondary to an impeded Na+ and fluid absorption from the rumen reticulum is discussed.

Effects of a synthetic vasopressin analogue (desmopressin) in pregnant, lactating and anoestral goats.

The effects of the long-acting synthetic vasopressin analogue desmopressin (dose 2 X 2 micrograms day-1 for two days) were investigated in pregnant, lactating and anoestral goats. Urine flow fell and urine osmolality increased in all experiments. However, pregnant goats continued to drink the same volumes of water each day with the result that the ratio of water intake/urine output increased markedly and the plasma osmolality fell. The results support the hypothesis that the regulation of water intake is changed during pregnancy and that pregnant goats have a lowered sensitivity to signals that normally inhibit water consumption. In lactating goats, milk secretion was not affected by desmopressin. The animals did not drink enough to compensate for the water losses in milk and urine, but more than was needed to cover the water losses in the urine. The plasma osmolality decreased slightly. It appears as if the mechanisms involved in the control of water balance are not sufficiently adapted to take water losses via the milk into account, if the animals are subjected to challenges. In anoestral animals, the water balance was maintained during desmopressin injections. The renal sodium excretion did not change, but the renal potassium excretion decreased in pregnant and lactating goats in response to desmopressin.

Fluid absorption from the rumen during rehydration in sheep.

Water movements across the rumen wall were studied during rehydration in four fistulated sheep. The animals were dehydrated for 48 h which increased total plasma protein, plasma osmolality, plasma Na+, arginine vasopressin and plasma renin activity. Two series of experiments were performed: Expt I with no food available during rehydration, and Expt II where the animals were fed hay. On the rehydration day, a fluid marker (cobalt-EDTA) was administered into the rumen. To avoid water outflow from the rumen a stopper was inserted into the reticulo-omasal orifice. When the animals were provided with water they immediately drank 9 l. The water offered contained the same marker concentration (Co2+) as in the rumen liquid. In Expt I, Co2+ concentration increased after drinking, and remained elevated until the stopper was removed. The highest value was obtained after 20 min, and this corresponded to at least a 11 water absorption in individual animals. In Expt II, the sheep immediately started to eat following drinking and the inflow of saliva caused a dilution of the marker. Plasma osmolality and Na+ concentration decreased in both experiments indicating that water absorption occurred in both experiments. Removal of the stopper did not cause any significant changes in the parameters measured. Vasopressin concentration fell immediately on the sight of water, and then continued to decrease. It is concluded that in the sheep, voluntary drinking is followed by an immediate and substantial absorption of water from the rumen.

Water and sodium movements across the ruminal epithelium in fed and food-deprived sheep.

Fluid and electrolyte movements across the ruminal epithelium of sheep were studied using the temporarily isolated rumen technique. The sheep were all subjected to the following treatments: (1) fed sheep (fed twice daily), after rumen emptying, received rumen contents from a fed sheep; (2) food-deprived sheep (two meals were omitted), after rumen emptying, received rumen contents from a food-deprived sheep; (3) fed sheep, after rumen emptying, received rumen contents from a food-deprived sheep; and (4) food-deprived sheep, after rumen emptying, received rumen contents from a fed sheep. Food deprivation led to an increased Na concentration of the rumen fluid while K and Cl concentrations, as well as osmolality, decreased. Plasma Na and osmolality decreased. During the 40 min after the rumen contents were exchanged no net movements of water occurred. Then the sheep were given an intraruminal load of saline which gave rise to a significant net absorption of fluid from the rumens of those sheep which had received rumen contents from fed sheep. The change in composition of the rumen contents after food deprivation impaired the absorption of Na and water from the rumen. Furthermore food deprivation reduced the Na absorptive function of the ruminal epithelium, but not the water permeability.

Fluid balance during heat stress in lactating goats.

Fluid balance and thermoregulation were studied during an acute heat load (maximal daily temperature, 38 +/- 1 degrees C; night temperature 27 +/- 1 degrees C) in six goats during lactation and non-lactation. The goats had free access to water for 1 day, followed by 29.5 h of water deprivation and then water was returned. With water available the goats increased water intake and urinary and milk water losses, while plasma and milk osmolality decreased. Water deprivation caused plasma osmolality and vasopressin concentration to increase most in lactating goats. Milk osmolality rose to values similar to plasma osmolality. Plasma cortisol increased in lactating goats at the end of dehydration. Renal Na+ excretion increased during dehydration in lactating goats. Evaporative heat loss was larger in lactating goats when hydrated, but became less than in non-lactating goats during dehydration. Lactating goats exhibited higher respiratory frequency and rectal temperature than non-lactating goats. In conclusion, our results show that goats increase the water turnover during heat stress if allowed to drink ad libitum, but when they are deprived of water lactating goats reduce water loss in urine, milk and by evaporation, and rectal temperature reaches higher levels than in non-lactating animals. This saving of water could allow milk production to be maintained for a longer time during heat stress.

Fluid balance during food deprivation and after intraruminal loads of water or isotonic saline in lactating and anoestral goats.

A study was made of water and salt balance during a 28 h period of starvation in lactating and anoestral goats. Food deprivation caused diminished water intake in all but one animal, and the secretion of urine and milk gradually decreased. The plasma volume and the glomerular filtration rate were reduced, the plasma Na concentration lowered, and the plasma renin activity and plasma aldosterone concentration raised during starvation. After 28 h without food the goats were given a load of water or saline into the rumen. The fall in the plasma protein concentration that occurred indicates that the plasma volume increased in all animals within 4 h of receiving saline, but was unchanged after the water load. The plasma Na concentration decreased further after the water load, but increased in all animals after the saline load. The plasma renin activity and plasma aldosterone concentration remained elevated after the intraruminal water load, but fell towards basic values after the saline load. The renal Na excretion decreased during food deprivation, and showed no increase within 4 h of saline loading. It appears that only the load of saline restored the salt and water homoeostasis of the animal. Lactating and anoestral goats do not apparently differ in their response to starvation. The effects of starvation on fluid balance seem to become as severe in goats as in monogastric species despite food reservoirs in the reticulo-rumen and omasum at the onset of food deprivation.