Effects of high salt diets and taurine on the development of hypertension in the stroke-prone spontaneously hypertensive rat

Summary. Taurine is present in high concentrations in mammalian tissues and has been implicated in cardiovascular control mechanisms. The aim of the present study was to evaluate the ability of taurine to attenuate salt-induced elevations in blood pressure and markers of damage to the kidney and cardiovascular system in stroke prone spontaneously hypertensive rats (SPSHR). Male SPSHR (6 weeks old) were placed on high salt diets that contained 1% (w/w) NaCl added to their normal chow for 84 days and then were switched to 3% added NaCl for the remaining 63 days of the study. SPSHR was given 1.5% taurine in the drinking water (n = 8), a taurine free diet (n = 8) or normal chow (n = 8). A final control group (n = 6) was not given high salt diets. High salt diets caused an acceleration in the development of hypertension in all groups. Taurine supplementation reduced ventricular hypertrophy and decreased urinary excretion of protein and creatinine. The taurine free diet did not alter serum or urinary excretion of taurine, but did result in elevated urinary nitrogen excretion, increased serum cholesterol levels, and impaired performance in a spatial learning task. Alterations in dietary taurine intake did not alter urinary or serum electrolytes (Na⁺, K⁺), but taurine supplementation did attenuate a rise in serum calcium seen with the high salt diets. Urinary excretion (μg/24 h) of epinephrine and dopamine was significantly reduced in SPSHR given 1% NaCl in the diet, but this effect was not seen in SPSHR on taurine free or supplemented diets. Taurine supplementation showed cardioprotective and renoprotective effects in SPSHR given high salt diets. Received April 12, 1999/Accepted September 13, 1999     

Adult sterol metabolism is not affected by a positive sterol balance in the neonatal Golden Syrian hamster

Dietary components impact metabolism early in life. Some of the diet-induced effects are long lasting and can lead to various adult-based diseases. In the current studies, we examined the short-term effects of dietary cholesterol on neonatal hepatic sterol metabolism and the long-term effects that those early-life diets had on sterol metabolism in adulthood. Neonatal hamsters began consuming solid food as a supplement to milk by 5 days of age; diets contained 0 or 2% added cholesterol (wt/wt). By 10 days of age, plasma and liver cholesterol concentrations were 3.2- and 2.5-fold greater, respectively, in the neonates fed cholesterol. Hepatic sterol synthesis rates were suppressed 65% in cholesterol-fed neonates compared with control neonates. By 20 days of age, plasma and liver cholesterol concentrations were still greater and sterol synthesis rates were now suppressed maximally in neonates fed cholesterol compared with control neonates. The expression level of an apolipoprotein B-containing lipoprotein receptor (low-density lipoprotein receptor-related protein) was greater and the mature form of the sterol regulatory element-binding protein-2 was similar in livers of 20-day-old control neonates compared with control neonates at 10 days of age. To test whether the change in sterol balance in the neonatal period had a lasting effect on hepatic sterol metabolism, all animals were weaned on a low-cholesterol diet. At 70 days of age, hepatic sterol synthesis rates, plasma lipoprotein and liver cholesterol concentrations, and bile acid pool sizes and compositions were measured. Sterol balance in the adults was similar between animals fed either diet early in life, as demonstrated by a lack of difference in any parameter measured. Thus, even though dietary cholesterol suppressed hepatic sterol synthesis rates dramatically in the neonatal hamster, the change has little impact on sterol balance later in life.     

Taurine deficiency in maned wolves (Chrysocyon brachyurus) maintained on two diets manufactured for prevention of cystine urolithiasis

This study assesses the long‐term effects of an experimental diet vs. a commercially available manufactured diet, intended to reduce clinical disease related to cystinuria, on the taurine status of captive maned wolves. For 13 weeks, two pairs of maned wolves were maintained on the commercially available maintenance diet, whereas two individually housed wolves were maintained on the experimental diet. All six wolves, at the beginning and at the end of the diet trial, had severely decreased plasma concentrations of taurine (as compared to the normal canine reference range of 60–120 nmol/ml) (National Research Council [2003] National Academies Press) with average taurine concentrations of 16 nmol/ml at the beginning of the study and 3 nmol/ml at the end of the study. There was no statistically significant difference in the taurine concentrations between animals on the maintenance vs. experimental diets. Both diets were supplemented subsequently with taurine at a concentration of 0.3%. All study animals were eventually switched to the taurine‐supplemented version of the commercially manufactured maintenance diet and subsequent samplings were carried out to monitor plasma taurine concentrations. A final sampling, carried out approximately 5 months after the initiation of taurine supplementation, showed an average taurine concentration within the target canine reference range (90.25 nmol/ml). There are numerous physiologic (e.g., possible unique metabolism and requirements for taurine in this species as compared to other canids) and dietary factors (e.g., effects of the types and concentrations of fiber and protein on nutrient availability, taurine metabolism, and enterohepatic circulation of taurine‐conjugated bile salts; impaired taurine synthesis secondary to low cysteine availability) that could be potential contributors to the development of taurine deficiency in the maned wolves in this study. Taurine supplementation should be considered in maned wolves maintained on diets intended for reduction of cystinuria‐related complications. Zoo Biol 0:1–14, 2005. © 2005 Wiley‐Liss, Inc.     

Dietary carbohydrate composition modifies the milk N efficiency in late lactation cows fed low crude protein diets

Nitrogen emissions from dairy cows can be readily decreased by lowering the dietary CP concentration. The main objective of this work was to test whether the milk protein yield reduction associated with low N intakes could be partially compensated for by modifying the dietary carbohydrate composition (CHO). The effects of CHO on digestion, milk N efficiency (milk N/N intake; MNE) and animal performance were studied in four Jersey cows fed 100% or 80% of the recommended protein requirements using a 4×4 Latin square design. Four iso-energetic diets were formulated to two different CHO sources (starch diets with starch content of 34.3% and NDF at 32.5%, and fiber diets with starch content of 5.5% and NDF at 49.1%) and two CP levels (Low=12.0% and Normal=16.5%). The apparent digestible organic matter intake (DOMI) and the protein supply (protein digestible in the small intestine; PDIE) were similar between starch and fiber diets. As planned, microbial N flow (MNF) to the duodenum, estimated from the urinary purine derivatives (PD) excretion, was similar between Low and Normal CP diets. However, the MNF and the efficiency of microbial synthesis (g of microbial N/kg apparently DOMI) were higher for starch v. fiber diets. Milk and milk N fractions (CP, true protein, non-protein N (NPN)) yield were higher for starch compared with fiber diets and for Normal v. Low CP diets. Fecal N excretion was similar across dietary treatments. Despite a higher milk N ouput with starch v. fiber diets, the CHO modified neither the urinary N excretion nor the milk urea-N (MUN) concentration. The milk protein yield relative to both N and PDIE intakes was improved with starch compared with fiber diets. Concentrations of β-hydroxybutyrate, urea and Glu increased and those of glucose and Ala decreased in plasma of cows fed starch v. fiber diets. On the other hand, plasma concentration of albumin, urea, insulin and His increased in cows fed Normal compared with Low CP diets. This study showed that decreasing the dietary CP proportion from 16.5% to 12.0% increases and decreases considerably the MNE and the urinary N excretion, respectively. Moreover, present results show that at similar digestible OM and PDIE intakes, diets rich in starch improves the MNE and could partially compensate for the negative effects of Low CP diets on milk protein yield.     

Effects of dehydrated lucerne and soya bean meal on milk production and composition,nutrient digestion,and methane and nitrogen losses in dairy cows receiving two different forages

Dehydrated lucerne is used as a protein source in dairy cow rations, but little is known about the effects of lucerne on greenhouse gas production by animals. Eight Holstein dairy cows (average weight: 582 kg) were used in a replicated 4×4 Latin square design. They received diets based on either maize silage (M) or grass silage (G) (45% of diet on dry matter (DM) basis), with either soya bean meal (15% of diet DM) completed with beet pulp (15% of diet DM) (SP) or dehydrated lucerne (L) (30% of diet DM) as protein sources; MSP, ML, GSP and GL diets were calculated to meet energy requirements for milk production by dairy cows and degradable protein for rumen microbes. Dry matter intake (DMI) did not differ among diets (18.0 kg/day DMI); milk production was higher with SP diets than with L diets (26.0 v. 24.1 kg/day), but milk production did not vary with forage type. Milk fatty-acid (FA) composition was modified by both forage and protein sources: L and G diets resulted in less saturated FA, less linoleic acid, more trans-monounsaturated FA, and more linolenic acid than SP and M diets, respectively. Enteric methane (CH₄) production, measured by the SF₆ tracer method, was higher for G diets than for M diets, but did not differ with protein source. The same effects were observed when CH₄ was expressed per kg milk. Minor effects of diets on rumen fermentation pattern were observed. Manure CH₄ emissions estimated from faecal organic matter were negatively related to diet digestibility and were thus higher for L than SP diets, and higher for M than G diets; the resulting difference in total CH₄ production was small. Owing to diet formulation constraints, N intake was higher for SP than for L diets; interaction between forage type and protein source was significant for N intake. The same statistical effects were found for N in milk. Faecal and urinary N losses were determined from total faeces and urine collection. Faecal N output was lower for M than for G diets but did not differ between protein sources. Urinary N output did not differ between forage types, but was lower for cows fed L diets than for cows fed SP diets, potentially resulting in lower ammonia emissions with L diets. Replacing soya bean meal plus beet pulp with dehydrated lucerne did not change CH₄ production, but resulted in more N in faeces and less N in urine.     

Effect of dietary taurine supplementation on metabolome variation in plasma of Nile tilapia

Taurine has been considered as an essential nutrient for many aquaculture species. While dietary taurine supplementation is highly recommended, novelty studies on taurine metabolism in fish are needed. The present study aimed to provide insight into the molecular mechanisms involved in multiple metabolome changes in Nile tilapia (Oreochromis niloticus) by studying plasma metabolic profile changes in response to graded levels of dietary taurine supplementation. The analysis used proton nuclear magnetic resonance-based metabolomics. Four groups of tilapias were fed with four diets supplemented with 0.0, 0.4, 0.8 and 1.2% taurine for 84 days. Fish plasma was sampled at multiple time points to provide an accurate snapshot of specific metabolic profiles during growth. Under the effect of taurine supplementation, 21 and 12 metabolites in tilapia plasma shown significant changes in terms of time-dependence and diet-dependence, respectively. These metabolic changes in tilapia plasma were mainly associated with energy and amino acid metabolism, lipids, nucleotides and protein metabolism. The results indicate that 0.8% taurine supplementation could significantly improve the carbohydrate synthesis, protein digestion and absorption, and fat deposition of tilapia and thereby promoted growth and development of tilapia.     

Effects of Taurine Supplementation on Hepatic Markers of Inflammation and Lipid Metabolism in Mothers and Offspring in the Setting of Maternal Obesity

Maternal obesity is associated with obesity and metabolic disorders in offspring. However, intervention strategies to reverse or ameliorate the effects of maternal obesity on offspring health are limited. Following maternal undernutrition, taurine supplementation can improve outcomes in offspring, possibly via effects on glucose homeostasis and insulin secretion. The effects of taurine in mediating inflammatory processes as a protective mechanism has not been investigated. Further, the efficacy of taurine supplementation in the setting of maternal obesity is not known. Using a model of maternal obesity, we examined the effects of maternal taurine supplementation on outcomes related to inflammation and lipid metabolism in mothers and neonates. Time-mated Wistar rats were randomised to either: 1) control : control diet during pregnancy and lactation (CON); 2) CON supplemented with 1.5% taurine in drinking water (CT); 3) maternal obesogenic diet (high fat, high fructose) during pregnancy and lactation (MO); or 4) MO supplemented with taurine (MOT). Maternal and neonatal weights, plasma cytokines and hepatic gene expression were analysed. A MO diet resulted in maternal hyperinsulinemia and hyperleptinemia and increased plasma glucose, glutamate and TNF-α concentrations. Taurine normalised maternal plasma TNF-α and glutamate concentrations in MOT animals. Both MO and MOT mothers displayed evidence of fatty liver accompanied by alterations in key markers of hepatic lipid metabolism. MO neonates displayed a pro-inflammatory hepatic profile which was partially rescued in MOT offspring. Conversely, a pro-inflammatory phenotype was observed in MOT mothers suggesting a possible maternal trade-off to protect the neonate. Despite protective effects of taurine in MOT offspring, neonatal mortality was increased in CT neonates, indicating possible adverse effects of taurine in the setting of normal pregnancy. These data suggest that maternal taurine supplementation may ameliorate the adverse effects observed in offspring following a maternal obesogenic diet but these effects are dependent upon prior maternal nutritional background.     

Different diets and amino acid supplementation do not affect the voluntary consumption of ethanol by rats

The effects of four different diets (control diet: 19.5% protein, 60.5% carbohydrate, 10% fat; diet I: 65% protein, 10% carbohydrate, 10% fat; diet II: 5% protein, 76% carbohydrate, 10% fat; diet III: 20% protein, 69% carbohydrate, 1% fat; diet IV: 69% protein, 15% carbohydrate, 1% fat) and supplementation with 3 amino acids (tryptophan: 150 mg/kg/d; arginine: 400 mg/kg/d; taurine: 380 mg/kg/d) on the voluntary consumption of ethanol were investigated in rats using the 2 bottle method. First, rats received the control diet and diets I, II, III and IV for 20 days with a choice of ethanol for the last 6 days only. Ethanol consumption was similar in all dietary groups. Second, rats received the control diet for 8 days followed by diets I, II and IV for another 8 days. Ethanol was offered throughout both periods. The switch to the special diets did not affect ethanol consumption. Third, rats received a control diet with arginine, tryptophan or taurine added to the drinking fluids for 16 days with a choice of ethanol for the last 5 days; thereafter supplementation stopped but the ethanol choice remained. No difference in the voluntary intake of ethanol was noted but ethanol consumption fell after cessation of arginine supplementation. In conclusion, diets differing greatly in their composition or supplementation with these 3 amino acids did not affect the voluntary choice of ethanol by rats in a significant manner.     

Net protein utilization of stock diets for rats and mice

Male Sprague-Dawley rats of six weeks of age were fed on ten percent crude protein diets for a ten day experimental period. The net protein utilization (NPU) by carcass analysis of six kinds of revised stock diets for rats and mice was compared with that of purified whole-egg protein and milk casein. NPU values for all revised stock diets and milk casein were lower than those for purified whole-egg protein. Compared to milk casein, two kinds of revised stock diets showed lower NPU, but the remaining four diets had similar NPU.     

Effects of partial replacement of soybean meal with other protein sources in diets of lactating cows

The protein nutrition of dairy cows is of great importance because of its direct influence on milk production, reproductive efficiency, and feeding cost. Eight first-lactation Holstein cows were randomly assigned to two contemporary 4 × 4 Latin squares in a 2 × 2 factorial design to evaluate the effects of replacing soybean meal with yeast-derived microbial protein (YMP) as a protein source (0% or 1.5% of dry matter (DM)) and its combination with slow-release urea (SRU; 0% or 0.75% of DM) on DM intake and milk production and composition, as well as blood parameters and nitrogen balance. Each experimental period lasted 28 days, with 21 days of adaptation and 7 days of data collection. The diets were formulated to attend the nutritional recommendations of the National Research Council and consisted of 49% forage (47% corn silage and 2% Tifton hay) and 51% concentrate, with 16.8% CP and 1.6 Mcal net energy for lactation/kg DM. For diets without YMP, the inclusion of SRU decreased DM intake, milk production as well as N intake and balance, but did not affect efficiency of production, milk composition or most of blood parameters. On the contrary, for diets with YMP, DM intake and milk production were increased by inclusion of SRU, while minor effects were observed for milk efficiency and composition, blood parameters as well as N intake, excretion and balance. When diets with SRU were compared, the inclusion of YMP increased DM intake, 4% fat-corrected milk, and N intake and balance (P<0.05), with no differences in milk production (kg/day), milk energy, efficiency of milk production or most of the blood parameters. For diets without SRU, YMP inclusion decreased DM intake, milk production, milk energy, N intake, fecal N and N balance (P<0.05), with no effects on milk efficiency and composition, or most of blood parameters. In conclusion, the use of YMP, SRU or both as partial substitutes of soybean meal in the diet of lactating cows has no negative effects on productivity parameters.     

The replacement of skim milk by dried microbial cells and whey in milk diets for calves

In two experiments, the performance and health of calves fed on diets containing dried microbial cells (DMC) was monitored. In the first experiment 32 seven-day-old British Friesian bull calves, reared on a conventional early weaning system to 8 weeks of age, were given milk replacers in which 5, 10 and 20% spray-dried DMC and whey replaced 14–55% of skim milk protein. All DMC diets contained 36 g/kg of non-nucleic acid nitrogen. In Experiment 2, 38 two-day-old Ayrshire bull calves were fed for 63 days solely on one of two milk diets containing 0 or 10% DMC at 5 levels of intake designed to produce body gains of 0–1 kg/day. While the inclusion of up to 10% DMC in both experiments had little effect on performance or health, 20% DMC was associated with severe diarrhoea, loss of appetite and growth retardation, and impaired clotting of the milk in vitro. In Experiment 2 the response, in gain, by calves given increasing intakes of milk dry matter was linear and was unaffected by the type of diet offered.It was concluded that when levels of DMC in excess of 10% inclusion are used in association with maize starch, deleterious effects on performance are likely.     

Effect of dry-matter concentration of milk substitute and method of feeding on intake and performance by lambs

Forty-eight lambs were artificially reared from 1 day old and offered milk substitute reconstituted to give diets containing 10, 16, 22 and 28% dry matter (DM). Three feeding methods were used for each diet: milk substitute available ad libitum (AL); restricted to a mean daily intake of 1300 g liquid milk substitute (RLQ); and restricted to a mean daily intake of 247 g milk substitute DM (RDM).Solid food intake and lamb growth rate were measured both before and after weaning at 28 days.For method AL, decreasing DM concentration in the milk substitute increased intake of the liquid but decreased that of DM. When DM intakes were held constant, neither method of feeding nor DM concentration had an effect on lamb growth, and level of reconstitution of the milk substitute had no effect on its digestibility. Differences in growth rate before weaning were due entirely to differences in intake of milk substitute DM.After weaning, lambs which had received the diet containing 10% DM tended to perform less well than those that had received the other diets.The lambs were slaughtered at 35 kg live weight. There were no effects of treatment on gains of water, fat and protein.     

The utilization of canola and its constituents by lactating dairy cows

Three feeding trials and one nylon bag trial were conducted to determine the effect of supplementing a barley-based control diet with 3.5% canola oil (CO), 22% presscake (CPC) or 9% whole seed (WCS) on feed intake, digestibility, milk yield and composition of lactating dairy cows. Ruminal utilization of canola meal (CM), CPC and WCS was also determined. Increasing the level of fat in the diet had no significant effect on intake of concentrate or digestible energy, or on total tract digestibility of dry matter (DM), crude protein (CP) and acid detergent fibre. Addition of canola in the form of CPC and WCS gave greater energy and ether extract digestibility than C and CO (P < 0.05). Diet had no significant effect on milk production, yield of milk CP, milk lactose + ash, gross energetic efficiency of milk production, milk urea or minerals. Milk fat and 4% fat corrected milk (FCM) yield were similar with the C and CPC diets, and with the CO and WCS diets. But the CO and WCS diets gave less milk fat and FCM than the C diet (P < 0.05). Milk crude protein was higher (P < 0.05) on the WCS diet than on the C, CO and CPC diets, which were similar. Diets WCS, C and CO promoted similar levels of blood urea (BU) but BU levels with CPC and CO were lower than with the C diet (P < 0.05). Ruminal DM and CP disappearance of CM was lower than for WCS and CPC at all incubation times (P < 0.05).     

Effects of mixtures of red clover and maize silages on the partitioning of dietary nitrogen between milk and urine by dairy cows

Eight multiparous lactating Holstein-Friesian cows were used to evaluate the partitioning of dietary nitrogen (N) from diets based on mixtures of red clover and maize silages in comparison with diets based on ryegrass silage. All cows received 4 kg/day of a standard dairy concentrate with one of four forage treatments in an incomplete changeover design with three 4-week periods. Three treatments were based on mixtures of red clover and maize silage. N intake was altered both by varying the ratio of these silages (40/60 and 25/75 on a dry matter (DM) basis) and by an additional treatment for which the DM intake of the 40/60 mixture was restricted to the level achieved with grass silage. Rumen passage rates were estimated from faecal excretion curves following a pulse oral dose of Dysprosium-labeled silage and urinary excretion of purine derivatives (PD) was used as an index of rumen microbial protein synthesis. Red clover silage mixtures led to significantly increased feed intake (21.5, 20.7 and 15.2 kg DM/day for 40/60 and 25/75 red clover/maize silage mixtures and grass silage, respectively), milk production (25.8, 27.8 and 20.0 kg/day for the same treatments, respectively) and milk component yields, but were without effect on milk fat and protein concentrations. The large increase in the yield of milk (24.5 kg/day) and milk components for the restricted red clover/maize silage treatment, in comparison with the grass silage treatment, was proportionately greater than the increase in DM intake (16.6 kg DM/day). There were no significant treatment effects on diet digestibility, while the higher intakes of red clover silage mixtures were associated with higher rumen passage rates (5.82%, 6.24% and 4.55%/h, respectively). There were significant effects of both N intake and forage source on the partitioning of dietary N between milk and urine. When dietary protein was diluted by the inclusion of maize silage, red clover silage led to increased milk N and reduced urinary N in comparison with grass silage. Improvements in N utilisation may be related to increased dietary starch and/or rumen passage rates leading to increased microbial protein synthesis for these treatments. Urinary excretion of PD was significantly higher for all diets based on mixtures of red clover and maize silages, in comparison with grass silage. Urinary N output was close to literature predictions based on N intake for the diet based on ryegrass silage, but 40 to 80 g/day (25% to 30%) less than predicted for the diets based on the mixtures of red clover and maize silages.     

Comparison of taurine biosynthesis ability between juveniles of Japanese flounder and common carp

This study was conducted to investigate taurine deficiency and the ability of taurine biosynthesis in both juvenile Japanese flounder (JF) and juvenile common carp (CC) in vivo using low taurine level diets. Three different taurine level diets were prepared by the supplementation of taurine to the basal composition (JF--0, 0.5 and 1.5% in JF; CC--0, 1, 3% in CC). The final average body weight and feed efficiency of JF fed the JF - 1.5% was significantly higher than those of fish fed on the JF--0%. On the other hand, no significant difference was observed in CC fed with CC--0, 1, and 3% diets. The taurine retention rate was negative in the case of JF-fed with the taurine-free supplement (JF--0%). On the other hand, the taurine retention rate was about 280% in the case of CC-fed with the taurine-free supplement (CC--0%). These findings indicate that while taurine is essential for growth of JF, it is not essential for the growth of CC.     

Taurine Supplementation Reduces Blood Pressure and Prevents Endothelial Dysfunction and Oxidative Stress in Post-Weaning Protein-Restricted Rats

Introduction

Taurine is a sulfur-containing amino acid that exerts protective effects on vascular function and structure in several models of cardiovascular diseases through its antioxidant and anti-inflammatory properties. Early protein malnutrition reprograms the cardiovascular system and is linked to hypertension in adulthood. This study assessed the effects of taurine supplementation in vascular alterations induced by protein restriction in post-weaning rats.

Methods and Results

Weaned male Wistar rats were fed normal- (12%, NP) or low-protein (6%, LP) diets for 90 days. Half of the NP and LP rats concomitantly received 2.5% taurine supplementation in the drinking water (NPT and LPT, respectively). LP rats showed elevated systolic, diastolic and mean arterial blood pressure versus NP rats; taurine supplementation partially prevented this increase. There was a reduced relaxation response to acetylcholine in isolated thoracic aortic rings from the LP group that was reversed by superoxide dismutase (SOD) or apocynin incubation. Protein expression of p47^phox NADPH oxidase subunit was enhanced, whereas extracellular (EC)-SOD and endothelial nitric oxide synthase phosphorylation at Ser 1177 (p-eNOS) were reduced in aortas from LP rats. Furthermore, ROS production was enhanced while acetylcholine-induced NO release was reduced in aortas from the LP group. Taurine supplementation improved the relaxation response to acetylcholine and eNOS-derived NO production, increased EC-SOD and p-eNOS protein expression, as well as reduced ROS generation and p47^phox expression in the aortas from LPT rats. LP rats showed an increased aortic wall/lumen ratio and taurine prevented this remodeling through a reduction in wall media thickness.

Conclusion

Our data indicate a protective role of taurine supplementation on the high blood pressure, endothelial dysfunction and vascular remodeling induced by post-weaning protein restriction. The beneficial vascular effect of taurine was associated with restoration of vascular redox homeostasis and improvement of NO bioavailability.     

Indigestion in Young Calves

Increasing the lactose content of different milk replacers or milk diets by approx. 30 % of the dry matter increased the frequency of diarrhoea the first 10–12 days in young calves on all occasions in 5 experiments comprising 120 calves. For all diets taken together, this effect was highly significant. Total daily intakes of lactose amounted to 200–480 g. When lactose was given on top of the milk rations, the growth rate increased significantly, whereas the growth rate was usually insignificantly reduced when lactose replaced other nutrients in milk diets or milk replacers, their levels of protein and fat becoming low. Albumin and total protein in blood plasma were significantly lower when the dietary protein level was low. Milk replacers with 20 or 40 % whey powder, replacing skim milk powder, performed equally well, but gave significantly less growth than the old-fashioned feeding of whole milk-skim milk. Intake of hay and barley and a number of clinical and histological or pathological parameters did not vary consistently with dietary level of whey powder or lactose. Feeding whole milk all the time resulted in low intake of hay and barley and poorly developed forestomachs, but high dressing-out %. Substituting soya for part of the skim milk powder in milk replacers gave abomasal content with no curds. In most cases, pH in the rumen appeared to be nearly up to neutral until the calves ate ground barley, about 1 month old.     

Milk yield response of dairy cows fed fat along with protein

The influence of a fat-coated protein on milk production of Holstein dairy cows was determined using a 4×4 Latin square experiment. Twelve cows were fed a control diet or test diets supplemented with fat, fat plus ruminally undegraded protein (RUP), or a fat-coated protein (Duets™). Cows fed test diets received 0.55 kg of more fat per day than cows in the control treatment. Daily intakes of feed, energy, and protein were the same in all treatments. Cows produced 36.5, 37.3, 37.9, and 39.3 kg of energy-corrected milk per day in control, fat, fat plus RUP, and fat-coated protein treatments, respectively. Cows fed fat-supplemented diets produced an average 1.7 kg more milk daily compared with cows in the control treatment. Feeding RUP along with fat or fat-coated protein provided no further improvement in milk yield compared with fat alone, but partially alleviated the depression in protein content caused by supplemental fat and increased the daily yield of milk protein. In the present experiment, cows fed fat-coated protein produced daily an average 60 g of milk protein more than cows fed fat alone. Since, there was no advantage in milk yield, the decision to include fat-coated protein in dairy rations should be based on its price compared to fat alone and the return in terms of milk protein yield.     

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part II: effects of supplementation with methionine or taurine on growth,feed utilization,and health

Fishmeal has long been a staple protein feedstuff for fish, but its global shortage and high price have prompted its replacement with alternative sustainable sources. In this experiment involving largemouth bass (a carnivorous fish), a new mixture of feedstuffs (45% poultry byproduct meal, 30% soybean meal, 15% blood meal, and 10% krill shrimp meal) was added to low (14.5%) fishmeal diets along with 0.0%, 0.5% taurine, 0.5% methionine, or 0.5% taurine plus 0.5% methionine (dry matter basis). The positive control diet [65.3% fishmeal (46% crude protein on dry matter basis)] and all low-fishmeal diets contained 40% true protein and 10% lipids. There were 3 tanks per treatment group (20 fish/tank). Fish with the mean initial body weight of 16.6 g were fed to satiety twice daily. Compared with the unsupplemented low-fishmeal group, supplementing either 0.5% methionine or 0.5% methionine plus 0.5% taurine to the low-fishmeal diet improved (P < 0.05) the growth, feed utilization, retention of dietary protein and lipids, and health of largemouth bass, reduced (P < 0.05) the occurrence of black skin syndrome from ~ 40 to ~ 10%. Histological sections of tissues from the fish with black skin syndrome showed retina degeneration, liver damage, and enteritis in the intestine. Compared with methionine supplementation, supplementing 0.5% taurine alone to the low-fishmeal diet did not affect the growth or feed efficiency of fish and had less beneficial effects (P < 0.05) on ameliorating the black skin syndrome. These results indicated that: (a) the basal low-fishmeal diet was inadequate in methionine or taurine; and (b) dietary supplementation with methionine was an effective method to improve the growth performance, feed efficiency, and health of largemouth bass. Further studies are warranted to understand the pathogenesis of the black skin syndrome in largemouth bass.

     

Fish protein hydrolysate elevates plasma bile acids and reduces visceral adipose tissue mass in rats

Conjugation of bile acids (BAs) to the amino acids taurine or glycine increases their solubility and promotes liver BA secretion. Supplementing diets with taurine or glycine modulates BA metabolism and enhances fecal BA excretion in rats. However, it is still unclear whether dietary proteins varying in taurine and glycine contents alter BA metabolism, and thereby modulate the recently discovered systemic effects of BAs. Here we show that rats fed a diet containing saithe fish protein hydrolysate (saithe FPH), rich in taurine and glycine, for 26 days had markedly elevated fasting plasma BA levels relative to rats fed soy protein or casein. Concomitantly, the saithe FPH fed rats had reduced liver lipids and fasting plasma TAG levels. Furthermore, visceral adipose tissue mass was reduced and expression of genes involved in fatty acid oxidation and energy expenditure was induced in perirenal/retroperitoneal adipose tissues of rats fed saithe FPH. Our results provide the first evidence that dietary protein sources with different amino acid compositions can modulate the level of plasma bile acids and our data suggest potential novel mechanisms by which dietary protein sources can affect energy metabolism.