Effects Of Dietary Crude Protein Research Articles

Effects of Dietary Crude Protein on Growth Performance, Nutrient Utilization, Immunity Index and Protease Activity in Weaner to 2 Month-old New Zealand Rabbits

An experiment was conducted to determine the effects of different dietary crude protein (CP) levels on growth performance, nutrient utilization, small intestine protease activity and immunity index of weaner to 2 month-old New Zealand rabbits. Eighty weaner rabbits were allocated in individual cages to five treatments in which they were fed diets with CP at 14%, 16%, 18%, 20% and 22%, respectively. The growth performance and nutrient digestibility of rabbits increased firstly when dietary CP increased, then decreased. The average daily gain was the highest and feed conversion rate was the lowest when dietary CP reached 20%, namely 34.9 g/d and 2.74:1, respectively. Maximum CP digestibility was 72.1% in the 18% CP group, maximum crude fiber digestibility of 28.4% occurred in the 16% CP group and was significantly different from other treatments (p 0.05), and was highest for 20% CP treatment (1.5 g/d). The effect of CP level on the rate of digestible nitrogen (DN) converted RN was small. The spleen index, thymus index, chymotrypsin and trypsin activities in small intestine were highest when dietary CP was 16%, which were 1.0, 2.8, 15.7 U/g and 125.7 U/g, respectively. There was no significant difference among treatments (p>0.05). According to the above results, the appropriate dietary CP level from weaner to 2 month-old meat rabbits was 18-20%.

Growth Performance and Body Composition of Palmetto Bass Fed Five Levels of Dietary Protein at Two Energy‐to‐Protein Ratios

AbstractA feeding trial was conducted to determine the effects of dietary crude protein (CP) level and digestible energy‐to‐protein (DE:P) ratio on the growth performance and body composition of palmetto bass (female striped bass Morone saxatilis × male white bass M. chrysops). Ten soybean‐meal‐based diets were prepared to contain 30, 35, 40, 45, or 50% CP at DE:P ratios of 33.48 or 41.85 kJ/g CP. The diets contained lyophilized palmetto bass muscle as the sole animal protein source to improve dietary amino acid composition. Wheat middlings and corn grain were the major sources of carbohydrates, and the diets were formulated to meet the known nutritional requirements of palmetto bass. Fish fed 35% or 40% CP at 33.48 or 41.85 kJ/g CP had significantly (P ≤ 0.05) greater weight gains and higher feed efficiency ratios than fish fed the other diets. The protein efficiency ratio (g weight gain/g CP consumed) decreased and visceral fat ([g visceral fat × 100]/g body weight) increased as the dietary protein level increased in both DE:P treatments. The hepatosomatic index ([g liver weight × 100]/g body weight) increased with the dietary protein level up to 40–45% CP. Whole‐body muscle content and fillet yield did not differ significantly among fish fed any of the diets at either DE:P ratio. The lipid content of fillets was higher among fish fed 45–50% CP than among those fed up to 40% CP. Hematocrit and serum protein concentrations were not affected by the dietary CP level or the DE:P treatment. Overall, the DE:P ratio had little or no effect on most of the parameters of interest. Based on our comparisons of weight gain, diet utilization efficiency, and body composition among treatment groups, a 35% CP diet with 41.85 kJ/g CP was considered optimum for palmetto bass under the conditions of this study.

Effects of dietary protein concentration and specific amino acids on body weight, body composition and feather growth in young turkeys

1. Two randomised block factorial experiments were conducted to investigate the relationships between the effects of dietary crude protein and specific amino acid concentrations on the relative growth of the body and feathers of young turkeys. 2. Decreasing dietary crude protein concentration from 300 to 180 g /kg in experiment 1 reduced the body and breast muscle weights of a large male line of turkeys proportionally by 0·44 and 0·52 compared with 0·19 and 0·24 in a small traditional line. 3. Decreasing dietary crude protein concentration was associated with a maximum reduction in feather weight of 0·18 and 0·24 respectively in male line and traditional turkeys. The length of the feathers in the cranial region of the breast decreased from 26 to 19 mm in the traditional line compared with an increase from 14 to 25 mm in male line turkeys. 4. Decreasing dietary crude protein concentration was associated with an increase in the fat content of the feather-free carcase. Male line turkeys had a higher carcase fat and lower feather dry matter content than the traditional turkeys. 5. It was concluded that dietary crude protein was preferentially partitioned to feather rather than muscle growth in the male line in contrast to a traditional line of turkeys in which the growth of feathers and muscle were affected equally. 6. In experiment 2, the amino acids arginine, valine, methionine and tyrosine were added separately to a common basal ration (180 g CP/kg) to raise their concentration to that of the control ration (260 g CP/kg). Each ration was fed ad libitum to male line turkeys from 2 to 6 weeks of age. 7. Amino acid supplementation increased body and breast muscle weights. 8. Compared with the basal ration, tyrosine was associated with a reduction in feather weight whereas valine had no effect. Supplementation with arginine and methionine resulted in increased feather weights that were similar to that of the controls. 9. It was concluded that arginine and methionine were used preferentially and are essential for feather growth. Excess amino acids that are not required for feather growth such as tyrosine and valine were used for increased body growth and resulted in relatively poor feather cover. 10. The results suggest that feather growth was maintained as much as possible at the expense of body growth when the amino acid concentration of the ration was less than that required to maximise body and muscle weight gain in large male line turkeys.

Hepatic 5′ deiodinase activity in the broiler chicken: effects of diet and prior thyroid status

Male, Shaver broiler chickens growing from 7 to 49 days of age were used in two experiments to demonstrate the effects of dietary crude protein (CP) and thyroid hormone deficiency-replenishment on 5′D activity. In the first experiment, birds were fed 18% CP ± 1 g/kg methimazole (M) from 7–28 days and then an 18% CP diet ± 1 mg/kg T 3 for 8 days. The second experiment involved feeding three levels of CP (12, 18 & 24%) ± 1 g/kg M from 7 to 28 days and an 18% CP from 28–49 days. Methimazole depressed both plasma T 3 and T 4. Although M depressed and supplemental T 3 increased 5′D per gram of liver in the first experiment, M also increased the relative liver size. Thus, total T 3 productive capacity increased in the face of a decrease in specific activity. Again, in the second experiment, M depressed both T 3 and T 4. In addition, low a low protein diet also depressed T 4. Both CP and M affected 5′D activity in 28-day-old birds. In contrast, only the carry over effect of M was significant in 49-day-old birds. It is suggested from these studies that particular care must be taken in selecting a method to express 5′D activity. Permutations in the thyroid state alter the liver size of the bird, distorting values expressed per unit of liver weight. Values expressed per unit of protein may fail to account for the influence of changes in liver size on total 5′D activity.

Effects of dietary protein level and cold exposure on tissue responsiveness and sensitivity to insulin in sheep

The effects of dietary crude protein (CP) level and cold exposure on tissue responsiveness and sensitivity to insulin were studied in sheep. Nine rams were assigned to one of three isoenergetic diets which contained 70, 100, and 140% of CP for maintenance. They were exposed from a thermoneutral environment (20 degrees C) to a cold environment (0 degrees C) for 7 days. A hyperinsulinemic euglycemic clamp approach was applied for the determination of tissue responsiveness to insulin (the maximal glucose infusion rate, GIRmax) and tissue sensitivity to insulin (the plasma insulin concentration at half maximal glucose infusion rate, ED50). Dietary CP level influenced digestibilities of dry matter and CP (P=0.002 and P=0.001, respectively), and cold exposure decreased (P=0.01) CP digestibility. The GIRmax and ED50 tended to be influenced (P=0.08) by dietary CP level. The GIRmax was enhanced (P=0.0001) during cold exposure. Significant interactions between diet and environment were found for the GIRmax (P=0.04), but not for ED50 (P=0.07). It is concluded that in sheep dietary CP level can modify insulin action in response to cold exposure.

Fütterungs- und nicht fütterungsbedingte Einflüsse auf den Milchharnstoffgehalt von Milchkühen – 1. Mitteilung: Fütterungsbedingte Einflussfaktoren auf den Milchharnstoffgehalt von Milchkühen

Abstract. Title of the paper: The impact of nutrition and non nutrition factors on milk urea concentration. I. The impact of nutrition factors on milk urea concentration The object of this study was to determine the impact of dietary crude protein / energy balance, stage of lactation parity, milk yield or milk protein yield, milk protein content, somatic cell count, season and herd on milk ureä concentration under the conditions of large herds (50–1000 dairy cows) and routine milk yield recording. From this data a model was created to predict the milk urea concentration for a single dairy cow or a feeding group For the analysis of the data a mixed linear model (proc mixed; SAS®, 1997) was used. The fixed effects (ratio of crude protein / energy, degradability of dietary crude protein, ruminal N-balance, lactation period, parity) was computed by generalized least-squares-means. The season, herd and month were used as random effects Milk yield or milk protein yield, milk protein content, somatic cell count and day in milk were included as Covariables in the model. The effect of dietary crude protein / energy balance on milk urea was significant (p < 0.0001). For diets with an optimal ratio of crude protein / energy (according to GfE, 1997) 226 mg/1 was calculated using least-squares-means. For diets with excess of crude protein this figure rose to 252 mg/1 In this study a significant difference in least-squares-means calculated urea concentration did not existed for degradability of dietary crude protein. On the other hand, a significant difference in least-squares-means calculated urea concentration existed for ruminal N-balance between 0 and 2.

Nitrogen Metabolism of Early Lactation Cows Fed Diets with Two Different Levels of Protein and Different Amino Acid Profiles

Four multiparous Holstein cows (569±122kg) surgically prepared with indwelling catheters in the mesenteric, portal, and hepatic veins and carotid artery were allocated in a 4 × 4 Latin square to determine the effects of dietary crude protein (CP) level and amino acid (AA) profile on N metabolism during early lactation (from 25 to 65 d in milk). Cows received their diets in two equal meals and were milked twice daily. The dietary treatments were: 18% CP with a high (18H) or a low (18L) quality AA profile, and 15% CP with a high (15H) or a low (15L) quality AA profile. The four diets were similar in net energy for lactation (1.75 NEL Mcal/kg) and contained the same amount of RUP (34% of CP). The quality of the AA profile pertained only to the essential AA (EAA), and was assessed by comparison with the EAA profile of casein and considered the potential contribution of EAA from ruminal bacteria. The 18H and 15H diets were supplemented with 50 and 25g/d of ruminally protected Met, respectively. After 10 d on treatment, a blood flow marker (p-amino-hippurate) was infused into a mesenteric vein, and arterial, portal, hepatic, and mammary blood samples were obtained at 3, 6, and 12h after feeding. Dry matter intake was similar across treatments (23.4±0.5kg/d). Amino acid oxidation, and consequent urea production, in the liver were numerically greater with the 18% CP rations, and, as a result, arterial urea concentrations were greatest (P<0.01) with these rations. The amount of total AA extracted by the mammary gland tended to be greater with the H than with the L diets (21.4 vs. 18.2 mmol/ h, respectively). Milk yield tended to be greater (P=0.16) with the 18H and 15H diets (47.7 and 46.3kg/d, respectively) compared with the 18L and 15L diets (45.9 and 44.6kg/d, respectively). Also, milk CP and casein contents were greatest (P=0.09) with the H diets compared with the L diets. Milk and plasma urea N were greatest (P<0.01) with the 18% CP diets. The efficiency of N utilization for milk protein synthesis was greatest (P<0.09) with the 15% CP diets. It is concluded that milk protein production during early lactation is less susceptible to variations in dietary CP contents than variations in the AA profile of the dietary protein.

The effect of dietary crude protein on growth, ammonia concentration, and litter composition in broilers

An experiment was conducted to determine the effect of diets with reduced CP and supplemental amino acids on broiler performance, N excretion, litter characteristics, and equilibrium NH3 gas concentration. Results suggest that reducing CP (and lysine) below 241 g/kg (13.7 g/kg lysine) in the diets fed during the first 3 wk may slightly increase feed:gain and therefore may not be advisable. During the period 22 to 43 d of age there were no significant differences in weight gain and BW at 6 wk of age when reducing CP from 215 g/kg (11.5 g/kg lysine) to 196 g/kg (11.3 g/kg lysine), but feed intake and feed:gain ratio increased. However, reducing CP did cause equilibrium NH3 gas concentration and litter N to decline by 31 and 16.5%, respectively. Both of these advantages will improve air quality within the housing facility and possibly reduce heating costs during winter associated with higher ventilation rates required to reduce elevated NH3 gas concentrations.

Effect of Dietary Energy and Protein Concentration on the Concentration of Milk Urea Nitrogen in Dairy Ewes

To study the effects of dietary crude protein (CP) and energy on milk urea N concentrations in dairy sheep, eight pelleted total mixed rations were prepared to obtain two levels of energy density (1.65 and 1.55 Mcal of net energy for lactation per kilogram of dry matter for high energy and low energy rations, respectively) and four concentrations of CP within each energy level (mean CP concentrations, 14.0, 16.4, 18.7, and 21.2% of dry matter). The experimental design consisted of two 4 × 4 Latin squares (one per energy level) with two replications per treatment within each 3-wk period. Milk urea N concentrations were similar between dietary energy levels. Within each energy level, milk urea N was linearly and positively associated with dietary CP content and intake (range of milk urea N concentrations, 12.2 to 25.8 mg/dl for ewes fed high energy rations and 12.9 to 26.7 mg/dl for ewes fed low energy rations). The comparison of these results with those from other trials suggested that milk and blood urea N concentrations are closely correlated with dietary CP concentrations and less closely correlated with dietary CP intake. Our results suggest that milk or blood urea N concentrations can be used as indicators of protein metabolism and intake of lactating ewes.

Effect of dietary crude protein and energy content on nitrogen utilisation, water intake and urinary output in growing pigs

A digestibility and balance trial was carried out with four intact castrated male pigs (live weight 33-82 kg) to study the effects of dietary crude protein and energy content on nutrient digestibility, nitrogen metabolism, water intake and urinary output. In a 4 x 4 Latin square design, four barley-oats-soya bean meal based diets were arranged 2x2 factorially. The corresponding factors were dietary crude protein (CP) content: high (180 g/kg CP) or low protein diet (140 g/kg CP) supplemented with free lysine, methionine and threonine; and dietary net energy content; high (1.05 feed units (FU)/kg) (feed unit=9.3 MJ net energy) or low net energy content (0.95 FU/kg). Lowering dietary CP content (mean values of 189 to 152 g/kg dry matter, respectively) by supplementation of free amino acids decreased urinary nitrogen (N) excretion by 6.9 g/day (32%) (P

Further studies on carry-over effects of dietary crude protein and triiodothyronine (T3) in broiler chickens.

Indian River male broiler chickens growing from 7 to 28 d of age were fed on diets containing either 120 or 210 g crude protein and 0 or 1 mg triiodothyronine (T3)/kg diet to study in vitro lipogenesis (IVL). In addition, a carry-over period (180 g crude protein/kg diet from 28 to 40 d of age) was used to test the persistence of prior treatment effects. The higher protein level increased, but T3 decreased (P < 0.01) growth and feed consumption at 28 d of age. The lower protein level increased (P < 0.05) and T3 decreased IVL in 28-d-old chickens. These effects were only sustained for 6 d following the switch to a common diet at 28 d. IVL at 40 d of age was not affected by either crude protein or T3 fed during the 7-28 d period. The higher protein level increased plasma insulin-like growth factor-1 during the period from 7 to 28 d; however, this effect lasted for only 6 d following the switch to a common diet. Plasma growth hormone (GH) at 28 d of age was inversely related to dietary protein level. Changing to a common level of crude protein did not change plasma GH values at 12 d, indicating that the nutritional state of the young chicken may affect GH at a later period of life. Metabolic changes noted in this study were rapid and maintained for a short period of time following the feeding of a common diet.

Effects of dietary crude protein content and food intake on the production of semen in two lines of broiler breeder males

1. The effects of dietary crude protein (CP) concentration and feeding rate on semen production and quality from 21 to 66 weeks of age were assessed in a factorial experiment with 48 caged broiler breeder males from 2 strains. 2. The probability of obtaining semen and semen volume were lower in one of the two strains but the concentration and yield of spermatozoa were similar. 3. There was no evidence that males which were fed on an increasing quantity of food produced more semen or a greater concentration of spermatozoa than males on a fixed allocation of 120 g/d food. 4. The concentration of spermatozoa was lower in males fed on a diet containing 160 compared with 120 g CP/kg. On termination of the experiment, average testes size was small and testicular function was absent in a large proportion of the males on the high protein diet.

Effects of Dietary Crude Protein, Breed, Parity, and Health Status on the Fertility of Dairy Cows

A study was conducted to determine the impact of dietary CP (13% vs. 20%), parity (first vs. second lactation or later), and breed (Holstein vs. Jersey) on the reproductive efficiency of dairy cows. Sixty-four cows were blocked by parity and breed and assigned to one of two treatments. Cows were removed from treatments on d 100 or 120 depending on pregnancy status. Cows were categorized by health status based on the occurrence of postparturient disorders. Plasma urea N concentrations were influenced by diet (8.6 vs. 21mg/dl, 13 and 20% CP, respectively), parity, and breed. Reproductive indices were not influenced by diet except that days to first estimated ovulation increased for cows fed the 20% CP diet when health status was added to the model. Days to first observed estrus, first AI service, and cumulative pregnancy rate were affected by health status. Regression analysis for survival showed an interaction of diet and health status for days open. High CP diets tended to increase days open when cows had major health problems; otherwise, a high CP diet decreased days open. The implementation of a strict reproductive management program allowed high reproductive efficiency goals to be achieved regardless of plasma urea N concentrations.

The effects of dietary crude protein on growth of the Eurasian perch Perca fluviatilis

A 73-day feeding experiment was conducted to evaluate the effects of dietary crude protein level on growth of Eurasian perch juveniles. Determination of the protein requirement of 2.9 g perch was performed with six semi-purified diets containing crude protein levels ranging from 0 to 60%. Fish were held in three recirculated systems, each diet being tested in triplicate. Significant differences in growth and survival appeared among fish fed diets containing up to 30% crude protein and fish fed diets from 40% crude protein and above. Three mathematical models (the four parameter saturation kinetics, broken line and second order polynomial Brett model) were used to analyse the relationships between dietary crude protein and specific growth rate. According to the saturation kinetics and polynomial models, the optimum dietary crude protein levels were 36.8 and 43.6%, respectively. Based on broken line and polynomial models, maximum growth occured at 43.1 and 56.5%, respectively. Endogenous protein losses of 2.9 g juvenile perch reached 1.11 mg fish −1 day −1 at 23 °C.

Carry-over effects of dietary crude protein and triiodothyronine (T3) inbroiler chickens

Indian River male broiler chickens growing from 7 to 30 d of age were fed on diets containing crude protein levels ranging from 120 to 300 g/kg plus 0 or 1 mg triiodothyronine (T3)/kg diet. The purpose of this study was to examine the effects of these treatments on lipogenesis after a common diet was fed (180 g crude protein/kg diet from 30 to 56 d of age). Dietary treatment groups were sampled at 30 and 56 d. In vitro lipogenesis was determined by incubating liver explants for 2 h at 37 degrees in Hanks' salts containing 25 mM-HEPES and 10 mM-[2-14C]acetate and then measuring acetate incorporation into total lipid. Growth and feed consumption from 7 to 30 d increased (P < 0.01) as dietary protein increased from 120 to 210 g/kg diet. Both measurements decreased as crude protein increased from 210 to 300 g/kg diet. T3 decreased (P < 0.01) growth and feed intake during this period. Low-protein (< 180 g/kg) diets increased (P < 0.05) and T3 decreased lipogenesis in 30-d-old chickens. Although birds given T3 from 7 to 30 d grew at the greatest rate from 30 to 56 d of age, the final body weight was still less than controls. In vitro lipogenesis at 56 d of age was not affected by either of the two dietary treatments. In contrast, the relative size of the abdominal fat pad (g/kg body weight) at 56 d was decreased by feeding T3 from 7 to 30 d. Any changes in metabolism elicited by either dietary protein levels or hormone treatments may be specific to the particular dosing interval and are not sustained when a common diet is fed during a repletion period.

The Effect of Dietary Crude Protein as Protected Soybean Meal on Mammary Metabolism in the Lactating Dairy Cow

Metabolism in the mammary gland was related to changes in milk output in response to changes in dietary protein intake. Three diets of grass silage and concentrate were fed to four lactating dairy cows equipped with intravascular catheters across the mammary gland. Concentrates differed in the inclusion of protected soybean meal and provided 11.3, 15.4, and 20.1% CP, respectively. Blood samples were taken to assess the effect of protein percentage on the nutrient fluxes across the gland and their relationship to milk production. Milk production, milk protein yield, and milk protein concentration were all increased as CP intake increased, although these responses were not linear. Concentrations of urea in milk reflected those in plasma and increased as dietary protein intake increased. Uptake of glucose and BHBA by the mammary gland tended to increase as milk production increased. Arterial supply of essential AA increased as the dietary protein increased. Supply and uptake of nonessential AA were unchanged by dietary treatment, and uptake was insufficient to account for output of nonessential AA residues in milk protein. The supply of essential AA was not limiting for milk protein synthesis, and some alternative mechanism must have existed for the control of milk protein yield.

Effects of Dietary Protein Level on Carcass Composition of Broilers at 5 to 15 Days of Age.

Few reports have been available concerning the relationship between dietary protein level and body composition of broilers at starting stage (0-3 weeks of age) under the same metabolizable energy (ME) condition. Preceding determination of the amino acid requirement of broilers using body weight gain as a main criterion, the effects of dietary crude protein (CP) on the carcass composition of broilers were studied.To the experimental diets mainly consisting of corn, whole egg protein was added as a good protein source to contain 3, 200 kcal ME/kg and 6 levels of CP from 12.1 to 21.1% arithmetically. Five broilers for each diet were fed ad libitum the experimental diets from 5 to 15 days of age after nutritional effects of yolk sack decreased. On the 15th day, they were sacrificed after recording the body weight and feed consumption, and mois-ture, fat, protein and ash contents of the carcass were determined. The body weight gains reached the maximum level at 16.2% CP and the feed efficiency reached the maximum level at 15.0% CP. Percentage of the carcass moisture (Y1), protein (Y2) and ash (Y3) increased linearly and, to the contrary, that of fat (Y4) decreased linearly with increasing the dietary CP level as follows: Y1=0.284X+61.27(r2=0.658) Y2=0.236X+11.50(r2=0.606) Y3=0.266X-0.86(r2=0.939) Y4=-0.786X+28.09(r2=-0.935) where X is percentage of the dietary CP.The highest ratio of retained protein, to ingested one was 71.9% at 14.9% of the dietary CP level and that of retained energy to ingested one was 52.6% at 14.9% of the dietary CP level.The contents of the digestive tracts increased with increasing the dietary CP level and body size. However, they did not affect the estimation of the requirements.

Effect of Dietary Crude Protein and Metabolizable Energy Levels on the Performance of Laying Hens.

The present experiment was conducted to determine the extent the performance of young laying hen was affected by dietary crude protein (CP) and metabolizable energy (ME) levels, preceeding a series of experiment to determine the requirement of each essential amino acid.Seven hundred twenty pullets of a commercial strain were housed two birds per cage in an open convention-ventilated laying house and fed twelve diets ad libitum from 150 to 255 days of age. Three replicate (240 birds per replicate) were involved. Mean daily temperature ranged from 15° to 25°C during the experimental period. Experiment had a 4×3 factorial arrangement of treatment with four levels of CP and three levels of ME.The diets were formulated for methionine, lysine and tryptophan to reach 85, 95, 105 or 115% of the NRC recommendations and contained graded levels of dietary ME (2, 700, 2850 and 3, 000 kcal/kg).Significant diet differences for feed intake, egg production, egg weight, egg mass, body weight gain and feed conversion ratio were noted. Increasing the dietary energy resulted in reduced feed intake and a general tendency to increase energy intake. But feed consumption was not affected by dietary CP levels. Increasing the protein level of the diet resulted in increased protein intake but had no effect on energy intake. Throughout the whole experimental periods, egg production increased with increasing CP levels. The egg production rate was not affected by ME level till 192 days of age, but it tended to decrease with increasing ME level after that age. Egg weight increased with age on all diets. It increased with increasing CP level until 234 days of age, but was not affected by ME level throughout all experimental period. Since egg weight increased with age on all diets and egg production rate increased with increasing CP levels, egg mass also increased with age and by CP levels in the similar way as egg weight and production rate. As protein and energy levels increased, efficiency of feed utilization increased.The present study showed that the CP level which maximized hen performance was 14.5% or more across all ME levels and on the protein requirements of laying hens indicated that for maximum production of about 90%, hens required about 18 grams of protein per day. Present experiment also have suggested that in a moderate environmental temperature (from 15° to 25°C) ME levels of 2, 700-2, 850 kcal per kg diet might give economical results. The daily energy requirement of the hens for maximum production of about 90% ranged from approximately 310 to 330 kcal ME per day.

Effects of Dietary Crude Protein, Electrolyte Balance, and Photoperiod on Growth of Broiler Chickens

Three experiments were conducted with broiler chicks to study the effects of dietary electrolyte balance, dietary crude protein level, and photoperiod on performance. Increasing the electrolyte balance (Na +K −Cl) from about 200 meq/kg to 350 meq/kg or more improved gain and feed consumption of chicks fed high protein (28.6%) diets but depressed gain and feed consumption of chicks fed low protein (14.3%) diets. Neither sex nor photoperiod affected to nature or magnitude of the crude prtoein × electrolyte balance interaction, although birds housed under 16L:8D had significantly higher concentrations of plasma ammonia than did those housed under 23L:1D. Chicks fed diets containing a high vs. a low electrolyte balance had significantly higher concentrations of plasma uric acid and significantly lower kidney asparaginase activities. Electrolyte effects on kidney asparaginase activity were not affected by diet crude protein content. Results indicate that the electrolyte balance that provides for optimum growth is dependent upon dietary crude protein concentration. Further, diet electrolyte effects on metabolic acid-base homeostasis are not related to their effects on growth.

The effect of dietary protein and energy content on growth rate and feed utilization of the African catfish Clarias gariepinus (Burchell 1822)

Twenty semi-purified diets were formulated to investigate the effect of dietary crude protein and metabolizable energy content on growth rate and feed utilization of the African catfish Clarias gariepinus (Burchell 1822). The feeding experiment was performed at two temperatures (24 and 29°C) and lasted 12 weeks (three periods of 4 weeks each). Mean initial fresh body weight was about 40 g ( N = 1200). Growth rates were highest in the first period and subsequently decreased in the middle and last period at both temperatures, irrespective of crude protein and metabolizable energy intake. Feed conversions were best in the first period. Optimal intake levels of crude protein and metabolizable energy were higher at 29°C than at 24°C. The optimal amount of crude protein intake per unit of metabolizable energy intake with respect to growth rate was about 25.4 mg·kJ −1 at 24°C. At 29°C this amount was about 34.7 mg·kJ −1. The results indicate that the requirements of the African catfish with respect to crude protein and metabolizable energy are comparable to those of other omnivorous fish species. These requirements are higher at higher temperatures, while younger fish utilize their feed with a higher efficiency than older fish.