Changes in body composition and adipocyte cellularity of male broilers subjected to varying degrees of early-life feed restriction

Three experiments were conducted to determine growth performance, body composition changes, and adipocyte characteristics of male broilers subjected to early-life feed restriction. The purpose of Experiment 1 was to determine 42-d growth performance and body composition changes. Treatments used were full-fed control and 50% physical feed restriction during the period 6 to 12 d of age. Experiment 2 was conducted to determine the adipocyte characteristics during and after feed restriction to 42 d of age. An additional treatment involved gradual refeeding following the feed restriction period. Experiment 3 was designed to test the effect of feeding different types of dietary fat during realimentation on the abdominal fat pad (AFP) size, and lasted until 18 d of age. Three types of fats were tested, namely animal-vegetable (A-V) blend, flax oil, and animal tallow, each represented by full-fed and feed-restricted treatments. Complete compensatory growth by feed-restricted birds relative to controls was not achieved by 42 d in either Experiments 1 or 2. Early feed restriction resulted in lower body fat percentage at 12 d (P < 0.05), although by 42 d a higher rate of fat deposition mainly by hypertrophy of adipocytes resulted in no difference in fatness. Gradual reintroduction into ad libitum feeding did not alter such adipocyte hypertrophy nor improve compensatory growth response during refeeding. There was consistent improvement in feed efficiency associated with early-life feed restriction (P < 0.05). The use of different types of dietary fat did not effect the AFP when expressed as percentage body weight. Birds that were fed A-V blend during the refeeding period had bigger AFP (grams per bird), a situation that is attributable to differences in body weight. Attainment of growth compensation by the feed-restricted broilers apparently requires a more prolonged growth period or a less severe feed restriction program than that used here. Saturation of dietary fat has no effect on realimentation characteristics of the broiler.

Broiler response to diet energy

Male broiler chickens were fed corn-soybean diets providing 2,700, 2,900, 3,100 or 3,300 kcal ME/kg. In all experiments, each treatment was tested with three replicate groups of 30 birds grown to 49 d of age. In Experiment 1, birds consumed the various diets ad libitum whereas in Experiment 2, all birds received identical and restricted quantities of feed so as to ensure variable intakes of energy. In a third experiment, after 7 d of age, broilers had access to feed in two feeders that contained only the highest level of energy, or the 3,300 kcal ME/kg diet in combination with one of the other diets previously described. Providing diets of 2,700 to 3,300 kcal ME/kg for ad libitum consumption had no effect on growth rate (P > 0.05) and energy intake was constant; however, reducing the energy level of the diet did result in reduced carcass fatness (P < 0.01). When feed intake was controlled in Experiment 2, there was reduced growth (P < 0.01) rate as energy level of the diet was reduced. This reduced growth was associated with dramatic reduction in carcass fatness (P < 0.01), although breast meat yield was not affected. When broilers were offered a choice of diets, they showed remarkably precise control of intake, such that energy intake was again constant across all treatments. However, even though energy intake was constant, broilers consuming the choice diets involving the lower energy content diets tended to have less carcass fat. It is concluded that the broiler still possesses a good ability to control its feed intake based on desire to normalize energy intake. As energy intake is decreased, or there is increased protein intake, the bird deposits less carcass fat.

Broiler response to energy or energy and protein dilution in the finisher diet

Two experiments were carried out with male broiler chickens in which diets from 35 to 49 d of age were diluted by oat hulls and sand. In one experiment only energy was diluted; in the second experiment, both energy and protein (amino acid) levels were affected. Each diet was tested with four replicate floor pens each containing 25 1-d-old birds. All birds received a standard starter diet to 16 d and then grower diet to 35 d. In Experiment 1, dilution of only energy resulted in a significant linear (P < 0.01) reduction in body weight at 42 d, although there was growth compensation after this time such that all birds weighed the same at 49 d. Diet energy dilution resulted in increased feed intake, although energy intake was not maintained (P < 0.01). Diet energy dilution generally had little effect on carcass weight or yield of breast meat, although there was less abdominal fat (P < 0.01). In Experiment 2, dilution of both energy and protein had a comparable effect on growth rate as described in Experiment 1; however, in this study there was a linear decrease in carcass weight and breast meat yield as the diet was diluted. These results suggest that the male broiler chicken can grow quite well on very low energy diets but that a period of at least 7 d is required for adjustment to feed intake. Even with compensatory increase in feed intake, however, the bird is unable to maintain its energy intake when fed such diluted diets.

Utilization of fats and fatty acids by turkey poults

Two experiments were carried out with young, Large White male turkey poults maintained in either floor pens or metabolism cages. In Experiment 1, poults were fed isoenergetic diets containing either no supplemental fat, or 5% of either tallow, corn oil, soybean oil, animal-vegetable blend fat, or canola oil. Poults generally ate less of the fat-supplemented diets and showed improved feed utilization, although weight gain was little affected. There was improved fat retention when vegetable oils were used (P < .01) and this was reflected in a slight improvement in diet energy level (P > .05). Poults fed tallow or animal-vegetable blend fat also excreted most fat. Diet had no effect (P > .05) on apparent retention of calcium or phosphorus, although retention of magnesium was less with more saturated fats. In Experiment 2, poults were fed diets containing palmitic acid, oleic acid, or a 50:50 (wt/wt) mixture of these fatty acids. There was a reduction (P < .05) in apparent retention of nitrogen, magnesium, calcium, and fat for poults fed palmitic acid, oleic acid, or the mixture. Mixing palmitic acid with oleic acid corrected some of these problems. However, reduced mineral retention was not reflected in any change in levels of bone ash, calcium, or phosphorus. Feeding palmitic acid did result in the most dramatic reduction of bone magnesium content (P < .05). It is concluded that turkey poults, like chicks, are less able to digest saturated fatty acids, and that such undigested fats can lead to reduced retention of some minerals through increased soap formation. However, there is no direct evidence that such soap formation causes a major change in bone calcium or phosphorus content or in gross bone development or poult well-being.

Relation between functional deficit and intraneural local anesthetic during peripheral nerve block. A study in the rat sciatic nerve

BACKGROUND

During peripheral nerve block, local anesthetic (LA) penetrates within and along the nerve to produce the observed functional deficits. Although much is known about the kinetics and steady-state relation for LA inhibition of impulse activity in vitro in isolated nerve, little is known about the relation between functional loss and intraneural LA content in vivo. This study was undertaken to investigate the relation of functional change to intraneural LA.

METHODS

A sciatic nerve block was performed in rats with 0.1 ml 1% lidocaine radiolabeled with 14C. The total intraneural uptake of LA was determined at different times after injection, and the distribution of lidocaine along the nerve was assayed at different stages of functional block. Drug content was also compared with equilibrium lidocaine uptake in the isolated rat sciatic nerve.

RESULTS

Total intraneural lidocaine in vivo increased to near steady-state in about 3 min, stabilizing at approximately 14.3 nmol/mg wet tissue for about 12 min before decreasing to zero at 70 min after injection. Although intraneural lidocaine was 1.6% of the injected dose during full block, only 0.3% was left when deep pain sensation returned and 0.065% was still detected when functions fully recovered. Despite these large differences in total lidocaine content, the longitudinal distribution remained constant. Intraneural lidocaine concentrations obtained at full block and partial recovery could be achieved in vitro by equilibration in 0.7-0.9 and 0.2-0.3 mM lidocaine, respectively.

CONCLUSIONS

During peripheral nerve block only a small amount of injected LA penetrates into the nerve. The intraneural content of LA correlates with the depth of functional block.

Effect of dietary calcium level on plasma proteins and calcium flux occurring during a 24 h ovulatory cycle

An experiment was carried out to determine whether feeding different calcium levels from the onset of production has an effect on medullary bone reserves, plasma proteins and ultimately shell formation. A total of 80 Single Comb White Leghorn hens photostimulated at 17 wk of age were fed a 2.5% Ca diet until the appearance of the first egg. Thereafter diets providing 2.5, 3.0, 3.5, 4.0, or 4.5% Ca were fed to groups of 16 hens. At 6, 12, 18, or 24 h post-ovrposition, blood was collected from four hens per treatment, which were then euthanized and developing shells and bones sampled. As dietary Ca increased, plasma Ca, protein, and protein-bound phosphorus concentrations also increased (P < 0.05). Dietary Ca level had no effect (P > 0.05) on the % Ca or total Ca content of bone ends or medullary bone. As dietary Ca concentration increased, both shell ash and shell Ca increased (P < 0.05). Regardless of dietary Ca, shell secretion was most rapid during 12–18 h of the ovulatory cycle (postoviposition). Key words: Calcium, medullary bone, shell calcification, plasma proteins

alpha-Linolenic acid- and docosahexaenoic acid-enriched eggs from hens fed flaxseed: influence on blood lipids and platelet phospholipid fatty acids in humans

This study was undertaken to examine the effects that consumption of eggs from hens fed diets containing flaxseed would have on plasma and platelet lipids of male volunteers. Feeding diets containing 0%, 10%, and 20% ground flaxseed to Leghorn pullets provided a marked progressive increase in n-3 fatty acid content as alpha-linolenic acid (alpha-LNA) (28, 261, and 527 mg/egg) and docosahexaenoic acid (DHA) (51, 81, and 87 mg/egg) but no alteration in the cholesterol concentration of the egg yolk. Twenty-eight male volunteers, divided into three groups, were fed four eggs per day for 2 wk according to a cyclic Latin-square design. No statistically significant changes were observed in total cholesterol, high-density-lipoprotein cholesterol, or plasma triglyceride concentrations. Significant increases in total n-3 fatty acids and in DHA content (which rose from 1.5 to 2.0% by wt or 33% overall), and a significant decrease in ratio of n-6 to n-3 fatty acids were found in platelet phospholipids of subjects consuming eggs from flaxseed-fed hens. Health and Welfare Canada in 1990 set recommended intakes for dietary n-3 fatty acids and for the ratio of n-6 to n-3 fatty acids, which are not being met currently by the overall population. Eggs modified by the inclusion of flaxseed in the laying hens' diet could provide an important nutritional source of n-3 fatty acid.

D-arabitol metabolism in Candida albicans: construction and analysis of mutants lacking D-arabitol dehydrogenase

Candida albicans produces large amounts of the acyclic pentitol D-arabitol in culture and in infected animals and humans, and most strains also grow on minimal D-arabitol medium. An earlier study showed that the major metabolic precursor of D-arabitol in C. albicans was D-ribulose-5-PO4 from the pentose pathway, that C. albicans contained an NAD-dependent D-arabitol dehydrogenase (ArDH), and that the ArDH structural gene (ARD) encoded a 31-kDa short-chain dehydrogenase that catalyzed the reaction D-arabitol + NAD <=> D-ribulose + NADH. In the present study, we disrupted both ARD chromosomal alleles in C. albicans and analyzed the resulting mutants. The ard null mutation was verified by Southern hybridization, and the null mutant's inability to produce ArDH was verified by Western immunoblotting. The ard null mutant grew well on minimal glucose medium, but it was unable to grow on minimal D-arabitol or D-arabinose medium. Thus, ArDH catalyzes the first step in D-arabitol utilization and a necessary intermediate step in D-arabinose utilization. Unexpectedly, the ard null mutant synthesized D-arabitol from glucose. Moreover, 13C nuclear magnetic resonance studies showed that the ard null mutant and its wild-type parent synthesized D-arabitol via the same pathway. These results imply that C. albicans synthesizes and utilizes D-arabitol via separate metabolic pathways, which was not previously suspected for fungi.

Response of broiler breeders to low-protein diets. 2. Offspring performance

Broiler breeders were allocated at random to one of four experimental diets containing various levels of CP (16, 14, 12, or 10%), at constant methionine+cystine and lysine levels of .59 and .82%, respectively. Diets were isoenergetic and all birds received the same quantity of feed daily to 64 wk of age. Eggs from birds fed 10 and 12% CP were consistently smaller (P < .01) and in two trials involving breeders at 30 and 52 wk of age this resulted in reduced chick weight at hatching, although no lasting effect was observed on weight of offspring at 48 d. Better feed efficiency (P < .05) was observed from broilers hatched from hens fed lower CP diets. These data suggest that it is possible to reduce the CP intake of broiler breeders while maintaining intake of critical amino acids without adversely affecting offspring performance.

Response of broiler breeders to low-protein diets. 1. Adult breeder performance

Four hundred female and 50 male commercial strain breeders were reared separately from 1 d to 18 wk of age, with all birds receiving the same diet. At 18 wk, all pullets were weighed and the extreme weights removed from the group. The remaining hens were then randomly sorted into four treatment groups each represented by four replicate groups. Treatment involved feeding different levels of CP (16, 14, 12, and 10%), supplemented with synthetic lysine and methionine in order to maintain constant lysine and TSAA levels, respectively. Diets were isoenergetic and all birds received the same quantity of feed daily. Dietary protein had no effect on egg production (P > .05). However, breeders fed 10% CP were lighter (P < .01) in weight than birds fed 16% CP. Eggs from birds fed 10 and 12% CP were consistently smaller (P < .01), and this resulted in reduced chick weight at hatching. Low-protein diets also resulted in less nitrogen excretion. These data suggest that it is possible to reduce the CP intake of broiler breeders while maintaining intake of critical amino acids without affecting performance.

Hen performance, egg quality, and the sensory evaluation of eggs from SCWL hens fed dietary flax

Two hundred and twenty-five 19-wk-old Single Comb White Leghorn pullets of a commercial strain were fed diets containing either 0, 10 or 20% ground flax seed. Birds fed 20% dietary flax were smaller and ate more feed (P < 0.01). Hen performance in terms of egg production and egg-shell deformation was unaffected by dietary flax throughout the trial. Egg weight followed this trend until period 12, when control-fed hens laid significantly larger eggs (P < 0.01). The metabolizable energy of diets containing 10 and 20% ground flax was significantly less than that of the control corn-soybean diet (P < 0.01). Malondialdehyde levels in the liver of birds fed 20% dietary flax were moderately elevated, although this was not indicative of serious lipid peroxidation. Percentage liver fat was significantly lower in birds fed all levels of dietary flax (P < 0.05). There was a significant increase of N-3 fatty acids, and particularly linolenic acid, in the livers of birds fed all levels of dietary flax. The data from taste-panel studies involving fresh and stored eggs were somewhat inconclusive, although in general there was a slight perception of off-flavour in eggs from flax-fed birds. Key words: Hen performance, egg quality, dietary flax

Effect of early feed restriction and realimentation on heat production and changes in sizes of digestive organs of male broilers

Two experiments were conducted with broilers to determine the effect of early feed restriction and realimentation on metabolic heat production and changes in sizes of digestive organs. An indirect open circuit calorimeter was used. Treatments were a full-fed control (FF) and a feed-restricted group (FR). Feed during the restriction period (6 to 12 d) for the FR birds was limited to 50% of voluntary feed intake of the FF birds. This was followed by realimentation period when all birds were provided feed for ad libitum consumption. The purpose of Experiment 1 was to measure basal metabolic rate (BMR), and Experiment 2 was designed to measure 36-h fasting metabolic rate (FMR), in both cases during time of restriction and realimentation. At the end of the 36-h unfed period, birds were killed and their digestive organs excised, blotted, and weighed. The FR birds showed significantly (P < .01) lower BMR compared with the FF birds during the restriction period. This lower BMR did not carry over into the refeeding period, when there was no difference between the two treatments. Thirty-six-hour FMR, like the BMR was also lower for FR compared with FF birds, but only during the period of restriction. Weights of digestive organs (expressed as a percentage of BW) during restriction were generally heavier for FR compared with FF birds. Measurements of organ weights taken during realimentation show significantly (P < .05) heavier liver and pancreas for FR compared with FF birds. Results of these experiments suggest that lower MR of "restricted-refed" birds does not play a role in the ability of the birds to show improved feed efficiency and growth compensation. Greater feed intake relative to BW and its associated digestive adaptations seem to be contributing factors to any growth compensation.

Laying hen performance as influenced by protein intake to sixteen weeks of age and body weight at point of lay

White Leghorn chicks were fed corn-soybean meal diets containing 20, 17, 14, and 11% protein, with similar levels of energy, from hatch to 16 wk of age. Body weights at 16 wk were similar for pullets fed the 20 and 17% protein diets, but were reduced by 11 and 27% for birds fed the 14 and 11% protein diets, respectively, as compared with the 20% protein diet. At 16 wk of age, all birds were placed on a common 17% protein laying diet. Pullets fed the 14 and 11% protein laying diets were slightly slower coming into production, however, by 28 wk of age egg production was similar for all four growing treatment groups and remained so until the end of the experiment. Average egg weight was similar for pullets fed the two higher levels of protein during the growing period and significantly lower for those pullets fed the 11% grower diet for all except the 28- and 32-wk periods. Pullets fed the 14% grower diet produced eggs with average weights significantly lower than those for the higher protein diets from 40 to 58 wk of age. Although the results might be interpreted as indicating that higher protein growing diets result in body protein reserves that subsequently enhance egg size, it is more likely that the pullets consuming lower protein diets produce smaller eggs because they have smaller body weights.

Predicting preterm delivery: the fetal fibronectin test

Preterm labour and delivery is a major problem and the leading cause of perinatal death in the UK. At present it is virtually impossible for doctors and midwives to predict when preterm labour is about to start. A new test may help with this problem. It detects the presence of fetal fibronectin in the vagina, which may indicate that the cervix is preparing to begin labour. Although these are early days, the fibronectin test looks promising. It is suitable at present for high-risk patients. Further studies are needed before its use can be justified as a screening test for low-risk women.

Strain comparison of turkey egg components

Two experiments were conducted to quantify the composition of turkey hatching eggs in relation to strain of bird and age of breeder. In one experiment, 20 Nicholas and British United Turkeys of America (BUTA) eggs produced at 3, 12, and 24 wk of production were examined for physical and chemical components. Eggs from Nicholas hens were always some 4 g heavier (P < .05) due essentially to a larger albumen content. Although absolute components increased over time (P < .05), there were few changes in proportional composition (P > .05). Eggs from BUTA turkeys initially contained more yolk protein (P < .05). At 12 and 24 wk of production, eggs from Nicholas hens changed most rapidly and at these ages contained more yolk protein than the BUTA strain eggs (P < .05). At the end of the production cycle, BUTA eggs contained less lipid and protein in the yolk (P < .05). For both strains there was an increase in stearic acid content of yolk lipid with increased breeder age. In a second experiment, comparable studies were conducted on eggs obtained from male and female line BUTA breeding stock. Although male line eggs were heavier (87 vs 78 g), the smaller female line eggs exhibited proportionally more yolk (P < .05), as absolute yolk weight was similar for both strains (22.4 vs 22.5 g). It was concluded that only minor differences exist in components of eggs from different turkey strains.

Effect of varying period of early nutrient restriction on growth compensation and carcass characteristics of male broilers

An experiment was conducted to determine growth and carcass characteristics of male broilers subjected to varying periods of early nutrient restriction. Nutrient restriction was achieved by feeding a starter diet in which the major ingredients were replaced with 50% oat hulls. Five treatments involved feeding this diluted diet for 6 d, either continuous or split into shorter periods in different ways, all starting at 6 d of age. On completion of the 6 d of nutrient restriction, all birds received undiluted starter diet, followed by grower and finisher diets to trial termination at 49 d. All birds fed the diluted diet exhibited reduced nutrient intake. Complete growth compensation by all birds that previously received the diluted diet was attained by 35 d, due largely to their superior (P < .05) feed efficiencies relative to the control birds during realimentation. Varying the period of nutrient restriction did not affect growth compensation. Birds that received the diluted diet for 6 continuous d tended to be leaner at 42 d compared with those that consumed the diluted diet for shorter periods. This latter effect may relate to variable ME intake. There was no statistical difference in other carcass characteristics measured at both 42 and 49 d of age.

Blood, intestinal and skeletal calcium dynamics during egg formation

An experiment was carried out to study the dynamics of various body-Ca pools in the hen during a single ovulatory cycle. One hundred 32-wk-old Single Comb White Leghorn hens were used. For experimental purposes the ovulatory cycle was divided into four periods: 1–6, 6–12, 12–18 and 18–24 h post-oviposition.At 0, 6, 12 and 18 h post-oviposition 25 hens each were intubated proventricularly with 15 μCi of 45Ca as CaCl2 solution. Approximately 1 mL of blood was collected from the leaf brachial vein, and the bird was subsequently placed in an individual cage. Red blood cells, labelled with 15Cr, were re-injected into the same bird from which it was collected. At 0.5, 1, 2, 4 and 6 h post-intubation with 45Ca, blood samples were taken from the right brachial vein of five hens and the birds were immediately killed, carcasses were dissected, the left femur and tibia-fibula were excised, and an egg, if present, was removed. Whole blood was assayed for 51Cr activity, and plasma, bones and shells were assayed for 45Ca activity and Ca concentration.Another five hens were injected in the right brachial vein with 15 μCi of 45Ca immediately following oviposition. Subsequently, the left brachial vein was catheterized and blood was sampled at 0.5, 1, 2, 4, 6, 12, 18 and 24 h post-injection.There were no significant (P > 0.05) differences in blood volume or plasma-Ca concentration for the four periods assayed. Following intubation, plasma-45Ca activity decreased quadratically (P < 0.05) with time for all four periods assayed. Regression analysis showed that the biological half-life of plasma 45Ca was 3.30, 2.13, 1.80 and 1.77 h for periods 1, 2, 3 and 4 respectively. When birds were injected intravenously with 45Ca the half-life of plasma 45Ca was 0.116 h.There were no significant (P > 0.05) changes over time in ash or Ca content of bone ends (BE) or medullary bone (MB). Only MB accumulated 45Ca during the first 6 h of the cycle. There was no difference (P > 0.05) in 45Ca activity of either BE or MB over time in period 2. Only BE experienced a significant (P < 0.05) loss in 45Ca during period 4.There were no differences (P > 0.05) in total shell ash. shell Ca or 45Ca with time in period 1. Shell ash increased (P < 0.05) by 188, 348 and 237 mg h−1 and shell Ca increased by 69, 128 and 82 mg h−1 in periods 2, 3 and 4, respectively. Accumulation of shell 45Ca confirmed that the transfer of Ca was greatest during period 4 of the ovulatory cycle. Using 45Ca dynamics, we estimated that over the entire ovulatory period 1716 mg of Ca was absorbed from the digestive tract and 1704 mg was secreted as shell. Key words: Calcium-45 activity, calcium-45 half-life; plasma 45Ca, bone 45Ca, shell 45Ca, shell secretion, Ca absorption

Age-related carcass composition changes in male broiler chickens

To quantify growth and development of the broiler chicken to 70 d, a flock of male birds was sampled at regular intervals, and observations were made on growth and development of various carcass components. Birds were fed conventional diets and maintained on litter-floor pens in a room with environmental control. At 21, 28, 35, 39, 43, 47, 50, 55, 60 and 70 d of age, 12 birds were selected at random for estimation of live weight, eviscerated weight, cut-up portion composition and deboned meat yield. Observations involved weights of the various carcass components and proximate analysis. Birds showed linear growth to 70 d (P < 0.01), while development shown by the eviscerated carcass was positively quadratic (P < 0.01). Proportional fat content of the eviscerated carcass increased over time (P < 0.01), while protein content decreased (P < 0.01). The leg-thigh portion yielded the greatest quantity of meat, while the bone portion increased from 130 g to 843 g over the 21- to 70-d period. Total carcass skin increased in weight from 50 g to 365 g over the same period. Both deboned breast meat and leg meat increased quadratically over time (P < 0.01). Comparison of results with that developed 10–15 yr ago indicates chronological changes in carcass development. An apparent sporadic increase in yield of breast and thigh meat, which has also been shown by other workers, warrants further investigation. Key words: Broiler, carcass composition, meat yield