Early feed restriction of broilers: effects on abdominal fat pad, liver, and gizzard weights, fat deposition, and carcass composition

Avian Liver: The Forgotten Organ

Simple Summary

The liver is a multi-purpose organ, with involvement in bile secretion, and lipid, carbohydrate and protein metabolism, as well as a number of other metabolic functions. This organ can adapt easily to changes in feed and the environment. Being at the centre of a number of digestive, metabolic and productive activities, it is essential to have a better understanding of this organ and the factors affecting liver functionality.

Abstract

Despite having huge responsibilities in avian species, published reports on the influence of dietary factors and other possible constraints on the size, development and function of liver are limited. Consideration of the factors that could influence and alter liver function is therefore of critical relevance. In the current review, aspects of liver structure and function, and the influence of feed restriction, anti-nutritional factors, structural components and feed additives on liver are discussed. Effects of feed technology techniques such as thermal treatment and pelleting, feed particle size and whole grain feeding on the liver are also reviewed. A discussion of lipogenesis and lipid storage in poultry is presented to provide a better understanding and to differentiate the normal pathways of lipid metabolism from abnormal (i.e., disordered) pathways. The liver is the main site of fat synthesis in poultry, but under certain conditions, excessive fat can accumulate in the liver and cause problems. Factors contributing to the fatty liver syndrome are also examined.

Benefits of caloric restriction in the myenteric neuronal plasticity in aging rats

Aging is a biologic process characterized by progressive damage of structures and functions of organic systems. In gastrointestinal tract, it can involve enteric nervous system, which plays an important role in digestion and absorption of nutrients, causing hastening of intestinal transit thus reducing its absorptive function. Caloric restriction has been used in several studies with the intention of delaying deleterious effects of aging. This study aimed to evaluate the effects of caloric restriction on myenteric neurons of ileum by aging in rats. 30 Wistar rats were grouped as follows: GI (animals aged 6 months fed with normal diet), GII (animals aged 18 months fed with normal diet) and GIII (animals aged 18 months subject to 31% of caloric restriction). The rats of the GI group were euthanized at 6 months of age and after experimental period of 12 months animals of the group GII and GIII were euthanized, the ileum of all groups were collected, measured and processed by NADPH-dp and Acetylcholinesterase. Quantitative analysis of neurons revealed that aging promotes the increasing of myenteric neurons NADPH-dp and reduces Acetylcholinesterase neuronal population. However, in the cellular profile area, were not observed significant differences between the groups. The caloric restriction has been efficient and can be used preventively because it minimizes quantitative changes associated with aging on ileum myenteric plexuses.

Effect of Two-step Time-restricted Feeding on the Fattening Traits in Geese

The present study was conducted to determine whether the two-step time-restricted feeding improves the fattening traits of one-step time-restricted feeding in geese. Thirty-six 8-wk-old geese were allotted into one of three groups. Group R1 (the 1-step restricted feeding group) was allowed access to feed for 2 h in the morning from 8 wk to 14 wk of age. Group R2 (the 2-step restricted feeding group) was treated as Group R1, but was additionally fed for 2 h in the afternoon from 12 wk to 14 wk of age. Group C (the control group) was fed ad libitum from 8 wk to 14 wk of age. Feed intake and body weight (BW) were recorded daily and weekly, respectively. At 14 wk of age, the blood samples were collected to determine the fasting plasma levels of glucose, triacylglycerols and uric acid before sacrifice. The results showed that daily feed intake (DFI) was lower, feed efficiency (FE) was higher in both Groups R1 and R2 than in Group C, and daily gain (DG) in Group R2 was higher than in Group R1 during the whole experimental period (p<0.05). Group R1 exhibited lower abdominal and visceral fat weights in carcass than did Group C (p<0.05), and Group R2 was in intermediate. The fasting plasma glucose levels in Group C were higher, and triacylglycerol levels in Group R1 were higher, compared with the other groups (p<0.05). It is concluded that time-restricted feeding in the fattening period not only increases FE but reduces DFI, and the additional meal during the late fattening period improves the DG without the expense of FE in geese.

Quantitative feed restriction from 35 to 42 days of age for broiler chickens

The objective of this study was to evaluate the effect of increasing levels of feed restriction in broilers aged from 35 to 42 days, on the performance, carcass parameters and intensity of lesions at slaughter. A total of 1,225 one-day old chicks were obtained from a commercial hatchery and were grown over a 34-days period (five weeks). At 34 days of age all birds were weighed and redistributed into a completely randomized design to perform the following treatments: control (0% feed restriction), 10, 20, 30 or 40% feed restriction. The amount of feed given to animals was adjusted daily according to the previous day's intake of the control treatment. At 42 days, birds were weighed and two birds per pen were slaughtered, one to evaluate carcass yield and cuts and the other for body composition analysis. Weight gain and feed intake were decreased linearly (p<0.05) according to increasing levels of restriction, while the feed:gain ratio showed a quadratic effect (p<0.05). The hot eviscerated carcass weight decreased linearly (p<0.05) according to increasing levels of restriction, without effects on the carcass, breast and thigh yield. The dry matter and fat of the carcass decreased and the crude protein increased (p<0.05), according to levels of restriction. We conclude that feed restriction of 2.5% in the last week of life can improve the feed efficiency of poultry, when there is a higher accumulation of fat in the carcass.

Effect of early feed restriction on hepatic lipid metabolism and expression of lipogenic genes in broiler chickens

The study was conducted to investigate the effect of early feed restriction (ER) on lipid metabolism and mitochondrial function in the liver of broiler chickens. Newly hatched broiler chickens were randomly allocated into control and ER group which was subjected to feed restriction with feed provided on alternate days from hatch to 14 days of age (14 d), followed by ad libitum feeding until the end of the experiment on 63 d. ER group exhibited significantly lower body weight throughout the experiment. Serum concentrations of total cholesterol (TC) and high density lipoprotein cholesterol (HDLC) were significantly higher in ER group at 14 d (P<0.05), and the higher serum TC level in ER group was also observed at 63 d. In contrast, the contents of triglyceride (TG), TC and lipoprotein lipase (LPL) activity in liver were significantly lower in ER group at 14 d (P<0.05). At 14 d no significant difference was detected for the mRNA expression of the acetyl-CoA carboxylase-α (ACC-α), carnitine palmitoyltransferase I (CPT-I), sterol regulatory element binding protein-1c (SREBP-1c) or peroxisome proliferator-activated receptors α (PPAR-α) between control and ER group. At 63 d ACC-α mRNA expression was significantly down-regulated accompanied with a significantly up-regulated CPT-ImRNA and a decreased tendency of SREBP-1c mRNA expression in ER group (P=0.09). Swollen mitochondria with fragmented and reduced cristae were observed in liver of ER group at 14 d. Meanwhile the inner mitochondria membrane viscidity increased and hepatic mitochondrial superoxide dismutase (SOD) activity decreased at 14 d. The results suggest that feed restriction at early postnatal stage may produce long-term effect on lipid metabolism of broiler chicken, probably through, at least in part, alterations in mitochondria morphology and function.

Effect of Refeeding on Growth, Development, and Behavior of Undernourished Bank Swallow (Riparia Riparia) Nestlings

Nestlings of aerial insectivores adjust their energetics, behavior, and development of internal organs in response to food shortages and subsequent improvements in feeding conditions. Here, we present results of laboratory refeeding of Bank Swallow (Riparia riparia) nestlings, which were undernourished between 4 and 7 days of age. During a subsequent three-day-long refeeding, their body mass did not catch up with that of individuals continuously fed ad libitum. However, refed young managed to compensate for delayed growth of pectoral muscles, small intestines, and fully restored fat reserves. Their resting metabolic rates and body temperatures increased to values similar to those of nestlings fed ad libitum. In contrast, digestive activity of their guts (quantified as carrier-mediated intestinal brushborder uptake rate of L-proline) was reduced, as compared with the period of undernutrition. Likewise, high locomotor activity observed during food shortage was significantly reduced upon refeeding. Furthermore, differences in body mass between nest mates, which had earlier modulated both locomotor activity and physiological responses to food shortage, had no effect on mobility and physiology of refed nestlings. Our results indicate that even a short, three-day period of refeeding triggered conspicuous acceleration of growth and development of vital internal organs in previously undernourished nestlings. However, that was not accompanied by significant compensatory whole-body growth (defined as a period of above-normal rapid growth, relative to age).

Quantitative and qualitative feed restriction on growth characteristics of male broiler chickens

Four experiments were conducted to evaluate the quantitative and qualitative feed restriction on the performance of male broiler chickens. In the first experiment, broilers fed identical pelleted diets were feed-restricted from 5 to 42 d by giving 95, 90, or 85% of the feed consumed ad libitum by control birds the previous day. In a second experiment, broilers were fed pellet or mash diets from 1 to 7 wk. In Experiments 3 and 4, broilers were feed-restricted to 90% of the ad libitum intake of a control group during different intervals. Results from Experiment 1 indicated that live body weight at 42 d was significantly different between unrestricted and restricted broilers (P < 0.01). A reduction in mortality was noted when feed intake was reduced (P < 0.05). In the second experiment, broilers fed mash had lower body weights and breast meat yields at 42 and 49 d (P < 0.05). Cumulative mortality at 42 and 49 d was reduced in broilers fed mash (P < 0.05). Results from Experiment 3 indicated that body weight and mortality were not significantly different (P > 0.05) at 42 d across treatments. There was a significant (P < 0.01) linear improvement on feed conversion at 42 d due to duration of feed restriction. Breast meat yield at 42 d was less in broilers subjected to mild feed restriction (P > 0.05) (Experiments 3 and 4). Broilers appeared able to recover from mild feed restriction, and there was always an associated reduction in mortality.

Early and temporary quantitative food restriction of broiler chickens. 1. Effects on performance characteristics, mortality and meat quality

1. An experiment was conducted with broiler chickens to determine the effects of different early food restrictions, strain (Ross 508 and Hybro G) and sex on performance, mortality carcase composition and meat characteristics. 2. Birds were restricted to 80% or 90% of ad libitum intake for 4 d (80%-4 d-group and 90%-4 d-group, respectively) or 80% for 8 d (80%-8 d-group). All restrictions started on d 4. After the periods of restriction, all birds were fed ad libitum. 3. Only the 90%-4 d-group reached a final body weight not significantly different from, but lower than, the ad libitum group. The other restrictions were too severe to allow a sufficient 'catch-up'. 4. No significant differences in food conversion and total carcase fat content between groups were observed. Abdominal fat showed a tendency to increase due to the restrictions induced. 5. There was a slight trend towards a reduced mortality and of 'sudden death syndrome' but no clear effect of food restriction on number of chickens removed with leg problems. There was no significant decrease in uniformity of the flocks due to restriction. 6. The group 80%-8 d had a significant lower yield percentage. Cut-up parts and meat quality were not changed by restriction. Ross birds had a significantly higher proportion of breast meat than Hybro chickens. Meat of female chickens seemed to be paler than that of males, possibly because of the higher proportion of carcase fat. 7. Food restriction did not always give good results. However, a mild restriction (90% for 4 d) may offer some economic advantages over an ad libitum feeding regimen, mainly by reducing mortality.

Early and temporary quantitative food restriction of broiler chickens. 2. Effects on allometric growth and growth hormone secretion

1. An experiment was conducted with male broiler chickens to investigate the effect of different early food restriction programmes on proportional weights and allometric growth coefficients of carcase parts and on pulsatile growth hormone secretion. 2. At 4 d of age the animals were restricted to 80% or 90% of the ad libitum intake for 4 d or 80% for 8 d. When the restriction was finished, all birds received ad libitum food again. 3. On d 1, 8, 11, 14, 21, 28, 35 and 42, from each group 8 birds were weighed, stunned and killed and the weights of the stomachs, liver, heart, sternum, right thigh, right drumstick, breast and abdominal fat pad were determined. On d 29, 30, 31, 32 serial blood samples of 2 birds from each group were taken to determine the plasma growth hormone (GH) content. 4. Only the most severe restriction resulted in a tendency for the stomachs to mature earlier and the thighs to mature later. No other significant effect on the allometric coefficients could be observed. 5. It is concluded that during the restriction the birds give priority to the development of the supply organs such as the stomach, which are more important during early development at the expense of the demand tissues like breast and thigh. 6. No significant differences concerning the GH secretory parameters could be observed.

Effect of dietary aminoguanidine on tissue pentosidine and reproductive performance in broiler breeder hens

Factors influencing the age-related decline in production parameters of broiler breeder hens are poorly understood. Elevated blood glucose concentrations measured in broiler breeder hens may contribute to this decline. The nonenzymatic attachment of glucose to proteins generates glycoxidation crosslinks in tissue proteins, which can ultimately impair their function. One such glycoxidation crosslink, pentosidine, has been used as a biomarker for aging studies because of its accumulation on the structural protein collagen. The objectives of these studies were to determine whether pentosidine accumulates with age in hens and whether the crosslinking inhibitor, aminoguanidine (AG), could retard this accumulation. An additional objective was to determine whether AG had any effect on production performance. In the first study, broiler breeder hens (n = 318) were randomly assigned to two groups: control and supplemented (400 ppm AG). Pentosidine was measured in the skin of the birds at 20 and 67 wk of age. Egg production was measured daily. In a second study, broiler breeder hens (n = 60) were reared as previously described. Pentosidine was measured in the skin of the birds at 20 and 68 wk of age. Results showed that pentosidine was present in the skin of the hens, and that concentrations increased with age (P < 0.001). Although pentosidine was reduced (P < 0.001) in AG-supplemented birds, production performance was not affected. In conclusion, AG retarded the rate of accumulation of pentosidine during lay in broiler breeder hens, but the reduction in pentosidine did not significantly affect production performance.

The effect of early feed restriction on broiler performance

In an attempt to determine the effect of early feed restriction on broiler performance, nine trials were conducted. Feed restriction was based on previous 24-h feed consumption values of the full-fed control groups. Feed restriction was from either 7 to 14 d of age (Trials 1 to 5) or 8 to 16 d of age (Trials 6 to 9). The treatments for Trials 1 to 5 were 90, 75, and 60% of previous 24-h feed consumption of full-fed controls. The treatments for Trials 6 to 9 were 80 and 60% of previous 24-h feed consumption of full-fed controls. Early feed restriction did not affect abdominal fat. Early feed restriction did improve feed conversion (grams of feed:BW). Males and females equated at 41 d of age for an 8% reduction (90% feed restriction) at 14 d of age when compared with full-fed control broilers. Neither females or males could overcome a 17 or 18% weight reduction (75% feed restriction) at 14 d of age by 41 d of age. At 48 or 49 d of age, both males and females could equate in weight with full-fed control broilers for a weight reduction of 27 and 31% (60% feed restriction) at 16 d of age. Mortality or deformed legs did not differ between any of the comparisons.

Effect of early nutrient restriction on broiler chickens. 1. Performance and development of the gastrointestinal tract

An experiment was conducted to determine the effects of early nutrient restriction on performance and development of the gastrointestinal tract of broiler chickens. Four hundred male broiler (Ross x Ross) chicks raised in floor pens were assigned to two treatment groups. One group was given ad libitum access to feed from 1 to 48 d of age. The second group was feed restricted from 7 to 14 d of age to an energy intake of 1.5 x BW.67 kcal ME/d and then given ad libitum access to feed from 14 to 48 d. Body weight and feed intake were determined weekly. At 49 d of age, birds were processed for carcass yield, abdominal fat pad measurement, and body composition analysis. Broilers were also sampled at 7, 14, 21, and 41 d of age for proventriculus, gizzard, small intestine (duodenum, jejunum, and ileum), pancreas, and liver weights and for intestinal length measurements. Total DNA, protein:DNA, and RNA:DNA ratios of livers and jejuna were determined as indexes of changes in cell size and number. Feed-restricted broilers failed to catch up to the Control birds in BW at 48 d of age but were superior (P < .01) in overall feed efficiency. No treatment effects were observed on breast meat yields or abdominal fat. Moreover, percentage carcass fat, crude protein, ash, and dry matter were not affected by restricted feeding. Body weight and weights of gastrointestinal organs were reduced (P < .01) by feed restriction at 14 d of age. Restricted feeding, however, did not decrease the relative weights of organs, except for liver. Feed restriction also resulted in a reduction (P < .01) of liver cell number and size and a decrease in jejunum cell number. All organs recovered normal weight on refeeding, and all cellular constituent ratios (e.g., RNA:DNA, RNA:protein, and protein:DNA) returned to normal by 41 d of age. Absolute and relative weights of supply organs (e.g., proventriculus, gizzard, small intestine, liver, and pancreas) were less affected by feed restriction and responded more quickly to refeeding than the whole body.

Weight of internal organs and carcase yield of early food restricted broilers broilers

1. Effects of food restriction on growth rate and relative growth rates of supply organs (liver, heart, lungs and kidneys, digestive tract) and demand organs (breast, back, thighs, abdominal fat) of broiler chickens were studied. 2. Birds were restricted in intake to 50% (group FI 50) or 75% (group FI 75) of ad libitum from 5 to 11 d of age; all birds were fed ad libitum from 12 to 39 d of age. 3. Relative growth rates from 12 to 39 d of age of group FI 50 were higher (P < 0.05) than group FI 75 and control group. 4. No significant differences in food conversion ratio, carcase fat and abdominal fat between groups were observed. 5. At 12 d of age, relative weight of the empty digestive tract of group FI 50 was higher (P < 0.05) than that of the control group and group FI 75. 6. The increased weight of the empty digestive tract may have contributed to the ability of the chickens to achieve compensatory growth after the restriction period.