The effect of low‐protein grower diets on the subsequent response of pullets to quantitative food restriction during lay

1. The laying responses of pullets fed from 8 weeks of age on a 12.5% protein grower diet and subsequently subjected to food restriction commencing at various times between 20 and 40 weeks of age were compared with those of pullets reared on diets containing 12.5 or 16% protein and given access to food throughout lay.

2. Restricted feeding during lay of pullets reared on the low‐protein diet substantially improved laying performance, the best results being obtained from pullets fed the low‐protein grower diet and restricted from 20 weeks. The laying responses of pullets restricted after peak‐lay at 40 weeks of age were not significantly different from those of birds restricted prior to peak‐lay.

3. Maximal egg production of 81 % over the 48weeks of the experiment was attained on an average daily ME intake of 270 kcal (1130 kJ) and a FCR of 2.06 : 1.

4. It is suggested that food restriction of laying pullets previously reared on low‐protein diets may be successfully utilised prior to peak‐lay provided such restriction is not so severe as to retard the rate of attainment of mature weight and a continued slight gain in weight thereafter.     

Lysine restriction during grower phase on growth performance,blood metabolites,carcass traits and pork quality in grower finisher pigs

Abstract

The effects of lysine restriction during grower phase and realimentation during finisher phase on growth performance, nutrient digestibility, blood metabolites, carcass traits and pork quality were studied. Sixty-four pigs (two castrated males and two females per pen) weighing 34.34±5.22 kg were assigned to four dietary treatments. During grower (35–55 kg), pigs were fed isoenergetic lysine-restricted diets. The different lysine content of diets were 0.950 (NRC recommendation), 0.760, 0.665 and 0.570%, corresponding to lysine restriction of 20, 30 and 40%. Then all pigs were fed with common finisher 1 (55–85 kg) and 2 (85–115 kg) diets. Lysine restriction during the grower phase resulted in poor performance and lower concentration of blood metabolites but improved the nutrient digestibility and efficiency of lysine utilization. Compensatory growth response in terms of improved weight gain and feed efficiency was observed in pigs previously fed lysine-restricted diets during finisher 1, but the concentration of blood urea nitrogen and total protein were lower. No differences in growth performance, digestibility of nutrients and blood metabolites were noted during finisher 2. Lysine restriction of grower diets decreased the dressing percentage (quadratic, P=0.024), and protein content of longissimus muscle (linear P=0.034, and quadratic P=0.009). Thus, it could be concluded that pigs subjected to lysine restriction during grower phase exhibited compensatory growth responses in weight gain and improved efficiency of feed and lysine utilization for weight gain and lean accretion during finisher phase.     

Restricted feeding of broiler breeder pullets during the rearing period and its effect on productivity and breeding

A total of 2000 broiler breeder pullets was used for an experiment comparing two levels of restricted feeding from 6 to 20 weeks with three levels of low‐lysine feeding from o to 12 weeks of age. The object of the experiment was to obtain matching body weights at 20 weeks of age between the two levels of quantitative restriction and the highest and lowest levels of lysine feeding and to compare subsequent biological performance during lay. A control treatment was included in which birds were fed ad libitum at all stages.

Both methods of nutrient restriction reduced intake to 20 weeks of age. From 1 d to 60 weeks of age total food intake was reduced in proportion to the degree of restriction applied during the growing stage.

Sexual maturity was delayed by both methods of restriction, though low‐lysine diets produced a greater delay than quantitative restriction. Production of total eggs and of settable eggs was increased by both quantitative food restrictions and by the least severe of the lysine‐deficient diets. Following quantitative restriction egg size and fertility were both improved, but these advantages were not obtained by lysine restriction.

Mortality and culling were mainly influenced by a high incidence of “rupture of the gastrocnemius tendon “ which occurred exclusively in pullets fed lysine‐deficient diets during rearing.

It is concluded that quantitative restriction is to be preferred because of its advantageous effects on egg weight, rate of lay and fertility, and because it avoids the high mortality rate found with severe lysine restriction.     

Effect of feeding low lysine starters and developers on growth,sexual maturity and subsequent performance of broiler breeder pullets 1

Pullets that were fed diets containing 0.53 per cent and 0.42 per cent lysine grew at a slower rate and matured later than those that were given adequate amount of lysine. The latter pullets converted their food more efficiently than did the restricted pullets with the exception of the group fed the ration containing 0.53 per cent lysine for the first 12 weeks. The restricted pullets consumed less food during the growing period. A smaller bird was produced on less food. The restricted pullets were also lighter than the control pullets at the end of the laying season. A saving in food costs is indicated because the smaller hen would require less food for maintenance.

There was a higher mortality in the pullets fed a ration containing 0.53 per cent lysine during the growing period. The mortality in the group fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age was the same as that of the control. There were no differences in mortality during the laying season that could be related to methods of rearing the pullets.

During the laying season, the highest rate of lay was obtained from hens which had been fed the ration containing 0.42 per cent lysine from 7 to 22 weeks of age. Hens fed on the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks of age showed no improvement in rate of lay as compared with controls.

Hens fed the ration containing 0.42 per cent lysine from 7 to 22 weeks laid fewer small eggs at the beginning of the laying season than did hens receiving adequate amounts of lysine throughout or fed the ration containing 0.53 per cent lysine from o to 4, 8 or 12 weeks. The hens fed the latter ration laid smaller eggs throughout the laying season.

No differences were found between the fertility, hatchability or embryonic mortality of eggs obtained from hens fed on lysine deficient diets during growth and those fed on diets adequate in lysine.     

Reproductive performance of dwarf broiler breeders given different allowances of food during the rearing and breeding periods and two lighting patterns

1. Dwarf broiler breeders were either fed ad libitum or restricted to allow growth to mean body weights of 1.4 or 1.8 kg at 20 weeks of age. During the breeding period these birds were fed ad libitum, or food was restricted to different degrees and the birds subjected to two different incremental lighting patterns. 2. Egg production of birds fed ad libitum during the breeding period increased with the degree of food restriction during rearing. 3. Food restriction during the breeding period increased the egg production of birds weighing 1.8 kg at 20 weeks but decreased that of birds weighing only 1.4 kg. 4. Fertility was relatively low and inversely related to body fatness of females. 5. The differences in lighting pattern did not influence performance. 6. For optimum reproductive performance during the rearing period dwarfs should not be restricted so severely as conventional breeders. Best chick production was obtained from birds with a bodyweight of 1.8 kg at 20 weeks of age, which were subjected to a 10% restriction of food during the breeding period.     

The response of Ross 308 and Hybro broiler chickens to early and late skip-a-day feed restriction

The effects of skip-a-day feeding for 14 days during the starter or grower period or for 28 days during both periods followed by ad libitum feeding to market age on the growth performance of two strains of broiler chickens, Ross 308 and Hybro, were studied over 7 weeks. Ross was superior to Hybro in weight gain, final body weight and feed conversion but consumed more feed. Overall, feed restriction reduced feed intake, weight gain and body weight in all feed - restricted birds. Also, the 14-day feed-restricted birds gained more weight and were heavier than the 28-day restricted ones. Feed restriction neither improved feed conversion nor reduced abdominal fat but decreased mortality rate. Strain | treatment interaction significantly affected only feed intake. It is suggested that for broiler chicken production in the tropics Ross 308 could be used and feed restricted for 14 days during the starter or grower period.     

Lysine restriction and realimentation affected growth,blood profiles and expression of genes related to protein and fat metabolism in weaned pigs

To investigate the effects of lysine restriction and subsequent realimentation on growth performance, blood profiles and gene expression of leptin and myostatin, 128 weaned pigs [initial body weight (BW) 6.96 ± 1.07 kg, 26 ± 2 days of age] were randomly allotted to four treatments. The starter diets during the first 2 weeks (P1) contained 100%, 80%, 70% or 60% of recommended lysine levels ( National Research Council, 1998 ). Then, common grower 1 and 2 diets were offered for 2 weeks (P2 and P3) each. During P1, average daily gain (ADG) was linearly reduced (p < 0.05) with the increasing levels of lysine restriction. Growth rate was greater in pigs previously fed lysine‐restricted diets than well‐fed pigs although it did not reach a significant level during realimentation. However, the final BW and overall ADG were the lowest (p < 0.05) and F/G was poor in pigs fed 60% lysine diet. Relative visceral organ weights and composition of skeletal muscle were similar (p > 0.05) among the treatment. Blood triglyceride and glucose levels were increased (p < 0.05) during P1, while blood urine nitrogen, total protein and albumin levels were decreased (p < 0.05) during P2 with the reduction in dietary lysine levels. The abundance of myostatin mRNA in skeletal muscle and leptin mRNA in subcutaneous adipose tissue were lower (p < 0.05) in lysine‐restricted pigs than in pigs fed non‐restricted diets. In conclusion, 80% and 70% lysine restriction of starter diets resulted in inferior growth and compensatory growth effect was noted during realimentation, while 60% lysine restriction had a negative influence on growth performance. Moreover, the changes in myostatin and leptin mRNA abundance caused by nutritional manipulations may be involved in the regulation of protein and fat deposition in young pigs.     

Effect of age of release from light or food restriction on age at sexual maturity and egg production of laying pullets

1. Lohmann Brown pullets, in one trial, and Hyline Brown pullets in another, were reared from day 2 on short daylengths, and from week 8 in trial 1 (week 16 in trial 2) on food restriction. These restrictions were lifted at various times during the rearing period as a means of determining the relative importance of the day length and food restriction stimuli on the attainment of sexual maturity and subsequent laying performance. 2. A total of 2304 pullets were used in each trial. The birds were reared in light proof rooms, and subjected to 8L:16D until they were moved to a laying facility where a light stimulus of 16L:8D was applied. In trial 1 the six ages at which light stimulation was applied were 115, 122, 129, 136, 143 and 171 d. Within each light treatment, food restriction of pullets, which consisted of feeding 72 g of food/bird d, was lifted at six different ages, namely, 115, 129, 143, 157, 171 and 185 d. In trial 2 both the light stimulation and the lifting of food restriction occured at 111, 125, 139, 153, 167 and 181 d of age, producing 6x6=36 treatments in both trials. 3. The first trial was terminated when the pullets were 28 weeks old, soon after all the birds had commenced laying, because of an outbreak of Egg Drop Syndrome. However, because age at maturity was the variable of major interest, data from this experiment could be used in the analysis. The second trial ended when the birds reached 40 weeks of age. Variables measured were age at maturity, food intake and body weight gain subsequent to the lifting of restrictions and, in the second experiment, rate of lay, peak rate of lay and egg weight at various ages. 4. The mean age at sexual maturity was influenced by the date of release from light restriction (P<0.001) and from food restriction (P<0.001) in both trials. In addition, the interaction between the age at release from light and from food restriction was significant. Regression equations were produced for each trial to describe the relationships between the age at sexual maturity and the age at release from light restriction and food restriction. 5. There was an effect of both light restriction (P<0.001) and of food restriction (P<0.001) on the increase in food intake (g/bird d) in the week following release from food restriction in both experiments. These effects were not independent: the effect of the interaction of light and food restriction on this increase in food intake was also highly significant. The longer the birds were subjected to light restriction, the less dramatic the increase in food intake when food restriction was lifted. The more sustained the period of food restriction, the higher the increase in food intake in the week following release from the restriction. 6. Mean egg weight was 4 g heavier at 22 weeks of age in birds released from food restriction at 16 and 18 weeks, than from those released at 24 and 26 weeks of age. However, by 30 weeks of age, birds restricted for longer produced heavier eggs than their earlier-maturing counterparts. This effect continued to the end of the trial at 40 weeks of age, at which time there was a 2.3 g difference in egg weight between these treatments. 7. Both light and food restriction have an effect on the age of maturity in laying hens. The length of time between the release from light or from food restriction to the onset of laying depended on the age of the pullets when the release occurred. Egg weight at a given age was significantly affected by the age at release from food restriction, but not from light restriction.     

Digestible lysine requirement of starter and grower pigs

Three experiments were conducted to determine the digestible lysine requirement of starter (6 kg BW initially) and of grower (21 kg BW initially) pigs. Experiment 1 used 294 starter pigs and lasted 28 d; Exp. 2 used 182 grower pigs and lasted 35 d. Protein and total lysine contents of the basal corn-peanut meal diets were 20 and .8% for Exp. 1 and 16 and .54% for Exp. 2. Basal diets were fortified with five incremental additions of lysine.HCl to provide lysine contents ranging from .8 to 1.3% in Exp. 1, and .54 to .94% in Exp. 2. Diets contained crystalline tryptophan, threonine and isoleucine (Exp. 1 only) to provide dietary concentrations equal to 18, 70 and 60% of the highest lysine level fed. Average daily gain and gain/feed of both starter and grower pigs increased (P less than .05) linearly and quadratically as dietary lysine level increased. For starter pigs, ADG and gain/feed were optimized at 1.1 to 1.2% total lysine. For grower pigs, ADG and gain/feed were optimized at .86% total lysine. In Exp. 3, barrows fitted with an ileal T-cannula were used in a 4 X 4 Latin square design. Basal diets and diets with added lysine were evaluated. Apparent lysine digestibility of the basal starter and grower diets and lysine.HCl were 79.9, 74.1 and 96.7%, respectively. Based on these values and the total lysine contents found to optimize performance, the digestible lysine requirements of starter and grower pigs are 1.03 and .71%, respectively.     

Effects of restricted feeding in the growing and laying periods on the performance of White Leghorn by Australorp crossbred and White Leghorn strain cross chickens

1. The effects of restricted feeding in the rearing and laying periods on the performance of three White Leghorn cockerel by Australorp pullet crossbred strains and one White Leghorn strain cross were studied in two experiments.

2. After feeding ad libitum in the rearing period, mean body weights of the three crossbred strains at 20 weeks of age were 1.75, 1.66 and 1.55 kg and that of the White Leghorn strain cross was 140 kg. The differing restrictions during rearing reduced mean body weight at 20 weeks by 14 to 33% and increased the time to sexual maturity by 8 to 23 d.

3. All restriction regimes during rearing increased mean egg weight and tended to reduce mortality in the laying period. Optimum hen‐day egg number over 64 weeks of lay was obtained following mild restriction (14% body weight reduction) of the two heavier strains or ad libitum feeding of the lighter strains. Over 48 or 64 weeks of lay, egg number per hen housed (at 18 to 20 weeks of age) was optimised after moderately restricting (14 to 21% body weight reduction) the crossbred strains or feeding the White Leghorn strain cross ad libitum.

4. Over 64 weeks of lay, mortality was reduced from 19.3% to 10.5% in the lightest crossbred strain, in which a high proportion of deaths were associated with Marek's disease and lymphoid leucosis, by restriction during rearing.

5. Restricting food intake by 7 or 8% throughout the laying period reduced hen‐day and hen‐housed egg number and mean egg weight of all four strains. The reduction in hen‐day egg number associated with food restriction during lay was less for the heavier strains that had also been restricted during rearing.

6. Metabolisable energy intakes required to support maximum production over 64 weeks of lay were 1.23 to 1.36 MJ/d.     

Rearing photoperiod and abrupt versus gradual photostimulation for egg-type pullets

1. Lohmann White and Lohmann Brown egg-type hybrids were reared on 6-, 8-, 10- or 12-h photoperiods, transferred to 12.5 h at 18 weeks and then given weekly increments to reach 14 h at 21 weeks. In a second experiment, Lohmann White pullets from the same rearing facility were transferred abruptly to 14 h at 18 weeks. 2. Body weight gain and feed intake to 6 and 18 weeks were positively correlated with rearing photoperiod in both breeds. Mortality to 18 weeks was unaffected. 3. Whether the photoperiod was increased abruptly or in a series of increments, Lohmann White pullets reared on 6 or 8 h matured 4 to 6 d later than pullets reared on 10 or 12 h. Rearing day-length had little effect on sexual maturity in Lohmann Brown pullets. 4. In both genotypes and each experiment, egg numbers, egg weight and shell strength increased with rearing photoperiod. Feed intake in the laying period was not significantly affected by rearing day-length, but a meta-analysis of all data showed a significant, though small, increase in adult feed intake with rearing photoperiod. Despite Lohmann White birds reared on 6 and 8 h having lower body weights throughout the laying period, they had larger body weight gains between 18 and 70 weeks than those reared on 10 or 12 h. There were no clear effects of rearing photoperiod on albumen height or mortality. 5. The heavier eggs and stronger shells of the birds reared on the longer day-lengths were correlated with heavier body weights at 18 weeks, and the superior egg numbers and higher feed intake were associated with age at sexual maturity.     

Effects of low dietary protein and different allocations of food during rearing and restricted feeding after peak rate of lay on egg production,fertility and hatchability in female broiler breeders

1. A 3x2x2 factorial experiment was conducted with boiler breeder females to determine the effects of body weight gain (three levels) and conventional or lower crude protein concentrations in the rations during rearing, and restricted or ad libitum feeding after the peak rate of lay on egg production, fertility, hatchability, mortality and food consumption. 2. Compared with ad libitum feeding, conventional food restriction resulted in a decrease in average daily food consumption of 0.6 during rearing, 0.2 during early lay and an increase of 0.4 after the peak rate of egg production. Mortality was decreased by more than half. 3. Restricted birds had higher total and settable egg production, fewer defective or damaged eggshells and higher fertility and hatchability than those fed ad libitum. The modified (more generous) rearing programme resulted in lower rates of egg production and higher rates of mortality compared with the conventional food restriction programme. 4. Low-protein rearing rations were associated with higher rates of food intake, higher mortalities and lower rates of egg production than the conventional protein rations. There were no differences in the fertility or hatchability of eggs between birds fed on the two concentrations of dietary crude protein. 5. Ad libitum feeding post-peak was associated with higher rates of mortality to 60 weeks of age. Post-peak feeding had little effect on the rate of lay or egg weight in conventionally restricted birds fed high protein rations or in birds fed ad libitum. Restricted feeding post-peak decreased the rate of lay and egg weight in birds on the modified restriction programme and in conventionally restricted birds fed on the low protein rations. There was no effect of post-peak feeding on fertility or hatchability of eggs. 6. The total numbers of saleable chicks per kg food consumed were 1.83, 1.72 and 0.52 for conventional, modified and ad libitum feeding during rearing; 1.56 and 1.15 for restricted and ad libitum feeding post-peak: there were no differences associated with protein concentrations of rations fed during rearing.     

The performance of laying hens fed on rearing and laying diets containing urea

In an experiment using 2880 light hybrid pullets the effect of urea on laying performance has been assessed. Birds received one of three low‐protein rearing diets from 7–20 weeks of age. The control rearing diet, containing 11.5% crude protein, was compared with two diets containing 13.2% crude protein, one in which the protein was from conventional sources and the other containing 11.5% conventional protein and urea equivalent to 1.7% crude protein. At 20 weeks birds were allocated to one of two laying diets formulated to meet essential amino acid requirements. Half the birds from each rearing treatment received a low‐protein diet (14.7%) and the remaining birds received a 16.4% protein diet which included urea equivalent to 1.7% crude protein. Laying performance was recorded for the next 30 weeks.

Body weights of birds fed on the urea‐containing rearing diet were similar to those of birds fed on the control diet (1.22 kg) and less than those on the 13.2% protein diet (1.29 kg). Urea in the laying diet caused a 2% increase in egg production and tended to cause an improved food conversion efficiency. In contrast, a 3.5% less efficient food conversion was found during laying in birds which had received urea during rearing, compared with birds which had received the low‐protein rearing diet. Birds receiving the 13.2% protein diet, containing no urea, during rearing laid smaller eggs than birds fed on the 11.2% protein rearing diet. A high mortality rate occurred during laying due to lymphoid leucosis but no differences between treatments were found.     

Effect of low protein diets for growing Leghorn pullets upon subsequent laying performance

An experiment was conducted with White Leghorn pullets to study the effect on laying performance of dietary protein content and amino acid supplementation during the growing period. From 0 to 6 weeks of age birds fed on diets containing either 149 g protein/kg supplemented with methionine and lysine or 182 g protein/kg grew faster than those fed on a diet containing 149 g protein/kg alone. However, only those fed on the supplemented diet utilised their food more efficiently. From 7 to 20 weeks of age neither body weight gain nor food utilisation was affected by the dietary protein content. Pullets fed the low protein diet supplemented with 2 g methionine/kg and 2.5 g lysine/kg during the period of 0 to 6 weeks of age had significantly better egg production than birds fed the low protein diet alone. The dietary protein content during 7 to 20 weeks of age did not influence subsequent egg production.     

A comparison of three methods of food restriction of laying‐type pullets on growth and laying performance

1. Three methods of restricting the growth rate of pullets from 8 to 20 weeks of age were compared. They were: quantitative food restriction, a diet low in lysine and arginine and a low protein diet.

2. Food consumption up to 20 weeks of age was significantly reduced by all three treatments; mortality was increased and sexual maturity was delayed.

3. Greatest uniformity was observed amongst pullets fed on the low protein and the low lysine diets

4. By 70 weeks there were no significant differences in food conversion based on food consumed between 20 and 70 weeks of age, but based on consumption between 8 and 70 weeks the quantitatively restricted birds converted food most efficiently.

5. The most favourable method of restriction appeared to be the feeding of a low lysine or low protein diet, since rearing costs were low, and the performance of the pullets on these treatments was high.     

Requirement of true ileal digestible threonine of growing and finishing pigs

Ninety-six crossbred barrows and gilts were used to investigate the optimum supply of true ileal digestible threonine for growing (approximately 35-65 kg body weight) and finishing (approximately 65-110 kg body weight) pigs. For this purpose, according to a bifactorial arrangement in the grower as well as in the finisher phase four dietary threonine levels were combined with two dietary levels of lysine. Measurement criteria were body weight gain, feed intake, feed conversion rate and carcass characteristics. In the grower stage at the lower lysine level daily gain increased numerically (p < 0.1) and the feed to gain ratio decreased significantly with an increasing dietary true ileal digestible threonine concentration. Increasing the true ileal digestible lysine concentration of the diet from 7.8 to 9.2 g/kg increased average daily gain in the grower stage significantly from 815 to 855 g and decreased the feed to gain ratio significantly. In finishing pigs, daily gain and feed to gain ratio were significantly improved by an increasing dietary true ileal digestible threonine concentration from 821 to 902 g and from 3.14 to 2.94 kg/kg, respectively, but not by the differing lysine supply. As in the grower stage, barrows consumed more feed than gilts at similar growth rates and this resulted in a significantly reduced feed to gain ratio in gilts compared with barrows. The requirements of true ileal digestible threonine for optimize both, daily gain and feed to gain ratio, as derived by the broken-line model were 10.3 g/animal and day for growing and 10.7 g/animal and day for finishing pigs respectively.     

Lysine requirement of growing male Pekin ducks

1. One growth experiment and one balance test were conducted to study the response to increasing levels of dietary lysine supplementation in male Pekin ducks with special reference to the growth periods from 1 to 3 weeks and 4 to 7 weeks of age. 2. Two different low-lysine diets were used as basal diets in both periods. The basal lysine levels were 7.6 g/kg (d 1 to 21) and 6.2 g/kg (d 22 to 49) and the ranges in lysine concentration were 7.6 to 12.6 g/kg (d 1 to 21) and 6.2 to 11.2 g/kg (d 22 to 49). 3. Growth performance, feed conversion efficiency and meat yield increased ( P < 0.05) with increas6 ing lysine concentration (requirement defined as 95% of the asymptote). 4. It is concluded that the dietary lysine concentration should be 0.93 g/MJ nitrogen corrected apparent metabolisable energy (AME N ) (11.7 g/kg) for the starter period (until d 21) and 0.75 g/MJ AME N (10.0 g/kg) for the grower period (from d 22 onwards).     

Welfare assessment of broiler breeders that are food restricted after peak rate of lay

1. Broiler breeder females were reared on one of three growth curves (ad libitum, conventional or modified restriction) and given rations containing a high or low concentration of crude protein. After the peak rate of lay they were fed ad libitum or a decreasing quantity of food in response to declining egg production. The welfare of the birds was assessed by determining the changes in indices of welfare at 36, 48 and 60 weeks of age. 2. Body weight increased rapidly in restricted birds fed ad libitum post-peak and water intake declined. 3. Post-peak food restriction was associated with a decrease in resting and increased drinking and spot-pecking activities. Birds that were food restricted during rearing spent more time foraging and spot-pecking at 36 and 48 but not 60 weeks of age. 4. Immune function increased with age but was not affected by the experimental treatments. The heterophil-lymphocyte ratio in birds fed ad libitum during rearing was numerically lower at 36 and higher at 48 and 60 weeks of age compared with restricted birds. 5. There was no effect of treatment on plasma corticosterone concentration. Creatine kinase activity was high at 60 weeks in treatments that were characterised by poor reproductive status and the activities of other enzymes reflected differences in reproductive status and mortality. 6. There was no long-term welfare or production advantage from feeding low protein rations or more generous feeding during the rearing period compared with conventional food restriction programmes.     

Growth and laying performance of light‐hybrid pullets subjected to quantitative food restriction

1. Three degrees of quantitative food restriction producing body weights 88, 76 or 64% of controls at 20 weeks and three times of starting restriction 3, 6 or 9 weeks of age were compared with ad libitum‐fed pullets in a factorial experiment with 1800 light‐hybrid hens. Restrictions were applied such that the target weights were produced irrespective of time of starting.

2. Food intake was least when restrictions were started at 3 weeks.

3. Sexual maturity was delayed in proportion to the severity of restriction and resulted in lower percentages of small eggs.

4. Egg numbers decreased as restriction increased.

5. Mortality in restricted groups during rearing and laying was higher.

6. Optimal restriction was apparently intermediate between treatments producing 88 or 76% of ad libitum‐fed body weight. Body weight was so excessively affected by the most severe restriction that total production was adversely affected.

7. Restriction from 3 weeks was more profitable than restriction from 6 or 9 weeks, resulting in lower food cost during rearing and higher total egg production.