Achieving optimal body weight and body composition through feed intake is vital in terms of hen development, as it is needed to support efficient production. Feed intake is restricted in broiler breeders as the birds are unable to adequately self-regulate feed intake, while with ad libitum fed breeder hens, there is a decrease in the total egg output. In addition, very severe feed restriction results in poor egg production (Wilson and Harms 1986).

Selection pressure is causing greater nutritional restriction in broiler breedersGenetic companies are gradually improving broiler chicken body weight gain, feed conversion ratio and meat yield (Havenstein, Ferket et al., 2003). However, broiler breeder management regarding feed allocation and body weight targets has been kept quite constant. As a result, broiler breeders are suffering from increased feed and nutrient restrictions with continued breeder selection pressure. Feed restriction during the rearing phase, which is estimated to be between 33-50% of the ad libitum feed intake of broilers at a similar age or body weight (de Jong, Voorst et al., 2002), is a focal point of concern in terms of broiler breeder welfare and later performance. The highest feed restriction in broiler breeders occurs between 8 and 16 weeks of age which makes this phase critical during development (Hocking, 1993). Since feed restriction conditions prevent certain growth-, metabolic-, reproductive- and health-related problems, the growth curves provided by the primary breeder companies have been recommended as the most welfare-friendly alternative to ad libitum feeding (Renema and Robinson, 2004). However, this can result in considerable feelings of hunger in the birds (Mench, 2002), which has been an increasing concern from an animal welfare viewpoint.

The potential to reduce the degree of feed restriction and feelings of hunger has been assessed with contrasting results, for instance, through diluted diets (Hocking, Zaczek et al., 2004), relaxed feed restriction (Hocking, Maxwell et al., 2002; Bruggeman, Onagbesan et al., 2005), and the introduction of alternative genetic stocks (Heck, Onagbesan et al., 2004; Bruggeman, Onagbesan et al., 2005).

Diluted diets as an alternative to reduce feed restriction and improve resultsUsing diluted diets during production phases has been studied with varying results – although the studies have only been on a limited scale to this point.• Zuidhof et al. (1995) observed greater egg and chick production

when whole oat hulls were used to dilute the nutrients in the broiler breeder’s feed.

• Enting et al. (2007) obtained a higher rate of lay with the 11% diluted diet, compared to a control diet. In addition, although the percentage of fertile eggs did not differ among treatments, the 11% diluted diets produced higher egg weights but significantly lowered hatchability.

• Tolkamp et al. (2005) observed that qualitative restriction suffers from the inability to accuracy achieve target body weights or desired uniformity of weight gain.

• Zuidhof et al. (1995) observed that the rate of decrease in flock uniformity during lay was slower in hens fed the diluted diets.

The offspring of parent stocks that have been fed diluted diets have shown significantly lower mortality (Enting et al., 2007). This effect is most evident in older breeder flocks. The differences in humoral immunity were also obtained (IgM and IgG responses). The authors related these results to the differences in egg size and egg composition. In addition, chicks from breeders fed diluted diets reached higher final body weights (at 38 days old) which may be mainly related to the different nutrient intakes of the parents. Based on current literature data, the effect of low density breeder diets on progeny is very positive. However, the scarcity of trials at offspring level suggests that more research work is needed to corroborate these results.

Broiler breeders feeding strategies

Poultry UpdateFeed recommendations 2016

Trouw Nutritions’s broiler breeder feeding strategyTrouw Nutrition R&D is aware of the potential impact that genetic improvements have on broiler breeder nutrition and management. Broiler breeders are increasingly restricted compared to their potential. For that reason, hunger, metabolic disorders, and stereotypic behaviours are now common in commercial production. In order to reduce feelings of hunger, fibre-rich feeds and low-density feeds have been tested in small flocks. The effects have not been unequivocal and may be dependent on the nutrient density of the feeds that were used among the different studies. Since a less severe feed intake restriction might have less pronounced effects on feelings of hunger and stress hormone levels, it can be hypothesised that a combination of low-density feeds and a less severe restriction of feed intake will have a more positive effect on bird welfare and production performance in late lay. As evidence suggests that current feed intake restriction levels may have a negative effect on laying performance and day-old chicken quality, a higher feeding level during the rearing and production period may improve these two parameters by reducing the feelings of hunger, increased uniformity by the end of the rearing phase, and reduced stereotypic behavioural activities (such as pecking, which can develop into cannibalism).

Research and DevelopmentThe Broiler Breeder Feeding Strategy project was developed to study the effect of diluted (low density) diets formulated with fibrous raw materials, in combination with high body weight (BW) targets, as strategies to increase feed allowance and to reduce the negative effects that occur from current feed restriction practices. A series of four research trials were performed by Trouw Nutrition R&D. Two of the trials took place during the rearing phase (0-19 weeks old), and differed in that one used feed in mash form (RP-6) and the other used feed in crumble form (RP-7). Another trial took place from the start of the production phase up to 50 weeks old, and used a crumble diet. Finally, an offspring study was also conducted to evaluate breeder nutrition strategies on broiler progeny performance.

Rearing PhaseThe two rearing phase studies (RP-6 and RP-7) were conducted to study the effect of diet dilution and higher body weight targets throughout rearing (0-19 weeks old) on breeder pullet uniformity, body composition, feelings of hunger and behaviour. Both trials were designed to test the hypothesis that using diluted diets and allowing pullets to reach higher body weights may reduce feelings of hunger, stereotypic behaviour, mortality and variations in body weight, which could ultimately lead to better performance in the subsequent production periods.

Trials were designed as 2x2 factorial designs (Table 1) to determine the effect of two different diets (standard versus diluted) and two different breeder target body weights (standard versus higher BW) and their possible interaction. Each treatment had 5 replicates of 170 and 150 breeder females/pen (RP-6 and RP-7, respectively).

Table 1. Trial design for RP-6 and RP-7 broiler breeder studies investigating the impacts of dietary nutrient density and pullet-rearing weight targets

Treatment 1 2 3 4

Diet Standard Standard Diluted Diluted

Target BW, g Standard* Higher Standard* Higher

* Standard body weight RP-6 from Aviagen 2008 and RP-7 from Aviagen 2012 recommendations

For trials RP-6 and RP-7, 3,400 (5.6 females/m2) and 3,000 (5.0 females/m2) birds were tested. In both trials, broiler breeder females between 0 and 3 weeks old were fed a pellet diet (2mm diameter). From 3 to 19 weeks, the broiler breeders were given feed in mash form in trial RP-6 and in crumble form in trial RP-7. Although both trials were based on the Ross 308 recommendations, the target body weight values differed between the two as the RP-6 trial followed the 2008 recommendations, and the RP-7 trial followed the 2012 recommendations.

The target body weights were achieved by using different diets which resulted in four varying amounts of feed offered. Time spent eating was significantly increased (P<0.05) when birds were reared to heavier target body weights. In addition, in RP-6 (mash feed), the birds that were fed diluted diets spent more time eating compared to the birds eating the standard diet (P<0.0001). This result suggests that when fed diets in mash form, birds spend more time eating, even with diluted diets, but that with crumbles this effect is reduced (see Figure 1).

The feeding rate test (Figure 2) measured the amount of mash feed consumed over a period two minutes under the normal restricted regimen or after a period of ad libitum feeding in RP-6. The concept behind this test is that the level of hunger is reflected in the speed of eating. The less feed consumed within a certain time, the lower the perceived hunger level. Birds fed diluted diets were statistically (P<0.05) less motivated to eat under the standard restricted regimen compared to the birds fed with the standard diet. The second hunger test (ad-libitum) is performed to check the differences in terms of feeding motivation between chronic (restricted) and acute feed deprivation (ad-libitum). The differences demonstrated that birds were less hungry (i.e., food motivated) when fed the diluted diet as they ate 40% less feed on average (35-45%), which agrees with observations by Savory (1993).

Standard diet Diluted diet

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150

100

50

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This supports our assertion that birds fed Treatments 1 to 3 ad-libitum had the same food motivation as birds fed Treatment 4 on feed restricted diets, and these birds still reduced their feed intake when fed ad-libitum.

In RP-7, the feeding rate test showed significant differences between the birds fed diluted and standard crumble diets (P<0.0001). Figure 3 shows the feed intake during two minutes after a 24 hour feed withdrawal. Within the study results, the bars on the left are the birds that have had restricted feeding (normal regimen) and, on the right, the same birds after 5 days of ad libitum feeding. The only results of the effect of the diet are shown, as no significant differences due to target BW were observed. Breeders eating the diluted diet consumed less than those fed standard diets during their first access to the feed when kept in restricted regimen. After 5 days of ad libitum feeding, the birds eating the standard diet and the diluted diet ate less feed than when they were restricted, indicating that in both situations the birds suffer different feelings of hunger, or at least, are less motivated to eat. These results are similar to those obtained in RP-6 but are in contrast to those obtained by Nielsen (2011), who observed that, under both regimens, breeders were equally hungry.

Behavioural observations were also performed in the two trials. In both studies, the differences between the morning and the afternoon results were observed for some of the behavioural observations, mainly in those related to pecking. Broiler breeders fed diluted diets consistently showed less stereotypic behaviour related to fixed pecking elements (Figure 4). These differences could be attributed to an increase in feeding time (as observed in diluted diets) and could corroborate the observation that breeder pullets eating diluted diets are grown with a better standard of management in terms of animal welfare. It was also observed that growing birds to heavier BW tended (P=0.0529) to reduce the pecking behaviour during the morning, as shown in Figure 4.

In summary, using diluted diets during the rearing phase significantly improves animal welfare. This is because the birds’ reduced motivation to eat suggests less feelings of hunger, while body weight and uniformity targets are achieved. Birds spend more time eating, which leads to less stereotypic behaviour related to pecking. Rearing breeder females to heavier body weights seems to be a positive strategy in terms of improving breeder welfare, as the feeding rate test response was larger in relation to fixed pecking elements.

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Figure 1. Effect of diet and target BW in time spent eating (minutes) during the rearing phase (RP-6 and RP-7 trials)

Figure 2. Feeding rate test results for RP-6 (mash)

Figure 3. Feeding rate test results for RP-7 (crumble)

Standard diet Diluted diet

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Morning Afternoon

14.911.71

P=0.133

P=0.04099.069 6.283

Standard target BW High target BW

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P=0.04968.995 6.336

Production phaseThe birds reared in the course of the RP-7 trial were kept to study the effect of diet dilution and higher body weight targets during the production phase (until 50 weeks old). Males were mixed with females at 21 weeks old (11 hens : 1 cockerel). Males followed standard BW recommendations (Aviagen 2012) and were fed a standard separate male diet for all treatments. Females were fed following the minimum nutrient requirements. Eggs were collected daily and sent twice a week to a multi-stage hatchery between weeks 28 and 50. The results showed no significant differences in number of hatching eggs, hatched chicks or breeder hen mortality (Table 2). However, breeders grown to heavier body weights had higher egg production, and birds fed the standard (control) diet produced more eggs (Table 2). Egg weight was also affected by the treatment. Eggs from heavy females had the highest weight and eggs from standard BW hens were smaller. In addition, eggs from females grown to the standard BW with a diluted diet were the lightest, and significantly lower than those coming from the hens fed the control diet.

Standard diet Diluted diet

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46.46

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30.74 24.12P=0.0529

Figure 4. Effect of diet and target BW on fixed pecking elements stereotypic behaviour

Pecking fixed elements, % (RP-7)

Pecking fixed elements, % (RP-6)

Table 2. Carry-over effects on broiler breeder production performance (28-50 weeks old) during the rearing phase, on birds with different growth target weights, fed diets varying in nutrient density

Treatment Diet Body weight Egg production%

Hatching eggs%

Hatched chicks%

Egg weightg

Cum. Mortality%

Standard 73.21 a 91.48 81.33 63.97a a 2.876

Diluted 70.92 b 90.20 81.48 63.80b b 2.513

Standard 71.14 b 90.47 81.48 63.51b b 3.016

Heavy 72.99 a 91.22 81.33 64.26a a 2.372

1 Standard Standard 72.54 a 91.34 81.15 63.72b b 4.522

2 Standard Heavy 73.88 a 91.62 81.50 64.22a a 1.230

3 Diluted Standard 69.73 b 89.59 81.81 63.31c c 1.510

4 Diluted Heavy 72.10 ab 90.81 81.15 64.29a a 3.515

The differences in terms of egg production and egg weight between treatments could have been partly provoked by the differences in nutrient intake (see Table 3 and Figure 5). This fact could actually have been more relevant to the results than the differences between standard or diluted diets. Figure 5 illustrates the effect that energy and protein intake have on egg production,

and suggests that for high or standard body weights a minimum energy and protein intake is needed to optimise performance. According to broken line analysis, the minimum energy intake requirement is 410 kcal/d and the minimum CP intake is 22.8 g/d (considering the global phase from 20 to 50 weeks old).

Table 3. Mean nutrient intake in relation to diet density and target hen weight (standard versus higher)

Treatment Diet Body Weight Energykcal/d

Crude Proteing/d

Calciumg/d

Digestible Phosphorous

g/d

Standard 422.1 23.26 4.369 0.475

Diluted 406.3 22.46 4.200 0.457

Standard 396.0 21.849 4.100 0.444

Heavy 432.5 23.862 4.469 0.488

1 Standard Standard 403.0 22.20 4.174 0.452

2 Standard Heavy 441.3 24.31 4.564 0.498

3 Diluted Standard 389.1 21.50 4.026 0.436

4 Diluted Heavy 423.6 23.41 4.374 0.478

As observed in the rearing phase, both diluted diets and allowing breeding females to reach heavier body weights increased the time spent eating, which, in turn, led to fewer stereotypic activities related to pecking behaviour.

Offspring studyThis trial was conducted to evaluate the effects that broiler breeder target body weights and diet dilution has on offspring performance. Broiler breeders were fed a standard or diluted diet and grown to a standard or higher body weight, than breed target in a 2x2 factorial design. The eggs from 29 week old hens were collected and incubated in a single stage hatchery. A total of 6,080 chicks were placed at three different Trouw Nutrition R&D (PRC) facilities, according to the broiler breeders’ treatments. Each treatment had 42 replicates, consisting of 30-40 birds each. All the chickens were fed a standard feed program consisting of three phases following the Trouw Nutrition 2011 recommendations; starter (0-9 days), grower (9-22 days) and finisher (22-37 days).

Performance results from 0 to 37 days (Table 4) suggest that the Broiler Breeder Feeding Strategies applied in this project did not affect broiler performance parameters, with the exception of mortality where the offspring of broiler breeder hens reared to

higher than recommended target weights (P=0.063) tended to have numerically lower mortality than standard, breed recommended, target weights (5.73 versus 7.65%, respectively). This response was consistent between all phases studied.

Table 4. Performance from 0 to 37 days old

From 0 to 37 days BW 37dg

DWGg/d

DFIg/d

FCRg/g

Mort.%

Diet

Standard 2674 71.31 111.6 1.566 7.063

Diluted 2670 71.14 111.2 1.564 6.320

Target BW

Standard 2671 71.13 111.2 1.564 7.653

Heavy 2673 71.32 111.7 1.566 5.730

Diet*Target BW

StandardStandard 2675 71.26 111.5 1.565 7.866

Heavy 2673 71.37 111.8 1.567 6.260

Diluted Standard 2667 71.00 110.9 1.562 7.440

Heavy 2674 71.27 111.5 1.565 5.200

380.0 390.0 400.0 410.0 420.0 430.0 440.0 450.0

Min AME = 410Kcal/d

75.074.574.073.573.072.572.071.571.070.570.069.569.068.0

Diluted-Std

Diluted-Heavy

Standard-Std

Control-Heavy

21.00 22.00 23.00 24.00 25.00

Min CP = 22.8 g/d

75.074.574.073.573.072.572.071.571.070.570.069.569.068.0

Diluted-Std

Diluted-Heavy

Standard-Std

Standard-Heavy

Conclusions

Rearing phase: combine body weight targets with diluted dietsA combination of heavy body weight targets and diluted diets appears to be the most reliable strategy to increase the amount of time spent eating, as well as to reduce eating motivation and stereotypic pecking behaviour.

Using diluted diets (independent of the target body weight) reduced the motivation to eat and increased the time that breeder females were eating.

When crumble diets are used, the impact on the time spent eating is much lower than with mash diets. This suggests that mash diets are advisable when trying to increase the amount of time spent eating. Production phase: higher body weight targets to support overall performanceRearing breeder hens to higher target body weights (higher than recommended by Aviagen 2012) in the rearing phase appears to support the best overall production phase performance (as in, by producing a higher percentage of eggs), independently of the diet used.

Diluted diets had positive effects on reducing non-desirable activities (e.g., pecking) by keeping the birds busy eating. None of the interventions, as in diluted diets and higher body weights, or even combinations of the two, had any significant effect on the number of hatchable eggs or hatched chicks.

Figure 5. Relationship between dietary energy and protein intake and egg production %

Egg Production % vs CP Intake Egg Production % vs Energy Intake

To maintain bird performance, minimum nutrient intakes (energy and protein) are required, independently of the diet (control or diluted), and may vary according the body weight and production level.

Offspring performancesFeeding diluted diets to young breeders had no measurable impact on offspring performance. However, raising breeders to a higher body weight tended to reduce mortality in their progeny.

RecommendationsDeveloped by Trouw Nutrition, the Broiler breeder feeding strategy concepts can improve the welfare and performance of your breeders.

The NutriOpt Broiler breeder recommendations and calculator will allow you to implement these feeding strategies according your current breeder nutritional program. Contact a Trouw Nutrition representative near you to discuss how to put NutriOpt services and tools to work for you.

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errors, misinterpretations or consequences when the information is applied. This document or its content is not to be copied or further distributed without the consent of Nutreco Nederland B.V.