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Keywords: Layer breeding, balanced selection, behaviour, welfare, production efficiency

Innovative Layer Genetics to Improve Egg production

16.12.2017

Abstract

In commercial layer breeding, extensive gene pools are tested and selected for market requirements which must be anticipated at least five years ahead. Animal welfare and cage-free housing dominate future needs of the market. Stronger shells for longer production cycles without moulting have to be combined with stronger bones. Nesting behaviour and minimal tendency to develop feather pecking or cannibalism without beak treatment, are key trait complexes. Field results confirm a continuous positive genetic trend in egg output and better feed efficiency which can be converted into land savings.
No single big gene effect can be expected to control the multifactorial problem of feather pecking. Adjusting the shape of the beak, with a heritability of .10 to .25, can contribute to reducing the risk of severe cannibalism. For better skeletal integrity, the assessment of bone quality in pedigree birds housed in enriched cages is done by keel bone palpation or ultrasound measurement of the humerous. Both traits show similar heritabilities in the range of .15 to .30 and can be included in a balanced selection approach for performance, quality, and welfare traits. The combination of performance testing and genome-wide marker analysis, are promising tools to generate more progress for a balanced performance and behaviour profile.

Introduction

Today’s human population of more than 7 billion will grow steadily and by 2050, this will reach about 9 billion. In order to feed the growing human population, the production of food will have to be more efficient in terms of utilising the limited resources that we have. We have to produce large amounts of high quality protein with affordable prices to cover the growing demand. Production systems need to be environmentally friendly, socially responsible and economically viable. Selective breeding of farm animals can make a major contribution to this global challenge. The demand for eggs is on a level of 75 million tons with an annual increase of 1 million tons each year. To satisfy the increasing demands, at least 50 million hens will have to be added each year, assuming management conditions to support the genetic potential for 20kg egg mass per hen, i.e. from 20 to 76 weeks of age. Current per capita egg consumption and the rate of change, differ considerably between continents and countries within continents, depending on traditions, purchasing power, and the ability of other sources of food. Europe and North America havelittle growth potential, while the demand in countries like China, India, Latin America and certain countries in Africa, is expected to grow considerably, especially due to changing consumer habits of educated urban people with the necessary purchasing power. Consumer habits and preferences for specific egg characteristics like shell colour and egg size also differ between countries and between consumers within a country. Japan, for example, has maintained one of the highest levels of consumption with more than 300 eggs per capita for decades. The custom of breaking a raw eggover a bowl of rice for breakfast helps to explain the focus on egg quality: whiteshelled eggs with superior internal egg quality and guaranteed freedom from Salmonella. White eggs are also preferred in North and Central America, the Middle East, India, Taiwan and the Philippines, whereas brown eggs are preferred in most countries of Latin America, Europe and China. Tinted eggs, produced from crosses between White Leghorns and brownegg breeds, are popular in Japan and China, but seldom seen in Europe. The layer breeding industry has gone through significant changes during the past decades and has a remarkable record to cope with new challenges. Increased egg production, improved feed efficiency and adaptation of egg quality to consumer preferences have contributed significantly to the success of the poultry industry. Without these genetic improvements and corresponding improvement of nutrition, disease control and general farm management, the poultry industry would not have achieved its current position in the global food market. While the focus has to remain on maximizing the genetic potential for producing high quality protein at competitive cost, additional requirements of the egg industry, changing consumer habits and public opinion have to be taken into account.

General layout of layer breeding

Primary breeders have to look beyond current requirements and anticipate changing needs and opportunities at least five years into the future. Close communication between breeders and distributors is necessary to introduce new varieties at the right time to benefit from growing niche markets. For the global layer business, diverse markets have to be served and each of these may prefer different performance profiles of the commercial layers. This requires extensive gene pools with large elite lines which can be combined to generate strain crosses with specific attributes to meet market needs as closely as possible. Maintaining and developing new lines, testing, selection and reproduction of primary stocks involves high fixed costs in the operation and requires superior skills in quantitative genetics as well as internal organization to keep track of the availability of different sub-lines for niche markets. Genetic development, marketing and technical support have to communicate closely with local distributors to provide the best possible service for the current market and to benefit from changing requirements. Major challenges for the layer industries are constantly high feed prices and animal welfare which is gaining more importance not only in Europe, but also in North America. Geneticists must anticipate at least five years ahead as to what the market trends will be like as well as consumer orientation. When alternative husbandry and organic egg production were introduced some years ago, no one believed that these would someday become dominant market trends. At the time when the prospect of a prohibition of beak treatment was outlined, no one would have ever imagined that it would actually happen in several European countries. The same goes for male chicks, whose culling will be prohibited and replaced by determining sex in the egg. In fact, European legislation forbidding any kind of amputation to animals has been in place for a long time now. In the next five years, the determination of sex in the egg will be a reality, or even the demand for layer nutrition where only non-GM raw materials and ingredients are to be used in the formulation. Future selection goals are geared towards extending the production period and increasing the number of saleable eggs per hen, improving shell quality, and hen liveability with consistent feather cover until the end.

Stronger shells for longer cycles without moulting have to be combined with better bones. Bone strength and breakage can be a major issue in cage-free environments. Also, the enrichment with perches can be a challenge for the skeletal integrity and bone lesions.

Housing systems vary between continents and within Europe. In Switzerland, Austria, Sweden and Germany, commercial layer cages have been banned for several years. Enriched cages, considered by poultry scientists as an acceptable compromise between demands of animal welfare organizations and the “needs” of laying hens, are installed in Europe as an alternative to conventional battery cages. Retailers and animal welfare groups in different countries, continue to lobby for a complete ban on cages in Europe. Even in North America, a change from cage systems to aviary systems is most likely within the next decade.

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A total of 1320 hens, 600 Lohmann Selected Leghorn (LSL) classic and 720 Lohmann Brown (LB) classic were used. All birds were raised from day-old up to 18 weeks of age in deep litter pens at the Experimental Poultry Farm of Bavaria, Kitzingen, Germany. The birds were not beak trimmed. At 19 weeks of age the pullets were transferred to a force ventilated layer house with windows. The layer house was subdivided in 44 deep litter pens of 4.07 m² each. 30 birds (7.4 birds per m²) were housed in each pen; 24 pens were stocked with LB and 20 pens with LSL. Four experimental diets, a control diet and three different substitution treatments, with 11 replicates each were randomly assigned to the pens. The control diet represented a practical diet containing 16% of HP soybean meal and 8% of DDGS as protein sources (table 2).

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A control diet on the basis of soybean meal only would contain 19% of soybean meal. This hypothetical diet was used as reference for the substitution of soybean meal by other components. In treatment one (T1) 52.6% of soybean meal was replaced by 15.7% of a mixture of rapeseed meal from extracted rapeseed (RSE), rapeseed expeller (RSC) and sunflower meal (SFM). In treatment 2 (T2) soybean meal was entirely replaced with sunflower meal as main component and small amounts of DDGS, RSE extract and RSC. The substitution components in treatment 3 (T3) were based on RSE and RSC. Within each treatment a four phase feeding program was established to adjust the nutrient composition to the changing requirements of the hens (Table 3). Within the treatments and feeding phases all diets were iso-caloric, iso-nitrogen and contained the same amount of minerals and vitamins. Egg production, egg quality, mortality, feather conditions, injuries of skin and toes and economic criteria and egg income over feed cost (IOFC) were determined for a full-year laying period. Data were analyzed using a two-factorial model with line and feed treatment as main effects. Within each line, differences between dietary treatments were tested using Tukey’s multiple t-test. Treatment x strain interactions were not tested for statistical signifcance.

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Results and discussion

Mean values of all criteria are shown in table 4 for LB and table 5 for LSL. LSL showed generally a higher percentage of egg production than LB with the highest egg production in T1 (89.9%). The effect of diets within lines where however, not signifcant. In LB hens in treatments T1 to T3 showed in tendency a higher performance then the control birds. This shows that LB hens responded more sensitively to the replacement of SBM than LSL. This is supported by the data of daily feed intake. There was a signifcant reduction in daily feed intake in the diets with higher proportions of rape seed products. T3 with a total of 16% of rape seed products showed the lowest daily feed intake (120 g), while T1 and T2 with 8% of rape seed products took an intermediate position between the control and T3. Why some birds dislike rape seed products and react with decreased feed intake has not been explained so far; chemical characteristics, the color, structure or taste of the feed may be involved.

Feed conversion was consistently more efcient in LSL than LB layers. Mortality varied between 2.8% and 9.3% in LB and 5.3% and 9.3% in LSL, but the differences due to treatment are not signifcant due to small number of replications. In LSL the main cause of mortality was toe pecking: 31 out of 48 hens which died or had to be culled for this reason. This problem occurred in all dietary treatments and may be due to the fact that the birds were not beak-treated.

In both lines, there was a signifcant dose response on egg weight for the level of substitution of soybean meal: egg weight decreased consistently with increasing level of substitution of SBM. Low egg weight of 63.3 and 62.0 g was found in diets containing high levels of sunflower meal (T3) in LB and LSL respectively. Similar reduction in egg size was found in LB in T2 (63.3 g). Low levels of different substitutes (T1) showed an intermediate egg size of 63.6 and 63.2 g in LB and LSL respectively. The negative correlation between rate of lay and egg size is well known and also is found in this experiment, where the negative effect on egg weight is partially compensated by higher egg production. Differences in average daily egg mass or total hen-housed egg mass are therefore small, but have to be kept in perspective when calculating egg income over feed cost.

5-damme

Due to reduced egg weight in non-soybean meal diets T2 and T3, the proportion of small eggs (S) increased substantially in the frst weeks of lay and the proportion of eggs in the categories large (L) and extra  large (XL) at the end of the laying period was lower. Since small eggs (below 53 g) cannot be sold as table eggs, they have to be sold at a low price to processing plants. The proportion of cracked eggs was lower in LSL than in LB hens. Egg shell strength was lower in T2 (high level of sunflower meal), but the proportion of cracked eggs was not increased in this treatment. Sunflower meal increased the percentage of dirty eggs in both lines. Average feather scores differed signifcantly between feed treatments within line, but were not consistent across lines. Differences between lines could only be shown when particular areas were considered. While LSL showed more feather loss on the neck and back, more damage in the vent area was found in LB. However, most hens (93 to 79%) showed only slight feather damage (scores 0 and 1). Lower scores occurred in the control diet: only 7% of LB and 8% of LSL layers had featherless areas with more than 5 cm in diameter. In LB the highest score was found in T1 (1.01) and the lowest in the control. The deterioration of the feathers is mainly caused by vigorous feather pecking and pulling.High dietary fber has been found to reduce the risk of feather pecking. The fber content of diets in phase 1 feed was 2.8% in the control, 3.8% in T1, 5.8% in T2 and 4.8% in T3. The control diet had the best feather condition in both lines, although it had the lowest fber content. Thus, a lower level of dietary fber cannot explain feather pecking damages in the present study, but the higher feed intake of the control birds may have reduced feather pecking. Especially at the onset of lay many birds don’t eat enough to fully cover their nutritional requirement, and reduced feed intake in response to the substitution of SBM may have contributed to the development of feather pecking. In line with the feather scores, skin injuries were also less frequent in the control compared to the other dietary treatments. Injuries of the skin occurred mainly in the cloacal area and in the area of the preening gland. However, differences between lines and dietary treatments where not signifcant. The occurrence of “bumble foot” and toe lesions is often considered as a problem of nutrition. Diets which lead to wet litter have been found to increase the risk of footpad problems. In the present study there was no signifcant effect of the diet. There was a tendency of better foot conditions with T1 feed in both lines. The lines differed signifcantly in the frequency of footpad damages. The percentage of birds with intact footpads was 56.1% in LB and only 13.3% in LSL. Similar results were found for toe injuries. The proportion of birds showing no toe damage varied between 77 and 93% in LSL and 95 and 100% in LB. The effect of dietary treatments was not signifcant in LB. In LSL, T2 had the lowest proportion of birds with intact toes (77%). In both lines toe conditions were best in the control (93% of intact toes in LSL and 100 % in LB). The cause of the high frequency of toe injuries in LSL when fed sunflower meal (T2) is not known,  nor is it consistent with feather scores and skin injuries. Therefore it should not be concluded from these results that  sunflower meal represents a special risk for cannibalism.

Economics

The economic calculation is based on the assumption that imported non-GMO HP soybean meal is replaced by locally produced DDGS, rape seed extract, rape seed expeller, sunflower meal and maize gluten. Since non-GMO HP soybean meal is very expensive, its substitution with locally grown products leads to a substantial reduction of feed cost compared to the control diet: 1€/dt in T1, 1.31 €/dt in T2 and 1.55 €/dt in T3. Taking different egg prices into account, calculations were made for three different scenarios: eggs sold (1) to an egg processing plant (lowest price), (2) to a large-scale packing station (intermediate price), and (3) directly to the consumer (highest price). The results are shown tables 4 and 5. Independent of the egg price, egg income over feed cost (IOFC) was higher for LSL than in LB layers. The economic results with different diets also differed between lines: under all marketing scenarios, LB layers produced a higher IOFC when imported non-GMO soybean meal was replaced by alternative sources of protein: the best result was found with T3, followed by T1 and T2, and the lower egg production with the control diet in LB could not be compensated by larger eggs. In LSL the best economic result was achieved in T1 under all marketing scenarios, followed by control, T3 and T2. However, it should be kept in mind that the calculation is based on the high price of non-GMO soybean meal. With the same performance, the ranking of economic results would be reversed if ordinary GMO soybean meal were used.

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Conclusions

  • Total substitution of imported soybean meal with locally available sources of protein in layer diets leads to reduced daily feed intake, reduced egg weight, and more damage of feathers, skin and toes. Therefore total substitution is not  recommended at present. Further experiments are required to fnd out whether disadvantages of alternative feedstuffs may be removed by adjusting nutrient density, composition of amino acids or feed additives which improve the digestibility of nutrients in these components.

  • Genetic lines respond differently to alternative feedstuffs. Brown-egg layers like LB appear to be more sensitive than white-egg layers like LSL to substitution of soybean meal.

  • High levels (16%) of sunflower meal produced more dirty eggs and toe damages than other diets.

  • Partial substitution of non-GMO soybean meal by moderate levels of locally available substitutes (rape seed products, sunflower meal) showed similar performance in terms of egg mass and feed efciency, but minor problems of welfare related characteristics.

References

Jeroch, H., Simon, A., Zentek, J. 2012:
Geflügelernährung. Verlag Eugen Ulmer,
Stuttgart, Germany.

Jeroch, H., Dänicke, S. 2016: Faustzahlen
zur Geflügelfütterung. In: Geflügeljahrbuch 2017. Verlag Eugen Ulmer, Stuttgart,Germany.

Kamphues, J. 2014: Supplemente zur
Tierernährung. Verlag Schaper, Hannover,
Germany

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