Female Persistency Post-Peak: Managing Fertility and Production

Four main reasons for poor persistency in broiler breeder flocks are explained by Michael Longley, Aviagen's Global Technical Transfer Manager. He says that reacting efficiently and effectively to key management points is what will make the difference between a top- or bottom-quartile performing flock.

8 June 2013

17 minute read

By: Jackie Linden

Summary

Introduction

Chick numbers are most often reduced during the period between 40 to 60 weeks of age because of poor persistency in both egg production and hatchability. It is important to understand the main reasons why broiler breeder flocks exhibit poor persistency post-peak and how to overcome them.

The main reasons for poor persistency in broiler breeder flocks are:

Environment - temperature, ventilation, and lighting: Feed allocation must be adjusted appropriately for environmental temperature. Altering feed intake in response to changes in temperature must also take into account egg production levels, egg weight, egg mass, and body weight. Ventilation must be appropriate for bird biomass and external environmental conditions. Wherever possible, do not provide in excess of 14 hours of light in lay as this will advance the onset of adult photorefractoriness and reduce persistency of egg production.
Feather cover - feed management: Female feather cover plays an essential role in post-peak flock management for egg production and hatchability performance. Flocks with poorer than expected feather cover need to be properly managed if drops in hatchability and egg production are to be avoided. Close attention must be paid to feed level, house temperature, and mating ratio, the latter particularly where over-aggressive and/or too many males are present.
Body weight and egg weight: Body weight and egg weight must be monitored closely during the postpeak production period. Changes to feed levels made without consideration of body weight may lead to reduced persistency. For example, reducing feed too aggressively or without allowing or compensating for an overweight flock will cause a drop in persistency. Increasing feed too quickly to bring a flock back to target when it is underweight will push birds over weight too quickly, thus reducing egg production. A change in trend of egg weight increase often occurs before a drop in production is seen and so can be the first indication of a potential problem. A flock with higher or lower than expected increases in daily egg weight, away from the standard, should have feed allocation altered accordingly to avoid a fall in persistency.
Conditions in the production house: Nest box space, feeder space and feed distribution, drinker space, floor space, and litter quality must be appropriate for the flock and maintained within recommended levels.

Conclusion

Measuring and monitoring changes in feather cover, environmental temperature, flock condition, body weight and egg weight profile compared to standard, and housing conditions and external challenges is necessary to be able to react efficiently and effectively to how the flock is performing. Reacting efficiently and effectively to these key management points is what will make the difference between a top or bottom quartile performing flock.

Introduction

Managing for fertility is an important aspect of achieving good bird production and welfare. However, maintaining persistent egg output and high chick numbers remains a challenge for today’s production manager. Poor persistency in egg production and hatchability are still the main reason for loss of chick numbers during the period between 40 to 60 weeks of age.

This article looks at the main reasons why broiler breeder flocks exhibit poor persistency of egg production and hatchability post-peak, and aims to provide advice on how to overcome them.

What is a good performing broiler breeder flock?

During rearing, a good performing flock will have:

a weight gain profile that closely follows the breed standard body-weight targets throughout rear and achieves female target body weight at 20 weeks
appropriate fleshing and body conformation for age
good sustained female and male uniformity throughout rear, with a CV of less than 10 per cent at the end of rearing, and
excellent feather cover.

The rearing period forms the foundation on which the future performance of the flock is based. Without detailed management of all aspects of the rearing period, from brooding through to mating-up, and in particular grading the flock into correct rearing groups, future egg production performance will be compromised. A poorly reared flock is less predictable, with a quicker decline in persistency post-peak, and therefore a lower hatching egg and chick output compared to a well reared flock.

During production, a good performing flock will have:

a predictable and uniform onset of egg production in response to light stimulation
pin bone spacing of at least two fingers for more than 80 per cent of the females prior to first light stimulation.
a steady, regular increase in daily egg production from first egg
a peak hen-housed egg production level of greater than 86 per cent
cumulative hatchability of greater than 84 per cent to 64 weeks of age, and
good feather cover for age.

All of the traits given above play an important role in producing optimum hen-housed chick numbers of more than 145 chicks per hen to 64 weeks.

Main reasons for poor persistency in broiler breeder flocks

Many managers not reaching the levels of performance identified in the previous section see poor post-peak persistency as the main reason for this.

Monitoring of the following Key Management Points must form part of a daily management routine if issues of postpeak persistency are to be resolved.

Reacting efficiently and effectively to these Key Management Points is what will make the difference between a top or bottom quartile result. Each area is discussed in more detail below.

Key Management Points

Environment – temperature, air quality, ventilation, and lighting
Feather cover – feed management
Body weight and egg weight – compared to standard and weekly trends (gains)
Conditions in the production house – nest box space, feeder space and feed distribution, drinker space, floor space, litter quality
Feed management – nutrient intake and feeding management
Challenges – disease, temperature variation, mating ratios, parasites.

Environment – Temperature

The relationship between temperature and the effect it has on bird performance is often overlooked, especially when considering feed allocation and nutrient intake. Many managers feed the same feed amount for age throughout the year, regardless of environmental temperature.

Flocks peaking during the hotter months of the year would normally be allocated a lower peak feed amount and possibly have feed withdrawn more quickly after peak. However, feed amounts must be reviewed if there is a fall in temperature. Feed may need to be increased or held at a higher or more static level as production progresses through the winter or colder months. This will improve persistency without the occurrence of excess increases in female body weight.

A winter peaking flock will generally need a higher peak feed amount but it will be possible to withdraw feed post-peak more quickly during the summer or hotter periods of the year. This reduces the potential for a flock to become overweight, while also maintaining persistency.

When managed in closed-type housing, total cumulative post-peak feed withdrawal amounts from peak to end of lay can typically range from 10 to 11 per cent for a winter-peaking flock and eight to 10 per cent for a summer-peaking flock (based on body weight, egg production and feed levels given in the Global Performance Objectives).

In addition, it is important that feed intake is altered as operating temperature differs from 20°C (68°F). Energy intakes must be altered to account for changes in temperature. A basic rule is that:

For every 1°C (2°F) change from 20°C (68°F) between 15°C and 25°C (59 to 77°F) females will need an increase in energy of approximately one per cent per day per degree change.

For example, for a reduction in temperature from 20 to 15°C (68 to 59°F), females will require a five per cent increase in feed or an extra 25 to 30kcal of energy (9-10g / 0.3-0.4oz extra feed) per bird per day based on a 2,800kcal ME per kg diet. For an increase in daily average temperature from 20 to 25°C (68 to 77°F), females will require approximately a 25 to 30kcal reduction in daily energy intake (9-10g / 0.3-0.4oz less feed) based on a 2,800kcal ME per kg diet.

It is essential that the changing energy requirements of the bird caused by changing environmental temperatures are taken into account. However, altering feed intake in response to changes in temperature is not straight forward and feed allocation, egg production levels, egg weight, egg mass, and body weight must also be considered before any changes are made.

Environment – lighting and persistency

In order to dissipate juvenile photorefractoriness, birds must experience at least 18 weeks of short daylengths (eight hours) during rearing. Birds can then be given, and will be able to respond to, an increase in daylength (light stimulation), thus initiating production. However, after prolonged exposure to long daylengths (more than 11 hours), birds become adult photorefractory. This means that they are no longer able to respond to a long stimulatory daylength and production begins to decline with age (the normal egg production curve). It is recommended that in lay, a daylength of 13 to 14 hours of light is provided. Providing more than 14 hours of light to a flock during lay will generally lead to that flock exhibiting poorer persistency because the onset of adult photorefractoriness will be advanced and production will decline more rapidly.

In situations where open-sided production houses are used, daylength should preferably be kept to 13 to 14 hours by use of blackout curtains at the beginning and end of each day.

Key Management Points

Standard objectives for feed allocation are based on house temperature of 20°C (68°F)
Correction in feed allocation is needed for house temperatures differing from 20°C (68°F)
For a winter peaking flock, aim to reduce feed levels by 10 to 11 per cent from peak to end of lay
For a summer peaking flock, aim to reduce feed levels by eight to 10 per cent from peak to end of lay
Manage rearing daylength to be a maximum of eight hours per day for at least 18 weeks
Production daylength should be a maximum of 13 to14 hours to help delay adult photorefractoriness.
Production traits ( per cent eggs, egg weight, egg mass, body weight) after any feed change must be monitored closely.

Environment - Ventilation

Ventilation is a key part of the management system and should be monitored as closely as possible for the life of the flock. It is essential to highlight the importance of ventilation and the link it has with persistency. Inappropriate or inadequate ventilation can lead to poor persistency, and ventilation must be accurately matched to bird biomass, feather cover, and external environmental conditions. Exact ventilation principles will not be discussed further in this article.

Feather Cover

Female feather cover plays an essential role in post-peak flock management for egg production and hatchability performance. Flocks with poorer than expected feather cover, if not managed correctly, do show clear drops in hatchability and egg production that in many cases will not recover. Pay close attention to feed level, house temperature, and mating ratio, particularly mating ratio where over-aggressive and/or too many males are present.

Feather cover of broiler breeder females can be scored throughout the life of the flock using a 0 to 5 scale (0 relating to females being fully feathered and 5 relating to females with no or little feather cover). A sample of females should ideally be inspected for feather cover on a weekly basis. Each bird in the sample should be given a feather score so that an overall idea of flock feathering condition can be determined. This can be done in detail when handling the birds during weighing times and/or when walking through the flock during a general house inspection.

Examples of management areas that affect feather cover are provided in Table 1. More information can be obtained from a local Technical Service Manager.

Table 1. Examples of management factors that influence feather cover during the production period

Feather cover and nutrition

The influence of nutrient specifications, particularly in relation to methionine and cystine levels, should not be overlooked when considering feather condition. Aviagen nutrition specifications are designed to ensure optimal feather development throughout the life of the flock and should be followed as closely as possible to ensure best possible performance.

Feather cover - temperature and feed levels

The relationship between environmental temperature, feed level, and feather cover of females plays a particularly important role in post-peak production persistency. Many flocks experiencing lower than expected weekly egg production levels post-peak also exhibit feather cover that is much poorer than normal for age.

For flocks with poor feather cover, feed levels must be adjusted to allow for increased energy requirements. The relationship between feed level and environmental temperature discussed previously is based on changes required in feed allocation when house temperature varies from 20°C (68°F), and assumes a good feather cover. However, where feather cover is poor at lower temperatures, an additional increase in feed allocation (above the levels mentioned earlier) is essential to maintain production traits. The difference between a well-feathered flock in the summer and a poorly feathered flock in the winter may be as much as 25g (or 0.9oz) of feed per bird per day.

Feather cover and fertility

The focus up to this point has been on maintaining persistent egg production levels post-peak, but poor feather cover also has a direct impact on fertility levels, reducing the number of chicks per female, particularly after 40 weeks of age. This is not because the female becomes any less fertile as such but because a poorly feathered female becomes less receptive to male mating activity. Normal mating behaviour does not occur if a female does not have the protection of a layer of feathers. The very process of mating will have an impact on feather cover of females throughout the production cycle so it is important to monitor and understand the normal pattern of feather loss for a flock and react appropriately to natural changes in feather cover or if feather loss becomes excessive.

Over-mating

In many cases where flocks exhibit lower fertility levels through peak and drops in fertility, particularly post-peak, mating ratios are above those recommended (Table 2).

Table 2. Recommended mating ratios

Initial mating ratios (25 to 35 weeks) are often higher than recommended due to the incorrect belief that this will improve early and peak hatch. Male numbers may also remain higher than recommended when:

there is no means of disposing of males
male levels are simply not reduced
inappropriate male management reduces mating ratios such that fertility becomes poor and then mating ratios are held (or increased) in an attempt to help fertility.

Avoid having high male numbers as this will lead to overmating, feather damage, non-receptive females (due to poor feather cover and bullying) and poorer persistency (fertility) post-peak.

Body Weight and Persistency

Body-weight control is key in day-to-day management practices, but in many cases feed allocation simply follows a set “company” profile from one flock to the next. With feed prices contributing to 70 to 80 per cent of the cost of production, adjusting feed levels according to set “company” guidelines in order to stay within budgetary constraints may not allow for what a flock requires when it is over or under standard weight.

Body weight, persistency, and feed levels must be managed quantitatively:

reducing feed too aggressively or without allowing or compensating for an overweight flock will cause a drop in persistency, altering the balance of weight gain, egg production, and maintenance.
increasing feed too quickly to bring a flock back to target when it is underweight generally pushes birds overweight too quickly and reduces egg production.

When making any adjustments in feed level, it is essential to consider the impact that this has on total nutrient intake rather than just grams of feed per bird per day. Changes in daily energy and protein intake will affect body weight, egg weight, egg production, and egg mass.

If a flock is overweight for example, this weight difference from standard must be maintained if persistent production levels are also to be maintained. Giving more feed over the life of the flock, but ensuring correct total nutrient intake, will maintain egg production as a reward.

Figure 1. Relationship between body weight control, feed amount and production

Figure 1 shows a high peaking flock with a peak feed amount of 180g (6.3oz) per bird (i). The flock remains on this feed level until 35 weeks and feed withdrawal is 13 per cent from peak to 58 weeks (ii). Persistency is good even though body weight is still very high compared to standard. The increased feed level and appropriate feed withdrawal allowed this flock to maintain body weight without compromising production.

The balance of production, egg weight, maintenance, and body weight becomes even more critical for an underweight flock. If feed reduction is required, it is good practice to give two smaller feed changes over a seven-day period, rather than a larger, single reduction once a week. This allows the flock to adjust more gradually, maintaining balance of production, body weight and maintenance.

Egg Weight and Persistency

Along with body weight, monitor egg weight closely during the post-peak production period. Monitoring egg weights on a daily basis allows trends against standard to be plotted so that feed amounts can be adjusted appropriately. A change in trend of egg weight increase often occurs before a drop in egg production is seen and so can be the first indication of a potential problem.

A flock performing below standard for post-peak egg production and being overfed will show consistently (over a period of at least four days) higher than expected increases in daily egg weight away from the standard. Over-feeding a poor performing flock will have a negative impact, not only on production but also on overall hatchability due to a generally poorer egg shell quality in larger eggs. In this case, further feed removal will be required.

If feed is withdrawn too quickly or at too high a level for the egg output of the flock, a reduction in egg weight will precede a drop in production. If a consistent drop in egg weight (over a period of at least four days) occurs, feed should be given back to the flock.

Housing conditions related to persistency

Broiler breeder flocks may be challenged to varying degrees on a daily basis, however only the effects of larger challenges may be noticeable and seen as sudden or dramatic changes in physical flock performance. It is much more difficult to identify the ongoing, lesser challenges that may only be observed as a gradual change in flock persistency or reported fertility, particularly during the later stages of production. Housing conditions (Table 3) should be monitored on a regular basis and adjustments made where possible.

Table 3. Housing conditions affecting broiler breeder persistency

Key Management Points

monitor body weight and egg weight as part of the daily and weekly management schedule.
if birds are over standard body weight, maintain the difference between standard and actual body weight throughout the production period.
if birds are under standard body weight postpeak, remove feed in small amounts split over a seven-day period
adjust feed levels to maintain a regular and small weekly increase in body weight and egg weight
adjust feed levels to maintain body-weight gain, maintenance, and egg production.