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Poult Sci 2008. 87:805-811. doi:10.3382/ps.2007-00285
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PRODUCTION, MODELING, AND EDUCATION

Feeding Broiler Breeder Males. 4. Deficient Feed Allocation Reduces Fertility and Broiler Progeny Body Weight

H. Romero-Sanchez*, P. W. Plumstead{dagger}, N. Leksrisompong{dagger}, K. E. Brannan{dagger} and J. Brake{dagger},1

* University of Antioquia, AA1226 Grupo Grica, Faculty of Agriculture, Medellin, Columbia; and {dagger} North Carolina State University, Department of Poultry Science, Box 7608, Raleigh, NC 27695-7608

1 Corresponding author: jbrake{at}ncsu.edu


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
Two experiments were conducted to evaluate the effects of male broiler breeder feed intake on broiler progeny performance. In experiment 1, a low cumulative nutrition program supplied 29,580 kcal of ME and 1,470 g of CP, whereas a high cumulative nutrition program supplied 33,500 kcal of ME and 1,730 g of CP to photostimulation at 21 wk of age. Two diets (HiDiet and LoDiet) were formulated, and a single feeding program was used to achieve the selected nutrient intakes. The HiDiet group of males in experiment 1 achieved greater BW and exhibited lower fertility when fed as the LoDiet males from the onset of egg production. The HiDiet breeder males subsequently produced male broilers from eggs laid at 29 wk of age that exhibited lower BW at 42 d. This was due to the heaviest 50% of the breeder males in this treatment not gaining BW consistently due to less-than-adequate ME intake relative to their greater BW requirements. Two feeding programs during the production period (constant or increasing) were compared in experiment 2. Broilers were hatched from eggs laid at 32 and 48 wk of age to evaluate the vertical effect of male treatments on progeny performance. No difference in fertility or broiler performance was found at 32 wk. However, the constant feeding program produced lower fertility from 36 to 55 wk of age, and this resulted in a lower male and female broiler progeny BW at 42 d of age from eggs collected at 48 wk of age. Adequate breeder male feed allocation during the production period improved fertility and favorably affected broiler progeny performance in both experiments. However, broiler progeny effects were observed only when there were differences in fertility, which suggests that the males with the greatest genetic potential were not mating at these times.

Key Words: broiler breeder male • rearing nutrition • fertility • broiler performance


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
Genetic selection has been very successfully used by the broiler industry to improve expression of highly heritable traits such as BW, breast muscle yield, and feed efficiency. However, these genetic improvements may be accompanied by a decline in broiler breeder reproductive variables (Goerzen et al., 1996; Barbato, 1999) such as delayed sexual maturity and reduced fertility that have been generally associated with excess BW (Siegel and Dunnington, 1985; Hocking, 1990). Thus, elaborate feed restriction programs have been developed and routinely utilized to control broiler breeder BW, especially that of the male. However, it has been shown that broiler progeny BW can be negatively affected by less-than-adequate feed allocations to parent broiler breeder males (Attia et al., 1993, 1995).

A major problem encountered with commercial broiler breeder flocks has been the often dramatic decrease in fertility during the latter part of the laying period, particularly after 50 wk of age (Kirk et al., 1980; Walsh and Brake, 1997). It has been generally considered that the reduction in fertility was caused by a decline in mating activity that was largely attributable to the heavy BW and poor physical condition of older males (Hocking, 1990). However, other evidence has suggested that a ME deficit was a more likely cause of such male fertility problems (Buckner et al., 1986; Sexton et al., 1989a,b; Cerolini et al., 1995; Bramwell et al., 1996). It has also been demonstrated that poor fertility after 45 wk of age could be reversed by increasing the male feed allocation (Cerolini et al., 1995; Romero-Sanchez et al., 2007a,b). The objective of the present experiment was to provide divergent feeding programs that would influence the fertility of broiler breeder males and observe subsequent breeder BW, breeder fertility, and broiler progeny performance to determine if a vertical effect of broiler breeder male feed intake on broiler progeny performance could be discerned.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 REFERENCES
 
Experiment 1

Ross 344 (Aviagen Inc., Huntsville, AL) broiler breeder males were reared on 2 different cumulative feeding programs providing either 29,580 kcal of ME and 1,470 g of CP (considered the control) or 33,500 kcal of ME and 1,730 g of CP to produce either low or high planes of cumulative nutrition and BW at 21 wk of age, respectively. After 2 wk of starter feed (Table 1Go), 2 grower diets were fed (LoDiet and HiDiet; Table 1Go) in a manner that provided 2 cumulative nutrition treatments using a single feed allocation program as described previously (Romero-Sanchez et al., 2007c). From 21 to 24 wk of age, the HiDiet and LoDiet diets were proportionally blended to create a gradual transition to a single common breeder laying diet (2,930 kcal of ME/kg and 15.4% CP) that was fed during the production period (Table 1Go). All feeds were in a mash form.


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  		Table 1. Composition of breeder starter (0 to 2 wk), breeder grower (2 to 21 wk), breeder layer (22 to 64), broiler starter (0 to 3 wk), and broiler grower (3 to 6 wk) diets in experiment 1
 
Day-old chicks were permanently identified with both neck tags and wing bands and placed in a 20-pen growing house with 16 pens for Ross 308 slow-feathering females and 4 pens for males as described previously (Romero-Sanchez et al., 2007c). At placement, there were 68 females and 50 males in each female and male pen of experiment 1, respectively. After exposure to 23 h of light per day for 7 d, all birds were reared in a blackout house to 21 wk of age under an 8L:16D lighting program. Birds were moved at 21 wk of age to a curtain-sided, two-thirds slat and litter house where the photoperiod was extended with artificial light to 14 and 15 h at 22 and 24 wk of age and to 15.5 and 16 h at 5 and 50% rate of lay, respectively. All males were weighed individually at 21 wk of age. The BW of all males was ranked within each growing treatment irrespective of pen, and 96 of the original 200 males were then assigned to breeding pens in such a manner that each breeding pen had a similar BW distribution that reflected the overall BW distribution from light to heavy within each of the 2 growing treatments. Female pens were moved intact after excessively large and small females were removed. Thus, there were 55 females and 6 males allocated to each of the 16 breeding pens. Mortality was monitored daily, and male feed allocation was adjusted to maintain a programmed slow increase throughout the production period.

Male BW was thereafter determined individually at 22, 24, 28, 32, 36, 40, 48, 56, and 64 wk of age. Eggs were collected twice daily and stored in a cooler at 16°C and 70% RH until incubated. Incubation analysis was conducted on the basis of weekly sets of 60 eggs per replicate pen. All unhatched eggs were opened and examined macroscopically for evidence of embryological development and fertility by a single experienced individual. Chicks that hatched from eggs produced at 29 wk of age were grown as broilers as detailed below.

Experiment 2

Ross 308 slow-feathering female broiler breeder chicks and male Ross 344 male chicks were permanently identified with both necks tags and wing bands and then placed, respectively, into each of 12 female or 12 male floor pens located within a blackout rearing house as described by Romero-Sanchez et al. (2007a). From 0 to 2 wk, all birds received a starter feed followed by a grower diet to 24 wk and a layer diet from 25 to 64 wk of age (Table 2Go). All feeds were in a mash form. A more-than-adequate minimum intake of 31,460 kcal of ME and 1,669 g of CP (Brake, 2002) was attained at 21 wk of age. Broiler breeders were reared under a blackout lighting program and moved at 21 wk of age to a curtain-sided two-thirds slat and litter house where the photoperiod was extended with artificial light as described for experiment 1. An average of 200 females and 20 males were moved to each of the 12 breeding pens.


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  		Table 2. Composition of breeder starter (0 to 2 wk), breeder grower (2 to 21 wk), breeder layer (22 to 64), broiler starter (0 to 3 wk), and broiler grower (3 to 6 wk) diets in experiment 2
 
Two different feed allocation programs (constant or increasing) were applied after 26 wk of age (Romero-Sanchez et al., 2007b). The constant feeding program maintained 110 g/male per day throughout the production period, considered the control, whereas the increasing feeding program provided biweekly increments of 1 g from 26 to 42 wk and a similar increase every 4 wk from 42 to 62 wk until a daily feed intake of 123 g/male per day was reached. Male BW was measured individually at 20, 24, 28, 32, 36, 40, 48, 56, and 64 wk of age. Mortality was recorded daily, and feed allocation was corrected. Eggs were collected twice daily as in experiment 1. Fertility analysis was carried out as in experiment 1 on the basis of biweekly sets of 180 eggs per replicate pen. Chicks that hatched from eggs produced at 32 and 48 wk of age were grown as broilers as detailed below.

Broiler Trials

A broiler trial was conducted with eggs collected at 29 wk of age during experiment 1. The chicks were sexed at hatching, and 15 male chicks were allocated to each pen in a 32-pen house with 16 replicate pens per breeder feeding treatment. Eggs were collected at 32 and 48 wk of age in experiment 2. The chicks were sexed at hatch and allocated to a 72-pen house with 18 replicate pens of either 15 male or female chicks from each breeder feeding treatment. A single starter and grower diet that met or exceeded the NRC (1994) minimum suggestions was used from 0 to 21 and 21 to 42 d, respectively, in experiments 1 and 2 (Tables 1Go and 2Go). No finisher diet was used for the sake of simplicity.

Statistical Analyses

The GLM procedure of SAS Institute (2001) was used to analyze the broiler data and the continuous variables of the broiler breeder data. Fertility data was analyzed as categorical data (Walsh and Brake, 1997), where each individual egg was taken as a binomial event, either fertile or infertile, using the general model (GENMOD) procedure of SAS Institute (2001). Orthogonal contrasts were used to compare treatment probabilities (Giesbrecht and Gumpertz, 2004) where appropriate. To initially test the age effect and its interaction with the treatments, a split-plot design with age and the interaction in the subplot was conducted using PROC MIXED of SAS Institute (2001). These results have been previously reported (Romero-Sanchez et al., 2007a,b,c). When a broiler trial was conducted, fertility was analyzed on a weekly basis during the time period when eggs were collected for incubation. Means were partitioned using LSMEANS, and statements of statistical significance were based upon P < 0.05 unless otherwise stated.

A 1-way design was used to analyze all broiler breeder data on a weekly or biweekly basis, as appropriate, in the present study. Pen was the experimental unit, and during the production period of experiment 1, the 16 pens were divided between 2 rearing treatments (LoDiet and HiDiet) with 8 replicates per treatment based upon the male BW distribution procedure that was conducted at 21 wk. The 12 broiler breeder pens in experiment 2 were divided into 2 treatments with 6 replicates for each of the 2 feed allocation programs during the production period (constant or increasing).

For the broiler trials, a broiler sex effect was added as an additional factor in experiment 2 only. For the broiler trial of experiment 1 a 1-way design with 16 replicates per breeder feeding treatment was used, and for the broiler trial of experiment 2, a completely randomized design with a 2 x 2 factorial arrangement with 18 replicates per breeder male feeding treatment and broiler sex combination was used.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
REFERENCES
 
Experiment 1

Males subject to the high plane of rearing nutrition (HiDiet) in experiment 1 were previously reported (Romero-Sanchez et al., 2007c) to demonstrate a significantly higher BW during the rearing and early production periods, but differences diminished thereafter. The HiDiet males were also previously reported to exhibit lower fertility (Romero-Sanchez et al., 2007c). The effect of low and high cumulative nutrient intake during rearing on fertility from 28 to 33 wk of age and on 42-d male broiler BW from 29-wk-old breeders is depicted in Figure 1Go. Male broilers from the LoDiet treatment, compared with male broilers from the HiDiet treatment, exhibited greater BW at 42 d of age (P < 0.06). These findings could be explained with a simplistic approach. Males with greater BW at 21 wk of age would have had higher maintenance requirements, and, therefore, fewer nutrients (primarily ME) would have been available for growth and reproduction. In fact, due to the availability of individual BW data, when the males were divided into the 50% heaviest BW and the 50% lightest BW within each pen and tracked over time, it was observed that the 50% heaviest males from the HiDiet diet was the only group that did not continue to grow steadily after 28 wk of age (Figure 2Go). Failure to gain BW probably indicated a deficiency of ME. To further delineate this effect among the HiDiet males, the daily ME intake was compared with the calculated maintenance requirement (Combs, 1968) as shown in Figure 3Go; the heaviest 50% of the males were found to be relatively more restricted from 24 to 36 wk of age.


Figure 1
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  		Figure 1. Effect of the rearing broiler breeder male diet on fertility during the early production period and its effect on broiler progeny male BW at 42 d of age in experiment 1. Ross 344 males were fed diets containing either high (HiDiet) or low (LoDiet) nutrient density during rearing that produced either greater or less BW, respectively, at 21 wk of age. The 2 groups were then fed in a similar manner. The open circles and open bar represent the LoDiet treatment, whereas the closed squares and solid bar represent the HiDiet treatment. The plus symbol (+) indicates a numeric difference in fertility that approached significance (P < 0.1) at each age. The broiler BW effect was significant at P < 0.06.

 

Figure 2
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  		Figure 2. Broiler breeder male BW during the production period as affected by rearing diet in experiment 1. Ross 344 males were fed diets containing either high (HiDiet) or low (LoDiet) nutrient density during rearing that produced males with greater or less BW, respectively, at 20 wk of age. Males then received the same diet after 24 wk of age and were identified individually as being in either the 50% heavy BW and 50% light BW within experimental pens at 21 wk. Transition period indicates when the HiDiet and LoDiet were blended in various proportions.

 

Figure 3
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  		Figure 3. Energy balance for HiDiet (fed diet containing high nutrient density) males in experiment 1. Ross 344 males were fed a single diet providing 340 kcal/d of ME during the period shown above. Males were identified as being in either the 50% heavy BW or 50% light BW within each experimental pen at 21 wk to determine subsequent growth and fertility patterns. The ME requirement for maintenance (MEm) for the heavy BW and light BW birds within the HiDiet treatment was estimated as a function of the BW as MEm = 1.45 x BW0.65 x (1.78 – 0.012 x T), where T = average temperature in °F (Combs, 1968).

 
It has been well documented that BW at 8 wk (or similar juvenile age) has been an important tool in broiler selection (Siegel, 1963) for many years, with the larger BW males being used in subsequent generations. It would be reasonable to assume that the largest 50% of the HiDiet and LoDiet males would possess the same genetic potential, because both fairly represented the largest males in the population that were originally produced from the same grandparent flock. If this assumption were true, then the decreased broiler progeny BW observed would have to be due to reduced mating activity among the largest broiler breeder males that possessed the greatest genetic potential for broiler growth.

Experiment 2

No significant differences in fertility or BW were observed from 26 to 40 wk of age (Romero-Sanchez et al., 2007b). Because significant differences were not observed in fertility or broiler performance when the breeder flock was young (32 wk of age), no data were included herein, for the sake of brevity. Thereafter, the increasing feeding program during the production period produced a significantly increased breeder male BW (Romero-Sanchez et al., 2007b) and increased fertility (Figure 4Go) thereafter. Average male and female broiler BW at 42 d from eggs laid at 48 wk of age was significantly improved by the increasing feeding program. The explanation for these results should be similar to that of experiment 1. The gradual increase in feed allocation provided by the increasing program allowed the largest BW males with the greatest genetic potential to continue to mate and produce broiler progeny.


Figure 4
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  		Figure 4. Effect of the broiler breeder male feeding program during the production period on broiler breeder fertility and its effect on average male and female broiler progeny BW at 42 d in experiment 2. Ross 344 broiler breeder males were fed a single diet following an increasing or a constant program during the production period. The closed squares and solid bar represent the increasing treatment, whereas the diamonds and open bar represent the constant treatment. An asterisk (*) indicates a significant difference (P < 0.05).

 
Although high BW has been implicated to be the main cause of declining fertility, McGary et al. (2003) did not find a correlation between fertility and male BW or spermatozoal penetration of ova in 2 different broiler breeder strains. Therefore, it seems unlikely that BW per se directly affected male mating ability within the range of BW experienced in this study. In contrast, the present data present strong evidence to suggest that heavy males could be easily overrestricted and stop mating as a result of a nutrient deficiency, presumably ME. Thus, if the principle that the heaviest males were the first to cease mating as a result of a ME deficiency can be accepted, the genetic potential of these males would not be expected to appear in the progeny. This explanation would also seem to fit the data of Zhang et al. (1999), who showed that slow and consistent BW gain after sexual maturity was required to optimize the number of spermatozoa per ejaculate and semen production, especially during the late breeding period after 46 wk of age.

Some decline in fertility of broiler breeder flocks must be inevitable because of the normal aging process in females and males. Because fertility has been shown to be maintained toward the end of the production period by artificial insemination, it has been assumed that the decline in late fertility was predominantly a male problem (Brillard and McDaniel, 1986). Based on this, other authors have related decreased fertility to anatomical problems of overweight males that had difficulties achieving cloacal contact with hens (Soller et al., 1965; Hocking and Duff, 1989; Hocking et al., 1989). Other investigations have related fertility problems to leg problems of overweight males (Duff and Hocking, 1986). Based on these data, it would appear that the reduction in broiler breeder fertility that has been commonly observed in older commercial flocks could be attributed to a decreased mating efficiency, frequency, or both (Duncan et al., 1990), which in turn may be related to excessive male BW (Hocking and Bernard, 2000; Hocking and Robertson, 2000), lameness (Hocking and Duff, 1989; Hocking et al., 1989), or excessive restriction of nutrients (Cerolini et al., 1995).

Although effects on average breeder male performance must be important when considering flock fertility, it would be reasonable to assume that effects on fertility varied between individual males in relation to variations in individual BW vs. individual nutrient intake. Presumably, the largest males in a flock would be more subject to nutrient deficiencies (primarily ME) than smaller males and would be the first to show reduced semen production and mating activity. Evidence to support this hypothesis was provided by the results of the broiler trials conducted in this study. When there were no differences in fertility between male breeder treatments, there were also no differences in the performance of the broiler progeny, and the treatments that produced the lowest fertility also produced reduced 42-d broiler performance (Figures 1Go and 4Go). The most plausible interpretation of these data was that there was a reduction in the mating frequency of the heaviest broiler breeder males with the greatest potential to produce heavy BW progeny. Somewhat similar results have previously been reported by Attia et al. (1993, 1995), who provided broiler breeder males with different levels of daily ME intake and reported a significant increase in 42-d BW of offspring sired by males provided high ME intakes. These data suggested that although the decline in late broiler breeder fertility can be reduced by increased feed allocation to all birds in the flock, this practice may have the most benefit with the male broiler breeders that possessed the greatest BW. The benefits of providing sufficient nutrients to maintain mating behavior and libido of these birds was shown to not only increase the fertility of the flock as a whole but also to have positive effects of increasing the overall genetic potential of the broiler progeny for growth and feed efficiency.

Received for publication July 13, 2007. Accepted for publication December 10, 2007.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 REFERENCES
 
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