End-of-Season Carcass and Reproductive Traits in
Shared by: qzl20249
2004 Poultry Science Association, Inc. End-of-Season Carcass and Reproductive Traits in Original and Replacement Male Broiler Breeders N. J. Wolanski,* R. A. Renema,* F. E. Robinson,*,1 and J. L. Wilson† *Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada, T6G 2P5; and †Department of Poultry Science, University of Georgia, Athens, Georgia 30602 Primary Audience: Hatching Egg Producers, Hatchery Specialists, Researchers SUMMARY Reproductive efficiency of male broiler breeders declines toward the end of a production cycle. It is common to add young, replacement males (spiking) to a breeder flock to maintain or increase fertility. To date, no study has reported if there are differences in the carcass and reproductive morphology between original and spiked males at the end of the breeding period. In this study, the weight, fleshing traits, footpad condition, and testes size of 327 Hubbard males (237 original and 90 replacement) from a commercial operation were examined. The original birds (63 wk of age) had significantly higher BW, breast weight, girth measurement, keel length, and spur length than the spiked males (48 wk of age). While external indicators of size and fleshing differed between replacement and original roosters, testis weight was not affected by the age of the bird. It was found that average testis weight correlated well with BW in birds in which testicular regression had not taken place but only weakly with spur length. Because original males had a higher BW and were more heavily fleshed than replacement males, their ability to successfully complete matings may have been impeded. Further research is needed to link growth profiles with semen quality, sexual behavioral, and longevity of a male breeder in a commercial flock. Key words: broiler breeder males, replacement males, testis weight, testicular regression, fleshing 2004 J. Appl. Poult. Res. 13:451–460 DESCRIPTION OF PROBLEM insemination . The reduction of fertility ob- served in naturally mating flocks may be associ- Broiler stocks have been intensively selected for growth rate, feed efficiency, and breast muscle ated with increased BW of roosters toward the mass. Genetic progress in these traits can impact end of lay  or a decrease in libido of older reproductive fitness [1, 2]. Although female ef- males . It has been suggested that the frequency fects on a flock with poor fertility cannot be dis- of successful copulations may be reduced by car- missed , the male most strongly influences cass characteristics, such as excessive chest girth, fertility in the later stages of production. Flock which can lower flock fertility. Considerable vari- fertility can be maintained with the use of artificial ability in reproductive performance between indi- 1 To whom correspondence should be addressed: firstname.lastname@example.org. 452 JAPR: Research Report vidual males  occurs with some males were managed according to standard Western Ca- maintaining high rates of fertility, while other nadian industry conditions. Males were reared males may be subfertile or infertile or may have sex-separate in light-tight housing with an initial undergone testicular regression. photoperiod of 24 h light. On d 4, the day length The use of external traits, such as BW, leg was reduced to 12.5L:11.5D until wk 4, when it conformation, and secondary sex characteristics was further decreased to 8.5L:15.5D. At 17 wk as indicators of male fertility in broiler breeders of age, 300 males were selected from the rearing has been studied . It was found that musculo- barn based on BW and were cohoused with 4,860 skeletal characteristics, rather than BW alone, are pullets. The flock was photostimulated at 23 wk closely associated with a male’s ability to copulate with a single step increase in day length to successfully. Recent research  has shown that 14L:10D. Day length was increased to 15L:9D at low fertility toward the end of lay may be a result wk 26 and further increased to 16 h at 28 wk. At of poor semen transfer due to males becoming 28 wk of age, an additional 45 males were added too large to attain full cloacal contact with the from the original flock to replace mortality and hens. Hocking and Duff  noted that increased to bring male numbers up to 6.8% of the hen flock. male BW, which is common in late production, By 45 wk of age male numbers had dropped was negatively correlated with fertility in naturally to 271 (6.2% of female flock). Ninety replacement breeding flocks. Up to peak lay, the original males males were added to the original flock as part of can maintain fertility. However, shortly thereafter the male spiking program. The new males were fertility tends to decline. Hatching egg producers 30 wk old at the time of introduction to the mature commonly supplement flocks with young, re- breeding flock and had been reared identically to placement males at 40 to 45 wk of lay (spiking). the original males until 23 wk of age. However, At the time of spiking, poorer performing original replacement males were kept in the rearing facility males may then be culled. Addition of replace- at a photoperiod of 8.5L:15.5D until 30 wk of ment males may improve or maintain the fertility age. Photostimulation (16L:8D) coincided with of a flock. movement to the laying barn. The first objective of this study was to deter- Both the replacement and original males were mine if replacement males differ from original feed restricted from 2 wk of age until the end of males in carcass characteristics (chest girth, keel production in accordance with the Hubbard BW length, shank length, and spur length, BW, and guidelines. Two percent of the males were testes weight) at the end of a production cycle. weighed every 4 d to obtain an average weight The second objective was to study external fac- of the males then feed allocation was determined. tors, such as footpad score and feathering score The males were reared on a grower ration with within the original and the replacement groups, 2,620 kcal/kg ME and 17% CP. The male breeder and to assess the impact of body size on these ration contained 2,660 kcal/kg ME and 16.1% traits. The entire male population was divided into CP. Nipple drinkers provided the males with chlo- LOW (<4,000 g), standard (STD) (4,001 to 4,900 rinated water, available ad libitum throughout g), and HIGH (>4,900 g) BW categories and com- rearing and breeding. The University of Alberta, pared within the original and replacement male Faculty of Agriculture, Forestry and Home Eco- groups to assess the effect of relative body size nomics, Animal Policy and Welfare Committee on carcass and reproductive traits. The impact of approved this experimental protocol, under the BW on foot condition and reproductive status was guidelines of the Canadian Council of Animal of particular interest, as well as the comparison Care . of these traits between the original and replace- ment males. Data Collected MATERIALS AND METHODS Following removal of the hens from the barn at 63 wk of age, all remaining males (n = 327) Breeder Management were wing-banded and sorted into the original (63 A commercial flock of 4,950 Hubbard Hi-Y wk of age) and replacement (48 wk of age) groups. hens and 624 Hubbard Hi-Y males  (original) Visually, the original males had longer, sharper WOLANSKI ET AL.: MALE BREEDER END-OF-SEASON TRAITS 453 spurs, while the younger replacement males had 5,200 g, whereas 33/237 or 13.9% of original rounded, small smooth spurs. males had a BW of greater than 5,200 g. The girth of the thoracic cavity was measured Fertility problems are associated with in- on each live male with a fabric tape measure using creased male BW [15, 16]. As the original males the notch of the keel as a reference point. The in the current study were heavier than the replace- males were killed by cervical dislocation. A feath- ment males, their size may have contributed to a ering score was assigned based on the relative decline in reproductive effectiveness later in the feather cover of the bird’s back area using a 6- breeder period. Of the original males, 23.6% were point scale described by Sikur et al. . Footpad in the HIGH (>4,900 g) size category compared condition was evaluated on a 3-point scale in with only 4.4% of the replacement males (Table which a score of 1 was for poor footpad condition 2). More of the replacement males fit in the LOW characterized by large, open sores or severe le- (<4,000 g) size category, with 40.0% of the birds sions, a score of 2 for average footpad condition here compared with 14.3% of the original birds. characterized by few open sores or swollen le- sions, and a score of 3 for good footpad condition Breast Muscle and Fleshing Traits characterized by little to no open sores or swol- The additional weight (477 g) of the original len lesions. compared with the replacement males also im- Birds were individually weighed, and the pacted the fleshing of the birds (Table 1). The length of the shank and spur were recorded. The average breast muscle weight of the original group breast muscle (pectoralis major and minor) and the was 678.4 g while that of the replacement males testes were dissected from each bird and weighed. was 575.9 g (Table 1). This difference in breast Any abnormalities, such as testicular regression, muscle weight similarly affected the chest girth were recorded. A bird was considered to have and keel length measurements. The chest girth of regressed testicles if the average testis weight of the original males was 3.9% greater than that of the bird was less than 4 g. The birds were sorted the replacement males and keel length was 1.0% into uniform body size groups around the mean greater (Table 1). Even when compared on a per- flock BW to assess the impact of size on reproduc- centage basis, the breast muscle weight of the tive traits in the original and replacement male original males (14.7%) was greater than that of populations. The 3 BW groups were LOW the replacement males (14.0%). The data in Table (<4,000 g), standard (STD) (4,001 to 4,900 g), 3 illustrate that breast weight, chest girth, and keel and HIGH (>4,900 g), irrespective of whether length were significantly and positively correlated birds were original or replacement males. The with BW (r = 0.88, 0.68, 0.56, respectively; P < data were analyzed using SAS  with standard 0.001). These findings are in agreement with those statistical methods . of Bjerstedt et al.  who illustrated that breast weight was highly correlated with BW in 62-wk- RESULTS AND DISCUSSION old laying hens. Keel length also correlated well BW with breast muscle weight (r = 0.52), indicating that a larger keel length in a bird allowed more The mean BW of the 327 males processed at space for breast muscle deposition, which may 63 wk was 4,442 g. The weights were normally be a result of indirect selection for breast muscle distributed around this value (Figure 1A). Ap- mass in broiler offspring. proximately 80% of the birds were within ±15% The older group of original males tended to of the mean BW, suggesting that the flock was have more breast muscle deposition, which may highly uniform in BW. However, when the total have a negative impact on mating ability. Previous population was sorted into replacement and origi- research has related the decrease of fertility in nal groups, the original males were found to be heavier males to an increase in breast fleshing, significantly heavier than replacement males (Ta- which impedes the large-breasted males from at- ble 1). The normally distributed subpopulation of taining full cloacal contact with females [5, 18]. replacement males represented a large proportion Genetic selection for growth traits has altered BW of the lower end of the BW spectrum in this flock and muscle distribution of the broiler breeder, (Figure 1B). No spiked birds had a BW of over with the frame of the birds also likely changing 454 JAPR: Research Report FIGURE 1. Frequency of distribution of the total population (A) of 327 broiler breeder males and of the 90 replacement (48 wk of age) and 237 original (63 wk of age) males (B) sorted into 10 BW groups. to carry the redistribution of muscle . The When the original and replacement males stance and leg dimensions of the male have been were sorted into the 3 BW categories, breast mus- changing as breast muscle mass has increased, cle weight, chest girth, and keel length differences which together may further affect the ability of followed the pattern of BW differences (Table 2). the male to achieve cloacal contact during mating. The good correlation of breast muscle weight with WOLANSKI ET AL.: MALE BREEDER END-OF-SEASON TRAITS 455 TABLE 1. Mean values (±SEM) for carcass and reproductive traits of original (63 wk of age) and replacement (48 wk of age) broiler breeder males Parameter Original Replacement n 237 90 BW (g) 4,573 ± 34a 4,096 ± 54b Breast muscle weight (g) 678.4 ± 8.4a 575.9 ± 13.7b (% of BW) 14.73 ± 0.11a 13.97 ± 0.18b Chest girth (cm)A 39.8 ± 0.1a 38.3 ± 0.2b Keel length (mm) 191.9 ± 0.5a 190.0 ± 0.7b Abdominal fat pad incidence (%)B 21.94 ± 0.03a 12.22 ± 0.04b Shank length (mm) 139.8 ± 0.4b 140.3 ± 0.7a Spur length (mm) 23.7 ± 0.3a 13.9 ± 0.5b Comb height (mm)C 66.3 ± 0.8 66.2 ± 1.3 Testes traits Left testis weight (g) 15.9 ± 0.4 15.9 ± 0.6 Right testis weight (g) 14.1 ± 0.4 13.6 ± 0.6 Mean testis weight (g) 15.0 ± 0.4 14.7 ± 0.6 (% of BW) 0.325 ± 0.008b 0.356 ± 0.012a Means within a row with different subscripts are significantly different (P < 0.05). a,b A Girth = bird circumference using notch of keel as reference point. B Birds possessing a discernable abdominal fat pad. C Height measured from top of head to tip of third spike from the front of the comb. chest girth and keel length (Table 3) demonstrates While it may be assumed that the heavy birds the usefulness of these noninvasive, external indi- had excessive breast muscle deposition, the low cators of fleshing. Within the original males, the amount of fleshing observed in the LOW males breast muscle of the HIGH, STD, and LOW males may also require attention. It is not known if these represented 16.0, 14.6, and 13.3% of BW, respec- males were relatively low weight (and under- tively (Table 2). The larger birds were carrying fleshed), when they entered the breeding barn, or a significantly greater proportion of breast muscle. if their BW and condition deteriorated during the While a similar relationship existed among the breeding period. During rearing, males that start replacement male groups, the HIGH replacement out smaller or larger will typically remain at their males carried a similar proportion of breast muscle end of the size distribution . When males are to the STD males. As the HIGH replacement subjected to the sperm quality index test, those group contained only 4 birds, the means for this with scores in the lowest, most inferior quartile group had a higher level of variance than the also have the lowest BW, while those in the upper means for the lighter replacement males. The quartiles are statistically similar in BW . breast muscle and fleshing traits for the original While differences in physiological measures of and replacement males within a body size cate- male quality have been observed, elevated mating gory appeared similar (Table 2). Overall differ- activity may have a more critical role in optimiz- ences between the original and replacement males ing flock fertility . The 2 extremes in male presented in Table 1 were primarily due to there flock BW and fleshing are both problematic for being few HIGH males within the replacement flock fertility. male population, which skewed the results for Abdominal Fat Pad this population down. Body weight was the most important affecter of breast muscle weight and Abdominal fat pads were not detectable in fleshing traits. Increased breast muscle deposition the majority of the males. Whereas 21.9% of was associated with age, with the older, original the original males had a visible abdominal fat male population containing a higher proportion deposit, only 12.2% of the replacement males of heavily fleshed, HIGH birds (Table 2). did (Table 1). This suggests that the older (and 456 JAPR: Research Report TABLE 2. Mean values (±SEM) for carcass and reproductive traits of original (63 wk of age) and replacement (48 wk of age) broiler breeder males sorted on the basis of BW into 3 groups Weight categoriesA Parameter LOW STD HIGH Original males n 34 147 56 BW (g) 3,773 ± 45c 4,488 ± 22b 5,284 ± 35a Breast muscle weight (g) 504.4 ± 14.6c 655.1 ± 7.0b 845.2 ± 11.4a (% of BW) 13.33 ± 0.25c 14.58 ± 0.12b 15.98 ± 0.20a Chest girth (cm)B 38.0 ± 0.3c 39.5 ± 0.2b 41.8 ± 0.2a Keel length (mm) 186.4 ± 1.1c 191.3 ± 0.5b 197.0 ± 0.8a Abdominal fat pad incidence (%)C 35.3 ± 0.1a 19.1 ± 0.0b 21.4 ± 0.1ab Shank length (mm) 135.3 ± 1.1c 139.7 ± 0.5b 142.8 ± 0.9a Spur (mm) 22.5 ± 0.8b 23.3 ± 0.4b 25.5 ± 0.6a Comb height (mm)D 65.6 ± 2.2 67.3 ± 1.1 64.2 ± 1.7 Testes traits Left testis weight (g) 10.8 ± 1.0c 15.7 ± 0.5b 19.3 ± 0.7a Right testis weight (g) 9.7 ± 0.9c 13.8 ± 0.4b 17.3 ± 0.7a Mean testis weight (g) 10.2 ± 0.9c 14.8 ± 0.4b 18.3 ± 0.7a (% of BW) 0.272 ± 0.020b 0.329 ± 0.009a 0.347 ± 0.015a Replacement males n 36 50 4 BW (g) 3,655 ± 44c 4,342 ± 37b 4,986 ± 131a Breast muscle weight (g) 494.0 ± 14.1c 618.4 ± 11.9b 782.6 ± 42.2a (% of BW) 13.41 ± 0.28b 14.24 ± 0.24a 15.69 ± 0.84a Chest girth (cm)B 37.1 ± 0.2b 39.0 ± 0.2a 40.2 ± 0.6a Keel length (mm) 186.5 ± 1.0c 191.7 ± 0.9b 199.8 ± 3.1a Abdominal fat pad incidence (%)C 11.1 ± 0.1 12.0 ± 0.1 25.0 ± 0.2 Shank length (mm) 138.7 ± 1.1b 140.9 ± 0.9b 147.8 ± 3.3a Spur length (mm) 12.7 ± 0.6b 14.6 ± 0.5a 16.9 ± 1.9a Comb height (mm)D 64.6 ± 1.5 67.0 ± 1.3 70.3 ± 4.6 Testes traits Left testis weight (g) 12.9 ± 0.9b 18.0 ± 0.8a 15.9 ± 2.8ab Right testis weight (g) 11.0 ± 0.8b 15.4 ± 0.7a 13.9 ± 2.3ab Mean testis weight (g) 12.0 ± 0.8b 16.7 ± 0.7a 14.9 ± 2.5ab (% of BW) 0.322 ± 0.020b 0.386 ± 0.017a 0.299 ± 0.060ab a–c Means within a row with different subscripts are significantly different (P < 0.05). A Divided into uniform groups around the mean flock BW. LOW = <4,000-g birds; standard (STD) = 4,001- to 4,900-g birds; HIGH = >4,900 g. B Girth = bird circumference using notch of keel as reference point. C Birds possessing a discernable abdominal fat pad. D Height measured from top of head to tip of third spike from the front of the comb. heavier) males may have begun to divert nutri- fat was not correlated with birds that had under- ents from mating activities to storage. There was gone testicular regression within the LOW or no significant effect of BW grouping on abdomi- any body size group, which would have been a nal fat pad incidence in replacement males, possible explanation. However, to put the small whereas 35% of the LOW, original males had (approximately 10 g) fat pad weights of males a detectable fat pad compared with 19% of the in perspective, the mean fat pad weight of a STD birds (Table 2). The presence of abdominal feed-restricted broiler breeder female at 54 wk WOLANSKI ET AL.: MALE BREEDER END-OF-SEASON TRAITS 457 TABLE 3. Correlation coefficients (and P-values) of carcass and reproductive traits of original (63 wk of age) and replacement (48 wk of age) male broiler breeders Correlation coefficients (P-value) Breast Chest Keel Shank Foot muscle Mean testis Parameter girthA length length scoreB weight weight BW 0.6796 0.5633 0.3035 −0.2067 0.8822 0.4450 (0.0001) (0.0001) (0.0001) (0.002) (0.0001) (0.0001) Chest girth 0.3894 0.2083 −0.0984 0.6616 0.2589 (0.0001) (0.0001) (0.076) (0.0001) (0.0001) Keel length 0.3725 −0.1864 0.5247 0.1631 (0.0001) (0.0007) (0.0001) (0.0031) Shank length −0.2732 0.2404 0.0501 (0.0001) (0.0001) (0.37) Foot score −0.1857 −0.0916 (0.0008) (0.099) Breast muscle weight 0.3147 (0.0001) A Chest girth was a measure of the birds circumference using notch of keel as reference point. B Evaluated on a 1 to 3 scale as follows: 1 = poor condition characterized by large, open sores or severe lesions; 2 = average condition characterized by few open sores or swollen lesions; 3 = good footpad condition characterized by little to no open sores or swollen lesions. of age can be greater than 4.5% of the mature shown). Within the original and replacement hen BW . Male broiler breeders are feed male groups, 99.6 and 86.7% of the birds re- restricted and have low circulating levels of es- ceived a score of 6, which refers to birds with trogen, which virtually eliminates the coordi- no visible signs of bare skin on the back . nated, dramatic increase in lipid synthesis driven Only 1 original male and 12 replacement males by estrogen that occurs in the hen . Without had lower than the top feather score. Within the the stimulatory effects of estrogen on lipid depo- replacement male population, 10% of the birds sition, the male remains very lean throughout received a feather score of 3, referring to birds the first breeding cycle. with minimal feather cover on the back (6 to 30% feather cover) . The inferior feathering External Carcass Traits in these males appeared to be the result of in- The replacement group had a mean shank creased feather picking, which may have been length of 140.3 mm, which was significantly a consequence of establishment of a new social greater than the 139.8 mm for the original group order from when these males were introduced (Table 1). As both groups had achieved a mature to the barn. The feather scoring method used frame size, the slightly longer shank length of was limited to examination of the back feathers replacement males may be a reflection of their and did not assess feathering in the vent area, later photostimulation age. Long bone growth which could have provided positive identifica- generally ceases once reproductive hormone tion of sexually active males. concentrations rise during sexual maturation. The raw footpad condition score was 2.13 There were several relatively tall individuals in in the replacement group compared with a mean both the original and replacement groups. Shank score of 1.92 in the original group. Chi-squared length increased in the heavier BW groups of analysis demonstrated that the distribution of both the original and the replacement males (Ta- footpad condition scores in the original males ble 2). Clearly frame size is a major component was shifted toward poorer values than in the influencing mature BW. replacement males (Table 4). This may be a The feather score analysis was not very use- result of replacement males spending less time ful, as the majority of the birds received the in the breeding barn conditions or because they highest score due to good feathering (data not were typically lower in BW than the original 458 JAPR: Research Report TABLE 4. Foot scores of original (63 wk of age) and replacement (48 wk of age) broiler breeder males as groups and sorted on the basis of BW into 3 groups at 63 wk of age Foot scoreA Source 1 2 3 1 2 3 (birds, n) (birds, %) Male groupB Original 85 86 65 36.02 36.44 27.54 Replacement 18 42 30 20.00 46.67 33.33 InteractionC Original-LOW 8 14 12 23.52 41.18 35.29 Original-STD 53 50 43 36.05 34.01 29.25 Original-HIGH 24 22 10 42.86 39.29 17.86 Replacement-LOW 6 15 15 16.67 41.67 41.67 Replacement-STD 12 25 13 24.00 50.00 26.00 Replacement-HIGH 0 2 2 0.00 50.00 50.00 A Evaluated on a 1 to 3 scale as follows: 1 = poor condition characterized by large, open sores or severe lesions; 2 = average condition characterized by few open sores or swollen lesions; 3 = good footpad condition characterized by little to no open sores or swollen lesions. B Original males had more birds with poor footpad scores (Fisher’s exact test P = 0.018). Original males total is 236 due to missing data for 1 male. C Footpad scores not significantly different between original and replacement males for LOW (<4,000 g) (P = 0.74), standard (STD) (4,001 to 4,900 g) (P = 0.13), and HIGH (>4,900 g) (P = 0.14) body size groups. males. Body size may be an important factor in and replacement male groups (Table 2). footpad score. While the footpad score distribu- VonSchantz et al.  reported that spur length tions of original and replacement males within and testis mass were positively correlated. Spur each body size group were not significantly dif- length was weakly but significantly correlated ferent (Table 4), the original males included a with average testis weight within the original greater proportion of HIGH males, of which male (r = 0.11) and replacement male (r = 0.20) 43% received a score of 1, indicating poor foot- groups. This relationship may be primarily a pad condition. If the foot lesions or sores are result of BW. severe, they may have a negative influence on The height of the comb did not differ be- a male’s ability to mate. Lighter males would tween male groups (Table 1) or among body place less stress on their footpads. Previous re- size classes within these groups (Table 2). Comb search has shown that broiler footpad condition height did not correlate with reproductive traits could be adversely affected if proper litter, venti- in this study and was not a useful indicator of lation, and temperatures were not maintained in reproductive status. Comb height has previously the barn . been used as an indicator of testes weight and The 237 original males had a mean spur fertility. However, a very diverse population length of 23.7 mm, which was significantly may be required to see this effect, and it also greater than 90 replacement males, with their appears to vary by strain . mean spur length of 13.9 mm (Table 1). It is clear that the spurs continue to grow within the Testis Weight time frame of a typical breeding period. Within the original and replacement male populations, The mean values of the left testis, right testis, the LOW males had shorter spurs than either and average testis weight did not differ between STD or HIGH males (Table 2). The HIGH origi- replacement and original males (Table 1). When nal males had a significantly longer spur length comparing the testicular size of males within the than the STD males, while it was only numeri- replacement and original groups, 13 of the 237 cally increased in the small group of HIGH re- original males (5.5%) had undergone testicular placement males. There was a 3-mm difference regression, whereas only 2 of 90 (2.2%) replace- in spur length between HIGH and LOW original ment males had regressed testes (<4 g). The fact WOLANSKI ET AL.: MALE BREEDER END-OF-SEASON TRAITS 459 that a higher percentage of older males (original up a smaller proportion of BW than in the larger males) had undergone testicular regression sug- body size groups. A similar comparison existed gests that age may influence reproductive fit- between the LOW (12.0 g) and STD (16.7 g) ness. It has been observed that more groups within the replacement males (Table 2). seminiferous epithelium is atrophied in 160-wk Average testis weight was positively correlated old male Japanese quail than in young quail, with BW (r = 0.445) (Table 3), further support- suggesting an age-related decline in sperm out- ing the link between larger males and greater put . Hence, it may be likely that original absolute testis weights relative to smaller males. males were experiencing testicular regression This is in agreement with the findings of Wilson due to advanced age. Following testicular regres- et al.  who found that testis weight of males sion, blood plasma testosterone concentrations was positively correlated with BW. falls as the Leydig cells no longer produce high However, both Brown and McCartney  levels of this sex hormone. This could explain and Wilson and McDaniel  have reported why Duncan et al.  observed a significant that birds possessing larger testes did not pro- decrease in male libido with age. Declines in duce the most semen. Nutrient intake can also be male fertility are more likely to be due to the a factor in the maintenance of sperm production. loss of effectiveness of specific individuals Bramwell et al.  reported that reduced energy rather than to widespread declines in reproduc- diets contributed to reduced testes weights and tive status. resulted in the production of hatching eggs with Overall, the left testis was on average 1.8 to reduced fertility. Broiler breeder males main- 2.3 g heavier than the right in both original and tained on a severe feed restriction program have replacement male groups (Table 1). While this been found to have a decreased semen volume phenomenon has been shown to be true in mam- mals as well , an explanation for this obser- and sperm concentration per ejaculate . If vation has not been reported. small males are being out-competed for access Although there was no significant effect on to feed, there can be direct effects on the testes. testis weight when the birds were sorted based Further complications in this relationship may on age, there was a significant effect when these arise from factors, such as sperm mobility, in groups were subdivided into the LOW, STD, which high mobility has been shown to improve and HIGH BW groups (Table 2). None of the fertility but be associated with lighter males . regressed males were in the HIGH body size Ultimately, mating behavior will determine the group. Mean testis weight increased in the larger reproductive effectiveness of the male flock. En- body size groups within the original males, aver- suring that the most reproductively active males aging 10.2, 14.8, and 18.3 g in LOW, STD, and are also the most reproductively fit should be HIGH males, respectively (Table 2). Within the an integral part of future breeder management original-LOW males, mean testis weight made programs. CONCLUSIONS AND APPLICATIONS 1. The primary difference between original and replacement males at the end of a breeding cycle is BW. 2. Age had little effect on carcass traits within LOW or STD body size ranges. The characteristics of original and replacement males in these categories were comparable. There were not enough replacement-HIGH birds for an effective comparison to the originals. 3. Small males have less breast muscle mass, determined by live-bird fleshing measurements as well as by necropsy at the end of the laying period. 4. Most male broiler breeders do not have a detectable deposition of abdominal fat at the end of the breeding period. 5. Absolute testis weight did not differ between original and spiking males. However, there was a trend to higher incidence of testicular regression in the former. Testes weights were highly correlated with BW but only weakly correlated with spur length. 460 JAPR: Research Report 6. This study examined the relationship between male age and reproductive condition in a commer- cial male population, as it is affected by body size. Further research is needed to link the long- term impact of variation in juvenile and prepubertal growth curve on semen quality, sexual behavior, and longevity of a male breeder in a commercial flock. REFERENCES AND NOTES 1. Wilson, H. R., N. P. Piesco, E. R. Miller, and W. G. Nesbeth. 18. Soller, M., H. Schindler, and S. Bornstein. 1965. Semen 1979. Prediction of the fertility potential of broiler breeder males. characteristics, failure of insemination and fertility in Cornish and Worlds Poult. Sci. J. 35:95–118. White Rock males. Poult. Sci. 44:424–432. 2. Siegel, P. B., and E. A. Dunnington. 1985. Reproductive 19. Renema, R. A., F. E. Robinson, M. Newcombe, and R. I. complications associated with selection for broiler growth. Pages McKay. 1999. Effects of body weight and feed allocation during 55–72 in Poultry Genetics and Breeding. W. G. Hill, J. M. Mason, sexual maturation in broiler breeder hens. 1. Growth and carcass and D. Hewitt, ed. Br. Poult. Sci. Ltd., Longman Group, Harlow, UK. characteristics. Poult. Sci. 78:619–628. 3. Bramwell, R. K., C. D. McDaniel, W. H. Burke, J. L. Wilson, 20. Karaca, A. G., H. M. Parker, J. B. Yeatman, and C. D. and B. Howarth. 1996. Influence of male broiler breeder dietary energy intake on reproduction and progeny growth. Poult. Sci. McDaniel. 2002. The effects of heat stress and sperm quality classifi- 75:767–775. cation on broiler breeder male fertility and semen ion concentrations. Br. Poult. Sci. 43:621–628. 4. Brillard, J. P., and G. R. McDaniel. 1986. Influence of sperm- atazoa numbers and insemination frequency on fertility in dwarf 21. Bilcik, B., I. Estevez, and M. R. Luque. 2002. Impact of broiler breeder hens. Poult. Sci. 65:2330–2334. male-male competition and morphological traits on reproductive be- havior in broiler breeders. Poult. Sci. 81(Suppl. 1):5. (Abstr.) 5. Hocking, P. M., and S. R. I. Duff. 1989. Musculo-skeletal lesions in adult male broiler breeder fowl and their relationships 22. Joseph, N. S., F. E. Robinson, R. A. Renema, and M. J. with body weight and fertility at 60 weeks of age. Br. Poult. Sci. Zuidhof. 2002. Responses of two strains of female broiler breeders 30:777–784. to a mid-cycle increase in photoperiod. Poult. Sci. 81:745–754. 6. Duncan, I. J. H., P. M. Hocking, and E. Seawright. 1990. 23. Dashti, N., J. L. Kelly, R. H. Thayer, and J. A. Ontko. 1983. Sexual behavior and fertility in broiler breeder domestic fowl. Appl. Concurrent induction of avian hepatic lipogenesis, plasma lipids, and Anim. Behav. Sci. 26:201–213. plasma apolipoprotein B by estrogen. J. Lipid Res. 24:368–380. 7. Reddy, R. P. K., and A. Sajadi. 1990. Selection for growth and semen traits in the poultry industry: What can we expect in the 24. Ekstrand, C., T. E. Carpenter, I. Anderson, and B. Algers. future? Pages 47–59 in Control of Fertility in Domestic Birds. J. P. 1998. Prevalence and control of foot pad dermatitis in broilers in Brilliard, ed. INRA, Paris. Sweden. Br. Poult. Sci. 39:318–324. 8. McGary, S., I. Estevez, M. R. Bakst, and D. L. Pollock. 25. VonSchantz, T., M. Tufvesson, G. Goransson, M. Grahn, M. 2002. Phenotypic traits as reliable indicators of fertility in male Wilhelmson, and H. Wittzell. 1995. Artificial selection for increased broiler breeders. Poult. Sci. 81:102–111. comb size and its effects on other sexual characters and viability in Gallus domesticus (the domestic chicken). Heredity 75:518–529. 9. McGary, S., I. Estevez, and M. R. Bakst. 2003. Potential relationship between physical traits and male broiler breeder fertility. 26. Ottinger, M. A., and S. L. Gorham. 1986. Histological and Poult. Sci. 82:328–337. neuroendocrine correlates of the age-related reproductive decline in 10. Hubbard-ISA. Duluth, GA. male quail. Poult. Sci. 65(Suppl. 1):100. (Abstr.) 11. Canadian Council on Animal Care. 1984. Guide to the care 27. Duke, H., and M. J. Swenson. 1993. Duke’s Physiology of and use of experimental animals. Vol. 2. Canadian Council on Animal Domestic Animals. 10th ed. Book News, Inc., Portland, OR. Care, Ottawa, ON, Canada. 28. Wilson, J. L., L. M. Krista, G. R. McDaniel, and C. D. 12. Sikur, V. R., F. E. Robinson, D. R. Korver, R. A. Renema, Sutton. 1988. Correlation of broiler breeder male semen production and M. J. Zuidhof. 2004. Effects of nutrient density on growth and and testes morphology. Poult. Sci. 67:660–668. carcass traits in fast- and slow-feathering female turkeys. Poult. Sci. 83:1507–1517. 29. Brown, H. B., and M. G. McCartney. 1983. Effects of dietary restriction on reproductive performance of broiler breeder males. 13. SAS Institute. 1999. SAS/STAT User’s Guide. Version 8. Poult. Sci. 62:1885–1888. SAS Institute Inc., Cary, NC. 14. Body weight and carcass characteristic data were analyzed 30. Wilson, J. L., and G. R. McDaniel. 1987. Dietary protein by 1-way ANOVA  comparing the original to the replacement levels for broiler breeder males. Poult. Sci. 66:237–242. males. One-way ANOVA was used within the original and the re- 31. Sexton, K. J., J. A. Renden, D. N. Marple, and R. J. Kemp- placement male groups to compare body size groups. Pearson correla- painen. 1989. Effects of ad libitum and restricted feeding on semen tion analysis  was performed to assess relationships between the quantity and quality, body composition, and blood chemistry of caged parameters measured. The footpad score data underwent chi-squared broiler breeder males. Poult. Sci. 68:569–576. analysis using Fisher’s exact test . Significance was assessed at the P < 0.05 level. 32. Bowling, E. R., D. P. Froman, A. J. Davis, and J. L. Wilson. 15. Kondra, P. A., and R. N. Shoffner. 1955. Heritability of some 2003. Attributes of broiler breeder males characterized by low and body measurements and reproductive characters in turkeys. Poult. high sperm mobility. Poult. Sci. 82:1796–1801. Sci. 34:1262–1267. 16. Ogasawara, F. X., H. Abplanalp, and V. S. Asmundson. Acknowledgments 1963. The effect of selection for body weight on reproduction in turkey hens. Poult. Sci. 42:838–842. Randy Kasa from Kasa Farms is to be wholeheartedly acknowl- 17. Bjerstedt, H. L., F. E. Robinson, R. T. Hardin, and T. A. edged for donating his birds and assisting with the project. The Wautier. 1995. Carcass traits and reproductive organ morphology in support provided by staff and students of the Alberta Poultry Research 62-week-old SCWL hens. Can. J. Anim. Sci. 75:341–344. Center is also gratefully acknowledged.