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Effects of Various Feeding Regimens on Reproduction in Broiler-Breeder Males
EDUCATION AND PRODUCTION Effects of Various Feeding Regimens on Reproduction in Broiler-Breeder Males E. A. FONTANA, W. D. WEAVER, JR., and H. P. VAN KREY Department of Poultry Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0332 (Received for publication March 16, 1989)
1990 Poultry Science 69:209-216 INTRODUCTION
Today's broiler-breeder is a product of intense genetic selection, nutritional advances, and systematic improvements in husbandry practices. The resulting progeny are characterized by rapid growth, excellent feed efficiency, and good body conformation. However, because of the negative genetic correlation between body size and reproduction (Siegel and Dunnington, 1985), the broiler industry has been forced to employ a number of management and nutritional schemes in order to maintain fecundity. Various levels of feed restriction, altered energy:protein ratios, or diets deficient in selected, essential amino acids have all been used to control growth. Arscott and Parker (1963) reported that feeding White Leghorn males a diet containing as little as 6.9% protein had no detrimental effect on semen volume or fertilizing capacity. Meyer et al. (1980) and Cecil (1981) observed that after turkeys attained sexual maturity, the volume and concentration of semen could be maintained satisfactorily with a diet containing 12% and 11% protein, respectively. When fed
to adolescent broiler-breeder males, diets containing 8.9% versus 16% protein significantly delayed sexual maturity but had no adverse effect on subsequent semen production, fertility, or hatchability (Wilson et al., 1971). Conversely, Wilson et al. (1987a) reported that broiler-breeder males fed a diet with 12 or 14% protein starting at 4 wk of age produced semen earlier and produced greater numbers of spermatozoa per ejaculate than did breeders fed a diet containing 16 or 18% protein. Individually caged broiler-breeder roosters fed a diet with 7% protein provided ad libitum or with a restricted feed intake on a diet with 16% protein produced semen of similar quality and fertilizing capacity (Bootwalla et al, 1988). Parker and McSpadden (1943) reported a progressive decrease in the volume, concentration, and fertilizing capacity of semen from Rhode Island Reds fed a diet restricted from 72 to 42% of that provided to controls fed on an ad libitum basis. However, McCartney and Brown (1980) found that restricting the diet of broiler-breeder males to 85 or 70% of the amount consumed by controls with ad libitum
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ABSTRACT A study was conducted using commercial broiler-breeder males and females maintained in alllitter pens and allowed to mate naturally. Using a separate feeding arrangement, males were given a diet containing either 12% or 14% protein. Body weights were maintained at either 90% or 100% of the recommended level. Females were provided feeders with grills which denied males access to the feed, while male feeders were elevated 46 cm above the floor to deny females access to that feed. In control pens, males and females ate from the same feeders and received a breeder diet with 14% protein. Eggs produced in pens where the males and females were fed separately showed significantly higher fertility (4.2%) than eggs from control pens. No differences in percentage fertility were noted between the two dietary-protein levels or body-weight groups of males fed separately. Furthermore, no differences were measured in percentage hatch of fertile eggs among any of the treatment groups. Males in control pens showed significantly heavier body weights and breast-angle measurements starting at 32 and 40 wk of age, respectively. No treatment effect was measured for male pododermatitis. The male control birds had heavier testes weights than the males in the groups with restricted body weights. However, semen concentration was not affected. This indicates that the improved fertility was related to the size and weight of the males, not to their ability to produce semen. The reduced fertility associated with excess male body weight may be both physical and physiological in nature. (Key words: broiler-breeders, fertility, body weight, separate feeding)
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MATERIALS AND METHODS
Rearing Period (0 to 20 Weeks of Age) Day-old, broiler-breeder chicks (100 Peterson males and 600 Hubbard females) were used. They were divided into 2 and 14 brooding pens (1.52 by 3.66 m, respectively), which were totally enclosed. A diet containing 16% protein and 2,897 kcal/kg of ME was provided on an ad libitum basis for the first 2 wk and was then restricted by weight and fed every other day (skip-a-day) for the remainder of the rearing period. Half of the birds in each pen were weighed weekly in order to estimate BW; feed allotments were adjusted to maintain BW within the range recommended by the primary breeders (Peterson Farms, 1986; Hubbard Farms, 1987). Water was available ad libitum. Light was provided for 24 h at 20 lux for the first 3 days, then reduced to 8 h per day at that same intensity for the remainder of the rearing period. All birds were beak-trimmed at 10 days of age, following the recommendations of the primary breeders. Production Period (20 to 65 Weeks of Age) At 20 wk of age, 500 pullets and 50 cockerels were randomly selected and were equally
distributed among 10 breeder pens (2.44 by 4.88 m). All pens had a window (1.5 by 1.8 m) with a southern exposure. For the male breeders, the following dietary and feed-restriction treatments, which were replicated, were imposed in a factorial arrangement: A. Controls. The males and females were allowed to eat from the same feeders and were given a diet containing 14% protein and 2,922 kcal/kg of ME (Table 1). Feed allocations were based on maintaining the hens at the body weight and level of egg production recommended by the primary breeder. As a result, male feed consumption and, thus, body weight were only partially restricted. B. CP14%, BW 100%. The males and females were fed separately, with males receiving a breeder diet (A, above) with 14% protein. Feed allocations were restricted in order to maintain the body weight of the males at 100% of that recommended by the primary breeder. C. CP 14%, BW 90%. The males and females were fed separately, with males receiving a breeder diet with 14% protein (A, above). Feed allocations were restricted so as to maintain the body weight at 90% of that recommended by the primary breeder. D. CP 14%, BW 100%. The males and females were fed separately. The males received a diet containing 12% protein and 2,781 kcal/ kg of ME (Table 1). Feed allocations were restricted in order to maintain the body weight of the males at 100% of that recommended by the primary breeder. E. CP 12%, BW 90%. The males and females were fed separately. The males received a diet with 12% protein (D). Feed allocations were restricted in order to maintain the body weight of the males at 90% of that recommended by the primary breeder. In Treatments B through E the females were fed a 14%-protein diet, as described in Treatment A. In all treatments, the females were managed and fed according to the recommendations of the primary breeder. In Treatment A, three tube feeders were used in each pen; in Treatments B through E, four feeders were used in each pen. Grills with horizontal openings (4.13 cm) and vertical openings (7.62 cm) were placed over the pans of three of the feeders, denying the males access to the "female" feeders. Females were denied access to the single "male" feeder by elevating that feeder to a height of 46 cm. The pans on all
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access from 28 to 40 wk of age had no effect on fertility or on the hatchability of inseminated hens. In a subsequent study, the same researchers found that semen volume was highest when the breeder males were fed an amount equivalent to 85% of that given to controls provided with feed ad libitum (Brown and McCartney, 1983). Under natural mating schemes, where males and females eat from the same feeders, controlling male body weight is difficult; however, studies have indicated that fertility and the number of chicks per hen can be increased if the sexes are fed separately using a specially designed, two-feeder arrangement (McDaniel, 1986; Andrews et ai, 1988). The objective of the present experiment was to study the influence of feeding broilerbreeder males a diet containing either 12 or 14% protein while maintaining their body weights at either 90 or 100% of that recommended by the primary breeder. The effects of protein level and feed restriction were determined for fertility, hatch of fertile eggs, semen concentration, weight of the testes, body weight, breast angle, and pododermatitis.
FEEDING EFFECTS ON REPRODUCTION
TABLE 1. Composition and calculated nutrient content of broiler breeder diets Dietary protein (%) Ingredient
14
76.24 Ground yellow corn 9.5 Dehulled soybean meal (49% CP) Wheat middlings Dehydrated alfalfa meal (17.5% CP) Rice hulls Wheat bran Corn gluten meal 2.85 Menhaden fish meal 1.05 Limestone 7.15 Dicalcium phosphate 1.52 Iodized salt .35 1 Vitamin premix 1.02 Trace mineral mix 2 .051 DL-Methionine .032 .082 Choline chloride Lysine .15 Total 100 Calculated analysis ME, kcal/kg 2,922 Calcium, % 3.13 Phosphorus, % .60 Lysine, % .71 Methionine, % .33
12 70 7.5 8.0 5.5 3.5 2.0 1.0 1.9 .3 .25 .05
100
taken each 4 wk, beginning at 28 wk of age. Breast-angle measurements were determined by using the Virginia Breast Meter (Bywaters and Siegel, 1958). Foot conditions were scored numerically from 1 to 6, with 1 representing no foot pad sores and 6 representing severe pododermatitis (Weaver, 1971). Semen concentrations were determined by using the spermatocrit procedure described by Hickman (1958). At the conclusion of the experiment, all males were weighed and sacrificed; the gonads were removed to determine the weight of the testes as a percentage of body weight. Daily egg production was recorded for each pen. In addition, starting at 28 wk of age, the eggs were collected for 3 consecutive days at 4-wk intervals in order to monitor fertility. All eggs gathered during this period were identified by pen number and were placed in a cooler at 18 C and 75% relative humidity. After an average storage time of 5 days, the eggs were set in a commercial incubator. After 18 days of incubation, all eggs were candled so the apparent mfertiles and dead embryos could be identified. These eggs were removed, broken-out, and examined macroscopically so as to distinguish between early dead embryos and infertiles. The remaining eggs were transferred to a hatcher; after 3 additional days of incubation, the numbers were recorded for late deads, pipped shells, and viable chicks. Differences in treatments were determined by subjecting the data to an analysis of variance (Snedecor and Cochran, 1980). When significant differences were found (P<.05), Duncan's multiple range test (Duncan, 1955) and orthogonal contrasts were used to partition the differences. The mathematical model used for percentage fertility and percentage hatch of fertile eggs was: Yiik = ri + Tj + R
2,781 .89 .74 .51 .43
'Supplied per kilogram of diet: 5,513 IU of vitamin A; 2,205 IU of vitamin D 3 ; 2.2 IU of vitamin E; 3.5 mg of menadione sodium bisulfite; 4.4 mg of riboflavin; 11 mg of calcium D-pantothenate; 33 mg of niacin; 250 mg of choline chloride; 6.6 mg of vitamin B12; .55 mg of folic acid; 124.6 mg of DL-methionine; 125 mg of ethoxyquin; and .1 mg of selenium. ^race-mineral mix contained: 12.0% manganese, 12.0% zinc, 4.0% iron, .5% copper, .2% iodine, and .045% cobalt.
The mathematical model used for body and testes weights, semen concentrations, breastangle measurements, and foot scores was: Yykl = l-i + Tj + R a)i + B(ij)1 + P k + (TP)ik + e(iji)k where \i = overall mean; Tj = treatment effect; i = 1 , 2 , . . . , 5; R(j)i = pens within treatments; j = 1, 2; B(ij)j = males within pens and within treatments; 1 = 1,2, . . , 50; P k = periods; k = 1, 2 , . . . , 10; (TP)^ = the interaction of treatments
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feeders measured 41 cm in diameter, providing a feeding area 8.6 cm wide and 10.2 cm deep. The daily photoperiod was increased from 8 to 14 h when the birds were moved from the rearing pens to the production pens (20 wk of age). The photoperiod was further increased by 1 h at 22 and at 24 wk of age, remaining at 16 h until the end of the study. Light intensity ranged from an average of 11.5 lux during the early morning and evening hours to more than 1,000 lux during periods of sunshine. Incandescent bulbs were used as the source of artificial light in all pens. The males were weighed weekly, the females biweekly. Feed adjustments were made based on body weight. Male breast-angle measurements, foot scores, and semen concentrations were
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FONTANA ET AL. TABLE 2. Effect of dietary protein and feed restriction on the fecundity of broiler-breeder males Dietary treatments Control1
28 32 36 40 44 48 52 56 60 64 28 to 64
88.8 95.8 94.7 91.2 91.1 91.4 86.3 85.9 85.9 82.8 89.9
± 3.19a ± 1.69a ± 2.03a ± 2.71 ab ± 2.91 a ± 2.75a ± 3.48b ± 3.84b ± 4.34b ± 4.60a ± .97 b
CP 14%, BW 100%2 90.0 96.6 96.5 96.6 94.8 94.4 95.3 92.0 84.7 89.0 93.7
± ± ± ± ± ± ± ± ± ± ±
CP 14%, BW 90% 3
CP 12%, BW 100%4
CP 12%, BW 90% 5
Mean percentage fertility (± SEM) 2.94a 92.3 ± 2.17a 93.1 ± 2.35a 94.7 ± 1.94a 1.60a 94.5 ± 1.85a 1.43a 96.2 ± 1.53a 98.6 ± ,85a 88.4 ± 2.97b 1.60a 95.0 ± 2.19 ab a a 2.20 89.8 ± 2.93 95.6 ± 1.43a 2.04a 94.7 ± 2.26a 97.0 ± 1.58a 97.4 ± 1.47a 2.16a 98.7 ± .92a 3.12ab 93.7 ± 2.69 ab 96.8 ± 1.73a 4.56 b 97.2 ± 1.45a 92.0 ± 2.72 ab 96.4 ± 2.3 l a 4.54a 91.6 ± 3.25a .79" 94.6 ± .70a 94.7 ± .64a
86.7 94.7 95.2 95.2 90.3 95.6 95.3 95.8 92.9 91.9 93.3
± ± ± ± ± ± ± ± + ± ±
3.46a 2.17a 1.75a 2.08 ab 2.74a 2.08a 2.15a 2.25a 3.09ab 4.16a .81 a
a
' Means within a row with no common superscripts are significantly different (P<.05). 'Males and females fed together: breeder diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 4 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 5 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder.
and periods; and e(jji)k = error term. Correlations for the different variables were determined by the Pearson procedure within the Statistical Analysis System (SAS Institute, 1985). Percentage data were transformed to arcsine V% prior to analysis.
• CONTTOL
5700 -I
• 14-100" - 12-100" - 14-90"
5200-
* f
1
Weiqht
The males in the control pens had significantly (P<.05) heavier body weights from 32 to 65 wk of age than the males in the four treatment groups fed separately (Figure 1). Furthermore, the males in the control group had a consistently heavier body weight than that recommended by the primary breeder (Peterson, 1986). Compared with the males fed separately, the body weights of the control males ranged from 7% heavier at 32 wk to 23% heavier at 49 wk of age. The mean percentage for fertility over the entire production cycle was significantly lower for the broiler-breeders in the control pens compared with the treatment groups fed separately (Table 2). Fertility was 4.2% higher in the pens where both sexes ate from separate
>v
~y^\ ^ ^ ^ ^ M .
Male Bo
RESULTS
(g)
- 12-90"
J>
3700-
3200 24
28
32
36
40
44
48
52
56
60
65
Weeks of Age
FIGURE 1. Effect from two levels of dietary protein and of feed restriction on male body weight. Controls were fed a diet containing 14% protein and 2,922 kcal of ME/ kg. Treated groups were fed diets containing either 12 or 14% protein; the birds were restricted in order to maintain body weight at 90 or 100% of that recommended by the primary breeder. *Controls were significantly heavier than the four groups fed separately from 32 through 65 wk of age (P<.05). There were no differences among the four groups fed separately.
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Weeks of age
213
FEEDING EFFECTS ON REPRODUCTION
TABLE 3. Effect of dietary protein and feed restriction on the breast angle (degrees) for broiler-breeder males Dietary treatments Control1
28 32 36 40 44 48 52 56 60 64
85.3 89.3 92.3 94.1 88.1 90.1 88.5 92.7 86.8 87.7
1.4a 1.9a 1.8a 2.4a 1.8a 1.8a 1.7a 2.0a 1.9a 1.9a
CP 14%, BW 100%2 81.9 78.3 80.5 82.3 79.2 78.7 79.9 81.8 77.1 77.1
CP 14%, BW 90% 3
CP 12%, BW 100%4
Mean breast angle (degrees) (± SEM) 81.5 ± 1.7a 79.4 1.3a 80.2 ± 3.0a 78.7 1.7a 80.9 ± 3.2a 81.1 2.0a b b 80.9 ± 2.8 84.2 1.7 b b 79.5 ± 2.0 83.3 1.5 81.3 ± 2.2 bc 84.2 1.3C 83.0 ± 2.1 b 83.1 1.0b b b 83.8 ± 1.9 83.4 1.2 b b 80.4 ± 1.4 78.9 .81 80.5 ± 1.1" 77.2 1.21
1.8a 1.4" 1.8" 1.9b 1.6ab 1.5b 1.1* 2.1 b 1.3b 1.1"
CP 12%, BW 90% 5 79.0 80.7 80.6 84.6 80.0 83.2 80.6 80.7 78.2 76.1
1.2a 2.1 a 2.3* 1.9b 2.4b 2.3 bc 1.8b 2.6b 2.0 b 1.6b
a_c
Means within a row with no common superscripts are significantly different (P<.05). Males and females fed together: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. 2 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 3 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 4 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 5 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 1
feeders than in the control pens. There were no significant differences in the percentage fertility over the egg-production cycle in pens where males and females were fed separately, indicating equal effectiveness for the two levels of dietary protein (12 and 14%) and the two body-weight-restriction regimens (90 and 100%) imposed on the males. No significant differences were observed among the treatment groups for percentage hatch of fertile eggs during any of the 10, fourwk production periods (individual data not shown) or for the entire egg-production cycle. Weekly values ranged from a low of 69% at 64 wk of age to a high of 89% at 44 wk of age. Beginning at 40 wk of age and continuing for the remainder of the experiment, the breastangle measurements were significantly (P<.05) greater for males in the control pens than for males in the groups fed separately (Table 3). The increases in breast angles corresponded with those in body weights and were supported by a positive correlation coefficient of +.65 between these variables (Table 4). Conversely, between breast-angle measurements and fertility, a significant negative correlation coefficient of -.19 was calculated.
No differences were observed in the foot scores at any time among the treatments imposed under the present study. The foot scores ranged from 1.61 ±.18 ( x ± SE) at 28 wk of age, to 2.78 ± .44 (x ± SE) at 64 wk of age. However, significant (P<.01) correlations were measured between foot scores and age; also, between foot scores and body weight (Table 4). Those correlations indicated that the
TABLE 4. Correlation coefficients for BW, breast-angle measurement (BA), foot score (FS), weight of the testes (WT), percentage fertility (PF), and age of broiler-breeder males
Variables BW and PF BW and BA BW and FS BW and WT BW and age BA and PF BA and FS FS and age *PS.05. **P<.01.
Correlation coefficient .45** 65** 42** .44** ,42** 19* 18** .40**
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Weeks of age
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FONTANA ET AL. TABLE 5. Effect of dietary protein and feed restriction on the semen concentration and the weight of testes for broiler-breeder males Dietary treatments Control1
CP 14%, BW 100%2
28 32 36 40 44 48 52 56 60 64
5.80 ± .45 b 5.34 ± .57" 4.85 ± .74a 4.71 ± .44a 5.86 ± .74a 4.77 ± .50" 4.26 ± .37" 4.57 ± .41 a 4.44 ± .36a 6.71 ± .58a
7.13 5.43 5.86 5.61 7.41 5.03 5.00 5.95 4.97 7.23
Weight of the testes6
.903 ± .09a
CP 14%, BW 90% 3
CP 12%, BW 100%4
an number of spermatozoa (billion/mL) 7.27 ± .52 ab ± .55 ab 7.51 4.77 ± .31 a 6.71 ± .56a a a 5.45 ± .71 4.67 ± .43 5.12 ± .25 a 5.11 ± .33 a ± .51 a 6.09 ± .23 a 5.05 4.67 ± .55 a ± .54a 4.87 4.36 ± .50 a 6.01 ± .63 a a a ± .54 6.94 5.45 ± .50 5.55 ± ,33 a ± .40a 4.70 ± .52" 8.13 ± .48 a 5.32
.710 ± .15 aD
.452 ± .09"
(± SEM) — ± .la ± .94a ± .56a ± 1.2a ± 1.2* ± .65 a ± .71 a ± .92a ± .23 a ± .61 a
.459 ±
.09"
CP 12%, BW 90% 5 6.85 5.08 5.73 4.49 5.50 5.50 5.65 4.77 4.70 7.64
± ± ± ± ± ± ± ± ± ±
.69 ab .95 a ,60a .76a .48a .31 a .61 a .53 a .43 a .86a
.454 ± .10"
a,b
Means within a row with no common superscripts are significantly different (P<.05). 'Males and females fed together: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. 2 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. %lean weights for the testes, as a percentage of body weight, at 65 wk of age.
severity of the pododermatitis increased as the males became older and heavier. Other than at 28 wk of age, no significant differences in semen concentrations were observed (Table 5). At 65 wk of age, the weights of the testes as a percentage of body weight were significantly heavier for the control males (.90) than for the males fed separately (.52); there were no significant differences among males in the treatments receiving different levels of protein or being maintained at different body weights. The differences in the weights of the testes had little influence on semen concentration; the correlation coefficient between these two variables was not significant. DISCUSSION
Only recentiy have the available broilerbreeder management systems allowed for separate feeding of the sexes in a natural mating environment (McDaniel, 1986). Utilizing such a system, the results of the present
experiment showed that the fertility of broilerbreeders can be significantly improved when the males and females are fed separately. Andrews et al. (1988) obtained similar results in an earlier study. Under more-conventional systems, where both sexes are allowed to eat from the same feeders, the males invariably consume too much feed and become overweight, adversely affecting fertility. The relationship between body weight and fecundity is supported by the negative correlation coefficients observed in the present study between fertility and male body weight and between fertility and breast angle. These findings agree with those of Carte and Leighton (1969) who reported a negative correlation between breast width and mating efficiency in turkeys. Because of the intense genetic selection for breast size, turkey breeders have been forced to use artificial insemination exclusively as a means of producing progeny. A separate feeding system, as employed in the present study, might allow current selection programs to continue without having to resort to artificial insemination.
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Weeks of age
215
FEEDING EFFECTS ON REPRODUCTION
breeder males maintained in cages was actually improved when feed consumption was restricted and body weight was controlled, indicating that physical limitations are not the only reasons why fertility is diminished when males are overweight. Thus, the results reported by Burke and Mauldin (1985) and by Brown and McCartney (1983) imply that both physical and physiological factors may be involved in the relationship between body weight and fertility. In summary, the findings of the present study indicate that an improvement in fertility can be achieved by restricting feed consumption and, thereby, the body weight of broilerbreeder males. This can be accomplished by using separate feedings systems for the males and females. The reduction in fertility associated with excess male body weight appears to be both physical and physiological in nature. ACKNOWLEDGMENTS The present research was supported in part by the Virginia Poultry Industry Research Check-Off Program. The authors would also like to express their gratitude to Hubbard Farms, Inc. of Walpole, New Hampshire and to Peterson Farms of Decatur, Arkansas for providing the breeder chicks used in the study. REFERENCES Andrews, L. D., G. C. Hams, Jr., and L. Stamps, 1988. The performance of broiler breeders with a male feeding system. Poultry Sci. 67:48. (Abstr.) Arscott, G. M , and J. E. Parker, 1963. Dietary protein and fertility of male chickens. J. Nutr. 80:311-314. Bootwalla, S. M., V. J. Rakphongphairoj, and T. F. Savage, 1988. Semen quality of individually caged broiler breeder males fed 16 and 7% crude protein diets containing yellow peas. Nutr. Rep. Int. 38:1009-1015. Brown, H. B., and M G. McCartney, 1983. Effects of dietary restriction on reproductive performance of broiler breeder males. Poultry Sci. 62:1885-1888. Brown, H. B, and M. G. McCartney, 1986. Restricted feeding and reproductive performance of individually caged broiler breeder males. Poultry Sci. 65:850-855. Burke, W. H., and J. H. Mauldin, 1985. Reproductive characteristics of broiler breeder males from flocks with low fertility. Poultry Sci. 64:73. (Abstr.) Bywaters, J. H., and P. B. Siegel, 1958. A comparison of poultry breast measuring devices. Proc. Assoc. Southern Agric. Workers 55:209-210. Carte, I. F., and A. T. Leighton, Jr., 1969. Mating behavior and fertility in the large white turkey. Poultry Sci. 48: 104-114. Cecil, H. C , 1981. Effects ofdietaiy protein on body weight and reproductive performance on male turkeys. Poultry Sci. 60:1049-1055.
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The different dietary and body-weight restriction treatments imposed on broiler-breeder males did not have a great effect on pododermatitis. The correlation between fertility and pododermatitis was not significant. The progressive pododermatitis observed in all breeder males in the current study appeared to be more closely associated with aging and a subsequent increase in body weight than with different levels of dietary protein. Thus, even though the severity of pododermatitis increased with both age and body weight, foot condition had no effect on mating activity, as measured by fertility. The body weight and dietary protein levels for the males had a minimum influence on semen concentration, suggesting that the lower fertility observed among breeders in the control group was not caused by any inability of the males in that treatment group to produce an adequate number of sperm cells. These results are consistent with those of Vaughters et al. (1987) and of Wilson et al. (1987b). Those researchers found that feeding broilerbreeder males diets with 12 versus 14% protein and 12 versus 15% protein, respectively, had no effect on semen concentration. In the present experiment, the weights of the testes were more closely associated with body size than with the level of dietary protein. That outcome agrees with the findings of Wilson et al. (1987a), who reported no difference in the weights of the testes for breeder males fed protein levels ranging from 9 to 18%. Apparently, once the testes reach the minimum critical size, additional size increases have little effect on semen concentration. Brown and McCartney (1986) reported that testes' weights in excess of 7 g were required for sustained semen production by broilerbreeders. In the present study, males with testes weighing less than 9 g at the time of necropsy had been yielding semen only irregularly throughout the year. For broiler-breeder males, increased body weight has generally been associated with a reduction in reproductive performance. In contemporary broiler-breeder flocks exhibiting disparate fertility, Burke and Mauldin (1985) found that reduced fertility was related to excess male body weight; also, that mating activity diminished in the flock containing the overweight males. Semen volume was not affected. However, Brown and McCartney (1983) found that the fecundity of broiler-
216
FONTANA ET AL. growth. Pages 55-72 in: Poultry Genetics and Breeding. Longman Group, Harlow, England, U.K. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th ed. Iowa State University Press, Ames, IA. SAS Institute, 1985. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Vaughters, P. D., G. M. Pesti, and B. Howarth, Jr., 1987. Effects of feed composition and feeding schedule on growth and development of broiler breeder males. Poultry Sci. 66:134-146. Weaver, W. D., Jr., 1971. A biological and economic evaluation of two management systems for broiler breeders. Ph.D. Diss. Pennsylvania State University, University Park, PA. Wilson, H. R., L. O. Rowland, and R. H. Harms, 1971. Use of low protein grower diets to delay sexual maturity of broiler breeder males. Br. Poult. Sci. 12:157-163. Wilson, J. R., G. R. McDaniel, and C. D. Sutton, 1987a. Dietary protein levels for broiler breeder males. Poultry Sci. 66:237-242. Wilson, J. L., G. R. McDaniel, C. D. Sutton, and J. A. Renden, 1987b. Semen and carcass evaluation of broiler breeder males fed low protein diets. Poultry Sci. 66:1535-1540.
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Duncan, D. B., 1955. Multiple range and multiple F test. Biometrics 11:1-42. Hickman, C. G., 1958. Spermatocrit values in facilitating the estimation of spermatozoa concentrations. J. Dairy Sci. 41:318-319. Hubbard Farms, 1987. Hubbard Breeder Pullet Management Guide, 1987. Hubbard Farms, Walpole, NH 03608. McCartney, M. G., and H. B. Brown, 1980. Effects of feed restriction on reproductive performance of broiler breeder males. Poultry Sci. 59:2583-2585. McDaniel, G. R., 1986. Sex separate feeding of broiler parent stock. Zootech. Int. 11:54-58. Meyer, G. B., C. F. Props, A. T. Leighton, Jr., H. P. Van Krey, and L. M. Potter, 1980. Influence of dietary protein during the pre-breeder period on subsequent reproductive performance of large white turkeys. 2. Growth, feed consumption, and male sex-limited reproductive traits. Poultry Sci. 59:358-362. Parker, J. E., and B. J. McSpadden, 1943. Influence of feed restriction on fertility in male fowls. Poultry Sci. 22: 170-177. Peterson Farms, 1986. Peterson Breeder Management Guide, 1986. Peterson Farms, Decatur, AR 72722. Siegel, P. B., and E. A. Dunnington, 1985. Reproductive complications associated with selection for broiler
1990 Poultry Science 69:209-216 INTRODUCTION
Today's broiler-breeder is a product of intense genetic selection, nutritional advances, and systematic improvements in husbandry practices. The resulting progeny are characterized by rapid growth, excellent feed efficiency, and good body conformation. However, because of the negative genetic correlation between body size and reproduction (Siegel and Dunnington, 1985), the broiler industry has been forced to employ a number of management and nutritional schemes in order to maintain fecundity. Various levels of feed restriction, altered energy:protein ratios, or diets deficient in selected, essential amino acids have all been used to control growth. Arscott and Parker (1963) reported that feeding White Leghorn males a diet containing as little as 6.9% protein had no detrimental effect on semen volume or fertilizing capacity. Meyer et al. (1980) and Cecil (1981) observed that after turkeys attained sexual maturity, the volume and concentration of semen could be maintained satisfactorily with a diet containing 12% and 11% protein, respectively. When fed
to adolescent broiler-breeder males, diets containing 8.9% versus 16% protein significantly delayed sexual maturity but had no adverse effect on subsequent semen production, fertility, or hatchability (Wilson et al., 1971). Conversely, Wilson et al. (1987a) reported that broiler-breeder males fed a diet with 12 or 14% protein starting at 4 wk of age produced semen earlier and produced greater numbers of spermatozoa per ejaculate than did breeders fed a diet containing 16 or 18% protein. Individually caged broiler-breeder roosters fed a diet with 7% protein provided ad libitum or with a restricted feed intake on a diet with 16% protein produced semen of similar quality and fertilizing capacity (Bootwalla et al, 1988). Parker and McSpadden (1943) reported a progressive decrease in the volume, concentration, and fertilizing capacity of semen from Rhode Island Reds fed a diet restricted from 72 to 42% of that provided to controls fed on an ad libitum basis. However, McCartney and Brown (1980) found that restricting the diet of broiler-breeder males to 85 or 70% of the amount consumed by controls with ad libitum
209
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ABSTRACT A study was conducted using commercial broiler-breeder males and females maintained in alllitter pens and allowed to mate naturally. Using a separate feeding arrangement, males were given a diet containing either 12% or 14% protein. Body weights were maintained at either 90% or 100% of the recommended level. Females were provided feeders with grills which denied males access to the feed, while male feeders were elevated 46 cm above the floor to deny females access to that feed. In control pens, males and females ate from the same feeders and received a breeder diet with 14% protein. Eggs produced in pens where the males and females were fed separately showed significantly higher fertility (4.2%) than eggs from control pens. No differences in percentage fertility were noted between the two dietary-protein levels or body-weight groups of males fed separately. Furthermore, no differences were measured in percentage hatch of fertile eggs among any of the treatment groups. Males in control pens showed significantly heavier body weights and breast-angle measurements starting at 32 and 40 wk of age, respectively. No treatment effect was measured for male pododermatitis. The male control birds had heavier testes weights than the males in the groups with restricted body weights. However, semen concentration was not affected. This indicates that the improved fertility was related to the size and weight of the males, not to their ability to produce semen. The reduced fertility associated with excess male body weight may be both physical and physiological in nature. (Key words: broiler-breeders, fertility, body weight, separate feeding)
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FONTANA ET AL.
MATERIALS AND METHODS
Rearing Period (0 to 20 Weeks of Age) Day-old, broiler-breeder chicks (100 Peterson males and 600 Hubbard females) were used. They were divided into 2 and 14 brooding pens (1.52 by 3.66 m, respectively), which were totally enclosed. A diet containing 16% protein and 2,897 kcal/kg of ME was provided on an ad libitum basis for the first 2 wk and was then restricted by weight and fed every other day (skip-a-day) for the remainder of the rearing period. Half of the birds in each pen were weighed weekly in order to estimate BW; feed allotments were adjusted to maintain BW within the range recommended by the primary breeders (Peterson Farms, 1986; Hubbard Farms, 1987). Water was available ad libitum. Light was provided for 24 h at 20 lux for the first 3 days, then reduced to 8 h per day at that same intensity for the remainder of the rearing period. All birds were beak-trimmed at 10 days of age, following the recommendations of the primary breeders. Production Period (20 to 65 Weeks of Age) At 20 wk of age, 500 pullets and 50 cockerels were randomly selected and were equally
distributed among 10 breeder pens (2.44 by 4.88 m). All pens had a window (1.5 by 1.8 m) with a southern exposure. For the male breeders, the following dietary and feed-restriction treatments, which were replicated, were imposed in a factorial arrangement: A. Controls. The males and females were allowed to eat from the same feeders and were given a diet containing 14% protein and 2,922 kcal/kg of ME (Table 1). Feed allocations were based on maintaining the hens at the body weight and level of egg production recommended by the primary breeder. As a result, male feed consumption and, thus, body weight were only partially restricted. B. CP14%, BW 100%. The males and females were fed separately, with males receiving a breeder diet (A, above) with 14% protein. Feed allocations were restricted in order to maintain the body weight of the males at 100% of that recommended by the primary breeder. C. CP 14%, BW 90%. The males and females were fed separately, with males receiving a breeder diet with 14% protein (A, above). Feed allocations were restricted so as to maintain the body weight at 90% of that recommended by the primary breeder. D. CP 14%, BW 100%. The males and females were fed separately. The males received a diet containing 12% protein and 2,781 kcal/ kg of ME (Table 1). Feed allocations were restricted in order to maintain the body weight of the males at 100% of that recommended by the primary breeder. E. CP 12%, BW 90%. The males and females were fed separately. The males received a diet with 12% protein (D). Feed allocations were restricted in order to maintain the body weight of the males at 90% of that recommended by the primary breeder. In Treatments B through E the females were fed a 14%-protein diet, as described in Treatment A. In all treatments, the females were managed and fed according to the recommendations of the primary breeder. In Treatment A, three tube feeders were used in each pen; in Treatments B through E, four feeders were used in each pen. Grills with horizontal openings (4.13 cm) and vertical openings (7.62 cm) were placed over the pans of three of the feeders, denying the males access to the "female" feeders. Females were denied access to the single "male" feeder by elevating that feeder to a height of 46 cm. The pans on all
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access from 28 to 40 wk of age had no effect on fertility or on the hatchability of inseminated hens. In a subsequent study, the same researchers found that semen volume was highest when the breeder males were fed an amount equivalent to 85% of that given to controls provided with feed ad libitum (Brown and McCartney, 1983). Under natural mating schemes, where males and females eat from the same feeders, controlling male body weight is difficult; however, studies have indicated that fertility and the number of chicks per hen can be increased if the sexes are fed separately using a specially designed, two-feeder arrangement (McDaniel, 1986; Andrews et ai, 1988). The objective of the present experiment was to study the influence of feeding broilerbreeder males a diet containing either 12 or 14% protein while maintaining their body weights at either 90 or 100% of that recommended by the primary breeder. The effects of protein level and feed restriction were determined for fertility, hatch of fertile eggs, semen concentration, weight of the testes, body weight, breast angle, and pododermatitis.
FEEDING EFFECTS ON REPRODUCTION
TABLE 1. Composition and calculated nutrient content of broiler breeder diets Dietary protein (%) Ingredient
14
76.24 Ground yellow corn 9.5 Dehulled soybean meal (49% CP) Wheat middlings Dehydrated alfalfa meal (17.5% CP) Rice hulls Wheat bran Corn gluten meal 2.85 Menhaden fish meal 1.05 Limestone 7.15 Dicalcium phosphate 1.52 Iodized salt .35 1 Vitamin premix 1.02 Trace mineral mix 2 .051 DL-Methionine .032 .082 Choline chloride Lysine .15 Total 100 Calculated analysis ME, kcal/kg 2,922 Calcium, % 3.13 Phosphorus, % .60 Lysine, % .71 Methionine, % .33
12 70 7.5 8.0 5.5 3.5 2.0 1.0 1.9 .3 .25 .05
100
taken each 4 wk, beginning at 28 wk of age. Breast-angle measurements were determined by using the Virginia Breast Meter (Bywaters and Siegel, 1958). Foot conditions were scored numerically from 1 to 6, with 1 representing no foot pad sores and 6 representing severe pododermatitis (Weaver, 1971). Semen concentrations were determined by using the spermatocrit procedure described by Hickman (1958). At the conclusion of the experiment, all males were weighed and sacrificed; the gonads were removed to determine the weight of the testes as a percentage of body weight. Daily egg production was recorded for each pen. In addition, starting at 28 wk of age, the eggs were collected for 3 consecutive days at 4-wk intervals in order to monitor fertility. All eggs gathered during this period were identified by pen number and were placed in a cooler at 18 C and 75% relative humidity. After an average storage time of 5 days, the eggs were set in a commercial incubator. After 18 days of incubation, all eggs were candled so the apparent mfertiles and dead embryos could be identified. These eggs were removed, broken-out, and examined macroscopically so as to distinguish between early dead embryos and infertiles. The remaining eggs were transferred to a hatcher; after 3 additional days of incubation, the numbers were recorded for late deads, pipped shells, and viable chicks. Differences in treatments were determined by subjecting the data to an analysis of variance (Snedecor and Cochran, 1980). When significant differences were found (P<.05), Duncan's multiple range test (Duncan, 1955) and orthogonal contrasts were used to partition the differences. The mathematical model used for percentage fertility and percentage hatch of fertile eggs was: Yiik = ri + Tj + R
2,781 .89 .74 .51 .43
'Supplied per kilogram of diet: 5,513 IU of vitamin A; 2,205 IU of vitamin D 3 ; 2.2 IU of vitamin E; 3.5 mg of menadione sodium bisulfite; 4.4 mg of riboflavin; 11 mg of calcium D-pantothenate; 33 mg of niacin; 250 mg of choline chloride; 6.6 mg of vitamin B12; .55 mg of folic acid; 124.6 mg of DL-methionine; 125 mg of ethoxyquin; and .1 mg of selenium. ^race-mineral mix contained: 12.0% manganese, 12.0% zinc, 4.0% iron, .5% copper, .2% iodine, and .045% cobalt.
The mathematical model used for body and testes weights, semen concentrations, breastangle measurements, and foot scores was: Yykl = l-i + Tj + R a)i + B(ij)1 + P k + (TP)ik + e(iji)k where \i = overall mean; Tj = treatment effect; i = 1 , 2 , . . . , 5; R(j)i = pens within treatments; j = 1, 2; B(ij)j = males within pens and within treatments; 1 = 1,2, . . , 50; P k = periods; k = 1, 2 , . . . , 10; (TP)^ = the interaction of treatments
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feeders measured 41 cm in diameter, providing a feeding area 8.6 cm wide and 10.2 cm deep. The daily photoperiod was increased from 8 to 14 h when the birds were moved from the rearing pens to the production pens (20 wk of age). The photoperiod was further increased by 1 h at 22 and at 24 wk of age, remaining at 16 h until the end of the study. Light intensity ranged from an average of 11.5 lux during the early morning and evening hours to more than 1,000 lux during periods of sunshine. Incandescent bulbs were used as the source of artificial light in all pens. The males were weighed weekly, the females biweekly. Feed adjustments were made based on body weight. Male breast-angle measurements, foot scores, and semen concentrations were
211
212
FONTANA ET AL. TABLE 2. Effect of dietary protein and feed restriction on the fecundity of broiler-breeder males Dietary treatments Control1
28 32 36 40 44 48 52 56 60 64 28 to 64
88.8 95.8 94.7 91.2 91.1 91.4 86.3 85.9 85.9 82.8 89.9
± 3.19a ± 1.69a ± 2.03a ± 2.71 ab ± 2.91 a ± 2.75a ± 3.48b ± 3.84b ± 4.34b ± 4.60a ± .97 b
CP 14%, BW 100%2 90.0 96.6 96.5 96.6 94.8 94.4 95.3 92.0 84.7 89.0 93.7
± ± ± ± ± ± ± ± ± ± ±
CP 14%, BW 90% 3
CP 12%, BW 100%4
CP 12%, BW 90% 5
Mean percentage fertility (± SEM) 2.94a 92.3 ± 2.17a 93.1 ± 2.35a 94.7 ± 1.94a 1.60a 94.5 ± 1.85a 1.43a 96.2 ± 1.53a 98.6 ± ,85a 88.4 ± 2.97b 1.60a 95.0 ± 2.19 ab a a 2.20 89.8 ± 2.93 95.6 ± 1.43a 2.04a 94.7 ± 2.26a 97.0 ± 1.58a 97.4 ± 1.47a 2.16a 98.7 ± .92a 3.12ab 93.7 ± 2.69 ab 96.8 ± 1.73a 4.56 b 97.2 ± 1.45a 92.0 ± 2.72 ab 96.4 ± 2.3 l a 4.54a 91.6 ± 3.25a .79" 94.6 ± .70a 94.7 ± .64a
86.7 94.7 95.2 95.2 90.3 95.6 95.3 95.8 92.9 91.9 93.3
± ± ± ± ± ± ± ± + ± ±
3.46a 2.17a 1.75a 2.08 ab 2.74a 2.08a 2.15a 2.25a 3.09ab 4.16a .81 a
a
' Means within a row with no common superscripts are significantly different (P<.05). 'Males and females fed together: breeder diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 4 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 5 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder.
and periods; and e(jji)k = error term. Correlations for the different variables were determined by the Pearson procedure within the Statistical Analysis System (SAS Institute, 1985). Percentage data were transformed to arcsine V% prior to analysis.
• CONTTOL
5700 -I
• 14-100" - 12-100" - 14-90"
5200-
* f
1
Weiqht
The males in the control pens had significantly (P<.05) heavier body weights from 32 to 65 wk of age than the males in the four treatment groups fed separately (Figure 1). Furthermore, the males in the control group had a consistently heavier body weight than that recommended by the primary breeder (Peterson, 1986). Compared with the males fed separately, the body weights of the control males ranged from 7% heavier at 32 wk to 23% heavier at 49 wk of age. The mean percentage for fertility over the entire production cycle was significantly lower for the broiler-breeders in the control pens compared with the treatment groups fed separately (Table 2). Fertility was 4.2% higher in the pens where both sexes ate from separate
>v
~y^\ ^ ^ ^ ^ M .
Male Bo
RESULTS
(g)
- 12-90"
J>
3700-
3200 24
28
32
36
40
44
48
52
56
60
65
Weeks of Age
FIGURE 1. Effect from two levels of dietary protein and of feed restriction on male body weight. Controls were fed a diet containing 14% protein and 2,922 kcal of ME/ kg. Treated groups were fed diets containing either 12 or 14% protein; the birds were restricted in order to maintain body weight at 90 or 100% of that recommended by the primary breeder. *Controls were significantly heavier than the four groups fed separately from 32 through 65 wk of age (P<.05). There were no differences among the four groups fed separately.
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Weeks of age
213
FEEDING EFFECTS ON REPRODUCTION
TABLE 3. Effect of dietary protein and feed restriction on the breast angle (degrees) for broiler-breeder males Dietary treatments Control1
28 32 36 40 44 48 52 56 60 64
85.3 89.3 92.3 94.1 88.1 90.1 88.5 92.7 86.8 87.7
1.4a 1.9a 1.8a 2.4a 1.8a 1.8a 1.7a 2.0a 1.9a 1.9a
CP 14%, BW 100%2 81.9 78.3 80.5 82.3 79.2 78.7 79.9 81.8 77.1 77.1
CP 14%, BW 90% 3
CP 12%, BW 100%4
Mean breast angle (degrees) (± SEM) 81.5 ± 1.7a 79.4 1.3a 80.2 ± 3.0a 78.7 1.7a 80.9 ± 3.2a 81.1 2.0a b b 80.9 ± 2.8 84.2 1.7 b b 79.5 ± 2.0 83.3 1.5 81.3 ± 2.2 bc 84.2 1.3C 83.0 ± 2.1 b 83.1 1.0b b b 83.8 ± 1.9 83.4 1.2 b b 80.4 ± 1.4 78.9 .81 80.5 ± 1.1" 77.2 1.21
1.8a 1.4" 1.8" 1.9b 1.6ab 1.5b 1.1* 2.1 b 1.3b 1.1"
CP 12%, BW 90% 5 79.0 80.7 80.6 84.6 80.0 83.2 80.6 80.7 78.2 76.1
1.2a 2.1 a 2.3* 1.9b 2.4b 2.3 bc 1.8b 2.6b 2.0 b 1.6b
a_c
Means within a row with no common superscripts are significantly different (P<.05). Males and females fed together: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. 2 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 3 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 4 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. 5 Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. 1
feeders than in the control pens. There were no significant differences in the percentage fertility over the egg-production cycle in pens where males and females were fed separately, indicating equal effectiveness for the two levels of dietary protein (12 and 14%) and the two body-weight-restriction regimens (90 and 100%) imposed on the males. No significant differences were observed among the treatment groups for percentage hatch of fertile eggs during any of the 10, fourwk production periods (individual data not shown) or for the entire egg-production cycle. Weekly values ranged from a low of 69% at 64 wk of age to a high of 89% at 44 wk of age. Beginning at 40 wk of age and continuing for the remainder of the experiment, the breastangle measurements were significantly (P<.05) greater for males in the control pens than for males in the groups fed separately (Table 3). The increases in breast angles corresponded with those in body weights and were supported by a positive correlation coefficient of +.65 between these variables (Table 4). Conversely, between breast-angle measurements and fertility, a significant negative correlation coefficient of -.19 was calculated.
No differences were observed in the foot scores at any time among the treatments imposed under the present study. The foot scores ranged from 1.61 ±.18 ( x ± SE) at 28 wk of age, to 2.78 ± .44 (x ± SE) at 64 wk of age. However, significant (P<.01) correlations were measured between foot scores and age; also, between foot scores and body weight (Table 4). Those correlations indicated that the
TABLE 4. Correlation coefficients for BW, breast-angle measurement (BA), foot score (FS), weight of the testes (WT), percentage fertility (PF), and age of broiler-breeder males
Variables BW and PF BW and BA BW and FS BW and WT BW and age BA and PF BA and FS FS and age *PS.05. **P<.01.
Correlation coefficient .45** 65** 42** .44** ,42** 19* 18** .40**
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Weeks of age
214
FONTANA ET AL. TABLE 5. Effect of dietary protein and feed restriction on the semen concentration and the weight of testes for broiler-breeder males Dietary treatments Control1
CP 14%, BW 100%2
28 32 36 40 44 48 52 56 60 64
5.80 ± .45 b 5.34 ± .57" 4.85 ± .74a 4.71 ± .44a 5.86 ± .74a 4.77 ± .50" 4.26 ± .37" 4.57 ± .41 a 4.44 ± .36a 6.71 ± .58a
7.13 5.43 5.86 5.61 7.41 5.03 5.00 5.95 4.97 7.23
Weight of the testes6
.903 ± .09a
CP 14%, BW 90% 3
CP 12%, BW 100%4
an number of spermatozoa (billion/mL) 7.27 ± .52 ab ± .55 ab 7.51 4.77 ± .31 a 6.71 ± .56a a a 5.45 ± .71 4.67 ± .43 5.12 ± .25 a 5.11 ± .33 a ± .51 a 6.09 ± .23 a 5.05 4.67 ± .55 a ± .54a 4.87 4.36 ± .50 a 6.01 ± .63 a a a ± .54 6.94 5.45 ± .50 5.55 ± ,33 a ± .40a 4.70 ± .52" 8.13 ± .48 a 5.32
.710 ± .15 aD
.452 ± .09"
(± SEM) — ± .la ± .94a ± .56a ± 1.2a ± 1.2* ± .65 a ± .71 a ± .92a ± .23 a ± .61 a
.459 ±
.09"
CP 12%, BW 90% 5 6.85 5.08 5.73 4.49 5.50 5.50 5.65 4.77 4.70 7.64
± ± ± ± ± ± ± ± ± ±
.69 ab .95 a ,60a .76a .48a .31 a .61 a .53 a .43 a .86a
.454 ± .10"
a,b
Means within a row with no common superscripts are significantly different (P<.05). 'Males and females fed together: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights only partially restricted. 2 Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 14% protein; 2,922 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 100% of that recommended by the primary breeder. Males fed separately: diet, 12% protein; 2,781 kcal/kg of ME. Male body weights restricted to 90% of that recommended by the primary breeder. %lean weights for the testes, as a percentage of body weight, at 65 wk of age.
severity of the pododermatitis increased as the males became older and heavier. Other than at 28 wk of age, no significant differences in semen concentrations were observed (Table 5). At 65 wk of age, the weights of the testes as a percentage of body weight were significantly heavier for the control males (.90) than for the males fed separately (.52); there were no significant differences among males in the treatments receiving different levels of protein or being maintained at different body weights. The differences in the weights of the testes had little influence on semen concentration; the correlation coefficient between these two variables was not significant. DISCUSSION
Only recentiy have the available broilerbreeder management systems allowed for separate feeding of the sexes in a natural mating environment (McDaniel, 1986). Utilizing such a system, the results of the present
experiment showed that the fertility of broilerbreeders can be significantly improved when the males and females are fed separately. Andrews et al. (1988) obtained similar results in an earlier study. Under more-conventional systems, where both sexes are allowed to eat from the same feeders, the males invariably consume too much feed and become overweight, adversely affecting fertility. The relationship between body weight and fecundity is supported by the negative correlation coefficients observed in the present study between fertility and male body weight and between fertility and breast angle. These findings agree with those of Carte and Leighton (1969) who reported a negative correlation between breast width and mating efficiency in turkeys. Because of the intense genetic selection for breast size, turkey breeders have been forced to use artificial insemination exclusively as a means of producing progeny. A separate feeding system, as employed in the present study, might allow current selection programs to continue without having to resort to artificial insemination.
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Weeks of age
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FEEDING EFFECTS ON REPRODUCTION
breeder males maintained in cages was actually improved when feed consumption was restricted and body weight was controlled, indicating that physical limitations are not the only reasons why fertility is diminished when males are overweight. Thus, the results reported by Burke and Mauldin (1985) and by Brown and McCartney (1983) imply that both physical and physiological factors may be involved in the relationship between body weight and fertility. In summary, the findings of the present study indicate that an improvement in fertility can be achieved by restricting feed consumption and, thereby, the body weight of broilerbreeder males. This can be accomplished by using separate feedings systems for the males and females. The reduction in fertility associated with excess male body weight appears to be both physical and physiological in nature. ACKNOWLEDGMENTS The present research was supported in part by the Virginia Poultry Industry Research Check-Off Program. The authors would also like to express their gratitude to Hubbard Farms, Inc. of Walpole, New Hampshire and to Peterson Farms of Decatur, Arkansas for providing the breeder chicks used in the study. REFERENCES Andrews, L. D., G. C. Hams, Jr., and L. Stamps, 1988. The performance of broiler breeders with a male feeding system. Poultry Sci. 67:48. (Abstr.) Arscott, G. M , and J. E. Parker, 1963. Dietary protein and fertility of male chickens. J. Nutr. 80:311-314. Bootwalla, S. M., V. J. Rakphongphairoj, and T. F. Savage, 1988. Semen quality of individually caged broiler breeder males fed 16 and 7% crude protein diets containing yellow peas. Nutr. Rep. Int. 38:1009-1015. Brown, H. B., and M G. McCartney, 1983. Effects of dietary restriction on reproductive performance of broiler breeder males. Poultry Sci. 62:1885-1888. Brown, H. B, and M. G. McCartney, 1986. Restricted feeding and reproductive performance of individually caged broiler breeder males. Poultry Sci. 65:850-855. Burke, W. H., and J. H. Mauldin, 1985. Reproductive characteristics of broiler breeder males from flocks with low fertility. Poultry Sci. 64:73. (Abstr.) Bywaters, J. H., and P. B. Siegel, 1958. A comparison of poultry breast measuring devices. Proc. Assoc. Southern Agric. Workers 55:209-210. Carte, I. F., and A. T. Leighton, Jr., 1969. Mating behavior and fertility in the large white turkey. Poultry Sci. 48: 104-114. Cecil, H. C , 1981. Effects ofdietaiy protein on body weight and reproductive performance on male turkeys. Poultry Sci. 60:1049-1055.
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The different dietary and body-weight restriction treatments imposed on broiler-breeder males did not have a great effect on pododermatitis. The correlation between fertility and pododermatitis was not significant. The progressive pododermatitis observed in all breeder males in the current study appeared to be more closely associated with aging and a subsequent increase in body weight than with different levels of dietary protein. Thus, even though the severity of pododermatitis increased with both age and body weight, foot condition had no effect on mating activity, as measured by fertility. The body weight and dietary protein levels for the males had a minimum influence on semen concentration, suggesting that the lower fertility observed among breeders in the control group was not caused by any inability of the males in that treatment group to produce an adequate number of sperm cells. These results are consistent with those of Vaughters et al. (1987) and of Wilson et al. (1987b). Those researchers found that feeding broilerbreeder males diets with 12 versus 14% protein and 12 versus 15% protein, respectively, had no effect on semen concentration. In the present experiment, the weights of the testes were more closely associated with body size than with the level of dietary protein. That outcome agrees with the findings of Wilson et al. (1987a), who reported no difference in the weights of the testes for breeder males fed protein levels ranging from 9 to 18%. Apparently, once the testes reach the minimum critical size, additional size increases have little effect on semen concentration. Brown and McCartney (1986) reported that testes' weights in excess of 7 g were required for sustained semen production by broilerbreeders. In the present study, males with testes weighing less than 9 g at the time of necropsy had been yielding semen only irregularly throughout the year. For broiler-breeder males, increased body weight has generally been associated with a reduction in reproductive performance. In contemporary broiler-breeder flocks exhibiting disparate fertility, Burke and Mauldin (1985) found that reduced fertility was related to excess male body weight; also, that mating activity diminished in the flock containing the overweight males. Semen volume was not affected. However, Brown and McCartney (1983) found that the fecundity of broiler-
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FONTANA ET AL. growth. Pages 55-72 in: Poultry Genetics and Breeding. Longman Group, Harlow, England, U.K. Snedecor, G. W., and W. G. Cochran, 1980. Statistical Methods. 7th ed. Iowa State University Press, Ames, IA. SAS Institute, 1985. SAS User's Guide: Statistics. SAS Inst. Inc., Cary, NC. Vaughters, P. D., G. M. Pesti, and B. Howarth, Jr., 1987. Effects of feed composition and feeding schedule on growth and development of broiler breeder males. Poultry Sci. 66:134-146. Weaver, W. D., Jr., 1971. A biological and economic evaluation of two management systems for broiler breeders. Ph.D. Diss. Pennsylvania State University, University Park, PA. Wilson, H. R., L. O. Rowland, and R. H. Harms, 1971. Use of low protein grower diets to delay sexual maturity of broiler breeder males. Br. Poult. Sci. 12:157-163. Wilson, J. R., G. R. McDaniel, and C. D. Sutton, 1987a. Dietary protein levels for broiler breeder males. Poultry Sci. 66:237-242. Wilson, J. L., G. R. McDaniel, C. D. Sutton, and J. A. Renden, 1987b. Semen and carcass evaluation of broiler breeder males fed low protein diets. Poultry Sci. 66:1535-1540.
Downloaded from http://ps.oxfordjournals.org/ at Purdue University Libraries ADMN on June 5, 2015
Duncan, D. B., 1955. Multiple range and multiple F test. Biometrics 11:1-42. Hickman, C. G., 1958. Spermatocrit values in facilitating the estimation of spermatozoa concentrations. J. Dairy Sci. 41:318-319. Hubbard Farms, 1987. Hubbard Breeder Pullet Management Guide, 1987. Hubbard Farms, Walpole, NH 03608. McCartney, M. G., and H. B. Brown, 1980. Effects of feed restriction on reproductive performance of broiler breeder males. Poultry Sci. 59:2583-2585. McDaniel, G. R., 1986. Sex separate feeding of broiler parent stock. Zootech. Int. 11:54-58. Meyer, G. B., C. F. Props, A. T. Leighton, Jr., H. P. Van Krey, and L. M. Potter, 1980. Influence of dietary protein during the pre-breeder period on subsequent reproductive performance of large white turkeys. 2. Growth, feed consumption, and male sex-limited reproductive traits. Poultry Sci. 59:358-362. Parker, J. E., and B. J. McSpadden, 1943. Influence of feed restriction on fertility in male fowls. Poultry Sci. 22: 170-177. Peterson Farms, 1986. Peterson Breeder Management Guide, 1986. Peterson Farms, Decatur, AR 72722. Siegel, P. B., and E. A. Dunnington, 1985. Reproductive complications associated with selection for broiler