The effects of broiler breeder BW and nutrient intake on ovary morphology and plasma reproductive hormone profiles were examined at photostimulation (PS) (21 wk) and at sexual maturity (SM) in standard (STD) and low (LOW), or high (HIGH) BW birds provided either restricted (RF) or ad libitum (AL) access to feed between PS and SM. At PS, 30 Shaver Starbro pullets at target BW were assigned to the STD treatment, and birds either 20% heavier (HIGH) or lighter (LOW) assigned accordingly. Ten birds of each size group were processed immediately for carcass analysis and 10 birds assigned to each size by feed interaction group. Blood samples were taken at 3-d intervals beginning at PS and profiles constructed for estradiol-17beta, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) to examine the relationship between body size, feeding level, and reproduction. Birds were processed for assessment of reproductive traits following SM. The AL birds reached SM with 11.0 large yellow follicles (LYF) (> 10 mm diameter) compared to 7.1 in RF birds. Small follicle atresia (< 5 mm diameter) was low in AL birds (10.3) compared to RF birds (32.3). The extent of small follicle atresia in RF birds was found to be inversely proportional to LYF number by stepwise regression. Increased small follicle atresia was associated with a longer sexual maturation period in RF birds (r = 0.619; P = 0.0003). Plasma estradiol-17beta concentration was greater in HIGH than in STD or LOW birds at PS, suggesting more advanced ovary development in HIGH birds. Estradiol-17beta profiles were similar in shape in all treatments, with the primary difference being the length of time prior to a substantial estradiol-17beta increase. Following PS, plasma LH and FSH concentrations of AL birds increased to levels nearly double that of RF birds, indicating a role for nutrient intake with rate of reproductive development. Plasma LH and FSH concentrations remained elevated for a greater time period in RF birds, however, possibly relating to the development of processes limiting LYF recruitment. This experiment demonstrated a modulation of reproductive hormone concentrations during sexual maturation by feeding level in conjunction with a sensitivity of the ovary to nutritional effects.

The effects of broiler breeder BW and nutrient intake on carcass traits were examined at photostimulation (PS) (21 wk) and at sexual maturity (SM) in birds of standard (STD) BW or either 20% lighter (LOW), or heavier (HIGH) at PS and subsequently allowed restricted (RF) or ad libitum (AL) access to feed. Of the 30 Shaver Starbro pullets assigned to each BW group at PS, 10 birds of each size were processed immediately for carcass analysis and 10 birds assigned to each of the RF and AL feeding regimens. Remaining birds were processed for assessment of carcass traits following SM. The mean BW of LOW, STD, and HIGH birds processed at PS were 1,639, 1,995, and 2,394 g, respectively. The relative breast muscle weight, abdominal fat pad weight, and total carcass lipid content of LOW birds were significantly lower than those of STD or HIGH birds. Body weight at PS primarily affected lipid stores, with absolute carcass lipid content being 103, 180, and 241 g in LOW, STD, and HIGH birds, respectively. The mean AL BW increased by 85% between PS and SM compared to 46% for RF birds. Although LOW birds weighed less than HIGH birds at SM, abdominal fat pad weight and carcass lipid content did not differ. Mean carcass lipid weight was 740 g in AL birds compared to 370 g in RF birds at SM. The use of AL feeding accelerated the onset of lay (25 d from PS) compared to RF birds (39 d), and removed body size effects on the rate of sexual maturation. Initial BW affected timing of SM in RF birds, with LOW, STD, and HIGH birds reaching SM 51, 38, and 27 d after PS, respectively. As the carcass composition of these birds varied greatly at PS, improving BW and composition uniformity at PS would be beneficial for a more uniform onset of lay and reduced early production losses from small hens. Whereas thresholds for BW, carcass protein, or carcass lipid appeared to affect the onset of lay in RF birds, the rapid onset of production in their AL counterparts suggests that the actual internal signal for reproductive development is more likely a metabolic one.

A study was conducted to determine the effect of nutrient dilution on plasma heterophil:lymphocyte ratios, behavior, and productivity of broiler breeder hens. Standard age-appropriate broiler breeder diets were fed either undiluted or diluted with 15 and 30% ground oat hulls from 0 to 56 wk of age. Feed was allocated daily so as to achieve the BW recommended by the breeder. Pullets were photostimulated at 20 wk, at which time 80 per treatment were moved, 2 per cage, to 120 laying cages, where they were housed until 56 wk of age. The same dilution treatment was continued for the laying period. The time required to consume the diluted feed was higher when diets were diluted during both the rearing (P = .002) and the laying periods (P = .0001). Heterophil:lymphocyte ratios at 12 wk of age indicated that hens subjected to higher levels of quantitative feed restriction experienced more long-term stress (P < .05). This difference was not evident at 20 wk or at 50 wk. During the laying period, hens that were fed diluted diets spent less time at the water source than those fed standard diets (P = .0001). The rate of decrease in flock uniformity during lay was slower in hens fed the diluted diets (P < .05). Hens fed the diet diluted by 15% had the highest egg production (P = .012), chick production (P < .0001), the best CP conversion efficiency (P < .05), and better feed conversion efficiency (P < .05). Diet dilution with ground oat hulls seems to be a means of reducing stress and improving efficiency and productivity in broiler breeder flocks.

The effect of age at photostimulation on carcass composition at photostimulation and at sexual maturity as well as its effect on subsequent reproductive performance in broiler breeders was investigated. A total of 600 broiler breeder pullets were reared in light-tight facilities. Skip-a-day feeding was used after 2 wk of age to limit body weight to levels suggested by the breeder. Limited daily feeding was initiated at the time of caging (time of photostimulation). The photoperiods used during rearing and lay were 8L:16D and 14L:10D, respectively. Forty birds were selected for study and moved to laying cages and photostimulated at 120, 130, 140, 150 or 160 d of age. Individual egg production records were kept until 60 wk of age. Twenty additional birds were killed for study of carcass composition and reproductive organ, morphology at the time of photostimulation and 20 others were killed at sexual maturity (first oviposition).As age at photostimulation increased, body weight and percent carcass lipid content increased while percent water and ash content decreased. No significant differences were found among treatment groups at photostimulation for carcass protein content. No significant differences were found in any carcass composition parameter at sexual maturity. All groups showed an increase in lipid content from photostimulation to sexual maturity, with the 120 d treatment group showing the largest increase. As age at photostimulation increased, the time from photostimulation to sexual maturity decreased. Total egg production, first egg weight, total egg mass produced, average fertility, hatchability and hatch of fertile did not differ significantly among treatment groups. Chick production was significantly higher in the 140-, 150- and 160-d treatment groups compared with the 120- and 130-d treatment groups. One explanation for the high rate of egg production seen in birds photostimulated at the older ages was that these birds reached sexual maturity with less between-bird variation. To take advantage of this improved flock uniformity, delaying photostimulation to 140 d of age or later is recommended. Key words: Chicken, broiler breeder, sexual maturity, egg production, hatchability, carcass composition

Changes in egg production, chick production, and egg laying patterns were examined in individually caged female Shaver Starbro breeders in a 2 × 2 factorial design based on two photostimulation programs and two feeding programs. The light period of Fast Photoperiod (FP) hens was changed from 8L:16D to 15L:9D at 20 wk of age. Slow Photoperiod (SP) hens were switched from a 8L:16D photoperiod at 20 wk to 11L:13D, with increases to 12L:12D, 13L:11D, 14L:10D, and 15L:9D weekly to 24 wk of age. Slow Feed (SF) hens were provided small (5 g or less) weekly increases in feed allocation from 20 to 25 wk. Fast Feed (FF) hens received larger feed allocations from 20 to 25 wk (maximum difference of 25 g more feed than SF hens received). Individual body weight, egg production, sequence length profiles, fertility, and hatchability were monitored to 64 wk of age.Whereas all treatments had a high rate of egg production, total egg production was 10.9 eggs greater in the SF feeding program (200.3) compared to the FF program (189.4). Hen-day production of SF birds was 68.2% for the laying period compared to 64.5% for FF birds over the 42 wk laying period. The mean laying sequence length of SF birds was 36.4% longer than for FF birds, indicating superior egg laying patterns and ability to maintain egg production. Sequence length was longer in FP than in SP hens in early lay (22 to 35 wk of age), although this effect appeared to be transient. Hatch of fertile and hatchability were increased in the SP compared to the FP birds, indicating an advantage to the SP program with regard to total number of chicks produced. Examination of embryonic mortality by 7-d periods of incubation indicated that the FF birds had a higher incidence of early and mid-term embryonic mortality than the SF birds, possibly relating to developmental problems associated with eggs of birds with excessive follicle development. These data demonstrate that minor differences in feed allocation can have an influence on egg and chick production traits and that precise early breeder hen management is paramount to optimize chick output. Exposing 20-wk old pullets to small, multiple feed increases can increase egg production. Key words: Broiler breeders, photostimulation program, feed restriction, egg production, fertility