The influence of daylength, body weight, and age on the reproductive ability of broiler breeder cockerels

Sexual behavior and seminal characteristics of fertile mature New Zealand White male rabbits of different body weights

Body weight in different mammalian species influences reproductive potential. The aim of the present study was to determine the relationship of body weight at the time of semen collection with libido, seminal characteristics and number of semen doses for artificial insemination (AI) in New Zealand White mature fertile male rabbits. Data came from 728 semen collections of 14 rabbits, 15-months of age that were sexually experienced with proven semen quality and fertility. Semen collection was performed twice a week with two ejaculates at each collection time and lasted 14 weeks. A second ejaculation was collected at 1-2h after the first. Data from each male from first and second ejaculates from 1 day of semen collection throughout the trial were averaged (n=324) and partial correlation coefficients and regression equations were estimated to describe the relationship of male body weight to ejaculation reaction time and 12 semen and sperm characteristics. As body weight increased there was a linear (P<0.05) increase in reaction time, abnormal sperm with an intact membrane and abnormal sperm with a damaged membrane and a linear (P<0.05) decrease in semen volume, sperm concentration per ejaculate, normal sperm with an intact membrane, number of normal motile sperm with an intact membrane and suitable semen doses for AI. Body weight of the mature male rabbit at semen collection had some influence on libido, semen and sperm characteristics, with a general trend toward a lesser reproduction potential as body weight increases.

Influence of male broiler breeder dietary energy intake on reproduction and progeny growth

A study was conducted to test the effects of dietary energy intake on reproduction in genetically similar broiler breeder males and on the subsequent growth of their progeny. Fifty-nine 1-d-old pedigree broiler breeder male chicks were raised to breeding age. At 33 wk of age, 33 males were chosen and placed in one of three groups of 11 males per group and fed either 370, 330, or 290 kcal per bird per d. Each group contained both full and half brothers and had similar 6- and 33-wk mean body weights. There was a significant negative effect of decreased dietary energy intake on sperm concentration and total live sperm per milliliter of ejaculate, whereas there was no significant effect on ejaculate volume or percentage dead sperm per ejaculate. Four groups of hens (21 wk of age) with 18 hens per group, were randomly assigned to each male dietary treatment group. Hens were artificially inseminated with 50 microL neat pooled semen from one of the three male treatment groups. There was a significant linear effect of diet on fertility, with no significant effect on hatch of fertile, hatch of eggs set, or embryonic mortality. There was no effect of sire energy intake on offspring body weights at 0, 3, or 6 wk of age. Hens were similarly artificially inseminated and sperm penetration determined for 9 consecutive d postinsemination. There was a significant quadratic relationship between sperm penetration of the perivitelline layer overlying the germinal disc and day postinsemination for each of the three male treatment groups. In addition, mean sperm penetration was 62.3, 42.9, and 6.6 holes in the germinal disc perivitelline layer for the high, medium, and low energy groups, respectively. Following 16 wk of dietary energy treatment, there was a significant linear effect of diet on mean testes weight, mean testes weight as a percentage of male body weight, and male body weight.

Effect of restricted and ad libitum feeding on semen production and fertility in broiler breeder males

1. The effect of food restriction on the quality of semen production and fertility in broiler breeder males was studied. 2. Seventy-two Ross broiler breeder males, from 20 to 54 weeks of age, were divided into 4 groups and fed as follows: group 1 = 110 g/bird/d; group 2 = 120 g/bird/d; group 3 = 130 g/bird/d; group 4 = ad libitum. 3. Body weight, sperm quality (volume, concentration, % motility and % live cells) and fertility were measured. The birds were slaughtered at 55 weeks of age; the abdominal fat pad and testicles were weighted. 4. Groups 2 and 3 produced the highest volume of semen. The quality of semen was very similar in all the restricted groups. 5. Males fed ad libitum produced semen with the best motility and percentage of live cells. Groups 3 and 4 showed the best fertility percentage (79%) against group 1 and 2 (59 and 72% respectively).

Performance of two male broiler breeder strains raised and maintained on various constant photoschedules

The purpose of the present study was to examine the interaction of constant photoschedules and genetic background on performance of male broiler breeders. Day-old cockerels from two BW strains were placed on litter floors in light-controlled chambers. Light treatments (LT) (60 lx) consisted of 2, 4, 8, 16, and 24 h light/day. At 9 wk of age, birds were individually caged and evaluated biweekly for semen production. Venous blood samples were collected at 16, 32, 48, and 64 wk of age. Data for testes weight, histology, and morphometry were obtained at 64 wk. Age at first semen production showed a cubic response in the levels of LT with earliest semen production from 4 and 8 h light (187.0 and 188.2 days, respectively). The BW was linear in the levels of LT within week; average BW was generally greater for birds on short LT than for birds on longer LT. Semen concentration was also linear in the levels of LT within week; increased semen concentration occurred with short LT. Changes in semen weight and spermatozoa count per ejaculate across the levels of LT differed for strain. A larger percentage of males produced semen in the less than or equal to 8 h LT than in the 16 or 24 h LT. Plasma testosterone was lower at 16 wk compared with later ages, and a positive linear relationship existed between testosterone level and hours of light. There was a cubic LT effect for testes weight per BW with larger values for less than or equal to 8 h LT compared with 16 or 24 h LT.

Effects of ad libitum and restricted feeding on semen quantity and quality, body composition, and blood chemistry of caged broiler breeder males

One hundred eighty, 16-wk-old, caged broiler breeder males were randomly assigned to one of three feeding treatments: 1) restricted feeding (RES), breeder-recommended levels minus 25%; 2) control feeding (CON), breeder-recommended levels; 3) full-fed (FF), ad libitum feeding. Each group received the same corn-soybean diet, with 15.5% CP and 2,878 kcal ME/kg feed. The males were ejaculated twice weekly, and BW, semen characteristics, hematocrits (HCT), and serum testosterone (T) were determined every 4 wk. At 17, 35, and 56 wk of age males were killed for body composition determination of percentages of protein, moisture, and fat. The FF males were heavier throughout the experiment than either CON or RES males. The FF group had a higher percentage of males in semen production than CON, which had a higher percentage of males in production than RES. Males of the FF group produced more semen with a higher spermatozoa concentration (SC) than CON, which males had higher spermatozoan concentrations than RES. The FF males had a higher level of T overall than CON or RES males. Hematocrits of FF were higher than those of CON birds, which were higher than those of RES birds. Body compositions were not significantly different among treatments at 17 wk; however, at 35 and 56 wk, FF males had a higher percentage of fat and a lower percentage of protein than birds in the other two groups. Significant positive correlations were found between body fat and the variables HCT, BW, semen weight (SW), and SC. Body weight was positively correlated with SW, and T was correlated with HCT.

Correlation of broiler breeder male semen production and testes morphology

Broiler breeder males were fed either a 9, 12, or 15% protein diet (2,819 kcal/kg metabolizable energy) from 6 to 50 wk of age. From 48 through 49 wk of age semen volume (VOL) and concentration (CONC) and number of spermatozoa per ejaculate (NSE) were determined, and at 50 wk of age body weight (BWT) and testes weight (TWT) were measured. Spermatogenic activity was evaluated histologically by a) a computer-aided assessment of seminiferous epithelial area (SEA), tubular diameter (TD), and epithelial height (EH); and b) visual appraisal of seminiferous tubular size and maturity of cell types (testes score-TS). Relationships among NSE, TS, SEA, TD, EH, BWT, and TWT were determined. Dietary protein had no significant effect on VOL, CONC, NSE, BWT, TWT, TS, SEA, EH, or TD. Significant positive correlation coefficients were observed among NSE, TS, SEA, TD, and EH, indicating moderate effectiveness of these methods in evaluating reproductive state. Low correlations between NSE and other variables may have resulted from 25% of the males having high TS but failing to ejaculate semen. Body weight and TWT, as well as BWT and NSE, were positively correlated. The SEA and TD had higher correlations with TWT than with BWT.

Restricted feeding and reproductive performance of individually caged broiler breeder males

Two experiments were conducted, one in the summer and another in the fall, involving 95 Hubbard broiler breeder males per experiment. Breeder males were randomly placed in individual cages at 26 (Trial 2) or 30 (Trial 1) weeks of age and provided with five levels of feed intake. The Hubbard White Mountain male Management Guide recommendation (154 g/bird/day) was designated as the control level (100%). Other levels were 115, 85, 70, and 55% of the control level. The effects of feed intake on body weight, semen volume, percent semen-packed cell volume, luteinizing hormone (LH), and testes weight were determined. Body weights were significantly decreased as feed intake was decreased. Dietary restriction levels of 115, 100, 85, and 70% had no significant effects on semen volume or semen-packed cell volume. Dietary restriction of 55% resulted in reduced semen volume, semen-packed cell volume (except in Trial 1), and testes weight. Dietary restriction had no significant effect on LH. A calculated metabolizable energy (ME) value of 346 kcal of ME/bird/day, which lies between the 85 and 70%-fed groups, should be adequate for normal body weight maintenance with the Hubbard broiler breeder male grown in individual cages.