Effect of Diet and Early Quantitative Feed Restriction on the Minimum Weight Requirement for Onset of Sexual Maturity in White Rock Broiler Breeders

Abstract

The effect of diet and feed restriction on minimum weight for onset of sexual maturity was studied in White Rock broiler breeders. In the restriction experiment, three groups of birds were subjected to moderate, severe, and very severe quantitative food restriction during the rearing period (19 week target weights: 1900, 1300, and 700 g, respectively). From 20 to 24 weeks body weight was equalized at 2200 g, and from 24 weeks birds were allowed to gain about 150 g/week until first egg. In the diet experiment, two groups of birds were raised under severe quantitative food restriction during the rearing period and then allowed to gain about 150 g/week on a low metabolizable energy/protein (ME/P) ratio diet (25.4% protein, ME/P = 116) and on a high ME/P ratio (14.7% protein, ME/P = 219) until first egg. All birds were killed at first egg. Birds of the three restriction groups entered lay at the same lean body weight and ash and protein content, but at different age, carcass weight, shank length, dry matter, and fat content. Birds of the two diet groups entered lay at the same lean body weight, shank length, and ash content but at different carcass weight, dry matter, and fat content. Considering both experiments together, birds of the different treatment groups entered lay at similar lean body weight and ash content but differed in age, carcass weight, shank length, dry matter, and fat content.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of age and carcase composition on the onset of sexual maturity in quail under normal feeding regimens

“…In addition, the ash content of the carcase was constant at 28, 35 and 42 d of age, despite the fact that calcium, the major component of ash according to Sturkie (1976), is of critical importance for egg production. These findings, which are similar to those of Soller et al (1984), indicate that ash content is not an important factor determining the onset of sexual maturity in the quail.…”

“…Quail which were not in lay had a lower fat content than those which had laid their first egg, suggesting that they were below the hypothesised minimum body fat threshold for the onset of egg-laying. Zelenka et al (1984) did not find any relationship between carcase fat and sexual maturity in Japanese quail, although Soller et al (1984) found that body fat content (percent fat) alone was not sufficient to initiate sexual maturity in meat-type breeders. However, it is evident from this experiment that the start of egg production is closely related to carcase fat content.…”

“…Sexual maturity is delayed until females reach a minimal chronological age. Other researchers (Leeson and Summers, 1982;Soller et al, 1984;Eitan and Soller, 1991) found that a minimum body weight is required for the initiation of sexual maturity in female domestic fowls, suggesting the possibility of there also being a minimum age requirement for maturity in this species. A significant correlation was found between egg-laying and liver weight.…”

“…This is a general phenomenon in mammals, as well as in poultry. Sexual maturity in female chicken and quail is unequivocally signalled by the onset of lay (Soller et al, 1984;Zelenka et al, 1984). Domestic fowl and quail must reach a minimum age before they can commence egg production (Dunnington and Siegel, 1984;Zelenka et al, 1984).…”

Retinoic Acid Accelerates the Development of Reproductive Organs and Egg Production in Japanese Quail (Coturnix coturnix japonica)1

“…As a consequence, the mean body weights at the first egg were not significantly different between the RA and VA treatment groups, even though the RA-treated quail began to produce eggs earlier ( Table 2). Results of several studies indicate that the onset of egg laying in chickens and quail, which is synonymous with the onset of sexual maturity, depends on several biological factors, such as body weight [20,21] and age [22,23]. The onset of sexual maturity (i.e., age at the first egg laying), as indicated by the development of reproductive organs [24], requires a minimum body weight.…”