A study was conducted to determine the performance, carcase and gastrointestinal tract (gut) characteristics of broilers fed diets supplemented with dry peppermint (<I>Mentha piperita</I> L.) or thyme (<I>Thymus vulgaris</I> L.) leaves, which are among the alternative growth promoters. In the study, 312 one-week-old broilers (Ross-308) were used. There were 3 dietary treatments, each consisting of 4 replications (13 males and 13 females in each replication). The control group was fed basal diet, while the peppermint and thyme groups were fed diets supplemented with 0.2% peppermint or thyme (w/w) as menthol and thymol (70 mg per kg diet) sources, respectively. From 7 days to 35 days of age, the body weight gain was higher (<I>P</I> < 0.05) in broilers fed the peppermint-supplemented diet compared to the control, but the effect of peppermint on body weight gain disappeared at 42 days of age. Feed intake, feed to gain ratio, carcase weight, carcase yield, and the relative weights of the edible inner organs and whole gut, and the relative length of the whole gut were not significantly affected by peppermint and thyme contents. The peppermint or thyme leaves increased (<I>P</I> < 0.05) the abdominal fat pad at 42 days of age. Thus, the dry peppermint leaves had a higher growth promoting efficacy than the dry thyme leaves at an early stage of broilers’ life, but an increase in abdominal fat should be taken into account for carcase quality and processing.

In this study, canonical correlation analysis (CCA) was applied to estimate the relationship between three different sexual maturity traits (X set: days to first egg (DFE), weight of the first egg (WFE), body weight at first egg (BWFE)) and level of nutrient intake (Y set: energy (EI) and protein intake (PI)) or the egg production traits at two different periods (Z set: number of egg (NE 1 and NE T ) and weight of egg (WE 1 and WE T ) from 22 to 25 (W first ) and 22 to 33 wk of age (W all ), respectively), which were measured from 64 egg-type pullets (Isa Brown) manipulated for time of access to energy and protein sources to onset of egg production. Partial CCA (PCCA) was used to eliminate the contribution of differences in the levels of nutrient intake to canonical variables for X and Z sets at the first production period. Estimated canonical correlation coefficients between X set and Y set (0.429, p = 0.042), X set and Z set (0.390, p = 0.007 for W first ) and within Z set (between W first and W all ; 0.780, p<0.001), and partial canonical correlation coefficient between X set and Z set (0.415, p = 0.009) were significant. Canonical weights and loadings from CCA indicated that the BWFE had the largest contribution compared to the DFE and WFE to variation of egg number produced at two different periods. The results from PCCA indicated that the contribution of PI and EI to the degree of the correlation between canonical variables for X and Z sets were unfavourable. In conclusion, the effect of body weight at sexual maturity upon the availability of nutrients can have a higher contribution to variation of egg production in pullets if the contribution of differences in nutrient intakes to onset of egg production were eliminated.

BACKGROUND: The effects of different methods of offering energy (ES) and protein (PS) sources on growth and egg production of layer pullets were assessed. From 9 to 22 weeks of age, 320 layer chickens (Isa Brown) were allocated to four treatments: 1, control (balanced diet); 2, E60:P40 (ES and PS in balanced diet sequentially during 60 and 40% of daily photoperiod respectively); 3, E40:P60 (ES and PS in balanced diet sequentially during 40 and 60% of daily photoperiod respectively); 4, EPFC (free choice between ES and PS in separate troughs).