Effects of growth patterns and dietary crude protein levels during rearing on body composition and performance in broiler breeder females during the rearing and laying period

Abstract

The combined effects of growth pattern (GP) and dietary CP level during rearing (2 to 22 wk of age) on body composition and performance were investigated in broiler breeder females from 0 to 40 wk of age. One-day-old pullets (n = 768) were randomly allotted to 48 pens according to 2 growth patterns (standard = SGP and high = HGP) and fed using 1 of 3 dietary CP levels (high = CPh, medium = CPm, and low = CPl). From 19 to 22 wk of age, feeding level was gradually adjusted to obtain a similar target BW for all birds, and then until 40 wk of age, all birds received similar amounts of a standard breeder diet. During the rearing period, the HGP pullets were fed a higher feed intake level (6.5%) than SGP pullets. To meet BW targets at 22 wk of age, feed intake from d 14 onward had to be increased for the CPm (4.6%) and CPl (10.0%) treatments. Breast muscle percentages of HGP and SGP pullets were similar at any age, although abdominal fat pad at 20 wk was 0.18% higher for HGP pullets. Pullets fed the CPl diet had a lower breast muscle percentage compared with pullets fed the CPm and CPh diets (0.46 and 0.85% at wk 10, 0.81 and 1.45% at wk 20, respectively). Abdominal fat pads in CPl pullets were 0.18 and 0.22% (wk 10), and 0.24 and 0.42% (wk 20) higher compared with CPm and CPh pullets, respectively. At 40 wk of age, no effects on breast muscle and abdominal fat pad were found among all treatments. Egg production, sexual maturation, and egg weight were not affected by GP and CP levels during rearing. It was concluded that a low CP diet during rearing decreased breast muscle and increased abdominal fat pad, whereas a high GP only increased abdominal fat pad, at the end of the rearing period. Decreasing dietary CP level seems to be more effective in increasing abdominal fat pad than increasing GP.

The effect of rearing photoperiod on broiler breeder reproductive performance depended on body weight

“…Independent of photoperiod, higher than recommended BW at the end of rearing accelerated sexual maturity (age at first egg), whereas a lower than recommended BW delayed sexual maturity (Fattori et al, 1991 ; Renema et al, 2001a , b ; Hocking, 2004 ; Ekmay et al, 2012 ). However, other studies did not find the same result (Zuidhof et al, 2007 ; van Emous et al, 2013 ). Target BW curves of the latter studies converged at peak production, whereas target BW curves in the former were not aligned during the laying period (van Emous et al, 2013 ).…”

“…However, other studies did not find the same result (Zuidhof et al, 2007 ; van Emous et al, 2013 ). Target BW curves of the latter studies converged at peak production, whereas target BW curves in the former were not aligned during the laying period (van Emous et al, 2013 ). Therefore, both target BW and the timing and level of feed restriction may affect sexual maturity and reproductive efficiency.…”

Low-protein diets with balanced amino acids reduce nitrogen excretion and foot pad dermatitis without affecting the growth performance and meat quality of free-range yellow broilers

“…Different feeding types, CP levels, breeds, and feeding environments may provide different results (Zhang et al 1999;Cui et al 2010). To our knowledge, CP research has primarily focussed on Arbor Acres broilers or laying hen (Emous et al 2013;Zeng et al 2015), and few studies investigated free-range yellow broilers in China.…”

Development of the ‘animal welfare’ dimension within the Greenwell sustainability assessment model. 1.: Justification of the selection of indicators

“…Moreover, the effects can be marginal [ The proportion of total time spent on stereotypic pecking after feeding is indicative of hunger in broiler breeders [69][70][71]. Relative feed control during the laying period is much lower than during rearing, especially after the peak of lay, and stereotypic behaviours are nearly absent, so this indicator relates mainly to the rearing period [72][73][74]. Male and female genetic line/breed in combination with nutritional/feeding management strategies (rearing)…”