Response of broilers to dietary balanced protein. 1. Feed intake and growth

Abstract

Context Knowing the broilers’ response to the intake of balanced protein allows nutritionists to choose the optimal level to be used in the feed. Aims The objective of the present study was to describe the response of male and female broilers of two commercial strains to a range of dietary balanced protein levels. Methods In total, 2496 sexed chicks (equal numbers of Ross 308 and Cobb 500) were used. Six dietary balanced protein levels × two strains × two sexes (24 treatments) were randomly allocated to 96-floor pens, using four replications of 26 chicks each. Feed intake, bodyweight, feed conversion efficiency, carcass weight and the weights of the breast without skin, thigh plus drum (leg) and wing were measured at 14, 28, 42 and 56 days of age. Key results Feed intake in all periods in both strains and sexes increased as the dietary balanced protein level decreased, and then decreased markedly at the lowest balanced protein levels. Only at 14 days did the responses differ between strains and sexes; in all other cases, the responses differed only between sexes. At 14 days, the response in bodyweight differed between strains and sexes, whereas at all other samplings they differed only between sexes. The response in carcass, breast and wing yield at 14 days was the same for both strains and sexes but differed between strains and sexes at 28 days. At 42 and 56 days, the response differed only between sexes. The response in leg (thigh-plus-drum) weight at 14 days was the same for both strains and sexes, but after that differed between sexes only. Body lipid content increased linearly initially, and then quadratically, as dietary protein content was reduced. Conclusions Appropriate equations are presented for describing the above responses of broiler chickens, male and female, from two commercial strains. Implications The fitted equations may be used to calculate the optimum economic level of dietary balanced protein to be used under different economic circumstances.

Dynamics of Growth and Egg Traits in Three Dietary Balanced Protein Scenarios Applied for Laying Hens

“…Specifically, the body composition of laying hens at the beginning of the laying phase could also affect the peak and persistence of egg production [ 29 ]. The dietary protein content is known to affect the growth of broilers and breeder pullets [ 30 , 31 ], and considering the higher cost of dietary protein [ 32 ] and the trend in reducing the nitrogen excretion in poultry farms [ 17 ], it might be convenient to investigate the effects of dietary protein over the growing and laying phase. Assuming that essential amino acids are required in constant ratios with lysine, in this study the concept of balanced protein was used as proposed by Eits et al [ 33 ].…”

“…A general theory for feed intake regulation was developed over the years [ 34 , 35 , 36 ], suggesting that feed intake is regulated by the first limiting component in the feed, being energy or essential amino acids. Evidence demonstrates that feed intake of growing broiler chicken and pullet of broiler breeder is affected by dietary protein [ 30 , 31 ]. For laying birds, the feed intake regulation seems to be more complex because the consumed nutrients are also used for egg production.…”

“…Among the responses observed in this study, the body fat content between laying hens consuming the different levels of balanced protein was unexpected. Most reports in the literature demonstrate that growing birds would increase body lipid content when they are offered a low balanced protein feed [ 30 , 31 ]. The opposite result is reported when a growing bird consumes a high balanced protein feed.…”

Response of Laying Hens to Repletion and Depletion in Dietary Balanced Protein

“…The objective to produce different laying hens at the end of the rearing phase was achieved, but the body composition was similar between groups. The effect of dietary balanced protein over body fat is well documented in the literature for broilers and breeders [ 27 , 28 ]. Those studies report that body fat percentage increases with the reduction in dietary balanced protein.…”

“…The data presented ( Table 5 ) demonstrate that repletion in dietary balanced protein could be a strategy to recover a pullet that reaches sexual maturity with low body weight. In addition, there may be an economic benefit to reduce balanced protein in the feed because the feed price would decrease [ 27 ]. Since feed intake was similar between groups, the feeding cost (feed intake x feed price) would also reduce.…”