Effects of protein level and digestibility on the growth and carcass characteristics of broiler chickens1

Abstract

A study was conducted to evaluate the effects of dietary protein level and protein digestibility on the growth performance and carcass characteristics of broilers from 1 to 35 d of age. Broiler chickens (n = 320) were fed 4 different ideal protein-balanced, isocaloric diets in a 2 × 2 factorial design with 2 levels of protein [high protein (HiPro; 20 and 18% or 200 and 180 g/kg) and low protein (LoPro; 18 and 16% or 180 and 160 g/kg) on d 1 to 14 and d 15 to 35, respectively] and 2 levels of protein digestibility [high digestibility (HiDig) and low digestibility (LoDig); approximately 85% and 80% CP digestibility, respectively]. The HiDig diets were formulated using soybean meal and fishmeal, whereas the LoDig diets used wheat distillers dried grains with solubles and meat and bone meal as the primary protein sources. The standardized ileal digestibility (SID) values of the wheat distillers dried grains with solubles and meat and bone meal (56.5 and 72.0% SID for lysine, respectively) were measured before the experiment to improve the accuracy of the diet formulations. During the starter phase, the interaction was significant for ADG; birds fed the LoPro-LoDig diet grew slower than birds fed the other 3 diets (P< 0.05). During the grower phase, the interaction was significant for ADFI; birds fed the LoPro-LoDig diet had the lowest ADFI compared with those fed the other 3 diets. The interaction between protein level and digestibility was significant for the SID of most of the AA and was significantly higher for birds fed the HiPro-HiDig diet compared with those fed the other 3 diets. Total breast meat yield was significantly higher in birds fed the HiPro diets than in those fed the LoPro diets, whereas birds fed the HiDig diets had significantly more abdominal fat than those fed the LoDig diets. The results suggest that low-protein diets can support growth performance equal to high-protein diets when highly digestible ingredients are used. However, maximum breast meat yield requires a high-protein diet and is not affected by ingredient digestibility.

Effect of dietary protein concentrations, amino acids and conjugated linoleic acid supplementations on productive performance and lipid metabolism of broiler chicks

“…In our trial, in general, there are few differences among groups in terms of fat deposition and percentage of liver. The results on abdominal fat deposition are in line with the findings of Widyaratne & Drew (2011). Also the effect of liver fat percentage is not linear but the groups supplemented with 4% CLA had a higher liver fat percentage than the correspondent low-CP groups no supplemented with CLA, and, for the 5EAAs group, also higher than the control.…”

Productive, physiological and immunological responses of two broiler strains fed different dietary regimens and exposed to heat stress

“…According to Laudadio et al (2012) feeding dietary protein levels (20.5%) under thermoneutral conditions significantly improved the growth of broilers compared to levels of 22.5 and 18.5%, whereas BWG and feed intake and FCR remained unaffected by dietary treatment during 14-49 d of age. On the other hand, low-protein diets can sustain productive performance similar to highprotein diets (Widyaratne and Drew 2011). In this regard, ileum villi did not alter by feeding with the low-CP diet.…”

“…Moreover, the effect of the dietary CP of broilers was found to be inconsistent and differed from one study to another; for example, utilisation of low-CP diets for broiler chickens caused low performance compared to standard protein with sufficient amino acids (Berres et al 2010). On the other hand, Laudadio et al (2012) and Widyaratne and Drew (2011) found that low-protein diets under thermoneutral conditions did not influence the performance of broilers. Alternatively, in hot climates, low dietary protein increased growth performance (Thim et al 1997).…”

“…The use of low-CP diets for broiler chickens caused low performance compared to standard protein with sufficient amino acids (Berres et al 2010). On the other hand, Widyaratne and Drew (2011) and Laudadio et al (2012) found that lowprotein diets under thermoneutral conditions did not influence the performance of broilers. However, in hot climates, low-protein feed increases growth performance (Thim et al 1997) and decreases excreta N, thus eliminating environmental pollution from N (Sterling et al 2005;Kamran et al 2010;Attia and Hassan 2017).…”

Utilizing Salvinia molesta as Alternative Protein Source in Broiler Diet and the Effect on Performance, Breast Muscle and Abdominal Fat

“…Furthermore, the increase FI with diets T2 and T3 can be an attempt by the birds to meet their nutrient requirements (Hill and Dansky, 1954). According to Widyaratne and Drew (2011) FI is influenced by the availability and quality of dietary protein particularly lysine in the amino acid concentration, however, due to the high tannin content from the increase levels of S.molesta as well as crude fiber contents of diets T2 and T3 this could have reduced the amount of dietary lysine hence the birds increased their FI but still their nutrient requirements were not met as evident with the suppressed growth rate with treatments T2 and T3. This is in line with Uwalaka et al (2013) who observed that increased level of tannin content in unripe plantain peel meal (UPPM) caused the birds to increase their FI but still resulted in depressed weight gain of broilers.…”