The influence of feeding with starter diets containing spray-dried bovine colostrum (SBC), spray-dried bovine plasma (SBP), or spray-dried porcine plasma (SPP) on the growth performance and gut morphology of broiler chickens was investigated. The crude protein, lysine, and methionine plus cystine contents (g/kg as received) of SBC, SBP, and SPP were determined to be 766, 736, and 684; 58, 61, and 55; and 27, 28, and 24, respectively. The 3 test proteins were incorporated into a maize–soybean meal diet at a level of 50 g/kg and fed to 6 replicates of 8 male broiler chicks from 1 to 14 days of age. On Day 14, the experimental diets were replaced with a common grower-finisher diet, which was offered until Day 35. Dietary treatments had no effect (P > 0.05) on the weight gain or feed intake of birds during the first 14 days. However, feed/gain of birds fed the SBC diet was lower (P < 0.05) than of those fed the control diet. A trend for a reduction in feed/gain (P = 0.06) was observed in SBP and SPP diets. Dietary treatments had no effect (P > 0.05) on performance during Days 14–35 or Days 1–35. Villus height was increased by 5.7% (P < 0.05) and 4.6% (P = 0.05) in birds fed the SPP and SBP diets, respectively, compared with those fed the control diet. Crypt depth was 6% greater (P < 0.05) in birds fed the SPP diet and tended (P = 0.08) to be greater in birds fed the SBC diet, compared with birds fed the control. The ratio of villus height to crypt depth tended (P = 0.06) to be lower in birds offered the SBC diet compared with the control. Crypt goblet cell density was reduced (P < 0.05) by 13.9% in birds fed the SBC diet, compared with control birds. These results suggest that feeding with diets containing the SBC, SBP, and SPP during 1–14 days of age has some beneficial effects on broiler chickens. Further studies are needed to evaluate these products in less sanitary environments, which may increase the positive responses.
In the past, poultry nutrition has focussed on increasing the production efficiency to meet the progress achieved in the genetic potential of broilers and layers. Future directions in poultry nutrition will be driven by not only by the need to maximise biological and economic performance of birds, but also by societal issues (environment, antibiotic growth promoters, welfare, traceability and use of genetically modified ingredients). Key advances in poultry nutrition are discussed and future directions, which can be expected, are highlighted. Given the tightening supply and ever-increasing cost of raw materials, there will be more pressure to extract every unit of energy and nutrients from feed ingredients. In this context, a number of feed additives are expected to play an increasingly significant role. Feed enzymes and crystalline amino acids, in particular, will have a profound effect on future sustainability of the poultry industry. Future nutritional research need to focus on identifying the barriers to effective digestion and utilisation of nutrients and, to achieve this objective, nutritionists must combine their expertise with those of specialising in other biological sciences, including immunology, microbiology, histology and molecular biology.
The effects of dietary calcium (Ca) concentration on the digestion of Ca, phosphorus (P), nitrogen (N), fat and starch along the intestinal tract of broilers were assessed. Three-week old broilers were fed maize-soy diets containing 6, 9 or 12 g/kg of Ca (Ca: total P ratios of 1:1, 1.4:1 and 2:1, respectively) for six days and digesta were collected from the duodenum, jejunum, upper ileum and lower ileum. Apparent digestibility coefficients of P, Ca, N, fat and starch in different intestinal segments were calculated based on indigestible marker ratios in the diet and digesta. Apparent digestibility coefficients of P and Ca were determined to be negative in the duodenum. Apparent P digestibility was reduced (P<0.05) by increasing dietary Ca concentrations, but there was a Ca x intestinal site interaction (P<0.05). Jejunum was the major site of P absorption in birds fed the low Ca and normal Ca diets, but both the jejunum and upper ileum were involved in birds fed high Ca diets. Dietary Ca concentration had no effect (P>0.05) on apparent Ca digestibility. Calcium was absorbed predominantly in the jejunum. Digestibility of N and fat was reduced (P<0.05) by increasing dietary Ca concentrations. A significant (P<0.05) dietary Ca x intestinal site interaction was observed for N. In birds fed low Ca and normal Ca diets, N was primarily digested by the end of jejunum, but in birds fed high Ca diet both jejunum and upper ileum were involved. At all dietary Ca concentrations, fat was digested mainly in the jejunum and upper ileum, but digestion continued in the lower ileum. Apparent starch digestibility and AME were unaffected (P>0.05) by dietary Ca concentrations. Most of the starch digestion was completed by the end of the jejunum. The present data suggest that the site of digestion of P and N shifts depending on dietary Ca concentrations. Increasing dietary Ca concentrations negatively influenced the digestion of P, N and fat, but had no effect on those of Ca and starch.
A 21-d experiment was conducted with day-old male broilers (n = 840) to evaluate the effectiveness of supplemental phytase for improving the availability of phytate P in soybean meal when varying levels of P were fed. The semi-purified basal diet (.18% phytate P) contained soybean meal as the only protein source. Seven levels of phytase (0, 200, 400, 600, 800, 1,000, and 1,200 U/kg diet) were added to diets formulated to contain .20, .27, or .34% nonphytate P (nP; or .38, .45, and .52% total P, respectively). The desired levels of nP in the three basal P diets were achieved by adding varying amounts of defluorinated phosphate. A 2:1 Ca:total P ratio was maintained in all diets. Body weight gains and feed intake were improved (P < .001) by phytase at all nP levels, but the magnitude of response was greatest at low nP levels, resulting in an nP by phytase interaction (P < .01). Gain:feed was unaffected by phytase addition. A high mortality (35 to 45%) was observed for the .20 and .27% nP diets without added phytase, but this declined to normal levels with the addition of 200 to 400 U phytase/kg diet. Ash percentage of toes and tibia and shear force and stress of tibia increased with added phytase. These responses clearly show that the phytate-bound P in soybean meal was made more available to broilers by microbial phytase, and the total response was related to the phytase and nP/total P levels. Based on the high R2 values for the second order translog equations, BW gain, feed intake, and toe ash percentage were the most sensitive indicators to assess P availability, followed by tibia force and ash percentage. Derived nonlinear and linear equations for BW gain and toe ash percentage at the two lower nP levels were used to calculate P equivalency values of phytase for inorganic P. Using the average function of P released (Y) by microbial phytase (X) derived with nP levels of .20 and .27% for BW gain and toe ash percentage, Y = 1.120 − 1.102e−.0027X, 1 g of P could be released with 821 U of phytase. The amount of P released increased with increasing levels of phytase, but the amount of P released per 100 U of phytase decreased. Released P ranged from 31 to 58% of phytate P for 250 to 1,000 U of phytase/kg of diet.
An experiment was conducted to determine the digestible calcium (Ca) and digestible phosphorous (P) requirements of 10-day-old broiler chickens. Fifteen corn-soybean meal-based diets containing 3.3, 3.9, 4.4, 5.0, and 5.5 g/kg standardized ileal digestible (SID) Ca and 4.0, 5.0, and 6.0 g/kg SID P was fed to broilers from d 1 to 10. Each experimental diet was randomly allocated to 6 replicate cages (12 birds per cage). Body weight and feed intake were recorded at the start and end of the experiment and the feed conversion ratio was calculated. On d 10, birds were euthanized to collect ileal digesta, toes and tibia for the determination of digestible Ca and P, toe ash concentration and the concentrations of ash, Ca, and P in tibia. Titanium dioxide (5 g/kg) was included in all diets as an indigestible indicator for apparent ileal digestibility measurements. Total excreta were collected from d 1 to 10 for the measurement of total tract retention of Ca and P. Fixed effects of the experiment were dietary concentrations of SID Ca and SID P and their interaction. If the interaction or main effects were significant (P < 0.05), the parameter estimates for second-order response surface model were determined using General Linear Model procedure of SAS software. The growth performance, bone mineralization and mineral utilization of broiler starters were found to be optimized at 5 g/kg SID P concentration. Required SID Ca for maximum weight gain and bone mineralization was determined to be 3.32 and 4.36 to 4.78 g/kg, respectively, at 5 g/kg SID P concentration, which correspond to SID Ca to SID P ratios of 0.66 and 0.87 to 0.96, respectively. The estimated SID Ca requirement for weight gain is lower than the current Ca recommendation (9.6 g/kg total Ca or 4.4 g/kg SID Ca) for broiler starters. However, bone mineralization is maximized around the current total Ca recommendation at 8.9 to 9.8 g/kg (4.36-4.78 g/kg SID Ca) and indicates that bone mineralization requires more Ca than growth performance.