Short-term effects of food protein content on subsequent diet selection by chickens and the consequences of alternate feeding of high- and low-protein foods

Performance, immunity, and physiological responses of broilers to dietary energy and protein sequential variations

The current trial was designed to examine effects of sequential feeding of diets varying in energy and protein contents on performance, gut development, welfare indices, and immune responses of broiler chicks. A total of 240 one-day-old broiler chicks (Ross 308) were randomly allotted to 4 treatments with 5 replicates in a completely randomized design. Sequential feeding was evaluated in 48-h cycles during 8 to 28 d of age. Diets varied in energy (E+ = 3,210 kcal/kg and E- = 2,790 kcal/kg) and protein (P+ = 25.14% CP and P- = 16.76% CP) contents. The 4 feeding programs were: control (ME: 3,000 kcal/kg, CP: 20.95%); P+/P- (P+ followed by P- containing 3,000 kcal/kg energy); E-/E+ (E- followed by E+ containing 20.95% CP), and E-P+ / E+P- (E-P+ followed by E+P-). The experiment lasted 42 d and birds were fed by a standard finishing diet from d 28 to 42. Broilers fed on E-/E+ and E-P+/E+P- had lower daily feed intake than control ones during 8 to 28 d of age (P < 0.05), while daily weight gain and feed conversion ratio were not affected significantly. Footpad dermatitis was lower in birds sequentially fed E-/E+ and E-P+/E+P- at 35 d of age (P < 0.05). Sequential feeding of diets varying in either energy or protein or both increased duration of tonic immobility at d 39 of age (P < 0.05). Feeding with E-/E+ regime decreased jejunal crypt depth, while feeding P+/P- regime increased villus height and crypt depth in the duodenum and ileum (P < 0.05). However, no relationship was found between intestinal morphology and growth performance of broiler chickens. Antibody production against sheep red blood cells as well as Newcastle and influenza disease viruses was not affected by sequential feeding. In conclusion, digestive organs and intestinal morphology might be adjusted to energy and protein variations. Sequential feeding increased the fear level in chickens.

Sequential Feeding Programs for Broiler Chickens: Twenty-Four- and Forty-Eight-Hour Cycles

Sequential feeding programs (Seq) of 2 feeds, 1 protein rich-energy poor and 1 energy rich-protein poor, during the same day or every other day were compared with a control complete diet for male broiler growth and body composition from 15 d to market weight. In experiment 1, BW gain and breast meat yield were significantly lower than those of controls for 24-h-cycle Seq with extreme protein content difference between the 2 feeds. BW gain and breast meat yield were higher than those of controls when feeds with moderate differences [feed moderately rich in protein (PM) = 26% CP; feed moderately rich in energy (EM) = 16% CP] were fed. Feeding periods that were half as long but changed twice as frequently gave less favorable results. In experiment 2, effects of allowing access to feed for different lengths of time were measured. The treatments in a 24-h cycle were a constant control diet, 50% PM-50% EM, 40% PM-60% EM, or 80% PM-20% EM decreasing to 40% PM-60% EM. Chickens fed 40% PM-60% EM had a 6% lower BW gain and a 3% higher feed/gain ratio and were fatter than those from other treatments. In experiment 3, male chickens fed a 48-h-cycle Seq of EM and PM every other day had the same BW gain, feed intake, and feed/gain ratio as controls. In experiment 4, five 48-h-cycle Seq with varying differences of energy and protein contents between EM and PM gave similar or slight reduction of performances compared with controls. A field trial with 8 flocks of broilers confirmed that feeding high and low protein feeds on alternate days resulted in performance similar to that from feeding a complete feed despite large day-to-day variations in lysine intake. Converse to shorter phases, Seq for 48-h cycles offers new opportunities for practical application and also for studies of short-term regulation of protein and lipid metabolism in chickens.

The relationship between meal composition and long-term diet choice

When animals are offered a choice of feeds that are nutritionally complementary, they are able to select a consistent combination of these feeds over long periods of time. Analysis of how such consistent diet choice is achieved, in terms of short-term feeding behavior, may further our knowledge of how animals regulate nutrient intake. Previous work, on meal pattern analysis and on nutrient synchronization, led us to hypothesize that animals may select a consistent diet within a meal. In three experiments cows were offered a choice between high- (H) and low- (L) protein feeds and short-term feeding behavior data were collected using computerized feeders. Feeding behavior was first analyzed in terms of visit characteristics. A greater average daily intake of H, relative to L, was more closely related to the ratio of H visits to L visits than to differences in the intake per visit to feeders supplying H or L. Individual meal criteria were estimated using a mixed-distribution model, and visits were clustered into meals. Cows typically had approximately six meals per day. The observed frequency distribution of meal composition, in terms of the proportion of visits to H feeders, was determined. Subsequently, the observed visits were randomly reclustered into bouts consisting of the same number of visits as were observed in meals, and the frequency distribution of random bout composition was calculated. If frequency distributions of meals and random bouts coincide, then this is evidence that cows do not regulate diet choice within a meal. Comparison of the frequency distributions of meals and random bouts provided no evidence that cows attempted to achieve their long-term average diet composition within a meal. We also investigated whether cows tried to achieve a consistent diet choice within a meal by adjusting their intake per visit, depending on the feed type visited and the proportion of visits to H feeders in a meal. There was no evidence that this occurred. In conclusion, our analyses have shown that cows did not attempt to select within a meal a consistent diet in terms of protein to energy ratio. Indeed, our data and the literature suggest that the timeframe over which the intake of energy and protein is regulated must be greater than a meal in a number of animal species.

Early age thermal conditioning and a dual feeding program for male broilers challenged by heat stress

The effects of early age thermal conditioning (TC) and dual feeding on responses of male broilers to a thermal challenge at 34 d of age are reported. Three hundred chicks were randomly divided into two equal groups. One group was exposed to thermal conditioning (38 C, 42% relative humidity for 24 h) at the age of 5 d, and the other group was not exposed. From 11 to 41 d of age, temperature was diurnally cyclic: 26 C (1600 to 0900 h) and 30 C (0900 to 1600 h). From Day 19, a factorial (2 x 2, TC x diet) experiment was conducted using eight pens of six broilers per treatment. Diets were control diet and dual feeding of a high protein fraction (1600 to 0900 h) and an energy-rich fraction (0900 to 1600 h). Growth and feed efficiency were slightly enhanced (+4%) by thermal conditioning and slightly reduced (-4%) by dual feeding. Mortality during thermal challenge was reduced by both factors. [In not conditioned chicks (N), 31 fed a control grower diet (NG) and 12 on a dual feeding program (NDF) died; in thermal conditioned chicks (T), 18 fed a control grower diet (TG) and 11 on a dual feeding program (TDF) died.] Before the thermal challenge period, body temperature (Tb) was consistently reduced in T. During the thermal challenge period, Tb was reduced by thermal conditioning and dual feeding. Measured at the age of 32 d, Tb gave an estimation of the ability of the chickens to cope with heat stress 2 d later. Pectoral mass was increased in TG, whereas the liver and the gizzard were significantly heavier in TDF and NDF. These results suggest that thermal conditioning at 5 d of age induces a consistent metabolic change in broiler males. The dual feeding program might have induced transitory effects on heat production during the heat stress.