The effect of feed processing of novel unheated, low trypsin inhibitor soybeans on the performance of young female turkeys reared from hatch to 21 days of age.

The objective of this study was to evaluate the effects of dietary inclusion of a novel low trypsin inhibitor soybean (LTI) fed as mash or crumbled pellet form on the productive performance and digestibility in turkey poults from hatch to 21 d. A total of 336 Hybrid Converter turkey poults were allocated in groups of 7 to 6 treatments, each with 8 replicate cages. Treatments were arranged as a 3 × 2 factorial with inclusion level of the low trypsin-inhibitor soybean (0, 20, and 40% LTI) and feed form (mash and crumbled pellet). A single batch of feed was mixed for each inclusion level and divided into 2 aliquots: one remaining as mash and the other conditioned at 82°C for approximately 30 s, pelleted and then crumbled. On d 7, 14, and 21 posthatching, BW, and feed intake (FI) were recorded and BW gain (BWG) and feed conversion ratio (FCR) calculated. Excreta samples were collected from d 19 to 21 and pooled by cage. At d 21, intestines were excised, pancreas weights recorded (PRW), and ileal contents collected. There were no interactions (linear, P > 0.05) between LTI inclusion and feed form on BW, BWG, FI, or FCR at d 7 or 21. Increasing LTI resulted in a linear reduction in BW at 7, 14, and 21 d (P < 0.006). Poults fed crumbles were significantly heavier at d 21 than those fed mash feed (P < 0.027) with no interaction of LTI level with feed form. FCR was not significantly greater with increasing LTI. However, poults fed crumbles had a better, lower FCR that those fed mash feed from d 0 to 21 (P < 0.018). There was a significant interaction between feed form and LTI level at 14 d (P < 0.031), but not 7 or 21 d. Pancreatic hypertrophy (PRW) increased linearly with increasing LTI (P < 0.001) with a significant linear interaction with feed form (P < 0.001). Poults fed crumbles had less pancreatic hypertrophy. At 21 d of age, dietary fat digestibility (ALD, %) was linearly reduced with increasing LTI (P < 0.001). However, poults fed crumbles had significantly better fat absorption than poults fed mash (91.2 vs. 85.8%) (P < 0.001), and there was a significant linear interaction between feed form and LTI level (P < 0.001). AMEn was significantly better for the poults fed crumbles compared to mash (3228 vs. 3132 kcal/kg) (P < 0.001), and there was a significant linear interaction between feed form and LTI level (P < 0.001). Based on the results this trial, it is possible to include up to 20% unheated full fat LTI soybeans into poult starter diets after pelleting. Pelleting improves nutrient utilization, allowing for greater incorporation of the LTI soybean in the crumbled diet compared to the mash diet.

Response of turkey poults to soybean lectin levels typically encountered in commercial diets. 2. Effect on intestinal development and lymphoid organs.

Lectins are capable of altering intestinal morphology by binding to and disrupting the intestinal brush border membrane. They are also known to alter the weight of lymphoid organs. Therefore, we evaluated the effect of soybean lectin (SBL) on intestinal morphology and lymphoid organ weights of poults fed diets containing SBL. Dietary treatments evaluated in this study included a cornstarch and casein-based control (lectin-free) semipurified diet (PD) and semipurified diets containing 0.024 or 0.048% SBL (PDL and PDH, respectively). Experimental diets were fed from hatch to 14 d. Morphological evaluation of the intestine involved measurement of the villi height and perimeter, crypt depth, villus:crypt, and thickness of the muscle layer in the jejunum. Intestinal physical characteristics were also determined by measuring intestinal weight, length, and volume. Results indicated that 0.048% SBL in PDH increased villus:crypt and reduced total intestinal length in turkey poults. In addition, both the 0.024 and 0.048% dietary SBL levels reduced thymus weights. It was concluded that dietary SBL up to 0.048% enhanced intestinal development by increasing villus:crypt, but might alter the structural integrity of lymphoid organs.

Versazyme supplementation of broiler diets improves market growth performance.

Day-old male broiler chicks were randomly assigned to 32 floor pens in a completely randomized block design and grown to 6 wk of age. Birds in experiment 1 were fed 1 of 2 basal diets supplemented with or without a protease containing feed additive, Versazyme (VZ). The 4 treatments were 1) control (C), a corn-soybean meal diet that contained 95% of amino acids recommended by NRC except for threonine and isoleucine; 2) C + 0.1% VZ (wt/wt) (C+) in the starter diet only; 3) high (HP) amino acid diet, a corn-soybean meal diet with 100 to 105% of amino acid recommended by NRC except for threonine and isoleucine; and 4) HP + 0.1% VZ (wt/wt) (HP+) in starter diet only. Supplementing both diets with VZ improved BW and feed conversion ratio (FCR) at 21 d of age and BW at 42 d of age. Cumulative 42-d FCR was only improved in birds fed the HP+ diet. Birds in experiment 2 received the following treatments: 1) HP, 2) HP + 0.1% VZ batch A (wt/wt) (A) in starter diet only, and 3) HP + 0.1% VZ batch B (wt/wt) (B) in starter diet only. Enzyme supplementation improved 22-d BW and FCR. There was no significant difference in BW at 43 d of age. Both A and B improved overall FCR (1.758 and 1.751 vs. 1.79 for A and B vs. HP, respectively). In conclusion, supplementation of starter broiler diets with VZ resulted in improved market growth performance.

Response of turkey poults to soybean lectin levels typically encountered in commercial diets. 1. Effect on growth and nutrient digestibility.

Lectins are known to bind to the intestinal brush border membrane and induce antinutritional effects such as disruption of the brush border membrane (BBM) and reduced nutrient digestibility in laboratory rodents. Because soybean lectin (SBL) is usually present in poult starter diets, 2 similar experiments with starting turkey poults were conducted to investigate the effects of purified SBL on growth performance and nutrient digestibility. Experimental diets were a corn starch-casein based control (lectin-free) semipurified diet (PD), semipurified diets containing 0.024 or 0.048% soybean lectin (PDL, PDH), and a corn-soybean meal diet (SBD). Experimental diets were fed from hatch to 14 d. Antibodies specific for soybean lectin were detected in the serum of poults fed the PDL and PDH diets, implying that the SBL in these diets remained active in the digestive tract. Poults fed the control PD or SBD grew equally well. The 0.024% SBL level in PDL had no significant detrimental effect on any parameters assessed in the 2 experiments. In contrast, the 0.048% SBL level in the PDH gave inconsistent results for feed efficiency (FE) and brush border enzyme levels. For instance, on d 6 in experiment 2, poults fed the PDH had poorer FE (P < 0.05) compared with the control PD treatment, but had similar FE to poults fed the PD in experiment 1. In conclusion, SBL present at levels up to 0.024% of the diet would not cause antinutritional effect in turkey poults up to 2 wk of age.

Glucose and electrolyte supplementation of drinking water improve the immune responses of poults with inanition.

Enteric disorders predispose poultry to malnutrition. The objectives of this paper were 1) to simulate the inanition of poult enteritis mortality syndrome by restricting feed intake and 2) to develop a drinking water supplement that supports the immune functions of poults with inanition. Poults were restricted to 14 g of feed/d for 7 d beginning at 14 d of age then fed ad libitum until 36 d (recovery). The control was fed ad libitum. During the feed-restriction period, duplicate groups of 6 poults received 1 of 5 drinking water treatments: 1) restricted feed, unsupplemented water; 2) restricted feed + electrolytes (RE); 3) RE + glucose + citric acid (REGC); 4) REGC + betaine (REGCB); or 5) REGCB + zinc-methionine (REGCBZ). Immunological functions were assessed by inoculating poults with SRBC and B. abortus (BA) antigen at 15, 22, and 29 d of age. Antibody (Ab) titers were determined 7 d later for primary, secondary, and recovery responses. The primary and secondary total Ab titers to SRBC for restricted feed were 4.71 and 6.16 log3, which where lower (P < 0.05) than for controls (8.00 and 9.66 log3) and the other treatments. The recovery Ab titer for controls was 10.7, significantly higher than restricted feed (8.71) and RE (8.10) groups but not different from other treatments. The primary total Ab responses to BA were significantly lower in the restricted feed and RE groups as compared with the control and other treatments. Although feed restriction of poults to maintenance reduces the humoral immune responses, these responses can be significantly improved by drinking water containing electrolytes and especially sources of energy such as glucose and citric acid.

Investigating the possibility of monitoring lectin levels in commercial soybean meals intended for poultry feeding using steam-heated soybean meal as a model.

Native soybean lectins (SBL) could potentially have deleterious effects on young animals. The objectives of this study were to determine the optimum processing temperature and time at which SBL is inactivated and to investigate the possibility of using urease activity (UA) to predict residual lectin levels in soybean meal (SBM). Raw defatted SBM was steam-heated at incremental temperatures between 90 and 120 degrees C for 5 to 20 min in an autoclave. The processed meals were subjected to native-PAGE and measurement of total carbohydrate-binding lectin (TCBL), agglutinating lectin (AL), UA, and trypsin inhibitor (TI). Processing severity was evaluated by determining protein solubility in 0.2% potassium hydroxide. Results indicated that levels of all antinutrients (TCBL, AL, UA, and TI) decreased with increasing processing temperature (P < 0.05). The intensity of the lectin band on the electrophoresis gel was considerably reduced when meal was heated at 100 degrees C for 5 min. This result implied that lectin inactivation occurred at 100 degrees C. More than 90% of all the original antinutrient levels in the raw meal were destroyed when meals were heated at 100 degrees C for 5 min. Meals processed at 100 degrees C for 5 to 20 min had protein solubility values (80 to 85%) indicative of adequate processing. The denaturation pattern of UA was highly correlated with that of SBL (r > or = 0.73), indicating that UA could be used for monitoring lectin levels in commercial meals. We concluded that UA of 0.03 to 0.09 units of pH change are indicative of adequately processed meals that contain negligible lectin levels.

Keratinase in starter diets improves growth of broiler chicks.

The objective of this study was to determine the efficacy of a broad-spectrum protease enzyme, PWD-1 keratinase, upon supplementation to corn-soy starter diets on growth performance of broiler chickens. Three experiments were conducted. In each experiment, 1-d-old broiler chicks were randomly assigned to 24 cage pens of eight birds per pen in a completely randomized design of five experimental treatments and grown to 21 or 26 d of age. Treatments in experiments 1 and 2 were control (C, 21.39% CP), low protein (LP, 18% CP), and LP supplemented with 0.05, 0.1, or 0.15% enzyme preparation (wt/wt). Treatments in experiment 3 were control (C), C+ 0.1% enzyme preparation (C+E) fed starting at either 1 or 5 d of age, LP and LP+ 0.1% enzyme preparation (LP+E). Feeding the LP+E diet produced numerically higher BW at 21 d of age (experiments 1 and 3) and a significantly higher BW at 26 d of age (experiment 2; 1,025 and 1,032 g vs. 965 g for 0.1 and 0.15% vs. LP, respectively, P < 0.05). Feed conversion ratio (FCR) was also improved when chicks were fed the LP+E diet both at 21 (experiment 3) and 26 d of age (experiment 2). In experiment 3, supplementing the C diets with 0.10% enzyme resulted in improvements (P < 0.05) in BW whether the enzyme was supplemented starting at 1 d (767 vs. 695 g for C+E vs. C, respectively) or 5 d of age (764 vs. 695 g for C+E vs. C, respectively). FCR was numerically improved. Furthermore, diets supplemented with the enzyme at any level resulted in reduction of jejunal viscosity at 22 and 27 d of age (P < 0.05). Results of these experiments indicate that the growth of broiler chickens can be significantly improved by dietary supplementation with PWD-1 keratinase.

Intermittent biotelemetric monitoring of electrocardiograms and temperature in male broilers at risk for sudden death syndrome.

Biotelemetry was used to acquire electrocardiograms (ECG) and temperature measurements in a study of male broilers at risk for sudden death syndrome (SDS), a fatal condition that may have underlying cardiovascular mechanisms. Day-old (Day 1) Arbor Acres x Arbor Acres male chicks were randomly assigned to two different diets: control (Diet A) and one that contained elements that contribute to SDS (Diet B). The heaviest birds in each group on Day 13 underwent surgery on Day 15 to have transmitters with temperature sensors and ECG electrodes implanted. After surgery, three controls and three implanted birds from each diet group were kept in individual cages and exposed to 23 h of light and 1 h of darkness during each 24-h cycle. Implantation did not affect weight gain between Days 13 and 22 (P = 0.396). Temperature measurements and 1-min ECG were taken every 15 min. Heart rate and heart rate variability were measured from three 2-s segments in two dark and two light period samples during Days 17 to 19. Diet B decreased weight gain (P = 0.045), lowered heart rate (P < 0.0001), and increased internal temperature (P < 0.0001). Heart rate variability was lower during dark versus light periods (P = 0.004), which indicates that the birds rested during the dark periods, but was not affected by diet (P = 0.651). Thus, biotelemetry provided a useful method for intermittent physiological monitoring of poultry on different diets and under changing environmental conditions.

Growth and digestive function of turkeys surviving the poult enteritis and mortality syndrome.

Stunted growth of poults afflicted by enteritis mortality syndrome (PEMS) may be associated with depressed digestive capabilities. We conducted two experiments to test this hypothesis. Survivors of PEMS were obtained from a research flock that had been purposefully infected at 5 d of age with PEMS inoculum that included turkey corona virus. The PEMS survivors were assigned to Experiments 1 and 2, beginning at 40 and 35 d of age, respectively. Three groups (large, L; medium, M; and small, S) and two groups (L and S) of 20 poults each were selected to represent different degrees of stunting in Experiments 1 and 2, respectively. When the body weights of each group in both experiments were plotted using initial body weight as the starting point, all of the weights fell on the normal growth curve except Group S in Experiment 1. Therefore, there was no evidence of compensatory growth over the period studied. In Experiment 1, apparent fat absorption (AFA) was significantly higher (P < 0.05) for control (85.9%) than for M (78.5%) and S (78.3%) groups, and AME, for the control group was significantly higher than all the PEMS-survivor groups. In Experiment 2, Group L had a higher AFA and AMEn than Group S. AFA and AMEn improved in both groups over time. The digestive capabilities of PEMS survivors were depressed proportionally to the degree of stunting. Impaired fat digestibility and dietary energy utilization in PEMS-afflicted birds are likely contributors to stunted growth and reduced recovery rates.

Restriction of feed consumption and body weight in two strains of large white turkey breeder hens.

Large White female-line turkey breeder hen poults (576) of two strains (N, female line and B, male line) were brooded by strain in floor pens from day of hatch until 3 wk of age (WOA). At 3 WOA, all poults were randomly distributed by strain to 48 floor pens in a curtain-sided house. Poults were feed (calorie) restricted beginning at 3 (N3, B3) or 6 (N6, B6) WOA to obtain a 45% reduction in BW at 16 WOA compared to ad libitum controls (NC, BC). At 16 WOA, all hens were gradually returned to ad libitum feeding. At 18 to 30 WOA, all hens were subjected to 8 h light/d. At 30 WOA, all hens were photostimulated with 15.5 h/d. Hens were inseminated weekly with semen from same strain, male-line breeder males. Eggs were collected daily, and all settable eggs from weeks of lay (WOL) 5 to 6, 10 to 11, 15 to 16, 20 to 21, and 24 to 25 were incubated by pen in a common incubator for each set date. Measurements included BW, feed consumption, egg production, mortality, egg fertility, egg hatchability, and poult weight. Statistical analysis of means was performed by strain. Target BW were obtained for feed-restricted hens. Restricted hens increased their feed consumption upon re-alimentation but did not achieve the cumulative feed consumption or BW of control fed hens by 56 WOA. Egg production of N3 hens was greater than NC hens for WOL 2 and 3. Total and settable eggs per hen were greater for N3 hens than for NC for WOL 1 to 5. There were no differences observed for egg weight, egg fertility, hatch of all eggs set, hatch of fertile eggs, or offspring weight among N hen treatments. The B0 hens produced more eggs than B3 or B6 hens. The B6 hens produced lighter weight eggs than B0 hens. It was concluded that early severe feed restriction of female line breeder hens might improve subsequent reproductive performance.

Dietary threonine responses in growing turkey toms.

A study was conducted to evaluate Thr responses in Large White (British United Turkeys) male turkeys during three time periods: 0 to 3, 3 to 6, and 6 to 9 wk of age. The Thr-deficient diets, fed in 3-wk intervals, were composed primarily of corn, peanut meal, poultry meal, and soybean meal as intact protein sources and supplemented with amino acids. Graded levels of L-Thr were added to the Thr-deficient diets. Another group of turkeys received a corn-soybean-poultry meal control diet in each time period. Diets were formulated to meet a minimum of 110% of suggested amino acid specifications (NRC, 1994) for all essential amino acids, except Thr. Feed intake, BW gain, and feed:gain responses were measured. Average environmental temperatures for Weeks 1, 2, and 3 were 29, 27, and 24 C, respectively. From 4 to 9 wk of age, average environmental temperatures varied between 24 and 35 C. Turkeys in each time period responded to Thr in a curvilinear manner with responses at the asymptote being equivalent to turkeys fed the corn-soybean meal control diets. Adequate dietary Thr levels for gain and feed:gain for the 0 to 3 wk period were 0.93% (3.21 g Thr/Mcal ME) and 0.97% (3.34 g Thr/Mcal ME) of diet, respectively. From 3 to 6 wk of age, the level of dietary Thr needed to support adequate BW gain and feed:gain was 0.88% of diet (2.81 g Thr/Mcal ME). The level of dietary Thr needed to support adequate BW gain and feed:gain from 6 to 9 wk of age was 0.77% of diet (2.30 g Thr/Mcal ME). These results indicate that the NRC (1994) estimations of Thr needs up to 9 wk of age are more than adequate.

Vitamin D deficiency alters the immune responses of broiler chicks.

Three experiments were conducted to test the hypothesis that a vitamin D deficiency alters the immune responses of female broiler chicks. The control diet contained 800 IU of cholecalciferol (vitamin D3)/kg and the deficient diet was the same except without supplemental vitamin D3. The vitamin D deficiency status was established on the basis of a significantly lower blood ionized calcium or total serum calcium (75 to 85% of the control). Vitamin D-deficient chicks also had lower growth rate and bone ash. In Experiment 1 at 8 d of age, and Experiment 2 at 23 d of age, the cutaneous basophil hypersensitivity response as determined by the increase in interdigital skin thickness 20 h after a single injection of 100 microg phytohemagglutinin-P was significantly depressed in vitamin D-deficient chicks (62 to 64% of the control). Thymus weight, adjusted for body weight, was significantly lower in the vitamin D-deficient chicks at 24 d of age (61% of the control). Primary and secondary antibody responses against SRBC in vitamin D-deficient chicks were not different from the control. In Experiment 3, in 17-d-old chicks, vitamin D deficiency decreased the number of abdominal macrophages phagocytizing SRBC in vitro within 45 min from 14.7 to 10.1%. These results indicate that vitamin D deficiency depresses the cellular immune responses in young broiler chicks.

Dietary Spirulina platensis enhances humoral and cell-mediated immune functions in chickens.

Cornell K-strain White Leghorns and broiler chicks were raised to 7 wks and 3 wks of age respectively, with diets containing various levels (0, 10, 100, 1,000 and 10,000 ppm) of Spirulina platensis from day of hatch. Chicks in all treatment groups had comparable body weights. While bursal and splenic weights did not change, the K-strain chicks had larger thymuses (P < or = .05) over the controls (0 ppm group). No differences were observed in anti-sheep red blood cells antibodies during primary response. However, during secondary response, K-strain chicks in all Spirulina-dietary groups had higher total anti-SRBC titers with 10,000 ppm group being the highest (6.8 Log2) versus the 0 ppm (5.5 Log2) group. In broiler chicks, a one Log increase in IgG (P < or = .05) was observed in 10,000 ppm group over the controls. Similarly, chicks in 10,000 ppm Spirulina group had a higher PHA-P-mediated lymphoproliferative response over the 0 ppm controls. Macrophages isolated from both K-strain (10,000 ppm group) and broilers from all Spirulina groups had higher phagocytic potential than the 0 ppm groups. Spirulina supplementation at 10,000 ppm level also increased NK-cell activity by two fold over the controls. These studies show that Spirulina supplementation increases several immunological functions implying that a dietary inclusion of Spirulina at a level of 10,000 ppm may enhance disease resistance potential in chickens.

Dietary calcium and phosphorus effects on broiler performance and the incidence of sudden death syndrome mortality.

Three experiments were conducted with broiler chickens to determine the effect of dietary Ca and P on growth, feed conversion, bone ash, and the incidence of sudden death syndrome (SDS) mortality. Trial 1 tested three rations [100% NRC (1984) Ca and P; 140% NRC Ca and P; and 140% NRC Ca and P to 3 wk and 100% NRC from 4 to 7 wk] in Ross x Ross males to 7 wk of age. Dietary Ca and P had no effect on body weight, feed conversion, bone ash, or leg problems, but SDS mortality was significantly higher in the two groups fed 140% Ca and P for 3 or 7 wk (2.83 and 3.33% SDS mortality, respectively). Trial 2 tested three diets (85% NRC Ca and P, 100% NRC Ca and P, and 140% NRC Ca and P) in mixed sex Arbor Acres x Peterson chicks to 7 wk of age. The lower level of Ca and P (85% NRC) significantly improved feed conversion (7 wk) and decreased bone ash only at 3 wk and serum Ca (7 wk). There was no effect of diet on SDS in this trial. Trial 3 tested two diets (85% NRC Ca and P or 100% NRC Ca and 85% NRC P) in Ross x Ross males to 9 wk of age. Six-week body weight was significantly reduced in the 85% NRC Ca and P diet but body weight was equal by 9 wk of age. No effects were observed for feed conversion, leg disorders, bone ash, or serum Ca. The SDS mortality was significantly increased in the chicks fed the 100% NRC Ca and 85% P diet compared to the 85% NRC Ca treatment. The results of these trials indicate that even slight deviations in dietary Ca and P beyond the NRC recommendations can create a metabolic imbalance in certain strains of broilers (Ross x Ross), which possibly increases susceptibility to SDS mortality.

Fusarium proliferatum culture material alters several production and immune performance parameters in White Leghorn chickens.

White Leghorn Cornell K-strain chicks (3 replicates of 16 per pen) were started at Day 7 on feed amended with Fusarium proliferatum culture material containing fumonisin B1, fumonisin B2, and moniliformin at 61, 10.5, and 42.7 ppm, respectively. Observed effects on performance of treated birds included reduced feed conversion at 2 wk, and reduced body weight of males and females up to 6 wk (P < or = .05). Splenic, thymic, and liver weights, normalized for body weight, were reduced (P < or = .05) with no change in bursa of Fabricius. No significant changes were observed histologically in the spleen, bursa, kidney, heart, liver, cecal tonsils, colon, or tibia. Significant suppression in total Ig and IgG levels occurred. Macrophages from treated chicks exhibited a 34% reduction in phagocytic activity. Natural killer cell activity was not affected. These findings, which showed that Fusarium toxins alter performance and immune end points in chickens, imply that chickens exposed to mycotoxins may be more susceptible to infectious diseases.

Tolerance of turkeys to diets high in trypsin inhibitor activity from undertoasted soybean meals.

The objectives were to determine the responses of turkeys to soybean meals (SBM) differing in urease and trypsin inhibitor activity, to estimate the AME of diets containing these SBM, and to determine the responses to supplemental L-Met and L-Lys. Four experiments were conducted with poults 1 to 3 wk of age and one with turkeys 6 to 8 wk of age. In Experiment 1, the trypsin inhibitor activities (TI) were 1.8, 4.2, 5.4, 7.0, and 8.8 mg trypsin inhibited/g SBM (method of Hamerstrand et al., 1981). The corresponding urease indices were .02, .14, .51, .90, and 1.5 pH units. The SBM were 46% of the diet. Significant pancreatic hypertrophy occurred with dietary concentrations of TI of 3.2 mg/g and above. At 4.0 mg TI/g of diet, the feed:gain ratio was increased, but body weight gain and AME of the diet were reduced. In Experiments 2, 3, and 4, poults responded similarly to Met additions to diets containing 46% SBM with TI of 1.8 or 4 mg/g SBM, or to Met or Met plus Lys additions to diets containing 40.7 or 49.6% SBM with TI of 2 or 11 mg/g SBM. In Experiment 5, the SBM contained TI at 4.3, 6.1, 8.9, or 12.5 mg/g. The corresponding urease indices were .05, .27, 1.43, and 1.72 pH units. The SBM were 49.6% of the diet. Using 6 to 8 wk old turkeys, the AME of the four diets were determined to be 2.76, 2.71, 2.58, and 2.57 Mcal/kg. The AME of diets containing 4.4 and 6.2 mg TI/g of diet were reduced (P < .05). In conclusion, through 3 wk of age, turkeys can tolerate soybean TI concentrations of 2.5 mg TI/g of diet. Turkeys 6 to 8 wk of age can tolerate 3 mg of soybean TI/g of diet.

Potassium chloride improves the thermotolerance of chickens exposed to acute heat stress.

Experiments were designed to test the hypothesis that chicks that drank an electrolyte solution containing K prior to and during an acute exposure to heat would have greater thermotolerance than chicks that consumed only water. In three experiments, 5- or 7-wk-old male chickens drank distilled water (control), or .3, .6, or .9% KCl solutions (Experiments 1 and 2), and .6 or .9% KCl or .8% KHCO3 solutions (Experiment 3) for 48 h before acute heat stress (HS) and during HS. Body temperature (Tb), blood pH, partial pressure of blood carbon dioxide (pCO2), ionized Ca (Ca2+), plasma Na, K, Cl, total Ca, inorganic P (Pi), and osmolality (Osm), and water consumption were determined. Water intake increased with the concentration of KCl. Before HS, .6% KCl increased plasma K and Ca2+, whereas .9% KCl resulted in a marked increase in K, Ca2+, Na, Cl, and Osm and a decrease in pH. During HS, .6% KCl-birds had lower hyperthermic Tb and pH values and higher Ca2+ and K concentrations than controls. Plasma Na and Osm of .6% KCl birds decreased whereas those of the control birds remained unchanged. Providing K as KHCO3 aggravated respiratory alkalosis and failed to influence either Tb or plasma electrolytes, suggesting that the beneficial effect of .6% KCl may in part be attributed to the accompanying Cl. Hyperthermic Tb and Ca2+ values were highly correlated. The results showed that .6% KCl solution reduced HS-related responses and indicated a relationship among supplemental KCl, blood Ca2+, and Tb.

Duodenal calcium uptake, femur ash, and eggshell quality decline with age and increase following molt.

An experiment was conducted to test the hypothesis that the decline in eggshell quality over time during egg production, and its improvement after molting, paralleled the rate of calcium uptake by the duodenum of the laying hen. In vitro duodenal calcium uptake rate and femur ash (percentage of femur weight) were determined at 37, 45, 51, 58, 68, and 72 wk of age. Percentage shell and shell thickness (millimeters) were determined at 22, 29, 36, 44, 50, 57, and 71 wk of age. Molt was induced at 63 wk of age. Three commercial strains DeKalb XL-Link, ISA/Babcock B-300V, and Hy-Line W-36 were compared. There were no differences in duodenal calcium uptake rate among strains. There was a significant decline (P < .01) in duodenal calcium uptake from 408 pmol/mg tissue per min at 37 wk of age to 329 pmol/mg per min at 58 wk of age. Femur ash decreased (P < .01) from 50.8% at 37 wk of age to 47.6% at 58 wk of age. Percentage shell and shell thickness declined (P < .01) from 9.79% and .403 mm at 22 wk of age to 8.88% and .373 mm at 57 wk of age, respectively. After the induced molt, duodenal calcium uptake increased (P < .01) to 402 pmol/mg tissue per min, and percentage shell and shell thickness increased (P < .01) to 10.23% and .389 mm, respectively. Duodenal calcium uptake increased immediately postmolt, whereas femur ash did not increase until 72 wk of age (P < .01).

Dietary electrolyte balance effects on performance and metabolic characteristics in growing steers.

The effects of dietary electrolyte balance (DEB; mEq of Na + K - Cl/100 g of DM) on performance and acid-base status of growing cattle consuming a corn silage-based diet were established using 120 Angus (n = 60) and Angus crossbred (n = 60) steers (247 +/- 2.4 kg). Treatments consisting of 0, 15, 30, or 45 mEq of DEB/100 g of DM were obtained by varying NH4Cl and NaHCO3. Average daily gain showed a linear increase (P < .05) with increased DEB for the first 28 d and a quadratic response (P < .05) for the remainder of the 84-d study. Average daily feed intake was not affected by DEB the first 28 d. However, feed intake over the entire feeding period showed a linear increase with increasing DEB (P < .01). On d 28, plasma Na, K, and Mg were not affected by DEB, whereas Ca followed a quadratic pattern (P < .10). On d 84, plasma Na and Mg decreased linearly with increasing DEB. Plasma Cl concentrations decreased linearly (P < .01) with increased DEB on d 28 and 84. On d 28 arterial blood pH and HCO3 increased linearly (P < .05) with increased DEB, whereas ionized Ca, pCO2, and pO2 were unchanged. On d 84, arterial blood pH (P < .10), HCO3 (P < .05), and ionized Ca (P < .10) increased quadratically, whereas pO2 and pCO2 were not affected by treatment. Ruminal pH increased linearly (P < .05) with increased DEB on d 28 but showed no differences on d 84. These data indicate that DEB affects performance and systemic values in growing feedlot cattle. A DEB in the range of 15 to 30 mEq seemed to provide normal homeostasis of growing steers fed a corn silage-based diet.

Dietary electrolyte balance effects on performance and metabolic characteristics in finishing steers.

One hundred twenty Angus and Angus-hereford crossbred steers (337 +/- 3 kg) were used in a randomized complete block design to evaluate the effects of dietary electrolyte balance (DEB; Na + K - Cl) on performance, acid-base status, and plasma mineral concentrations in cattle consuming a high-concentrate, low-fiber (5% cottonseed hull) diet. The steers were blocked into six groups based on BW and pen location, with five steers per pen. The treatments consisted of 0, 15, 30, and 45 mEq of DEB/100 g of DM. Average daily DMI increased linearly (P < .01) with increasing DEB for the first 28 d then increased quadratically (P < .05) for the remainder of the study. Daily gain tended (P < .10) to increase quadratically, whereas gain:feed was not affected by DEB. Carcass marbling score increased quadratically (P < .05), but other carcass measurements were not affected by DEB. On d 42, arterial blood pH was increased quadratically (P < .10) and HCO3 responded cubically (P < .10) to DEB, whereas ionized Ca, pCO2, and pO2 were not affected by treatment. On d 84, pCO2 (P < .10) and HCO3 (P < .05) decreased linearly as DEB increased. On d 42, plasma concentrations of Na, K (P < .10), and Mg (P < .05) decreased quadratically with increasing DEB. Plasma CV concentrations decreased linearly (P < .05) with increasing DEB on d 42. On d 84, total plasma Ca increased linearly (P < .10) with increasing DEB.(ABSTRACT TRUNCATED AT 250 WORDS)