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PubMed1982

Performance of growing turkey hens as influenced by supplemental dietary fat and different ME:nutrient ratios.

Rate of gain and feed efficiency of growing hen turkeys from 1 to 126 days of age was improved by supplementing diets with a blended fat at levels ranging from 2 to 8%. The favorable response to supplemental fat occurred with diets base on corn or milo with the greatest responses obtained with the corn-based diets. There was no significant difference in body weight and feed efficiency between the hens receiving diets in which the concentration of nutrients were adjusted with increases in metabolizable energy (ME) concentration or diets in which nutrient concentrations remained constant (nonadjusted) irrespective of ME level. Body weight of hens at 126 days of age was increased from .4 to 1.8% for each 1% supplemental fat on the basis of regression analysis. Feed efficiency improvement varied from 1.4 to 1.5% for each 1% supplemental fat. Efficiency of protein utilization was improved significantly by the addition of supplemental fat, occurring primarily with the nonadjusted diet series. Efficiency of ME utilization was improved in both diet series by supplemental fat. Supplemental fat improved protein efficiency of milo-based diets but had no effect on ME utilization. Hens receiving fat-supplemented, corn-based diets exhibited a higher percentage of pendulous crops as compared with hens receiving the control corn diet or the milo-based diets.

Animals↗

PubMed1976

Methionine requirement of developing turkeys from 8-12 weeks of age.

Two experiments were conducted with Large White male turkeys from 8-12 weeks of age to estimate the methionine requirement for optimum growth rate and feed efficiency. The first experiment was conducted with five pens of 22 turkeys per treatment when the mean minimum temperature was 17.2 C and the maximum 32.2 C. The second experiment was conducted with four groups of 14 turkeys per pen when the mean minimum temperature was 1.4 C and the maximum 12.4 C. Initial body weight and rate of gain in the first experiment was lower than that in Experiment 2. Maximum growth and feed efficiency in Experiment 1 were obtained with a methionine level between 1.32 and 1.41 g./mcal. of M.E. and in Experiment 2 between 1.27 and 1.43 g. Adding 0.1% l-cystine to the basal diet in Experiment 2 failed to improve growth or feed efficiency significantly. The estimated requirement for methionine in these experiments agrees with the present estimate of the National Research Council.

Age Factors↗

PubMed1984

Postpartum performance in a diallel cross among lines of mice selected for litter size and body weight.

Postpartum dam performance was studied in a complete diallel design involving five lines of mice. The selection criterion in each line was: large litter size at birth (L+); large 6-wk body weight (W+); an index for large litter size and small 6-wk body weight (L+W-); the complementary index (L-W+) and random (K). Females from the five lines and 20 reciprocal F1 crosses were mated to sires of a randomly selected control line (CC). Correlated responses in average direct genetic and average maternal genetic effects for dam body weight and litter size at parturition persisted throughout lactation, indicating important pleiotropic effects. Major correlated responses occurred for litter weight, feed intake and litter feed efficiency, primarily due to average direct genetic effects. Using general combining ability and net line effects as criteria for choosing among lines, L+ had a distinct advantage if the objective was to increase litter size in a crossing program. If the objective was to maximize litter weaning weight, then W+ would be favored for net line effects, while L+ and W+ would be about equivalent for general combining ability. None of the lines had an advantage for litter feed efficiency. Direct heterosis for dam weight at 12 and 21 d of lactation averaged 2.7 and 1.9%, while for litter size the respective averages were 7.4 and 7.3%. The W+ X L+W- cross exhibited overdominance for litter size. Direct heterosis was moderate for feed intake and litter weight, but was negligible for litter feed efficiency because of the mathematical relationship among the three traits. Maternal heterosis for preweaning progeny growth was suppressed because of heterosis for litter size in the dam. Grand-maternal effects on growth of the young were small and would not be an important consideration in choosing among these lines in a crossbreeding program.

Animals↗

PubMed1992

Restricted feeding and broiler performance: age at initiation and length of restriction.

Broiler cockerels were provided either ad libitum access or restricted to alternate-day access to feed initiated at different ages and lasting for different durations. Regimens consisted of ad libitum feeding; alternate-day feeding; alternate-day feeding from 0 to 6, 6 to 12, or 12 to 18 days of age (DOA); alternate-day feeding from 0 to 12, 0 to 6, and 12 to 18, or 6 to 18 DOA; and alternate-day feeding from 0 to 18 DOA. By 39 DOA, chicks restricted for only one 6-day period reached body weights equivalent to those of chicks eating ad libitum. Body weights of chicks restricted for more than 6 days during the first 18 days after hatch were lower than those of chicks eating ad libitum at 39 DOA. Restriction for more than 6 days improved feed efficiency. Chicks restricted for the whole experiment had superior feed efficiency but low body weights. Antibody responses to sheep erythrocyte antigen were similar among feeding regimens. Response to Escherichia coli inoculation was generally less severe in chicks provided restricted access to feed, and overall mortality was highest in chicks eating ad libitum. Feeding regimens had little effect on organ weights relative to body weight, amount of abdominal fat (either on an absolute basis or relative to body weight), or percentage lipid in the abdominal fat pad.

Abdomen↗

PubMed1976

The tryptophan requirement of male and female broilers during the 4-7 week period.

Studies with broiler type chickens were conducted to determine the minimum tryptophan requirement for maximum growth, optimum feed efficiency and molted body feather count for the 4-7 week period of growth for both male and females. Basal diets analyzed to contain 0.158, 0.157, and 0.147% tryptophan using analyzed tryptophan values of 0.09, 0.01, 0.31, 0.70, 0.40, and 0.46% for corn, gelatin, corn gluten meal, soybean meal, peanut meal-45, and peanut meal-50, respectively. Based on the regression equations for males, the calculated tryptophan requirement for maximum growth, optimum feed efficiency, and molted body feather count for the 4-7 week period is 0.179, 0.170, and 0.172%, respectively for 3300 Kcal. of M.E. per kg. of diet. When expressed as a function of energy, these requirements would be 0.054, 0.052, and 0.052% tryptophan per megacalorie of M.E. per kg. of diet, respectively. Based on the equations for females, the calculated tryptophan requirement for maximum growth, optimum feed efficiency, and molted body feather count is 0.173, 0.163, and 0.172%, respectively for 3300 Kcal. of M.E. per kg. of diet, respectively.

Age Factors↗

PubMed1988

Effects of white lupine in diets of growing turkeys.

In Experiment 1, dehulling white lupine (WL) improved growth and feed efficiency of male Large White turkey poults fed 40% WL during 4 to 21 days of age. In Experiment 2, WL was included proportionally with soybean meal in corn-soy diets of female turkeys from 0 to 17 wk of age. Soybean meal: WL ratios (S:WL) were 1:0 (control), 2:1, 1:1, and 6:1. At 17 wk of age hens on S:WL diets of 2:1 had body weights that were similar to those of birds fed the corn-soy control diets. Growth of hens fed S:WL diets of 6:1 was depressed (P less than .05). Growth depressions were greatest earlier in the study; older birds made compensatory gains. Feed efficiency of hens fed S:WL diets of 1:1 was poorer than that of controls during 0 to 11 wk but better than that of controls after 11 wk of age. Feed efficiency values were similar during 0 to 17 wk for hens fed control and S:WL diets of 2:1 and 1:1. Sensory evaluation of roasted light and dark meat of market birds revealed no taste differences in relation to WL level in the diet.

Animal Feed↗

PubMed1993

Crambe meal is equivalent to soybean meal for backgrounding and finishing beef steers.

Growth, feed efficiency, and carcass characteristics of 70 crossbred steers fed one of four diets were compared. The four diets differed in source of protein supplementation: 100% soybean meal (SB), 67% SB and 33% crambe meal (CM), 33% SB and 67% CM, and 100% CM. All supplements were fed in isonitrogenous amounts. Steers were fed backgrounding diets (12.9% CP) for 84 d and finishing diets (11.2% CP) for 96 d. Average initial weight was 303.4 kg. Backgrounding gains ranged from 1.38 to 1.41 kg/d (P = .92). Finishing gains ranged from 1.43 to 1.47 kg/d (P = .86). Range in entire-experiment gains was 1.41 to 1.46 kg/d (P = .85). Feed efficiencies were equal; entire-experiment efficiencies averaged .144 (P = .96). Growth and efficiency patterns were the same for all four treatments. No overall treatment differences were detected for the seven carcass variables (P = .26 to .96). Average fat depth, longissimus muscle area, yield grade, and dressing percentage were .95 cm, 84.0 cm2, 2.45, and 61%, respectively. At the protein percentage levels of these diets, CM substituted equally for SB for growth rate, feed efficiency, and carcass characteristics.

Analysis of Variance↗

PubMed1982

Effects of monensin fed to replacement dairy heifers during the growing and gestation period upon growth, reproduction, and subsequent lactation.

Sixty Holstein heifers initially weighing 196 kg were assigned by weight to treatments of 0, 200, and 600 mg of monensin. These treatments were fed daily until calving to determine effects of monensin on growth rate, feed consumption, feed efficiency, reproductive performance, and subsequent lactation. Throughout the feeding period the control (0 mg) heifers received sufficient feed to allow a calculated growth rate of .68 kg/day. Monensin treatment groups were fed the same amount of the identical ration over the 448-day experiment. Daily gain, feed intake, and feed efficiency for the 0, 200, and 600 mg treatments were .60, .69, .69 kg, 7.47, 7.46, 7.43 kg, and 12.41, 10.81, 10.81. Although days on trial to first estrus were not different among treatment groups, heifers fed monensin at 200 and 600 mg/day conceived 38 and 34 days sooner than 0 mg heifers. Percent conception, number of calves born, calf birth weight, and calving difficulty were not affected by treatment. Milk production was measured for 120 days subsequent to the experimental feeding of monensin. During this period heifers were fed a common ration ad libitum. Milk production of 17.1, 16.9, and 17.0 kg/day for 0, 200, and 600 mg was not affected by prior treatment.

Animals↗

PubMed2000

Short-term weight cycling in aging female rats increases rate of weight gain but not body fat content.

OBJECTIVE: To examine the effects of short-term repeated weight cycling (WC) above and below the baseline (BL) body weight (BW) on body weight regulation, feeding efficiency, and fat content in old female Wistar rats when dietary fat content was kept constant. DESIGN: Completely randomized. ANIMALS AND METHODS: Female Wistar rats, 11 months old at the beginning of the study, were randomly divided into six groups (12 per group) after a group of rats (BL) was sacrificed for baseline data collection: the high fat gain (HFG) group gained weight to 20% above the BL weight with a high fat diet (HF) and returned to BL level by food restriction (50% of ad-libitum amount) for five cycles; the high fat loss (HFL) group lost weight to 20% below the BL weight by food restriction (50% of ad-libitum amount) and regained to BL level by ad-libitum feeding for four cycles; the high fat ad-libitum (HFA) and low fat ad-libitum (LFA) groups were fed HF and low fat (LF) diet, respectively, ad-libitum for the entire study; the high fat restricted (HFR group) and low fat restricted rats (LFR group) were fed the HF and LF diet, respectively, in restricted amounts to maintain BW at BL level. RESULTS: A trend of increased rates of weight gain and feeding efficiencies from the first to last cycles for both WC groups was observed, and significant increases was observed between cycles 4 and 5. The rate of weight gain and feeding efficiency of HFL was significantly higher than that of the HFG group for all cycles (P<0. 05). The rates of weight loss were significantly decreasing with each successive cycle for HFG, but were unchanged for HFL. Percentage of body fat was not modified permanently from BL to sacrifice for both HFG and HFL groups. The body fat of HFA was higher than that of the other groups (P<0.01), while the body fat of LFA was significantly higher than that of the LFR, BL and HFL groups (P<0.01), but was similar to that of the HFG and HFR groups. The body fat of WC groups and HFR were similar to each other. The percentage of internal fat (retroperitoneal+omental) were similar for the WC groups. The percentage of internal fat of the HFG, HFR and LFA groups were similar, but were significantly higher than that of the BL and LFR groups (P<0.05). The percentage of internal fat of HFA was significantly higher than that of the rest of the groups (P<0.01). CONCLUSION: Short-term WC did not affect body fat content in these animals, but since weight gain became easier and weight loss became more difficult for animals in the HFG group, repeated WC may promote obesity in these rats.

Adipose Tissue↗

PubMed1989

Effect of dietary thyroxine on growth and muscle protein metabolism in broiler chickens.

The effects of thyroxine (T4) on growth, feed efficiency, breast muscle (Musculus pectoralis profundus) weight, liver weight, abdominal fat content, and rates of muscle protein synthesis (Ks) and breakdown (Kd) estimated by N tau-methylhistidine excretion were investigated in broiler chickens of both sexes. Dietary inclusion of .4 ppm T4 resulted in a less abdominal fat content in female chickens and a higher muscle protein synthesis rate in male chickens. Administration of T4 at the level of 1.2 ppm produced higher feed efficiency in both sexes and greater muscle weight and muscle protein synthesis rate in male chickens. This treatment also produced less abdominal fat content in female chickens. Administration of T4 at the level of 3.6 ppm produced lower body weight gain, breast muscle weight, liver weight, and abdominal fat content in both sexes and both higher protein synthesis and breakdown in skeletal muscle in male chickens. These experiments demonstrated that the abdominal fat content could be successfully reduced by dietary inclusion of T4, especially in female broiler chickens. The findings in the present investigation suggested that the improved feed efficiency and muscle growth were largely accomplished by the increase in muscle protein synthesis induced by the dietary inclusion of thyroxine.

Abdomen↗

PubMed1994

Digestible lysine requirement of male and female broiler chicks during the period three to six weeks posthatching.

Experiments were conducted to determine the dietary digestible lysine requirement of male and female broilers (Ross x Ross) during the period 22 to 43 d posthatching. An amino acid-fortified basal diet containing corn, feather meal, and soybean meal as intact protein sources provided .63% total lysine, 20% CP, and 3,200 kcal MEn/kg. The basal diet contained .51% true digestible lysine as determined with a precision-fed cecectomized adult cockerel assay. Growth rate and feed efficiency of birds fed the basal diet fortified with a surfeit level of L-lysine were equal to those of birds fed a methionine-supplemented corn-soybean meal positive control diet (20% CP; 3,200 kcal MEn/kg). Graded levels of synthetic L-lysine (0, .1, .2, .3, .4, .5, .6%) were added to the basal diet to produce growth response curves. Subjecting the growth data to broken-line analysis indicated that the digestible lysine requirement for maximum body weight gain was .85% for males and .78% for females. The requirement for optimum feed efficiency was higher: .89% for males and .85% for female broilers. Breast meat (Pectoralis major) yield increased quadratically in response to lysine addition, and the responses suggested that the lysine requirement for maximal breast yield was not greatly different from that predicted from the feed efficiency data. Abdominal fat (percentage of live body weight) increased from the first to the second increment of lysine, but it then declined as lysine level was increased further.

Adipose Tissue↗

PubMed1991

Effect of a high-fat diet on the performance response to porcine somatotropin (PST) in finishing pigs.

One hundred sixty pigs were used in a 2 x 2 factorial design to compare the performance response to daily injection of porcine somatotropin (PST); (0 or 2 mg/d) in animals fed a 14% CP corn-soy diet (control, C) to those fed a diet with 10% added fat (F) and calorie:protein and lysine:protein ratios similar to that of the C diet. Treatments, assigned randomly to 20 pens (n = 5/treatment) of eight pigs each, were initiated at 90 kg body weight and continued for 28 d. Responses to PST and dietary fat were typical. These include improved gain and feed efficiency and decreased feed intake. The effects of dietary fat on intake and efficiency were accounted for largely by the difference in energy density of these diets. Across diets, PST treatment resulted in a 13% improvement in ADG (P less than .001), a 13% decrease in feed intake (P less than .0001) and a 22% improvement in efficiency (P less than .0001). Of particular interest were the additive (PST x diet interaction, P less than .2) effects of PST and dietary fat on gain in these animals. Pigs treated with PST that were fed the F diet had greater rates of gain than did PST-treated pigs fed the C diet (P less than .05). Treatment with PST increased ADG by 9% in pigs consuming the C diet vs 16% in pigs fed the F diet. Similarly, dietary fat resulted in 4 and 11% increases in ADG in pigs treated with 0 or 2 mg of PST/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2002

Iron deficiency and marginal vitamin A deficiency affect growth, hematological indices and the regulation of iron metabolism genes in rats.

Iron deficiency and marginal vitamin A (VA) deficiency frequently coexist and affect billions of people, mostly children and women, worldwide. The effects of these micronutrient deficiencies alone and in combination on hematologic, biochemical and molecular indices of iron and VA status were investigated in a 2 x 2 randomized blocked study conducted in growing male Sprague-Dawley rats. From 3-8 wk of age, rats were fed one of four purified diets that were either adequate or restricted in iron (Fe) and adequate or marginal in VA: (+)Fe(+)VA, 20.3 and 0.367 micro g/g, respectively, denoted control diet; (-)Fe(+)VA, 3.34 and 0.405 micro g/g; (+)FeVA(m), 22.2 and 0.051 micro g/g; or (-)FeVA(m), 3.03 and 0.055 micro g/g. Weight-matched rats fed adequate micronutrients were included to control for possible confounding effects of Fe deficiency on growth and feed efficiency. Iron restriction reduced (P < 0.05) weight gain, feed efficiency, blood hemoglobin and hematocrit. Plasma and liver iron and plasma transferrin saturation were reduced by approximately 50%, whereas liver transferrin mRNA and protein and transferrin receptor mRNA were elevated, as was liver ferritin light-chain protein and light-chain mRNA. Liver heavy-chain ferritin mRNA, hemopexin, ceruloplasmin and cellular retinol-binding protein mRNA were not affected by iron or VA restriction. Although marginal VA deficiency did not exacerbate indices of poor iron status during iron deficiency, iron deficiency was associated with lower plasma retinol and elevated liver VA concentrations. These results are consistent with an impaired mobilization of liver retinol during iron deficiency as well as multiple alterations in iron metabolism.

Anemia, Iron-Deficiency↗

PubMed1991

The effects of dietary calcium, phosphorus, and protein on the performance and nutrient utilization of broiler chickens.

The effects of varying dietary Ca, available phosphorus (AP), and protein on 5- to 17-day performance (growth and feed efficiency), Ca and P contents of tibia and plasma, ME, and N utilization of broiler chickens were investigated in three experiments. In Experiment 1, high dietary Ca (24.3 versus 11.8 g/kg) reduced performance, N digestibility, and ME, whereas N retention was not affected. Reducing dietary protein (186 or 203 versus 217 g/kg) reduced performance and N retention but increased ME. In Experiment 2, high dietary Ca (25.3 versus 10.7 g/kg) reduced performance, tibia Ca, and plasma P and increased plasma total Ca; whereas the diet with both high Ca (25.3 g/kg) and high AP (9.8 versus 4.3 g/kg) reduced only performance. Reducing dietary protein from 206 to 166 g/kg diet reduced growth but improved feed efficiency and tibia P content. In Experiment 3, a diet containing 25.6 g of Ca and 4.9 or 10.7 g of AP compared with a diet containing 11.2 g of Ca and 4.9 g of AP/kg of diet reduced performance. Reducing dietary protein from 236 to 215 g/kg of diet decreased performance. It was concluded that high dietary Ca reduced growth performance and feed efficiency and that altering the dietary protein from 166 to 236 g/kg of diet did not overcome the growth depression effect of high Ca or of high Ca and AP diets.

Animals↗

PubMed2004

The combined effects of dietary lysine and total sulfur amino acid level on egg production parameters and egg components in Dekalb Delta laying hens.

Dekalb Delta hens were randomly assigned to one of eight dietary treatment groups. Two intakes of lysine (860 and 959 mg/hen per day) and 4 intakes of TSAA (635, 689, 811, 877 mg/hen per day) were combined in a 2 x 4 factorial treatment arrangement and fed from 20 to 43 wks of age. A phase feeding regimen was implemented at 43 wk with lysine intake lowered to 715 or 816 mg/hen per day and TSAA to 578, 607, 699, or 779 mg/hen per day. Cage was the experimental unit (5 hens/cage), and dietary treatments were replicated 8 times. Egg production (EP) and feed consumption were not affected by dietary treatments. Feed efficiency improved linearly by increasing TSAA intake during phase I only. Hen weight gain was improved (P < or = 0.03) by increased dietary lysine (94.2 vs. 135.2 g weight gain/hen). During phase I, hen weight gain was affected quadratically (P < or = 0.02) by TSAA. Increasing TSAA intake up to 689 mg/hen per day increased hen weight gain, but gain decreased at the highest intake. Egg weights (EW) increased (P < or = 0.02) from 59.02 to 60.21 g with increased lysine intake. Increasing lysine intake increased wet and dry albumen percentage, whereas dry yolk percentage decreased with increasing lysine. Total sulfur amino acid intake affected wet yolk, dry yolk, and solids in a quadratic trend, with hens fed 811 and 699 mg/d producing eggs with the greatest yolk solids. Wet and dry shell percentages were not affected by lysine or TSAA, and specific gravity decreased linearly during phase II and overall, with increased dietary TSAA. In conclusion, the dietary lysine at 959 and 816 mg/hen per day for phases I and II, respectively, optimized EW and feed efficiency. Because EP was not affected by dietary lysine, the dietary level for optimizing EP is closer to 860 and 715 mg/hen per day for phases I and II, respectively. Dietary TSAA level for maximum EP and feed efficiency was near 811 and 699 mg/hen per day but for EW may be closer to 877 and 779 mg/hen per day for phases I and II, respectively.

Amino Acids, Sulfur↗

PubMed1988

Age-constant versus weight-constant feed consumption and efficiency in broiler chickens.

Weekly body weights, feed consumption (FC), and feed efficiencies (FE = gain:feed) of 148 male and 125 female broilers were measured individually between 2 and 7 wk of age. Multiple regression analyses of these traits were performed to examine the influence of body weight, weight gain or feed consumption, age, and individual broiler differences. Four different measures of FC and FE from 4 to 6 wk of age were compared within sex: age-constant FC and FE; weight-constant FC and FE; age-constant-weight-corrected FC and FE; and weight-corrected FC and FE, which estimate weight-constant measures. Much of the variation (85 to 90%) among broilers in FC and FE was due to age and body weight differences. Partial regression coefficients indicated that increased body weight at commencement of testing was associated with increased FC and reduced weight gain and FE. Correlations between age-constant and weight-constant FC were zero. This indicates the two forms have little in common. Correlations of body weights and weight gain with FC were negative (-.5 to -.8) for weight-constant values but positive (.5 to .8) for age-constant values. Hence, correlations of the correct (weight-constant) measure of FC with body weights indicate that faster growth gives rise to lower broiler feed consumption. Age-constant and weight-constant FE values were positively correlated (.8 to .9); however, the latter values had larger correlations with body weights and weight gain. These results emphasize the need to correct age-constant FC and FE for body weight differences in order to evaluate differences in efficiency among broilers more accurately.

Age Factors↗

PubMed1976

Sulfur amino acid requirement and foot pad dermatitis in turkey poults.

Five experiments were conducted with Large White poults to determine the effect of methionine and other sulfur-containing compounds on the incidence and severity of dermatitis and on growth and feed efficiency to three or four weeks of age. The poults were housed in battery brooders with wire screen floors in four experiments" and in floor pens with litter in one experiment. Male turkeys were used in four experiments and female turkeys in one experiment. Either a corn-soy diet or a cornstarch-soy diet was used as the basal diet in the various studies. A high incidence of foot-pad dermatitis was observed in poults fed the basal diets unsupplemented with methionine. A high incidence of a dermatitis on the upper part of the beak was also observed in poults maintained in battery brooders but not in floor pens. Adding methionine to the diets significantly lowered the incidence and severity of dermatitis, but cystine and potassium sulfate failed to modify dermatitis. Some foot-pad dermatitis was still observed in poults fed levels of methionine more than adequate to meet the requirements for optimum growth and feed efficiency. The incidence and severity of foot-pad dermatitis generally increased with age during the experiment among poults fed methionine-supplemented diets. Although methionine deficiency is a major cause of foot-pad dermatitis in poults, other environmental or dietary factors also appeared to be involved in the development of the condition. The methionine requirement for optimum growth, feed efficiency, and prevention of dermatitis was approximately 0.6% or 2.1 g. per mcal. of metabolizable energy (M.E.). This is higher than the present recommendation of the National Research Council. With corn-soybean meal diets the requirement for total sulfur amino acids is approximately 1.05% or 3.7 g. per mcal. of M.E.

Amino Acids, Sulfur↗

PubMed2004

Effects of diet complexity and dietary lactose levels during three starter phases on postweaning pig performance.

Four experiments involving 1,005 crossbred pigs weaned at 19 +/- 2 d of age evaluated the effect of diet complexity and lactose level on starter pig performances. Experiment 1 was a randomized complete block (RCB) conducted in nine replicates with 135 pigs. A complex diet using several protein sources, a semicomplex diet with fewer protein sources, and a simple diet of corn and soybean meal comprised the three treatment groups. All diets contained 25% lactose (as-fed basis) with lysine (total) constant from d 0 to 14 (1.55%) and d 14 to 28 (1.45%), respectively. Gain, feed intake, and feed efficiency (P < 0.05) improved as diet complexity increased during both periods. In Exp. 2, 240 pigs in eight replicates in a RCB design were fed complex diets, but dietary lactose (total; as-fed basis) levels ranged from 10 to 35% in 5% increments from 0 to 14 d after weaning. From 14 to 30 d, a common 17% lactose diet was fed to evaluate the effects of early lactose level on subsequent responses. Gains (P < 0.05) increased for the 0- to 7- and 0- to 14-d periods as lactose increased to 30%. Similar gains resulted for all treatment groups from 14 to 30 d after weaning, with no evidence of compensatory responses to early lactose levels. In Exp. 3, 330 pigs were fed complex diets. From 0 to 7 d after weaning, the diets contained 25% lactose (as-fed basis), and from 7 to 21 d postweaning, the lactose levels ranged from 7 to 31% in 5% increments. Gain (P < 0.01) and feed efficiency (P < 0.05) increased from 7 to 21 d to the 17% lactose level. In Exp. 4, 300 pigs were fed 25 and 17% (as-fed basis) lactose diets from 0 to 7 and 7 to 21 d postweaning, respectively. From 21 to 35 d postweaning, lactose levels of 0 to 20% in 5% increments were added to a corn-soybean meal diet. The experiment was conducted as a RCB design in 12 replicates. Gain (P < 0.05) and feed intake (P < 0.05) increased to 10 to 15% lactose. When the data from Exp. 4 were partitioned into lighter (15.0 kg) and heavier (17.7 kg) pig weight replicates, only the lighter replicates had significant improvements in gain, feed intake, and feed efficiency (P < 0.05) in response to dietary lactose. These results demonstrated that starter pigs performed better when fed complex diets, that dietary lactose levels of 25 to 30% (to 7 kg BW) during the initial week postweaning, 15 to 20% lactose during d 7 to 21 (to 12.5 kg BW), and 10 to 15% lactose during d 21 to 35 postweaning (to 25 kg BW) resulted in maximum performance.

Animal Feed↗