Technical considerations for maize flour and corn meal fortification in public health: consultation rationale and summary.

Fortification is the purposeful addition of vitamins and minerals to foods during their industrial processing, as a way to improve the nutrition and health of populations who consume these foods. Twelve countries have mandatory maize (Zea mays subsp. Mays) flour or meal fortification. The World Health Organization (WHO) is updating evidence-informed guidelines for the fortification of staple foods in public health, including the fortification of maize flour and corn meal with iron and other micronutrients. Although there is limited experience with fortification of maize, mass fortification of maize flour with at least iron has been practiced for many years in several countries in the Americas and Africa: Brazil, Costa Rica, El Salvador, Kenya, Mexico, Nigeria, Rwanda, South Africa, Tanzania, Uganda, the United States, and Venezuela. The WHO, in collaboration with the Sackler Institute for Nutrition Science and the Flour Fortification Initiative (FFI), convened a consultation on technical considerations for fortification of maize flour and corn meal in public health in New York, New York on April 8-9, 2013 to provide input into the guideline-development process and to discuss technical considerations of the fortification processes for maize flour and corn meal.

Legislative frameworks for corn flour and maize meal fortification.

Corn flour and maize meal fortification can benefit the consumer when the added nutrient contents are in amounts appropriate to address nutrient gaps. Legislative instruments (standards and regulations) are needed to provide guidance to the producers and food control authorities. We reviewed a number of national standards and regulations of fortified corn flour and maize meal and identified constraints; contrary to current belief, the practice of using minimum contents or ranges of nutrients has caused confusion, misinterpretation, and conflict, and should therefore be abandoned. On the basis of the findings, a model of fortification legislation is proposed, in which the additional content and the expected average nutrient content in a final product are recommended as the main parameters for quality control and enforcement. For labeling, the average content, or one adjusted to the expected content of the product at the market, can be applied. Variation in micronutrient contents should still be checked to ensure homogeneity but with adherence to clear procedures of sampling and testing, which should be part of the standards and regulations.

Stability of key micronutrients added to fortified maize flours and corn meal.

Maize is a dietary staple in many countries. Although nutritious in many ways and a good source of energy, typical maize lacks several key micronutrients (MNs) that are often added to maize meals or flours to enhance nutritional value. Many factors affect MN stability in maize products, including uncontrolled conditions during distribution, long storage times, and MN premix composition. Consumer preparation also affects the final MN content of food. This review summarizes research relating to MN stability during processing, transport, storage, and meal preparation, focusing on those MNs most often added to maize and maize-based foods. Significant losses in B vitamins (B1, B2, B3, B6, B9, and B12) occur during manufacturing, distribution, and cooking. Added minerals (e.g., iron, zinc, calcium) are generally retained, although phytates in corn may affect bioavailability. Vitamins A and D3 are recent additions to fortification premixes for maize and are not well studied. Although there have been numerous studies of MN fortification in wheat flour, maize has not been as thoroughly examined, so recommendations are not as well supported. Future investigations should include well-designed and executed studies of the most labile MNs added to maize flours and meals, and their fate during all steps of processing, shipping, and preparation.

Effects of extraction conditions on improving the yield and quality of an anthocyanin-rich purple corn (Zea mays L.) color extract.

Purple corn (Zea mays L.) is a rich and economic source of anthocyanin colorants and functional ingredients. However, high levels of anthocyanin-rich waste are generated during processing, reducing the yields and increasing the costs of the final product. This waste has been associated with anthocyanin complexation with tannins and proteins. Our objective was to evaluate anthocyanin extraction methods to reduce purple corn waste. Different solvents (water, 0.01%-HCl-acidified water, and 0.01%-HCl-acidified ethanol), temperatures (room temperature, 50, 75, and 100 degrees C), and times of exposure to the solvents were investigated. Acetone (70% acetone in water) extraction was used as control. Anthocyanins, total phenolics, tannins, and proteins in extracts were measured by the pH differential, Folin-Ciocalteu, protein precipitation, and BCA assay methods. Qualitative analyses were done by HPLC coupled to a PDA detector and SDS-PAGE analysis. Water at 50 degrees C achieved the highest yield of anthocyanins (0.94 +/- 0.03 g per 100 g dry corncob) with relatively low tannins and proteins, comparable to the anthocyanin yield obtained by 70% acetone (0.98 +/- 0.08 g per 100 g dry corncob). Extending the extraction time from 20 to 60 min and using consecutive reextraction procedures reduced anthocyanin purity, increasing the yields of other phenolics. A neutral protease was applied to the extracts and effectively decomposed the major protein that was believed to contribute to the development of anthocyanin complexation and waste generation. Extraction time, consecutive reextraction procedures, and enzyme hydrolysis should be considered for high yield of anthocyanins and waste reduction.

Effects of soybean fortification on protein quality of tortilla-based diets produced from regular and quality protein maize.

The physiological development of laboratory rats fed with a typical indigenous tortilla diet was studied for two generations. The experiment compared casein control diet and five different types of diets: (1) a diet of tortillas obtained from fresh masa (FM); (2) regular tortillas produced from enriched dry masa flour containing vitamins B1, B2, niacin, folic acid, and the microminerals iron and zinc (REDMF); (3) tortillas produced from enriched dry masa flour fortified with 6% defatted soybean meal (FEDMF); (4) tortillas produced from enriched quality protein maize flour (EQPM); and (5) and, tortillas produced from enriched quality protein maize flour fortified with 3% defatted soybean meal (FEQPM). The growth of rats fed FEDMF and FEQPM diets was significantly higher (P < 0.05) in both generations than their counterparts fed EQPM, REDMF, or FM diet. Animals fed quality protein maize (QPM) tortilla had the highest protein digestibility, but the FEQPM and FEDMF diets had the highest biological value (BV), net protein utilization (NPU), and protein-digestibility-corrected EAA scores (PDCEAAS). The difference among treatments was more evident in the second-generation rats. The pregnancy rate, number of newborns/litter, litter weight, and newborn survival rate was also higher for rats fed FEDMF, EQPM, and FEQPM diets than their counterparts fed REDMF and FM.

The influence of processed corn and supplemental fat on digestion of limit-fed diets and performance of beef cows.

Trial 1, 135 crossbred cows with calves were used to compare limit-fed corn-hay diets with ad libitum hay and cracked with whole corn in limit-fed diets. Diets were to supply similar TDN intakes. Cow-calf pairs were fed treatment diets from 24 h after parturition until the beginning of the breeding season (62+/-13 d). Cow and calf performance was not affected (P > .05) by intake level or corn processing. In Trial 2, 48 crossbred primiparous cows with calves were used to determine the effect of adding 4% fat to a limit-fed corn-hay diet. Diets were to provide similar TDN intakes. Cow-calf pairs were fed treatment diets from 24 h after parturition until the breeding season started (79+/-14 d). Cow weight, condition score change, and calf gain were not affected (P > .05) by supplemental fat. Milk yield and composition were not different (P > .05) 52 d postpartum. At 92 d postpartum, milk production was 65% greater (P = .01) for cows that received supplemental fat. In Trial 3, four cannulated steers were used to evaluate the influence of corn processing and fat supplementation on digestion. Feeding cracked corn improved (P < .05) DM and OM digestion compared with whole corn. Adding 4% supplemental fat did not influence (P > .05) digestion. Limit-feeding a corn-hay diet is an alternative to feeding ad libitum hay that can accomplish similar cow and calf performance. Supplementation of 4% fat can be used in a limit-fed diet without detrimental effects on digestion, lactation, or cow and calf performance.

Effect of degradable and escape protein and roughage type on performance and carcass characteristics of finishing yearling steers.

We evaluated protein sources for finishing steers in two randomized complete block design experiments. Experiment 1 used 144 steers (334 kg) with 2 x 3 factorially arranged treatments. Basal diets contained .9% urea or 5.6% soybean meal (SBM) and were either not supplemented or supplemented with additional protein (2%) from blood meal-corn gluten meal (BMCG) or SBM. Steers fed urea-containing diets consumed 4.6% (P < .10) more feed than those fed SBM-supplemented basal diets. On the basis of carcass weights, steers fed diets containing SBM as the basal protein source were 3.8% (P < .10) more efficient than those fed urea-containing diets; supplying additional SBM improved gain efficiency (G/F) 4.3% (P < .10) compared with BMCG. In Exp. 2, 384 steers (367 kg) were fed diets containing 1.0% urea (DM basis) and 10% roughage as either sorghum silage (four diets) or alfalfa hay (two diets). Additional protein was either not provided or provided (2%) as SBM, sunflower meal (SFM), or a 50:50 (N basis) SBM:SFM blend in silage-containing diets; for diets containing alfalfa, additional protein was either not provided or provided (2%) as SBM. Averaged across roughage source, added SBM tended (P = .16) to increase ADG. Dressing percent decreased (P = .09) with added SBM but was higher (P = .04) with alfalfa as roughage source. Feeding alfalfa vs sorghum silage as the roughage source increased carcass adjusted ADG 4.3% (P = .06) and G/F 4.8% (P = .02). Supplementing high-grain diets with SBM enhanced diet utilization, but BMCG was of little value.

Effect of amino acid supplementation on whole-body protein turnover in Holstein steers.

We used the [15N]glycine single-dose urea end-product technique to measure whole-body protein turnover in six Holstein steers (250 +/- 18 kg). Steers were implanted with Revalor-S and continuously infused abomasally with water (4 L/d) or amino acids (AA; in 4 L/d water) in a crossover experiment (two 14-d periods). The AA infusion contained the following (g/d): lysine (5.3), methionine (3.3), threonine (3.2), tryptophan (1.0), histidine (2.1), and arginine (5.5). Steers were fed a diet containing 85% rolled corn, 10% prairie hay, and 1.1% urea (DM basis) at 2.16% of body weight. Nitrogen retention tended (P = .15) to increase with AA infusion, from 27.9 to 32.9 g N/d. Amino acid infusion numerically increased whole-body protein turnover from 168.6 to 183.2 g N/d, protein synthesis from 152.6 to 169.3 g N/ d, and protein degradation from 124.7 to 136.4 g N/d. Enhanced protein accretion may have resulted from a larger increase in protein synthesis than in degradation. The tendency for increased N retention is interpreted to suggest that the implanted, lightweight Holstein steers fed a corn-urea diet in our study were able to respond to AA supplementation, suggesting that at least one of the infused AA was limiting in the basal diet. Protein turnover data suggest that cattle, like other animals, may increase protein synthesis and protein degradation in response to supplementation with limiting AA. The [15N]glycine single-dose urea end-product technique for measuring whole-body protein turnover in cattle may be useful.

The efficacy of phytase in corn-soybean meal-based diets for laying hens.

Microbial phytase hydrolyzes poorly degradable vegetable phytate P in the gastrointestinal tract of poultry; thereby increasing the availability of organic P to an extent that remains to be established. For this purpose, the P equivalency value of phytase in corn-soybean meal layer diets was assessed in three experiments (two short-term absorption studies and one performance trial lasting a complete production period). In the first absorption study, two basal diets containing 30 or 40 g Ca/kg diet were supplemented with either phytase [0, 250, or 500 phytase units (FTU)/kg diet] or with monocalcium phosphate (MCP; 0, 0.5, or 1.0 g P/kg diet) and fed to layers from 20 to 24 wk of age. The ileal absorption of Ca and P was measured during the last week. It was shown that 250 FTU/kg diet hydrolyzed an amount of phytate P that was equivalent to 1.3 g P from MCP. At the highest phytase inclusion level (500 FTU/ kg diet), a lower value of equivalency was observed, as P absorption was almost maximal at the lower level of phytase inclusion (250 FTU/kg diet). Phytase hydrolyzed phytate-bound P effectively at both Ca levels, although this degradation was significantly reduced by 12 percentage units at the higher dietary Ca level. The second absorption study, used 0, 250, and 500 FTU phytase/kg diet and 0 and 1.0 g P/kg diet of MCP. All diets were standardized at 35 g Ca/kg diet. The ileal absorption of Ca and P was determined at 24 and 36 wk of age. These values were significantly reduced in 36-wk-old hens compared to 24-wk-old hens. At 24 wk of age, phytic acid P degradation was significantly improved with increasing levels of phytase up to the maximum inclusion level of 500 FTU/kg diet (maximum phytic acid-P degradation at the end of the small intestine was 66%). In this experiment, the dose of 250 FTU/kg diet was equivalent to 0.8 g MCP-P. In Experiment 3, either phytase or MCP-P was added to a corn-soybean meal layer diet, containing 40 g Ca/kg diet and 3.6 g P/kg diet, at levels of 0, 100, 200, and 300 FTU/kg or levels of 0, 0.3, 0.6, and 0.9 g MCP-P/kg, respectively. Production performance was measured from 18 to 68 wk of age. Diets were consumed ad libitum. Growth, production performances (except kilograms of feed per kilogram of egg), and tibia parameters were significantly improved by dietary supplementation of the negative control diet with either phytase or MCP-P. Growth, egg production, and feed conversion ratio of the hens from the supplemented groups remained good throughout the experiment. No phytase dose effects on the production characteristics or tibia parameters were observed, indicating that the P requirements of the laying hens were met throughout the production period even at the lowest level of supplementation.

Escape protein supplementation of steers fed grass silage-based diets.

Beef steers (Trials 1 and 2, 280 +/- 2 kg; Trial 3, 330 +/- 2 kg) were fed diets of 67.5% wheat (Trial 1) or oat silage (Trials 2 and 3), 20.5% barley, and 12% supplement in randomized complete block design growth trials. Dietary treatments were graded levels of supplemental escape protein (EP) from corn gluten meal (Trial 1, 0 to 213 g/d escape protein) or animal by-products (1:1:1 DM mixture of blood, feather, and meat and bone meals, 0 to 223 or 0 to 317 g/d of escape protein in Trials 2 and 3, respectively) to titrate amounts needed to maximize steer live weight gain. As supplemental EP from corn gluten meal increased, steer live weight gain increased linearly (P < .001) and feed-to-gain decreased linearly (P < .001). Supplementation with 135 g/d of corn gluten meal EP (335 g/d of corn gluten meal) increased average daily gain from .76 to .91 kg/d. As supplemental EP from animal by-products increased, steer live weight gain increased quadratically (P < .05) and feed-to-gain decreased linearly (P < .01). Supplementation with 223 or 317 g/d of animal by-product EP increased live weight gain by .27 kg/d. Supplemental escape protein was needed to increase live weight gain of steers consuming ensiled forage diets due to low EP contents of silages (7, 3, and 23% of CP in Trials 1, 2, and 3, respectively) and barley (15, 27, and 22% of CP in Trials 1, 2, and 3, respectively) and limited microbial protein synthesis.

Influence of supplementing corn-soybean meal diets with vitamin E on performance and selected physiological traits of male turkeys.

Three experiments were conducted to determine the effects of supplementing practical diets of male turkeys with dl-alpha-tocopheryl acetate (TA). In Experiment 1, a factorial arrangement of dietary treatments [0, 12, 50, 150, and 300 IU TA/kg with 0 or 300 mg ascorbic acid (AA)/kg] was used. These 10 treatments were fed to poults from 1 to 41 d of age. From 41 to 118 d of age, the AA treatments were discontinued, and the 300 IU TA treatment groups were changed to 12 IU TA/kg. Neither TA nor AA treatments affected 41-d BW, feed to gain ratio (FE), or livability. No effects of dietary TA concentrations on turkey performance were observed through 118 d of age alpha-Tocopherol (TOC) concentrations of plasmas and livers were increased by increments of dietary TA, with substantial liver storage when toms were fed 150 IU TA/kg from 1 to 118 d. Supplementing diets with 0, 25, 50, 75, or 100 IU TA/ kg in Experiments 2 and 3 had no effect on performance of toms through 119 and 105 d, respectively. alpha-Tocopherol concentrations of plasma and red blood cells (RBC) increased linearly with increments of dietary TA. The same was true for livers in Experiment 2. Susceptibility of RBC to hemolysis induced by 400 microM t-butyl hydroperoxide (TBH) in Experiment 2 decreased with increasing dietary TA, and these decreases corresponded to increases in TOC concentration of RBC. However, the relationships between hemolysis and dietary TA or RBC TOC were inconsistent in Experiment 3 and varied according to concentration of TBH (200, 300, or 400 microM) and age of the toms. At 105 d of age, RBC of toms fed no supplemental TA were resistant to hemolysis, irrespective of dietary TA and TBH concentration. In Experiment 3, there were no indications of dietary TA effects on plasma peroxide concentration or activity of plasma creatine kinase. A positive relationship between dietary TA and blastogenic responses of blood lymphocytes was observed with concanavalin A when toms were at 44 d but not at 23 or 86 d of age. The overall data indicate that corn-soybean meal diets containing from 6 to 20 IU TOC/kg, but no supplemental TA supported satisfactory performance and well-being of male turkeys from 1 d of age to market ages when the turkeys were free of disease, as was true in the research reported here.

Feeding value of cottonseed meal for feedlot cattle.

One hundred twenty crossbred steers (294 kg, initially) were used in a 141-d finishing trial. Four concentrations (8, 16, 24, and 32% of diet DM) of cottonseed meal (CSM, prepressed solvent-extracted) replaced steam-flaked corn in a corn-based finishing diet. Increasing level of CSM decreased ADG (linear component, P < .10), feed efficiency (linear component, P < .01), and dietary NE (linear component, P < .01). Observed dietary NE was 99% of expected at 8 and 16% CSM but 95% of expected at higher levels of inclusion (linear component, P < .05). Level of CSM did not influence (P > .10) dressing percentage, longissimus area, fat thickness, or retail yield. Eight Holstein steers (285 kg) were used in a replicated 4 x 4 Latin square design to evaluate treatment effects on characteristics of digestion. Ruminal digestibility of OM decreased (linear component, P < .05) as CSM increased, although ruminal digestibility of starch and feed N were not affected (P > .10). Ruminal escape protein from CSM was 58%. Total tract starch digestion was not altered (P > .10), but total tract digestibility of OM and GE decreased (linear component, P < .05) and digestion of N increased (linear component, P < .01) as CSM replaced steam-flaked corn. The ratio of observed to expected DE value of the diets was similar across CSM levels, averaging .99. Thus, comparative DE value of CSM was not affected by level of inclusion, averaging 3.32 Mcal/kg. We conclude that the NEm and NEg values of CSM are 1.88 and 1.24 Mcal/kg, respectively, and in close agreement with tabular values. However, CSM should not exceed 16% of DMI, because higher levels may depress cattle performance and replacement value of CSM.

Factors affecting phosphorus and calcium digestibility in diets for growing-finishing pigs.

In two experiments, we investigated various factors that affect the estimation of the apparent total tract digestibility (ATTD) of DM, Ca, and total P in diets for growing-finishing pigs. In Exp. 1, the effects of age, housing, and calculation method (indicator [Cr2O3] vs 10-d total collection) were determined. Eighteen barrows and gilts (40 to 95 kg BW) were housed in six pens, and ATTD was estimated using the indicator method. Twelve barrows were housed in metabolic crates, and ATTD was estimated using both calculation methods. Dietary treatments were 1) a tapioca-soybean-barley-based diet, 2) Diet 1 supplemented with 400 FTU microbial phytase/kg of diet, and 3) a corn-soybean meal-based diet: In Exp. 2, six barrows (95 to 120 kg BW) were fed a phytase-deficient diet to investigate the effects of coprophagy (40 g fresh feces/kg of diet) and movement. Pigs were fed at 2.8 times maintenance requirement (418 kJ ME/BW.75); water supply was 2.5 L/kg of feed. The ATTD increased as BW increased. Phytase enhanced total P ATTD by an average of 18.1 percentage units. The ATTD of DM was higher and the ATTD of Ca and total P (P < .001) were lower in pigs housed in pens than in pigs housed in metabolic crates. Fecal consumption and movement led to numerical increases in Ca (P = .217) and total P (P = .103) ATTD. Estimates of Ca and total P ATTD using pigs in metabolic crates are lower than estimates in practice.

Effects of supplemental energy source and amount on forage intake and performance by steers and intake and diet digestibility by sheep.

Two levels of concentrate supplements containing different types of carbohydrates (corn-soybean meal, CSBM; wheat middlings, WM; and soybean hulls, SBH) were evaluated for effects on forage intake and performance in growing steers and total diet digestibility in sheep. In Exp. 1, 63 crossbred yearling cattle (298 and 377 kg initial BW for yr 1 and 2, respectively) were given ad libitum access to chopped bermudagrass (Cynodon dactylon [L.]) hay with no supplementation (CONTROL) or with 25 or 50% of projected total TDN intake from CSBM, WM, or SBH. In Exp. 2, digestibilities of organic matter (OMD) and neutral detergent fiber (NDFD) were determined with sheep fed levels of hay and concentrates similar to those used in the growth trials. Hay intake was 1.99% of BW for steers fed hay alone and averaged 1.93% of BW in steers fed supplements at the low level. At the high level of concentrate supplementation, hay intake was depressed (P < .001) to a similar extent (1.63% of BW) in steers supplemented with CSBM, WM, or SBH. AT the low concentrate level, shrunk ADG was similar (.63 kg/d) among supplements, but at the high concentrate level steers fed SBH had higher (P = .06) shrunk ADG (.95 kg/d) than steers fed CSBM (.76 kg/d). Body condition score (BCS) increased more (P = .06) for CSBM- and SBH- than for WM-supplemented steers. Total tract OMD was lower (P < .001) in sheep fed WM (54.8% for low and 56.9% for high supplementation levels) than in sheep fed CSBM (57.4 and 62.6%) or SBH (57.2 and 62.5%). Total tract NDFD was higher (P < .001) for the SBH (58.9% for low and 63.3% for high levels) diets than for CSBM (54.6 and 51.0%) or WM (54.6 and 51.8%) diets. Supplements containing highly digestible fiber (SBH) produced less negative associative effects than high-starch supplements (CSBM) when fed with bermudagrass hay at the high level (.8 to 1% of BW), but no differences were found at the low feeding level (.4 to .5% of BW).

Response of lactating cows to methionine or methionine plus lysine added to high protein diets based on alfalfa and heated soybeans.

Lactation diets based on wilted alfalfa silage and heated whole soybeans are common in the midwestern US. We examined the milk production response of multiparous Holstein cows to the addition of ruminally protected methionine at two percentages to a basal total mixed ration. An additional total mixed ration included both methionine and lysine supplementation. Sixteen Holstein cows in early lactation were used in a replicated 4 x 4 Latin square design with 21-d periods. Milk production, milk composition, and dry matter intake were determined for the last 5 d of each period. Milk production (41.5 kg/d), dry matter intake (25.9 kg/d), and milk fat concentration (3.26%) were unaffected by the supplementation of amino acids. The addition of methionine increased milk protein concentration and yield linearly. Each gram of methionine increased milk protein yield by 4 g, and milk protein concentration increased from 2.89 to 2.99% with the addition of 10.5 g/d of methionine. The proportion of casein N in total milk N was unaffected by treatment. The addition of lysine did not elicit a response. Total mixed rations based on alfalfa haylage, heated soybeans, and animal proteins were clearly limited by their methionine content but were adequate in their lysine content.

Soaking increases the efficacy of supplemental microbial phytase in a low-phosphorus corn-soybean meal diet for growing pigs.

Sixty-three crossbred barrows averaging 18.7 kg initial BW were used in a 6-wk study of the effects of soaking on the efficacy of supplemental microbial phytase (Natuphos, BASF) in a low-P corn-soybean meal diet. The basal corn-soybean meal diet contained .06% available P, .32% total P, and .55% Ca with no added inorganic P. The basal diet was supplemented with 0, 250, or 500 phytase units (PU)/kg of diet. The diet was fed dry or soaked (2 parts water:1 part diet and mixed for 2 h at 30 degrees C before feeding) in a 3 x 2 factorial arrangement. A positive control diet was supplemented with inorganic P and provided .23% available P, .48% total P, and .60% Ca. Pigs were individually penned and fed their respective diets to appetite in four equal meals daily. There were no soaking x phytase interactions (P > .1 to .6) for growth performance criteria. Daily gain and gain/feed ratio were increased (P < .01) by soaking and increased linearly (P < .01) by phytase. Daily feed intake was increased linearly (P < .01) by phytase. There were soaking x phytase quadratic interactions (P < .01) for apparent P absorption criteria because soaking the 250 PU/kg diet increased P absorption similar to that obtained with the 500 PU/kg diet fed dry. Apparent P absorption criteria were increased by soaking (P < .01) and were increased linearly (P < .001) and quadratically (P < .03) by phytase. Phytase reduced fecal P excretion 37 to 40% with dry feeding (P < .03) and 48 to 49% with soaking (P < .01).

Supplemental chromium picolinate influences nitrogen balance, dry matter digestibility, and carcass traits in growing-finishing pigs.

Four trials were conducted to determine the influence of feeding 200 ppb Cr as chromium picolinate (CrPic) on DM digestibility, N balance, and carcass traits of growing-finishing pigs. A 15% CP corn-soybean meal diet was fed during the grower phase, and a 13% CP corn-soybean meal diet was fed during the finisher phase. In each of three trials, crossbred barrows (six littermate pairs) were used for two N balance periods (end of grower, 61.3 kg; end of finisher, 98.9 kg). After the second balance period, all the barrows were killed and carcass data were collected. Initial and final BW were 23.5 and 104.9 kg, respectively. Growth rate was similar for control and CrPic-fed pigs in all trials. The rate of N absorption was increased by feeding CrPic (P < .05), but N retention was increased only numerically (P = .14). Dry matter digestibility was also increased by feeding CrPic (P < .02). Dressing percentage and backfat thickness at the 10th and last rib did not differ between treatment groups. Longissimus muscle area was larger (P < .05) for pigs fed CrPic. In Trial 4, crossbred barrows (six littermate pairs; initial BW, 82.0 kg) were used in a switch-back design with an extra period. Digestibility of DM (P < .02) and absorption of N (P < .06) were improved with only a numerical increase (P = .22) in N retention. No carryover effect was observed. These findings show that pigs fed 200 ppb Cr from CrPic can have larger longissimus muscle areas and that Cr supplementation improved N absorption and DM digestibility.

Effects of fish meal in beef cattle diets on growth performance, carcass characteristics, and fatty acid composition of longissimus muscle.

We investigated the effects of fish meal (FM) in beef cattle diets on growth performance, carcass characteristics, and fatty acid (FA) composition of longissimus muscle in 63 yearling steers (335 +/- 23 kg). High-moisture corn and alfalfa silage diets were supplemented with either a corn gluten/blood meal mixture or FM at 10% of the diet. Fish meal contained (as-is basis) 5.87 g/kg eicosapentaenoic acid (EPA) and 9.84 g/kg docosahexaenoic acid (DHA). Seven strategies were developed to feed either a control diet (no FM) or diets containing 5 or 10% FM with FM fed for either 56, 112, or 168 d before slaughter. Average daily gain and feed efficiency were not affected (P > .10) by FM feeding but DMI decreased. Within FM diets, cattle fed 5% FM consumed more (P < .01) DM and gained more (P < .02) than cattle fed 10% FM. Carcass traits were not affected (P > .05) by feeding strategy except for fatter (P < .05) and lower (P < .06) yielding carcasses in cattle fed 5 vs 10% FM diets. Fish meal feeding increased (P < .01) concentrations of (n-3) FA, including EPA and DHA, and decreased (P < .05) concentrations of arachidonic acid. Increasing the amount of dietary FM further increased (P < .01) concentrations of EPA and DHA and decreased (P < .05) concentrations of (n-6) FA. We estimate that a 114-g steak from cattle fed 10% FM would supply 35 to 90% of the current average daily intake of EPA and DHA in North America. The results indicate that FM may have a role in niche marketing of beef provided that eating quality is not compromised.

Ardacin for steers grazing endophyte-free fescue pasture: effects on live weight gain, forage intake, nitrogen and fiber digestion, ruminal fluid kinetics, ruminal fermentation, and serum hormones and metabolites.

Growth and digestion studies were conducted to evaluate the use of ardacin as a feedgrade antibiotic for enhancing digestive function and growth in grazing steers. In Exp. 1, 90 yearling steers (average initial BW of 248 kg) used in a randomized complete block design (block = weight group) grazed fescue pasture without supplementation (CON) or with daily supplements (DM basis) of .4% of BW supplemental ground corn (CRN) or .4% of BW supplemental corn supplying 120 mg of ardacin (ARD). In Exp. 2, 12 ruminally and duodenally cannulated steers and three ruminally cannulated steers (Hereford x Angus; average BW of 347 kg) were used to evaluate the effects of the same supplements used in Exp. 1 on ruminal fermentation and digestion. In Exp. 1, ARD-supplemented steers weighed more (P < .01) at the conclusion of the study than CRN steers, which together weighed more (P < .01) than CON steers. Average daily gain was greater (P < .10) in supplemented than in CON steers; ARD steers had greater (P < .01) ADG than CRN steers. In Exp. 2, forage intake and harvesting efficiency did not vary (P > .10) with supplementation or type of supplement, but total intake reflected (P = .03) the addition of corn to the forage diet. Addition of ardacin increased (P = .02) ruminal pH compared with CRN steers. Ardacin decreased ruminal molar proportions of acetate and increased (P = .01) propionate proportions when compared with CRN steers. Total tract N digestibility was affected (P < .10) by supplementation and by addition of ardacin to the diet. Addition of ardacin to the ground corn supplement increased ADG, in part by enhancing acetate:propionate ratios and increasing N digestion.