Biomedical subjects

J G Fadel

Publications and source records attributed to J G Fadel.

14 recordsLinked to original sources

PubMed2006

Metabolic models of ruminant metabolism: recent improvements and current status.

The NC-1009 regional research project has two broad goals of quantifying the properties of feeds and the metabolic interactions among nutrients that influence nutrient availability for milk production and that alter synthesis of milk, and using those quantitative relationships to challenge and refine computer-based nutrition systems for dairy cattle. The objective of this paper was to review progress in modeling. Significant progress has been made in model refinements over the past 10 yr as exemplified by the most recent NRC model (2001) and work on the Molly model of Baldwin and colleagues (1987). These models have different objectives but share many properties. The level of aggregation of the NRC model (2001) does not allow detailed analyses of specific metabolic reactions that affect nutritional efficiency. The Baldwin model is aggregated at the pathway level and is therefore amenable to assessment with a broad range of biological measurements. Recent improvements to that model include the addition of an ingredient based input scheme, use of in situ data to set ruminal protein degradation rates, and refinement of the representation of mammary cell numbers and activity. Although the Baldwin model appears to be appropriate structurally, several parameters are known to be inadequate. Predictions of ruminal N metabolism and total-tract starch digestions have similar accuracy as the NRC model. However, the NRC more accurately predicts total-tract fiber digestion and both models significantly overpredict total-tract lipid digestion. These errors contribute to overpredictions of weight retention when simulating full lactations with the Baldwin model and may result in performance prediction errors with the NRC model. Limitations remain in the descriptions of metabolism and metabolic regulation of the splanchnic, viscera, adipose tissue, body muscle, and mammary tissue. Integration of genetic control mechanisms can expand these efforts to assist genetic selection as well as feeding management decisions.

Animal Feed↗

PubMed2004

Technical note: Estimating parameters of nonlinear segmented models.

The objective of this technical note is to develop an applied technique to estimate parameters using the Statistical Analysis System's nonlinear procedure (SAS PROC NLIN) for segmented models that have a change point or lag as one of the parameters. The goal is to select good starting values for the parameters near the global minimum or at least near a lower local minimum compared with what might be achieved using traditional starting values. The model used was f1 (t) = B1 + B4 if t < or = B3 and f2(t) = B1*exp[-B2*(t - B3)] + B4 if t > B3, where B1, B2, B3, and B4 are the parameters that require estimates, B3 is the change point or lag, and t = time. This technical note illustrates the solution when a traditional grid search for starting values is used and demonstrates a modified technique where starting values are systemically determined by fixing B3 over a range of reasonable values and then using the parameters from the solution with the lowest residual sums of squares as the starting values for the final solution. The modified method resulted in a lower square root of mean square error compared with the traditional method. The estimates for B3 (lag) were 3.5 for the modified method compared with 4.5 for the traditional method. This technique works well when using the SAS PROC NLIN procedure but can be modified to work with other statistical packages.

Models, Statistical↗

PubMed2003

Evaluation of low-phytate corn and barley on broiler chick performance.

Grains produced by low-phytate barley and corn isolines homozygous for each species' respective low phytic acid 1-1 allele were compared to grain produced by near-isogenic normal or wild-type barley and corn in broiler chick feeds. Cobb x Cobb (384) chicks were used in a 10-d study. A randomized complete block design with a factorial arrangement of 2 x 2 x 3 was used with 4 replicates (8 chicks / replicate) per treatment. Twelve isocaloric and isonitrogenous treatment diets were formulated to contain 2 types of grain (barley and corn), 2 levels of grain (40% and 60%), and 3 sources of available P (wild-type grain, wild-type P-supplemented grain, and low-phytate grain). Growth parameters, bone parameters, total bone mineral, and apparent digestibilities were measured. The mean growth and bone responses were 1) higher for barley diets compared to corn diets, 2) higher for 60% grain inclusion compared to 40%, 3) higher for low-phytate compared to wild-type grains, and 4) not different for low-phytate compared to P-supplemented wild-type grain diets. Chicks fed low-phytate-based diets excreted 33 and 43% less P than chicks fed wild-type and P-supplemented wild-type diets, respectively. Correlations between percentage bone ash, total bone ash, and bone strength indicated a strong relationship and appear to support the use of bone strength analysis as a simpler method than ash content determination as an indication of P status. Feeding low-phytate grains will reduce the need for supplemental P in chick diets.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Oyster mushroom cultivation with rice and wheat straw.

Cultivation of the oyster mushroom, Pleurotus sajor-caju, on rice and wheat straw without nutrient supplementation was investigated. The effects of straw size reduction method and particle size, spawn inoculation level, and type of substrate (rice straw versus wheat straw) on mushroom yield, biological efficiency, bioconversion efficiency, and substrate degradation were determined. Two size reduction methods, grinding and chopping, were compared. The ground straw yielded higher mushroom growth rate and yield than the chopped straw. The growth cycles of mushrooms with the ground substrate were five days shorter than with the chopped straw for a similar particle size. However, it was found that when the straw was ground into particles that were too small, the mushroom yield decreased. With the three spawn levels tested (12%, 16% and 18%), the 12% level resulted in significantly lower mushroom yield than the other two levels. Comparing rice straw with wheat straw, rice straw yielded about 10% more mushrooms than wheat straw under the same cultivation conditions. The dry matter loss of the substrate after mushroom growth varied from 30.1% to 44.3%. The straw fiber remaining after fungal utilization was not as degradable as the original straw fiber, indicating that the fungal fermentation did not improve the feed value of the straw.

Agaricales↗

PubMed1998

Influence of processed corn grain in diets of dairy cows on digestion of nutrients and milk composition.

Five primiparous Holstein cows (55 d in milk) that were fitted with ruminal and duodenal cannulas were used in a 4 x 5 incomplete Latin square to determine the effects of blends of steam-flaked and dry-rolled corn on site and extent of nutrient digestion and milk yield and composition. Diets were fed as total mixed rations and consisted of 45% forage and 55% concentrate; each diet contained 27% corn grain. Dietary treatments were composed of blends of dry-rolled and steam-flaked corn in ratios of 100:0, 67:33, 33:67, and 0:100. Intake of dry matter; digestibilities of dry matter, organic matter, acid detergent fiber, cellulose, neutral detergent fiber, fatty acids, and N; and microbial efficiency were unaffected by diet. Ruminal, postruminal, and total tract digestion of starch increased linearly, and starch passage to the duodenum decreased linearly, as the proportion of dry-rolled corn in the diet decreased. Ruminal propionate and valerate increased linearly, and acetate, butyrate, isovalerate, and the acetate to propionate ratio decreased linearly, as proportions of dry-rolled corn in the diet decreased; however, no changes in total volatile fatty acid concentrations in ruminal fluid were observed. Ruminal fluid pH was similar across diets. A decrease in dry-rolled corn decreased ruminal ammonia N and plasma urea N linearly. Milk yield and composition, as well as milk N fractions, were similar across diets. Although changes in fatty acid composition of milk fat were small, linear decreases in percentages of trans-C16:1 and cis-9- and cis-10-C18:1, as well as a linear increase in the percentage of C18:2 occurred as the proportion of dry-rolled corn in the diet decreased. An increased proportion of dry-rolled corn in the diet decreased digestion of starch in the rumen, and patterns of volatile fatty acid concentrations shifted accordingly. However, no effects on lactational parameters were observed.

Ammonia↗

PubMed1998

Ash content of detergent fibers in feeds, digesta, and feces and its relevance in fiber digestibility calculations.

The influence of insoluble ash in diet, digesta, and fecal samples was evaluated. Ash-free values of neutral detergent fiber (NDF) and acid detergent fiber (ADF) for feed, digesta, and fecal samples were compared with uncorrected values of NDF and ADF in two digestibility experiments. Six feed samples were selected at random along with four duodenal and two fecal samples; the latter two were a part of two digestion studies. The silica composition of feed samples was low with the exception of oat hay and rice straw. Ash-free values of NDF and ADF for digesta and fecal samples were lower than uncorrected values of NDF and ADF, and silica accounted for the majority of the differences. The use of ash-free values of NDF and ADF in both digestibility experiments with dairy cows resulted in more realistic digestibility estimates and reduced the amount of variability associated with the calculation of the digestibility of NDF and ADF in the rumen and total digestive tract. The source of the insoluble ash was not identified but could have come from individual feedstuffs or the consumption of sand. Sample contamination by silica and other ash components may influence NDF and ADF composition if the fiber residues are not ashed prior to calculation of NDF and ADF.

Animal Feed↗

PubMed1997

Effects on nutrient digestion of wheat processing and methods of tallow addition to the diets of lactating dairy cows.

Five multiparous Holstein cows in midlactation that were fitted with ruminal and duodenal cannulas were used in a 3 x 5 incomplete Latin square. The objective of this study was to examine the effects on nutrient digestion of wheat processing and method of tallow addition to the diets of lactating dairy cows. Diets consisted of 45% forage and 55% concentrate, and each diet contained 20% wheat and 2% tallow (as-fed basis). Treatments were dry-rolled wheat with tallow added to the concentrate, steam-rolled wheat with tallow added to the concentrate, and steam-rolled wheat with tallow added first to the wheat. The dry matter intake; digestion of starch, fiber, and fatty acids; ammonia N concentration; and molar proportions of volatile fatty acids in ruminal fluid were not affected by treatments. The apparent digestibility in the total tract of organic matter and nitrogenous compounds was significantly higher for the steam-rolled treatment with tallow added first to the wheat. Mean ruminal fluid pH was similar across treatments; however, cows fed the diet containing steam-rolled wheat with tallow added first to the wheat had the smallest pH change from 0 to 2 h postfeeding. Milk yield did not differ, regardless of cow diet. Method of tallow addition had marked effects on the apparent digestibility of organic matter and N in the total tract of lactating dairy cows.

Animal Nutritional Physiological Phenomena↗

PubMed1997

Effects of corn processing on the site and extent of digestion in lactating cows.

Three multiparous Holstein cows in midlactation were fitted with ruminal and duodenal cannulas. Cows were used in an experiment with a 3 x 3 Latin square design to study the effect of corn processing on nutrient flow from the rumen to the duodenum and on ruminal fermentation in lactating cows. Cows were fed diets consisting of 40% forage and 60% concentrate. The only difference in dietary ingredients was the type of processed corn included at 24% of the total diet (as-fed basis). Treatments were dry-rolled corn with a bulk density of 0.54 kg/L and steam-flaked corn with a bulk density of either 0.39 kg/L or 0.31 kg/L. Ruminal fluid pH was not affected by corn processing, but steam-flaking decreased the molar percentage of acetate and increased the molar percentage of propionate. Digestibility of starch in the rumen was not affected by processing. Digestibility of starch entering the duodenum as well as apparent digestibility of starch in the total tract were increased by steam-flaking. Flow of feed and microbial N from the rumen and microbial N efficiency were not affected by grain processing. Yields of milk and milk components as well as composition of milk were not affected by grain processing.

Animal Feed↗

PubMed1995

Quantity and economic importance of nine selected by-products used in California dairy rations.

Food processing representatives, brokers, nutritionists, livestock producers, and trade associations were surveyed to quantify 9 by-products used for feeding livestock during 1992 in California. The commodities were almond hulls, dried beet pulp, wet brewers grains, wet citrus pulp, pressed citrus pulp, wet corn gluten feed, corn gluten meal, whole cottonseed, and rice bran. The 9 by-products contributed over 2.5 million tonnes and about 27% of the total feed concentrate moved within California during 1992. Market value of these 9 by-products was almost .25 billion dollars. Whole cottonseed accounted for about 31% of the total tonnage of these 9 by-products and provided about 66% of the total CP and 53% of the total NEL of these 9 by-products. The by-products were more valuable as energy sources than CP sources compared with NEL from corn and CP from soybean meal, respectively. Calculations of milk production, based on the CP content or NEL content of the by-products, showed that these 9 by-products could have contributed sufficient CP or NEL for over 31% of the milk produced in California during 1992. Ration formulations demonstrated that the economic value of by-products changed with feedstuffs available and, in general, would be used in rations over a range of market prices.

Animal Feed↗

PubMed1992

In vitro buffering capacity changes of seven commodities under controlled moisture and heating conditions.

Effects of adding 0 or .25 g of water/g of feed and heating for 0, 20, or 40 h at 100 degrees C on buffering capacity of beet pulp, almond hulls, alfalfa hay, oat hay, wheat bran, oat bran, and barley were determined in vitro. Feeds were examined for ash, N, NDF, ADF, acid detergent lignin, total buffering capacity (pH 4 to 9), and physiological buffering capacity (pH 5.5 to 7). Minerals were measured at 0 g of water/g of feed, 0 h of heat and at .25 g of water/g of feed, 40 h of heat; differences were negligible. Total buffering capacity was high for alfalfa, oat hay, and almond hulls; low for barley and oat bran; and intermediate for beet pulp and wheat bran. Physiological buffering capacity was consistently lower than total buffering capacity, but differences varied among and within feeds. Moisture had little effect on buffering capacity, NDF, ADF, or lignin. Time of heating had a significant effect on buffering capacity, NDF, ADF, and lignin but not on N or ash. Heating increased buffering capacity in most cases. Lignin was a poorer predictor of buffering capacity than total ash across feeds but a better predictor within feed across treatments. Large errors could occur when using total ash to predict buffering capacity for feeds subjected to heat.

Animal Feed↗

PubMed1992

Application of theoretically optimal sampling schedule designs for fiber digestion estimation in sacco.

Three different geometrically spaced sampling schedule designs, a theoretically optimal design, and a design that included all sampling times were evaluated by comparing parameter estimates, half-life, R2, and an indicator of variance-covariance space. Alfalfa and oat hays were tested using nylon bags placed in the rumen of a fistulated, non-lactating cow, and the amount of NDF remaining was measured at specified times. Parameters were estimated from f(t, phi) = Ae-K(t-lag) + U, where f (t, phi) = NDF at time t (h), A = degradable NDF, U = undegradable NDF, lag = time before digestion, and K = rate constant (h). A, U, and f(t, phi) are expressed as a fraction of DM at time 0. Estimates A and U did not fluctuate, whereas K and lag varied across designs. All R2 were over .96 and did not vary across designs. Comparison of designs that had the same number of observations showed that the indicator of the variance-covariance space was statistically similar across designs, although the optimal design was ranked best. Parameter estimates were similar when using different sampling schedule designs, but some estimates differed by 29%. The optimal design sampling schedule provided sufficient information to estimate parameters without loss of accuracy when compared with other designs.

Animal Feed↗

PubMed1991

The use of integer programming in dairy sire selection.

A computerized sire selection integer program, IPSIRE, was developed to test the optimality of solutions obtained by using MAXBULL, a popular computerized sire selection aid. The IPSIRE program uses an optimization software package and a compatible spreadsheet; MAXBULL uses linear programming techniques. The computer programs were compared using large and small data sets. Multiple combinations were run, varying the levels requested for PD fat percentage, PD type, and price paid per unit of semen. All other constraints were held constant. The objective function for all combinations maximized PD milk. The IPSIRE program exceeded MAXBULL by an average of $2.5 for PD dollars and 7.3 kg (16.1 lb) for PD milk using the small bull data base. Sire averages for traits PD type, PD fat percentage, and price paid were not different between the two programs. Similar trends were seen using the large bull data base. The IPSIRE program exceeded MAXBULL by an average of $1.2 for PD dollars and 4.1 kg (9.0 lb) for PD milk, whereas sire averages for PD fat percentage, PD type, and price paid were not different between programs. The goal for PD type had the least influence of the three goals on sire averages for PD milk. The goal for price paid had the greatest impact on realized PD milk; higher goals for price paid produced solutions with higher values for realized PD milk. The IPSIRE program required longer computational times for finding solutions that maximized PD milk than MAXBULL.

Animals↗

PubMed1989

Effects of baking hulless barley on the digestibility of dietary components as measured at the ileum and in the feces in pigs.

The effects of different baking conditions on the apparent digestibility of dietary components were examined in pigs with an ileal cannula. The pigs were fed a hulless barley-based diet that was 1) uncooked, 2) baked for 4 h using high moisture, low temperature (37% dry matter, 121 degrees C) conditions (HMLT), or 3) baked for 1 h using lower moisture, high temperature (48% dry matter, 204 degrees C) conditions (LMHT). Ileal digesta and fecal dry matter were not different between the three diets. Pigs fed the HMLT and LMHT diets had 4% and 2% higher starch digestibility at the ileum, respectively, than did pigs fed the uncooked diet (P less than 0.05). Total Klason lignin recovered at the terminal ileum was similar for all diets even though initial Klason lignin values for the LMHT diet were twice that of the uncooked or HMLT diet. Digestibility of non-starch polysaccharides (NSP) as measured at the ileum and in the feces of pigs fed the baked diets was about 10% higher than in pigs fed the uncooked diet (P less than 0.1). The ratio of NSP ileal digestion:NSP digestion as measured in the feces was over 0.75 for all diets. Baking increased digestibility in the barley-based diet by increasing the digestibility of starch and dietary fiber. Increasing the severity of baking (LMHT) tended to decrease digestibility compared to the mild baking (HMLT), but not significantly.

Absorption↗

PubMed1989

Effect of pelleting and beta-glucanase supplementation on the ileal and fecal digestibility of a barley-based diet in the pig.

The influences of pelleting and beta-glucanase supplementation on the digestibility of dietary components in a barley-based diet were investigated in pigs fitted with cannulas in the terminal ileum. The diet contained 49.0% starch, 18.9% crude protein and 14.8% dietary fiber, with arabinoxylans (4.9%), mixed-linked beta-glucans (3.4%) and cellulose (3.3%) as the main fiber components. Pelleting increased mixed-linked beta-glucan solubility from 45 to 62%. Neither treatment influenced the ileal or fecal apparent digestibilities of dry matter (64 and 80%, respectively), energy (62 and 79%), crude protein (53 and 75%), crude fat (26 and 27%) or dietary fiber (58 and 72%). However, pelleting increased (P less than .01) the pre-ileal apparent digestibility of starch from 91.5 to 95.3% and decreased (P less than .03) that of ash from -10 to -23%, while increasing (P less than .005) the fecal apparent digestibility of starch from 98.6 to 99.7%. The solubility of mixed-linked beta-glucans in ileal digesta was lower (P less than .001) in pelleted (26%) than in unpelleted (58%) diets. beta-glucanase supplementation also increased (P less than .05) the ileal apparent digestibility of starch, from 92.6 to 94.3%, and of mixed-linked beta-glucans, from 95.7 to 97.1%. Significant between-pig differences in the apparent digestibility of dietary components were observed. In conclusion, treatments that disrupt the endosperm cell walls in barley can increase the proportion of the diet digested prior to the large intestine.

Animal Feed↗