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Biomedical subjects

S Leeson

Publications and source records attributed to S Leeson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Response of broiler breeders to low-protein diets. 1. Adult breeder performance.

Four hundred female and 50 male commercial strain breeders were reared separately from 1 d to 18 wk of age, with all birds receiving the same diet. At 18 wk, all pullets were weighed and the extreme weights removed from the group. The remaining hens were then randomly sorted into four treatment groups each represented by four replicate groups. Treatment involved feeding different levels of CP (16, 14, 12, and 10%), supplemented with synthetic lysine and methionine in order to maintain constant lysine and TSAA levels, respectively. Diets were isoenergetic and all birds received the same quantity of feed daily. Dietary protein had no effect on egg production (P > .05). However, breeders fed 10% CP were lighter (P < .01) in weight than birds fed 16% CP. Eggs from birds fed 10 and 12% CP were consistently smaller (P < .01), and this resulted in reduced chick weight at hatching. Low-protein diets also resulted in less nitrogen excretion. These data suggest that it is possible to reduce the CP intake of broiler breeders while maintaining intake of critical amino acids without affecting performance.

Amino Acids↗
PubMed1995

Response of broiler breeders to low-protein diets. 2. Offspring performance.

Broiler breeders were allocated at random to one of four experimental diets containing various levels of CP (16, 14, 12, or 10%), at constant methionine+cystine and lysine levels of .59 and .82%, respectively. Diets were isoenergetic and all birds received the same quantity of feed daily to 64 wk of age. Eggs from birds fed 10 and 12% CP were consistently smaller (P < .01) and in two trials involving breeders at 30 and 52 wk of age this resulted in reduced chick weight at hatching, although no lasting effect was observed on weight of offspring at 48 d. Better feed efficiency (P < .05) was observed from broilers hatched from hens fed lower CP diets. These data suggest that it is possible to reduce the CP intake of broiler breeders while maintaining intake of critical amino acids without adversely affecting offspring performance.

Animals↗
PubMed1995

Utilization of fats and fatty acids by turkey poults.

Two experiments were carried out with young, Large White male turkey poults maintained in either floor pens or metabolism cages. In Experiment 1, poults were fed isoenergetic diets containing either no supplemental fat, or 5% of either tallow, corn oil, soybean oil, animal-vegetable blend fat, or canola oil. Poults generally ate less of the fat-supplemented diets and showed improved feed utilization, although weight gain was little affected. There was improved fat retention when vegetable oils were used (P < .01) and this was reflected in a slight improvement in diet energy level (P > .05). Poults fed tallow or animal-vegetable blend fat also excreted most fat. Diet had no effect (P > .05) on apparent retention of calcium or phosphorus, although retention of magnesium was less with more saturated fats. In Experiment 2, poults were fed diets containing palmitic acid, oleic acid, or a 50:50 (wt/wt) mixture of these fatty acids. There was a reduction (P < .05) in apparent retention of nitrogen, magnesium, calcium, and fat for poults fed palmitic acid, oleic acid, or the mixture. Mixing palmitic acid with oleic acid corrected some of these problems. However, reduced mineral retention was not reflected in any change in levels of bone ash, calcium, or phosphorus. Feeding palmitic acid did result in the most dramatic reduction of bone magnesium content (P < .05). It is concluded that turkey poults, like chicks, are less able to digest saturated fatty acids, and that such undigested fats can lead to reduced retention of some minerals through increased soap formation. However, there is no direct evidence that such soap formation causes a major change in bone calcium or phosphorus content or in gross bone development or poult well-being.

Animals↗
PubMed1994

Effect of varying period of early nutrient restriction on growth compensation and carcass characteristics of male broilers.

An experiment was conducted to determine growth and carcass characteristics of male broilers subjected to varying periods of early nutrient restriction. Nutrient restriction was achieved by feeding a starter diet in which the major ingredients were replaced with 50% oat hulls. Five treatments involved feeding this diluted diet for 6 d, either continuous or split into shorter periods in different ways, all starting at 6 d of age. On completion of the 6 d of nutrient restriction, all birds received undiluted starter diet, followed by grower and finisher diets to trial termination at 49 d. All birds fed the diluted diet exhibited reduced nutrient intake. Complete growth compensation by all birds that previously received the diluted diet was attained by 35 d, due largely to their superior (P < .05) feed efficiencies relative to the control birds during realimentation. Varying the period of nutrient restriction did not affect growth compensation. Birds that received the diluted diet for 6 continuous d tended to be leaner at 42 d compared with those that consumed the diluted diet for shorter periods. This latter effect may relate to variable ME intake. There was no statistical difference in other carcass characteristics measured at both 42 and 49 d of age.

Animals↗
PubMed1994

Strain comparison of turkey egg components.

Two experiments were conducted to quantify the composition of turkey hatching eggs in relation to strain of bird and age of breeder. In one experiment, 20 Nicholas and British United Turkeys of America (BUTA) eggs produced at 3, 12, and 24 wk of production were examined for physical and chemical components. Eggs from Nicholas hens were always some 4 g heavier (P < .05) due essentially to a larger albumen content. Although absolute components increased over time (P < .05), there were few changes in proportional composition (P > .05). Eggs from BUTA turkeys initially contained more yolk protein (P < .05). At 12 and 24 wk of production, eggs from Nicholas hens changed most rapidly and at these ages contained more yolk protein than the BUTA strain eggs (P < .05). At the end of the production cycle, BUTA eggs contained less lipid and protein in the yolk (P < .05). For both strains there was an increase in stearic acid content of yolk lipid with increased breeder age. In a second experiment, comparable studies were conducted on eggs obtained from male and female line BUTA breeding stock. Although male line eggs were heavier (87 vs 78 g), the smaller female line eggs exhibited proportionally more yolk (P < .05), as absolute yolk weight was similar for both strains (22.4 vs 22.5 g). It was concluded that only minor differences exist in components of eggs from different turkey strains.

Age Factors↗
PubMed1994

Laying hen performance as influenced by protein intake to sixteen weeks of age and body weight at point of lay.

White Leghorn chicks were fed corn-soybean meal diets containing 20, 17, 14, and 11% protein, with similar levels of energy, from hatch to 16 wk of age. Body weights at 16 wk were similar for pullets fed the 20 and 17% protein diets, but were reduced by 11 and 27% for birds fed the 14 and 11% protein diets, respectively, as compared with the 20% protein diet. At 16 wk of age, all birds were placed on a common 17% protein laying diet. Pullets fed the 14 and 11% protein laying diets were slightly slower coming into production, however, by 28 wk of age egg production was similar for all four growing treatment groups and remained so until the end of the experiment. Average egg weight was similar for pullets fed the two higher levels of protein during the growing period and significantly lower for those pullets fed the 11% grower diet for all except the 28- and 32-wk periods. Pullets fed the 14% grower diet produced eggs with average weights significantly lower than those for the higher protein diets from 40 to 58 wk of age. Although the results might be interpreted as indicating that higher protein growing diets result in body protein reserves that subsequently enhance egg size, it is more likely that the pullets consuming lower protein diets produce smaller eggs because they have smaller body weights.

Age Factors↗
PubMed1994

Effect of early feed restriction and realimentation on heat production and changes in sizes of digestive organs of male broilers.

Two experiments were conducted with broilers to determine the effect of early feed restriction and realimentation on metabolic heat production and changes in sizes of digestive organs. An indirect open circuit calorimeter was used. Treatments were a full-fed control (FF) and a feed-restricted group (FR). Feed during the restriction period (6 to 12 d) for the FR birds was limited to 50% of voluntary feed intake of the FF birds. This was followed by realimentation period when all birds were provided feed for ad libitum consumption. The purpose of Experiment 1 was to measure basal metabolic rate (BMR), and Experiment 2 was designed to measure 36-h fasting metabolic rate (FMR), in both cases during time of restriction and realimentation. At the end of the 36-h unfed period, birds were killed and their digestive organs excised, blotted, and weighed. The FR birds showed significantly (P < .01) lower BMR compared with the FF birds during the restriction period. This lower BMR did not carry over into the refeeding period, when there was no difference between the two treatments. Thirty-six-hour FMR, like the BMR was also lower for FR compared with FF birds, but only during the period of restriction. Weights of digestive organs (expressed as a percentage of BW) during restriction were generally heavier for FR compared with FF birds. Measurements of organ weights taken during realimentation show significantly (P < .05) heavier liver and pancreas for FR compared with FF birds. Results of these experiments suggest that lower MR of "restricted-refed" birds does not play a role in the ability of the birds to show improved feed efficiency and growth compensation. Greater feed intake relative to BW and its associated digestive adaptations seem to be contributing factors to any growth compensation.

Animal Feed↗
PubMed1994

Predicting preterm delivery: the fetal fibronectin test.

Preterm labour and delivery is a major problem and the leading cause of perinatal death in the UK. At present it is virtually impossible for doctors and midwives to predict when preterm labour is about to start. A new test may help with this problem. It detects the presence of fetal fibronectin in the vagina, which may indicate that the cervix is preparing to begin labour. Although these are early days, the fibronectin test looks promising. It is suitable at present for high-risk patients. Further studies are needed before its use can be justified as a screening test for low-risk women.

Female↗
PubMed1992

Calcium and phosphorus metabolism and eggshell formation of hens fed different amounts of calcium.

Twenty-seven 42-wk-old Single Comb White Leghorn hens housed in separate cages were fed either 2.5, 3.5, or 4.5% Ca diets, each providing .45% available P. Birds were allowed a 7-day adaption period followed by an 8-day collection period. Feed and water were available for ad libitum consumption with feed intake recorded daily. Eggs and excreta were collected daily for mineral analysis. Feed, Ca, and P intake of hens increased significantly (P less than .05) on shell-forming (SF) days compared with days on which shell formation did not take place (NSF). Dietary Ca level had a significant (P less than .05) effect on feed and Ca intake of hens. On SF days, hens retained more dietary Ca, both as a percentage and per gram Ca basis, compared with NSF days. As dietary Ca increased, the percentage Ca retained decreased (P less than .05) and per gram Ca retained increased (P less than .05). Dietary Ca had no effect (P greater than .05) on egg weight or egg production. Increasing dietary Ca significantly (P less than .05) decreased shell deformation and increased (P less than .05) shell weight and grams of shell Ca, although there was no significant (P greater than .05) effect on percentage shell Ca. Calcium retention increased linearly (P less than .05) as Ca intake increased, and shell weight increased quadratically (P less than .05). There was a diminishing response of shell weight to Ca intake at higher levels.

Animals↗
PubMed1992

Calcium and phosphorus metabolism and eggshell thickness in laying hens producing thick or thin shells.

Two experiments were carried out to investigate the Ca and P metabolism of hens laying thick- (THK) or thin-shelled (THN) eggs on shell-forming days (SF) and days on which shell formation does not occur (NSF). In Experiment 1, 10 hens identified as producing THK or 10 hens producing THN eggs were offered a diet containing 3.5% Ca and .4% available P. Feed consumption, egg production, egg weight, egg deformation, and shell weight were recorded over 8 days. Shells and excreta were collected daily for Ca and P analysis. Feed, Ca, and P intake did not differ significantly (P greater than 0.5) between the two groups of hens, however, feed intake and Ca retention increased significantly (P less than .05) on SF compared with NSF days. The THK hens retained significantly (P less than .05) more Ca compared with THN hens. No differences (P greater than .05) were recorded for egg production, although there were differences (P less than .05) in egg weight and shell deformation between the two groups of hens. Increased egg weight did not account for differences (P less than .05) in eggshell deformation. Although percentage shell Ca was not significantly different (P greater than .05), total shell Ca was different (P less than .05) between the two groups. In Experiment 2, both groups of birds (THK and THN) were allowed simultaneous access to two different diets, a high-energy, high-protein diet low in Ca and P, and a low-energy, low-protein diet high in Ca and P.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of dietary calcium level on medullary bone calcium reserves and shell weight of Leghorn hens.

Two experiments were conducted to determine the effect of different levels of dietary Ca and subsequent feeding of a very low level of Ca on the medullary bone Ca reserves of laying hens. In Experiment 1, a total of 30 40-wk-old Single Comb White Leghorn hens were offered a diet with 2.5, 3.5, or 4.5% Ca for a period of 21 days with 10 birds per dietary treatment. On Day 21, five hens from each dietary treatment were euthanatized. The remaining birds were offered a .46% Ca diet for 5 days. In Experiment 2, 25 Single Comb White Leghorn hens were fed a 3.5% Ca diet for 21 days. Hens were then offered a .46% Ca diet and five hens euthanatized on Days 0, 2, 3, 5, and 7 of feeding the low-Ca diet. In Experiment 1, dietary Ca level had a significant (P less than .05) effect on total medullary Ca reserves of laying hens. Previous dietary Ca level had no significant (P greater than .05) effect upon medullary bone Ca reserves after subsequently feeding the low-Ca diet for 5 days. There was a (P less than .05) significant reduction in medullary bone Ca reserves of hens, regardless of previous level of calcium fed. In Experiment 2, feeding a low level of dietary Ca resulted in a significant (P less than .01) reduction in medullary bone Ca reserves of all bones measured, except the humerus. Although there was a significant (P less than .05) reduction in medullary bone Ca during the depletion period, hens appeared to make some attempt to conserve medullary bone Ca reserves.

Animals↗
PubMed1992

Measurement of metabolizable energy in poultry feeds by an in vitro system.

A two-stage in vitro system (IVDE) for estimating AMEn in poultry feeds was investigated. For 71 diets ranging from 2.2 to 3.4 kcal/g, the average AMEn was 2.889 kcal/g and the mean IVDE value was 3.005 kcal/g. From the 71 diets, 30 (42.2%) showed differences between AMEn and IVDE of less than .100 kcal/g and represented diets across the AMEn range of values. The statistical analysis of the data showed a standard error of the estimate (SEE) of .152 kcal/g for the 71 diets assayed. No clear differences in accuracy of AMEn among the diets, as related to the composition and proportion of ingredients, were observed. Thus, the IVDE method gave different AMEn for diets of similar composition. The application of the IVDE system to selected ingredients showed that the AMEn of corn was underestimated by the method. However the AMEn of roasted, extruded soybeans and oats was estimated accurately by the IVDE method. Other ingredients were greatly overestimated by the in vitro technique (soybean meal, corn gluten meal, and barley). The results of applying the IVDE method for estimating AMEn showed the limitations of this technique with regard to the universality of its application. Although the method was successful in estimating AMEn values of diets and ingredients, for many samples the IVDE technique did not give acceptable results.

Animal Feed↗
PubMed1992

Response of broilers to feed restriction or diet dilution in the finisher period.

Two experiments were conducted to study the response of 35- to 49-day-old male broilers to either feed restriction or diet dilution. In Experiment 1, after being fed conventional starter-grower diets to 35 days of age, birds consumed either a conventional finisher diet ad libitum, or 10, 20, 30, 40, or 50% less of this diet to 49 days of age. Performance and carcass characteristics were measured from 35 to 42 days and 42 to 49 days. There was a linear relationship between nutrient intake and 42- and 49-day body weight (P < .01). However, as a percentage of the control birds, weight gain was reduced less from 42 to 49 days (64%) than from 35 to 42 days (86%) for the 50% restricted group. Thus, there was apparently an adaptation in the period from 42 to 49 days. In a second comparable experiment, birds were offered a conventional finisher diet or one with either 10, 20, 30, 40, or 50% dilution with a 50:50 (wt:wt) mixture of sand:oat hulls. Growth rate was only slightly reduced, thus demonstrating the remarkable ability of the broilers at this age to increase feed intake in response to energy density of the diet. Although birds were of comparable weight, diet dilution resulted in a linear reduction in size of abdominal fat pad, whereas breast weight was not affected. The present data suggest that broiler chickens are far from eating to physical capacity, at 35 days of age, because they were able to exhibit up to a 70% increase in feed intake relative to the control birds.

Aging↗
PubMed1992

The effect of dietary sodium on right ventricular failure-induced ascites, gain and fat deposition in meat-type chickens.

Experiments were carried out using various levels of sodium (Na+) from NaCl or NaHCO3 to determine: 1) the level of Na+ required to induce ascites alone or in combination with cold temperature and 2) the effect of Na+ on weight gain and fat deposition in broiler chickens. In experiment 1, there were no cases of ascites using levels of Na+, from NaCl at 0.14% to 0.44% in the feed from day 3 or using added Na+, from NaCl at 0.0% to 0.12% in the water from day 3 with a level of 0.14% in the feed. There was no significant difference in 21 or 42 day body weight, feed conversion, or right ventricle:total ventricle (RV:TV) ratio between treatment groups. Day 3 to 4 body weight gains were significantly increased in all treatment groups with added Na+ (p less than 0.01). In experiment 2, with levels of added Na+, from NaCl, at 0.0% to 0.12% in the water with a level of 0.20% in the feed there were two cases of ascites, one at day 7 and one at day 40 at the 0.12% level. There were no significant differences in body weight at days 21 or 42 or in the RV:TV ratios between groups. Feed conversions were improved (p less than 0.01) with the lowest and highest levels of Na+ and a significant increase in day 3 to 4 body weight gain, with increasing Na+ in all treatment groups, was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1991

Research note: utility of the thiobarbituric acid test in the determination of the quality of fats and oils in feeds.

The TBA test is a rapid and simple method for determining the extent that a fat has degraded to non-metabolizable aldehydes, such as malondialdehyde. A fat that has a high peroxide number or high value in the TBA test would not be suitable for use in feeds because it would contain a high peroxide or aldehyde content. The digestibility of corn oil, poultry fat, and a commercial animal-vegetable blend incorporated into a basal diet were 91.0, 88.3, and 69.7% with metabolizable energy of 9.664, 9.020, and 5.961 kcal/g and transit times in the digestive tract of 173, 167, and 140 min, respectively. The commercial blend had the highest value in the TBA test and also had the highest level of lipid hydroperoxides and the lowest content of total fatty acids. In contrast, the corn oil had the lowest value in the TBA test, the lowest peroxide number, and the highest content of total fatty acids. The data suggest that the TBA test may be useful as an indication of the quality of fats and oils for use in feeds.

Animal Feed↗
PubMed1991

Response of laying hens to supplemental niacin.

Two experiments were conducted to investigate the effect of supplemental niacin on laying hen performance and liver fat and egg cholesterol content. In Experiment 1, 16 replicate groups of four adjacently caged birds were fed corn and soybean meal diets calculated to contain 22, 44, 66, or 132 mg supplemental niacin/kg (23.2, 38.7, 57.0, and 143 mg/kg niacin by analysis). Egg production, egg weight, feed intake, and eggshell quality were assessed each 28 days through a 364-day trial period. After 280 days, cholesterol content on three eggs per replicate was measured. At the end of the study, one bird per replicate was killed for subjective scoring of liver fat content. In Experiment 2, 24 birds from the control treatment (22 mg/kg supplemental niacin) of Experiment 1 were retained and fed for a subsequent 28-day period. Over this time, eight birds were each fed diets containing 22, 522, or 1,022 mg/kg supplemental niacin. Egg cholesterol content was measured in eggs collected on the last 3 days of the study. In Experiment 1, birds fed 66 or 132 mg/kg supplemental niacin/kg produced more eggs (P less than .05) than birds fed 22mg/kg. Niacin supplementation affected shell quality (P less than .05). Dietary niacin level had no effect on egg cholesterol content of liver lipid evaluation. In Experiment 2, supplementary niacin levels up to 1,022 mg/kg, which more closely stimulates therapeutic levels used for humans, again failed to affect egg cholesterol content.

Animal Feed↗
PubMed1991

Growth and development of Leghorn pullets subjected to abrupt changes in environmental temperature and dietary energy level.

Four trials were conducted to note the response of pullets to changes in environmental temperature and energy level at 56 days of age. In each trial, birds were fed diets providing either 2,500 or 3,000 kcal ME/kg throughout rearing, or with a single diet change from 2,500 to 3,000 and 3,000 to 2,500 kcal ME/kg occurring at 56 days. Each of the four diet scenarios was tested with six replicate caged groups each containing 10 pullets. In Trials 1 and 2 environmental temperature was maintained at 18 and 30 C, respectively, to 126 days. In Trials 3 and 4, temperature was changed at 56 days from 18 to 30 C and 30 to 18 C, respectively. Regardless of environmental temperature conditions, diet change per se had minimal effect on growth and development. Rather dietary energy level used from 56 to 126 days had the greatest effect on growth, with birds fed the highest energy content diet generally being heaviest. However, this effect was not significant (P greater than .05) in all trials, which is probably related to a lack of effect on energy intake under such conditions. Final body weight was more closely associated with energy intake than with protein intake and energy intake was maximized when high-energy diets were used after 56 days of age. Consumption of high-energy diets after 56 days, regardless of trial conditions, always resulted in increased carcass fat content at 126 days. It was concluded that abrupt and major changes in environmental temperature or dietary energy as used in these trials have little deleterious effect on pullet development. Conditions prevailing during later stages of growth have a far greater effect than changes per se in these parameters.

Animal Feed↗