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Biomedical subjects

T R Morris

Publications and source records attributed to T R Morris.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of protein concentration on responses to dietary lysine by chicks.

Chicks were fed on diets varying in crude protein (CP) content (140 to 280 g/kg diet) in either 8 steps, experiment 1, or 6 steps, experiment 2. Protein composition was held constant in each experiment. At each protein concentration, 5 (experiment 1) or 6 (experiment 2) concentrations of lysine were tested, ranging from 40 to 60 g/kg CP. Growth rate and efficiency of food utilisation to 21 d of age responded to increasing dietary protein contents up to about 230 g CP/kg. An estimate of lysine requirement at each protein concentration was obtained by fitting a quadratic curve to the response data and calculating the dose of lysine (g/kg CP) needed to maximise either growth rate or gain/food ratio. Although no growth response to dietary protein was obtained between 240 and 280 g CP/kg, the amount of lysine needed to maximise growth and gain/food ratio over this range increased systematically when expressed as g/kg diet, but remained constant if expressed as g/kg CP. The regression of lysine required (g/kg diet) for maximum performance (growth or food efficiency) on CP (g/kg diet) was strictly linear for both responses in both experiments throughout the entire range studied (140 g CP/kg to 280 g CP/kg). The estimated lysine requirement was 0.053 of the CP in experiment 1 and 0.055 of the CP in experiment 2. It is concluded that a fixed ratio of lysine to protein should be specified in practical diet formulation, rather than a minimum dietary concentration of lysine. This would ensure that, if the dietary protein content rises above a prescribed minimum value in least-cost formulation, an appropriate adjustment will automatically be made to the lysine content of the solution.

Animals↗
PubMed1987

Effects of constant environmental temperatures on the performance of laying pullets.

1. Two experiments are described in which laying pullets maintained at constant temperatures were fed a range of diets with a view to defining optimum combinations of temperature and nutrient intake. 2. In the first experiment, all combinations of 6 temperatures (15 degrees, 18 degrees, 21 degrees, 24 degrees, 27 degrees and 30 degrees C) 9 diets (three protein concentrations and three energy contents) and two stocks were tested for 34 weeks using 4320 pullets. In experiment 2, all combinations of three rearing temperatures, three laying temperatures (18 degrees, 22.5 degrees and 27 degrees C) three diets (protein concentration) and two stocks were tested for 61 weeks using 2160 pullets. 3. As anticipated, higher dietary protein concentrations were needed to maintain egg output at higher temperatures. If diets suplying adequate amino acid intakes were provided, egg output was unaffected by temperatures in the range 15 degrees to 27 degrees C although, at the highest temperature, egg weight was slightly reduced and rate of lay (particularly in the later part of the laying year) was increased. At 30 degrees C, egg output was depressed whichever diet was fed. 4. Dietary energy content had small but significant effects on egg weight and egg output but did not interact with temperature. It was not possible to maintain egg weight or egg output at 30 degrees C by feeding a high energy, high protein diet. 5. Estimated heat output of the birds increased during the course of the experiment at the lower temperatures but decreased with time at 30 degrees C. Feather loss occurred earlier at the lower temperatures and this is interpreted as an effect of temperature on the timing of the annual moult, which also accounts for the better persistency of lay observed at 27 degrees C.

Animals↗
PubMed1987

Effect of dietary energy concentration on the response of laying hens to amino acids.

1. A hypothesis, that the optimum amino acid concentration in the diet is not directly proportional to the dietary energy concentration, but changes in inverse proportion to the change in food intake resulting from a change in energy concentration, was tested in three experiments. 2. Response experiments involving the amino acids methionine, lysine and isoleucine were conducted, in each case at three dietary energy concentrations, using a diet dilution and blending technique, thereby ensuring a constant ratio between background amino acids and the first-limiting amino acid in all diets, and also keeping the ratio of amino acids to energy constant as energy varied. 3. A common response curve relating egg output (g/bird d) to amino acid intake (mg/bird d) for each amino acid, fitted by means of the Reading Model, adequately described the response at each of the dietary energy contents. This implies that energy does not influence egg output directly, but only indirectly through its effect on food intake and hence on amino acid intake. 4. Both amino acid and energy concentration significantly influenced food intake. Energy intake was not constant over all dietary energy concentrations, being lower at low energy levels and higher at high energy concentrations. 5. It is concluded that amino acid requirements should not be stated either as percentages or as ratios with energy. Optimum amino acid intakes and energy concentrations should be calculated; the expected food intake should then be predicted, after which the appropriate concentration of nutrients in the diet can be determined.

Amino Acids↗
PubMed1987

Quantitative review of the effects of environmental temperature on food intake, egg output and energy balance in laying pullets.

1. Data from 30 published experiments have been analysed to examine the relationships between environmental temperature and the long-term, adapted responses of laying pullets, measured as metabolisable energy intake, egg output and body weight change. Heat production was also estimated indirectly from the other three variables. 2. The majority of experiments employed White Leghorns, but there were 8 large trials in which brown crossbred pullets had been compared directly with White Leghorns. These trials were used to estimate differences in energy intake and heat output between brown and white birds. 3. A total of over 26,000 birds was involved in the analysis. Individual trials varied in scale from 9 birds to 2,280 birds per treatment and in duration from 8 to 61 weeks. The constant temperatures investigated ranged from 10 degrees C to 34 degrees C, but there were no data for brown pullets beyond 30 degrees C. 4. The relationship between temperature and metabolisable energy intake is curvilinear, with food intake declining more steeply as ambient temperature approaches body temperature. Adapted heat production per bird is also a curvilinear function of temperature, tending towards a value of zero when extrapolated to the point at which ambient temperature equals normal body temperature. However no satisfactory data are available for fully adapted responses in the range 34 to 42 degrees C because egg production declines continuously when these temperatures are maintained for long periods. 5. When energy intake and heat output are expressed as functions of metabolic body size (kg 0.75) they can be represented as linear functions of temperature within the range 15 to 30 degrees C, but the slope must change outside this range. 6. It is calculated that the energy available for production is at a maximum at 23 degrees C for brown birds and at 24 degrees C for White Leghorns. Gross energetic efficiency is at a maximum at 30 degrees C, but egg output is reduced at this temperature. The optimum operating temperature for laying houses will depend upon the local cost of modifying ambient temperature and on the cost of supplying diets of appropriate protein content.

Animals↗
PubMed1987

The effect of carbimazole on growth and sexual maturity in the pullet.

Carbimazole (100 mg/kg diet) was fed to pullets from 8 to 12 or from 12 to 16 weeks of age. Pullets fed carbimazole from 8 to 12 weeks of age matured about 12 d earlier and produced more eggs between 17 and 22 weeks of age. Their body weights and feed intake were significantly lower than those of normal birds. Feeding carbimazole from 12 to 16 weeks of age had no significant effect on the birds except during the course of treatment where their feed consumption was less than that of the controls.

Animals↗
PubMed1985

Evaluation of a diet dilution technique for measuring the response of broiler chickens to increasing concentrations of lysine.

Three experiments were conducted on male broiler chickens between one and three weeks of age to determine their response to dietary lysine concentrations. Serial dilutions of a summit diet shown to be first-limiting in lysine were fed in all experiments. The balance between amino acids in these diets was maintained within narrow limits. Intake of the most-limiting amino acid was the most important factor determining growth rate; protein intake as such was of little or no importance. The efficiency of utilisation of dietary lysine for protein growth was calculated to be 65.05 mg/g protein gain, representing a net efficiency of 0.85. The diet dilution technique overcomes the major disadvantage of the graded supplementation method for determining the requirements of amino acids, namely that of the amino acid balance changing systematically in successive dietary treatments.

Animal Feed↗
PubMed1985

Quantitative review of optimum amino acid intakes for young laying pullets.

Data relating egg output to daily intakes of lysine, methionine, tryptophan, isoleucine and valine have been analysed using both published and unpublished sources. Amino acid requirements in mg/d for individual pullets were estimated by the following equations: (Table: see text) where E = egg output in g/d and W = body weight in kg. Response curves for flocks of pullets were calculated using the Reading model and optimum intakes were derived for various body weights, egg outputs and ratios of input costs to output values. Estimates of amino acid maintenance requirements were related to reported values for the adult cockerel and the amino acid requirement for egg output was related to the digestibility of amino acids and the composition of egg protein. Procedures are suggested for deriving response coefficients for other essential amino acids.

Amino Acids↗
PubMed1982

Concentrations of luteinizing hormone and progesterone in plasma during sexual development of the Khaki Campbell duck.

Concentrations of LH and progesterone were measured in the plasma of ducks which were, from 3 weeks of age, raised on either a constant photoperiod of 16 h light: 8 h darkness or a lighting schedule which stimulated natural changes in daylength. In ducks raised on a constant photoperiod of 16 h light: 8 h darkness the plasma concentration of LH increased steeply between 7 and 3.5 weeks before the onset of lay. Concentrations of LH then declined, gradually at first, but them rapidly during the 7 days before the first oviposition in association with a pronounced increase in the plasma concentration of progesterone. During the 18 days before the first egg was laid there was a significant (P less than 0.01) negative correlation between the plasma concentrations of LH and progesterone. The patterns of LH release during sexual development of ducks raised on a schedule which stimulated natural changes in daylength were variable but could be categorized according to the daylength at which each duck came into lay. In ducks coming into lay soon after the winter solstice when daylength was short (8.0-8.5 h light/day) there was a pronounced 15-fold prepubertal increase in the plasma concentration of LH although in some ducks high LH levels were not maintained until 3-4 weeks before the first oviposition and were not always followed by a rise in the plasma concentration of progesterone. In contrast, in ducks coming into lay when daylength had increased to 11.0-11.5 h light/day there were only minor fluctuations in the plasma concentration of LH until a small two- to threefold increase in LH was observed during the 2 weeks before the first oviposition.

Animals↗
PubMed1979

Toxicity of shoti (Indian arrowroot: Curcuma zedoaria) for rats and chicks.

1. A flour was prepared from rhizomes of shoti(Curcuma zedoaria) in such a way that most of the protein was retained. The crude protein (nitrogen x 6.25) content in this product was 155 g/kg, compared with approximately 10 g/kg in commercial shoti flour. 2. The high-protein flour proved highly toxic to 5-week-old rats and caused 100% mortality within 6 d when given at 320 g/kg diet. 3. Fresh rhizomes were minced and dried, and the resulting meal was given to weanling rats at 400 g/kg diet. All the animals lost weight rapidly, and two of the five rats died within 4 d. 4. This same shoti meal was given to 1-d-old chicks at 100 and 200 g/kg diet. All the chicks survived the test period (20 d), but body-weight, food intake and efficiency of food conversion decreased with increase in the level of shoti meal in the diet. 5. The traditional method of preparing shoti involves prolonged washing in changes of water, which removes most of the protein and other water-soluble nutrients and, presumably, a toxic constituent. Further investigation is needed to identify the toxic principle, and to discover a less wasteful procedure for removing it.

Amino Acids↗
PubMed1978

The photoperiodic effect of ahemeral light-dark cycles which entrain circadian rhythms.

1. A 27-h cycle of light and dark provides a greater gonadotrophic stimulus to the laying fowl, as judged by sexual maturity and rate of lay, than a 24-h cycle incorporating the same photoperiod. 2. An hypothesis put forward to account for these effects states that Effective Photoperiod equal p + c - b, where p = actual photoperiod, c = cycle length and b = the period of the endogenous biological clock. 3. Two experiments designed to test this hypothesis have yielded results which are consistent with it. 4. A poultryman who use an ahemeral cycle to alter egg weight or shell thickness and then whishes to transfer his flock back to a 24-h cycle should calculate the difference between the two cycle lengths and then add this quantity to the prevailing photoperiod to find the appropriate amount of light to be used in the 24-h cycle.

Animals↗
PubMed1978

Entrainment of oviposition in the fowl using light-dark cycles.

1. Fourteen experiments were performed to determine the minimum photoperiod and minimum scotoperiod needed for entrainment of oviposition in hens exposed to 21-h, 24-h and 30-h cycles. Entrainment was measured by the proportion of total eggs laid in a modal 8-h segment of each cycle. 2. In a 24-h light and dark cycle, a 15-min photoperiod or a 5-h scotoperiod produced essentially the same degree of entrainment as 6 h light, 18 h darkness (6L : 18D) or 14L : 10D, which were used as control treatments. Under 21-h light and dark cycles a minimum 3-h photoperiod or a minimum 9-h scotoperiod was needed to achieve full phase setting. When the cycle length was increased to 30 h a minimum 8-h photoperiod or a minimum 12-h scotoperiod was required for full entrainment. 3. This study demonstrates that photoperiod is a stronger signal than scotoperiod for the purpose of phase setting oviposition. It also shows that a stronger signal is required to achieve entrainment when the length of the light-dark cycle is several hours shorter or longer than the natural period of 24 h.

Animals↗
PubMed1978

Entrainment of oviposition in the fowl using bright and dim light cycles.

1. Nine short trial, involving 96 different treatments, were used to investigate the critical intensities and duration of bright and dim periods of lighting needed to entrain oviposition in cycles ranging from 21 to 30 h. 2. Entrainment was shown to depend upon the contrast between bright and dim lighting, and to be independent of the absolute light intensity. 3. A bright: dim ratio of 13:1 fully entrained oviposition in cycles of 25 h and 27 h. For 23-h and 28-h cycles a 30:1 ratio was required. Twenty-one-hour cycles required a ratio of 300:1 and with 30-h cycles a ratio of 1000:1 was needed to achieve full entrainment of oviposition. 4. In 24-h cycles, 1 h of bright lighting at 02.00 h was sufficient to override other environmental signals and cause eggs to be laid in the late evening, but a minimum bright period of 6 h was needed to cause full phase setting with 21-h cycles. 5. Circadian periodicity can easily be imposed on hens by providing a short exposure to bright light with a background of continuous dim light; but the signal must be increased (by providing a greater contrast between bright and dim lights and/or a longer period of bright lighting) to entrain oviposition when the cycle deviates markedly from the natural period of 24 h.

Animals↗
PubMed1978

The relative importance of sunrise and sunset for entrainment of oviposition in the fowl.

1. A series of four "sunset" signals, without associated sunrises, was given to laying hens by reducing light intensity in steps from 190 lx to 63, 21, 7 and 2 lx at 24-h intervals. Four "sunrises" were given by reversing the process. Treatments involving single "sunrises", single "sunsets" and combinations of sunrises and sunsets at 12-h intervals were also tested. 2. Only treatments which included one or more sunset signals were found to give full entrainment of oviposition, as judged by the proportion of eggs laid in a modal 8-h segment of each 24-h cycle. Full entrainment was achieved if the sunset occurred between 16.00 h and midnight, but not if the sunset occurred in the morning hours. Treatments involving only sunrise signals did not fully entrain oviposition but did have effect on the timing and distribution of ovipositions. Sunrises given in association with sunsets increased the degree of entrainment achieved, as compared with the sunset signal alone. 3. This study indicates that sunset is a potent synchronising agent for phase setting oviposition and, presumably, for phase setting the endogenous circadian rhythm of the fowl. Sunrise can also exert a modifying influence.

Animals↗
PubMed1978

The tryptophan requirements of young laying pullets.

Two experiments were conducted with laying pullets between 32 and 47 weeks of age. In each trial 1728 White Leghorn and 1728 cross-bred pullets were used. A series of diets of increasing protein content was offered. Protein quality was identical in all diets and tryptophan was demonstrated to be the most limiting amino acid in the protein mixture used. The daily tryptophan requirement of the individual pullet was estimated, by indirect methods, to be 2.25 mg/g egg output plus 10.25 mg/kg body weight. Response curves for flocks of pullets are illustrated. Calculated optimum intakes of tryptophan for various ratios of costs of input to value of output are tabulated. It is estimated that for a flock of mean body weight 1.5 kg, producing 55 g egg mass/hen d and consuming 110 g food/hen d, the optimum dietary tryptophan concentration is 1.7 g/kg when the marginal cost of supplying 1 kg tryptophan is 20 times the marginal value of 1 kg egg output.

Animals↗
PubMed1978

Effects of age on the tryptophan requirement of laying hens.

White Leghorn pullets which had been used for an assay of tryptophan requirement between 32 and 40 weeks of age were used for similar determinations between 63 and 73 and, after a moult, from 97 to 106 weeks of age. A tryptophan-limiting protein mixture was used and by dilution seven dietary protein contents were produced, supplying from 0.84 to 1.92 g tryptophan/kg diet. The diet of lowest protein content was also supplemented with free tryptophan. These diets were fed in experiments using 24 groups of 72 pullets at 63 to 73 weeks and 45 groups of 21 hens at 97 to 106 weeks. The relationship between egg output and tryptophan intake was the same in moulted hens as in young pullets, but pullets of 63 to 73 weeks of age yielded a different response curve; more tryptophan being needed for a given egg output. It is concluded that tryptophan required, per day, does not decrease during the first laying year, despite a decrease in rate of egg output.

Age Factors↗
PubMed1977

The relative importance of light and temperature as phase setting signals for oviposition in the fowl.

Under continuous lighting, time of oviposition was controlled by a temperature cycle (12 h at 30 degrees C and 12 h at 20 degrees C). The peak of egg laying occurred 15 h after the beginning of the cool period, which is the same interval as the interval observed between lights-out and peak egg laying under a 12L:12D lighting schedule. 2. When the temperature cycle was set 12 h out of phase with a light-dark cycle (12L:12D; temperature reduced when the lights came on), oviposition was entrained by the light-dark cycle. 3. When a temperature cycle was set 6 h in advance or 6 h in arrears of a 12L:12D cycle there was a difference of 1-4 h in mean time of lay between the two treatments, indicating that temperature can have a significant, though subsidiary, effect on oviposition time in the presence of a clear light-dark signal. 4. When the light-dark signal was reduced to 22L:2D, oviposition time was controlled by the temperature cycle. With 20L:4D oviposition time was determined principally by the photoperiod, but with a subsidiary effect due to temperature.

Animals↗