Biomedical subjects

T R Morris

Publications and source records attributed to T R Morris.

At least 37 records · Page 2Linked to original sources

PubMed1995

Effect of photoperiod on the mean oviposition time of two breeds of laying hen.

1. Oviposition times were recorded for brown and white egg-laying hybrids under 8, 10, 13 and 18 h photoperiods. 2. Mean oviposition time for both breeds was advanced relative to dusk by approximately 0.5 h for each 1 h extension of photoperiod. 3. Mean oviposition time for the brown egg hybrid was 1.2 to 1.4 h earlier than that of the white egg hybrid under each lighting regimen. 4. A genetic difference in phase setting of the Open Period for Luteinising Hormone (LH) release is the likely reason for the difference in mean time of lay of the two breeds. The difference is possibly one between brown and white hybrids generally, rather than between the particular varieties of hen used in this trial. 5. The proportion of the day in which eggs are laid is shorter under long photoperiods presumably because light at the end of the photoperiod inhibits the pre-ovulatory surge of LH.

Animals↗

PubMed1995

New intermittent lighting programme (the Reading system) for laying pullets.

1. Two intermittent lighting systems for laying hens are: the Biomittent system, using an asymmetric pattern of 0.25L:0.75D for 16 h followed by 8D, which entrains oviposition to 24 h cycles and, compared with standard lighting programmes, gives the same egg number and egg size but a smaller feed cost, and a symmetrical system (4[3L:3D]) which allows intervals between ovipositions to stretch, giving bigger eggs with thicker shells, but yielding fewer eggs and achieving no saving in food intake. 2. A new system was devised to combine the increased egg size and shell thickness, characteristic of symmetrical intermittent lighting programmes, with the reduction in food intake which is a feature of programmes that reduce total activity time. The pattern tested was 24(0.25L:0.75D). 3. The results of 2 trials showed that this new system gives about 2% fewer eggs than conventional (Step Up) or Biomittent lighting with a 2% increase in mean egg size and a 3% improvement in shell thickness at the end of the laying year. Feed consumption with the new system was similar to that under Biomittent lighting and 6% lower than that recorded for Step Up lighting. 4. Mortality was lower with the new system than with Step Up lighting, but not significantly so. From the evidence of other trials it is argued that intermittent lighting programmes which provide less than 8 h total illumination in 24 h generally reduce laying house mortality and may be regarded as beneficial to the welfare of the hen.

Aging↗

PubMed1995

A test for photorefractoriness in high-producing stocks of laying pullets.

1. Pullets of 2 high-producing commercial stocks (both brown-egg layers) were exposed to 5 different lighting patterns between 18 and 72 weeks to test the hypothesis that photoperiods used in commercial lighting programmes early in the laying year may be unnecessarily long and, by accelerating the development of photorefractoriness, may contribute to the decline in egg production observed after the initial peak. Two rooms of 288 pullets were allocated to each treatment. 2. The rate of lay observed with a Step-Up treatment which gave increases in photoperiod from 8L:16D at 18 weeks to 15L:9D at 27 weeks of age was not significantly different from that of treatments which held the birds on 11L:13D during peak egg production but gave increments up to 15L:9D later in the laying year. 3. A control group maintained on 11L:13D from 20 to 72 weeks laid 295 eggs per bird housed and a further group held on 8L:16D from 0 to 72 weeks laid 284 eggs per bird. These yields were lower than the Step-Up treatment (299 eggs) but show the potential of modern hybrid stocks to lay prolifically even without light stimulation. 4. It is concluded that the stocks tested in this experiment showed no advantage when given lighting programmes in the first laying year which were designed to minimise the adverse effects of photorefractoriness.

Aging↗

PubMed1994

Effects of timing and size of daylength change on brown egg laying domestic hens: plasma luteinising hormone concentration and sexual maturity.

1. Brown egg laying pullets were transferred from an 8-h photoperiod to an 8-, 10-, 13- or 16-h photoperiod at 6, 9, 12, 15, 18 or 20.3 weeks of age. Plasma luteinising hormone (LH) concentrations were measured at transfer and 7 and 14 d afterwards. 2. Significant increases in plasma LH occurred following light stimulations at 6, 9 and 12 weeks of age. 3. Changes in LH concentration 7 d after a light increase from 8 h to 8, 10, 13, 16 h were highly correlated with photoperiod length at 9 and 12 weeks of age. 4. Changes in LH were generally poorly correlated with age at sexual maturity, although the reduced influence on age at first egg of a light increase given close to sexual maturity was reflected in minimal LH responses at 18 and 20.3 weeks.

Aging↗

PubMed1993

Influence of sequence length on the response to ahemeral lighting late in lay.

1. An experiment is described in which 96 individually-caged SCWL hens in two rooms were used to investigate the response to changing to a 28-h cycle using a reverse treatment design. 2. The application of the 28-h cycle did not affect mean rate of lay but increased mean egg weight and egg output. 3. Grouping the birds according to their preliminary sequence length yielded an interesting outcome. In both rooms, birds with short sequences (< or = 6 eggs) produced significantly more eggs under the 28-h cycle, while those with long sequences (> 6 eggs) produced marginally fewer eggs. The same trend was also evident with egg output. 4. Changing from 24-h to 28-h increased yolk and albumen weights as well as shell quality. However, relative to egg weight, no measurable effect was detected due to light cycle, age or sequence length on yolk and albumen weights. 5. The paper provides new evidence suggesting that long ahemeral cycles could be used to improve egg production as well as shell thickness in flocks with modest rates of lay.

Animals↗

PubMed1992

Effects of dietary protein concentration on the response of growing chicks to methionine.

1. Experiments were conducted independently at two stations to measure the requirement for methionine in chick diets with crude protein (CP) varying in 8 steps from 140 to 280 g/kg diet (experiment 1) or from 90 to 300 g/kg (experiment 2). 2. Protein composition was the same at all protein concentrations within a trial. The diet was designed to be first-limiting in methionine and DL-methionine was added to provide 5 ratios of methionine to CP at each protein concentration. 3. Methionine required for maximum growth rate or maximum efficiency of food utilisation was estimated at each protein concentration by fitting a quadratic regression equation to the relevant data. The requirement was also estimated by fitting the Reading model to data for growth rate and methionine intake. 4. In both trials and by all three methods of estimation, the methionine requirement (g/kg diet) for maximum performance increased as a linear function of dietary CP concentration and nearly in direct proportion to CP. 5. It is concluded that diets which contain surplus protein, beyond that needed to maximise growth rate or food efficiency, need supplementation with methionine beyond that required when dietary protein is just adequate. A suitable rule for practical formulation is that methionine concentration in chick diets should be not less than 0.025 times the dietary CP concentration.

Animals↗

PubMed1991

Effects of dietary cottonseed meal and iron-treated cottonseed meal in different laying hen genotypes.

The effects of dietary screw-pressed cottonseed meal (CSM) and iron-treated CSM on laying performance and discolourations in eggs were examined in a range of hen genotypes. In experiment 1, six genotypes, obtained at point-of-lay from various sources, were fed on a non-CSM diet, a diet with 300 g CSM/kg, and a diet containing iron-treated CSM at 300 g/kg. In experiment 2, two of these genotypes were reared together from day-old and were fed from 10 to 18 weeks on a non-CSM diet or a diet containing iron-treated CSM at 250 g/kg. They were then fed on a non-CSM layer diet or a diet containing iron-treated CSM at 300 g/kg, in a 2 x 2 x 2 factorial design that also examined the effects of the rearing diet. 2. The effects on food intakes and egg production of including CSM and iron-treated CSM in layer diets depended on the genotype of the hens. The strongest interaction between breed and diet was on food intake, the breed Hubbard Golden Comet (HGC) being the least tolerant of CSM and iron-treated CSM. 3. Inclusion of iron-treated CSM in the rearer diet to supply approximately 70% of the dietary protein had no adverse effects on growth or age at first egg. Food intake and egg production between 18 and 26 weeks were affected by the iron-treated CSM layer diet, but there were no carry-over effects attributable to the rearing diets. 4. Genotype was not a factor in the development of the gossypol-related brown yolk discolouration in fresh or warm-stored eggs of hens fed on a CSM-based diet containing 197 mg free gossypol/kg and 52 mg cyclopropenoid fatty acids (CPFA)/kg (experiment 1). 5. In both experiments, the susceptibility of eggs to the CPFA-related cold storage effects depended on the genotype of the hen, eggs from hens of the HCG breed being more affected than those of ISA hens. 6. Treatment of CSM with crystalline ferrous sulphate heptahydrate, at a 4:1 weight ratio of iron to free gossypol, prevented brown yolk discolourations in all genotypes tested, as assessed by subjecting egg yolks to atmospheres of ammonia, and cold storage of eggs.

Ammonia↗

PubMed1991

Optimum isoleucine requirement of laying hens and the effect of age.

1. Medium weight laying hens were used for an assay to determine their isoleucine requirement between 26 and 36 weeks of age and again between 46 and 56 weeks of age. 2. Two isoleucine-limiting mixtures were formulated with similar amino acid profiles, one containing 198 g and the other 110 g crude protein per kg diet. These mixtures were blended to give a series of 11 diets with isoleucine contents ranging from 7.6 to 3.8 g/kg. The lowest protein diet was also fed with a supplement of L-isoleucine. Each of the 12 diets was given to 5 groups of 24 laying hens. 3. The daily isoleucine requirement of individual laying hens was estimated to be 9.48 mg/g egg output plus 44.47 mg/kg body weight per day for the 1st period and 12.11 mg/g egg output plus 6.86 mg/kg body weight per day for the 2nd period. Calculated optimum intakes of isoleucine for various ratios of cost of input to value of output are tabulated. For example, for a flock of medium weight hens producing an average of 50 g daily egg mass, the optimum isoleucine intake (mg/hen d) varied between 760 and 890 varying for ratios of costs to egg prices. 4. It is concluded that the isoleucine required per day does not decrease during the first laying year despite a decrease in rate of egg output.

Aging↗

PubMed1990

Note on the effects of protein concentration on responses to dietary lysine by chicks.

1. This paper gives further analyses of data from previously reported trials in which chicks were fed diets with protein concentrations ranging from 140 to 280 g/kg diet, with the lysine content varied at each protein concentration. 2. Alternative methods of estimating the lysine requirement, at each concentration of protein, are investigated. 3. Although these methods produce rather different estimates of requirement, they do not change the conclusion that the lysine needed for maximum growth or maximum efficiency of food utilisation is a linear function of dietary protein concentration throughout the range from 140 to 280 g crude protein/kg. 4. It is concluded that lysine requirements for growing chicks should be specified as a proportion of the protein and not as a proportion of the diet.

Animal Feed↗

PubMed1990

Effects of arginine and protein on chicks' responses to dietary lysine.

1. A chick experiment was designed to test whether the proven effect of excess protein on the requirement for lysine was associated with the arginine content of the protein. 2. Protein contents of 180, 220, 260 and 300 g/kg diet were fed in combination with lysine concentrations of 38, 43, 48, 53 and 58 g/kg crude protein and arginine concentrations of 49.4 or 68.4 g/kg crude protein. 3. Growth rate and efficiency of food utilisation were not significantly affected by the arginine content of the protein. Significant responses to lysine were obtained at all protein contents. 4. Lysine required for maximum growth or maximum food efficiency increased in direct proportion to the protein content of the diet and was not affected by arginine content of the diet within the range of concentrations tested.

Animal Feed↗

PubMed1990

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

1. Chicks were fed from 4 to 18 d on 40 diets containing all combinations of 8 crude protein (CP) concentrations (from 160 to 300 g/kg) and 5 tryptophan concentrations (from 7.5 to 13.5 g tryptophan/kg CP). 2. At each protein concentration there were responses in growth rate and in efficiency of food utilisation to supplementation with tryptophan. Curves were fitted to estimate the maximum response at each protein concentration. 3. The amounts of tryptophan required (g/kg) for maximum growth and maximum food efficiency were each linear functions of dietary protein concentration. The chick's requirement for tryptophan can be expressed as 12 g/kg CP. 4. It is concluded that a fixed ratio of tryptophan to protein should be specified in practical diet formulation, rather than a minimum dietary concentration of tryptophan.

Animal Feed↗

PubMed1990

Protein requirement of fast- and slow-growing chicks.

1. Responses of male broiler chicks and male chicks of an egg-laying stock to dietary crude protein (CP) concentrations ranging from 167 to 251 g/kg (metabolisable energy content 13 MJ/kg) were compared from 0 to 21 d of age, using 20 groups of 9 or 10 chicks (5 diets x 2 stocks x 2 replicates). 2. Average growth rate in the broilers was three times that of the layer chicks. The broilers needed at least 251 g CP/kg to maximise their liveweight gain but the layer chicks needed only about 188 g CP/kg. 3. The broiler chicks ate less than twice as much food as the layers and their maximum gain/food ratio was 0.6 compared with 0.4 for the layer chicks. These maximum efficiencies of conversion of food to liveweight were achieved in both cases with a diet containing 230 g CP/kg. 4. The efficiency of protein utilisation (above maintenance) was the same in fast- and slow-growing genotypes (about 0.47 g protein gain/g protein consumed). 5. Carcase analysis at 3 weeks of age showed that the broilers had deposited more fat than the layers and that protein content of the diet had markedly influenced fat deposition in both stocks. Fat in the whole body increased from 29 to 87 g/kg in the layer chicks and from 81 to 123 g/kg in the broilers as dietary protein was reduced from 251 to 167 g/kg. 6. The optimum protein to energy ratio of a chick starter diet will depend on the growth potential of the stock, as well as the cost of ingredients and the value of fatter or leaner carcases.

Adipose Tissue↗

PubMed1988

Partitioning of the response to protein between egg number and egg weight.

1. Data from published trials with laying hens were examined to see whether the concentration of dietary protein needed to achieve maximum egg weight was greater than the amount needed to achieve maximum rate of lay. 2. It is concluded that both rate of lay and egg weight continue to show small responses up to the same level of protein (or limiting amino acid) input. 3. When predicting egg output using asymptotic models, a reasonable assumption is that small increments in dietary protein, close to the optimum, will evoke equal proportional responses in egg size and in rate of lay. 4. When protein supply is severely limiting, the major response is a reduction in rate of lay. Egg weight seldom falls below 0.90 of its maximum value, however inadequate the protein intake may be.

Animals↗

PubMed1988

Model for the prediction of mean time of oviposition for hens kept in different light and dark cycles.

1. Evidence from 26 short-term experiments with laying fowls has been analysed to determine the relationship between onset of darkness and mean time of oviposition for light-dark cycles ranging from 21 h to 30 h incorporating various dark periods from 5 h up to 23 h. 2. When the light-dark cycle is equal to or longer than 24 h, mean time of lay (H) in hours from onset of darkness is predicted by the equation: H = 64.62-2.161C + 0.268S, where C = cycle length (h) and S = scotoperiod (h) (multiple correlation coefficient = 0.977). 3. For light-dark cycles shorter than 24 h, the best equation found was: H = -4.97 + 0.740C + 4.482S - 0.175CS (multiple correlation coefficient = 0.981). 4. The meaning of these equations in relation to events in the ovulation cycle of the fowl is discussed.

Animals↗

PubMed1988

Experiments with the Cornell intermittent lighting system for laying hens.

1. Two experiments were conducted to provide further evidence about rate of lay under the Cornell lighting system (2L:4D:8L:10D). Each used 1728 hens of each of 2 brown-egg stocks in 12 light-proof rooms. 2. In the first the Cornell system was compared at 2 light intensities (average values 2 and 10 lux) with a conventional step up lighting programme. In the second, Cornell lighting was introduced at 18, 21 or 24 weeks of age and compared with a step up programme. 3. Total egg output was essentially the same from the Cornell lighting system, using 10 h light/d, as from the step up programme using 16 h/d. When the Cornell system was applied abruptly at 18 weeks to pullets which had been reared on short days (8L:16D) sexual maturity was advanced, resulting in an increase in mean rate of lay to 72 weeks of age and a reduction in mean egg size. Application of the Cornell system from 21 or 24 weeks gave the same egg numbers and the same egg size as the step up programme. 4. Food intake was about 2% lower with the Cornell treatment in both experiments. Although this difference was not quite significant in either, it probably reflects a real effect of the reduced hours of light. It represents a greater potential cost saving than the reduced electricity consumption. 5. Birds in rooms with an average light intensity of 2 lux laid slightly fewer eggs but their eggs were 0.5 g heavier than those laid in rooms maintained at 10 lux. There were no interactions between light intensity and light pattern or between stocks and light pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Experiments with the Bio-mittent lighting system for laying hens.

1. Two experiments are described in which a system of intermittent lighting (15 min light followed by 45 min dark for 15 h, then 15 min light, 30 min dark, 15 min light and 8 h dark) was applied to laying pullets from 37 to 72 weeks of age. A step-up lighting programme was used as a control treatment (8L:16D from 0 to 18 weeks, photoperiod increased by 20 min each week from 18 to 41 weeks, 16L:8D from 41 to 72 weeks of age). 2. Food consumption was reduced by about 5% when intermittent lighting was in use and by 3.8% for the period from 18 to 72 weeks. 3. Rate of lay and egg weight were similar for intermittent lighting and the control treatment, provided that protein content of the diet was adjusted to maintain an adequate amino acid intake. 4. In the second trial 2 stocks, 2 stocking densities confounded with 2 temperatures and 2 types of food trough were used. Each of these factors affected food intake and it was found that more food was saved by intermittent lighting when intake was high and less when it was low. The proportion saved was approximately 5%. 5. Mortality was slightly but not significantly lower in both experiments where intermittent lighting was used. This may indicate that caged pullets are under less stress when intermittent lighting is used.

Animals↗

PubMed1988

Timing of oviposition in mixed systems using bright light, dim light and darkness.

1. Two experiments were conducted to examine time of oviposition for hens exposed to continuous dim lighting, to dim lighting alternating with bright lighting in a 24 h cycle or to a mixed system using bright light, dim light and darkness. 2. Under continuous dim lighting (0.3 lux), the pattern of ovipositions was the same as that reported previously for constant darkness, more eggs being laid around midnight than around noon. 3. With alternating bright and dim phases, mean time of lay was approximately 16 h after the transition from bright to dim lighting, which was 3 h earlier than under the corresponding cycle of light and dark. This phase advance was the same whether the bright:dim ratio was 16:1 or 160:1. 4. Dim lighting (1.25 lux) preceded by a period of normal lighting (5 lux or 50 lux) and followed by 8 h darkness was treated as part of the photoperiod. 5. It is concluded that, when there is no darkness, a period of dim lighting is treated as darkness, provided the contrast between bright and dim phases is sufficient. However, when darkness, dim light and bright light are all included in a cycle, the dim light is treated as part of the photoperiod, even though there may be a contrast between the brightly lit and dimly lit phases which, in the absence of darkness, would cause the dim phase to be treated as dark.

Animals↗

PubMed1988

Time of lay in hens exposed to intermittent lighting.

1. Two short-term trials are described in which laying hens were exposed to 8 h light followed by 8 one-min pulses of light at hourly intervals followed by 8 h darkness (8L:8i:8D). The effect of varying the intensity of illumination during the one-min pulses and the effect of placing the intermittent lighting before the 8 h photoperiod (8i:8L:8D), were studied. 2. Normal egg production was maintained by the 8L:8i:8D system when the light pulses were at 20 lux, but not at 5 lux. This suggests a minimum threshold for illumination with short light pulses higher than that needed for continuous lighting. 3. Time of lay under 8L:8i:8D was the same as with 8L:16D in relation to the beginning and ending of the 8 h main photoperiod, but with 8i:8L:8D mean time of lay was 2 to 3 h earlier. Thus the hourly pulses caused a phase advance when placed before the normal photoperiod but did not cause a phase delay when placed after the normal photoperiod.

Animals↗