Journal of Agricultural Science, 47

M. L. Ryder. The pre-natal development of follicle population in the Romney lamb (Vol. 47, Pt. 1)

M. L. Ryder. Observations of nutritional and seasonal changes in the fleeces of some Masham sheep (Vol. 47, Pt. 2)

Will readers please note that the plates illustrating the above articles have been incorrectly placed. The present Plate 7 facing p. 144 should be Plate 1 facing p. 10 and the present Plate 1 facing p. 10 should be Plate 7 facing p. 144.

The design and analysis of rotation experiments present problems which are not encountered in annual experiments. The problems of design have been discussed by Yates (1949) and Stevens (1951 b). This paper is concerned with problems of statistical analysis. The experiment described is sufficiently general in its design for it to serve usefully as a basis of discussion of methods of analysis, both of the mean yields and of the measures of secular trend. It is shown that rotation experiments, without replicates within series, can be adequately analysed.

1. This work presents an analysis of the ecological differences between populations in terms of one important developmental system, the timing of inflorescence development on the shoot apex, and its corollary, the partition of energy between seed production and continued vegetative growth.

The object of the first paper is to establish rapid and accurate greenhouse methods for testing response to low temperature and photoperiod, the most important environmental factors influencing inflorescence development.

2. The timing of inflorescence development was studied by the dissection of the shoot apex in several lines of cereals under various temperatures and photoperiods. The rate of leaf appearance is linear on any shoot and is unaffected by the initiation of spikelet buds on that shoot. The elongation of the shoot apex is exponential, being gradual during vegetative growth but increasing at spikelet initiation. The elongation of internodes begins only at the late spikelet bud stage, and progresses stepwise, one internode beginning to elongate as the preceding one ceases.

The general pattern of inflorescence development is similar in all material, but differences occur between lines in the time at which the spikelets are initiated and in the rate of subsequent elongation. These pilot results make it possible to choose the most suitable measures of reproductive development and the most effective environmental treatments to distinguish between populations. The leaf number before heading on the main shoot is used as a quantitative measure of inflorescence development. It records the physiologic age at which spikelet initiation occurs, and is only slightly affected by temperature fluctuations between 10 and 20° C.

3. In the tests for response to vernalization, the germinating seeds are exposed to low temperatures (0–5° C.) for varying lengths of time, and then planted in long day or continuous light. The temperature immediately after planting is kept at 10–15° C. (50–60° F.) to avoid either further vernalization or devernalization. The photoperiod is optimum, and the rapidity of heading is a measure of response to low temperature.

4. The usual method of testing for response to photoperiod under a range of constant photoperiods has the disadvantage that in short days the plants may head slowly or not at all, thus increasing the demand for time and labour. A more rapid turnover can be obtained by exposing the seedlings to differential photoperiods from germination onwards and transferring at a series of dates to long day or continuous light. The leaf number at transfer and the leaf number before heading are recorded, and from these the inductive effects of the initial photoperiods can be calculated. All seedlings must be fully vernalized, i.e. competent to respond to photoperiod, before the tests begin.

The following applications of the methods are suggested:

(i) The agronomic classification of populations and the prediction of their behaviour under specified local climate and farming practice.

(ii) The rapid selection and progeny testing of parental material in plant breeding work.

(iii) The assessment of the potential genetic variation within populations and the study of the adaptive changes occurring under selection.

Forty adult (15 months old) fat-tailed Egyptian rams and ewes of the Rahmani and Ossimi breeds were available at the Animal Breeding Research Farm, Giza, Egypt (30° N.). Body temperature and respiration rates were measured twice weekly throughout the year 1953–4. On days of observations, four readings were taken at 10 a.m., 12 noon, 2 p.m. and 4 p.m. Skin temperature was measured once weekly at noon for nine body regions, using a precision bridge thermometer. The effects of docking and pregnancy were also studied.

1. There were seasonal variations in body temperature and respiration rate. The maximum values were during summer and the minimum during winter. The seasonal rate of change was greater in respiration rate than in body temperature.

2. Body temperature was 39·1 and 39·0° C. for the Ossimi rams and ewes respectively, while it was 38·9° C. for both Rahmani sexes. Respiration rate per minute was 42·0, 39·3, for Ossimi rams and ewes and 38·2 and 35·9 for Rahmani rams and ewes respectively. Body temperature and respiration rate were higher in the Ossimi than in the Rahmani breed, and in the males than in the females. Breed differences may be related to anatomical differences such as body conformation, size of skull and tail, thickness of skin and subcutaneous fat and differences in coat characteristics. Sex differences may be associated with the live weight of the animals as well as differences in the hormonal system.

3. Pregnancy had no effect on body temperature and respiration rate in either breed.

4. Different experimental groups reacted similarly with respect to diurnal variations in body temperature and respiration rate; the lowest values being at 10 a.m. and the highest at 4 p.m. Maximum body temperature and respiration rate preceded maximum environmental temperature by 2–4 hr. The diurnal rate of change in respiration rate was higher than that in body temperature. The diurnal changes in body temperature and respiration rate of animals were mainly due to the changes in the environmental temperature throughout the day.

5. (a) Skin temperature varied from 33·7 to 39·7° C., according to season and body region. Seasonal variations in skin temperature of different body regions showed the same trend.

(b) Highest skin temperatures were recorded for middle and upper fat tail, back thoracic and middle scrotum regions, while the lowest were recorded in lower and upper scrotum, lower tail and neck ventral regions. The breast region had an intermediate skin temperature. The different skin temperatures were due to anatomical differences such as the thickness of subcutaneous fat, density of covering wool or to differences in the amount of blood supply.

6. Docked rams had a lower skin temperature and respiration rate than controls, denoting better heat regulation. This may be due to metabolic differences or anatomical changes in the body such as the thickness of subcutaneous fat.

1. A review of the literature indicated: (a) A lack of agreement upon whether or not restriction of the plane of feeding from weaning or 100 lb. live weight to bacon weight improves efficiency of food conversion. (b) That a severe restriction of the plane of feeding improves carcass-quality measurements, (c) That a less severe restriction of food intake brings the total growth period within a range more acceptable to the farmer, but only has a small effect in improving carcass quality, (d) That the small benefits to quality from this less severe restriction may be equalled or surpassed by quite small changes in the genetic ‘type’ of pig fed. (e) That there are probably interactions in the response of different ‘types’ of pig to different planes of feeding.

2. Two experiments were undertaken. In Exp. 1 both Large White × Swedish Landrace pigs and Large White × Wessex Saddleback pigs were fed from weaning to bacon weight to one of three planes of feeding. Exp. 2 was very similar in design except for some modifications to planes of feeding and the substitution of Essex Saddleback × Large White pigs in place of the Wessex crosses.

3. In Exp. 1 the planes of feeding, according to our stated definitions in terms of total digestible nutrients consumed daily at different live weights, were: very high during both growing and finishing periods (VH-VH); very high during the growing period but restricted during the finishing period (VH-R); and very low during both growing and finishing periods (VL-VL). In Exp. 2 the planes of feeding were: VH-VH; VH-R, the restriction being slightly more severe than in Exp. 1; and low during both growing and finishing periods (L-L).

4. In Exp. 1 there was no difference in growth rate between breed crosses. Pigs on the VH-R and VL-VL planes were 12 and 88 days older respectively at bacon weight than those fed to the VH-VH plane. In Exp. 2, Landrace crosses grew faster than the Essex crosses on the VH-VH and VH-R planes, but Essex crosses grew faster on the L-L plane. Landrace crosses fed to the VH-R and L-L planes were 11 and 63 days older respectively at bacon weight than others fed to the VH-VH plane. Essex crosses fed to the VH-R and L-L planes were 16 and 53 days older respectively at bacon weight than others fed to the VH-VH plane.

5. In Exp. 1 there was no difference in food-conversion efficiency (f.c.e.) between breed crosses. There was no significant difference in f.c.e. between the VH-VH and VH-R planes, but there was a loss of 14% in F.C.E. on the VL-VL plane. In Exp. 2 the Landrace crosses had better F.C.E.'s than the Essex crosses on the VH-VH and VH-R planes, but Essex crosses were the more efficient on the L-L plane. There was no significant difference in F.C.E. between the VH-VH and VH-R planes for either breed cross, but there were losses in efficiency of 4 and 14% on the L-L plane for the Essex and Landrace crosses respectively.

6. In Exp. 1 the Landrace crosses had less back fat over the shoulder than had the Wessex crosses. Pigs of both crosses fed to the VH-R plane had smaller fat measurements than those fed to the VH-VH plane, but this improvement was only significant for minimum back fat. Landrace crosses also had less fat over the ‘eye’ muscle when fed to the VH-R plane, but this did not apply with the Wessex crosses. The difference in carcass quality attributable to the restricted plane of feeding after 100 lb. live weight was considered to be equalled by the difference between breed crosses. The improvement in carcass-quality measurements between pigs fed to the VH-VH and VL-VL planes surpassed the difference between breed crosses, but the carcasses tended to be soft. However, no data were available on the iodine numbers of the fats.

7. In Exp. 2 the Landrace crosses had less fat over the shoulder and over the eye muscle and smaller minimum back-fat measurements than had the Essex crosses. Pigs of both crosses fed to the VH-R plane had smaller fat measurements than those fed to the VH-VH plane, the difference being significant for shoulder fat and minimum back fat. Again the differences between the effects of these two planes of feeding and between the two breed crosses were considered about equal, and again the difference between breed crosses was surpassed by the difference between the carcass measurements of pigs fed to the VH-VH and L-L planes. In Exp. 2 the effects of planes of feeding upon length of carcass, thickness of streak, percentage fore and percentage middle differed significantly between the two breed crosses.

8. When carcass data from both experiments were compared it was apparent that differences between breeds or strains of bacon-type pigs are likely to be of more importance in the production of high-grade bacon than attempts to alter the conformation by varying the plane of feeding—and thus the growth curve—within the limits acceptable in practice.

9. Although previous evidence indicates that males grow faster than females, there was in Exp. 1 no significant difference in growth rate between the sexes. In Exp. 2 there was again no overall significant sex effect, but during the finishing period females grew faster than males on the VH-VH and VH-R planes, but males grew the faster on the L-L plane. In Exp. 1 there was no significant difference between sexes in F.C.E., but in Exp. 2 males were less efficient than females on the VH-VH and VH-R planes, but were the more efficient on the L-L plane, this interaction again developing principally during the finishing period.

10. In both experiments females had carcasses which were longer, had less fat, larger areas of ‘eye’ muscle and larger hams than males. In both experiments the restricted plane of feeding after 100 lb. live weight reduced the shoulder-fat measurements of females but had no effect on those of males which, being the fatter, had the greatest need of improvement to achieve the highest grade. However, the statistical significance of this interaction was low and it requires confirmation.

11. It is not the intention of the authors that these results should be taken to apply in general to the breed crosses used. The breed crosses were chosen solely as pigs which would differ somewhat in genetic type from each other.

12. The results from these experiments confirmed the indications from the literature which have been noted in paragraph 1 of this summary. The results and some of their implications have been discussed in the text.

1. A study was made of the performance of eight litters of pigs housed under two widely different levels of ambient temperature during the suckling period and under uniform conditions from weaning to 200 lb. live weight.

2. There was no significant treatment difference in the amount of milk suckled, but the pigs exposed to the lower temperature consumed more solid food before weaning.

3. Up to weaning those kept at the higher temperature were the more efficient converters of milk and solid food into live weight.

4. There was a highly significant correlation between milk suckled and live-weight gain.

5. Probably through excessive handling, the pigs were under weight at weaning, but the postweaning performance appeared to be unaffected by the pre-weaning treatment.

6. The average milk yield of six sows from the 3rd to the 56th day of lactation was 275 kg. 605 lb.) (variations 202–347 kg. (445–764 lb.)). Yields have been compared with others published.

7. After allowing for maintenance requirements and weight gain or loss it is estimated that the sows required 412 Calories of net energy to produce 1 lb. of milk.

1. The information analysed in this report is taken from records of the Compton herd of Large White pigs over a period of about 4 years.

2. Length of gestation period: close concentration about the mean of 114·17 days; no apparent relationship between litter size and extremely long or short gestation period. There was no difference in the average duration of pregnancy as between old and young sows, nor was there any evidence of a characteristic tendency to long or short pregnancies in individuals. The incidence of stillbirths appears to be independent of the length of the gestation period.

3. The number of pigs born, alive or dead, ranged from 3 to 24, the average being 13·12. The average number of pigs born alive was 12·4 and the average number weaned was 8·1.

4. The average number of pigs born rose with successive pregnancies to a maximum of more than 15 in the 6th and 7th litter and declined thereafter. The average number born alive reached a maximum of more than 14 in the 5th litter and declined thereafter, the decline being less marked among pigs born alive than among all pigs including stillbirths, apparently because embryonic mortality (before parturition) bears more heavily on the litters of older sows, whereas the incidence of stillbirths is not related to age (or to the ordinal number of the litter).

5. The incidence of stillbirths was studied in relation to litter size, the data being compared with similar data recorded elsewhere. The proportion of stillbirths was higher among female piglets than among males. The reverse was true in litters of less than average size, and the possible significance of this difference between smaller and larger litters is discussed.

6. The foetal sex ratio appears to bear no relation to the ordinal number of the litter or to its size.

7. The reasons for discard of sows which have been culled during the period under review have been recorded and are briefly discussed.

The present investigation is concerned with the influence of procaine penicillin and aureomycin on digestion. In particular, the effect of antibiotics, in amounts generally included in feeding-stuffs, on the bacterial digestion of cellulose in the large intestine of the pig, was investigated.

The digestibility of a basal diet composed of fine bran, maize meal, dried lucerne meal and whitefish meal was determined with and without the addition of antibiotic. No effect was noted on the digestibility of any food constituent.

The diet fed in four digestion trials contained 500 g. of shredded fodder cellulose. The digestion coefficient for the crude fibre, in these diets rich in cellulose, was 76·2% when 18 mg. of procaine penicillin was added per lb. of meal and 76·8% when no antibiotic was added.

The nitrogen-free extractives in the fodder cellulose are mainly if not entirely composed of xylan. If the nitrogen-free extractives and crude fibre are combined to give ‘cellulose’ as defined by Norman & Jenkins, the digestion coefficients for the cellulose were 85·7, 83·4, 85·7 and 87·2%, respectively, thus showing little difference between treatments.

There is no warrant for assuming that the antibiotics had any bactericidal or bacteriostatic effect on the cellulose-splitting organisms.

Synthetic soil crumbs stabilized by the addition of small quantities of a polymer, and natural soil crumbs from old grassland, have been extracted with neutral sodium pyrophosphate and alkali and the strengths of the crumbs compared before and after extraction, using the sodium saturation technique. Three polymers were used: polyvinyl alcohol (a non-ionic polymer), sodium alginate, and a vinyl acetate-maleic anhydride co-polymer (Vama), the latter both carboxylated polymers. Pyrophosphate was able to displace the carboxylated polymers from the synthetic crumbs, but not the stabilizing fraction of the organic matter from the grassland crumbs. 0·5N-NaOH produced a much greater reduction on the strength of the alginate treated crumbs compared with Vama crumbs, which is attributed to the weaker hydrogen bonds formed by the former. Prolonged leaching with alkali removed a considerable part of the stabilizing organic matter in the grassland crumbs. Neither method of extraction affected the stability of the polyvinyl alcohol crumbs.

It is concluded that the grassland crumbs are stabilized by the formation of inter-lamellar complexes with the clay in the crumbs, and probably that the substance forming the complexes is a polymer and contains amino-groups.

Evidence is also given that phosphate ions and the carboxylated polymers are attached in the same manner to the edges of the clay crystals.

The failure of a high proportion of fertile eggs to hatch still remains a major cause of financial loss to the poultry industry. Payne (1919) pointed out the consistent manner in which embryonic mortality manifested peak periods at the fourth day and the nineteenth day of incubation, and he drew attention to the fact that the latter period of susoeptibility showed an increased level of mortality with artificial incubation compared with natural methods. Romanoff (1949) summarized the explanations put forward to account for these two peaks of embryonic mortality. Riddle (1930) suggested that the first period was caused by respiratory maladjustments, and he, and others, considered that the failure of the developing embryo to make the fine adjustments at this time and to deal effectively with the excretion of various toxic substances may be a major cause of death. The second peak period of mortality occurs at the transition from allantoic to pulmonary respiration. Failure to achieve this change, with the consequent death of the chick in the last stages of development, may be greatly influenced by the cumulative effect of all the unfavourable conditions to which the hatching egg has been subjected. Not the least of these will be environmental conditions in the incubator and the incubator house adversely affecting the oxygen supply and the relative humidity.

1. An investigation to compare winter and spring defoliation of S.147 oats, and incorporating an application of nitrogen, was carried out during the seasons 1950/1, 1951/2 and 1952/3.

2. Forage available in the spring was considerably greater than that available in the winter, but it had a lower crude-protein content.

3. Compared with the undefoliated oats, both spring and winter defoliation reduced the number of productive tillers by significant amounts, but nitrogen had no effect on tiller numbers under defoliated and undefoliated conditions.

4. Spring and winter defoliation caused significant reductions in grain yields; with winter defoliation the decline in yields was substantial. On the undefoliated and spring-defoliated oats nitrogen increased yields by significant amounts.

5. Spring and winter defoliation reduced straw yields, but nitrogen on both treatments and on the undefoliated oats gave significant yield increases.