The subcutaneous, intermuscular and cavity fat depots of the half carcasses of 15 Large White × Landrace castrated male pigs, forming a growth series from 8 to 62 kg live weight, were dissected. Seventy individual muscles of these pigs were analysed for intramuscular fat content. The growth rates of each of the four fat depots, relative to total fat, were similar. Subcutaneous fat was the predominant fat depot over the growth range studied. Both intramuscular fat and non-fat dry matter grew faster than the entire muscles containing them. Growth gradients for the intramuscular fat of muscle groups, relative to either total intramuscular fat or to total fat, were similar to those for the entire muscles. The growth gradients for muscle groups were affected by neither the growth of the contained intramuscular fat nor the contained non-fat dry matter. Intramuscular fat density, but not non-fat dry-matter density, varied throughout the carcass. The fat content of muscles was highest in those that could be useful as subcutaneous insulators.

A total of 124 pregnant multiparous sows were allocated to either control or treated groups. The treated sows were given 175 μg of an analogue of prostaglandin F2α (I.C.I. Ltd compound no. 80996) on day 113 of gestation. Gestation lengths for the control and treated groups were 116·3 ± 1·44 and 114·0 ± 0·31 days respectively. Two thirds of the treated sows farrowed between 24 and 32 h following administration of the drug. The number of live and stillborn pigs per litter did not differ between the two groups but birth weights were significantly higher in natural than in induced farrowing litters (1·36 v. 1·26 kg). Piglet mortality up to 10 days of age was significantly less in control litters (0·74 v. 1·61). The subsequent reproduction of sows was not affected by treatment with the prostaglandin analogue

Semen from eight Murrah buffalo bulls was collected and analysed for physical and biochemical determinants throughout the year. Depending upon the climatic conditions, the whole year was divided into four periods. The mean values of volume, density, mass motility and sperm concentration was 1·64 + 0·060 ml, 2·48±0·032 (3-point scale), 2·65±0·069 (5-point scale) and 1185 ±19·2 million/ml, respectively. The mean values of alkaline and acid phosphatases were 1238±47·4 and 1244±54·5 King-Armstrong units (KAU)/100 ml of seminal plasma. Average figures for citric acid, calcium, phosphorus, total nitrogen and non-protein nitrogen (NPN) were 507 + 14·1, 53·0±l·2, 121±4·9, 649±12·8 and 116±2·0 mg/100 ml of seminal plasma. Periods of the year had significant effect on volume, alkaline and acid phosphatases, citric acid and NPN (P < 0·01). Different correlations of physical and biochemical determinants are discussed. Of all the determinants only weight of the bull, sperm concentration and NPN were found to be positively correlated with fertility while phosphorus was negatively correlated.

Determinations of sodium bicarbonate (pH 8·5) extractable P made on profiles of a sandy loam soil 7 and 8 years after fertilizer application to coconut in the Dry zone of Sri Lanka showed that the downward movement of P from concentrated superphosphate was greater than from rock phosphate (saphos). The surface layers (0–15 cm) of soil given concentrated superphosphate had higher P values (60 and 89 mg/kg for the 8th and 9th year respectively) than those given rock phosphate (3 and 16·5 mg/kg). At 40 cm depth the concentrated superphosphate treatment had 6 and 30 mg P/kg but the rook phosphate treatment had almost zero P at and below 40 cm.

Phosphorus in the soil profile 8 years after fertilizer application was fractionated by the method of Chang & Jackson. Concentrated superphosphate treatment increased the Al-P and to a lesser degree Fe-P and Ca-P. Rock phosphate treatment increased the Ca-P and to a lesser extent Fe-P and Al-P. Phosphorus concentration in the 14th leaf was significantly correlated with Al-P, Fe-P and NaHCO3-P but not with Ca-P and organic P.

The significance of the findings to phosphorus fertilizer application to coconut is discussed.

The effects of the planting density of the seed potato crop, the date on which it was defoliated and the time at which it was lifted, on the weight, shape and number of eyes on progeny tubers in a given size grade, were small and were unlikely to be of practical importance.

Size grade was both closely and linearly related to the number of eyes on a tuber and seemed to be a perfectly adequate practical method of grading seed tubers according to their number of eyes.

Blood samples were taken each week from 30 individually-reared heifer calves between 1 and 13 weeks of age and analysed for packed cell volume, blood glucose and Hb; and serum albumin, urea-nitrogen, total protein, inorganic phosphate, Ca, Mg, K, Na, Fe and total iron-binding capacity. All calves were weaned by 6 weeks of age, and were fed ad libitum.

There were significant changes (P < 0·001) in blood concentrations with age for most constituents. Concentrations of albumin and Fe increased and of K decreased steadily over the whole of the period. Glucose and total iron-binding capacity concentrations decreased until about the 6th week of life and then increased.

There were significant correlations (P < 0·05) for both the calves' weight gain and their feed intake from 6 to 13 weeks with the mean concentrations of glucose, inorganic phosphate, Na, albumin and total iron-binding capacity over the same period. Weight gain during this period was also correlated with serum Fe concentration. When weight gains were adjusted for the feed intake, the correlations between weight gain and the concentrations of all blood constituents became insignificant.

There was a significant correlation (P < 0·05) between weight gain after 6 weeks of age and Hb concentration before 6 weeks. However, when weight gain was adjusted for birth weight, this correlation became insignificant.

Partial closure of the stomata occurred during the middle of the day even when tea plants were growing in a wet soil and there were similar diurnal changes in the xylem water potential (ψx). As the soil dried the daily minimum values of ψx declined, more in some clones than in others, and there were also interesting differences between clones in the sensitivity of their stomata to changes in ψx. Possible ways in which these observations could form the basis of tests for screening clones for drought resistance are discussed.

The reproductive potential of a sheep system is much reduced by the failure of released ova to be fertilized and to survive to parturition. This paper looks at currently available information on fertilization failure and early embryonic deaths. Separate hypotheses are proposed for fertilization and for early embryonic mortality. For fertilization, the hypothesis is that a ewe that mates with a ram will end up with either all or none of her released ova fertilized. For embryonic mortality, the hypothesis is that the survival of a fertilized ovum depends only on how many ova were released with it and is independent of the survival or death of those released with it. A mathematical model is constructed on these hypotheses and its predictions are compared with published experimental results of other workers.

Concentrations of serum lipids, concentrations and compositions of liver lipids, and ultrastructural composition of hepatocytes were measured in non-lactating cows following a 6-day fast. There was no change in the concentration of serum lipids due to fasting. The content of total lipid in liver (g/kg of liver wet weight) doubled due to an eightfold increase in triglyceride, a twofold increase in cholesterol ester, a fourfold increase in free fatty acid and a 50% increase in cholesterol. The composition of liver lipids (g lipid/100 g of total lipid) changed with an increase in the proportions of triglyceride and free fatty acid, a decrease in the proportion of phospholipid, and no change in the proportion of cholesterol and cholesterol ester. The ultrastructural composition of the hepatocytes changed in fasted cows with an increase in the volume density of cytoplasm occupied by lipid droplets and lysosomes and a decrease in the volume density of glycogen. The number of mitochondria per cell decreased and volume of individual mitochondria increased. The fatty liver induced by fasting non-lactating cows was chemically and morphologically different from the fatty liver induced by fasting lactating cows.

The digestibilities of grass cell wall constituents determined in a digestion trial were compared with those obtained by suspending various isolated cell wall preparations in nylon bags in the rumen of a sheep. Particular attention was paid to acetyl groups and to individual sugars, which were determined in both cases by gas liquid chromatography.

For dried grass and hay in the digestion trial the cell wall constituents showed digestibilities decreasing in the following order: arabinose, galactose, glucose, xylose, acetyl, lignin.

For a leaf cell wall preparation derived from all cell types except mesophyll, the nylon bag technique allowed the same order of digestibilities; rhamnose and uronic acids were also measured and found to be rapidly digested. Mesophyll cell walls placed in nylon bags were more readily digested than non-mesophyll. All the sugars, and also acetyl groups, were digested to the same extent.

In a grass cell wall preparation isolated from sheep faeces, tested similarly, xylose and glucose were digested to the same extent, but acetyl groups were less digested.

Removal of acetyl groups, using sodium ethoxide, which left the sugar composition and lignin content unchanged, increased the digestibility particularly of the cell walls from faeces.

The results are discussed with reference to the relationship between cell wall composition and digestibility.

A replicated trial of 18 families of Navy-bean breeding lines in the F4 generation was grown at Cambridge. The selection-index technique was used to investigate means of improving the efficiency of simultaneous selection for four criteria, namely yield, seed shape (numerical scores from ‘good’ to ‘poor’), early maturity and increased height of pod tips. Relative economic weights were chosen. The yield components and a range of characters describing plant type were measured making 15 characters in all, and combinations of these were included in 32 indices.

It was predicted that simultaneous selection would be limited by adverse correlations between some of the four selection criteria, especially early maturity and height. The estimated efficiency of selection would hardly be improved by including information on the yield components. Combinations of the plant type characters, on the other hand, were predicted to provide considerable additional advance amounting to a 10% improvement when information on total number of nodes and inflorescences and hypocotyl diameter was included.

It was concluded that the time involved in collecting yield component data would be better spent collecting information on a limited number of plant type characteristics in future trials, and that an ideal plant was one with reduced branching and a few heavily podded inflorescences borne on a tall plant with a strong base.

The effects of the physical environment in Manitoba on the growth of Vicia faba minor cv. Diana were monitored during 1974–5. Seed yields and dry-matter production were considerably lower than have recently been achieved with similar varieties in Britain. Factors integral to the prairie environment are suggested to be the cause of this productivity differential. In particular, high soil moisture stress appears to be capable of severely reducing yields especially when experienced during the early phases of reproductive development. Satisfactory dry-mayEer production is not likely to be achieved if the seasonal soil heat accumulation (above 5 °C) is less than 1000 degree days. Low soil temperatures in the initial vegetative growth stage may also be responsible for the failure to achieve potential crop growth. Similarly high ambient temperatures (above 20°C) appear to be deleterious to crop growth.

Field-bean heat units were defined to facilitate the examination of potentially useful atmospheric heat on crop growth.

In the Highlands of Kenya every 1-week delay in planting maize after the onset of the rains reduces the grain yield by approximately 0·6 t/ha. No satisfactory explanation has been found for this phenomenon. A physiological growth study was made on four dates of planting per year over 4 years. Early growth rates and maximum crop growth rates showed a progressive decline with delay in planting which resulted in smaller plants at 5 weeks post-emergence and at 50 % tassel emergence in maize planted later. There was a strong relationship between the size of plant at tasselling and the final grain yield and a highly significant relationship (r = 0·94) between the size of plant at 5 weeks post emergence and the final grain yield. Other environmental studies showed that soil temperature at 7·5 cm, coupled with a soil moisture stress factor, largely controlled the dry-matter production rate during early growth, and consideration of the mean value of these two variables over the first 5 weeks of growth accounted for 70% of the variation of dry matter at 5 weeks post-emergence. It was further shown that 82% of the variation in final grain yield caused by date of planting could be accounted for by consideration of the mean value of these two variables during the first 5 weeks of growth.

Balance trials were carried out in which different amounts of Mg (0·44–2·9 g/day) were infused alternatively into the rumen and into the omasum, abomasum or duodenum of sheep consuming a low Mg diet (0·2 g Mg/kg D.M.). Absorption from the region between the infusion sites was measured from the change in urinary excretion and apparent absorption caused by changing the site of infusion.

Absorption was greater from a ruminal than from a comparable duodenal infusion. There was evidence, however, that the absorption mechanism within the stomach area was becoming saturated at the higher infusion rates in that the relationship between the amount absorbed and infused was curvilinear. The proportion of infused Mg which was absorbed from the stomach area fell from 0·61 to 0·14 as the infusion rate increased from 0·44 to 2·80 g/day.

The main site of absorption within the stomach area was the rumen; a small amount was absorbed from the omasum, but none from the abomasum. Positive differences between omasal and duodenal infusions were seen in plasma concentration at the two lowest and in urinary excretion at all infusion rates.

Increasing the amount of Mg infused into the duodenum caused an increase in plasma concentration and a linear increase in absorption.

When the ruminal and duodenal infusions were repeated with the sheep consuming hay, the results were similar but the proportion of infused Mg absorbed was reduced.

Measurements of 21 bone lengths and breadths were made on radiographs of 215 foetuses of known gestational ages ranging from 50 to 145 days obtained from 80 Finnish Landrace x Dorset Horn ewes. Number of foetuses per ewe varied from 1 to 5, but the main statistical analyses were based on the 22 sets of twins, 34 of triplets and 11 of quadruplets. Equations were fitted to relate each of the linear measurements to foetal weight alone, to foetal age alone, to foetal age together with number of foetuses, and to foetal age together with foetal weight. It was found that there were significant differences between the twins, triplets, and quadruplets in the lengths their bones attained at any specified weight or at any specified age but not when both weight and age were fixed. The relationships to weight and age jointly were significantly closer than to either of them alone even after allowing for number of foetuses. The mathematical model that fitted best was a modified Gompertz equation of the form

where ywas the measured length, w was the number of days prior to expected parturition, w was foetal weight, wu was an estimate of the expected foetal weight at time u, and P, Q, R and Dwere fitted constants.

The acute thermoregulatory responses of normally feathered (control) and poorly feathered laying hens were studied in the ambient temperature range from 0 to 38 °C.

Core body temperature in the poorly feathered birds began to fall at between 15 and 20 °C but this difference from the controls was significant only at 0 and 5 °C, when there was severe hypothermia. The temperature on the skin of the back was significantly lower at 20 °C and below, but the comb temperatures did not differ.

The rate of oxygen consumption in the poorly feathered hens was significantly higher than that of the controls at 30 CC and below; at the acclimation temperature (20–25 °C) the difference was about 62%. The rate of increase of heat production with falling ambient temperature was 2–6 W/ma/°C in the poorly feathered group and 1–0 W/ma/°C in the controls.

Absolute rates of evaporative heat loss did not differ between the two groups.

The ratio of the coefficients of dry heat transfer in the poorly feathered and control birds at 0–30 °C was 2–1:1.

Rectal, external auditory meatus and skin temperatures and panting rates were measured in native fat-tailed Awassi and imported German Mutton Merino (GMM) sheep. The Awassi evolved under desert conditions, have a localized fat deposit, coarse carpet wool, long pendulous ears and long, spiral horns (males). In contrast, the GMM evolved under temperate conditions, have well-distributed fat, medium fine wool, short, straight ears and are polled. The study was carried out during the summer in the northern part of the Negev desert.

The mean daily rectal temperature fluctuation was higher (P < 0·01) in the GMM than in the Awassi (1·78 °C v. 1·08 °C). The external auditory meatus temperature was lower than the rectal temperature by 1·5 °C in the GMM and by 1·7 °C in the Awassi, indicating a cooler brain temperature. The maximum skin temperature was similar to the maximum rectal temperature in both breeds, thus sweating was of little importance. The panting rate of the GMM increased fivefold (40·6–199·4 pants/min) whilst the rate of the Awassi increased fourfold (35·3–135·0 pants/min). There was no between-breed difference in either the rectal temperature or panting rate until 25–30 °C ambient temperature and it is thought that the higher rectal temperature of the GMM at this ambient temperature might have triggered off the higher panting rate. It seems that the GMM use panting to a greater extent than the Awassi whereas the Awassi dissipate heat through the skin more efficiently than the GMM. It is concluded that both breeds are thermostable, much of the between-breed difference in rectal temperature can be attributed to their anatomical differences.

Mesomorphic, stress-sensitive Pietrain pigs were found to have a lower insulin secretory response to intravenous tolbutamide, glucose and arginine, when compared with ectomorphic, stress-resistant Large White pigs. Pietrain pigs have also been observed to be insulin-insensitive in comparison with Large White pigs. The combination of a low production of and low sensitivity to insulin in the Pietrain breed could account for their enhanced sensitivity to lipolytic agents and for their reduced ability to deposit body fat.

Six experiments on winter wheat, three in 1974 and three in 1975, evaluated aqueous ammonia, aqueous urea and a solution of ammonium nitrate and urea, using ammonium nitrate granules as the standard. Aqueous ammonia and aqueous urea were injected 8–10 cm deep in bands either 25 or 50 cm apart during April. The ammonium nitrate/urea solution was sprayed and the ammonium nitrate granules were broadcast (a) partly in April and partly in May or (6) wholly in May. All were applied at 50, 75, 100 or 125 kg N/ha. Yields and % N in grain were measured and N removed by grain calculated. In two experiments lodging diminished yield and complicated the comparisons.

Elsewhere, aqueous urea and aqueous ammonia were of similar value, and each gave a larger yield when injected in bands 25 rather than 50 cm apart. Both fertilizers gave yields similar to those from broadcasting the ammonium nitrate granules, but larger yields than from spraying the ammonium nitrate/urea solution. Yields were slightly larger when divided rather than single topdressings were given, but % N in grain and the amounts of N removed were smaller. Yields and % N in the grain were smallest when the ammonium nitrate/urea solution was sprayed. The other three fertilizers were each of greater value judged by N uptake, the ammonium nitrate granules having a slight advantage.

Three constant and four variable heights of cutting were applied to swards of Italian ryegrass (Lolium multiflorum Lam.) cv. Aberystwyth S. 22 and perennial ryegrass (Lolium perenne L.) cv. Aberystwyth S. 23 for a period of 2 years. The treatments were initially given in the seeding year of the Italian ryegrass swards and first harvest year of the perennial ryegrass. The same swards were used throughout the duration of the two experiments. The three heights of cutting 3, 6 and 9 cm were defined by the mean lengths of tiller remaining after defoliation with a flail harvester.

The yield of dry matter (D.M.) was relatively low from Italian ryegrass cut repeatedly to 3 cm because many plants died. Higher yields were obtained by cutting repeatedly to 6 or 9 cm but only when the grass at the end of the season was cut to 3 cm. Italian ryegrass produced more herbage by variable than constant heights of cutting, especially when a lax cut occurred in mid-summer.

Perennial ryegrass gave higher yields of D.M. by constant low than high cutting, but there were no differences in yield when the constant high cut swards were closely defoliated at the end of each season. More herbage was produced by variable than constant heights of cutting in the second year, especially when several lax cuts occurred in the variable height of cut treatments.

As perennial ryegrass had a very prostrate growth habit in swards which received several close cuts tillers were not defoliated too severely. In contrast, Italian ryegrass remained erect in growth habit even in swards which were closely defoliated and thus tillers were cut more severely than those of perennial ryegrass. The need to measure accurately the actual lengths of tillers after defoliation is emphasized in height of cutting treatments.