Digestibility, performance and carcass analysis trials were used to compare the nutritive value of two diets, containing 78% of either cooked potato flake (diet CPF) or maize meal (diet M). Diet CPF had slightly lower values for gross energy (GE) and nitrogen (N), markedly lower values for ether extractives and crude fibre, a slightly higher lysine concentration and a markedly higher potassium concentration.

Apparent digestibility coefficients were determined with ten piglets weighing 22 kg; digestibility values for GE and N were respectively 0·95 and 0·91 for diet CPF, and 0·84 and 0·88 for diet M. Digestible energy (DE) and digestible N (DN) values were 10·2 MJ and 26·9 g/kg dry matter for diet CPF, and 15·3 MJ and 27·9 g/kg dry matter for diet M. The performance of 30 piglets grown from 21 to 53 days of age and from 6·0 to 13·1 kg was similar for each diet, as were the empty body, water, N, lipid, ash and GE gains of 18 of these piglets. The efficiencies of conversion of nutrients ingested from diet CPF into the components of body gain were for GE, DE, N and DN; 0·21, 0·22, 0·48 and 0·52 respectively. Corresponding values for diet M were 0·17, 0·21, 0·38 and 0·44.

The greater efficiency with which the nutrients in the potato flake were used thus resulted in a growth response which was at least equal to that of the maize meal.

Two breeds of zebu viz. Hariana and Sahiwal were examined for the possible existence of red cell K+ polymorphism. All the animals examined appeared to be LK type. However, red cell K+ concentration varied rather widely between 7 and 50 m-equiv/1. Within the major LK type three distinct subtypes, tentatively designated as low low (LLK), medium low (MLK) and high low (HLK) were observed. The mean red cell K+ concentration in the various subtypes in the same order were 12·5, 19·5 and 38·0 m-equiv/1 respectively. LLK animals were significantly more frequent in the Sahiwal than in the Hariana breed. The possible genetic basis of the occurrence of these subtypes within the major LK type is discussed.

LLK animals had significantly higher pcv, Hb and RBC, than MLK animals. The WBC and plasma protein values were also higher, though not significantly, in the former group. In addition, animals of the LLK subtype showed consistently lower rectal temperature at comparable levels of respiratory effort under conditions of thermal stress than MLK animals.

A technique is described for the in vivo estimation of the rate of production of bacteria in the rumen of buffalo calves. The animals were given their daily ration in 12 equal amounts at 2-h intervals. The bacterial cells from the rumen were labelled either with 14C or 36S by in vitro incubation in the presence of [U-14C]DL-leucine or 35S-sodium sulphate. Labelled bacterial cells were injected in a single dose into the rumen. Samples of the ruminal fluid were drawn at various time intervals for 9 h and the specific radio-activity of the bacteria determined. The dilution in the specific radioactivity was used to calculate the turn-over time and rates of production of bacteria in the rumen. The average turnover time was 308 min. The production rate of bacteria averaged 211 mg/min (20·3 g/mole VFA produced).

Comparison of summer, winter and spring-grown cabbage showed that carotene synthesis differed considerably. Spring-grown cabbage was found to produce a peak of carotenoids during the first week of growth, and this decreased after one month. In comparison, winter-grown cabbage was still producing more carotenoids after 1 month and came to a peak of carotenoid production between 1 and 2 months. The winter-grown cabbage plants were maintained for 12 months and it was found that oxidative processes occurred at a later date than in spring- and summer-grown plants. It is shown that total carotenoids and interconversions of carotenoids are a useful indication of the metabolic processes, including oxidation and degradation of carotenoids, occurring in maturing and senescing plants.

The effect of variation of the vitamin A potent carotenoids in the cabbage, and the increased spring production of carotenoids in cabbage, are discussed in relation to the life style of P. brassicae.

Blood samples were taken from groups of lactating and non-lactating cows on three occasions from each of 24 commercial dairy herds sampled eight herds at a time at 6-weekly intervals throughout 1972. The blood samples were analysed for packed cell volume, blood glucose and haemoglobin, and for the serum concentrations of albumin, total protein, urea nitrogen, Ca, inorganic phosphate, Mg, K, Na, Cu, and Fe.

Clear seasonal patterns were evident for packed cell volume and the mean concentrations of urea nitrogen and haemoglobin each of which were highest during the summer months. The effect of season on the concentrations of the other constituents was smaller. Mean values of packed cell volume, haemoglobin and Fe were consistently higher in the non-lactating cows than in the lactating cows. Mean concentrations of Mg were lower in the blood of non-lactating cows throughout the year; Cu concentrations followed a similar trend in the autumn and winter.

There was evidence of overall herd differences regardless of season, in particular for Cu, globulin, Fe and urea nitrogen concentrations.

Four groups of six 18-month-old wethers were fed a diet of hay ad libitum with a pelleted ground barley supplement for 70 days. The control group received no further dietary supplements and the sodium content (0·46%) was above that recommended by published standards. Groups 2, 3 and 4 received supplements of sodium chloride, mixed and pelleted with the barley, to provide a final dietary concentration of 1·7, 2·5 and 3·1% sodium respectively.

Dry-matter intake, dry organic-matter intake and digestible organic matter in dry matter (DOMD) were significantly reduced (P < 0·01) at the highest sodium intake. There was a reduction in live-weight gain and efficiency of utilization of digestible organic matter with increasing sodium chloride supplementation, with significant differences (P < 0·05) between the highest and lowest sodium intake groups.

There were no consistent or significant changes in the serum concentrations of sodium or potassium following sodium chloride supplementation, but serum calcium and magnesium levels were significantly lowered as a result of sodium chloride supplementation.

Sodium chloride supplementation improved the apparent availability of sodium, potassium, magnesium and calcium but reduced that of phosphorus and nitrogen. The retention of Na, K, Mg, P and N was lower at the highest sodium intake but Ca retention was higher. Urine volume and excretion of Na, K, Mg, Ca, P and N increased with sodium chloride intake.

Photosynthetic rates of flag blades were measured in eight wheat varieties. The differing rates observed were not correlated with winter or spring habit, plant height or gibberellin sensitivity. The rates were correlated inversely with the flag blade area in these varieties.

Applied gibberellin increased photosynthetic rate and the maximum increase was 17% in the variety with the lowest control rate. However, the varieties did not differ significantly in their response to the hormone.

In 92 field experiments in Tanzania's major cotton-growing area south and east of Lake Victoria mean yield without fertilizer was nearly 900 kg/ha of seed cotton. The mean direct effect of 224 kg/ha of single superphosphate with 202 kg/ha of ammonium sulphate was 380 kg/ha of seed cotton; with twice as much fertilizer the increment was 525 kg. First and second residual responses made important contributions to the total effect of superphosphate. In most zones the response to each fertilizer was large but in Nassa response to superphosphate was small; in Nzega yields were small and there was no response to ammonium sulphate, perhaps because Calidea dregei caused abscission of bolls; on the acid soils of Ukerewe Island yields and responses to superphosphate were small.

Data are given to show the average amounts of plant nutrients in the soils most used for cotton. Correlations of yields with soil chemical data suggest that some soils lack enough calcium for large yields. A long-term experiment at the Ukiriguru research farm (Le Mare, 1972) showed that productivity of impoverished soil growing cotton every year was recovered and improved by lime with phosphorus and nitrogen fertilizers: the experiments throughout the cotton area indicated that those results were widely relevant.

A model is presented which considers the effects of competition between pairs of individuals in binary mixtures. Competitive effects are defined in terms of two parameters; a monoculture effect (Mo) which measures competition between like individuals and a mixture effect (Mi) which relates to competition between unlike individuals. If the data from a particular density replacement series conform to the proposed model the ratio of Mi to Mo can be used to determine whether it would be more advantageous to grow a mixture of the two components concerned or a pure stand of the better component. Where appropriate the optimal composition of the mixture may also be estimated. Theoretical considerations suggest that a 50:50 ratio only represents the optimal composition of a mixture when the two components possess a similar expression for the character concerned.

The model has been applied to dry weight data collected over two growing seasons from a glasshouse experiment which contained 5 genotypes of Lolium perenne grown as monocultures and in all 10 binary combinations. Each combination was represented by three mixture proportions. For the majority of these density replacement series the model was satisfactory, with mixture effects tending to be of greater significance during the first of the two growing seasons. Failure of the model was in general due either to a specific form of competition, which maintained the performance of the mixtures at the level of the better monoculture, or to the presence of more complex forms of competition.

The implications of this model for the development of productive herbage mixtures are briefly discussed, whilst the possible effects of invasion by unsown grass species upon the productivity of a pure sward are also outlined.

One side of the carcasses from 145 beef animals was weighed, measured and quartered. Measurements were made in the exposed eye muscle region which was then photographed. Measurements were made from the photographs and the quarters were jointed. Each joint was separated into lean, bone, intermuscular fat, subcutaneous fat and ‘other tissues’. The material is described in terms of breed, sex and side weight. Details of the measurements made are given and the methods of jointing and tissue separation are described. The latter was different in three groups of 30, 72 and 43 animals. The overall carcass composition in terms of lean, bone, intermuscular fat plus ‘other tissues’, and subcutaneous fat for the three groups is summarized and the reasons for including ‘other tissues’ with intermuscular fat are given.

The data described in Part I of this series (Pomeroy et al. 1974) were analysed by regression methods, to see how, and how well, estimation of total carcass composition (simplified to bone, lean and fat) can be achieved in situations where the beef side cannot be fully dissected, but can be measured as an intact side, quartered and the cut surface photographed, or where sample joints can be dissected. Equations are given, based on the largest group (Group II, 72 animals) of the three previously described, and the advantages to be gained from quartering the carcass, photographing the cut surface, and dissecting a sample joint are quantified. These equations have been tested by applying them to the other two groups, I and III of 30 and 43 animals.

A technique is described in which cereal seedlings after germination and hardening under controlled conditions in a growth chamber were subjected to freezing in tubes immersed in a solution of ethylene glycol. Susceptibility to freezing was estimated by measuring electrical conductance on the linear 0–100 scale of a standard ‘Avometer’ using platinum probes inserted near the base of the lamina of the first leaf. The use of the technique is illustrated by two experiments with winter barley cultivars chosento represent a wide range of winter hardiness. Although significant cultivar differences in mean conductance existed prior to freezing, adequate differentiation was obtained by measurements after freezing only. The differentiation of these cultivars on mean conductance values after freezing was well correlated with their established winter hardiness.

It is concluded that the technique is sufficiently sensitive for the preliminary screening of early generation material but that, because of significant cultivar × hardening-duration interactions, advanced breeding lines should be tested over a range of hardening and freezing regimes.

Two groups of five and six ewes were studied through two separate winters by monthly wool and skin samples in an attempt to follow the changes leading up to fleece casting, which occurred extensively in only two animals.

Although no fleece break was observed, the animals that cast most showed the biggest decrease in fibre diameter. They also had a decrease in staple length where the wool was not cast.

Follicle inactivity increased during the observations reaching a peak at the end of the winter, and the animals that cast most had most follicle inactivity. It is concluded that casting was associated not with fleece break but with increased follicle inactivity coupled with premature release of the fibres from the follicles.

Border Leicester ewes were kept in three contrasting photoperiodic environments, the rhythm at latitude 30° 32′ S (group 1) - 12 h light: 12 h dark interrupted by 6 weeks of continuous light (group 2a) and 12 h light: 12 h dark (group 2b) - from August 1972 to September 1973. In group 1 all ewes exhibited oestrus compared with 87·5% and 57·1% in groups 2(a) and 2(b) respectively. The mean number of oestrous periods per ewe ranged from 4·4 in group 1 to 3·0 in group 2(a) and 1·0 in group 2(b). It is concluded that the non-fluctuating light rhythm had an adverse effect on the reproductive potential of the treated groups and that Border Leicester ewes are dependent on a fluctuating light rhythm for normal reproductive function.

The relationship between the voluntary dry-matter intake of grasses and their in vitro digestibility (DOMD), chemical composition and susceptibility to enzymic hydrolysis was examined in two experiments. The grasses were artificially dried and represented a range of species and varieties cut at various growth stages.

In both experiments some 70% of the observed variation in intake could be attributed to differences in in vitro digestibility between the grasses and between the growth stages when harvested. Estimations of acid detergent fibre, pepsin solubility and cellulose generally accounted for less than 70% of the variation in intake.

The enzyme digestion techniques, on the other hand, accounted for up to 79% of the variation. The content of enzymically unhydrolysable cell wall gave the highest correlation with voluntary intake (r = −0·88 and −0·89, residual standard deviation 5·5 and 6·2, for the two experiments).

It is concluded that simplified techniques based on cellulase digestion of plant material may be advantageously applied to breeding programmes with the expectation of identifying material high in digestibility and with good intake characteristics.

The wool weight/m2 of LK progeny arising out of LK × LK matings (approximately a quarter were HK and were excluded) and HK progeny arising out of HK × HK matings (all were HK) of two coarse-wool producing breeds of sheep, Marwari and Magra, were compared with the mid-parent values. LK progenies produced significantly more than the mid-parent value in both the breeds, but there was no increase in HK progeny. The difference in wool weight between the HK progeny and their mid-parent value tended to be less for Marwari whereas it was much less for Magra breed.

The results suggest that improvement in wool weight of sheep can be made by maintaining LK stock and mating LK × LK, culling the HK arising out of these matings in each generation.

The effect of sowing date and nitrogen on tillering patterns, survival and contribution of reproductive tillers to grain yield of standard and Mexican wheat cultivars were studied for two seasons.

Maximum number of tillers/plant, 3·2–4·5, was observed after 40 and 27 days from sowing for 1970–1 and 1971–2 respectively. The number of ears/plant was 1·4 at the end of the growing season. Varieties differed in tillering, and LRN10 and Giza 155 produced more reproductive tillers than Falchetto and Mexipak. Nitrogen application increased tillering efficiency, i.e. ratio of fertile to total tillers produced. Only 26% of tillers appearing in the axil of the first true leaf (T1) and 10% of tillers in the axil of the second true leaf (T2) survived to produce ears. The high mortality of tillers was attributed to high air temperature prevailing during the growth period (33 °C by day; 18 °C by night). Eared tillers did not die and were self supporting because of the photosynthesis by the ear.

Grain weight/tiller was positively correlated with tiller dry weight at heading, r= 0·76–0·96. Main shoots contributed about 81% of the total grain yield and 19% came from T1 and T2 tillers.

From monogerm sugar-beet seed as harvested non-viable fruits have to be eliminated, multigerm ones rejected and the size made sufficiently uniform for use in precision drills. Seed which had been gently rubbed to remove some of the cortex was graded for diameter, thickness and by aspiration, either singly or in combination. Effects of grading were determined by laboratory germination tests, radiography and field sowings in which seedling emergence and crop growth and yield were recorded.

Grading by thickness was effective in removing multigerm fruits. Grading by aspiration and diameter rejected non-viable seed and reduced the variation in size. By combining all three grading methods, samples of seed of 80% germination and 90% monogermity were produced, provided the seed lot as threshed gave at least 50% germination. True seed weight increased with fruit diameter but only the first aspiration was effective in removing light true seeds. Radiography showed that both aspiration and, to a less extent, grading by diameter were effective in removing most empty fruits but neither eliminated those with shrivelled seed. The field experiments confirmed that increase in fruit diameter or aspiration gave more seedlings. Even at uniform, high plant density, sugar yields were less from the smallest (less than 3 mm diameter) than from the other grades of seed. The initial aspiration also improved sugar yield but further aspiration decreased yield.

Fifty-nine Scottish Blackface female sheep were used to measure the effects of age and state of permanent incisor dentition on the loss of body reserves during pregnancy and lactation and on the ability to replenish them during the dry period, while grazing hill pastures. There were 27 6½-year-old sheep (11 with sound mouths and 16 with broken mouths), 16 5½-year-old sheep (with all permanent incisors clipped to gum level) and 16 2½-year-old sheep. Samples of sheep from each group were slaughtered at the beginning of pregnancy and in mid-lactation, and samples of those with broken mouths and of 5½-year-old and 2½-year-old sheep at the end of the subsequent dry period. Carcasses were dissected into soft tissue and skeleton fractions and the changes in chemical composition of the former are presented. The sheep were weighed at approximately monthly intervals; lamb birth weights and growth rates to 6 weeks of age were recorded.

There was no evidence that broken mouth or the clipping of the teeth impaired the ability of sheep to maintain body weight in early pregnancy, but there was evidence that sheep with broken mouths lost most weight in late pregnancy. There was also evidence that sheep with broken mouths may have poor milk yields as judged by the growth rates of their lambs but more data are needed to establish this conclusion.

The young sheep were most able and the sheep with the broken mouths least able to resist catabolism of their soft tissue protein during pregnancy and lactation. The losses amounted to 18, 20, 21 and 30% in the 2½-year-old, 5½-year-old and 6½-year-old sheep with sound mouths and with broken mouths, respectively. The young sheep replaced their protein reserves more rapidly than the sheep with broken mouths. It is suggested that the ability to restore body protein may be related to maturity.

There was evidence for a redistribution of protein in the body of undernourished sheep in mid-lactation. The soft tissues were overhydrated at this time but much of the fluid which accumulates during pregnancy had apparently cleared.

The chemical composition of the skeleton, mandible and 4th lumbar vertebra of 59 Scottish Blackface female sheep from a ‘broken mouth’ farm was determined. There were 27 6½-year-old sheep (11 with sound mouths, 16 with broken mouths), 16 5½-year old sheep (with loose incisor teeth which at the outset of the experiment were clipped to gum level) and 16 2½-year-old sheep. Sheep from each group were slaughtered at the beginning of pregnancy and in mid-lactation and from those with broken mouths and from the 5½-year-old and 2½-year-old groups at the end of the subsequent dry period. The sheep grazed hill pastures and received an energy supplement during late pregnancy and early lactation.

There were no differences between the 6½-year-old sheep with broken mouths and those with sound mouths in total skeletal mineral content or in the density of ash (ash: volume ratio) or organic matrix (organic matter: volume ratio) in the mandible and lumbar vertebra at the beginning of pregnancy or in mid-lactation. Nor were there differences in the density of ash or organic matrix between any groups, although the skeletons of the 6½-year-old sheep were larger. The lumbar vertebra, which is rich in cancellous bone, had a lower ash and organic matrix density in the 5½- and 2½-year-old sheep. It is suggested that bone mineralization may proceed slowly on such hill pastures.

The rates of repletion of the skeleton during the dry period, 0·35, 0·47 and 0·66 g Ca/day, respectively, in the 6½-year-old sheep with broken mouths, 5½-year-old and 2½-year-old sheep were much slower than rates given in the literature for sheep under controlled conditions. It is suggested that factors other than the major nutrients, protein, Ca and P, may be limiting repletion of the skeleton.

Recovery of the ash density of the vertebra was not complete at the end of the dry period. This was especially so in the sheep with broken mouths and resulted mainly from a failure to replace bone organic matrix.

The implications for the development of broken mouth of cyclical changes in the density of cancellous bone and of evidence that the ability to maintain and to remineralize the skeleton deteriorates with increasing age, are discussed.