1. Investigations on the fats from different tissues of forty-eight Romney ewes have shown that the iodine numbers of the fats cover a wide range from 32·7 for a perinephric fat to 83·7 for the fat from a metacarpal bone, while the percentage fat varies from as low as 3·8 in a longissimus dorsi muscle sample up to as high as 95·5 in a perinephric fat sample.

2. The mean iodine values of the fat and percentage fat respectively in the tissues examined were as follows: perinephric, 39·8, 88·1; loin subcutaneous, 41·7, 80·9; loin intermuscular, 44·4, 71·4; longissimus dorsi muscle, 53·1, 7·7; femur, 45·1, 39·8; tibia-tarsus, 54·3, 30·6 and metacarpus, 79·9, 24·3.

3. In the carcass tissues the muscle fat was significantly higher in iodine value than the fat from the fatty tissues. In the long bones analysed, the fats from the metacarpus had a highly significantly greater iodine value than was found for the other bones or carcass tissues. The fat from the tibia-tarsus was comparable in iodine value to that of the muscle tissue while the iodine value of the fat from the femur approached that from a fatty tissue.

4. A distinctive feature of the fats examined was their variability in iodine value. The values varied between animals by 15·3 units for perinephric fat, by 13·0 units for subcutaneous fat, by 16·9 units for intermuscular fat and by 12·4 units for muscle fat.

5. The present results for the iodine values of the fats of Romney ewes generally agree with those obtained by Callow (1958) for Suffolk lambs. However, whereas in Suffolk sheep in accordance with the temperature theory of Henriques & Hansen (1901) the subcutaneous fats have higher iodine values than do the intermuscular fats, in the Romney sheep studied the reverse holds.

1. Data on the dry-matter production of five grass species (each sown with white clover), over the period 1954–56, at six levels of compound fertilizer application, are reported. Perennial ryegrass (S. 101), meadow fescue (S. 215), timothy (S. 48), cocksfoot (S. 26) and bent (N.Z. browntop) were sown in 1953 at appropriate seed rates, each with 2 lb. per acre S. 100 white clover. The fertilizer treatments were 0, 1, 3, 5, 7 and 9 cwt. per acre of a compound of composition 10% N, 4% P2O5 and 9·5% K2O, applied in the early spring of each of the years 1954–56. The swards were cut three times a year in 1954 and 1956, but only two cuts were possible in 1955.

2. The timothy mixture gave the highest total production of dry-matter over the 3 years, the bent and perennial rye-grass mixtures giving the lowest total productions. Differences between mixtures in annual yield varied in sign and in magnitude from year to year. For example, bent gave the lowest yield in 1954, but outyielded the meadow fescue and the cocksfoot mixtures in 1955, and the perennial rye-grass mixture in 1956. As regards the distribution of dry-matter production over the season, it was found that bent differed from the other mixtures in that a higher proportion of its annual yield was produced at the second and third cuts.

3. There were significant linear relationships of dry-matter yield to fertilizer application rate in most of the data. On average over the 3 years, 1·6 cwt. of dry-matter were produced for each cwt. of spring applied fertilizer in the first cut, 0·7 cwt. per cwt. of fertilizer in the second cut, while very small and non-significant responses were found in the third cut. There was no evidence of systematic differences between grass mixtures in response to fertilizer level.

4. The yield of clover dry-matter in 1956 (the third harvest year) was least from the cocksfoot and timothy swards, and was significantly and linearly depressed by fertilizer application in all three cuts.

The effect of fertilizers in increasing the yield of clover seed was examined by a series of manurial trials. The initial mineral status of the crop and the extent of the uptake of the applied nutrients were determined by analyses of the leaf. The techniques for sampling and analysing leaves to determine mineral status are described.

The high yields of seed and lack of response to fertilizers in trials at Cambridge led to their being repeated at Saxmundham on land known to be extremely deficient in minerals. Even then there was a response only to phosphate which although significant was small.

Leaf samples were also collected from commercial crops of red clover in 1955, 1956 and 1957. The analyses of these samples indicted that none of them was as deficient as the crops at Saxmundham, and no relationship was found between mineral status and seed yield.

It is concluded that yields of red clover seed in Eastern England are not likely to be increased materially by the application of fertilizers.

1. Pure swards of S. 48 timothy and S. 215 meadow fescue receiving approximately 52 or 156 lb. N per acre over a period of 8 months were cut (a) at anthesis and twice thereafter or (6) every 4 weeks. The number and weight of tillers and leaves and annual plot yields were determined.

2. Tiller numbers rose to their highest in spring and then declined throughout the summer. The higher rate of nitrogen increased tillers in the meadow fescue more than in the timothy; the system of frequent defoliation resulted in enhanced production of tillers in the low nitrogen swards of both species, so that maximum populations within a species were similar under the two levels of nitrogen.

Bovine spermatozoa aged for 6–7 days at room temperatures (18–30° C.) in a coconut milk extender retained their fertilizing capacity. However, their fertilizing ability appeared to be impaired by environmental hazards in the form of oxygen damage, exposure to visible light, and temperature shock. Protective measures developed and used in the preparation and in the storage of the sperm suspensions to minimize premature loss of sperm function involved the addition of catalase and egg yolk to the extender and the maintenance of cell suspensions in the dark in vials containing a minimal air space. The experimental evidence obtained with this improved coconut milk extender established its ability to support and sustain the fertilizing capacity of bovine sperm for 6–7 days at room temperatures at a level comparable to the fertilizing capacity of refrigerated sperm in milk-glycerol or egg yolk-citrate-glycine extenders. The economic importance of this room temperature diluent is suggested by the fact that it eliminates the costly refrigeration required to maintain stored and shipped bovine semen at 5° C.

Coconut milk extender modified by the addition of 5% egg yolk also proved to be a satisfactory storage medium for sperm at low temperatures. It was found to be superior to both egg yolk-citrate and skim-milk extenders in conserving motility at 5° C. The fertilizing capacity of Ayrshire and Brown Swiss sperm stored at 5° C. in coconut milk extender which contained 15% coconut milk and 5% egg yolk compared favourably with the fertilizing capacity reported for sperm stored at 5° C. in other more widely used diluents. The number of motile sperm recovered from this extender after freezing to −79° C. was comparable to the number of motile sperm recovered from the egg yolk-citrate and skim-milk test diluents. The results of this study indicate that coconut milk extender is a versatile, easily prepared medium which can be used to preserve functional sperm over a wide temperature range.

1. An experiment has been carried out to compare the results of feeding the B-group diets of Parts II and III of this series to ewes during pregnancy and lactation.

2. The ewes fed a diet containing maize in place of dried molassed sugar beet pulp again maintained better bodily and skeletal condition.

3. The basis for other experiments in this series is discussed.

1. Effects on productivity and skeletal mineralization of high as opposed to moderate levels of protein and, or, energy intake by the ewe during pregnancy and lactation in the presence of adequate calcium, phosphorus and vitamin D have been studied.

2. Two experiments were undertaken. One experiment used 4½-year-old Cheviot ewes and the other used 3½- and 4½-year-old Scottish Blackface ewes. Weight records, blood samples and in vivo and flesh-free radiographs were obtained, and bone ash determinations were carried out.

3. The results showed that contrary to indications from earlier experiments in this series superiority in ewe weight, lamb growth, and mineralization of the ewe skeleton did not necessarily result from raising the protein and, or, energy values of the feed above the ‘moderate’ level.

4. Discrepancies between the in vivo and flesh - free radiological assessments were noted for consideration.

1. To evaluate selection criteria in grass breeding, a series of investigations was conducted measuring plant performance in a wide range of field environments.

2. This paper reports on the behaviour of one variety of Lolium perenne, S. 24, grown in a logarithmically related series of densities and frequently defoliated for 2 years. Half the plots received only natural rainfall, the rest were irrigated so that the calculated soil moisture deficit did not exceed 2 in.

3. In 1958, with little effect of irrigation, swards yielded most per unit area, widest spacing (24 in.) least; there were no significant differences in yields from the other densities (3, 6 and 12 in.). In 1959, when yields were lower, irrigation increased production in all plots, the higher the density the greater the increase. In contrast to 1958, over the range of spaced densities, the higher the density the greater the yield. Individual harvests did not always conform to the annual pattern.

4. Lowest mean production per plant was from broadcast plots in both 1958 and 1959, yields of plants from 3, 6 and 12 in. plots showed a linear increase with a reduction in density, those from 24 in., though heaviest, yielded less than linear expectation. In 1959 irrigation increased yields per plant.

5. Of the components of yield, number of sterile tillers gave the best estimate of total fresh weight (95·3% reliability). However, total number of tillers (sterile plus fertile) was almost as efficient (94%). Tiller weight was a much less reliable index.

6. The results and their value in establishing efficient criteria for selection in grass breeding are discussed.

Bleasdale & Nelder (1960) refer to several models which have been used in studying the relationship of yield and density in crop plants and indicate that they regard as most satisfactory the equation:

where ω = yield/plant, ρ = number of plants/unit area and A and B are constants. The estimation of the constants for any given case is a very unattractive arithmetic exercise requiring a fairly large number of observations and a tedious iterative calculation; Nelder (1961) has discussed the least squares fit with the equation in the form

which may readily be derived from (1) by the substitutions

The data in the present case do not justify attempting this process but some progress can be made by the substitutions

by means of which it is easy to derive from (1) that

There has been much speculation on the underlying mechanism of pregnancy toxaemia in the ewe (e.g. Reber, 1957; Kronfeld, 1958) and it is generally thought that the condition is a consequence of the failure of the ewe's metabolism to adapt to the increasing hexose demands of the foetus. Insufficient hexose is considered to be produced from dietary propionate and from the deamination of amino acids, with the result that liver glycogen is exhausted, citric acid cycle components are depleted and the resulting failure to oxidize activated acetate gives rise to ketone bodies. If this were the whole sequence of events the clinical symptoms should be reversible by the administration of glucose or glucogenic substances, orally or parenterally. Unfortunately clinical experience is that the condition shows a poor response to glucose therapy and the mortality of field cases is extremely high.

1. The composition of the bacterial population in the rumen of adult merino wethers conditioned to a diet of poor teff hay was studied during three consecutive periods of 60, 109 and 42 days when the ration was 1200,600 and 300 g. per day, respectively.

2. In all three periods there was no significant difference between the three sheep with regard to either the viable counts of the functional groups of bacteria fermenting cellulose, starch, glucose, xylose and lactate or the percentage proportions of the different morphological types occurring in each group.

3. The reduction of food intake had little or no influence on either the numbers or the morphological types of bacteria in each functional group.

4. The animals lost weight at approximately the same rate throughout the three periods of the experiment which was ended when they were in a state of prostration.

5. These results suggest that, providing the diet is changed only in respect of quantity, important functional groups of rumen bacteria can survive at levels of food intake which are insufficient for the survival of the animal.

1. The composition of the bacterial populations of the rumen of three sheep on lucerne hay was very similar with regard to both the levels of the functional groups which ferment cellulose, starch, glucose and xylose and to the morphological types of which they were composed. The lactate-utilizing bacteria showed more variation in numbers between individual animals.

2. The rumen flora of lucerne hay fed sheep differed from that of sheep on teff hay not only in significantly higher counts of the carbohydratefermenting bacteria in the former group, but also in distinctive types of cellulolytic bacteria.

3. The short- and long-term variations in number of cellulose digesters found earlier in a sheep on a practical diet of lucerne hay were not markedly reduced by feeding the same animal lucerne hay of constant composition.

4. A correlation appeared to exist between the protein content of the lucerne hay and the level of the lactate-fermenting bacteria in the rumen.

5. The changes in the viable counts of the bacteria capable of fermenting cellulose, starch, glucose and lactate during the first 8 hr. after feeding a ration of lucerne hay were small compared with the in vitro rate of multiplication of a pure strain of cellulolytic cocci isolated from a sheep on the same diet. This is regarded as further evidence in favour of the notion that the rumen contents, particularly of animals on high roughage diets, approximates to a continuous culture system.

The composition and feeding value of the common heather has been extensively studied by Thomas et al. (1934, 1935, 1953, 1955, 1956). He has shown that as the heather ages the protein content declines. Thus, samples from 2-year-old growths had a crude protein content (on a dry-matter basis) of 11·9% while that of growths 8 years old was 6·5–6·9%. Little or no information, however, appears to be available on the quality of heather protein, as judged by its amino acid composition.

1. A group of four Ayrshire and four Friesian cows was strip grazed on a cocksfoot-dominant sward while a second, similar group was zero grazed on herbage cut from the same field. The experiment consisted of five 10-day periods, two in the spring and three in the summer.

2. The intakes of all cows were calculated from values for faeces output, estimated by using chromic oxide, and for herbage digestibility, estimated from faeces nitrogen. The regressions used for predicting digestibility were determined with the zero-grazed cows, digestibility coefficients being calculated from measured intake and estimated faeces output values.

3. Over the whole experiment there was no difference between treatments in milk yield, herbage digestibility or intake. The solids-not-fat content of the milk of strip-grazed cows was significantly higher than for zero-grazed cows.

4. In both spring and summer the increasing maturity of the herbage caused declines from one period to the next in herbage digestibility and intake, and there were declines also in milk yield and solids-not-fat content. The declines were greater for the zero-grazed cows, apparently because they, unlike the strip-grazed animals, were unable to select the more digestible and palatable components of mature herbage. The effects of selective grazing on digestibility, however, were evidently small, for the difference in between the treatment groups was never greater than one unit.

5. The estimated energy intakes of both treatment groups corresponded quite well with their theoretical requirements of energy for maintenance, milk production and live-weight gain, and there was no evidence of the energy cost of free grazing being appreciably greater than that of zero grazing.

A flock of 320 Border-Leicester × Merino ewes was used to study the effects of pre-flushing and flushing treatments on subsequent lambing performances during the years 1958, 1959 and 1960. The flock was kept on non-irrigated perennial pastures in southern Victoria.

In 1958 groups of ewes that lost a mean of 17, 5 and 0 lb. during the 4 weeks immediately prior to flushing gave average lambing percentages of 94, 98 and 101, respectively.

In 1959 and 1960 flushing for a period of 3 weeks immediately prior to joining produced increased lambing percentages of 13 and 9, respectively. These increases were due almost entirely to increased twinning rates. The response to flushing was not related to the live-weight changes that occurred during flushing. However, the live-weights of the ewes at joining, and, to a lesser extent, before flushing, were related to subsequent lambing performances. The heavier ewes gave more twins than did the lightweight ewes.

Three grass/legume pastures were evaluated under Northern Rhodesian conditions.

A plot trial measured the herbage yields of Stylosanthes gracilis, velvet beans (Stizolobium deeringianum) and giant Rhodes grass (Chloris gayana) grown as pure stands, and in a mixed association with Rhodes grass. The herbage was harvested for 3 years, and the plots were then planted with a maize crop to test any residual effects.

After the establishment year, the D.M. yields, and especially the C.P. yields of the legume and grass/legume treatments, were markedly superior to grass alone. The increased yield of the grass/legume mixtures was due to the net gain contributed by legume herbage. There was no evidence of an underground transference of N from the legume to the associated grass.

Although there was no measurable treatment effect on soil N and C, the maize following the legume and grass/legume treatments had a higher leaf N level, and approximately double the yield, compared with the maize following the grass-alone treatments.

There were no significant differences in cattle weight gains when Rhodes grass alone, Rhodes grass/Stylosanthes, Rhodes grass/velvet beans, and Rhodes grass/pigeon peas (Cajanus cajan) were utilized as hay and foggage in the dry season.

Digestibility trials showed mature Rhodes grass hay to be a submaintenance feed, deficient in dietary protein. The addition of Stylosanthes raised the herbage digestible C.P. fourfold. The Rhodes grass/Stylosanthes hay was a maintenance feed.

The N yield of the grass/legume mixtures, although low by temperate standards, was 2½ times the N yield of grass alone. The potential value of a tropical grass/legume pasture will depend on the efficiency of the legume to fix N.

1. The behaviour of six grade and six zebu steers in a temperate environment was compared with their behaviour when moved to a tropical climate.

2. Reaction of both groups to the heat was demonstrated by seeking shade, increased water consumption and an alteration of grazing times. The similarity in their behaviour was, however, the most striking feature. The grades lay down slightly longer than the zebus, but showed no other differences and were not apparently distressed by heat.

3. The greatest difference found was in ruminating times and it is suggested that differences in food conversion may be more important than differences in heat tolerance, provided the animals are given the opportunity to adapt themselves fully to their environment.

1. A number of penned feeding and grazing experiments are described in which sheep and cattle, fed diets of low-quality roughage, were given supplements of urea and molasses, or urea and starch.

2. Starch was unsatisfactory as a source of supplementary carbohydrate, and it was concluded that this was mainly due to its low palatability. Molasses added without urea to a diet of straw for penned sheep increased intake and reduced the rate of live-weight loss in one experiment, but had no effect in another.

3. In general, supplementing low-quality rough-age with urea and molasses in both penned feeding and grazing experiments increased food intake and reduced the rate of live-weight loss. A supplement of urea alone increased food intake, but did not affect live-weight loss. The addition of ethanol or phosphoric acid to urea-molasses supplements had no additional beneficial effect. Supplementation with urea and molasses increased wool growth, but this increase was not always significant.

4. The general effect of urea on rumen contents was to increase pH, V.F.A. and ammonia N levels; the effect of molasses was to decrease pH and ammonia N levels, and increase V.F.A. levels.

5. Spraying of dry, standing herbage with urea and molasses increased the crude protein (N × 6·25) content, but this effect disappeared in 3–4 days. Sprayed herbage was markedly preferred by grazing animals, and generally one third of the sprayed herbage was removed within 24 hr. of spraying.

6. The advantages and disadvantages of the pasture-spraying technique, and the possibilities of other methods of feeding supplements containing urea to grazing animals, are discussed.

7. In no experiment where unsupplemented animals were losing weight did urea and molasses supplementation cause substantial increases in weight. It is concluded that the main value of supplementing low-quality roughage with urea and molasses would be for the survival, and possibly the maintenance, of animals.