The Journal of Agricultural Science

Data from the experiment described in the first paper of this series were subjected to regression analysis. Lean meat and live-weight gain response to both lysine and crude protein intake was almost linear in period 1 but in later periods little response was evident. Response of live-weight gain to increased energy was continuous though diminishing in the later periods. In periods 1 and 2 lean gains showed positive though diminishing response to energy.

In a multivariate regression analysis it was clear especially for younger pigs that the response to dietary lysine for both live-weight and lean meat gains is influenced by the dietary level of crude protein and the energy intake. Separate multivariate analysis for each sex indicated that females are more efficient converters of lysine and energy into live weight and lean meat. Also an interaction between sex and dietary lysine level was suggested.

A methodology for an economic analysis taking the joint objectives of total cost of production, speed of grain and quality of gain is established as a basis for design of high profit system of production.

The efficiency of the utilization of the energy of casein in adult fowls at different feeding levels both for maintenance and for lipogenesis, was studied. The casein was utilized for maintenance with an efficiency of 66·6 ± 1·3% of the gross energy and of 83·7 ± 1·4% of the metabolizable energy. For lipogenesis efficiencies were 51·6 ± 2·15%, and 61·3 ± 2·6% respectively.

Bulk harvests of primary growth were made at intervals during the spring and summer of 2 consecutive years from an ungrazed area of lucerne (Medicago sativa) and the digestibility by sheep was measured. At the same times, shoots of known length representative of the sward were collected, divided into 7·5 cm lengths, and separated into leaf and stem for the determination of ash, nitrogen, cellulose, and in vitro organic matter digestibility.

Digestibility and leaf: stem ratio of the bulk harvests decreased and dry matter increased as the season advanced. Leaf composition changed little, but stem increased in lignin and decreased in ash and in vitro digestibility. In vitro digestibility and leaf: stem ratio were highly correlated with sheep digestibility.

Chemical composition of shoots of known heights was similar to that of the bulk harvests. Leaf weights/shoot tended to increase linearly with height of shoot, whereas stem increased nearly as the square of the height. Dry matter of leaf and stem were inversely related to leaf:stem ratio. Stem digestibility decreased with leaf:stem ratio and with increase in shoot height.

Chemical components of shoot fractions were associated with each other and were largely dependent on the distance from the top of the shoot at which they had been taken, irrespective of shoot height or time of year. Bottom stems had lower ash, nitrogen and digestibility but higher cellulose, dry weight and dry matter than top stems, whose composition approached that of leaves. Leaf fractions showed little consistent trend with position on the shoot.

Some of the difficulties in studying changes in plant composition under field conditions are discussed.

A field experiment in each year 1963 to 1967 in Suffolk, England, tested the effect on yield of sugar beet of sowing dates ranging from 13 March to 11 May and harvest dates ranging from 20 September to 8 December. Sowings in March or early April gave similar yields of sugar but with later sowings yield decreased progressively faster. The relationship is represented by the equation

y = 106·3 (±2·24) + 0·212 (±0·184)x-0·009 (±0·003)x2,

y = yield as percentage of mean (60·1 cwt/acre of sugar), x = number of days after 12 March.

Delayed harvest increased sugar yield; the relationship is represented by the equation

y = 80·22 (±1·51) + 0·836 (±0·09)z-0·006 (±0·001)z2,

z = number of days after 19 September. This represents an increase of 0·247 cwt/acre/day of sugar in October and 0·083 cwt/acre/day in November, equivalent to about 2½ tons/acre of roots in October and 1 ton/acre in November.

The effect on sugar yield of different lengths of growing period, which ranged from 138 to 271 days, is represented by the equation

y = 38·7 (±26·6) + 1·045 (±0·267)a-0·0017 (±0·0007)a2,

a = number of days between sowing and harvest.

On average, sowing date had negligible effect on sugar percentage at harvest. In 3 years sugar percentage increased after the first harvest to a maximum and then decreased; in 2 years it decreased with consecutive harvests.

The rumen was found to be the main site of metabolism of biuret in sheep adapted to this compound. Some of the biuret which passed into the lower gut could be broken down there but this could account for the breakdown of less than 1 g/day when 15 g was fed. Biuret injected into the jugular vein or entering the bloodstream from the rumen or intestine was excreted unchanged in the urine. Sheep excreted 9–21% of biuret fed in a solid form and 37–39% when it was dosed as an aqueous solution. Sheep not adapted to biuret failed to retain any introduced into the rumen, duodenum or jugular vein.

Pigs were fed either at 3, 6 or 12 hourly intervals to a scale based on live weight from 21 kg to slaughter at 79 kg live weight. There was no effect of treatment on daily gain, feed efficiency or killing out percentage. Backfat thickness at C and K was increased by four times-a-day feeding compared with feeding twice or eight times/day, but this increase in fatness was not confirmed by sample joint dissection.

Six ewes were milked over a lactation period of 12 weeks beginning 2 weeks after parturition. Milk fat, total crude protein, and protein fractions were determined in each weekly milk sample.

Milk fat and total crude protein in whole milk increased significantly over the lactation, attaining mean values of 5.8 and 5.9% respectively. The concentration of the caseins, total albumins and β-lactoglobulin in the whole milk also increased significantly over the lactation, with mean concentrations of 4.67, 0.80 and 0.54% respectively. The mean concentrations of these fractions, expressed as a percentage of the total crude protein, were, caseins 78.7, total albumins 13.5 and β-lactoglobulin 9.1.

The following fractions, whose mean percentage concentrations in whole milk are given in parentheses, showed no significant trends over the lactation: α-lactalbumin + serum albumin (0.26), proteose-peptones (0.05), globulins (0.06) and non-protein nitrogen (0.35). Expressed as percentages of total crude protein, these concentrations are 4.4, 0.8, 1.1 and 5.6 respectively.

The milk constituents synthesized in the mammary gland, i.e. fat, caseins and β-lactoglobulin showed significant correlations in concentration in whole milk as well as significant increases in concentration over the lactation.

Statistical tests were made on the data obtained from 100 non-pregnant lactating cows, whose milk production ranged from 4 to 22 kg/day. The cows were kept in metabolism stalls and fed 37 different rations.

The authors have studied the correlation between total water intake, faecal and urinary water losses, absorbed and available water and the numerous other factors which were analysed in each of the 37 rations.

Total water intake is closely related to the dry-matter intake and the dry-matter content of the diet; it is related also to the composition of the ingested dry matter but is unrelated to the daily milk production.

Faecal water losses are closely related to the dry-matter intake and the dry-matter content of the diet; increase of pentosans and crude-fibre intake enhances the losses.

Urinary water excretion is related to the amount of absorbed water and to the dry-matter content of the diet; a highly significant correlation exists also between urinary water and urinary nitrogen and potassium. Daily milk production and urinary water are negatively correlated.

Water secretion in the milk depends on the dry-matter intake and on its composition; but there is no significant correlation between total water intake and milk water.

Carcass yield and chemical composition of edible meat of fifteen fattened yearling rams and fifteen fattened yearling wethers of Sudan Desert sheep were studied. The animals studied were random samples from groups which had been fattened for 2 months on three different rations. They were about 14 months old at slaughter, and their weights at slaughter ranged from 25 to 52 kg. The average dressing percentage for rams and wethers was 53·0 and 52·2% respectively. Warm carcass weights were 20·22 kg for rams and 19·64 kg for wethers, and these carcasses lost 4·2 and 3·1% of their weight respectively, after 48 h storage in the cold room at 0°C. The bone content of carcasses of rams and wethers was 23·4 and 21·3% respectively. The longissimus dorsi ‘loin eye’ area at the 12th rib was 8·6 cm2 and 8·3 cm2 for rams and wethers. The proportions of wholesale cuts in ram and wether carcasses were comparable, whereas the proportions of slaughter by-products varied between the two ‘sexes’. Mean weight of kidney fat in wethers was 50% greater than in intact rams, but the mesenteric and caul fat was heavier in rams than in wethers.

Ram carcasses had higher specific gravity than those of wether carcasses. Specific gravity was negatively correlated with fat content and positively correlated with protein, moisture and ash content of the edible meat of the carcass. The regression equations relating specific gravity to the major chemical components of meat had too high standard errors to be of predictive value in a practical sense.

An experimental and a conventional grazing system for 7- and 19-month-old dairy replacements were compared during 136 days of the grazing season. In the experimental system A, 24 calves were rotationally grazed around paddocks followed by 24 pregnant heifers which ate the herbage residue left by the calves. The conventional system B consisted of 24 calves and 24 pregnant heifers maintained at the same overall stocking rate as in system A, but the calves and heifers grazed in completely separate rotations. Half the calves on each system were drenched with an anthelmintic at weekly intervals from mid-July onwards to estimate within systems the effect of gastrointestinal worms on live-weight gain.

The total body content of fat, protein, ash, moisture and energy of 43 male cross-bred lambs was determined after the lambs had suckled the ewe at pasture for between 2 and 5 days. Sixteen lambs were dissected into seven compartments, namely, carcass, skin, wool, blood, viscera (two groups) and vastus lateralis muscle, and the chemical composition of each was determined. The heats of combustion of the fat and fat-free tissues were also determined. The relationships between empty body weight and body and organ composition were described by logarithmic regression equations.

Eighteen male cross-bred lambs (aged 2–5 days) in two equal groups were given artificial milk diets of either low- or high-protein content; subgroups of three lambs were slaughtered after 2, 4 and 6 weeks on experiment. The composition of the change in empty body weight (E.B.W.), and the chemical composition of the change in weight of the separate compartments and organs, were determined by the comparative slaughter method.

Lambs given the high-protein diet made significant gains in weight and in all chemical components in all periods. The composition of their E.B.W. was closely related to E.B.W. regardless of age. Lambs given the low-protein diet made only small gains in weight in 6 weeks, of which 76% was fat. The chemical composition of their E.B.W. was closely related to E.B.W. within each age group. The net gain of protein of these lambs in 6 weeks represented only 1% of the total weight gain, and over 50% of the protein gain was in wool. The skin and blood lost protein during the first 2 weeks, and failed to recover this loss during the remaining 4 weeks. Other organs lost protein initially but recovered this loss between 2 and 6 weeks.

It was concluded that the initial loss of protein represented the labile protein reserves of the lamb, and the subsequent recovery was an adaptation to the low-protein diet. Furthermore, the results with both diets indicated that the skin and blood were the most inefficient of the organs in the body in utilizing the available N during a period of protein deficiency, or during a period of abundance in the dietary supply of N.

Nineteen male cross-bred lambs, aged between 2 and 5 days, were allotted to each of three dietary treatments. The protein contents of the diets (on a dry-matter basis) were 12·0% (diet A), 28·5% (diet B) and 45·5% (diet C). The energy intakes of groups of lambs within each dietary treatment varied from below maintenance to ad lib.

The experimental period was of 3 weeks and the composition of the live-weight gain was estimated by the comparative slaughter method.

Body composition within each dietary treatment was highly correlated with empty body weight, but not with the previous energy intake. The fat content of the gain decreased, and the water and protein contents increased, as the dietary-protein concentration increased.

When compared at the same empty body weight, the protein content of the fat-free body of lambs given diet C was significantly higher than that of lambs given diet A. This effect of dietary-protein concentration could not be explained by differences in the amounts of protein stored as wool.

The ensiling characteristics of grasses and of red clover were examined by means of a small scale vacuum silage technique. Eight grasses, comprising three varieties each of perennial ryegrass and cocksfoot and two varieties of timothy, were evaluated after application of two levels of nitrogen fertilizer. Three varieties of red clover were evaluated at two stages of growth with and without sucrose supplementation during ensiling.

Perennial ryegrass varieties contained more water soluble carbohydrates than cocksfoot and timothy varieties. At the low level of fertilizer N, silages made from the first cut in mid-May were all well preserved 3 weeks after ensiling. At the high level of fertilizer only perennial ryegrass varieties and S345 cocksfoot were well preserved. After ensiling for 14 weeks perennial ryegrass silages remained well preserved but secondary fermentation in the cocksfoot and timothy varieties resulted in poor preservation. Silages made from the second cut at the end of May were all badly preserved except for silage made from tetraploid ryegrass at the low nitrogen level.

Significant correlations were established between the water soluble carbohydrate content of the grasses and the quality of the resulting silage, but herbage dry-matter content and buffering capacity were not significantly correlated with silage quality.

The red clover varieties were lower in water soluble carbohydrate and higher in buffering capacity than the grasses. Although the silages from red clover were well preserved they were of high pH. Supplementation with sucrose significantly reduced pH and ammonia content and increased lactic-acid content.

A laboratory investigation was made of the ammonification and nitrification in soil of pure urea with and without pure biuret and pure biuret alone. The soils ranged from acid (pH 5·1) to calcareous (pH 7·9). The work was done at two temperatures 5 and 25°C. The time between adding urea to the soil and the first analysis was from 1 h to 1 week. The soil moisture contents ranged from the wilting percentage to field capacity. In all work involving urea, ammonium sulphate was used as a standard to compare rates of nitrification.

Biuret had no detectable effect on the rates of ammonification and nitrification of urea. Biuret by itself nitrified in all the soils at both temperatures being slowest at 5 °C in the acid soil and fastest in the calcareous at 25°C.

Neither pH nor temperature appreciably affected the ammonification of urea but both had a marked effect on nitrification. The lower the pH and the lower the temperature the slower the nitrification. Ammonium from urea nitrified faster than ammonium sulphate and on the acid soil only ammonium from the urea nitrified.

The moisture content of the soil only affected ammonification of urea slightly but had a marked effect on the nitrification, the drier the soil the slower the nitrification. The same observation applied to ammonium sulphate.

The free-acid content of grass silages was reduced by the addition of sodium bicarbonate to the silage and increased by additions of lactic acid. In each of four comparisons the addition of sodium bicarbonate to increase pH from about 4·0 to about 5·4 resulted in significant increases in intake of dry matter which ranged from 9·7 to 20·7%. Intake of organic matter was consistently increased by this partial neutralization treatment, but the increases were not significant in all experiments. The addition of sodium as sodium chloride rather than sodium bicarbonate did not alter the intake of a highly acid silage. Addition of lactic acid to reduce the pH of a silage feed from 5·4 to 3·8 resulted in a decrease in dry-matter intake of 22%. The correlation between dry-matter intake and the silage characteristics: titratable acidity, total organic-acid content, lactic-acid content and pH were all significant.

It is concluded that the acids produced during the normal silage fermentation can limit the intake of the silage and it is suggested that chemical treatments to preserve wet grass without the presence or formation of large quantities of acids be investigated.

In sheep fed red clover hay nearly 40% of the feed hemicellulose left the rumen undigested and scarcely any of this hemicellulose was digested in the postruminal digestive tract. The caecal microflora from sheep fed the same diet did, however, yield enzyme extracts which readily hydrolysed isolated hemicellulose or xylan preparations. These caecal and rumen microbial extracts, were capable of hydrolysing the hemicellulose in undigested particulate plant material but were not capable of hydrolysing, to any extent, the hemicellulose in undelignified digesta particles from various parts of the postruminal digestive tract. The hemicellulose in delignified postruminal digesta and the hemicellulose polysaccharides isolated from the digesta were hydrolysed by both rumen and caecal hemicellulases. The results are discussed in the light of observations on the postruminal digestion of hemicellulosic material in roughage- and cerealfed animals.

Concentrate diets supplemented with 5, 20 and 40% of a high- and a low-quality hay were given ad libitum to British Friesian steers from 9 weeks of age to slaughter. The intake of dry matter and metabolizable energy was studied over weight ranges from 91 to 363 kg live weight. The quality of hay did not significantly affect the drymatter intake at any of the weight ranges studied. From 91 to 182 kg live weight the daily dry-matter intake decreased as the proportion of hay in the diet increased. Over the weight range from 182 to 272 kg live weight, intake was maximum at the 20% level of hay supplementation, while from 272 to 363 kg live weight, intake increased with increasing levels of hay in the diet. The supplementation of high-quality hay significantly increased the intake of metabolizable energy by animals weighing 91–182 kg. Increasing proportions of hay in the diet significantly affected the metabolizable energy intake at all stages of growth studied.

At 18 and 36 weeks of age digestibility and N balance studies were carried out. The metabolizable energy expressed as a percentage of the gross energy and the mean retention time of the diets were significantly affected by the age of animal, quality of the hay and the level of hay supplementation. Nitrogen retention was also affected by the age of the animal but not by the quality of the hay.

The relationships between the voluntary intake of dry matter and the metabolizable energy of the diet expressed as a percentage of the gross energy, for different stages of growth, are also presented.

The change in the digestibility and the mean time of retention of the diets in the digestive tract with age and the effect of this on the point where physical regulation to intake gives way to physiological regulation are discussed.

Concentrate diets supplemented with 5, 20 and 40% high- and low-quality hay were given ad libitum to British Friesian steers from 9 weeks of age to slaughter.

The performance of the animals was studied over 91 kg weight ranges from 91 to 363 kg live weight and from 9 weeks of age to slaughter. In the whole experimental period the daily live-weight gain was significantly greater on diets containing high-quality hay. There was also an increase in the daily live-weight gain in each of the weight ranges studied on diets supplemented with high-quality hay but this increase was not significant at the stage of growth from 272 to 363 kg live weight. As the level of concentrate in the diet increased there was a significant increase in the daily live-weight gain at each stage of growth studied and over the complete experimental period.

The mean feed conversion ratio was greater for diets containing low-quality hay. Except during the stage of growth from 272 to 363 kg live weight the proportion of hay in the diet significantly affected the mean concentrate conversion ratio. With increasing levels of hay in the diet there was a significant increase in the total dry-matter conversion ratio.

The conversion ratio of metabolizable energy was also increased on diets containing low-quality hay. The proportion of concentrate in the diet significantly affected the conversion ratio of metabolizable energy at all stages of growth studied.

There were significant differences in the killing-out percentages, weight and contents of the reticulo-rumen and the omasum plus abomasum expressed as a percentage of empty body weight, with increasing levels of hay in the diet. These measurements were not significantly affected by the quality of hay in the diet.

Indirect measurements of carcass composition indicated that the level of hay in the diet tended to affect the amount of fat in the carcass but the amount of lean was similar at the different ratios of concentrate to hay. The ratios of the weight of separable lean to the weight of separable bone in the 9–10–11th rib cut were similar at different levels of hay supplementation. The organoleptic appraisal of sample joints indicated that carcass quality was satisfactory.

In a 2-year experiment anhydrous ammonia (82% N) and an ammonium nitrate fertilizer (34·5% N) were applied at three annual rates—100, 200 and 300 lb N/acre (112, 224 and 336 kg/ha)—on an S.24 perennial ryegrass sward. At each rate the two fertilizers were applied either as a single dressing in the spring or as five equal split dressings over the season. Total yields of herbage dry matter and of crude protein were determined by cutting the herbage at approximately the same stage of growth five times each year. On the basis of total yield and seasonal distribution of yield anhydrous ammonia was best applied as a single dressing in the spring, whereas ammonium nitrate was best applied as five equal split dressings over the season. However, in both years anhydrous ammonia applied as a single dressing gave smaller yields and a poorer seasonal distribution of production than did ammonium nitrate applied as five equal split dressings. The factors contributing to the lower yield level with anhydrous ammonia applications are discussed. It is concluded that anhydrous ammonia has no marked advantages over ammonium nitrate as a nitrogen fertilizer for intensively managed grassland.