bluuebunny/crossref_metadata_2025 huggingface dataset:
Muscle: bone ratio and fat percentage as measures of beef carcass composition
Authors: Berg R. T. , Butterfield R. M.
Published: September 2010

1. Total anatomical dissection data from 62 half carcasses of steers representing 6 breed groups differing in age and nutritional history, were examined with a view to establishing a basis for comparison of carcass composition of breed groups or of cattle from various treatments.

2. The results indicate that total muscular tissue might be used for comparative purposes in certain instances. Muscle weight differences could be examined independently of general size by adjusting to common muscle plus bone weights.

3. It is proposed that relative carcass composition is best assessed by use of two measures: muscle: bone ratio and percentage fat tissue in the carcass.

4. Muscle: bone ratio was shown to increase with carcass weight and after the effects of carcass weight had been statistically removed the influence of percentage fat on this ratio was negligible. The required adjustment to muscle: bone ratio for differences in carcass weight was estimated at 0·03 per 10 kg. increase in carcass weight.

5. Percentage fat in a carcass is proposed as an index of acceptability. The requirements of different markets in terms of this index would need to be established. Adjustment factors for percentage fat based on carcass weight would need to be established on a within group basis.

6. Relative growth coefficients for muscle, bone and fat, based on a logarithmic relationship with total muscle plus bone, are presented and were found to agree closely with those for swine and sheep. The magnitude of differential growth in body tissues indicated by the growth coefficients accentuates the necessity of making carcass composition comparisons at standard weights or following suitable statistical adjustments.

7. The implications of carcass composition assessment in beef breeding programmes are discussed.
Nutrition of the early-weaned calf. IX. Nitrogen retention from different protein sources in calves fed ad libitum
Authors: Kay M. , Preston T. R. , MacLeod N. A. , Philip Euphemia B.
Published: September 2010

1. Nitrogen balance studies were conducted on 8 early-weaned calves fed on four diets containing respectively Peruvian fish meal, soya bean meal, groundnut meal and dried distillers grains as the major sources of protein.

2. Nitrogen retention differed significantly between diets, being highest on the fish meal diet, and lowest on the groundnut diet.
Hexoestrol implantation of steers fattened at pasture I. Effects on growth and herbage intake
Authors: Alder F. E. , Tayler J. C. , Rudman J. E.
Published: September 2010

The possibility of using hormones to increase the productivity of meat animals has been considered for a number of years (Hammond, 1957 and Scarisbrick, 1960). Lamming (1957) has pointed out that most of the work with hormones and beef cattle has been done in the U.S.A. under feedlot conditions. In this country Aitken and Crichton (1956), Dodsworth (1957) and Lamming (1957 and 1958) all obtained increases in rates of gain with implantation. Lamming found that responses in steers varied from 0 to 15% increase in gain per day in spring, about 20% in summer, 40% in autumn, i n each case on pasture and up to 60% under winter feeding conditions. He also used several levels of implantation, from which it appeared that the optimum level was about 45 mg. hexoestrol. Smith (1958) described trials conducted at eight farms in the North of Scotland in which 189 steers fattened solely on grass were implanted with hexoestrol. Implantation resulted in an extra daily live-weight gain of about 0·5 lb. Increases in dose levels above 60 mg. produced no significant response in terms of live-weight gain. Eighteen experiments at Experimental Husbandry Farms and the Norfolk Agricultural Station, described by Jones (1961), also showed that live-weight gain was increased by implanting; that the correct dose to give maximum response appeared to be 45 to 60 mg. hexoestrol; and that the implant should be made from 100 to 130 days before slaughter. Second implantations were made in several of these experiments and it appeared doubtful if this practice was desirable. In New Zealand, Lucas (1958) and Everitt (1959) also found that hexoestrol implantation increased weight gains of grazing steers.
Volatile fatty acids in the rumen of African sheep given a variety of low-protein diets
Authors: Topps J. H. , Elliott R. C.
Published: September 2010

1. Total concentrations of volatile fatty acids and molar proportions of acetic, nrooionic and butyric acids were determined in the rumen of Blackhead Persian sheep given sixteen low-protein diets.

2. Total concentrations of acids ranged from 2·89 to 9·33 millimoles/ 100 ml. of rumen liquor. Both digestibility and protein content of the ration had a significant effect on the concentration of volatile fatty acids in the rumen liquor. Protein content of the diet probably influenced the latter through controlling the rate of ruminal fermentation.

3. Molar proportions of acetic acid varied from 59·7% to 69·3%, of propionic acid from 21·2% to 29·6%, and of butyric plus higher acids from 7·6% to 16·3%. Protein content of the diet had no significant effect on the composition of the acid mixture, but organic matter digestibility was inversely related to the proportion of acetic acid.

4. The fermentation in the rumen of Blackhead Persian sheep, as judged by the volatile fatty acids produced, appears to be similar to that found in European breeds of sheep.
Determination of the milk yield of sows and correction for loss of weight due to metabolic processes of piglets during suckling
Authors: Spaendonck R. L. Van , Vanschoubroek F. X.
Published: September 2010

In determining the milk yield of the sow by weighing the litter before and after suckling, loss of weight due to metabolic processes must be considered.

An experiment is described to investigate the loss of weight of piglets caused by metabolic processes between two consecutive weighings, and to investigate the relationship between this loss on the one hand and the body weight and the age of the piglets on the other. Weight changes of 15 litters of average 9·8 piglets were studied during 66 weighing periods of 16 minutes, by putting the pigs in a cage, fixed on a differential balance. Each weighing period consisted of 8 periods of 2 minutes, so that in all, loss of weight was studied during 528 2-minute periods.
A note on milk production in crosses between dutch and American strains of Friesian dairy cattle
Authors: Soller M. , Bar-Anan R.
Published: September 2010

In poultry and dairy cattle heterosis is occasionally found in crosses of different strains of the same breed (Hutt and Cole, 1952; Johansson, 1939; Nordskog and Ghostley, 1954). Limited data on the milk production of reciprocal crosses between Dutch and American strains of Friesian dairy cattle being available in Israel, an investigation was carried out to determine whether crossing these two strains resulted in a heterotic effect on milk production.
Specialised sire and dam lines. IV. Selection within lines
Authors: Moav Rom , Hill W. G.
Published: September 2010

Selection on an index of two traits was represented graphically by means of a response ellipse or response circle. This procedure was used to find optimal index weights for uncorrelated traits, and to compare the efficiency of alternative indices.

Profit was expressed as a reciprocal function of reproductive performance, from which it was shown that the higher the reproductive performance, the smaller the weight that should be applied to it in a selection index. It was found that in pigs and broilers the average commercial standard of reproductive performance is sufficiently high that selection on production traits alone is almost as efficient as selecting on the optimum index.

Three alternative procedures for selecting from a single original line were compared graphically: A. Maintaining the single line and selecting all animals on the same index. B. Maintaining the single line but selecting males and females on separate indices. C. Splitting the original line into separate sire and dam lines, each selected on a specialised index. Method C was found to be the most efficient of the three; B was more efficient than A for one generation, but less efficient in subsequent generations.
Factors governing the shape of the growth curve of body weight and the age at slaughter of Suffolk × Welsh lambs
Authors: Broadbent J. S. , Watson J. H.
Published: September 2010

Curves of growth in live-weight, from birth to 16 weeks of age, of 362 Suffolk × Welsh lambs were analysed for the effect of sex, birth type, sire and test centre environment and related to variation in age at slaughter.

The relative pre-natal disadvantages of twin lambs resulted in their curves of growth differing from those of single-born animals, particularly in males. Test centre environment exerted a marked effect in such cases. At one centre, male twins showed marked compensatory growth.

Differences in growth existed between the 14 sire progeny groups. As the linear component of the growth curves decreased, the quadratic values became increasingly negative. Deceleration of growth was most marked in slowest growing progeny groups and this was accentuated by a poor test centre environment.

These factors combined to influence age at slaughter, which was also related to birth weight of the lamb. Lambs at the best test centre reached slaughter weight 10 and 16 days earlier than lambs at the two remaining centres. Sires produced differences in age at slaughter of 10 to 14 days, within centres.
Selection practices in dairy herds. 1. First lactation performance and survival to the second lactation
Authors: Hinks C. J. M.
Published: September 2010

1. The relationship between first lactation performance and the ability of individual animals to survive to the second lactation has been examined in Friesian and Ayrshire populations in an attempt to isolate the main determinants of survival, and to rationalise an apparently complicated selection procedure.

2. Low milk yield was the most important single cause of culling in the first lactation, though the two breeds differed considerably in the relative importance of milk yield in the selection programme. Natural wastage, caused by factors beyond the control of the farmer, accounted for the disposal of 5·7% of the population during the first lactation. Selection for butterfat was marginal in both populations, and could only be detected at extreme butterfat percentages, where high butterfat tended to compensate for a poor milk yield, and low butterfat to confirm a decision to cull an average yielding animal. Survival was not significantly affected either by the size of the herd or by the age at calving.

3. The proportion culled, and the intensity and effectiveness of selection for milk yield, were inversely related to the level of herd performance, and were greater in summer calving animals than in winter calvers.

4. The analysis indicated that selection for milk yield in different environments could be adequately described in terms of the Normal Curve. Yield-survival curves were computed and compared for groups of animals in different herd and calving season environments. When milk yield was expressed in terms of the deviation from the herd-year average, it was found that summer calvers, and animals in low yielding herds, had to demonstrate a productive capacity of far greater individual merit, if their chances of survival were to match those of their winter calving herdmates, and those of their contemporaries in higher yielding herds. When milk yield was expressed in absolute terms the survival of individual animals of similar yield was comparable in all herd and season environments. It was concluded that all the herds included in the analysis had been subject to the same absolute standards of milk yield in the selection of first calvers.
The protein requirement of the ruminant calf. I. The effect of protein content of the concentrate mixture on the performance of calves weaned at an early age
Authors: Stobo I. J. F. , Roy J. H. B. , Gaston Helen J.
Published: September 2010

1. Three experiments are reported, in which a total of seventy-two calves were weaned at 3 or 5 weeks of age and given concentrate mixtures containing either 19·2% or 11·9% crude protein, together with hay and water up to 12 weeks of age.

2. The performance of cross-bred calves weaned at 3 weeks of age and given concentrates ad libitum was significantly greater when the high-protein concentrate was used in Experiment 1.

3. In Experiment 2, in which Friesian heifer calves were weaned at 5 weeks and given concentrates ad libitum, the level of protein in the concentrates had no significant effect on live-weight gain from birth to 12 weeks. However, there was a tendency for the performance of calves given the concentrate containing 11·9% crude protein to be slightly inferior up to the age of 8 weeks.

4. When concentrate intake was restricted to 2 kg./day in Experiment 3, in which Friesian heifer calves were weaned at 5 weeks of age, the live-weight gain was significantly greater when the higher level of protein was given.

5. Daily increases in height at withers, heart girth and belly girth tended to be greater in all instances when the concentrate containing 19·2% crude protein was given, but significant differences between treatments occurred only in Experiment 3 for increase in heart girth and belly girth.

6. It is apparent from the results that the calf weaned at an early age needs to be given a concentrate containing more than 11·9% crude protein if maximum live-weight gain is to be achieved up to 8 weeks of age. The optimum protein content of the concentrate after this age seems to depend on the level of concentrate feeding. The relationship between energy and protein in determining production is discussed.
A note on the improvement of a trait by selecting on its components
Authors: Smith Charles
Published: September 2010

Many traits in farm animals, such as litter size or fleece weight, are the product or ratio of two or more component items. This note seeks to determine the circumstances in which selection directed at the component items is more effective in improvement than selection for the composite trait itself.

A change of one per cent in a product trait can be achieved by a change of one per cent in any of its components. The response expected on selection for a product trait or a component is proportional to h2C per cent, where h2 is the heritability and C is the coefficient of variation. Thus selection for a component trait (A) may possibly be more efficient than direct selection for the product trait (X) when is greater than . However, the correlated changes in other component traits would also have to be taken into account.
A note on the substitution of sorghum for barley in diets for fattening pigs
Authors: Lodge G. A.
Published: September 2010

Changes in prices of the basic cereals make it necessary to have a reliable assessment of their relative nutritive values if maximum economic efficiency of pig production is to be attained. As the primary role of cereals in pig feeds is as a source of energy, it is on this basis that comparison should be made but with due allowance for any major differences in nutrient content which may necessitate differential supplementation.

Sorghum, or milo, is a cereal imported into the United Kingdom which, at times, may be competitive with other cereals for price per ton but about whose nutritive value there is some confusion. Sorghum has not often been compared with barley as a cereal for pigs, but its value relative to that of maize seems to vary widely, between 80 and 100% (Braude, Mitchell and Robinson, 1950; Hillier, MacVicar and Pond, 1954; Aubel, 1956; Loeffel, 1957; Peo and Hudman, 1958; Schruben, 1959; Vanschoubroek, Spaendonk and Nauwynck, 1964). Estimates of relative digestible energy values (DE) are equally variable; the DE value of sorghum has been assessed as 94·5% (Diggs, Becker, Terrill and Jensen, 1959) and 96·2% (Robinson and Lewis, 1962) that of maize, whereas the TDN value given by Evans (1960) is greater than that of maize. Robinson and Lewis (1962) consider the DE value of sorghum to be 140% ofthat of barley, but Evans (1960) quotes a TDN value for sorghum which is 111% of that of barley. While variation in the type of sorghum used may account for some of this discrepancy, Dammers and Djikstra (1961) found little difference between the varieties milocorn, kaffir corn, granifero and white dari, and only guinea corn differed in having a lower energy value.
Variation in growth and efficiency in twin cattle on constant feeding levels
Authors: Taylor C. S. , Young G. B.
Published: September 2010

A genetico-nutritional experiment is described in which 22 Ayrshire twin cattle, both one-egg and two-egg, were reared and maintained for up to seven years on a standard all-pelleted ration. Six equally spaced constant levels of food intake ranging from 35 1b. to 140 1b. per week were used. Each twin was reared on nearly ad libitum feeding until it had grown sufficiently to be able to consume its pre-assigned level of constant food intake. Thereafter its weekly food intake remained unchanged until the end of the experiment. The number of animals on each of the six feeding levels varied from two to six.

On each constant level of food intake, animals continued to grow fairly rapidly for two or three years, but thereafter their growth tended to slow down and usually an equilibrium weight was eventually attained. The resultant mean weight curves constituted an apparently simple, regular and systematic family with each curve eventually separated from the next by a relatively constant weight difference.

Coefficients of variation were about 3% for unrelated animals strictly conforming to the design, but increased at later ages to around 6% when animals with different pre-treatment were included. Coefficients of variation, however, did not change over the ascending series of feeding levels.

The advantages of the design for exploring the triple relationship of gain, weight and food intake are outlined. The potential use of such results as an empirical feeding scale and the possibility of obtaining paths of maximum efficiency from such a controlled experiment are described.
A note on relationships between components of weather and the location of defaecation in out-wintered cattle
Authors: Powell T. L.
Published: September 2010

A Number of controlled environment studies (reviewed by Blaxter, 1962 and 1964) have emphasised the necessity of providing shelter for out-wintered ruminants. The nature of suitable shelter requires definition and this may be sought by observing the use animals make of different forms of shelter. Direct observation of livestock may, however, sometimes be an inappropriate investigational method. In the work reported here, shelter usage by cattle was assessed from the occurrence of defaecations in various regions of a pasture. Evidence of increased sheltering activity under weather conditions encouraging greater body heat loss would suggest that this method of recording behaviour may be recommended for application in relevant situations.
The evaluation of a device for feeding group-housed animals individually
Authors: Broadbent P. J. , McIntosh J. A. R. , Spence A.
Published: September 2010

A system which allows group-housed animals to feed individually is described. In this systm animals have sole access to their individual feeding point and this access is unlimited in duration and frequency. The food intake and performance of growing Friesian castrated male calves housed and fed by two arrangemente of this feeding device have been compared with cattle that were group-housed and group-fed, and cattle individually penned. A4 × 4 latin square design was used.

No significant treatment differences were detected and the feeding device did not appear to affect the food intake, performance or behaviour of the cattle.
Intensive beef production: 10. Replacement of cereals with chopped straw
Authors: Kay M. , Macdearmid A. , MacLeod N. A.
Published: September 2010

1. Two growth trials and a digestibility trial were carried out with 48 Friesian steers given diets containing approximately 5, 20, 35 and 50% chopped barley straw and concentrates up to 100%.

2. Rates of live-weight gain between 130 and 400 kg declined from 1·18 to 0·65 kg/day and carcass gain declined from 0·62 to 0·30 kg/day as the straw content of the diet increased from 5 to 50%.

3. Alimentary tract ‘fill’ increased from 10·5% of live weight with 5% straw to 21% of live weight with 50% straw, and killing-out percentage dropped from 55·5% to 48·3%.

4. Both dry-matter digestibility and apparent nitrogen digestibility were lowest for the diet with 50% straw.
Effects of early pregnancy on postnatal maternal performance of mice
Authors: Eisen E. J. , Williams W. R. , Hayes J. F.
Published: September 2010

The influences of age at first pregnancy and number of suckling young on maternal performance of mice were studied. Mean mating ages for early-pregnant and normal-pregnant females were 27 and 52 days respectively. Litter size from parturition (day 0) to day 12 of lactation was standardized to either 8 or 12 pups. The more rapid (P<0·01) growth rate and feed conversion efficiency of early-pregnant dams from mating to parturition continued from 0 to 12 days of lactation but occurred primarily in the first 3 days of lactation, so that there were no differences in body weight or feed intake from days 3 to 12 of lactation. There were no age at pregnancy effects on total mammary gland DNA, RNA or RNA/DNA ratio at day 12 of lactation or on individual progeny weights or feed conversion efficiency of litter growth from 3 to 12 days of lactation. Dams suckling eight young had a lower (P<0·01) feed intake, gain and feed conversion efficiency from 0 to 3 days of lactation. From 0 to 12 days of lactation, these dams were smaller, consumed less feed and their individual progeny weights were larger (P<0·01). Dams suckling eight pups had smaller (P<O01) mammary glands, less (P< 0·05) mammary gland DNA and a higher (P<0·05) RNA/DNA ratio. Interactions between pregnancy age and number suckling were not significant. Feed intake of the dam from 0 to 12 days of lactation was influenced more by litter weight gain (34%) than either dam weight gain (5%) or metabolic body size (6%). Maternal performance of mice, based on pup growth and mammary gland growth and function, was not affected by early pregnancy.
Productivity of Africander, Tswana, Tuli and crossbred beef cattle in Botswana
Authors: Trail J. C. M. , Buck N. G. , Light D. , Rennie T. W. , Rutherford A. , Miller M. , Pratchett D. , Capper B. S.
Published: September 2010

The three indigenous beef cattle breeds in Botswana, the Tswana, Africander and Tuli, were evaluated for reproductive performance, viability and growth. Over 3 yr the calving percentages of 1389 Africander cows, 305 Tswanas and 357 Tulis were 64·5, 70·6 and 85 respectively. These differences were significant (P<0·05). Mortality of the Africander calves was higher to 2 yr of age, being 11% compared with 7-5% for Tswana calves and 7·4% for Tulis. The 18 mo weight of 219 Tuli cattle was 284 kg, and of 454 Tswanas 279 kg, both superior to the 270 kg for the 786 Africanders. Productivity estimates combining these three traits demonstrate the value of the Tuli breed for Botswana conditions.

Comparisons of the crossbreds produced by the use of Simmental, Brahman, Bonsmara and Tuli sires on Tswana cows showed an advantage in growth to 18 mo through crossbreeding. The 18 mo weights of Simmental and Brahman crosses at 324 and 304 kg respectively were significantly different, and superior to the weight of pure Tswana at 279 kg. Bonsmara and Tuli crosses at 294 and 290 kg also showed a significant increase over the pure Tswana. The use of the Simmental is now recommended for better management conditions, with Brahman crossbreeding on a wider scale.
A note on selection differential and generation length when generations overlap
Authors: James J. W.
Published: September 2010

The generation interval may be defined as the mean age of parents of all progeny born, or as the mean age of parents of only those progeny destined to be selected as replacements. If the mean age of parents of replacements is used, selection differentials must be calculated within parental age groups. If the mean age of parents of all progeny born is used, the selection differential contains a component due to disproportionate selection of replacements from different parental age groups.
The value of virginiamycin (Eskalin) as a feed additive for growing pigs in diets with or without a high copper supplement
Authors: Barber R. S. , Braude R. , Mitchell K. G. , Pitman R. J.
Published: September 2010

In three trials, each involving 48 individually-fed pigs grown from 20 to 90 kg live weight, the value of virginiamycin as a performance-promoter either alone or together with 250 mg Cu/kg diet was examined. Both copper and virginiamycin on their own gave significant, although small, improvements in performance and the results suggested that there can be a degree of additive action between the two materials when both are added to the diet.
Pattern of intake of three roughage diets by non-pregnant, non-lactating Scottish Blackface ewes over a long period and the effects of previous nutritional history on current intake
Authors: Foot Janet Z. , Russel A. J. F.
Published: September 2010

The voluntary intake of two hays and one dried grass by 48 mature non-pregnant Blackface ewes was measured for 33 weeks. The apparent dry-matter digestibility coefficients of the diets in vitro were 59, 61 and 77% respectively for the hays and the dried grass. At the end of the first phase of the experiment each group of 16 ewes was split into two subgroups of five animals, each of which was subsequently given one of the other diets, and one subgroup of six animals which remained on the same diet. Food intake was measured for a further 8 weeks. Body fat was estimated at intervals from tritiated water space.

The amount of variation in voluntary food intake that could be attributed to variation in live weight and fatness of the animals and in apparent dry-matter digestibility and cell wall constituents of the diet was calculated for various periods.

The range of live weight and fatness increased during the experiment. Initially, and after the change in diets, variation in apparent dry-matter digestibility had an important positive effect on intake, but at the end of the 33-week phase its influence was negligible or, when fat weight was not considered, negative. The negative effect of fat weight on intake increased during the experiment.

Within individual diets during short periods of time (1 to 5 weeks) the highest proportions of the variation in intake that could be attributed to variation in live weight and fatness of the ewes were 50, 94 and 65% respectively for the hays and the dried grass. Taking all three diets together all the variables considered could explain 75% of the variation for a few weeks at a time, but for longer periods seasonal influences, and other factors not included among the independent variables, probably operated.
A note on the effect of breed-type and sex on the distribution of intermuscular fat in carcasses of sheep
Authors: Gaili E. S. E.
Published: September 2010

The distribution of intermuscular fat (IF) was studied in 24 lambs, of balanced sexes, from each of the Dorset Horn, Hampshire and Clun breeds, which were slaughtered at 42 kg live weight. The Clun lambs yielded the least total IF, the Dorset Horn most and the Hampshire an intermediate amount. The Clun lambs had significantly (P<005) less IF in the thoracic limb than the other two breeds; and the IF content of the neck+thorax region in the Hampshire was lower than that in the remaining breeds. Females had more IF than males in all sites examined. At an equally adjusted total IF weight, sex differences disappeared. The Hampshire yielded more IF in the thoracic limb, pelvic limb and back+abdomen, but, exceptionally, less IF in the neck + thorax than in the other two breeds.
A note on some factors influencing muscle pH values in commercial pig carcasses
Authors: Smith W. C. , Wilson A.
Published: September 2010

Measurements of longissimus dorsi pH at 45 min post mortem (pH1) were taken in 27 727 pig carcasses at four bacon factories. The overall least squares mean pH1 was 6·26 and 15·5% of carcasses had pHi values of 5·9 or less. Sex and commercial grade of carcass had little influence on muscle pHi or the incidence of values below pH 6·0. Factory differences were recorded in the distribution of muscle and within each there were marked producer effects in mean and the incidence of values below pH 6·0. Carcasses of Large Whites had fewer muscle pH1 values below 6·0 (12·4%) than those of British Landrace (18·7%), this being mainly due to a large breed effect at one factory. Although breed and testing background of sires of the carcasses examined and the first order interactions with factory had significant effects on muscle pHi and the incidence of values below pH 6·0, they were of little practical significance.
Comparing estimates of herbage digestibility from faecal nitrogen and in vitro determinations
Authors: Birrell H. A.
Published: September 2010

In a grazing experiment, the organic matter digestibility of herbage selected by sheep grazing at two stocking rates was determined at monthly intervals over a 9-month period by (i) the in vitro determination of organic matter digestibility of the material collected from sheep fitted with an oesophageal fistula, and (ii) derivation from the prediction of digestible organic matter intake with a faecal nitrogen regression. A comparison of the two techniques confirms the view of other workers that faecal nitrogen indices based on pen feeding trials of green herbage are unreliable for predicting digestibility of green herbage in the field. The bias which is produced by faecal nitrogen regression appears to be associated with the time spent grazing by the animal each day. Relating organic matter digestibility directly to nitrogen content of faeces of grazing sheep (N, g nitrogen/100 g faecal organic matter) and their grazing time (T,h) yielded the following equation:

The expression has standard errors (±2·6) similar to those involved in an in vitro determination. It provides a simple technique for estimating digestibility of herbage eaten by grazing sheep, but this may only be applicable to the particular sward conditions.

Field estimates of digestibility over summer and autumn by this equation were found to be similar to estimates by a faecal nitrogen expression established from hand feeding sheep with dry summer herbage.
Prolongation of gestation and changes in maternal steroid hormone concentrations during cold exposure of sheep in late pregnancy
Authors: Samson Deborah E. , Slee J. , Thompson G. E. , Goode Jane A. , Flint A. P. F.
Published: September 2010

In 40 ewes exposed to thermoneutral or cold environments during the last 5 to 6 weeks of pregnancy (experiment 1), and in 10 ewes treated in the same way during the last 3 to 9 days of pregnancy (experiment 2), cold exposure lengthened mean gestation times by 1·7 and 2 days respectively. This effect was statistically significant only in experiment 1. Blood samples were taken from the right atrium of ewes in experiment 2 and the concentrations of some hormones in the plasma were measured. Cortisol concentrations were higher in plasma from cold-exposed ewes than control ewes. Plasma progesterone concentrations were lower in cold-exposed ewes than control ewes during a period from 36 h before parturition to 36 h after parturition, but the changes in plasma total unconjugated oestrogens, 17a, 20o-dihydroxypregn-4-en-3-one and oestrogen sulphates were associated with parturition in the normal way.

The mechanism underlying the prolongation of gestation during cold exposure requires further investigation; events that precede the change of steroid production by the placenta at parturition are most likely to be involved.
Evaluating feeding strategies for dairy cows: a modelling approach
Authors: Doyle C. J.
Published: September 2010

Using a model to simulate food intake and the partition of food between milk production and live-weight gain, an attempt has been made to explore the financial implications of different levels and patterns of concentrate feeding, where silage is fed ad libitum. In the case of high-yielding cows it appeared that, although feeding more concentrates increased overall lactation yield, profits per cow and per hectare declined with increasing concentrate usage. This raises doubts concerning the traditional view that higher profits result from increasing yields per cow. Comparing different patterns of feeding it also appeared that there was no significant economic loss from flat-rate compared to stepped feeding of concentrates, where cows had ad libitum access to silage.
A comparison of long and shredded cereal straw for beef cattle
Authors: Mira J. J. F. , Kay M. , Hunter E. A.
Published: September 2010

Thirty Hereford × Friesian steers initially weighing 320 kg were used in two experiments, to compare the effects of mechanical processing of barley straw and the amount of rolled barley offered on intake and live-weight gain. The straw was offered ad libitum either in the long form or shredded through a 40 mm screen and supplemented with 20, 35 and 50 g barley DM per kgW"75 per day (L, M and H respectively). A solution providing 12 g urea per kg straw dry matter (DM) was sprayed onto the straw and all the animals were offered daily 480 g of soya bean meal with minerals and vitamins. In the first experiment, which had a change-over design, the animals were weighed at the beginning and the end of each period. The daily consumption of shredded straw (kg DM) was L 3·38, M 3·29 and H 3·00 and of long straw L 3·94, M 4·02 and H 3·56 (s.e. of difference, 0·29). There were significant differences in straw intake between steers offered the long and the shredded straw (P < 0·001) but no differences in intake when different amounts of barley were offered within the same physical form of straw. The mean daily live-weight gains for treatments L, M and H respectively were 0·25, 0·66 and 0·80 kg for steers given shredded straw and 0·32, 0·62 and 0·87 kg (s.e. of difference, 0·1) for those offered long straw. At the end of the first experiment the same animals were kept for a further 10 weeks on the same straw treatment but only treatments L and H were continued, the steers from treatment M being distributed between L and H. The straw intakes and live-weight gains were in agreement with those observed in the first experiment
Performance of Friesian cows with high and low breeding indexes 2. Energy and nitrogen balance experiments with lactating and pregnant, non-lactating cows
Authors: Grainger C. , Holmes C. W. , Moore Y. F.
Published: September 2010

Six lactating Friesian cows (three high and three low breeding index cows) were subjected to a total of 28 complete energy and nitrogen balances during early and late lactation. In addition, 12 non-lactating Friesian cows (six high and six low breeding index cows) were offered individually pasture indoors for 62 days, beginning at approx. 180 days of pregnancy. Cows within each genotype were randomly allocated to feeding levels which were nominally equivalent to their requirements for maintenance or twice maintenance. Eight of the 12 cows (four high and four low breeding index) were each subjected to two energy balance periods at approx. 210 (period 1) and 230 (period 2) days of pregnancy.

When offered pasture ad libitum during lactation, cows with high breeding indexes consumed significantly more gross energy per unit of metabolic live weight (P < 0·05) than did cows with low breeding indexes, but the two genotypes did not differ in their ability to metabolize the gross energy of the food, or in the individual losses of energy in faeces, urine or methane.

There were no significant differences between genotypes in their heat production at a common energy intake except during restricted feeding in early lactation when high breeding index cows produced less heat than did low breeding index cows (P < 0·05). During lactation high breeding index cows retained a higher proportion of their total energy retention (milk + body tissue energy) as milk in late lactation (P < 0·01) but not in early lactation.

For non-lactating cows, both genotypes required similar amounts of metabolizable energy to maintain zero maternal body energy retention, 0·79 and 0·80 MJ/M0·75 for periods 1 and 2 respectively. The efficiency with which metabolizable energy was converted to net energy (kg) was similar for both genotypes at both stages of pregnancy, the mean value being 0·52. The metabolizable energy required to maintain body condition was estimated to be 0·78 and 0·71 MJ/M0·75 for high and low breeding index cows respectively. The metabolizable energy required in excess of maintenance to promote a gain of one unit of body condition was estimated to be 2290 MJ. This is equivalent to 27 MJ energy retained per kg live-weight gain.

For lactating and non-lactating cows the differences between genotypes in their utilization of nitrogen were small and inconsistent.
Efficiency of food utilization in traditional and sex-controlled systems of beef production
Authors: Taylor C. S. , Moore A. J. , Thiessen R. B. , Bailey C. M.
Published: September 2010

An empirically based equation for voluntary food intake, obtained from a multibreed cattle experiment, was used to develop formulae for evaluating the overall efficiency of food utilization of beef production n i a production unit consisting of a dam and her progeny. With these formulae the dependence of overall efficiency on degree of maturity at slaughter was studied, with reproductive rate, dam food costs, terminal sire size and number of calvings per dam allowed to vary.

The formulae were used to study efficiency of food utilization in a traditional beef production system. Maximum efficiency values ranged from 2·3 to 3·5 g of lean tissue per MJ of metabolizable energy. These maximum values were affected to a small extent when progeny were slaughtered much earlier or later than the optimal degree of maturity. In a single-sex, bred-heifer (SSBH) system, the maximum value that could be attained with high technological efficiency and a reproductive rate of unity was 5·2 g, which was 0·5 times more efficient than the highest achievable traditional value. With a reproductive rate of 0·85, the highest efficiency value in an SSBH system was 4·8 g.

Overall efficiency of food utilization was also examined in a sex-controlled system where all offspring for slaughter were male and in a modified traditional system where every surplus female was bred once. Both these systems could give higher efficiency (up to 1·08 times) than in a traditional system, but neither could compete with a well-operated SSBH system.

Formulae to deal with multiple births, partial sex control and other factors are given in the APPENDIX.
Genetic selection to produce lines of sheep differing in plasma copper concentrations
Authors: Wiener G. , Woolliams J. A. , Woolliams Carol , Field A. C.
Published: September 2010

Male lambs were selected annually at 18 and 24 weeks of age for high or low concentrations of copper in plasma to produce two closed lines. The difference between the high and low lines increased to approx. 0·5 mg/1 after 5 years when the experiment ended, indicating appreciable additive genetic variation for the concentration of Cu in plasma. The selection lines were derived from a population of Scottish Blackface × Welsh Mountain crosses which had been interbred for many generations. The two parental breeds contributing to the cross normally differ in a number of aspects of Cu status with that of the Welsh higher than that of the Blackface. Both pure breeds were kept as controls. In the final year, Cu concentrations of the high selection line exceeded the values of the Welsh and the low selection line had values below those of the Blackface. Differences between the selection lines persisted at all ages.

There were indications of changes in the frequency of the Hb alleles, associated with the selection for Cu concentrations, but there were no correlated changes in body weight, reproductive performance or lamb mortality during the 5-year selection period when dietary supplies of Cu were not particularly restrictive.
Effects of source and level of protein on milk yield and reproductive performance of high-producing primiparous and multiparous dairy cows
Authors: Bruckental I. , Drori D. , Kaim M. , Lehrer Hanna , Folman Y.
Published: September 2010

Ninety primiparous and 150 multiparous Israeli-Holstein dairy cows were allotted at random into three groups. One group (LSBM) was given 170 g crude protein (CP) per kg dry matter (DM). The two other groups were given 210 g CP per kg DM with the extra 40 g CP per kg DM supplied either by soya-bean meal (HSBM) or by fish meal (HFM). Roughage supplied proportionately 0·20 of the dietary DM and was maize silage with groundnut hay in the winter and wheat silage with oat grass in the summer. The primiparous and multiparous cows were offered the experimental diets for 16 and 24 weeks, respectively.

Milk, milk fat and milk protein production (kg/day), for treatments LSBM, HSBM and HFM, were: 39·3, 40·0, 40·8 (P > 0·05); 1·12, 118, 1·06 (P < 0·05) and 1·21, 1·23, 1·26 (P > 0·05) for multiparous cows and 29·4, 31·2, 33·4 (P < 0·05); 0·89, 1·07, 0·93 (P < 0·01) and 0·92, 0·98, 1·05 (P < 0·05) for primiparous cows, respectively. Cows of high yield potential responded more to increasing dietary protein level than did cows of low yield potential. Average live-weight gains on treatments LSBM, HSBM and HFM were (g/day): 220, 160 and 310 (P < 0·05) in multiparous cows and 220, 170 and 230 (P < 0·05) i n primiparous cows, respectively. Pregnancy rates, 16 weeks after parturition, were 0·65, 0·52 and 0·72 (P < 0·05), in the LSBM, HSBM and HFM groups, respectively. The decrease in pregnancy rate in the HSBM cows, occurred in primiparous cows and cows in their fourth or later lactation but not in cows in their second or third lactation. The milk production of primiparous and multiparous cows in relation to the level and source of dietary CP and the utilization of energy and protein for milk production is discussed.
Performance and body composition of young steers given stack-ammoniated hay with or without a supplement or untreated hay with a supplement
Authors: Gibb M. J. , Baker R. D.
Published: September 2010

An experiment was carried out to investigate the performance of young steers given either ammoniated hay alone (TA), or supplemented daily with either 112 g fish meal (TF) or 2 kg barley (TB) or 2 kg barley-based concentrate (TC), compared with untreated hay supplemented with either urea (UU), to raise the nitrogen content of the diet to that of the ammoniated hay, or with 2 kg concentrate (UC). Serial slaughter of animals was carried out to examine the effects on body composition during the winter feeding period and subsequent grazing season.

Ammoniation of the hay significantly increased the in vivo digestibility of organic matter, acid-detergent fibre, neutral-detergent fibre and cellulose fractions (0·672 v. 0·643, 0·740 v. 0·670, 0·758 v. 0·638 and 0·826 v. 0·741, respectively). When offered with 2 kg concentrate, intake of ammoniated hay was higher than that of the untreated hay. Empty body weight gains (EBWG) during the winter period were affected by treatment (174, 225, 293, 590, 631 and 692 g/day for treatments UU, TA, TF, UC, TB and TC, respectively), and were highly correlated with total gross energy intakes (56·0, 61·0, 62·9, 74·5, 73·2 and 83·1 MJ/day, respectively). As the rate of EBWG increased, the fat proportion (g/kg EBW) at turn-out also increased. During the grazing season animals which had been on treatments UU, TA and TF showed a marked degree of compensatory growth (759, 686 and 640 g/day EBWG, respectively) compared with treatments UC, TB and TC (623, 572 and 601 g/day EBWG, respectively), and differential rates of tissue gain. This resulted in reduced, though still significant, differences in EBW, although body composition (g/kg EBW) at final slaughter was similar for all treatments. Thus, whilst short-term advantages in intake and performance can be obtained by ammoniation of hay, the benefits so achieved may not persist due to subsequent compensatory growth at pasture.
An assessment of carcass probes for use in Great Britain for the EC pig Carcass Grading Scheme
Authors: Cook G. L. , Chadwick J. P. , Kempster A. J.
Published: September 2010

To gain approval for use in the revised European Community (EC) Pig Grading Scheme to be introduced in 1989, methods of estimating carcass lean proportion must be shown to do so with a coefficient of determination greater than 0·64 and a residual s.d. of less than 25 g/kg. A trial was carried out to assess a number of methods for use in the EC Scheme as applied in Great Britain. Subcutaneous fat and m. longissimus depths at the head of the last rib and at the third/fourth from last rib were measured using the optical probe (OP), the Fat-O-Meater (FOM), the Hennessy Grading Probe II (HGP) and the Destron PG-100 Probe (DST) on a broad sample of 162 commercial carcasses representative of the ranges in fatness and weight found nationally. The left side of each carcass was separated into component tissues. Although the instruments all achieved similar levels of accuracy in predicting carcass lean proportion, some differences were found. The DST just failed to reach the required statistical criteria for approval in the EC Scheme. The results for the other three instruments were submitted to Brussels as evidence of suitability and they have been approved.

Using the regression relationships found between carcass composition and fat thickness together with results from earlier studies, it was estimated that the carcass separable fat proportion of British slaughter pigs has fallen at the annual rate of 7 g/kg since 1975.
The effect of interaction of ewe and lamb genotype on milk production of ewes and on growth of lambs to weaning
Authors: Doney J. M. , Peart J. N. , Smith W. F.
Published: September 2010

Single and twin purebred Scottish Blackface lambs born to Blackface ewes, and Suffolk cross lambs born to East Friesland × Blackface ewes, were removed from their dams at birth and cross-fostered to give all combinations of breed of ewe, breed of lamb and number of lambs suckled, with no ewe rearing her own lamb.

Milk production was measured on 1 day/week for 14 weeks. The effect of ewe breed was significant in all weeks, with the East Friesland cross ewes having a higher peak and a more sustained level of production than the Blackface ewes. Ewes suckling twins produced more milk than those suckling singles. Breed-of-lamb effect was significant during the first 5 to 6 weeks of lactation, with crossbred lambs inducing a higher milk output than Blackface lambs, irrespective of the breed of ewe suckled. Beyond this stage, lactation potential of the ewe replaced demand by the lamb as the first limiting factor.

Food intake by ewes during the first 6 weeks differed slightly with both ewe and lamb breed but there were larger differences associated with number of lambs suckled.

The data suggest that lambs on higher milk intake consume a smaller proportion of solid feed but that, in all groups, live weight at 14 weeks of age was closely related to milk intake.