Animal Production

Bradford and Spurlock, 1964, vol. 6, part 3, p. 299, line 7.

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.

1. Herbage was harvested from a single pasture in early June and late August of the same year and was preserved by freeze-drying. The June herbage contained more water-soluble carbohydrate than that cut in August but in other respects, including chemical and botanical composition and the apparent digestibility of organic matter and nitrogen, differences between the herbages were small.

2. The June herbage was given to a mature ewe during eight periods each of about 4 weeks' duration, and the August herbage was given during nine periods. The level of feeding varied between periods from about 0·35 to 1·5 times the maintenance level; in addition the fasting metabolism of the sheep was determined on three occasions. Gross energy intakes and the losses of energy in faeces, urine, methane and as heat were measured in each period.

3. The metabolisable energy of the June herbage was utilised more efficiently than that of the August herbage for fattening, and probably for maintenance also. It is suggested that this result stemmed from the difference in soluble carbohydrate content which was lower in the August material. The cellulose of that herbage was digested to a significantly greater extent, a larger proportion of the gross energy was lost as methane, and the ruminai volatile fatty acids, included a significantly lower proportion of propionic acid.

1. Twelve sets of 3 litter-sister Large White gilts were mated at first oestrus after reaching 250 lb. live-weight and given daily during 3 successive pregnancies either 6 lb. (A), 3 lb. (B) or 3 lb. for 76 days then 6 lb. until parturition (C) of the same meal mixture. During an 8-week lactation all were given 4 lb. meal plus 0·8 lb. per piglet suckled.

2. There was a significant linear increase in numbers born with successive parities (P<0·05) but no significant differences between treatment or sister groups. There was a highly significant difference between treatment groups in mean piglet birth weight (P< 0·001) but no parity effect; mean birth weights were 2·76, 2·40 and 2·58 Ib. for Groups A, B and C respectively. Differences between sister groups in mean piglet birth weight were also significant (P<0·05).

3. Post-natal litter performance was poor for all groups, probably because of the presence of E. coli, but there was no evidence of treatment effects other than on 3-week weight of third litters, which was significantly greater in Group C than in A or B (P<0·05). There were no significant effects on either number or weight of piglets at 8 weeks.

1. Nitrogen balance studies were conducted on 16 steers in two separate trials. The steers were fed on four diets containing respectively dry rolled barley; dried, steamed and rolled barley; dried, crimped barley and barley that had been stored in a sealed silo and rolled.

2. There were no significant differences in the dry-matter intake of any of the diets.

3. No consistent differences between the diets in dry-matter digestibility or nitrogen retention were observed.

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.

The possibility that restriction of pasture and controlled supplementation of the diet of milking cows with concentrates might improve the efficiency of utilisation of grazing was examined in a double reversal grazing experiment with 9 Ayrshire cows per treatment which extended over 4 months.

Cows received either pasture alone allocated daily by electric fence (treatment B), or half the pasture area plus one-third of their expected DOM intake offered as concentrates (treatment A).

In the first two periods, treatment A resulted in closer defoliation of the pasture.

Over the whole experiment there was no significant difference in yield of fat-corrected milk between treatments, although treatment A depressed butterfat percentage and raised milk yield significantly. Treatments did not influence live-weight gain significantly and toth groups gained over the season.

Feed intake estimated by chromic oxide-faecal index methods was similar for both treatments except in period 1. Intake estimates by clipping methods or by faecal index methods were in close agreement in period 1 for treatment B and in reasonable agreement in periods 2 and 3.

The results are discussed particularly with a view to the possibilities of replacing some grazing with barley or other concentrated feeds. On the available evidence this is economically feasible only where very profitable uses of the grassland saved are possible.

1. Two-thousand and sixty serum samples from indigenous cattle in Central Africa were examined for serum transferrin type. The breeds studied were Manguni, Mashona, Tuli, Angoni and Afrikander.

2. The variation in gene frequencies from breed to breed is presented. With the exception of one Angoni herd, the remaining herds fall into distinct breed groups.

3. The Mendelian hypothesis was tested on eight herds including at least one herd of each breed. With two exceptions good agreement with this hypothesis was obtained. The two exceptions were traced to two bulls, a Mashona (TfB/TfD) and a Tuli (TfD/TfF), both of which contributed TfD to their progeny at a rate in excess of Mendelian expectation.

4. The Hardy-Weinberg equilibrium hypothesis was tested for thirteen herds and good agreement was obtained in all cases.

5. In Angoni cattle no evidence was found to reject the hypothesis of independent segregation at the haemoglobin and transferrin loci.

1. An experiment was carried out with 24 individually fed castrated male, Large White pigs, to examine the effects upon growth and body composition of an anabolic steroid included in finishing diets of two protein levels.

2. There was a significant interaction between steroid and dietary protein level on the growth rate and food conversion efficiency. On the low protein diet growth rate and efficiency were improved by steroid treatment while with high protein intake the steroid significantly depressed growth. Analysis of the main effects showed no significant differences between steroid and protein means for food conversion efficiency and no significant difference between protein means for growth. There was a significant difference (P<0·05) for rate of growth in favour of the animals not receiving the steroid.

3. Steroid significantly improved the percentage of lean and the eye muscle area, but decreased the length of pigs. High protein feeding also improved the percentage of lean and the eye muscle area and also increased the length.

4. The results are discussed in relation to the use of steroids in other species, optimum time of application and the problem of ascertaining accurate physiological doses.

The voluntary intake and apparent digestibility of three roughages, alone and in mixtures, by six steers and six sheep were studied in 56 individual experiments. The fasting metabolism of each animal was also determined so that maintenance energy needs could be assessed.

No significant differences between the voluntary intakes of roughages by cattle and sheep were found when, for all experiments with each species, voluntary intake (g./kg.W0·73)was regressed on apparent digestibility. Cattle, however, digested the same roughage better than did sheep and consumed more of it. Despite their higher maintenance needs/kg. W0·73, when given the same roughage cattle thus attained the same relative feeding level (energy apparently digested/energy required for maintenance) as did sheep, there being an indication that sheep were more efficient users of low quality roughages than cattle. Sheep with high maintenance requirements tended to eat more than those with low ones, but no such relationship could be established with cattle.

When fixed amounts of higher quality roughage were given to both steers and sheep which were also given a lower quality roughage ad libitum, the total intake of food was in proportion to the voluntary intakes attained when the roughages were given separately.

Carcass data from 123 pigs slaughtered at either 120 lb., 200 lb. or 260 lb. live-weight have been analysed to study the relative value of four sample joints in predicting tissue composition in the carcass.

Percentage fat, muscle or bone in all joints was highly correlated (P<0·01) with the corresponding percentage of that tissue in the carcass. The highest correlations and correspondingly lowest residual standard errors were found for the loin, rib and composite loin and ham joints.

Significance tests of the a and b constants in regression equations relating percentage fat, bone and muscle in the joint to that in the carcass showed that only with the rib joint was it legitimate to combine the data from each slaughter weight into ‘overall’ equations.

As pooling the data for the combined loin and ham joint had little effect on the magnitude of the residual standard errors, overall equations relating tissue composition of that joint to the whole are also given. The accuracy of prediction, however, was lower than that obtained with the rib joint.

Application of the pooled regression equations relating carcass and rib joint composition to independent data, obtained by identical techniques, gave promising results.

1. A mathematical theory of the culling process in dairy cattle has been developed. This was necessary to give a conceptual framework for the discussion of longevity in the dairy herd as a heritable character, of its genetic relationship with milk yield and of the effects of selection on the genetical analysis of yield itself.

2. Culling is assumed to take place at the end of each lactation by truncation selection of a normally distributed variate (the culling variate) of which yield itself is a component.

3. Expressions are then derived for the effect of the culling on various parameters of yield and for survival as a function of yield.

4. The derivation of expressions relevant to progeny groups is dependent on the relative values of the genetic and phenotypic regressions of the culling variate on yield.

5. Because little is known of the actual causes of culling, it is not permissible to predict the genetic gain in yield by multiplying the selection differential by the heritability. This is only justified if the genetic and phenotypic regressions of the culling variate on yield are equal.

6. A direct estimate of the genetic gain by selection can, however, be obtained from the covariance for any character between the mean relative survival of progeny groups and their mean value for the character.

7. The effect of culling on the genetic analysis of yield in later lactations is discussed, as is the effect of later culling on survival to later ages as a function of early yield. It is suggested that the regression coefficient of relative survival of progeny groups on heifer yield will be approximately linear with age whereas that of individuals will probably increase to a limiting value.

8. The heritability of survival to different ages will probably pass through a maximum at the fourth lactation.

9. Longevity itself, as a function of heifer yield, is the sum of the cumulative survival curves to each individual lactation. The regression of length of life on heifer yield, at the individual or at the progeny test level, can be related to the mean phenotypic and genetic selection applied to animals in the herd at any time.

10. Because culling is to a large extent a voluntary action of the farmer, longevity in the dairy herd, though it is under continual selection and may have a significant heritability, need not necessarily increase.

The genetic progress in live-weight-for-age (LFA), milk production, and in overall economic value expected as a result of performance and progeny testing of young bulls with respect to milk production and LFA was computed. It was shown that performance testing can contribute considerably to overall progress in economic value, while under certain circumstances progeny testing for LFA can also contribute to genetic progress in overall economic value, but to a lesser degree than performance testing. The relative economic value of LFA and milk production was derived and found to be relatively stable under differing economic conditions.

Relationships between the intake of energy and the rate of gain on the one hand, and the chemical composition of gain on the other were studied in bacon pigs, assuming that: (1) the only important determinants of the energy balance are the expenditures of energy in maintenance, in protein deposition and in fat deposition; (2) the net energy cost of fat or of protein deposition remains constant in pigs of all ages and live-weights, whatever the level of nutrition; (3) the average maintenance requirements of pigs growing over the same live-weight range and kept under similar conditions are constant, irrespective of their daily gains; (4) the ratio of non-fat components to protein in the gains of pigs over a similar live-weight range is virtually constant. Deductions based on these assumptions enabled the expression of the feed conversion ratio as a function of the average daily protein deposition, the average daily maintenance requirements and the average daily intake of energy to be made. The dependence of the feed conversion ratio on each of these three factors was demonstrated.

After the substitution of plausible values for the energy costs of protein and of fat deposition, as well as for the average maintenance requirements, equations were derived for the estimation of the content of protein and of fat in the live-weight gain, when the total feed consumption and the number of days on test (20 to 90 kg.) were known. Using these equations, the average gain of fat and of protein in each year were estimated for the Danish Progeny Testing Stations during the period from 1926–7 to 1962–3. It was found that the decrease of the feed conversion ratio and consequent reduction in fat deposition which were achieved during this period, were accounted for mainly by an increase in daily protein deposition.

This paper reports a paternal half sib analysis of data collected over 3 years to estimate additive genetic variance of growth between birth and 16 weeks in crossbred progeny derived from Down rams. The data were divided into two groups and pooled estimates of parameters obtained by two methods. The paternal half sib intra-class correlations varied between 0·017 and 0·057 depending on pooling group and method. It is suggested that such low correlations arise because (a) most of the lambs in the study were still sucking at slaughter, close to 16 weeks of age, and the trait measured is thus largely influenced by maternal milking ability (b) the selection practised in the Down breeds may have been effective and reduced genetic variation and (c) there is considerable inbreeding in the Down breeds.

In further analysis of data from four farms involving rams mated to more than one breed of ewe there was limited evidence of specific combining ability of growth between birth and 16 weeks of age for Welsh ewes compared to ewes of other breeds.

Results are presented of an investigation in which 10 bull calves were subjected to heat stress in a climatic chamber from 26 weeks of age to the age of puberty. A similar group of 8 calves sired by the same bull were simultaneously subjected to ambient temperatures in another chamber. Maximum temperature in the hot chamber was 35–36° C. for 8 hours daily and maximum temperature in the temperate chamber was 27° C.

Observations were made on weight and age at puberty and characteristics of the first five ejaculates obtained from each bull. Post-mortem examinations included: carcass weight, weight of all genital organs, measurement of sperm reserves in testicles and epididymides and histological observations of the seminiferous tubules. The results indicated that the hot temperature exposure retarded fertility but that libido was exhibited at essentially the same intensity by both groups. The quality of semen obtained and the concentration of the spermatozoa were much lower in the bulls subjected to the hot environment during their growth period prior to puberty. The poor quality of semen was associated with impaired spermatogenesis.

It is recommended that in all fertility studies conducted with exotic breeds in the tropics, semen of known uniform quality be used. Natural service should not be used.

Conditions exist in Ghana which could implicate vitamin A deficiency as a factor in causing the poor growth and breeding difficulties observed in local cattle. Lansbury (1960) reviewed some of the limiting factors in the nutrition of cattle on the Accra plains, and stated ‘the bleached dried up appearance of the Accra plains over much of the year is due to the fact that most of the grassland is little more than standing hay from which most, if not all, of the vitamin A or its precursors are likely to have been lost’. Northern Ghana, with its longer dry season, presents such an appearance for a more extended period.

The physiology of indigenous West African cattle has not been investigated thoroughly. The ability of native cattle to survive on dietary regimes drastically deficient by standards based on requirements of temperate zone cattle, indicates an adaptability suggestive of a physiology differing from that of temperate zone cattle. The study reported herein was conducted to provide information on one aspect of this problem; namely the haemoglobin levels of indigenous cattle, as influenced by breed, season of year, growth characteristics and nutrient intake.

Investigations of measurable properties of pig muscle have been carried out in many countries (Scheper, 1962). This note describes the effect of sex on six characteristics of longissimus dorsi muscles, i.e. content of moisture, fat, total nitrogen, expressible moisture, myoglobin, total pigment and colour (light reflectance).

The maintenance requirement for digestible organic matter of adult sheep has been derived by Wood and Capstick (1926) and more recently by Lang-lands, Corbett, McDonald and Pullar (1963) by means of regression analysis of data for feed intake, live-weight and live-weight gain.

As data from digestibility trials carried out both in Trinidad and Venezuela were available, similar equations were derived for adult male sheep under tropical conditions. Groups of six adult male sheep were housed individually and total collections of faeces and urine were made for periods of 10 days after preliminary periods of 7 or 10 days. The quantity of forage offered was generally that which the individual sheep would eat without leaving a large residue. The results obtained in these trials and a more detailed description of the methods used have been described elsewhere (Butterworth, 1963; 1965). In all, 178 sets of data were used. Each set for an individual animal consisted of daily intake of digestible organic matter (D), the mean (W) of initial and final body weights, and daily change in weight (G) all in lb. Values of D and G were means obtained from the results for the 10-dayperiod. The value of G was subject to high error in determination as periods were short and measurement of weight change in ruminant animals over short periods is most unreliable (see for example, Lush, Christensen, Wilson and Black, 1928; Whiteman, Chambers, Loggins, Pope and Stephens, 1954). Mean values and ranges of the values were as follows: D=0·96 lb. (0·46–1·87 lb.), W=84·2 lb. (56·0–149·0 lb.) and G=0·02 lb. (-0·5-+0·5 lb.). The digestibility coefficients for the dry matter of the various forages used ranged from 47·3 to 68·0%.