Results of four experiments involving a total of 124 pigs covering the growth period between about 40 and 210 lb. live-weight indicated that:

1. The growth rate and efficiency of food utilisation of pigs receiving liquid skim milk up to a maximum of 5¼ pints per head per day, was better than that of pigs receiving a balanced all-meal diet. This was equally so whether the liquid skim milk was fed throughout the growing period or was abruptly removed from the diet at either about 75 lb. or 120 lb. live-weight, provided the all-meal diet fed subsequently contained adequate protein.

2. The addition of 0·1% copper sulphate to the meal fed with liquid skim milk significantly improved the growth rate and efficiency of food conversion.

3. The addition of 0·2% dl-lysine and 0·1% dl-methionine to the meal fed with liquid skim milk had no effect on the performance of the pigs.

4. Withdrawal of a protein supplement from the rations of pigs after they reached about 120 lb. live-weight adversely affected their performance.

1. Four groups of four calves were given rations containing adequate and inadequate amounts of magnesium, both with or without an excess of potassium, added as potassium chloride.

2. The excess of potassium resulted in the death of three of the eight calves, the clinical signs observed before death being cardiac insufficiency, oedema, severe muscular weakness and muscular atony. The excitability of motor nerves, measured by the method of Kugelberg (1944), was reduced by excess dietary potassium and the serum concentration of potassium was increased. The potassium content of the erythrocytes declined with age, irrespective of dietary treatment.

3. Although this evidence of potassium intoxication was obtained, no concomitant abnormalities were induced in magnesium metabolism by the excess of potassium whether or not the calves received rations containing adequate or inadequate amounts of magnesium.

4. Excess potassium had no effect on the concentration of potassium or magnesium in the muscle or on the Ca : Mg ratio in bone.

5. Magnesium deficiency resulting in tetany was shown to have no statistically significant effect on the intracellular concentration of magnesium i n the muscle. A very small drop in erythrocyte magnesium was noted. No effect on the excitability of motor nerves was observed.

6. The results suggest that the effect of excessive manuring of pastures with potassic fertiliser in increasing the incidence of hypomagnesaemic tetany is not due to a direct effect of potassium on the magnesium metabolism of the animal.

An experiment was started in 1950 designed to find out what proportion of the difference in milk yield between herds is genetic in origin. Sixty-five pairs of twins were split at birth equally between farms having high-yielding herds and farms having low-yielding herds. A previous paper on this experiment reported on the growth of the twins, the present paper on milk yield and on management practices in the herds.

Twenty-four pairs of twins survived to complete one lactation and these provide an estimate of 24%±18% for the genetic part of the difference between the herds.

Aspects of rearing of the twins and of management of the herds were examined. Twins in the high-yielding herds were served and calved earlier than those in the low-yielding group but they had a longer interval between service and calving. Differences between average heifer yields and average cow yields were from one-and-a-half to two times greater in the high- than in the low-yielding herd group. There were no obvious quantitative differences in feeding practice between the two groups although differences in body size suggest that twins in the high group were done better. For the age at first service there was a positive rank correlation of 0·30 between body size differences and subsequent differences in first lactation milk yield. There was no single factor of management or environment which appeared to be the cause of the yield difference between the herds.

1. Two experiments were made. In Experiment 1, 124 ram, wether and ewe lambs were allocated to four equal groups as they reached a live-weight of 30 lb. Group A received no hexoestrol; group B were implanted with a 15 mg. pellet of hexoestrol and lambs of group C were given a second pellet of 15 mg. 35 days after the first. Group D were implanted with three 5 mg. pellets simultaneously in three different sites. The lambs were creep-fed while running with their dams on pasture and were killed as they reached a live-weight of 95 lb.

In Experiment 2, 20 weaned ram lambs were allocated to a hexoestrol-implant group or a control group as they reached a live-weight of 40 lb. They were fed a pelleted ration indoors and were slaughtered at a live-weight of 110 1b.

2. Length of teats and weight of the pituitary were significantly increased for all lambs treated with hexoestrol as compared with their controls. Excessive mammary development and one case of rectal prolapse were observed i n treated ewe lambs, while 3 of the treated rams in Experiment 2 had scrotal oedema.

3. The rate of live-weight gain was greater for all hexoestrol-implanted lambs in Experiment 1 but less for the implanted lambs on Experiment 2 as compared with their respective controls. The differences just failed to attain significance at the 5% level.

4. Dressing percentage was significantly reduced by hexoestrol treatment i n Experiment 1. On the other hand treated ram lambs in Experiment 2 had significantly higher dressing percentages and appeared to be fatter than the controls.

5. Weights of testes and seminal vesicles in the ram and of the ovary in the ewe were decreased by hexoestrol treatment. Weights of seminal vesicles in the wether and of oviducts and uterus in the ewe were increased.

1. Eight Ayrshire milk cows were grazed for four 3-week periods from July to October 1957 in a balanced sequence on two strip-grazed and two free-grazed paddocks, each of two acres. Feed intake and digestibility were estimated by the chromic-oxide faecal-nitrogen method.

2. There was no significant difference in average feed digestibility between the treatments. Free grazing cows ate 30·4 lb. dry matter per day and strip grazing cows 28·9 lb. The difference was just significant (p<0·05). There was no significant difference in milk yield, live-weight or live-weight gain per cow.

3. Total feed output per acre was 11% greater on strip grazing when measured by utilised starch equivalent but only 1 % greater when measured by estimated feed consumption. The data suggest that strip-grazed cattle needed less energy for grazing.

4. The results are discussed with reference to their accuracy, their implications on grazing management and their correspondence with estimates of food requirements based on indoor feeding standards.

In an initial experiment, cattle receiving 5 mg. hydroxyzine dihydro-chloride daily gained 12·7% faster and manifested 12·0% better feed conversion ratio than the control, but these effects were not statistically significant under the conditions of the experiment. Carcass quality and endocrines were not affected by hydroxyzine feeding.

1. 2-week-old calves previously fed whole milk were changed abruptly o t skim milk which had been treated with formalin to give a final concentration of 0·1% of the preservative.

2. Difficulty was experienced in accustoming the calves to drink such formalin-treated milk and scouring invariably occurred within two days of the changeover.

3. Post-mortem and histological examination of calves fed formalin-treated skim milk showed severe damage to the alimentary tract compatible with clinical symptoms.

4. None of the above findings was apparent in control calves fed untreated skim milk.

1. Records used to compile the Contemporary Comparisons of 57 Friesian, 8 English Ayrshire and 11 Scottish Ayrshire A.I. bulls, each with at least 100 ‘effective daughters’ were analysed.

2. For each bull, the herd-years were divided into three equal groups on the basis of the average heifer yield of both daughters and contemporaries (high-, medium-, and low-producing herd-years) and three independent Contemporary Comparisons were calculated for each bull, one at each of the three yield levels.

3. In the data from England and Wales, the mean Contemporary Comparison declined with increasing mean level of production. This decline was such as to imply that some 20% of the differences in production between herds were genetic in origin. A possible explanation lies in the gradual change from Dairy Shorthorn to Friesian and Ayrshire which has taken place in England and Wales, but not in Scotland, during the last 15 years.

4. The variance within progeny groups within herd-years increased from the low level to the high but the coefficient of variation decreased slightly. The variance between sires also increased with the mean level of production but almost exactly in parallel with that within sires so that the heritability and consequently the accuracy of the progeny test for milk yield was effectively the same at all production levels.

5. The correlation between the true breeding values of the bulls at the different levels was very close to one.

6. From these results it is concluded that there is no need to provide special strains within breeds to suit particular management levels or to concentrate progeny testing in the higher-producing herds and that daughter records from all herds, irrespective of level of production, can be used with equal confidence.

1. A survey of management practices associated with the self-feeding of silage was carried out on a group of 130 farms during the winter of 1958-9.

2. The majority of farmers housed their cows in covered yards and allowed them free access to silage stored in a roofed surface clamp.

3. An average of 56 square feet per cow of covered yard and, under free access, 9·7 inches of face width per cow were allowed.

4. The average estimated consumption of silage over the whole feeding period was 2·12 cubic feet per cow per day. Where the feeding face was lit at night, the estimated silage consumption was 0·27±0·10 cubic feet per cow per day more than on other farms. There was also a suggestion that on farms where hay and/or straw was fed, the consumption of silage was less than on the remainder.

5. Levels of milk production were similar and concentrate feeding were slightly lower than those found in National Milk Recorded and Private Milk Recorded herds.

Comparisons have been made of a calf early-weaning concentrate mixture in which 50% of the total nitrogen was derived from groundnut meal and a similar mixture having 33% of the nitrogen from groundnut and 19% from white-fish meal.

In a feeding trial with 9 pairs of Aberdeen-Angus crossbred calves which were weaned at 3 weeks and then fed ad libitum, those given the ‘groundnut plus fish meal’ ration ate 4% less concentrate and gained 6 lb. more in weight over an 81-day period than their pair mates fed the ‘groundnut’ ration. Neither effect was significant.

There were no differences between the two rations in their digestibility or their ability to promote nitrogen retention when food intake was equalised.

1. The four systems of rearing dairy heifer calves, described in Part 1 of this series are now studied for their effect on absolute and relative growth rates to maturity.

2. Data on live-weights and measurements and the percentages of mature size attained by these at 44, 80, 104, 132, 182, 260 and 312 weeks of age are tabulated.

3. In all groups the measurement to reach maturity earliest was circumference of metacarpus followed in order by length of back, height at withers and width of hooks.

4. By 6 years of age all groups had attained approximately the same body size. Maturity in the LL group in terms of four skeletal measurements was delayed by only 9 months, and in the case of HL and LH animals by 5 and 4 months respectively.

5. All groups showed the same general pattern of relative growth but the effect of restricted feeding was to increase at the younger ages the difference i n percentage of mature size between early and late maturing measurements. After 44 weeks of age the rate of growth was most rapid in those measurements which were furthest from maturity then.

6. The rate of tissue deposition was markedly increased in high plane animals during early pregnancy compared with low plane. Evidence is presented to show that much of this was lost during lactation.

7. At first oestrus, animals in all four treatment groups had reached the same percentage of mature size for each body dimension (except for length of back in the LL group).

8. From data on 5 animals it is shown that although growth in height at withers and length of back ceased by 6 years of age there was slow but continuous growth in live-weight, middle and heart girths and width of hooks to 9 years of age.

1. The fat-corrected milk yields and butterfat and solids-not-fat percentages of the milk of heifers reared on the four planes of nutrition described in part 1 of this series are compared, i.e. high high (HH), high low (HL), low low (LL), low high (LH).

2. The most significant feature of the F.C.M. yields was the poor performance of the HL group in each lactation. When variability due to differences in lactation length had been eliminated the yields of the HL group in the first and second lactations were found to be significantly lower than those of the other treatment groups.

3. In the first lactation the mean B.F. percentages of HH, LH, HL and IX animals were respectively 3·92, 3·85, 3·81 and 3·74. These differences were significant at the 5% level. When the weekly yields and percentages of the HH and LL groups were compared it was found that the difference was almost entirely confined to the first 6 weeks of lactation. In the second and third lactations the mean B.F. percentages of all groups were similar.

4. Only in the second lactation were the S.N.F. percentages significantly different between groups. No explanation can be offered.

5. A comparison of the live-weight changes of HH and LL animals following successive calvings showed that recovery by the LL animals was most rapid immediately following first parturition and also during the first and second dry periods.

6. The plane of nutrition during rearing had no apparent effect on the pattern of change in milk yield and composition between first and third lactations, except that HH animals showed a more uniform rate of fall in S.N.F.% between one lactation and the next compared with the other three groups. Heifer lactations were longer and the milk had higher contents of B.F. and S.N.F. than later lactations.

7. The estimated feed costs of the rearing from birth to first calving of the HH, LH, HL and LL animals were markedly different.

8. The results are discussed in relation to practice.

Vertebrae counts made on 504 Large White and 550 (Wessex × Large White) pigs showed an association with carcass length but not with other carcass traits. For each additional vertebra there was an increase in length of approximately 15 mm.

Another group of 313 piglets from 36 litters were X-rayed at around 9 days of age in order to predict their ultimate carcass length. After correction for sex and variations in weight at slaughter it was found that the number of thoracic and lumbar vertebrae together accounted for 14% of the remaining variation in carcass length. Improved accuracy of prediction, accounting for 29% of the variation was obtained with a multiple regression equation using as independent variables: the skeletal length of the young pig as measured on its radiograph, its weight at birth and X-raying and the number of lumbar vertebrae. From measurements made on the carcass it i s suggested that X-raying of the bacon pig to measure the length of the first four lumbar vertebrae, would, in conjunction with an earlier determination of vertebrae number, enable a much improved prediction of carcass length to be made.

The incidence of various vertebral variations is noted and in particular the occurrence of one pig with only six cervical vertebrae.

Harnesses for the total collection of faeces from both ewe and wether sheep are described and field experience with them is reported.

1. Attributes desired in the gammons of bacon pigs are discussed, together with the methods whereby they are measured.

2. An experiment is described in which 16 judges made visual assessments of the qualities of the gammons of 10 carcasses of bacon weight from photographs, both of the fresh carcasses and of the cured bacon sides.

3. The judges did not show a high level of agreement in their rankings of the gammons. Although the overall rankings by the panel of the gammons on the fresh carcasses and on the bacon sides were similar, neither ranking was related to the composition or yield of the gammons.

4. The judges showed better agreement in their rankings of photographs of the cut surfaces of these 10 gammons and the cross-sections of the cooked gammons produced from them; in this case their preferences were related to the lean content of the gammons.

5. A second trial in which 25 judges scored 12 actual bacon sides for the quality of their gammons showed an even lower level of agreement between the judges' rankings, and again there was little agreement between the overall rankings of the panel and the results of dissections.

1. A comparison has been made of 305-day lactation milk yields and butterfat percentages of twin and single-born cattle under experimental and field conditions. Experimental two-egg twins, as judged from within-pair variances, were four times as variable as one-egg twins. Two-egg twins in the experimental herd were more alike than twins in dairy herds in fat percentage due to more frequent butterfat testing. Variance of milk yield within pairs was the same in both experimental and farm twins.

2. Twins and half sisters in dairy herds had similar within-pair variances for milk yield and fat percentage. Full sisters, of necessity non-contemporary, differed more in yield than twins and half sisters; significantly so in the latter comparison.

3. The between-pair variance components for experimental twins were high, relative to twins in herds. In experimental twins, breed differences, lack of culling and uniform treatment were probably contributing causes, and also more frequent observation of fat percentage during lactation. Twins n i dairy herds had greater between-pair variances than full sisters.

4. Experimental MZ twins had an intra-class correlation for milk yield of 0·88 and DZ twins of 0·67 which was much higher than for twins on farms. Farm twins and half sisters had correlations for milk yield of 0·37 and 0·31, to be compared with 0·20 in full sisters. Corresponding values for fat percentage were 0·40, 0·35 and 0·25 on farms as against 0·88 and 0·65 for MZ and DZ twins at the experiment station. These differences between experimental and commercial pairs were largely attributable to differences in between-pair variance.

5. There is no evidence from experimental or commercial data that twins produce less milk than single-born cows.

6. Differences between farms increased the within-pair variance in yield and decreased the intra-class correlation of twins and half sisters but had less effect on full sisters.

An analysis was made of the effect of inbreeding in Sardinian sheep from the records of 658 single female lambs born in the Monastir flock in the years 1935–42 and 1947–55.

The calculations of differences between inbreds (both 12·5% and 25%) were done within recording years. The results showed that inbreeding had no significant effect on birth weight or 30-day weight.

1. A field investigation to estimate the mean weight and chest girth of unserved Friesian, Ayrshire and Dairy Shorthorn heifers of between 3 and 24 months of age was carried out.

2. Data from 1,620 Friesians, 725 Ayrshires and 455 Dairy Shorthorns in the North of England were obtained, with a mobile weighbridge and a. spring-loaded steel tape in the winter 1958–59.

3. It was found that on average the Friesians were heavier and had a greater chest girth than the Ayrshires and Dairy Shorthorns, which did not differ significantly.

4. These heifers were apparently reared on planes of nutrition which, judged by conventional feeding standards, may be described as ‘low’.

5. After eliminating the linear effect of age by covariance analysis, highly significant differences between herds and between sires in weight and chest girth were found.

6. The investigation demonstrated the feasibility and value of collecting field data on body size.

The effects on average daily gain of a 12 mg. implant of diethylstilboestrol has been tested in male suckling lambs and in male hoggets. In both types stilboestrol produced some mammary stimulation. One case of rectal prolapse was encountered in the hoggets. In suckling lambs, treatment did not significantly increase rate of gain nor significantly affect any of several carcass characteristics studied. In hoggets, treatment produced a highly significant increase in rate of gain (33%), a highly significant increase in pelt weight and a highly significant decrease in the percentage of fat in the last rib section. It produced a non-significant increase in muscle and bone in the last rib section. Carcass score and dressing percentage were not significantly affected by treatment.

The oral administration of L-thyroxine to suckling female lambs from 30–70 lb. live-weight did not significantly affect the rate of gain or the carcass characteristics studied.

In three trials involving 288 hoggets the influence on growth rate of implanting 15 mg. hexoestrol or 12 mg. stilboestrol was compared. In one trial the influence of adding excipient to either stilboestrol or hexoestrol to increase the surface area of the implant was also assessed. Live-weight gain was calculated for each time interval after implantation and it was concluded that after approximately 140 days the influence of implantation had largely disappeared. For optimum benefit to live-weight gain implantations should be made approximately 100 days prior to slaughter.

In all trials, implantation with synthetic oestrogens resulted in extra daily live-weight gain, the increase for all animals amounting to 31% extra daily gain for hexoestrol and 26% for stilboestrol. The addition of excipient to the implant diminished the initial growth response and reduced the extra gain achieved.

Implantation with the synthetic oestrogens significantly increased the final live-weight on the farm, live-weight before slaughter and carcass weights when groups of animals from each treatment were slaughtered together.

Stilboestrol and hexoestrol implantation resulted in an extra 4·7 and 6·1 lb. full live-weight; 3·7 and 5·3 lb. empty live-weight and 1·3 and 2·8 lb. extra carcass weight respectively, compared to controls killed at the same time.

Where hoggets had received a high-plane diet, treatment did not affect killing-out percentage, but where the level of nutrition was lower a decrease of up to 1% was observed. In all trials treatment with the synthetic oestrogens resulted in an increase in pelt weight and in one trial this increase was up to 2 lb.

Implantation with hexoestrol and stilboestrol increased the size of the gut full and empty in two of the trials. The differences were reduced when the gut weights were corrected to 100 lb. empty live-weight. The weight of the thyroid gland or the total weight of the trachea, heart and lungs were not affected by treatment.

The approximate rate of uptake of hormone from a 12 mg. implant of stilboestrol was assessed by the decrease in the weight of dried tablet removed at slaughter from 30 to 200 days after implantation. The linear regression y (uptake in mg.)=3·029+0·039x (days from implantation) fitted the data best, giving an approximate average uptake over this period of 39 micrograms of stilboestrol per day.