Colostral whey protein levels do not change during the first 4 hr from the start of parturition when suckling is prevented. Both early and late-born piglets returned to the sow at the end of this period are able to suck colostrum of a high protein concentration. Removal of piglets from the sow and the presence of an attendant did not affect the farrowing process.

Repeatability estimates for various maternal characteristics were calculated for 301 inbred, 150 outbred and 135 linecross Large White sows each with two litters. The estimated repeatabilities did not differ significantly between the three kinds of sow and the arithmetic average of the values obtained were as follows: number of pigs born alive 0·24; number of pigs born dead 0·05; total birth weight of litter 0·25; average individual birth weight 0·41; number of pigs alive at 50 days 0·07; total litter weight at 50 days 0·14; average individual weight at 50 days 0·15.

The linecross sows produced and weaned more pigs than the outbred sows, which in turn performed better than the inbred sows. Changes in performance from the first to the second litter were similar for all three groups of sows.

The effect of gradually replacing barley with swedes or potatoes on intake of digestible dry matter and on the volatile fatty acid (VFA) composition of liquor was measured in an experiment with eight female and four castrated male sheep approximately six months old. The total intake of digestible dry matter was greatest when rolled barley was given at two-thirds of estimated maximal intake and roots given ad libitum. The intake of digestible dry matter was reduced to 80% of the highest intake when all the barley was substituted with swedes and to 70% of the highest intake when all the barley was substituted with potatoes. Replacing barley with roots had little or no influence on VFA composition.

Twenty-four Southdown and 24 Welsh Mountain year-old female sheep, half on high-plane and half on low-plane nutrition, were shorn and given two acute cold exposures in climate chambers. For 2 weeks before and 2 weeks between exposures the sheep were kept in a subcritical (+ 8°C) or a thermoneutral (+30°C) environment. Before the temperature treatment each sheep received an injection of Brucella abortus vaccine. Blood samples were taken during exposure to + 8°C and + 30°C and during the acute cold exposures for estimation of free fatty acid (FFA), protein-bound iodine (PBI), glucose, acetone, serum protein and antibody levels. FFA and glucose levels alone were measured in 32 similarly treated Scottish Blackface sheep.

1. Low plane sheep had higher PBI levels at all temperatures, and higher glucose levels during acute cold exposure than high plane sheep. Otherwise most major effects were attributable to ambient temperature.

2. At +8°C the PBI, FFA, glucose, serum protein and acetone levels were higher than at + 30°C.

3. Blackface sheep had lower FFA and glucose levels than Southdown and Welsh sheep at both temperatures.

4. During acute cold exposure, PBI, acetone and FFA levels increased further. PBI levels were highest in sheep previously at + 30°C, and acetone highest in sheep previously at + 8°C. Very high FFA levels were recorded, especially in sheep not previously cold-acclimatized.

5. Glucose levels increased initially, but fell towards the end of acute exposure, suggesting that relatively less carbohydrate and more fat was utilized for energy metabolism during this period.

6. Serum protein levels fell during acute exposure, possibly because protein catabolism increased. The proportions of albumin and γ-globulin increased and decreased respectively.

7. No effects of temperature on antibody levels were detected.

Samples of sheep's milk were used to study the occurrence of β-lactoglobulin variants of fast or slow electrophoretic mobility. The distribution of variant types between a sample of daughters and their dams was in general accord with simple Mendelian expectations for two autosomal co-dominant alleles.

1. Two experiments have been carried out to study the nutritive value of dilute solutions of fatty acids (consisting mainly of ammonium acetate) when incorporated in the diet of lactating Jersey cows.

The first, a continuous trial, extended over a total of 17 weeks and involved five pairs of cows. One cow in each pair received the treatment and one the control diet. The second trial, of change-over design, involved four pairs of cows; one cow in each pair received one or other of the experimental diets alternately over four 28-day periods.

2. The cows received basic diets comprising hay ad libitum and concentrates regulated according to milk yield. On the control treatment cows received water and a concentrate containing an appropriate percentage of groundnut cake; on treatment cows received a dilute solution of salts and an ‘all-cereal’ concentrate. The treatment provided cows with approximately 30% of their total DCP intake as ammonia-N and with 270 to 310 g of acetate and 43 to 49 g of propionate/day from the salt solution.

3. Solutions of salts have been offered to the cows at various concentrations in the range 0·25 to 2·6% (w/v) as a substitute for drinking water. Nineteen of the 20 cows consumed solutions of 1·4% concentration in normal quantities equivalent to water.

4. Treatment was associated with an appreciable depression in the yield of cows producing 13 to 14 kg of milk per head/day, but had little effect on the yield of cows producing 10 to U kg or less. This result has been discussed with reference to the role of the ammonia-N as a substitute for protein-N.

5. Treatment significantly increased the fat content of the milk produced by these Jersey cows above the high control level of 5·4%. Total milk fat production was also increased. This result has been discussed with reference to the role of acetate in dairy cow diets.

Data were obtained on 3028 lambs born during five successive years from 1961 to 1966 at Ras El-Hekma Desert Research Station in the Western Coastal Egyptian Desert. Breed groups involved in the study were Hungarian Merino, Syrian Awassi, native Barki sheep, and nine of their crosses. The characters studied were birth weight, weaning and yearling weights, pre- and post-weaning average daily gain and yearling greasy fleece weight. The effects of breed group, year of birth, sex, age of dam and type of birth on these characters were investigated.

The results obtained showed that Barki lambs excelled Merino lambs in all the traits related to body growth. Merino lambs, on the other hand, excelled Barkis in fleece weight. Barki lambs also excelled Awassi lambs in all traits except birth and weaning weights. In all characters except pre-weaning gain, the first cross of Merino and Barki (½M½B) was markedly superior to all the other crosses and pure breeds. The two third-crosses, ⅜ M ⅝ B and ⅝ M ⅜ B, were similar to each other in their productive traits and were slightly inferior to the first cross. The two back-crosses, ¼M¾B and ¾M¼B, were markedly different from each other, the former being better than the latter. The three-eighths Merino group is suggested for developing a new strain of sheep for the semi-arid regions. The effects of the environmental factors on the six characters studied were all highly significant except for the effect of sex on fleece weight and the effects of age of dam and type of birth on growth from weaning to yearling ages. The most important factor affecting the different traits was year of birth. Type of birth and age of dam were important sources of variation only for the characters studied till weaning age, but became of little importance thereafter. The effect of sex was pronounced only on yearling weight.

An experiment was undertaken to examine the possibility that progressive adjustments in tissue insulation on the trunk might occur following repeated wind cooling. Two sheep were exposed at right angles to an air flow of 12 mph for 6 hr daily on each of 7 consecutive days.

When first exposed to the wind the heat loss from the fleece-covered surfaces increased due to a reduction in insulation and apparently increased vaso-dilatation. After the first day there was a progressive increase in surface vaso-constriction before exposure and a gradual decrease in the extent of the vaso-dilatation during exposure. The results indicate the possibility of centrally-induced peripheral adjustments in blood flow occurring on the trunk of the sheep in response to repeated wind cooling.

1. The effect of feeding a salt solution containing ammonium acetate on the yield and fatty acid composition of cows' milk fat has been studied.

2. The trials involved eighteen lactating Jersey cows. In the first trial one group of 5 cows was fed the treatment diet throughout an experimental period of 10 weeks and another group of 5 cows acted as controls. In the second trial which extended over four 28-day periods, two groups of 4 cows spent alternate periods on treatment or control diets. The overall results of the two trials were in agreement.

3. The outputs of C4-C14 acids and of palmitic acid per kg of milk yielded were greater than the intakes. The output of C18 acids was less than the intake per kg of milk yielded. These observations were noted on both treatment and control.

4. Treatment resulted in an increased secretion of C4-C14 acids and of palmitic acid and a decreased secretion of C18 acids per kg of milk yielded.

5. The results have been discussed in the light of present knowledge concerning the synthesis of fat in the mammary gland.

Records on 695 lambs were collected over a period of 5 years from 1961/62 to 1965/66, at Ras El-Hekma Desert Research Station, 230 km west of Alexandria. The characters studied were birth, weaning and yearling body weights, pre- and post-weaning daily gains and greasy fleece weight.

Birth, 120-day and 365-day body weights were 3·4, 18·2 and 33·4 kg respectively. Greasy fleece weight at 16 months of age was 3·29 kg. Heritability estimates of birth, weaning, yearling weights, pre- and post-weaning daily gains and greasy fleece weight were 0·22, 0·45, 0·41,0·45 and 0·29 respectively. Genetic and phenotypic correlations between birth, weaning and yearling weights were all positive and significant. Genetic correlations between fleece weight and body characteristics were negative and low.

Histological examination of the rumen wall in intensively managed beef cattle confirmed the superficial nature of many of the lesions present and failed to reveal evidence of secondary bacterial infection. Of the lesions described, only intra-mucosal abscesses and their subsequent erosions proved to be significantly related to the occurrence of hyperkeratosis of the rumen mucosa. The remaining lesions, vacuolation of the stratum granulosum, acute microscopic ulceration, congestion of the submucosa and the presence of leucocyte aggregations in the submucosa, were all independent of this hyperkeratosis.

A survey of albumin polymorphism in the major breeds of cattle in the British Isles is described. Four and probably five alleles have been found. AlbA is the common type in all breeds. AlbB occurs with less than 1 % frequency in all breeds except Sussex and Charolais, where it has a frequency of 12% and 16% respectively. The possible implications of this finding are discussed. The other alleles AlbC(Ed) and AlbD are extremely rare, and are confined to a few animals each within one breed. AlbG has been tentatively proposed as the name for a new albumin type.

The ability of two groups of six Merino wethers aged 6 and 66 months to digest a lucerne ration was examined in order to detect possible biases in the use of faecal nitrogen as a faecal index substance. Earlier work with this technique had indicated a difference in selectivity between young and older sheep. No difference in ability to digest the ration was observed and it was concluded that the earlier observation was not an artefact in the faecal nitrogen technique. Oesophageal fistulae were prepared in 120 sheep differing in breed, sex, age, strain and previous history. Determinations were made of the nitrogen content, and in one experiment of the in vitro digestibility of the diet selected by sheep grazing various pastures. Significant differences in the nitrogen content of the diet selected by sheep varying in breed, age and previous grazing history were recorded on some pastures on some occasions but not on others. No significant differences were observed between sheep varying in strain or sex. No reason could be suggested for the occasional differences between groups in the nitrogen content or digestibility of the diet selected, but it appeared unlikely that it would be a major source of variation in the productivity of the different groups at pasture.

1. Twenty-four Southdown and 24 Welsh Mountain year-old female sheep, half on high plane and half on low plane nutrition, were closely shorn and given two short acute cold exposures (−20°C, 4 mph wind) in climate chambers. For two weeks before the first acute exposure half the sheep were kept at a moderately cold temperature (+8°C) and the remainder at a thermoneutral temperature (+30°C). During the next two weeks between acute exposures these temperatures were reversed for each group of sheep.

2. Resistance to body cooling during acute cold exposure was significantly greater after exposure to + 8°C. This was attributed to acclimatization. No further acclimatization resulted from acute cold exposure in addition to chronic moderate cold exposure.

3. Sheep which had been kept at +8°C cooled 33% more slowly than those which had been at + 30°C. High plane sheep cooled 34 % more slowly than low plane sheep. Southdowns cooled 32 % more slowly than Welsh sheep, but the Welsh sheep showed relatively greater acclimatization on low plane nutrition.

4. Compared with Scottish Blackface sheep given similar temperature treatment in an earlier experiment, the Southdowns and Welsh showed less initial cold resistance and less capacity for acclimatization.

Year, type of gestation (single or twin foetuses) and age of foetus all had highly significant independent effects on both foetal weight and length (P>0·01). Twin foetuses were both longer and heavier than single foetuses at 21 to 30 days post coitum. Continuous illumination, continuous darkness and intermittent light appeared to reduce foetal length and weight (P>0·05). Control foetuses were longer and heavier than those on other treatments. Neither feeding level (75 to 150% N.R.C. maintenance requirements) nor body weight of the dam had significant effects on foetal size within the age range studied.

Twenty-four sows from three nutritional regimes imposed until weaning of their third litters were used to investigate the influence of weight and body condition on ovulation rate.

For low-, medium- and high-plane sows respectively, mean corpora lutea numbers at 3 to 6 days post coitus were 13·8±0·78, 16·4±0·87 and 15·2±1·01 (not significantly different); conception rates at first service were 50, 87·5 and 100% percentages prenatal mortality were 36·1±7·95, 67·2±7·26 and 41·7±7·26, and mean numbers of pigs born alive were 9·0±1·19, 5·2±1·09 and 8·8±1·09.

Pooled data indicated no significant effect of body weight but a significant effect of weight loss during the preceding lactation on ovulation rate (P<0–01).

An experiment to test the effect on the voluntary food intake of lambs of giving diets containing 0, 20, 40 and 60% of either coarse or finely ground oat husks, in either a loose or pelleted form, is described and the results discussed. The results showed that voluntary intake was uniformly depressed with increased dilution of the diet with oat husks when the oat husks were coarse and the diet given loose. However, when the oat husks were finely ground and when the diet was pelleted the response to dilution was much modified and in the case of older, heavier lambs intake initially increased with dilution. It is concluded that ruminants may sometimes be able to respond to increased diet dilution so as to maintain their maximum digestible-energy intake but that the attempt is often thwarted to varying degrees according to the physical form of the food. An hypothesis is suggested for the pattern of response in food intake to be expected according to the type of food given.

Eight research and teaching centres have co-operated in an experiment involving 132 sows. Six treatments were used, combining three levels of feeding in pregnancy with two in lactation. Pregnancy treatments were High 3−2 kg meal/day, Medium 2·4 kg/day and Low 1·6 kg/day; in lactation either a high level, 4·1 kg plus 0·2 kg/pig (h) or a medium level, 2·3 kg plus 0·2 kg/pig (m) were given. The sows were maintained on the same nutritional regime for three parities although inevitably some sows were lost before the completion of the trial. Sow live-weight gains in pregnancy were directly related to feed intake; in lactation, losses in sow live weight were dependent on gains made in the previous pregnancy and on the level fed while suckling. After the first parity, in which animals fed the low level in pregnancy tended to produce larger litters (though the difference was not significant), there were no differences in numbers born attributable to treatments.

Increases in the feed intake of sows in pregnancy resulted in consistent and significant increases in the weight of the pigs at birth. This increase in birth weight also resulted in an increase in weight at weaning in the second and third parities. Level of feeding in lactation, which had a highly significant effect on sow live weight, had much less influence on weaning weights of pigs. There were no consistent pregnancy × lactation interactions, the effects of treatments in the two phases being additive.

An assessment is made of the relative efficiency of the six treatments and the value of the experiment is discussed in relation to other studies concerned with sow nutrition.

Digestibility was estimated in vitro from a total of 167 oesophageal fistula samples collected over a period of 16 to 24 months from adult sheep grazing eight Phalaris tuberosa-Trifolium repens pastures stocked continuously at rates of from 2·5 to 37·1 sheep per ha. Corresponding estimates of the nitrogen content of the faeces and of the fistula samples, the live weight and faecal output of the sheep, and of the herbage availability of the pasture were obtained.

The observations were stratified on the bases of stocking rate, digestibility, month of the year, herbage availability or organicmatter intake. Relationships between digestibility estimated by the fistula technique and faecal nitrogen content (model B) and between digestibility and faecal nitrogen content, nitrogen content of the dietary dry and organic matter, and faecal output per unit live weight (model A) were calculated for each stratum.

There were significant differences between relationships derived for the various stocking rates, levels of digestibility, times of year, levels of intake and levels of herbage availability; predicted values of digestibility for given values of the independent variables differed by as much as 20 units of digestibility. Model A was substantially more precise than model B.

Differences between estimates of digestibility, derived by the fistula technique and by a general faecal nitrogen—digestibility relationship, established by Lambourne and Reardon (1963a) were calculated. The differences were related to digestibility and to herbage availability.

The implications of these results are discussed and it is concluded that faecal nitrogen content is not a satisfactory index of the digestibility of the diet selected by grazing sheep.

Shorn Southdown and Welsh Mountain sheep on high or maintenance levels of nutrition were subjected to two acute (−20°C; 4 mph wind) cold exposures in climate chambers. Before and between exposures the sheep were kept in either a cold (+8°C) or a thermoneutral (+30°C) environment.

1. At +8°C, all the sheep shivered and showed sustained vasoconstriction and elevated heart rates.

2. At + 30°C, heart rates, skin temperatures on the extremities and muscular tone were all consistently higher in sheep which had previously been kept at +8°C.

3. During cooling, the onset of vasoconstriction and increase in heart rate were both delayed in sheep previously kept at + 8°C.

4. These effects (2, 3) were retained for at least 2 days but less than 12 days after the sheep returned to thermoneutrality. They decayed faster than the increased resistance to body cooling produced simultaneously in the same sheep (Sykes and Slee, 1969), since this was still detectable after 2 weeks.

5. Breed differences were mainly small.

6. It was concluded that acclimatization induced by chronic cold exposure was associated with a temporary increase in basal metabolic rate.