1. The intakes of herbage organic matter (OM) and digestible organic matter (DOM) by twenty dairy cows were measured during two periods of strip grazing on one pasture, in spring and late summer of the same year.

2. Results from the first 5-day measurement period in the spring suggested that intakes at this time were restricted primarily because the cows had difficulty in gathering the short herbage. Measurements on ten of the cows continued during a further 5 weeks while the digestibility of the OM of grazed herbage declined from about 80 to 68%. There was a fall of about 20% in DOM intake by the cows during this period; one-quarter of the fall could be ascribed to a reduction in OM intake and the remainder to the decline in digestibility as such.

3. Intakes were measured during two weeks in late summer and were compared with those measured during two weeks in the spring when the digestibility of the grazed herbage was similar. Intakes of DOM expressed as lb./lb. live-weight0·73 were the lower by about 10% in the late summer, or by from 10 to 20% in terms of DOM available for production when allowance had been made for maintenance requirements. This finding is discussed in relation to practical experience of the feeding value of autumn grass.

1. Nitrogen balance studies have been conducted on 16 early-weaned calves given four diets containing groundnut meal or herring meal, the protein of which had been rendered soluble or insoluble by different methods processing.

2. There were highly significant differences in nitrogen retention between ‘soluble’ and ‘insoluble’ herring meals but no differences between ‘soluble’ ‘insoluble’ groundnut meals.

3. ‘Insoluble’ herring meal gave retention values which tended to be higher (significantly so, in one experiment), and ‘soluble’ herring meal gave values significantly lower, than either type of groundnut meal. Mean daily live-weight gains tended to follow the same pattern.

4. Blood-urea concentration was significantly lower on the diets containing herring meal than on those containing groundnut meal but within each type meal did not differ according to solubility.

5. These results are discussed in the light of in vitro studies on the effect of pH on protein solubility.

6. It is concluded that solubility is of minor importance in groundnut meals but of major importance in fish meals when these are included in early weaning diets for calves.

7. Under conditions of low or ‘potentially low’ solubility the amino acid content of the protein source appears to be of considerable significance.

1. Rumen-ammonia concentration, pH of rumen liquor and blood-urea concentration have been measured at intervals after feeding in six calves given diets containing ‘soluble’ groundnut meal, ‘soluble’ herring meal or ‘insoluble’ herring meal as the major protein source.

2. There were no significant differences between diets in any of the measurements examined. A difference approaching significance was, however, observed between ‘soluble’ herring meal and the other diets in the direction and extent of the change in rumen-ammonia concentration during the first hour after feeding.

3. On all diets, pH of rumen liquor fell to a value in the region of 5·5 immediately after feeding and increased gradually to around 6·5 during the following 8 hr. Rumen-ammonia concentrations were at all times very low.

4. There was no significant residual correlation between changes in blood-urea concentration and the corresponding changes in rumen-ammonia concentration.

5. Rumen-ammonia concentration increased markedly on the ‘soluble’ herring meal diet when the nitrogen intake of the animals was increased by 50%; under similar conditions, only slight increases in this measurement were observed on the other diets.

6. Thesefindingsare discussed in relation to the efficiency of utilisation of dietary nitrogen.

Records of cows each milked in two different herds have been used to estimate a component of variance due to cows that is free of variation arising from cow-by-herd interaction effects. By making use of a prior estimate of within-herd repeatability the variance component due to cow-by-herd interaction effects was estimated, and found to represent 35% of the total within-herd variance of butterfat yields and 9% of that of butterfat percentage records.

Wastage and culling rates in Private Milk Records herds during a three year period, October 1957 to September 1960, were estimated from data collected byfieldsmenduring one week in each month.

Total deaths and disposals among cows fell from 29·3% in 1957–8 to 23·4% in 1959–60 due mainly to reductions in the sales of surplus cows, non-attested cows and reactors to tuberculin. Wastage and culling among cows tended to be higher in winter than in summer. The rate of loss tended to increase in successive lactations and the percentage of animals sold for dairying fell from the third lactation onwards whilst disease, accident and old age became increasingly important reasons for culling.

Total deaths and disposals among heifers fell from 17·3% in 1957–8 t o 11·3% in 1959–60 due mainly to a reduction in the sale of stock for purposes other than dairying as ‘surplus’ or ‘fat’, and to a fall in the numbers sold for dairying for miscellaneous reasons. There was a peak in heifer disposals in early summer.

It is estimated that the average herd life in P.M.R. herds from first calving o t disposal is between 3½ and 4½ years and that average total productive life from first calving to death is between 5 and 6 years.

1. Rates of live-weight gain from 2 to 96 weeks of age are compared in twin cattle of 8 breeds and crosses. The 258 animals in the trial consisted of 77 pairs of one-egg (MZ) and 52 pairs of two-egg (DZ) twins. All were females.

2. Between collection during the first week after birth, and 36 weeks of age, treatment of animals was uniform. After this some animals were grazed and others remained housed, depending on their date of birth. Members of each twin pair were, however, always treated alike. Between 36 and 96 weeks of age grazed stock gained 62 lb. more weight than housed stock. This difference was allowed for in making breed comparisons.

3. The trial period was divided into six stages. The most rapid gains were made between 24 and 36 weeks of age (1·43 lb. per day) and between 36 and 52 weeks (1·48 lb. per day). Earlier and later growth rates were about 30% less than these.

4. Rates of gain varied from 1·10 lb. per day in Ayrshires to 1·38 lb. per day in Friesian × Shorthorn crosses. The Friesian and its crosses with Shorthorn generally made fastest gains throughout the trial. The Ayrshire was slower than the rest. The Shorthorn and its crosses with Hereford and Ayrshire were intermediate in performance.

5. Ratios of within-pair variance in MZ and DZ twins indicate that differences in performance are most strongly dependent on genetic differences-at 12 to 24 and 52 to 72 weeks of age.

Four groups of Scottish Blackface ewe lambs were reared in the period 11–52 weeks old under different regimes. The regimes differed in the age of the lambs at which they were separated from their dams and whether having been separated they were together in a field and/or penned together n i a sheep shed.

These regimes caused differences in social behaviour among the four groups and also resulted in the groups adopting different parts (home ranges) of an enclosed 350 acre hill pasture. The various home ranges within the pasture are dissimilar environments and it is argued that home range and method-of-rearing effects will be confounded making statistical comparisons between the different rearing treatments impossible.

Two groups of autumn born Sussex-Ayrshire cross cattle balanced for sex were raised from about 400 lb. live-weight to slaughter either on (A) a system based on summer grazing and winter feeding on silage, hay and limited barley or (B) on an indoor system based entirely on concentrates and hay.

Group A produced carcasses which averaged 531 lb. in 616 days with a higher muscle content than Group B whose carcasses weighed 496 lb. after 528 days. Steers grew significantly faster than heifers on both treatments. Maturation of Group A was delayed by scarcity of pasture in September.

From feed intakes, including direct estimates of feed intake on pasture, it was calculated that despite the check suffered by Group A, S.E. per lb. of gain was similar on both treatments and better for steers than heifers.

Since the cost per unit of feed was lower for Group A this group showed the higher margin over direct costs.

A trial is described in which normal rations containing oleandomycin at 12½ and 25 g. per ton of meal and without the additive were given to females and castrates which had previously received creep feed with and without oxytetracycline.

A total of 48 pigs were individually fed on the rations from 50 to 200 lb. live-weight, a restricted scale of intake based on live-weight being adopted.

Between 50 and 100 lb. live-weight rate and efficiency of gain were significantly better in pigs which had not received antibiotic in the creep feed. No other treatment had any significant effect on performance.

Oleandomycin did not influence carcass measurements or dressing percentage. Minimum depth of fat at the mid-back was significantly greater in pigs which had received oxytetracycline in the creep feed while castrates had a significantly greater depth of fat at the shoulder and mid-back compared with females.

Pigs receiving the lower level of oleandomycin had significantly lighter kidneys than the control animals. Other visceral weights were not significantly influenced by the antibiotic, but females had significantly heavier kidneys, spleen and liver weights than castrates.

Current rates of inbreeding due to A.I. and natural service are estimated in Pedigree Welsh Black cattle.

Since 1948, 27 sires have been used in A.I., 16 of which have a common male ancestor. Four sire-son pairs and two pairs and one trio of half-brothers have been in recent use. Two-thirds of the bulls and heifers bred by A.I. and registered in 1960 were sired by 4 bulls. Since 1954 progeny of two A.I. sires who are father and son, were preferred for registration.

Pedigree analysis of a sample of 128 bulls showed that those bred by A.I. were, on average, 2·80% inbred, compared with 2·32% for those from natural matings. In a sample of 166 heifers corresponding values were 0·82% and 1·17%.

One herd, through natural service, contributed 12% of the genes of a sample of bulls and heifers. Four other herds were outstanding for the number of males they provided. The average inbreeding of their young, registered bulls was estimated to be 7·04%.

The widespread use of the descendents of one bull, both in A.I. and natural service, led to 94 cases of inbreeding in the third and fourth ancestral generations of the pedigrees of animals in the sample.

It is concluded that the short term consequences of using a small number of bulls in A.I. measured in terms of inbreeding, are no different from those in natural service and that inbreeding depression in traits of commercial importance would be undetectable.