In a factorial experiment, two protein concentrations and three patterns of feeding were administered to eighteen Large White × Wessex sows (three per treatment) in their second pregnancy. Treatments were repeated in their third pregnancy, when balance trials were conducted. The high protein diet (HP) (19·5% crude protein) contained 15% white-fish meal. The low protein diet (LP) (10·5% crude protein) contained protein of vegetable origin only. The pattern treatments involved intakes of 1·8 kg (L) 2·7 kg (C) and 3·6 kg (H) per day, the three pregnancy feeding patterns being HL, C and LH. Parturition results and lactation performance in the third reproductive cycle were similar to those recorded in the previous reproductive cycle (Pike & Boaz, 1969) reported earlier. Nitrogen retention in the third pregnancy was significantly higher in the HP sows(1606 g N)thaninthe LP sows(1082 g N) (P < 0·001). Intra-uterine nitrogen deposition in pregnancy was not affected by any of the treatments. Extra-uterine nitrogen deposition was significantly greater in the HP than the LP sows (P < 0·001). Dietary protein differences influenced extra-uterine rather than intra-uterine deposition of nitrogen in the pregnant sow, greater extra-uterine nitrogen deposition appearing to enhance subsequent lactation in this and the previous (Pike & Boaz, 1969) experiment. Protein utilization was more efficient in late than early pregnancy, suggesting that the feeding of higher levels of protein in late pregnancy should lead to greater efficiency over the whole pregnancy, provided energy intake is sufficient to promote optimum protein utilization.

Three experiments on the effects of sugars on milk production and live weight of cows are described. Two experiments each with twelve cows were of latin square design with 5-week periods. The third was a continuous treatment experiment of 11 weeks duration with twenty cows. All the animals were in mid-lactation. Performance on the basal diet of hay and concentrates was compared to that when the basal diet was supplemented with 10·7 Meal digestible energy daily in the form of sucrose or glucose monohydrate or concentrates.

Additional concentrates regularly increased milk yield, live-weight gain, solids-not-fat content of the milk, and yields of solids-not-fat and milk fat. Fat content of the milk was not affected.

Sucrose had a small beneficial effect on milk yield; the effect of glucose monohydrate on yield was small and indecisive. Sucrose depressed milk fat percentage; the effect of glucose on milk fat percentage varied between experiments. Both sugars increased solids-not-fat content of the milk, solids-not-fat yield, and rate of live-weight gain.

Over the longer treatment period in the third experiment milk fat content tended to recover partially for both sugar-supplemented rations. The effects on yield of milk and of milk fat did not alter. The effects on live-weight gain were established more decisively and the final order of the size of the beneficial effect of the supplements was: concentrates, glucose monohydrate, sucrose.

At the end of the third experiment rumen, contents from all cows were sampled by stomach tube. The concentrates supplement had no effect on the proportions of volatile fatty acids. Both sugars depressed the proportion of acetic acid and increased the proportions of propionic, butyric and valeric acids. In all cases except that of butyric acid, where the reverse occurred, the effect of sucrose was greater than that of glucose monohydrate.

A series of twenty-one nitrogen fertilizer rates ranging from 0 to 800 lb nitrogen/acre (897 kg/ha)/annum was applied on a pure S. 23 perennial ryegrass sward and on an S. 23 ryegrass sward containing S. 100 white clover. Total yields of herbage dry matter and crude protein from both swards at all the nitrogen rates were determined each year by cutting the herbage five times at approximately the same stage of growth on each occasion. Four-parameter growth curves relating herbage yield to nitrogen rate were fitted to the data, and are presented for the first 3 years of the experiment. On the pure-grass sward the response of dry-matter yield to nitrogen rate was almost linear between the 0 and 300 lb nitrogen/acre (336 kg/ha) rates, then it decreased steadily, becoming non-significant about the 500 lb/acre (560 kg/ha) rate. In contrast the response of crude-protein yield was virtually linear from the 0 to the 600–700 lb nitrogen/acre (673–785 kg/ha) rates. The inclusion of white clover in the sward increased the yields of dry matter and crude protein at the low nitrogen rates, but decreased the responses, with the result that the yields and responses of the grass + clover sward were not significantly different from those of the pure-grass sward at nitrogen rates above about 300 lb/ acre (336 kg/ha). In terms of profitability at present fertilizer prices the optimum nitrogen rate for dry-matter production on both swards was estimated to be 400–450 lb/ acre (448–504 kg/ha), whereas that for crude-protein production was greater than 600 lb/acre (673 kg/ha). The value of clover in a sward receiving nitrogen fertilizer is discussed.

Animals reared in constant ambient temperatures had significantly more skeletal muscle myoglobin than those reared in alternating temperature environments when the humidity was moderate or high. These differences did not exist when humidity levels were low. Comparisons ofthe effect of humidity level in constant ambient temperatures revealed high myoglobin in pigs subjected to moderate as compared to low humidity at 27°C, but humidity effects were nonexistent when the ambient temperature was 21 or 32° C. It is postulated that animals reared in alternating temperatures experienced intermittent and persistent development of tissue hypoxia and, asa consequence, had reduced aerobic metabolic pathways in muscle as compared to animals rearedinconstant ambient temperatures.

Moisture content of the coats of cattle, expressed as the percentage of the dry weight of hair, has been measured in a wide variety of environmental conditions in summer, springand winter. Strips of coat were clipped from 25 Jersey, 15 Zebu x Jersey crossbred and 9 Hereford heifers in a shed, in a climate room under warm, hot dry and hot humid conditions and outdoors both in sun and shade. Moisture content, weight of coat per unit area, depth of coat, skin and rectal temperatures, sweating and respiratory rates, air temperatures and vapour pressures were measured.

The mean moisture content of the coats varied in the different environments from 5·8 to 27·5 % and mean sweating rates from 28 to 438 g m-2 h-1. Moisturein summer coats out of doors in the sun averaged 11·2% and was about the same as that outof doors in the shade. In the shed, coat moisture was also low (average 11·8%) and amounted to less than half of the moisture content of clipped hair in equilibrium with a near saturated atmosphere. Herefords that had been fed a low plane ration from winter to summer, retained their long winter coats and these, in summer, had only half the moisture content of the short coats of normally fed Herefords. In the hot room, the moisture content of summer coats was usually higher than out of doors and varied around 18%.

The inner part of the coat had more moisture than the outer part and estimates of moisture gradients were made. Calculation of the contribution of sweating to total moisture in indoor environments showed that, at rapid rates of sweating, it was about 8% and was higher in winter andspring coats than in summer coats (Fig. 3). It was estimated that sun and wind reduced the moisture content of summer coats by about 3% in outdoor summer environments. The effect of sun and wind on moisture content of winter coats in the same environment was estimated at nearly 9%.

The results suggest that the site of evaporation was at the skin except in very hot humid indoor environments when some free moisture may have been present in the hair.

The intravenous (i.v.) infusion of solutions of ammonium salts into sheep produced a toxic condition in which the clinical signs, pathological findings and concentrations of ammonia in the venous blood were comparable with those found in urea poisoning, provided that the urea and ammonia toxicoses were induced over similar time intervals. Our results indicate that urea toxicosis in ruminants is due to the toxic effects of ammonia. Although the clinical signs resulting from the i.v. infusion of ammonium chloride, acetate and hydroxide showed some relationship to the basicity of the compounds, alkalosis did not appear to be a necessary prerequisite for ammonia toxicosis.

The tolerances of sheep to orally administered urea and i.v. infused ammonium salt solutionswere shown to be positively related to dietary nitrogen intake. These results and the observations reported by Payne & Morris (1969) that the concentrations of urea-cycle enzymes per unit of liver tissue were markedly affected by dietary nitrogen intake suggest that supplementation of ruminants grazing low-protein pastures with urea, occurs at a time when their tolerances to an over-dose of urea are minimal.

The i.v. administration of arginine and of y-amino butyric acid plus glucose did not appear to be of practical value in preventing urea poisoning.

Yield and growth analysis has been carried out on vining peas (variety Dark Skinned Perfection) sown at 43, 97 and 172 seeds/m2 at a rectangularity of 1:1. No difference wasobtained in the yield of green peas (at tenderometer reading 110) over this fourfolddifferencein sowing density.

At a high seed rate (172/m2) a high peak leaf area (8·3) was attained 1 week afterthe start of flowering but declined rapidly. The peak number of flowers and pods reached 1002/m2 at this density, but there was a greater wastage (34 %) by abscission than inthe lower seed rates which resulted in a similar number of pods/unit area being present at the time of vining for all densities.

In contrast, peas sown at low density (43/m2) resulted in a lower peak leaf area (4·3) but this occurred during the stage of pod fill; net-assimilation rate was somewhat higher also. Thus the yield of green peas may depend less on the ability of the plant stand to provide reproductive nodes than on its ability to produce photosynthate during the post-flowering period.

Iodine values, melting (slip) points and fatty acid analyses for back (‘bung’) and perinephric (kidney) fats from 114 pure and cross-bred pigs are reported.

In most cases the effects of breed were small, but half-Hampshire crosses showed a high proportion of pigs producing abnormally soft and highly unsaturated fats, though others were normal.

Although a general correlation existed between iodine value and melting-point the relationship broke down in some cases, and the ratio of monoene to saturated fatty acids of carbon chain length 16 and 18 is suggested as a better chemical index of softness due to causes other than dietary lipid.

Three experiments were carried out with adult sheep in order to estimate the effect of light and darkness in determining the incidence pattern of rumination.

In the first experiment the jaw movements of four sheep were recorded when they were housed in cages in a single room. Continuous records were made before and after black-out was applied to the room in order to investigate the effects of times of lighting and of feeding. The results showed that under these conditions the pattern of ruminating behaviour changed with the lighting system used and that the different feeding times had no effect upon rumination.

The first experiment was repeated with four sheep. Equal 12 h light or dark periods running from 10.00 and 22.00 h were applied and also days of continuous light or darkness. Food was given as equal meals at the beginning of each 12 h period. The results confirmed those of the first experiment and showed that rumination was greatest during the second half of each 12 h period of darkness. With permanent light or darkness rumination was least in the period from 10.00 to 16.00 h.

An attempt was made in the third experiment to impose a 16 h cycle on four sheep. The results showed no adaptation to a 16 h ‘day’. Instead, behaviour was circadian and probably based on cues external to the experimental room.

Thirty-six Hereford cross Friesian calves weighing on average 82.4 kg at an average age of 90 days were allotted in randomized blocks to a 2 x 3 factorial design. Castration by the open method was performed on half the number of calves and three dietary crude protein levels, 20, 14 and 11 % in dry matter were used in a mainly cereal concentrate diet fed ad libitum individually to the animals in stalls. Slaughter was at a fixed weight of approximately 420 kg.

Steers compared with bulls gained weight at a significantly slower rate and with less efficiency. Castration's greatest effect in reducing rate of gain occurred during the later stages of rearing when puberty in the bulls, as measured by a steep rise in seminal fructose, was associated with their relatively well maintained live-weight gain. The influence of testicular hormones was also apparent in the bull's carcass with its heavier head, horn and hide and significantly higher proportion of lean and lower proportion of fat in the side.

Dietary protein level affected rate of gain in both bulls and steers but at each level bulls performed better than steers. With circumstances similar to those in this experiment, a 14 % crude protein level in concentrate dry matter appears adequate for both categories up to a live weight of circa 270 kg and a reduction to 11 % thereafter. The effect of protein level on tissue proportions of the side and carcass composition generally was minimal.

Calorimetric experiments were made with a complete extruded diet for ruminants, ‘Ruminant Diet A’ prepared by Messrs U.K. Compound Feeds Ltd. Twelve determinations of energy and nitrogen retention were made using sheep and it was found that the diet had a metabolizable energy value of 2–32 kcal/g organic matter, and the net availabilities of its metabolizable energy were 42–7 % for fattening and 68–0 % for maintenance. These values agreed well with those predicted from equations published by the Agricultural Research Council. On a dry basis the starch equivalent was 38–3 %.

A study was made of the live-weight gains of four ¾-bred Brahman and four purebred Hereford steers over a 12-month period. At 950 lb live weight each animal was slaughtered, after which the carcass characteristics of the two breed types were compared.

The Herefords showed the highest live-weight gains over the whole year but during autumn, when nutritional levels were poor, the Brahmans had an advantage in average daily gain.

Although both breed types varied greatly in body conformation, there was little appreciable difference in weight distribution of joints on the carcass. A higher dressing percentage was observed in the Brahmans, this being attributed to their smaller alimentary tracts. The Brahmans had a greater carcass muscle and smaller carcass fat content than the Herefords. The necessity for fat trimming of the Hereford carcasses reduced their calculated retail value index to a level below that of the Brahmans in a market which discriminated against excess fat.

Thus it was concluded that even in a temperate climate, Brahman cattle can have a place in improving productive efficiency. Apart from the heterosis developed in crossbreeding, benefits should flow from the Brahmans superiority on poor pastures and the improved production of lean meat on their carcasses.

On seven separate occasions during a year, 24-h studies were made on the grazing behaviour of four ¾-bred Brahman and four purebred Hereford steers in the cool temperate New England region of northern N.S.W.

Although both breeds spent approximately the same time grazing, the Brahmans ruminated for shorter periods and thus had a lower ruminating time to grazing time ratio than the Herefords. No signs of cold stress were observed in either breed even though the dry bulb temperature frequently fell below freezing point. However, the Herefords sought shade more than the Brahmans when the black body temperature exceeded 32°C.

It is concluded that a climate such as that of New England, where winters are cold, should in no way adversely affect the performance of Brahman-type cattle, as judged by their behaviour.

The growth characteristics of root systems were studied in the wheat varieties Chinese Spring' Hope and the chromosome substitution lines of Hope into Chinese Spring. The growth patterns varied considerably between the lines and this was due to the fact that the plants formed different numbers of tillers and grew for different periods of time. A correlation existed between the development of the shoot and root systems although some lines differed widely in their shoot root ratios. Differences between the lines in the early stages of growth were small and they reacted uniformly to different levels of phosphorus supply. The relation between shoot and root growth was also shown by the fact that the conclusions from genetical analyses were very similar. These showed that the method of control was largely additive in nature. It was concluded that variations in shoot and root characteristics were markedly influenced by single genes affecting the duration of the vegetative growth period as well as by polygenic systems.

Animal production in grazing experiments depends both on treatment and on stocking rate. Production at optimum stocking rate is the only valid measure of treatment effect and treatment comparisons should be based on this criterion. Since optimum stocking rates are unknown these comparisons cannot be made directly, instead they must be inferred from the results obtained with the stocking rates actually used. This requires that some form of production stocking rate relationship be postulated. This paper suggests a form for this relationship and considers its implications on experimental design and particularly on the number of stocking rates per treatment.

Emergence trials of five different seed lots each of cv. Lincoln and Kelvedon Wonder at six centres provided 27 different sowing treatments. Although mean emergence between treatments varied, the rank order of the lots remained almost constant. The results of seedling evaluation and conductivity vigour tests correlated well with field emergence, with neither test superior to the other. Grades of vigour were established and related to the performance of the seed lots in the field trials.

Twenty-eight Hereford cross Friesian heifer calves aged 3 months were allocated in randomized blocks to two main treatments, namely, ovariectomy (spaying), performed by flank laparotomy, and anabolic steroid oral administration (Ethylestrenol). The cattle were tied in stalls and individually fed ad libitum on a ‘barley-beef’ type cereal mixture until slaughtered weighing approximately 340 kg.

Ovariectomy reduced overall rate of live-weight gain and food conversion efficiency but differences were not significant. Spayed heifers, however, grew significantly taller than entires. Although fat and bone proportions of the side were increased slightly, carcass grading and composition were not appreciably altered by ovariectomy.

Steroid treatment failed to improve performance but lean content of the side was slightly increased. This failure in response may have been due to incorrect dosage.

Tritiated water (TOH) space was determined in sixty-one sheep of known age (3 days to 18 months). Representative samples of the minced carcass were subsequently analysed to determine body composition (water, fat, protein, ash and energy). The regressions of the weight of the various body components on TOH space and body weight reported here gave equations suitable for prediction. These were similar to equations derived from published results for adults. Combining data on young sheep and adults gave broadly based equations that could be used to predict the body composition of healthy sheep of all ages from 3 days to adults.

The vegetative growth, flowering and seed yield of three cowpea varieties—Adzuki, Mala and New Era—with contrasting yields, were compared in one field and two greenhouse experiments. In the field the plants were spaced so far apart that they did not form a closed stand, but were effectively individuals, like the potted plants used in the greenhouse experiments. In all experiments New Era yielded most followed by Mala, although the differences between these two varieties were not significant, and Adzuki least.

Seed yield and vegetative growth were not simply related. New Era with the highest seed yield had the largest vegetative dry weight, leaf area and leaf area duration (D), followed by Mala, with Adzuki always least in each parameter. However, the superiority of New Era in total dry weight and leaf area was much greater than in seed yield. Mala and Adzuki were more efficient than New Era in converting dry matter into seed. Large fractions of current assimilates moved from the leaves to the seed of Adzuki and Mala than of New Era.

Varietal differences in relative growth rate, net assimilation rate, or leaf area ratio were too small to account for varietal differences in seed yield.

New Era and Mala produced more flower buds than Adzuki. However, Adzuki developed the largest proportion of ripe fruits, but had more aborted seeds/fruit than New Era and Mala. Thus, increased flower production and fruit formation did not increase the production of mature seeds. Therefore, little would be gained by breeding or selecting for increased flower production. The heavier seeds of Mala and New Era compared with those of Adzuki contributed greatly to their larger yields. At the spacing of 3 ft x 1 ft used in the field, the leaf area index (L) and leaf area duration (D) were suboptimal, and closer spacing should increase yield.

When open flowers were removed from cowpea plants for periods between 3 and 12 consecutive days beginning from the first day of anthesis, more flowers opened on the deflowered than on the untreated plants, thus compensating for those removed. However, most of these extra flowers dropped prematurely.

In experiments in the greenhouse or on dry-season irrigated plots, deflowering for up to 9 days did not decrease the seed yield of the varieties Adzuki or Westbred. In an early-season field experiment, deflowering of Westbred did not decrease the seed yield unless repeated for 12 days. All periods of deflowering Adzuki decreased the seed yield, and the longest period gave the smallest yield.