The calving dates of spring-calving cows in New Zealand Angus and Hereford herds, taken from 350 and 240 herd-years respectively, and the intercalving intervals (CI) of cows in 95 Angus and 73 Hereford herds have been summarized. The relationships of each CI with the calving date which initiated it were also analysed. Results for each breed were analysed taking account of district, herd, year and cow age (in years), a total of 35 890 Angus and 22 397 Hereford records being used. The first-calving date (FCD) was identified for each herd-year, and 0·82 of Angus and 0·75 of Hereford cows were recorded as calving within 60 days of the FCD. On a herd basis, proportionately only 0·27 of Angus and 0·15 of Hereford herds had calving spreads of 80 days or less (defined as the time from the FCD to the last calving date). With barren years ignored, the CIs of cows averaged 370 days (Angus) and 368 days (Hereford). Two-year-old cows had on average a CI of 12 (Angus) or 7 days (Hereford) longer in 1974-75 than older cows, and the differences were both 12 days in 1975-76. Regression analyses showed that, on average, the later the calving date within a herd-year and age group, the shorter the subsequent CI. For cows calving early in the first year, the CI increased by 7 days for Angus and 5·4 days for Herefords for each 10 days before the mean calving date for the breed. There were significant effects of district and cow age on the regression estimates. The overall regressions were not consistent with those derived from British beef industry data.

Data records from 556 beef heifers which included age at first oestrus (AFE) were used to test the null hypotheses: 1) daylength at birth is not a determinant of AFE in beef females; and 2) there is not an association between the day on which first oestrus occurred and the lunar phase.

The effect of daylength at birth was measured by forming a variable, X1 where X1 = sine (X1′ 360/365·25)°, and including it among the set of variables in a multiple linear regression equation with AFE as the dependent variable. The resultant estimated coefficient on X1 was -3·617 with a standard error of 21·32, and led to the conclusion that daylength at birth was not a factor which affected AFE in this group of beef heifers.

The lunar phase hypothesis was tested by forming the frequency distribution of the 556 observations of first oestrus over the 30-day lunar cycie. The chi-square test was applied with the theoretical (hypothesized) distribution being the uniform distribution. The value of the test statistic was such that the null hypothesis would not be rejected even with an a value approaching 0·50. Additionally, coefficients of autocorrelation calculated for lag phases of 7, 14 and 21 days were quite small. Thus it was concluded that the occurrence of first oestrus was uniformly distributed over the lunar cycle.

Lifetime maternal records were collected from 116 Red Poll cows born over a 12-year period. Estimates of mature cow weight (A), maturation rate (K) and lifetime maternal performance characters (years in herd, YH; number of calves weaned, NC; total calf weight weaned, TW; total calf weight plus mature cow weight produced, TW + A; average calf weaning weight, AW; calf weight weaned per year in the herd, TWIYH and predicted cow metabolizable energy (ME) required per kg beef produced, MEITW + A) were calculated to study the relationship between cow growth characters and maternal performance. Calf weights were adjusted to a steer basis. Reproductive management practices consisted of breeding heifers to calve as 2-year-olds; cows failing to calve in two successive seasons were culled. Mean mature cow weight was 554 (s.e. 6) kg with a mean maturation rate of 0·059 (s.e. 0·001) per month. The correlation between A and K was −0·69. Means for lifetime maternal characters were: YH, 5·1 (s.e. 0·2); NC, 4·7 (s.e. 0·2); TW, 1187 (s.e. 54) kg; TW + A, 1741 (s.e. 55) kg; AW, 252 (s.e. 1·7) kg; TWIYH, 228 (s.e. 4·5) kg/year; and MEITW + A, 72 (s.e. 1·2) MJ ME per kg beef. The regression of maternal lifetime productivity measures on mature cow weight was quadratic for YH, NC, TW and TW + A with optimal cow weight being 606, 600, 605 and 628 kg, respectively. AW and MEITW + A were positive linear functions of cow mature weight. Regressions of YH, NC, TW, TWIYH and TW + A on K were negative linear functions. AW and MEITW + A were not significantly related to K.

An experiment was designed to compare saline, prostaglandin F2α tham salt and progestagen pessaries as agents for oestrous synchronization in mature cyclic ewes maintained under normal husbandry conditions. The effect of these agents on ewe fertility and lambing performance was also assessed.

One hundred and sixty Clun Forest ewes were allocated to one of four equal-sized treatment groups and received either two injections of saline given 9 days apart (group A), two injections of 10 mg (group C) or 20 mg (group D) postaglandin F2α tham salt given 9 days apart, or progestagen pessaries left in situ for 12 days (group B). Oestrous response, fertility and lambing performance were monitored thereafter. Oestrus occurred within 3 days of the end of treatment in 0·28, 0·98, 0·58 and 0·83 of ewes in groups A to D respectively, with return rates after a single mating of 0·15, 0·13, 0·25 and 0·33 respectively. There was no difference between treatments in lambing performance. These results indicate that two injections of either 10 or 20 mg prostaglandin F2α given 9 days apart is a less effective means of synchronizing oestrus in sheep than progestagen pessaries.

Twenty-four British Friesian dairy cows in early lactation were used in a change-over design experiment with three periods, each of 4 weeks duration. The aim of the experiment was to assess the effects of both the type of concentrate and the level of concentrate supplementation on the utilization of grass silage for milk production. Four treatments consisted of offering 10 kg/day of either a barley (10B) or a sugar beet pulp-based concentrate (10S), each concentrate being offered at two crude protein concentrations of 175 (low) and 245 (high) g/kg dry matter. In a further two treatments the barley-based concentrates containing the low and high protein concentrations were offered at 7 kg/day (7B). All concentrates were offered in addition to the cows having ad libitum access to grass silage containing a dry-matter concentration of 213 g/kg and a digestible organic matter concentration of 668 g/kg dry matter.

Silage dry-matter intakes (kg/day) for cows given the low- and high-protein concentrates respectively were: 9·06 and 9·28 for the 7B treatments; 8·21 and 8·33 for the 10B treatments; and 8·04 and 7·97 for the 10S treatments (pooled s.e. 0·11). Fat-corrected milk yields for cows given the low- and high-protein concentrates respectively were: 24·0 and 24·1 for the 7B treatments; 25·9 and 27·0 for the 10B treatments; and 25·7 and 26·2 for the 10S treatments (pooled s.e. 0·57).

The higher level of concentrate feeding significantly increased milk yield (P < 0·001) whereas neither energy source nor protein concentration in the concentrates had a significant effect on milk yield (P > 0·05). There was a trend towards a greater response to increased protein concentration at the higher level of feeding.

In two experiments over 2 years, 181 Scottish Blackface ewes were differentially group-fed indoors to achieve moderately-good (score 2·5), moderate (score 2) or poor (score 1·5) body condition. Over 5 weeks prior to mating, ewes in moderately-good condition were either maintained or brought down to moderate condition by restricted feeding and ewes in moderate and poor condition were raised, respectively, to moderately-good and moderate condition by a high level of feeding. After mating, ewes were maintained in condition until slaughtered for a count of corpora lutea relating to first service. Ovulation rate was positively and significantly related to the level of pre-mating food intake at the moderate level of condition but not significantly so at the moderately-good level. It is postulated that ewes of this breed are more sensitive to the level of pre-mating food intake when in moderate condition at mating than they are when condition has risen to a moderately-good level.

A study was made of the behaviour of young calves at two Scottish auction markets, Lanark and Stirling, and an experiment was conducted to assess the effect of an auction market on the behaviour of calves less than 1 week old.

Several features of the marketing procedure were identified as causing the calves distress, mainly because the calves were unable to lie down and rest. Crowding of calves in the pens, movement to different pens, and penning of very young calves with older calves were the three main reasons why calves could not rest. The older calves (approx. > 10 weeks) were more active, running and jumping around the pens and disturbing the very young animals which stood up in response to being trodden on.

Crowding was severe in some pens although there was no clear evidence to show that small groups of calves (6 to 10 calves) in small pens rested more than calves in large groups (20 to 50 calves) in larger pens.

Calves showed their distress initially by calling loudly, looking wildly around their new environment and sometimes by running around the pen and calling. As time passed behavioural signs of distress were less prominent and calves assumed a ‘depressed’ posture with their heads low, ears held back, tails clamped down and with their weight distributed more on their hindlegs than on their forelegs.

Calves subjected to an experimental market showed similar signs of distress to those calves in the real markets, whereas control calves rested for more than 0·74 of the same time. Experimental calves which were subjected to a journey of 2.5 h were less easily disturbed from the lying posture at the experimental market than calves which had undergone a journey of 15 min only.

A contemporary comparison of crossbred ewes from five crossing sire breeds was made on a research farm from 1976 to 1981. The breeds involved were the traditional Border Leicester, three imported breeds — the East Friesian, the Oldenburg and the Texel, and a new prolific composite breed — the Cambridge. Rams from these breeds were group mated (2 to 3 rams per breed per year) to Scottish Blackface ewes on an upland farm in Scotland. Crossbred ewes derived from these matings were compared over three lamb crops on a lowland farm in England. The ewes were run together with the same husbandry conditions for all types. Results were available on some 120 to 150 ewes (300 to 450 lambings) per crossbred type. The Oldenburg and Texel crossbred ewes were appreciably poorer in most aspects of lowland lamb production. The Cambridge crosses were prolific but had high lamb mortality and lower litter weights at weaning than the traditional Border Leicester crosses. The East Friesian crosses were appreciably superior in several production traits. These results were combined with those from three other trials, involving crosses from the Bluefaced Leicester and Animal Breeding Research Organisation Damline to provide a ranking for UK crossing sire breeds.

An experiment was conducted to study the possibility of using marker concentration in faeces to estimate rumen outflow of Cr-treated protein supplements and the liquid phase (PEG). There were no significant differences in the outflow of each marker from the rumen when determined directly from rumen or indirectly from faeces, suggesting that faeces could be used to measure the outflow from the rumen without the need for surgical preparation of the animals. The outflow rate of the liquid phase was considerably faster than Cr-treated protein supplements.

Data were collected from 600 newborn lambs, offspring of 354 Western crossbred ewes and 26 rams, to determine heritability estimates as well as phenotypic and genetic correlations between wool follicle variables using histological techniques. Breed of sire and sire within breed were significant sources of variation in total and secondary wool follicle populations and secondary:primary (S:P) ratio. Heritability estimates calculated by regression of offspring on dam were slightly higher than by paternal half-sib correlation or regression of offspring on sire. Expressed as an average of the three methods of calculation, the heritability estimate for S:P ratio was highest (0·69), followed by estimates for secondary, total and primary wool follicles (0·52, 0·46 and 0·36, respectively). These estimates are similar to the heritabilities of fleece weight, staple length and fibre diameter. Selection for increased density, provided an accurate measure is used, is suggested as an effective means for increasing fleece weight within grade.

The growth of Southdown and Clun lambs was studied over the period birth to 415 days of age.

At birth, 50, 100, 150 and 200 days of age five lambs of each breed, and at 415 days three lambs of each breed, were slaughtered and their body composition determined by dissection.

The relative growth of lean, bone and total body fat was not influenced by breed. At each age both Cluns and Southdowns had similar proportions of total body fat, and were considered to be at the same stage of maturity.

There was a breed difference in fat partitioning, with the Clun depositing proportionately more of its total body fat intra-abdominally, compared with the Southdown. However, there was no significant effect of breed on the growth of individual fat depots relative to total fat. From earliest to latest the order of maturity was pericardial, intermuscular, perirenal-retroperitoneal, mesenteric, subcutaneous and lastly, omental fat.

Maturing patterns of carcass muscle, fat and bone and of body organs were established relative to live weight, using data from 20 Dorset Horn rams and 20 Dorset Horn wethers. The sheep were fed a pelleted ration from soon after weaning and individual sheep of both groups slaughtered at 6-kg increments in live weight from 18 kg to maturity at approx. 100 and 96 kg for the rams and wethers, respectively. This small difference in mature weight was mostly due to the weight of the testes and the increased weight of the head in mature rams.

As proportions of live weight, the mature rams had more carcass muscle and bone and less carcass fat than the mature wethers. In the mature animals the body organs in general comprised similar proportions of live weight in the two groups. However the head, hide and blood were proportionately heavier in the mature rams. The liver and alimentary tract were heavier in the mature wethers.

The maturing patterns for the three carcass tissues were not different for the two groups. However, many of the body organs matured on different patterns in the rams and wethers.

As the mature live weights and the maturing patterns for carcass tissues and some body organs were not different for the two groups, comparisons of the proportions of these tissues in rams and wethers would yield similar conclusions on an equal weight basis, as on the basis of the same proportion of maturity. However, comparisons of the proportions comprised by some body organs need to take account of different maturing patterns, as comparisons at different stages of maturity will each give different answers.

The performance of predominantly Suffolk-sired lambs from Border Leicester (BL), Bluefaced Leicester (BFL) and ABRO Damline (DL) crossbred ewes was compared on 18 commercial and college farms throughout England and Wales. The comparison took place over the 5-year period 1977 to 1981 and was the second stage in a comparative study on the productivity of the crossbred ewes. A total of 1277 crossbred ewes were involved with data on up to 3 years lambings per ewe, giving a total of 3522 mating records and 4864 lamb records.

The BFL lambs were heaviest and the DL lambs were lightest. The DL lambs had the lowest survival rates, and the BFL lambs the highest. The BFL lambs were slaughtered earlier (12 days) and at heavier weights (1·4 kg) than the DL and BL lambs, and had slightly heavier carcasses. The DL and BFL carcasses had better MLC carcass classifications than the BL, resulting in an advantage of 4 p/kg of carcass.

In productivity per ewe, the BFL litters had the highest slaughter and carcass weights and the highest income per litter, with the DL litters intermediate. An attempt was made to express productivity per unit of sheep weight maintained, taking account of ewe weight, litter size and the lamb slaughter date. On this index, the DL were marginally superior to the BFL, and both were superior to the BL.

Six weaned lambs were allocated to each of eight restricted feeding treatments with 1·00, 0·85, 0·71, 0·57, 0·43, 0·29, 0·15 or 0 of the diet as perennial ryegrass and the remainder as white clover, and to one ad libitum treatment with perennial ryegrass offered alone. A further six lambs were offered white clover ad libitum starting on day 15. Lambs on the restricted treatments received the same daily allowance of dry matter relative to live weight, adjusted at weekly intervals to allow the greatest possible intake without any rejection of herbage. Fresh cut herbage was offered daily and measurements were made over 69 days. Twelve additional lambs were slaughtered at the beginning of the experiment, and all lambs on restricted treatments were slaughtered at the end.

Increasing the proportion of clover in the diet increased the intake of nitrogen, empty-body-weight gain, carcass weight gain and nitrogen retention. When herbage was offered ad libitum, lambs ate significantly more clover than ryegrass and gained weight faster.

The weight of gut contents decreased as the proportion of clover in the diet increased. The digestibility of the organic matter, energy and nitrogen of the mixed diets simply reflected the digestibilities of the two herbages and their proportions in the mixture.

Maturity patterns have been established for 93 individual carcass muscles and nine standard muscle groups using dissection data from 20 Dorset Horn rams and 20 Dorset Horn wethers. A very high proportion, 81/93, of the individual muscles and all the muscle groups had maturity patterns which were not different for the rams and wethers.

Maturity patterns of some muscle groups varied from those previously demonstrated in Merino rams, in that the abdominal wall group was later maturing and the neck to forelimb and neck and thorax groups were earlier maturing in the Dorset Horns.

Comparison of the distribution of muscle weight of the Dorset Horn rams and wethers at the mean total muscle weight resulted in different conclusions to comparison at the mean proportion of maturity. It is concluded that comparisons of muscle weight distribution of entire and castrated male sheep, in which mature muscle weight varies, will be most meaningful if carried out at the same proportion of maturity, since comparisons at the same weight of total muscle will embrace components of difference due to stage of maturity.

In two experiments, ewes carrying two, three or four foetuses were offered restricted amounts of concentrates in the range 0 to 1050 g fresh weight per day and hay ad libitum from day 105 of pregnancy until lambing. The replacement rates of concentrates for forage were similar for both Teeswater × Dalesbred and Finnish Landrace × Dorset Horn ewes in experiment 1 (mean −0·63) when the ewes were offered hay which had an organic matter digestibility (OMD) in vitro of 0·56. There was no significant effect of number of foetuses carried on hay intake. As pregnancy progressed, hay intake increased slightly when hay alone was given and decreased at the higher levels of concentrates.

In experiment 2, hay intake by Finnish Landrace × Dorset Horn ewes was significantly higher when hay of higher digestibility was offered (0·52, 0·69 and 0·84 OMD) and decreased when higher levels of concentrates were given. Ewes carrying two foetuses ate more than ewes with three or four foetuses particularly when hay was offered as the sole food. Generally, hay intake decreased as pregnancy progressed and this was more evident when concentrates were offered.

A predictive equation is given to enable hay intake to be derived from hay digestibility, concentrate level, ewe live weight, number of foetuses carried and week of pregnancy.

One hundred and sixty-four Scottish Blackface ewes from two different farm sources were brought into a uniform moderately-poor level of body condition by early November. Five groups of approximately 33 ewes were then fed different amounts of pelleted dried grass and hay on pasture to achieve either high (H) or live-weight maintenance (M) levels of intake for different durations and at different times in the 36 days prior to mating at a synchronized oestrus. One group of ewes was fed the M level throughout, two groups were fed the H level for 18 days either preceded or followed by 18 days of the M level and two groups were fed the H level for 27 days either preceded or followed by 9 days of the M level. After mating, all ewes were fed the M level until slaughtered on return to service or at 28 (± 8) days after mating for counts of corpora lutea and viable embryos relating to first mating.

The gain in body condition and live weight after 18 days of H feeding was about half that achieved after 27 days. Time of H feeding had no differential effect on gain in condition or live weight. H feeding increased ovulation rate only if fed immediately prior to mating. When a period of M feeding preceded mating, most of the advantage was lost, particularly with 18 days of M feeding after 18 days of H feeding. Embryo mortality measured as ova loss was not significantly affected by either the duration or time of H feeding, although there was a trend for loss to decrease with increasing duration. Potential lambing rate to first mating was therefore significantly increased by H feeding for 27 days even when followed by 9 days of M feeding prior to mating but was not significantly increased by H feeding for only 18 days even when fed immediately prior to mating.

Differences in response were obtained from the ewes from the two sources. H feeding only produced a significant improvement in reproductive performance when potential was high and this was partly related to greater size. In populations with low potential, the provision of H feeding in the pre-mating period is therefore of doubtful economic advantage.

In a 2 × 2 factorial experiment, the effect of implants of the growth promoter Zeranol, with and without supplementary food, on the growth rate, blood metabolite and hormone profiles of lambs finished at pasture was examined. For lambs fed no supplement, Zeranol implants increased growth rates from 166 to 185 g/day (s.e. of difference = 11·4) whereas for animals fed supplement the response to Zeranol was much greater, the growth rates being 167 and 234 g/day (s.e. of difference = 12·8). Supplement given to lambs not treated with Zeranol replaced a proportion of the herbage intake while, in lambs given supplement and treated with Zeranol, herbage intake was greatly increased (P < 0·001). Plasma glucose and urea concentrations were not affected by treatment but non-esterified fatty acids (NEFA) were depressed and albumin levels increased by Zeranol implants, while supplementary food caused reductions in plasma NEFA and urea concentrations. It is suggested that Zeranol treatment and supplementary food acted synergistically through changes in insulin and growth hormone concentrations to induce a much larger increase in growth rate in the treated animals given supplementary food than in those given either Zeranol or supplement alone. The response to Zeranol may also have been altered by differences in thyroid hormone status associated with supplementary food.

The rate of incisor, pre-molar and molar tooth loss was studied in two groups of Masham ewes, one from 8·75 to 12·25 years of age, and the other from 7·25 to 9·25 years of age. Incisors were lost at the rate of 0·93 per year in group 1 and pre-molars from the lower jaw at the rate of 1·04 per year. The rate of loss of molars from the lower jaw and pre-molars from the upper jaw was much slower, whilst there was virtually no loss of molars from the upper jaw.

Mean litter size declined gradually from age 7 in group 1, but there was no decline up to age 9 years in group 2. Lambing percentage declined gradually from age 6 years, with a marked drop after age 10 years caused by an increase in barrenness and lamb mortality. Selling percentage also began to decline from age 6 years but dropped sharply after age 9 years following an increase in the number of lambs having to be reared by hand. Ewe live weight, lamb birth weight and lamb growth to 4 weeks of age showed no decline up to 12 years of age.

The effect of prolonged intake of saline well waters on the productive performance of 56 mature ewes and their lambs of the Magra and Marwari breed of the Rajasthan desert was studied for a period of 44 months. The sheep were maintained at pasture and given drinking water containing 0·3, 2·0 and 3·5 g/1 of total soluble salts. Body-weight changes during pregnancy and lactation, milk yields, greasy-fleece yields of the ewes, lamb birth weights and subsequent body-weight gains, up to weaning and post weaning, and greasy-fleece yield and pre-weaning and post-weaning survival rates of the lambs remained unaffected by the salinity levels in the waters tested.