Ways of conducting a progeny test for growth of carcass characters are discussed with reference to statistical efficiency. An intensive system (375 kg slaughter weight) is compared with a semi-intensive system (475 kg slaughter weight) and the use of intermediate results as predictors of the final outcome is discussed.

The crossbred progeny of 32 Hereford bulls (1043 calves) were admitted to a Progeny Testing Centre at 2-month intervals at 2 weeks of age over a period of 2 years, and divided between the two feeding regimes. Growth and carcass characters were measured, including taste panel assessments.

The semi-intensive system was found to have a higher power of discrimination between progeny groups, and tended to rank the bulls i n a different order from the intensive system. Truncation of the test at various intervals introduced an element of risk into the formation of the final judgement and showed little advantage as a predictor.

Records of 178 593 monoparous births between 1964 and 1970 in Israeli-Friesian dairy cattle were analysed for information on environmental and genetic factors affecting calving difficulties and perinatal mortality. The incidence of difficult calvings (DC) and peri-natal calf mortality (PM) were 6·9 and 9·1% in heifer calvings, and 1·6 and 4·1% in cow calvings. Calving characters were not related t o heifer age nor cow parity, but there was a seasonal trend in heifer calvings, with both DC and PM being high in winter and low in summer calvings.

Heritability estimates for calf-genotype effects on PM were 0·042 in heifer calvings and 0·013 in cow calvings. Heritability estimates for dam-genotype effects on PM were 0·018 and 0·004 respectively. Heritability estimates for DC were similar t o those for PM. The genetic correlations between DC and PM in the same class of calvings ranged between 0·8 and 0·9, while the environmental correlations were considerably lower, about 0·3. The genetic correlations between the calf-genotype effects in heifer and cow calvings were about 0·5, indicating that different factors may affect heifer and cow calvings.

It is proposed that sires already proven for milk yield be tested for their calf effects in heifer calvings, using contemporary comparisons within herds and seasons. Results will be available when the sires are 6 to 6½ yr old. Sires causing fewest calving difficulties would be nominated for heifer matings, so that most heifer inseminations would be by sires proven for both yield and calving characters. Some long-term progress might be obtained if sires with a high incidence of difficulties in their heifer mates were not used to produce young sires.

Forty-two British Friesian castrated male calves of 1 to 3 weeks of age were offered ad libitum unwilted or wilted silage made from the same sward for 21 consecutive weeks. Both silages were supplemented with a cereal and protein concentrate at two restricted levels of intake or with dried grass cobs offered ad libitum. There was little difference i n the chemical composition ofthe two silages except for DM content. Dry-matter intake of wilted silage was slightly but not significantly greater than that of unwilted silage. Differences between silages in daily gain or final live weight were not significant.

An increase in the intake of the cereal and protein concentrate led to a significant decrease (P < 0·001) in silage DM intake and a significant increase (P < 0·001) in daily gain andfinallive weight. Calves offered dried grass as a supplement to silage ate similar quantities of silage DM to calves offered an equal amount of the cereal and protein supplement but gained significantly less (P < 0·001) live weight. When intakes were presented on a unit metabolic live-weight basis, calves ate significantly more (P < 0·001) silage when supplemented with dried grass than calves offered the cereal and protein supplement.

In two feeding experiments, an untreated silage which had received no additive was compared with silages which had received either formic acid (‘Add-F’) or a formalin and sulphuric acid mixture (‘Sylade’). The ‘Add-F’ was applied at the rate of 3·81/t and ‘Sylade’ at the rate of 3·1 1/t of fresh herbage harvested from a perennial ryegrass and white clover sward.

The silages were offered ad libitum to 30 British Friesian male calves (mean fasted live weight 97 kg) in Experiment 1 and to 27 steers (mean fasted live weight 320 kg) of mixed breed in Experiment 2. Concentrate was offered to the animals in Experiment 1 at the rate of 0·86 kg dry matter/head per day.

In each experiment the intakes of dry matter and digestible organic matter were higher from the additive-treated silages than from untreated silage.

In Experiment 1 the application of ‘Sylade’ increased significantly (P < 0·05) the mean daily unfasted live-weight gain (0·87 kg/day) over that for animals offered untreated silage (0·74 kg/day). In Experiment 2 the mean daily unfasted live-weight gains from ‘Sylade’-treated (0·70 kg/day) and ‘Add-F’-treated silage (0·78 kg/day) were significantly higher (P<0·01) than that from untreated silage (0·38 kg/day).

1. Water intake was measured in eight lactating cows. Subsequently n i an experiment of a 4 × 4 Latin square design, each cow received 100, 87, 73 and 60% of its voluntary intake for 6 days followed by an 8-day recovery period.

2. Measurements were made of the intake of feed, milk yield and quality, water, Na and K balances, metabolic profiles, and serum and urine osmolalities. The cows were weighed at the beginning and end ofthe experimental periods, and pulse, respiration and rumination rates and rectal temperatures were measured daily.

3. Milk yield decreased significantly with increasing water deprivation. A 40% reduction in water intake was associated with a 16% decrease in intake of dry matter and a concomitant 16% decrease in milk yield. The only significant change in milk composition was a small increase in lactose concentration with increasing water deprivation.

4. There was no significant reduction in urine output, but the output of water in faeces was reduced and there was evidence of a reduction i n total body water which approximated the reduction in body weight. 5. Concentrations of serum Na and urea-N and serum osmolality increased significantly with increasing water deprivation.

Growth coefficients were determined for muscle, bone and fat in the side and in the ham, for six muscles of the ham, and for the femur, using data obtained from the dissection of 66 carcasses of female pigs weighing from 25 to 65 kg live weight.

Irrespective of the independent variable taken for regression, the coefficients showed bone in the side to be earlier developing than muscle, which in turn was earlier than fat. There is good agreement between these coefficients and corresponding values reported for cattle, sheep and pigs.

There was little evidence that the ham as a whole or its muscle, bone and fat components grew disproportionately to the corresponding components of the whole side.

The growth coefficients of the six muscles of the ham agreed closely with those reported for cattle, sheep and pigs with the exception of that for the m. adductor, which was lower.

The combined weights of the m. biceps femoris and m. adductor were related almost as closely to the weight of muscle in the side as was the weight of total muscle in the ham. Of the six muscles taken individually the weight of the m. biceps femoris was most closely related to muscle in the side.

In a series of observations the association between within-litter variation in growth performance of piglets to 3 weeks of age and other parameters was examined in 28 litters. Growth rate was correlated significantly with birth weight and milk intake of the piglet. Birth order and location of the preferred teat did not influence significantly the milk intake or growth performance. In a second series of observations the individual behaviour of the piglets immediately after birth was examined in relation to the within-litter variation in growth performance to 3 weeks of age in three litters. The amount of time that each teat was sucked during the period of continuous suckle was positively correlated with the growth performance of the piglet which preferred the teat at day 21 of lactation.

The implications of genetic variation in maternal performance for the relative merits of common selection strategies have been investigated. If the accuracy of progeny testing is computed without taking maternal effects into account, the estimate is biased upward. This bias increases as the correlation between direct and maternal genetic effects decreases from positive to negative values. The relative efficiency of progeny and performance test selection is a function of the heritability of direct and maternal genetic effects and the correlation between them. In terms of genetic gain per unit time, progeny testing is almost always less efficient than performance testing. For sire line improvement progeny testing is relatively more useful but is still likely to be less efficient than performance test selection unless there is a negative correlation between direct and maternal genetic effects or the correlation between purebred and crossbred direct genetic effects is very low or negative.

Analysis of body weight at 6 and 14 weeks of age in Galway sheep has shown that maternal genetic effects are an important source of variation in this population.

Two groups of 4 Suffolk rams were each subjected to mating pressures of 90 ejaculates (High) and 45 ejaculates (Low) over a 3-day period during summer and autumn. Every sixth (High) or every third (Low) ejaculate was collected into an artificial vagina and assessed for volume, sperm density, total sperm per ejaculate, motility and percentage of live and abnormal sperm.

There was a general lowering of semen quantity and quality with successive ejaculations. Rate of change of the various measures was greater on the High than on the Low mating pressure. Volume and percentage of live sperm showed a greater decline, and percentage of abnormal sperm a greater increase, during the autumn than during the summer. Density showed a greater decline in summer than in autumn.

The significance of the changes in semen characteristics observed is considered in relation to requirements for high fertility after pro-gestagen treatment.

Four 2½-year-old Suffolk rams were each mated to groups of 24 Polled Dorset Horn ewes in which the oestrous cycles had been synchronized by the use of progestagen-impregnated vaginal sponges. Ram introduction occurred at either 24 or 48 hr after vaginal sponge withdrawal. Few ewes were in oestrus 24 hr after sponge withdrawal, but the majority were showing oestrus at the time of the 48-hr introduction. Mating behaviour and subsequent lambing performance of the ewes were recorded. All rams mated with the majority of their ewes. Rams introduced 48 hr after sponge withdrawal were found o t serve their ewes less frequently and over a more limited period, but they did succeed in mating with a greater proportion of their ewes during their first 30 services. There were no statistically significant differences in overall lambing rate between treatments, but the ratio of ewes lambing to ewes served on the 48-hr treatment was 92·5% compared with 72·2% for the 24-hr treatment (P < 0·05).

From among 27 rams of haemoglobin type A the two rams with the highest plasma copper concentration and the two rams with the lowest were selected on the basis of a single determination. In the same way four rams were selected from among the 29 rams of haemoglobin type B. The average difference between the ‘high’ and the ‘low’ rams was 103 μg copper per 100 ml plasma. The rams were mated to 105 unselected females. Lambs born as a result of these matings were blood-sampled on eight occasions from 3 weeks to 29 weeks of age.

The plasma copper levels of the lambs sired by the ‘high’ copper rams were higher on average than those sired by ‘low’ copper rams. The two groups diverged from 12 weeks of age onward to a maximum difference, at 29 weeks, of 18 μg copper per 100 ml plasma. There was also an initial difference of 13 μg at 3 weeks but a much smaller one at 6 and 9 weeks.

There was no corresponding difference in plasma copper concentration between the offspring of haemoglobin A and haemoglobin B rams. The results are therefore consistent with the hypothesis that the association previously observed in the same flock between haemo-globin type and plasma copper level is unlikely to be due to an effect of the gene controlling haemoglobin type, but could be due effectively to a linked ‘copper gene’.

Correlations between maternal plasma copper concentration 3 weeks after parturition and lamb's plasma copper level showed a marked decline as the lambs grew older, starting from around 0·6 at 3 or 6 weeks old. This suggests a maternal ‘environmental’ influence on lamb's plasma copper in addition to any genetic effects.

The rectal temperature of 208 lambs of Scottish Blackface, Tasmanian Merino, Southdown, Cheviot, Soay and Finnish Landrace breeds was measured between 15 and 25 min after birth, and that of 94 lambs again 1 hr after birth. Relationships within breeds between rectal temperature and birth weight, weather (temperature and wind speed) and gestational age were examined.

Within the range of birth weights and weather encountered over a period of years Scottish Blackface, Cheviot and Soay breeds maintained homeothermy at birth. In contrast, the Merino and Finnish Landrace breeds, which had comparable birth weights to the Black-face and Soay respectively, showed significant reductions in body temperature sometimes exceeding 10°C in cold weather. The Southdowns also showed hypothermia. In the Merinos and Finns, 30 and 54% respectively of the variation in rectal temperature was accounted for by birth weight and weather.

Of those lambs with low rectal temperatures 20 min after birth, few showed any improvement after 1 hr. Merinos in cold weather showed the least tendency to recover.

Possible reasons for the different performance of the breeds and the implications for lamb survival are discussed.

A molassed sugar-beet product with added urea and dicalcium phosphate was evaluated as an energy and protein source for housed lactating ewes. Comparisons were made with a barley-vegetable protein and a barley-urea concentrate each formulated to supply approximately the same amount of crude protein. The overall performance of ewes and lambs given barley and vegetable protein was very significantly superior to that of ewes receiving the sugar-beet product. At 6 weeks after lambing the ewes given barley and vegetable protein had lost 57% (with singles) and 23% (with twins) less weight and their lambs had grown 28% (singles) and 48% (twins) more quickly than for ewes receiving the sugar-beet product. The intermediate performance of the ewes receiving barley and urea illustrated that the difference between the barley-vegetable protein concentrate and the sugar-beet product was both an energy and a protein effect.

An experiment was conducted to determine the effect of time of uptake of colostrum on blood gamma-globulin concentrations, lamb survival and subsequent growth rate. Seventy-six Greyface ewes and their lambs were housed throughout the experiment. After lambing, the lambs were either allowed to suck their dams immediately or restricted from sucking for 6 or 18 hr after birth. The gamma-globulin concentration in the lamb sera reached a peak 24 to 72 hr after the time of first suck and then gradually declined to 6 weeks. Restriction from sucking for the first 18 hr after birth did not reduce the amount of gamma-globulin absorbed compared with lambs allowed immediate access to colostrum. There was no difference between groups in lamb mortality which was low in all cases. With both single and twin lambs the best live-weight gain was achieved by lambs allowed to suck their dams from birth.

Forty British Friesian male calves were pair-fed creep feeds containing 67% of either cooked potato or cooked maize in the form of a dry coarse meal or finely ground in liquid suspension.

Although dry maize diets were more acceptable than dry potato diets, daily gains were unaffected by either diet composition or drymatter content.

Calves on liquid-fed diets produced faeces of significantly lower dry-matter content.

Six castrated male cattle of 350 kg live weight were used in an incomplete Latin square design to measure intake and digestibility of barley straw offered ad libitum alone and with 5 levels, 1·5 to 7·5 kg/day, of a barley and dried lucerne concentrate. Straw intake declined and total organic-matter intake increased linearly with increasing concentrate level. On average 1 kg additional organic matter as concentrate, increased total organic-matter intake by 0·68 kg. There was no evidence that the crude protein content of the whole diet affected straw consumption.

Semen samples from 19 bulls were added to solutions of NaCl having chloride concentrations of 10, 15, 17, 18, 19 and 20 g/1, and were examined continuously for motility until motility had ceased or 5 hr had elapsed. At chloride concentrations of 10 and 15 g/1 some motility was always present after 5 hr. At 19 and 20 g/1 sperm motility stopped abruptly. At 17 g/1 mean survival time was 2·55 hr. In four bulls which had chloride concentrations in semen of over 2·80 mg/ml, sperm survival time was significantly lower than the average for the other semen samples which had chloride contents between 1 -40 and 2·25 mg/ml. A larger study would be needed, however, to establish whether survival of bull sperm is related to the chloride content of the semen at the time of ejaculation.