Factors affecting survival to first and second calving and successful completion of a > 168-day first lactation were assessed in 3075 purebred and crossbred dairy heifer calves. Growth, disease, frequency, reproduction, calving, udder and lactation traits were examined in females of a breeding project conducted jointly at five research stations (herds) of Agriculture Canada. Losses included mortalities and non-discretionary culling. About 0·23 of potential heifers were culled or died before first calving, and 0·25 of those calving once did not calve a second time. Results from retrospective selection index and stepwise linear logistic analyses showed that predictability of culling prior to 308 days post partum was poor. With few exceptions, survival rates from birth to 82 weeks varied among herds (P < 0·001) and among lines (P < 0·05). Heterosis for the probability of completing a lactation and of survival to second calving was significant (P < 0·05) and positive (0·05 to 0·09). Heavier heifers were more likely to survive to first calving. Sire's estimated breeding values (SEBV) for milk yield and fat, protein and lactose concentration were not important in predicting survival to first calving. SEBV lactose was negatively associated with survival after first calving as predicted from data available at most preceding stages of life. An age greater than 82 weeks at last insemination was associated with a lower probability of survival to first and second calving (P < 0·001). Cows which conceived for a second gestation and subsequently aborted had a lower probability of survival to second calving than cows which did not abort (0·57 v. 0·76, P < 0·01). The only continuous traits with large effects on survival or the probability of completing a first lactation were days to last insemination (a measure of fertility) and milk yield. It was concluded that (1) there is considerable scope for improved management to increase survival in early life by prevention of calfhood diseases; (2) losses in early life do not bias sire evaluation on first lactation records; (3) improved reproductive success would greatly enhance overall survival rates; and (4) crossbreeding could have a large impact on overall herd profitability through increased survival.

Following a 3-week covariance period, 30 group-housed dairy cows were individually given one of three diets from week 4 to week 13 of lactation to determine any possible advantage in milk yield and production of feeding levels of undegradable protein (+UDP) or rumen-degradable protein (+RDP) above the minimum levels (control) proposed by the Agricultural Research Council (ARC, 1984). The three concentrates given were formulated to be of equivalent metabolizable energy (ME, 13·5 MJ/kg dry matter (DM)) concentration and each consisted of rolled barley plus a protein supplement: control (crude protein (CP), 129 g/kg DM) 0·35 kg DM fish meal per day; +UDP (CP, 167 g7kg DM) 1·0 kg DM fish meal per day; and +RDP (CP, 167 g/kg DM) 1+5 kg DM soya per day. For each group the total ‘concentrate’ allowance per animal per day was 11·6 kg fresh weight and was given in three equal feeds. Grass silage (CP 122 g/kg DM, ME 106 MJ/kg DM) was given ad libitum. For the control, +UDP and +RDP treatments, respectively, mean grass silage intakes were 8·29, 8·62 and 8·65 kg/day and mean milk yields were 26·6, 26·3 and 26·1 kg/day. These were not significantly different (P > 0·05). Milk fat concentration was lower (P < 0·05) for the +UDP treatment (36·4 g/kg) in comparison with the control (38·6 g/kg) or the +RDP treatment (39·7 g/kg) but no other milk constituent was significantly influenced by treatment. There was a trend for a greater live-weight gain with treatment +UDP (0·81 kg/day) compared with the other two treatments (control 0·50, +RDP 0·51 kg/day) but there were no differences in condition-score change between treatments. In this trial there was no advantage to feeding formulated levels of UDP or RDP above those proposed by ARC (1984).

Thirty-two Friesian cows in early lactation were given one of tour completely mixed diets based on equal proportions of barley straw and concentrate. Two varieties of barley straws had been identified as varying in degradation characteristics (Corgi and Gerbel) and the straws were either given untreated or treated with anhydrous ammonia. The ad libitum intake for 10 weeks closely reflected degradation characteristics. For Corgi, treated and untreated and Gerbel, treated and untreated the 48·h degradabilities were 71·9, 66·8, 61·9 and 52·2 (g/100 g) respectively. The voluntary intakes of dry matter were 17·1, 14·8, 15·0 and 13·1 (s.e. 0·51) kg/day and average yields of fat-corrected milk for 10 weeks were 26·7, 21·5, 22·6 and 22·4 (s.e. 1·0) kg/day respectively.

It was calculated that the differences between actual digestibility and potential degradability were greatest for ammonia-treated straws. Also it was observed that the degradability of faecal dry matter was greater from animals given ammonia-treated straws.

Five different straws consisting of two varieties of winter barley, two varieties of spring barley and one variety of winter wheat were chosen due to differences in degradation characteristics determined by using nylon bags incubated in the rumen of cattle and describing the straw using the equation: p = a + b (1 – e–ct). To increase variation in degradability, batches of the same straws were also treated with anhydrous ammonia in a sealed oven.

The straws were subsequently offered ad libitum to groups of steers given a daily supplement of 1·5 kg concentrate and untreated straws were supplemented with urea. The dry-matter intake (DMI) of the straws varied from 3·4 to 5·7 kg/day, the digestible DMI from 1·4 to 3·5 kg/day and growth rate from 106 to 608 g/day.

By using multiple regression of a, b, c from the exponential equations characterizing degradability of the straw, the correlation coefficients with DMI, digestible DMI and growth rate were 0·88, 0·96 and 0·95 respectively.

In the present study, a commercially available anabolic implant containing trenbolone acetate and oestradiol-17p was investigated in intact and castrated bulls. Measurements of growth rate, serum hormones and metabolites in both phenotypes, and testicular development and function in bulls, were obtained. The experimental objectives were realized in a 2 × 2 factorially designed experiment utilizing eight Angus-sired crossbred bulls and eight similar steers castrated at 7 months of age. Half of each group were implanted with 140 mg trenbolone acetate plus 28 mg oestradiol-17β. Body weights were monitored every 7 days and plasma samples were obtained at 28-day intervals from 9 to 15 months of age. In the implanted groups, mean concentrations of plasma trenbolone and oestradiol-17p were 380 ng/1 and 31 ng/1, respectively. Trenbolone concentrations were undetectable in both non-implanted groups, and plasma oestradiol-17β was less than half that in implanted animals. While plasma GH concentrations were stratified according to implant treatment, they did not differ among the groups. Cortisol levels showed phenotype × implant interaction; implanted steers and non-implanted bulls had lower concentrations than non-implanted steers and implanted bulls. The implant resulted in no significant changes in gross testicular measures in the bulls but did affect the testosterone response to a GnRH challenge and basal plasma concentrations of testosterone were reduced. Plasma urea concentrations were reduced by the implant, but sex phenotype had no effect. Over the 175-day trial, implantation did not significantly improve the growth rate of bulls, except during the first third of the experiment. In contrast, implantation improved the growth rate of steers over the entire experiment, although implanted steers still grew more slowly than either implanted or non-implanted bulls. It can be concluded that the endocrine status of the young bull is set for a fast growth rate, making improvements via an anabolic implant marginal, except in the immature animal.

Two experiments have been carried out to examine the effects on the intake and performance of finishing beef cattle of supplementing grass silages (perennial ryegrass) of medium and high digestibility (MD and HD respectively) with either extracted soya-bean meal or fish meal. In each experiment, the two silages were supplemented with (1) barley (107 g crude protein (CP) per kg dry matter (DM)), (2) a mixture of barley and soya-bean meal (187 g CP per kg DM) and (3) a mixture of barley and fish meal (182 g CP per kg DM) in a 2 × 3 factorial design. The MD silages were supplemented with 4·5 kg concentrates per head daily in each experiment and the HD silages with 2·75 and 2·5 kg per head daily in experiments 1 and 2 respectively. In experiments 1 and 2 respectively the diets were offered to 72 and 60 castrated male cattle of late maturing breed type which were initially 455 (s.e. 3·6) and 484 (s.e. 3·2) kg live weight; the MD silages contained 642 and 652 g digestible organic matter (DOM) per kg DM, 119 and 114 g CP per kg DM, 72 and 68 g NH3N per kg total N, and the HD silages contained 698 and 724 g DOM per kg DM, 158 and 148 g CP per kg DM, 58 and 51 g NH3N per kg DM. In experiment 1 for the MD silages supplemented with concentrates 1, 2 and 3 and the HD silages supplemented with concentrates 1, 2 and 3 respectively silage DM intakes were 5·47, 5·29, 5·24, 6·86, 6·77 and 6·76 (s.e. 0·129) kg/day; carcass gains 0·76, 0·74, 0·72, 0·75, 0·75 and 0·79 (s.e. 0·011) kg/day; subcutaneous fat depths 6·8, 7·8, 8·0, 9·2, 7·2 and 7·1 (s.e. 0·59) mm and areas of m. longissimus 21·5, 21·7, 23·2, 21·5, 22·4 and 21·9 (s.e. 0·78) mm2/kg carcass weight. Corresponding values for experiment 2 were 6·12, 6·05, 6·18, 7·65, 7·53 and 7·36 (s.e. 0·235) kg/day; 0·82, 0·88, 0·83, 0·85, 0·89 and 0·83 (s.e. 0·042) kg/day; 8·1, 7·8, 7·5, 9·1, 8·3 and 7·4 (s.e. 0·77) mm; 22·8, 21·9, 21·9, 21·0, 21·9 and 21·7 (s.e. 0·79) mm2/kg carcass weight. It is concluded that supplementation of MD or HD grass silages with soya-bean or fish meals did not significantly affect the intake, performance or carcass fatness of finishing beef cattle although the carcasses of animals offered HD silage supplemented with barley tended to be fatter than those from the other treatments.

Growth rates and chemical compositions were measured with ram lambs grazing pure stands of perennial ryegrass, timothy, cocksfoot and tall fescue. A group of lambs slaughtered at the start of the trial enabled estimates to be made of the live-weight gains over the summer and the composition of these gains. The composition of the grass was also measured in samples taken at weekly intervals and estimates were made of the nutrients consumed from the different grass plots.

The quantities of ash, Ca, P and Mg in the empty bodies of the lambs were within the range of published values from similar studies. They support the contention that grass-fed lambs tend to have larger contents of ash, Ca and P in their empty bodies than concentrate-fed lambs of similar weight. Perennial ryegrass provided a superior diet in that lambs eating this grass grew more quickly, with leaner tissues and higher levels of ash, Ca and P in their empty-body gains. Lambs consuming tall fescue grew most slowly but their mineral contents were as large as the ryegrass-fed lambs when data were adjusted for differences in empty-body weight. Lambs fed on timothy or cocksfoot were the most poorly mineralized in spite of consuming considerably more Ca, P and Mg than the lambs on ryegrass. The data suggest that the efficiencies of absorption of Ca and P in ryegrass may be high, at about 0·64 for Ca and 0·71 for P.

In three separate experiments a total of 144 Greyface ewes was offered direct-cut or wilted silage from week 4 to 5 of pregnancy until lambing with varying levels of concentrate during the last 6 weeks of pregnancy. Wilting resulted in a proportional increase in the intake of silage dry matter of 0·08 on average but, because digestibility of the wilted silages was lower, digestible energy intake of both silages was similar. Average change in ewe live weight from housing until after lambing was not affected by silage type and there was a small, non-significant increase in lamb birth weight on direct-cut silage. There was no evidence of any reduction in silage intake as total concentrate intake over the last 6 weeks of pregnancy increased to about 18 kg, and limited evidence of a reduction at higher levels with some indication of a greater reduction on direct-cut than on wilted silage. Compared with no-concentrate feeding the highest level increased ewe live weight by 252 g/kg concentrate and there was a non-significant effect on lamb birth weight of 13 g/kg concentrate.

Eighty crossbred sows, following a standard feeding regime in pregnancy, received daily either 2·0, 3·5. 5·0 or 6·5 kg diet containing 130 g digestible crude protein, 8·0 g lysine and 13·1 MJ digestible energy per kg over a 28-day lactation to produce variation in body fatness and live weight. Sows on the highest level of feeding gained 13 kg and lost some 3 mm backfat between farrowing and weaning; corresponding changes on the lowest level of feeding were –31 kg and –9 mm backfat. Live weight of the litter at weaning was positively related to sow daily food allowance in lactation, but the major benefit of increasing lactation food allowance was in reducing the rate of maternal body weight and fatty tissue loss. These effects were described by the regression equations: maternal live-weight change in lactation (kg/day) = —1·7+0·34 lactation food intake (kg/day); maternal backfat change in lactation (mm LJSP2) = —0·40+0·05 lactation food intake fkg/day). Sows ingesting less food in lactation catabolized proportionately more body tissue to maintain milk yield and piglet growth, although they achieved this imperfectly, having lighter litters at weaning. Calculation of an overall net balance, taking into account the need subsequently to replenish tissues catabolized in lactation and ensuring efficient rebreeding of the sow, favoured a lactation feeding strategy towards ad libitum.

The use of family selection indices has been proposed as a promising selection method for increasing prolificacy in pigs. Responses of up to 0-50 pigs per litter per generation are predicted from selection programmes using information from the dam and from relatives (full and half-sibs) of the dam and sire. In order to test this method in populations of finite size, the rates of selection response and the accumulation of inbreeding have been studied by simulation along 10 generations in a selected herd of 10 sires and 100 dams using five different family selection indices (Id, Ifd, Ihd, Ifs, Ihs). Two undesirable features were evident: (a) the standard deviations of indices were lower than those expected; and (b) the increase of inbreeding was up to three times that expected without selection. Both effects increased with the complexity of the family index reducing the rates of selection responses per generation, when a genetic model with dominance was assumed, to values close to 0·20 piglets, similar to those obtained with the basic index (Id). Some results of inbreeding effects on reproductive traits in three strains of an old closed herd of Iberian pigs are also presented. Multiple regression analysis of data from 4657 litters indicated a decrease in the number of live born ranging from 0·14 to 0·35 piglets per 10% increase in dam or litter inbreeding coefficient.

The interaction of sire with feeding regime (ad libitum and restricted) was assessed in the first stage of a selection experiment. There were 79 sires (59 Large White (Edinburgh) and 20 British Landrace (Wye)) with 1549 progeny (745 at Edinburgh and 804 at Wye) in the study. Progeny within each litter were allocated at random to each feeding regime. Pigs started test at 30 (± 3) kg and finished test at 85 (± 5) kg for ad libitum fed pigs or after 84 days on test for restricted fed pigs. All pigs were individually penned. At the end of test, food intake, weight off test and ultrasonic backfat depths were recorded. Variance components were estimated using restricted maximum likelihood and a weighted analysis took account of the different residual variances between feeding regimes, within each breed.

There were differences in some genetic parameters due to feeding regime within breeds. No evidence of a sire with feeding regime interaction for average daily gain or food conversion ratio was detected in Large White pigs (genetic correlations between ad libitum and restricted feeding were 1·21 (s.e. 0·17) and 0·89 (s.e. 0·19) respectively). Similar conclusions could not be made for the sample of British Landrace pigs due to the large standard errors of the genetic correlation estimates. For ultrasonic backfat depths, the negative estimates of sire variances under restricted feeding prevent calculation of the genetic correlations and conclusions to be made about the sire with feeding regime interaction.

The gene frequency of the halothane gene was estimated in nine British Landrace and Large White nucleus herds. Two hundred and sixty British Landrace and 186 Large White pigs purchased from these herd, to be used as foundation stock for a joint experiment on lean growth at the Physiology and Genetics Research Station, Edinburgh at Wye College, were test mated to homozygous halothane reactors (nn). One thousand six hundred and forty-six British Landrace and 1764 Large White offspring were given a 4-min halothane test at average ages of 76 and 50 days respectively. Maximum-likelihood estimates of the halothane gene frequency were 0·33 (s.e. 0·03) in British Landrace and 0·11 (s.e. 0·02) in Large White. Estimated proportions of reactors amongst heterozygotes (Nn) and halothane homozygotes (nn) were 0·00 and 0·70 in Large White, and 0·02 and 0·85 in British Landrace. There was significant heterogeneity between the herds for both breeds (P < 0·05). The proportion of halothane reactors in British Landrace herds has increased significantly (P < 0·05) from 0·13 in 1979 to 0·18 in 1982, and the proportion of Large White reactors has increased from zero to 0·01 in the same time period.

A study was made of the behavioural development of domestic piglets living in a spacious, ecologically and socially diverse environment. The effects of age and sex of piglet on the frequencies of 30 behaviour patterns over the period from birth to 14 weeks of age were examined through focal animal sampling of 35 piglets from six litters. It was found that the frequencies of lying and standing in contact with other pigs declined significantly with age while walking, wagging the tail, sniffing the ground and the biting of objects increased with age (P < 0·05). Trotting, scampering and circling with other piglets were most frequent between 2 and 6 weeks of age. The frequencies of shaking the head, ‘quacking’, rooting, shovelling, and chewing at, and shoving, other pigs also varied significantly with age. Females wagged their tails more frequently than males whereas males circled, shoved and mounted more frequently than females (P < 0·05). Results are discussed with reference to the behaviour of young pigs kept under intensive housing conditions.

Effects of daily food intake (FI) on daily gain (DG), food conversion ratio (FCR), ultrasonic backfat thickness (BF), proportion of lean parts (LP), proportion of fatty parts (FP), lean tissue growth rate (LTGR), fatty tissue growth rate (FTGR) and lean tissue food conversion (LTFC) were investigated in 687 barrows and 98 gilts, slaughtered at a mean live weight of 108 kg and fattened in seven batches. In the range of food intake from about 1·7 to 3·2 kg/day (22 to 42 MJ digestible energy) a continuous distribution of data was available.

Body composition was linearly related to FI. Most regressions of BF and all of LP and of FP on FI were linear, showing fatter animals at higher food intake. For FTGR, BF, LP and FP, parameter estimates based on linear regression were given. Although the response of DG and of LTGR on increasing FI was not always significantly different from linearity, the second degree polynomials indicated diminishing returns in all batches. FTGR had a high linear correlation with FI (0·85 to 0·95), indicating that in the present range of FI a rather fixed proportion of the food was used to deposit fatty tissue.

For DG and LTGR a non-linear model of the type a(FI -fo)b was fitted, where fo was interpreted as maintenance requirement. For FCR and LTFC the corresponding model was FI/(α(FI — fo)b). Both models were preferred over second degree polynomials because of better interpretation of parameters. FCR and LTFC showed minima at about 2·6 and 2·2 kg/day food intake, but especially for FCR the increase at increasing FI was low. Results were not consistent in demonstrating or refuting a plateau in LTGR, which in any event appears to lie near to or beyond ad libitum FI for most pigs.

Thirty-two entire male and 32 female pigs were used to investigate responses to eight concentrations of dietary protein, with constant amino acid composition ranging from 90 to 248 g/kg over different live-weight stages between 20 and 90 kg.

With increasing live weight there was a continuous decline in the concentrations of dietary protein required to support maximum growth and an increasing difference between the sexes in their response to dietary protein. Between 20 and 40 kg live weight sex had no significant effect on growth performance or on the dietary protein concentration for maximum growth (P > 0·05). Over all heavier live-weight stages entire males grew faster and more efficiently than females, and between 20 and 70, 20 and 80, 20 and 90 and between 50 and 90 kg live weight they responded to higher concentrations of dietary protein than females. During the latter stages of growth, the performance of females was also depressed on the two highest-protein diets. This was associated with a significant increase in carcass fat thickness at 90 kg.

Eighteen pregnant red deer hinds were slaughtered at known stages of gestation between 72 and 224 days (term = 233 days). The udder was removed and the gravid uterus was separated into foetal, placental, empty uterus, amniotic fluid and allantoic fluid components. Equations were fitted to the weights of each component to describe the effects of stage of gestation. Hind weight at mating had no significant effect. For the foetal weight (Y, kg) the data were closely fitted by a version of the Gompertz equation,

loge Y = 3·016 — 14·267exp (–0·01138t) – 0·086s

where t is time in days from conception and s is the sex of the foetus (male = −1, female = 1). The weights of the placenta and empty uterus were similarly fitted by versions of the Gompertz equation and mammary tissue by an exponential relationship. However, the weight of (logc) amniotic fluid was bestdescribed by a third degree polynomial, and that of (loge) allantoic fluid by a linear equation.

Using the equations and their first differentials, respectively, estimates were made of mean weights and daily rates of gain at different stages of gestation. These indicated altogether relatively slow growth and low weight of the red deer conceptus. Udder development occurred typically late in pregnancy.

The concentrations of dry matter (DM), crude protein (CP), fat and ash were determined for 18 singleton red deer foetuses of known gestational ages within the range 72 to 224 days (term = 233 days) and for their associated placentae and empty uteri. In addition, concentrations of Ca, P, Mg, Na and K were determined for the foetuses. The amniotic and allantoic fluids were analysed for DM, CP and ash content.

Concentrations of all measured components in the foetal fluids increased with foetal age (except for amniotic ash concentration which decreased) and linear regressions were fitted. Concentrations in the empty uterus remained constant. Given the equations previously fitted relating the weight of these tissues t o foetal age, the weights of their chemical constituents could then be calculated at various stages.

Concentrations of all measured components in the foetus increased with foetal age (except for foetal K which remained constant). In the placenta, concentrations of DM and CP tended to increase while those of fat and ash decreased. The actual weights of the chemical constituents were related to both foetal age and foetal weight by further regression analysis in the form of extended Gompertz equations.

Estimates are made of the daily rates of accretion of chemical components in the foetus and adnexa and these provide data against which to assess the additional nutrient demands of pregnancy in the red deer hind.

A technique is described for the collection of digestive contents with a glass T-shaped ileal cannula, in rabbits fed ad libitum. Repeated samples of ileal contents were easily obtained by gravity from conscious animals lying in a hammock for 1 h, twice a week, over a period of 2 months. Analysis of the ileal contents showed no diurnal variations in concentrations of crude protein, neutral-detergent fibre, ammonia, and total short-chain volatile fatty acids. The fresh weight output was maximal at 09.00 h and minimal at 03.00 h. The transit time of phenol sulphone phthalein between mouth and ileum was 75 (s.d. 14) min and did not vary according to the time of day when measured (08.00 to 12.00 h, 14.00 to 18.00 h, 20.00 to 24.00 h).