Twenty-eight Holstein/Friesian dairy cows were divided into four groups of seven. From weeks 4 to 15 of lactation they were given a basal diet consisting of 8 kg hay, 2 kg sugar-beet feed and 2 kg grass nuts, together with a concentrate allowance of 8 kg/day. Concentrates for group A were based on cereals and soya (control). Concentrate B contained 60 g protected fat supplement per kg; concentrate C contained 100 g lactose per kg; concentrate D contained 60 g fat supplement and 100 g lactose per kg. Milk yields were 24·6, 27·7, 25·6 and 26·5 kg/day and milk protein concentrations were 32·3, 30·7, 32·7 and 31·9 g/kg for groups A, B, C and D respectively. The effect of fat supplementation on milk yield and protein concentration was significant (P < 0·05) but the effect of lactose was not significant. Milk fat concentration was not significantly affected by treatment. It is concluded that lactose can partially alleviate the depression in milk protein concentration often observed when cows are given protected fat.

Although there may be task-specific differences in performance between wild and domestic animals, there is no evidence for any generally reduced cognitive capacity in domestic animals. It is not possible to compare intelligence between species or breeds without recognizing the contribution of differences in attention and motivation, and domestic animals often perform better on learning tasks than wild animals because they are less fearful. Considerable flexibility and complexity in behaviour can arise from context-specific decisions that may not require learning. Examples include alarm calling and maternal behaviour in chickens. However, the majority of intelligent behaviour shown by farm animals is dominated by learned associations, sometimes in response to remarkably subtle cues. Seemingly straightforward learning abilities may result in surprising emergent properties. An understanding of these properties may enable us to investigate how farm animals interact socially, and whether they form concepts. Other abilities, such as imitation and the re-organization of spatial information, do not appear to depend on associative learning. The study offarm animal cognition tells us little about the issue of animal consciousness but, none the less, plays an important role in the animal welfare debate. The types of cognitive abilities animals have provide clues as to the types of situations in which (given the benefit of the doubt) they might suffer.

The response of performance tested purebred Simmental heifers to various superovulatory treatments with ovine FSH was examined in two experiments. The heifers were 12 months old at embryo recovery, had average live weights of 468·4 kg (experiment 1) and 493·2 kg (experiment 2), and were fat (body condition score approx.4·0 to 4·5 units) at embryo recovery. In experiment 1, the effect of administering a total of 9·0 or 10·8 mg ovine FSH (Ovagen) administered as eight equal doses twice daily over 4 days was evaluated. In experiment 2, a total of 9·0 mg ovine FSH was administered either in equal doses in a level pattern or in declining doses twice daily over 4 days.

The response to the low, compared with the high, dose of ovine FSH in experiment 1 was 8·8 v. 10·5 ovulations (corpora lutea); 7·7 v. 7·7 totalova plus embryos recovered; 6·0 v. 4·1 viable embryos; 4·4 v. 3·1 grade 1 embryos (P > 0·05); and 1·7 v. 4·1 non-fertile ova(F < 0·01). In experiment 2, the response to the same total dose of ovine FSH administered in a level compared to a declining pattern was 8·5 v. 10·7 ovulations; 5·6 v. 9·6 total ova plus embryos; 3·1 v. 5·6 viable embryos; 2·5 v. 3·8 grade 1 embryos; and 1·7 v. 2·2 non-fertile ova. It was concluded that, although the differences between the treatments in the yields of viable and grade 1 embryos were not significantly different, there are practical and economic advantages to using a low rather than a high level of gonadotropin and there are no marked disadvantages in these areas to administering ovine FSH in a declining rather than a level pattern of doses.

Crossbreeding parameters and variance components were estimated for lactation and reproductive traits of crosses between the Sahiwal, Brown Swiss and Ayrshire breeds in a dairy herd in sub-humid coastal Kenya. An individual animal model urns fitted to the data with a fixed effect for 20 distinct breed crosses. The estimates of breed cross means were then regressed on average breed content, expected average heterozygosity and recombination loss to determine the additive breed contributions, and the contributions of dominance and epistasis to heterosis. It was estimated that the Sahiwal contributed about 1345 kg (proportionally 0·33) less milk per lactation than the Brown Swiss. The Ayrshire was intermediate. The large amount of heterosis from the crosses of the Sahiwal (Bos indicusj and Bos taurus breeds more than compensated for the lower additive value of the Sahiwal when used in a three-breed rotational cross or synthetic. Heterosis amotig Bos taurus breeds was negligible. Estimates of the maternal heterosis and recombination loss (epistasis) were not significant, although the latter were consistently large and positive. It was concluded that the heterosis between the zebu and European breeds was mainly due to dominance effects. Estimates of heritability for milk yield traits were low (around 0·09 to 0·13) compared with other studies, although estimates of repeatability (around 0·29 to 0·33) were similar to results from the literature, indicating that the accuracy of estimated breeding values in this crossbred herd was reduced because of the non-additive genetic effects. The genetic improvement of crossbred herds is discussed.

Customized sire selection indices were developed for Australian dairy bulls in order to promote more objective use of estimated breeding values in commercial breeding programmes. It was assumed that the breeding goal for commercial dairy farmers is the profitability of a bull's progeny. Seven characteristics of the progeny were identified as having a major impact on profitability and were included in the breeding objective: milk, fat and protein yield, survival, body weight, milking speed and temperament. Traits in the selection indices used to predict profit were milk, fat and protein yield, survival, milking speed, temperament, size, overall type and fore teat placement. Size was included because of its correlation with body weight, and overall type and front teat placement because of their correlation with survival. To avoid double counting the benefits of milk production traits, temperament and milking speed, the survival trait in the objective was defined as survival independent of voluntary culling for these traits. Customization of the breeding objective was achieved by adjusting the economic weights for traits in the objective to take account of important characteristics of farmers' herds, the milk payment system under which they operate and make allowance for their own value judgements. An assessment of the impact of customization suggested that, even though there is a wide range in the economic weights that are applicable in different areas of Australia, there would be little loss of efficiency in using a single national index. However, customization is still believed to be desirable given that it is likely that a substantial proportion offarmers will be reluctant to use a national index, especially in those states which have quotas and focus on the liquid milk market. The algorithms described in the paper have been incorporated into a user-friendly microcomputer program called $electabull which is now commercially available to farmers.

Sixteen first lactation dairy cows were used in a 2 × 2 × 2 × 2 factorial design experiment. Two silages, an extensively fermented inoculant-treated silage or a restricted fermented, mixed aliphatic carboxylic acid-treated silage were offered with two concentrate types (starch- or fibre-based) and supplementary lactic acid (LA, 0·4 kg/day) or soya oil (SO, 0·41 kg/day). Concentrates containing 180 g crude protein per kg were offered at 6 kg/day. Silage dry-matter intake tended to be higher (P = 0·07) with restricted fermented silage compared with the inoculant silage. Milk fat or protein concentrations were not significantly affected (P > 0·05) by silage fermentation type. LA inclusion had no significant effect (P > 0·05) on animal performance. SO inclusion significantly increased (P < 0-05) milk yield (+ 0·8 kg/day), decreased milk fat concentration and yield (40·2, 32·9 g/kg and 779, 667 g/dayfor - and + SO respectively, P< 0·001) and decreased milk protein concentration (-0·81 g/kg, P < 0·01). A significant concentrate × soya-oil interaction (P<0·01) suggested a greater reduction in milk fat concentration with the SO, starch compared with the SO, fibre combination. Modified acid-detergent fibre (P < 0·01) and neutraldetergent fibre (P < 0·001) apparent digestibility coefficients were significantly lower with starch- compared with fibre-based concentrates. Results suggest that milk production responses to changes in concentrate composition were not influenced by the extent of restriction of the silage fermentation process.

Four silages were prepared from perennial ryegrass swards at each of first (primary growth), second (first regrowth) and third (second regrowth) harvests during the 1993 growing season. At each harvest the four silages included two unwilted (without and with inoculant at 2·4 l/t) and two wilted (without and with inoculant at 24 l/t). The four silages within a single harvest, were offered as the total diet at maintenance levels to 12 wether sheep for 3 weeks to determine nutrient apparent digestibilities. They were also given to 12 lactating dairy coivs together with a concentrate supplement, in a three-period change-over study with experimental periods of 8-weeks duration, to examine dry matter (DM) apparent digestibility and utilization of nitrogen (N) and energy in the diets.

Inoculation tended to improve silage fermentation with on average lower pH and ammonia-N/total-N across the three harvests, while wilting of grass prior to ensiling significantly increased silage pH fP < 0·001) and ammonia-N/total-N (P < 0·001). Neither inoculation nor wilting had any significant effect on mean nutrient apparent digestibilities, assessed through sheep, across the three harvests. However, at the second harvest inoculation significantly reduced apparent digestibilities of DM (P < 0·001) and N (P < 0·001). At this harvest, wilting also significantly decreased apparent digestibilities of DM (P<0·05) and N (P <0·01), but significantly increased apparent digestibilities of DM (P < 0·05), energy (P < 0·001) and N (F < 0·05) at the third harvest. When the silages were offered as mixed diets to dairy cattle, neither inoculation nor wilting had significant effects on digestibilities of DM, N and energy at any of the three harvests, except for wilting which significantly decreased DM apparent digestibilities (P < 0·05) at the second harvest. However, the mean apparent digestibilities of DM (P < 0·01), N (P < 0·05) and energy (P < 0·01) across the three harvests were significantly lower following wilting, and N apparent digestibility (P < 0·05) was significantly higher following inoculation. The calorimetric data indicated that inoculaton had no significant effects on either methane energy output or heat production. Wilting also had no significant effect on methane energy output, but significantly increased daily heat production (P<0·05) at the first harvest. The efficiencies of metabolizable energy utilization for lactation (k1) were similar between the four silages at each of the first and second harvests, with the average being 0·50. The results of the present study indicated that inoculation tended to improve silage fermentation and significantly increased mean N apparent digestibility of mixed diets across the three harvests, while wilting significantly reduced mean DM, N and energy apparent digestibilities of mixed diets. Neither inoculation nor wilting had significant effects on Rvalue.

The aim of the present study was to investigate the effect of feeding strategy on the performance of oral stereotypies, such as tongue-rolling and bar-biting, and other behaviours in lactating dairy cows. Thirty–seven cows of the Swedish Red and Wliite breed were randomly assigned into three treatments with different feeding strategies. Cows in treatment (AL) were given food ad libitum during the whole experimental period, which lasted from weeks 3 to 26 post partum. The second group (AL–R) was given food ad libitum during weeks 3 to 14 post partum, thereafter they were given food at a restricted level. The third group (R) was given food at a restricted level during the whole experiment period. All cows were offered a total mixed ration consisting of 650 g concentrate and 350 g forage per kg twice a day and their individual daily food intakes were registered. Behavioural recordings were made for 4 h on a fixed day every 2nd week, where each individual cow was observed every 2nd minute.

During the complete experimental period, 27 out of the 37 cows showed stereotypies; 13 cows in group R, 10 in group AL–R and four in the AL group. The proportions of cows showing stereotypies were not independent of feeding treatment within the respective periods (P < 0·01). The stereotypy levels, counted as the mean frequency of recordings per treatment period, increased significantly between period 1 (lactation weeks 3 to 14) and period 2 (weeks 17 to 26) in group AL–R (P < 0·01) and in group R(P < 0·01), but not in the AL group. In period 2 the R cows had significantly higher stereotypy levels than the cows in the AL–R group (P < 0·01). Group R decreased the time spent eating between the periods (P < 0·001), with the same tendency in group AL–R. The AL group had longer eating time in period 2 than the AL–R (P < 0–001) and the R (P < 0·001) cows. The AL cows had a higher frequency of rumination than the other treatments in period 2 (P < 0·01). Both the AL–R and the R cows increased their activity levels between the periods (P < 0·001 for both). There were also differences between treatments in period 2, where the AL cows were less active than the AL–R (P < 0·05) and the R cows (P < 0·01).

It is concluded that oral stereotypies in dairy cows are highly affected by feeding strategy, where restrictive feeding of a mixed food induces significant increases of stereotypies. The results of this investigation clearly indicate that restricted feeding of a diet with high levels of concentrate has a negative effect on the well being of lactating cows.

Forty primiparous Holstein dairy cows were monitored from calving through 100 days in milk to evaluate the effect of energy balance in the early post-partum period on subsequent fertility. The post-partum interval to first ovulation (R2 = 0·41; P < 0·005) was lengthened by greater negative energy balance, and reduced by greater body weight at parturition or decreased body-weight loss during the experimental period. Luteal activity (R2 = 0·58; P < 0·0001), measured by plasma progesterone area under curve, was increased in the first cycle post partum by a shorter interval to first ovulation, improved energy balance during the 1st week of lactation and by decreased body-weight loss. Pregnancy status following first artificial insemination was related positively to the number of ovulations before insemination, improved energy balance during the 1st month post partum, fewer days to first ovulation and greater body weight at calving. These data suggest that energy balance and body weight are important in determining the post-partum interval to first ovulation and the subsequent fertility of first lactation dairy cotes.

Four silages (unwilted with and without inoculant, and wilted with and without inoculant) were prepared from perennial ryegrass swards at each of three harvests over the growing season. The four silages from each of the first (primary growth), second (first regrowth) and third (second regrowth) harvests were offered ad libitum to 48 dairy cows during periods 2, 1 and 3 respectively, in a two (control and additive) × two (unwilted and wilted) × three (harvest (period)) change-over design experiment with 8-week experimental periods. The animals also received a concentrate supplement at 7·0, 6·1 and 5·2 kg dry matter (DM) per day in the first, second and third periods respectively. The supplement was based on barley, molasses and soya-bean meal.

There were significant interactions between inoculation and wilting across the three harvests on silage DM intake (F<0-01), milk yield (P<0·05), and outputs of fat (P<0·01) and protein (P<0·05). Inoculation had no significant effects on silage intake and milk production across the unwilted and wilted silages. However, within the unwilted silages, inoculation significantly increased silage DM intake by 0·46 kg/day (P < 0·05) and fat yield by 0·032 kg/day (P<0·05). In contrast, within the wilted silages inoculation significantly reduced fat yield by 0·030 kg/day (P < 0·05). Wilting of grass prior to ensiling significantly increased silage DM intake by 0·73 kg/day (P <0·001), milk yield by 0·42 kg/day (P<0·05), fat yield by 0·053 kg/day (P < 0·001) and protein yield by 0·047 kg/day (P < 0·001) across the inoculant-treated and untreated silages. The effects however were mainly derived from the untreated silages as within the inoculant-treated materials the differences in silage intake and milk yield were not significant between unwilted and wilted treatments. The results of the current experiment indicate that wilting with no additive significantly improved silage intake and milk production, but otherwise the improvement was reduced with wilting following inoculation. Inoculation significantly increased silage intake and fat yield when used with the unwilted grass, but it significantly reduced fat yield when used with the wilted grass.

To examine the effects of increasing the crude protein (CP) content of concentrates at either equal concentrate intake (increasing CP intake) or at reducing concentrate intake (equal CP intake), 44 multiparous Holstein-Friesian cows were allocated to one of five treatments for weeks 4 to 18 of lactation. The treatments were 6 kg dry matter (DM) per day of concentrates containing nominally 200, 300 or 400 g CP per kg DM or 9 or 3 kg DM per day of concentrates containing 200 or 600 g CP per kg DM respectively. In addition 23 first-calf cows (heifers) were offered 5 kg DM per day of concentrates containing 200, 300 or 400 g CP per kg DM. All the animals were offered first-cut perennial ryegrass silage ad libitum. Increasing the concentrate CP content at equal intake caused only small and non-significant increases in silage intake by both heifers and cows. It significantly increased yields of milk and milk protein for both groups but whereas the cows responded to both increments of CP, the heifers only responded to the first. The concentrations of total protein, true protein, casein and non-protein nitrogen (NPN) in milk were significantly increased but the concentration of whey protein remained unchanged. Increasing CP concentration while the concentrate ration was reduced enhanced silage intake but had no significant effect on yields of milk or milk solids. The concentrations of total protein, true protein (non-significant), casein and NPN all increased but whey protein was unchanged. Overall the concentrations of casein and NPN were linearly related to the dietary CP concentration. With both concentrate strategies the proportion of true protein in total milk protein decreased and the proportion of NPN increased with increasing dietary CP concentration but the changes, though highly significant, were relatively small. It is concluded that the strategy of reducing the concentrate ration while maintaining concentrate CP intake causes only small reductions in milk solids production but it is dependent for success on supplies of high-quality grass silage to substitute for the concentrates.

Sixteen varied grass silages metabolizable energy (ME): 9·76 to 11·99 MJ/kg ethanol-corrected toluene dry matter (TDM); crude protein (CP: 149 to 211 g/kg TDM; lactic acid: 3·5 to 134·7 g/kg TDM; butyric acid 0·4 to 46·7 g/kg TDM) were offered ad libitum to early-lactation dairy cows (12 per experiment) along with a fixed allocation of 7 kg/day of a standard concentrate. Four silages were offered in each of four incomplete change-over design experiments with three 21-day periods. This design meant that each cow was allocated to receive three of the four silages evaluated in that experiment. ME intake ranged from 108 to 262 MJ/day (mean 177 (s.d. 30·2)). Similar variation was obtained with milk yields (mean 26·5 (s.d. 4·36) kg/day), fat content (mean 37·7 (s.d. 5·60) g/kg) and protein content (mean 29·0 (s.d. 2·36) g/kg). Urinary purine derivative/creatinine ratio (PD/C), an index of microbial protein measured in spot samples (two per day) averaged 2·92 (s.d. 0·757) mol/mol. Allantoin made up an almost constant molar proportion of PD excretion (mean 0·876 (s.d. 0·0377)), with a small but significant (P < 0·001) decline of 0·0132 (s.d. 0·003) per unit increase in PD/C.

Maximal utilization of silage nitrogen occurred with silages having higher ME and lower CP concentrations. Urinary PD/C suggested that microbial protein yield varied in a way which would not be predicted in current schemes and that it was a major source of variation in milk protein yield under the conditions of the present experiment. Principal components regression confirmed independent effects of ME supply and MP supply (indexed by urinary PD/C) on milk protein yield. Further work should pursue the possibility of using the urinary PD/C technique to refine protein feeding at the farm level.

Stochastic simulation is used to compare different systems of mating to reduce rates of inbreeding in selection programmes with phenotypic or animal model best linear unbiased prediction (BLUP) evaluation. Compensatory mating (the mating between individuals from the largest selected families to individuals from the smallest) turns out to be proportionately about 0-30 more effective than minimum coancestry matings for situations with low rates of inbreeding, such as phenotypic selection or high population size, although the advantage is less apparent if common environmental effects are important. A modification of this system of mating is proposed which can be applied for overlapping generations, and this is shown to reduce rates of inbreeding proportionately by about 0-50 more than for discrete generations. Under high inbreeding, however, such as for BLUP selection and small population size, minimum coancestry matings, or even avoidance of sib matings are more effective. A procedure combining compensatory and minimum coancestry matings is also simulated and gives the largest reductions in the rate of inbreeding. The effects of these and other systems of mating on the rate of inbreeding are shown to occur through a reduction in the cumulative effect of selection and a deviation from Hardy-Weinberg proportions.

Keeping cattle inside on concrete slatted floors can be detrimental to their health and behaviour and is also costly. Therefore, 22 steers of the Swedish Red and White Dairy breed were used to investigate the effect of wintering outdoors on growing cattle. The steers had a mean weight of 310 kg at the onset of the study. During winter, 11 ‘indoor’ steers were housed in pens with concrete slatted floors and 11 ‘outdoor’ steers were kept in a field with access to a shelter and trees. From the end of April until slaughter in September, both groups grazed together. During winter, all steers were given clover silage ad libitum. They were weighed every month. The behaviour of the outdoor steers was recorded from November to the end of March. Outdoor temperature, wind speed and solar radiation were measured continuously. A heated model was used in order to calculate the climatic energy demand. The steers were never observed to shiver. They were not observed to use the shelter during daytime. The most frequently observed behaviour was ‘eating’, followed by ‘standing’. The lower the temperature, the more time the steers were observed lying down (P < 0·01). ‘Moving’ increased with increasing temperature (P < 0·05) as well as with increasing wind speed (P < 0·01). During the grazing period following the experiment, the former outdoor steers grew significantly (P < 0·05) better than the former indoor steers. However, there was no significant difference in overall growth rate from start to slaughter. This study suggests that the winter climate in this part of Sweden (latitude 60°N) did not affect in a negative way the welfare or the growth rate of steers kept outdoors.

This study examined whether a prolonged anoestrus had any long-term effect on subsequent fertility of cows and estimated the relationship between repletion and resumption of reproductive activity. Twelve low body-condition, non-milking, non-cycling (depletion state) F1 crossbred dairy cows (Friesian × Boron and Simmental × Boran) were stratified to two diets (H: natural grass hay offered ad libitum and mineral lick +3 kg concentrate, and H + P: H + 7 h/day natural pasture grazing) according to parity, body weight, body condition score and calving intervals. Daily dry-matter intake was similar between cows on the two diets, but total intake of nitrogen was proportionately about 0·10 greater for cows with access to pasture. The calculated metabolizable energy intake was more than twice the estimated maintenance requirement for cows on both diets. Live weights increased from depletion to ovulation, to oestrus and to conception, but were not significantly different between cows on both diets. Body condition score increased from depletion time to first oestrus and to repletion and was greater for H + P than for H cows at first oestrus and at conception. After an average of 45 days of repletion, cows were already ovulating with no significant differences between cows on either diet. Days to onset of oestrus were 83 and 44 days for diet H and H + P, respectively. Time to conception was similar between coivs on both diets. Conception occurred when cows on H and H + P diets had recovered proportionately 0·51 and 0·58 of their live-weight and 0·84 and 1·27 of their body condition loss, respectively. Interval to repletion weight was 178 and 139 days for cows on the H and H + P diet, respectively. Cows subjected to an exceptionally long depletion period were able to resume ovarian cyclic activity and to conceive in less than 3 months when given twice maintenance requirements. These results have important management implication for on-farm situations in the tropics where fluctuations of food availability and quality occur.

Four groups each of eight Limousin × Friesian bulls, average weight 344 kg, were offered individually ad libitum diets comprising: 920 g rolled barley, 50 g cane molasses, 15 g urea and 15 g minerals/vitamins mix per kg or 867·5 g rolled barley, 50 g cane molasses, 7·5 g urea, 60 g soya-bean meal and 15 g minerals/vitamins mix per kg, plus or minus yeast culture (YC, 1·5 kg/t) (all weights fresh weights), until slaughter (460 kg). Rumen samples were obtained by stomach tube. YC decreased rumen ammonia concentrations (116·7, 56·0, 74·3, 45·7 (s.e.d. 19·40) mg/l for barley/urea, barky/urea/YC, barley/soya-bean meal and barley/soya-bean meal/YC, respectively). This was associated with increases (P < 0·05) in both the total number of bacteria (2·3, 4·2, 3·5, 6·8 (s.e.d. 1·06) × 109 per ml, respectively) and the protein content of rumen fluid (7·7, 9·6, 8·7, 9·0 (s.e.d. 0·59) g/l, respectively). However, the flow of microbial protein from the rumen as estimated from the appearance ofpurine derivatives in the urine was unaffected (131, 130, 129, 147 (s.e.d. 12·6) g N per day, respectively). Thus although the animals responded to the undegradable rumen protein supplied by the soya-bean meal there was no significant response in live-weight gain with YC (1·28, 1·31, 1·42, 1·48 (s.e.d. 0·081) kg/day, respectively).

Eighteen F1 crossbred dairy cows (Friesian × Boran and Simmental × Boran) were allocated to one of three diet groups (H: natural pasture hay; H+3: natural pasture hay + 3 kg concentrate; and H+5: natural pasture hay + 5 kg concentrate) using a stratified random sampling procedure, with parity, milk production genotype, body weight and body condition score as blocking variables. Cows on each diet were then allocated to three draught forces (7, 11 and 15 kg draught force per 100 kg live weight) in a cross-over design to investigate relationships between work output, live-weight changes, dry-matter intake (DMI) and milk yield. Each cow worked for 36 days in early lactation (from calving to 90 days) and for a further 36 days in late lactation (from 250 to 340 days post partum). Work output was similar for cows on each of the three diets. Cows on the H diet consumed more hay than cows on H+3 and H−5 diets. Hay and total DMI, milk yield and milk fat were similar across draught forces and during working and resting days when the cows were not pregnant. Similar results were obtained when cows were from 82 to 172 days pregnant. Pregnancy did not affect the ability of cows to perform work at different intensities. During working days cows lost live weight both when pregnant and when non-pregnant. During rest days, non-pregnant cows on diets H, H+3 and H+5 compensated proportionately 0·12, 0·59 and 0·59, respectively, of the live weight lost during working days. Pregnant cows on diet H+3 and H+5 compensated proportionately 0·95 and 1·77 live weight, respectively. Lower total live-weight losses during the pregnant period could be attributed partly to relatively greater DMIs and lower milk production, but also to gestation. Prediction of live-weight change from total DMI above maintenance, milk yield and work output during periods of 6 working days was poor (R2 = 0·18). However, the same parameters explained adequately changes in live weight for supplemented and non-supplemented working cows (R2 = 0·38 and 0·79, respectively) during a period of 90 days.

The main objective of the present experiment was to investigate whether progesterone priming eliminates defective luteal function in seasonally anoestrous ewes induced to ovulate with pulsatile GnRH treatment by synchronizing the early stages of follicle development. This was achieved by suppressing and synchronizing the early stages of follicle development with bovine follicular fluid (bFF) and then investigating whether this was sufficient to eliminate defective luteal function following the induction of ovulation with GnRH. Ewes in group 1 (no. = 10) were injected s.c. with 2 ml bFF at 8-h intervals for a period of 3 days before the start of GnRH treatment. Animals in group 2 (no. = 10), ivhich served as positive controls, were given a single i.m. injection of 20 mg progesterone 3 days before the start of GnRH treatment, while those in group 3 (no. = 10), which served as negative controls, were injected with corn oil alone at this time. Ewes in all the three groups were induced to ovulate by administration of 2-hourly injections of GnRH (250 ng per injection) for 54 h. Frequent blood samples for LH, FSH, and oestradiol were collected around the time of both progesterone/bFF injections and GnRH treatment, as well as daily thereafter to monitor luteal function.

The bFF injections given to animals in group 1 resulted in a significant (P<0·001) suppression of FSH concentrations, followed by a rebound rise in concentrations after the cessation of treatment. GnRH treatment significantly (P < 0·05) increased both mean LH pulse amplitude and overall mean LH concentrations in all the three groups, while LH pulse frequency was increased only in non-bFF-treated ewes. Plasma oestradiol concentrations 24 h after the start of GnRH treatment were significantly (P < 0·05) higher in groups 2 and 3 compared with group 1. These differences in the patterns of oestradiol concentrations over time were associated with a significant (P <0·05) delay in the onset of the pre-ovulatory LH surge in ewes treated witli bFF (group 1). However, there was no difference in either the duration or the height of pre-ovulatory LH surge between the three treatment groups. Ewes in all three treatment groups ovulated in response to GnRH treatment. However, both laparoscopic examination and plasma progesterone concentrations revealed that the incidence of normal luteal function was significantly (P < 0·05) higher in group 2 (10/10) compared with groups 1 (2/10) and 3 (4/10), with no difference between groups 1 and 3. Overall, these results suggest that progesterone priming does not eliminate defective luteal function through synchronizing early stages offollicle development.

In order to study the effect of day length and temperature on performance, data from 495 growing, non-castrated bulls of the Swedish Red and White breed were analysed. Groups of 11 bulls were housed in either an insulated building in pens having slatted floors or in an uninsulated building with pens having both a deep straw bed and a concrete floor. The majority of the bulls (330) were given a concentrate diet ad libitum, while the remainder (165) were given grass silage ad libitum supplemented with concentrate. Energy intake, live-weight gain, housing temperature, day length and change in day length were calculated as 14-day period means for the two housing systems. Regression analyses showed that live-weight gain was associated with increasing day length in bulls on both feeding treatments. For bulls given concentrate ad libitum, metabolizable energy intake was associated with increasing day length. The intake of heavier animals was more influenced by day length than that of those which were lighter. The seasonal influence on daily energy intake in bulls given silage did not show the same pattern as for bulls given concentrate ad libitum. The intake was highest in June and lowest in December for the bulls given concentrate but for the bulls given silage it was highest in August, September and October and lowest in March and April. This was due to the varying quality of the grass silage over the year. No effect or very little effect of temperature or housing system on energy intake or on weight gain was found.

An animal model was used to estimate heritabilities of faecal egg count (FEC) and packed cell volume decline (PCVD) in lines of Merinos selected for divergent levels of resistance to Haemonchus contortus. The estimated heritability of FEC was 0·23 (s.e. 0·03) and of PCVD was 0·21 (s.e. 0·03). A cube root transformation was found to be effective in normalizing FEC data and reducing the range of within selection line-birth year variances from 118-fold to 10-fold. Transforming FEC data increased the heritability estimate to 0·29 (s.e. 0·03) and reduced selection bias due to heterogeneity of variance, but the further step of pre-adjusting the transformed data to a common variance had only a trivial effect. Heritability estimates for FEC in years with high means and variances were similar, as were estimates for transformed FEC. The estimated genetic correlations between measurements in years with high and low means and variabilities were 0·77 to 0·91.

PCVD and pre-adjusted transformed FEC had a phenotypic correlation of 0·48. Estimates for the genetic correlation ranged from 0·76 in the decreased resistance line to 1·00 in the increased resistance line and 0·87 with pooled data. Other effects on resistance included birth type and dam age, with twins and progeny of maiden dams being more resistant than their cohorts. Sex effects were unimportant for FEC but males had higher PCVD than females in most, but not all, years. Younger animals had higher FEC and PCVD than older animals. Maternal genetic effects were found to be unimportant, as were the effects of low levels of inbreeding.