Leptin has an important rôle in the control of appetite and energy expenditure. Several studies have reported the effects of leptin in ruminants. However, little is known about changes in circulating leptin concentrations in neonates of ruminant species, or the effects of weaning on plasma leptin concentrations. The main objectives of this experiment were: to examine plasma leptin concentrations in lambs, in the period from just after birth through to weaning; to examine the effect of weaning on plasma leptin concentrations, and to compare leptin concentrations measured using a ‘multi-species’ leptin radio-immunoassay (RIA) kit and a specific ovine RIA in lambs during the 6-month period after weaning. In a previous paper, we reported leptin concentrations using a commercial RIA during the post-weaning period. However, we were not able to measure plasma leptin concentrations from just after birth to weaning as they were apparently below the level of sensitivity of the assay. In the present study, five crossbred lambs were removed from their dams within 2 days after birth, and bottle-fed on milk replacer at a level sufficient to meet a 1•2 times maintenance metabolizable energy intake. Lambs were weaned 45 days after birth, and housed individually in pens. The lambs were offered timothy hay, rolled barley and soya-bean meal to meet a 200 g daily gain during the post-weaning period. During the pre-weaning period, blood samples were collected within 5 h of birth and thereafter at 09:00 h; every day from 2 to 6 days of age; at 2-day intervals from 6 to 14 days of age; and at 3-day intervals from 14 to 45 days of age. During the post-weaning period, blood samples were collected before and 3 and 6 h after the morning meal at the ages of 0•5, 1, 2, 3, 4, 5 and 6 months. Plasma leptin concentrations slightly increased (P < 0•05) just after birth and then remained constant until 45 days old (P > 0•05). Additionally, plasma leptin concentration was not significantly changed following weaning. During the post-weaning period, plasma leptin concentrations were compared using two RIA systems. The correlation between plasma leptin concentrations measured by the ‘multi-species’ leptin RIA kit and specific ovine RIA was poor (r = 0•41). These findings are consistent with other reports and suggest that the ‘multi-species’ leptin RIA kit is not suitable for estimating leptin plasma concentrations in ruminants.

The efficiency of vaginal electrical resistance (VER) measurements for oestrous detection was determined in four experiments. The mean VER during oestrus, metoestrus, dioestrus, pro-oestrus and anoestrus was 32·68±0·46, 41·26±1·17, 50·23±0·55, 43·52±0·54 and 55·86±0·57 ohms, respectively. There were significant (P < 0·01) differences between VERs at the different oestrous cycle stages, except those during pro-oestrus and metoestrus which were similar. Twelve cows were induced in oestrus using prostaglandin (PG) administration to study the changes in VER during the peri-oestrus period. VER values changed both on a within-day (P < 0·05) and day-today (P < 0·001) basis following PG administration. Of the eight cows that responded, all were classified as in oestrus by VER in comparison to five detected in oestrus by a teaser bull. There was a significant association between VER and probability of conception (P < 0·01). Conception rates were 84, 61 and 20% when animals were inseminated at VER ranges of 26 to 30, 31 to 35 and 36 to 40 ohms, respectively. In the final experiment VER was recorded each day at the time of milking in 22 cyclic cows for 60 days. Animals were inseminated when the VER declined below 35 ohms. Of these 22 cows five cows showed overt signs of oestrus and 11/22 (50%) became pregnant. Twenty-one days post AI, five cows returned to oestrus, based on low VER, whereas 17 continued to show a high VER but eight of these (8/17) were subsequently classified as non-cyclic. It is concluded that VER can effectively be used for oestrus detection and identification of the optimum time for insemination but has limited value for pregnancy diagnosis. Cows should be inseminated when a VER reading of less than 36 ohms is recorded.

In the double-muscled (DM) Belgian Blue beef (BBB) breed, caesarean section (CS) is being applied systematically as a management tool to prevent dystocia. As a matter of fact, CS is the only possible way of calving in the breed. High birth weight and a relatively small pelvic area are the main causes of dystocia and, in the DM-BBB breed, the reasons for the systematically applied CS. Selection for lower birth weight and larger pelvic sizes might reduce dystocia and routine CS. Few data on inner pelvic sizes of pedigree animals are available. Using external measurements to estimate the inner pelvic sizes might be an option to resolve this problem. In this study, animals of the DM-BBB breed were measured and weighed on farms and in abattoirs. External and internal pelvic sizes increased with live weight and age of the animals. Gender had a significant influence on inner pelvic traits. Increased muscular conformation was associated with decreased inner pelvic dimensions. Models with weight, gender, age, withers height and outer pelvic width (TcTc) can be used to estimate inner pelvic sizes (R2 between 0•35 and 0•77). The estimated inner pelvic sizes can then be used to genetically evaluate pelvic traits in the DM-BBB breed. Improving weight, withers height and TcTc width in combination with lowering muscular conformation may help to decrease the high rate of caesarean section in the DM-BBB.

The meat palatability, water-holding capacity, colour and shear force values of 32 Boer goat (BG) kids and 32 South African Mutton Merino (MM) lambs were investigated. Two pelleted diets (offered to 16 animals per species) with either a low (LE, 9·9 MJ/kg dry matter (DM)) or a high (HE, 12·1 MJ/kg DM) metabolizable energy level were given to the animals for either 28 or 56 days. Thereafter the animals were slaughtered, the meat cooked and presented to a trained sensory panel. Organoleptically, a difference between goat and lamb was noted. Each one had a specific species flavour, which was not influenced by energy level of the diet. BG meat was perceived to be stringier than that of the MM, but there was no significant difference in Warner-Bratzler shear force values. Tenderness declined with age in both species and there was also a tendency for goat meat to be less juicy than lamb. Chevon had a more pronounced after-taste than lamb. No objective difference could be distinguished between the colour of the cooked goat and lamb, but there was a tendency for fresh lamb to have a higher a*-value (redness) than goat. Although diet did not influence drip loss, drip loss increased with an increase in slaughter age. Only after 56 days did the m. semimembranosus of MM have a significantly higher drip loss than that of BG (LE: 4·84 v. 3·43%; HE: 4·72 v. 3·23%). In the m. semimembranosus of both species cooking loss increased with an increase in slaughter age. It can be concluded that goat meat compares favourably with lamb in terms of water-holding capacity, colour and shear force values. If goats are finished in the feedlot, it can be done on a LE diet, since diet does not influences any of the mentioned characteristics. This may render a direct economic advantage for BG feedlot finishing.

This experiment investigated the effect of feeding grass silage alone or supplemented with additional energy and/or protein on the partitioning of nutrients between fat and lean deposition in cattle grown from approximately 140 to 550 kg. The distribution of total body fat between the main fat depots was also assessed. Ninety-two Hereford ✕ Friesian steers (140±18•8 kg initial live weight) were allocated to one of four dietary treatments; grass silage offered either alone (diet S) or supplemented with fish meal (diet FM; 150 g/kg silage dry matter (DM) intake but offered at equal estimated metabolizable energy (ME) intake to silage) or forage-concentrate diets of silage and a barley/soya (80: 20) concentrate at ratios of 70: 30 or 30: 70 on a DM basis (diets 30C and 70C, respectively). Eight animals were slaughtered at the start of the trial to determine initial carcass composition. Of the remaining 21 animals per diet, three were slaughtered at each of seven live weights ranging between 250 and 550 kg, at 50-kg intervals. Animals were given food individually and diets were offered ad libitum (except for FM) along with 100 g/day of a commercial vitamin/mineral pre-mix. At slaughter, half carcasses were minced for the determination of fat and protein content and visceral fat depots, perirenal, mesenteric and omental were removed and weighed. The relationships between chemical composition and empty body weight (EBW) at slaughter were assessed using allometric equations (loge y = loge a + b loge EBW). The composition of the silage was 271•9 g/kg toluene DM with a total nitrogen and estimated ME of 26•5 g/kg DM and 11•8 MJ/kg DM, respectively. DM intakes increased (P < 0•001) with increasing level of concentrate and this generated the expected differences in both energy and protein intake. Live-weight gains increased by proportionately about 0•1, 0•18 and 0•34 on the FM, 30C and 70C treatments, respectively, compared with the S alone. Carcass protein deposition (kg) was relatively linear across the slaughter weights 250 to 550 kg, except for the 70C treatment where the slope (shape or curvature parameter, b) was lower compared with S (P = 0•007). Carcass fat (kg) was similar between S and FM. However, at 350 kg EBW and above, the carcasses of animals given concentrate contained more fat (P < 0•01) compared with those on silage. Carcass fat deposition (kg) showed significant curvature between 200 and 500 EBW (kg) and this was most pronounced for the concentrate treatments with the slopes of the 30C and 70C (P = 0•072, P = 0•003 respectively) differing from the silage. Similar responses were observed for the visceral fat depots. Feeding concentrates resulted in a lower proportion of the total fat being deposited as carcass fat (and hence more as non-carcass fat), proportions averaging 0•65 and 0•61 for S and 70C, respectively; P = 0•066). The proportion of mesenteric fat decreased substantially with increasing total fat (P < 0•001). The relative contribution of intramuscular fat (g/kg total fat) in the longissimus dorsi muscle increased with total fat (P = 0•007) and this was particularly apparent for the S, FM and 30C and less so for 70C. It is concluded that good quality grass silage will support high levels of performance without the need for additional concentrate supplementation. The latter may contribute towards increased fat deposition within the animal.

A study was undertaken to examine the effect of level and type of supplement and changes in the chemical composition of herbage through the grazing season on herbage intake, animal performance and rumen characteristics with high-yielding dairy cows. Thirty-two high genetic merit dairy cows were allocated to one of four treatments in a two-phase change-over design experiment. The four treatments involved offering either high-fibre (HF) or high-starch (HS) supplements at either 5 or 10 kg dry matter (DM) per day. Animals rotationally grazed perennial ryegrass swards offered a daily herbage allowance of 23 kg DM. High levels of animal performance were maintained throughout the study with mean milk yields over the 21-week experimental period of 35·5 and 37·2 kg per cow per day on the 5- and 10-kg treatments respectively. Supplement type had no significant effect on herbage intake. Increasing the level of supplementation reduced herbage intake by 0·49 and 0·46 kg herbage DM per kg supplement DM and increased milk yield, with a milk yield response of 0·55 and 0·65 kg/kg supplement DM offered in phases 1 and 2. Supplement type had no significant effect on milk yield and milk butterfat content. However, in both phases 1 and 2, milk protein content was significantly higher with cows offered the HS supplement compared with the HF supplement, this being particularly evident at the higher level of supplementation. Supplement type also had marked effects on milk protein composition. These results indicate that high levels of performance can be achieved with dairy cows on grazed pasture with moderate levels of supplementation.

The purpose of the present study was to evaluate the effect of fermented liquid food (FLF) and the addition of lactic acid to a diet based on wheat and barley on the development of swine dysentery in pigs experimentally infected with a Danish field isolate of Brachyspira hyodysenteriae. Furthermore, to confirm if low non-starch polysaccharide (NSP)-containing diets reduce swine dysentery the effect of different dietary levels of NSP and resistant starch (RS) was evaluated. These diets were based on cooked rice and animal protein, cooked rice and potato starch, cooked rice and wheat bran, or cooked rice and sugar-beet pulp. The experiment was designed as a randomized-block trial and was performed in triplicate including a total of 192 pigs. After feeding the diets for 2 weeks, six pigs in each group were challenged orally with B. hyodysenteriae and observed for another 4 weeks. After challenge, swine dysentery was observed in all feeding groups. The incidence of disease varied between 94% (rice/wheat bran) and 44% (FLF). The effect of diet on faecal shedding of B. hyodysenteriae was statistically significant (P < 0·05). Feeding a diet based on cooked rice with a low content of NSP and RS, did not prevent the development of swine dysentery upon experimental challenge, and increasing the level of NSP or RS did not result in a higher incidence of disease or faecal shedding of B. hyodysenteriae. The incidence of swine dysentery in the FLF group was significantly lower (P < 0·05) compared with all other feeding groups, except for the lactic acid group. In conclusion, a low level of NSP or RS in the diet did not prevent the development of swine dysentery. Furthermore, the lowest incidence of disease was observed in the FLF group, even though this diet has a high content of NSP. The addition of organic acids to the food was not able to reduce infection with B. hyodysenteriae.

Data from pigs between 12 and 120 kg live weight were used to develop a relationship between the capacity for food bulk and live weight. High bulk foods, intended to limit growth, were offered for 21 days to pigs of 12, 36 (600 g sugar-beet pulp per kg (SBP60)) and 108 (800 g sugar-beet pulp per kg (SBP80)) kg live weight. Control pigs were given a low bulk food C at all weights. After 21 days the pigs were slaughtered and measurements made on the gastro-intestinal tract (GIT). In two additional treatment groups SBP60 was offered from a weight of either 36 kg or 72 kg before SBP80 was offered at 108 kg. Daily live-weight gain, after allowing for the effects of a change of gut fill, was less at all weights on the high bulk foods than on C. At all weights the high bulk foods caused a significant increase in the weights of the stomach, large intestine, caecum and gut fill. Effects on the weight of the small intestine were small. Previous nutrition had no significant effect on the adapted performance, or on the size of the GIT, of pigs given SBP80 at 108 kg but pre-feeding SBP60 significantly increased initial consumption of SBP80. Constrained intake was not directly proportional to live weight beyond 40 kg. The absolute capacity for bulk (Cap, kg water-holding capacity per day) was related to live weight (W, kg) by the quadratic function Cap = (0·192.W) - (0·000299.W2). The value of Cap is predicted to reach a maximum when W = 321 kg. The combined weights of the large intestine and caecum (WLIC) changed with W in ways that were similar to the way in which Cap changed. In addition the ratio of Cap to WLIC was close to constant. The combined weight of the large intestine and the caecum may determine the capacity for food bulk in pigs.

We determined milk intake and growth rate of fat-tailed Awassi ram lambs from birth to 30 days of age when sucking ewes that were grazing natural green pasture in the semi-arid Negev. The conversion of milk and energy intake to body mass and body solids gain in the lambs were calculated. Annual rainfall and, as a consequence, pasture availability were below average during the study. Body mass at birth was 4·22 (s.d. 0·71) kg and at 30 days was 12·10 (s.d.1·22) kg for an average daily gain of 256 (s.d.33) g/day. Of the 256 g/day, 100 (s.d.12·3) g/day were body solids, and for every unit body mass increase, proportionately 0·391 was body solids. Milk and energy intakes averaged 1·34 (s.d.0·23) l/day and 5·66 (s.d.0·97) MJ/day, respectively. The volume of milk intake per kg increase in body mass and body solids were 5·2 l and 13·4 l, respectively, whereas, the energy intake per kg increase in body mass and body solids were 22·1 MJ and 56·6 MJ, respectively. Of the total metabolizable milk energy intake, proportionately 0·46 was converted to body energy of the lamb. Although dry matter intake of the ewes was insufficient to prevent body mass loss, they produced sufficient milk to support a relatively high lamb growth rate, presumably by mobilizing fat reserves in the tail.

The objective of this study was to determine if weight and age at weaning affect the response of pigs to inclusion of cooked cereal in their post-weaning diet. In experiment 1, pigs (no. = 116) weaned at 17 to 28 days of age and weighing between 4 and 10 kg were individually given for 28 days post weaning, diets based on: (1) uncooked cereal or (2) cooked cereal (steamed and flaked wheat and maize). The gelatinized starch proportion was 0•265, 0•838, 0•203 and 0•745 for uncooked maize, steam flaked maize, uncooked wheat and steam flaked wheat, respectively. Pigs were offered 2•5 kg of starter diet (16•1 MJ digestible energy (DE) per kg and 17•4 g/kg of lysine). This was followed in each case by link diet (15•2 MJ DE per kg and 16•2 g/kg of lysine) to 28 days post weaning. Thereafter, pigs were grouped and given a common weaner diet and a common finisher diet to slaughter. In experiment 2, pigs (no. = 408) were weaned at between 20 and 28 days of age. Pigs were allocated by weight to heavy (7 to 8 kg), medium (6 to 7 kg) and light (5 to 6 kg) groups (24 groups of 17 pigs) and assigned to treatments as in experiment 1 for 26 days. A common weaner diet was offered between day 26 and day 56. In experiment 1, pig weight, food intake, daily gain, food conversion efficiency and carcass measurements were not affected by cooking (P > 0•05). Regression analysis indicated that weight and age at weaning had a significant association with weight at 28 days post weaning for uncooked (R2 = 0•628; P < 0•001) and cooked (R2 = 0•579; P < 0•001) cereal diets. In experiment 2, there was no interaction between weaning weight and cooking (P > 0•05) and no performance benefit resulted from cooking (P > 0•05). In conclusion, steam flaking did not improve pig performance during the treatment period or at any subsequent period.

Five species of alpine pasture plants from the Pyrenees representing 3 botanical groups: grasses (Festuca eskia, Nardus stricta), forbs (Anthyllis vulneraria, Galium verum) and shrubs (Echinospartum horridum), were collected monthly from June to September and analysed for nitrogen (N) content, cell wall composition, in vitro enzymatic digestibility (DMDe) and volume of gas produced by microbial fermentation. Among the dicotyledenous varieties, A. vulneraria and G. verum showed the highest nutritive value whilst that of E. horridum was low due to high lignin content. Grasses showed moderate nutritive values in June rapidly decreasing thereafter. Nitrogen content and organic matter digestibility (OMDg) of A. vulneraria remained relatively constant through the sampling period whereas it abruptly decreased for remaining species from July. Gas production significantly differed among species during the first 48 h of microbial fermentation but not at later stages of fermentation. Collection date did not affect gas production before 24 h of incubation but significant differences were found thereafter with samples from June and July being more degraded than from August and September. Principal component analysis associated OMDg positively with N content and gas production and negatively with fibre content. Lignin proportion did not significantly correlate with gas production or with OMDg, suggesting that the degree of lignification is not the only factor affecting microbial fermentation but other factors such as lignin tissue locations may be involved. A. vulneraria has been revealed as very good forage with a high potential in extensive animal production systems. Both OMDg and DMDe methods seem more accurate than chemical analyses for evaluating forages at different stages of maturity.

Choice feeding could be more widely applied with pigs if the initial variability between individuals in diet selection was overcome and there was a better understanding of the factors affecting the learning process in groups. In six replicates, two groups of four pigs (live weight 35·5±0·95 kg) were formed containing either an individual trained to select between two foods or an untrained control animal. The groups were offered food L (130 g crude protein (CP) and 5·6 g lysine per kg) and food H (260 g CP and 15·5 g lysine per kg) in two troughs as a choice for a period of 14 days. Food intake was measured twice daily for the first 3 days and then daily. The pigs were weighed three times per week and feeding behaviour was video recorded on the 1st and 3rd days of grouping. There was no effect of the trained pig on the performance of the group over the 2-week period (daily live-weight gain: 1·19 kg and 1·21 kg for the pigs in control or trained groups; s.e.d. 0·057). Within the first 8-h period of food recording pigs in groups with a trained pig selected a diet similar to that of the trained pig, whereas those with a control pig showed initial variation in selection before adopting a pattern in favour of one food, usually after about 3 days. In the first 24 h the pattern of visits to the troughs by the naïve pigs followed that of the trained pig whereas the pigs in the control groups initially visited the troughs at random. After 3 days the difference between the groups was small and largely non-significant. In five of the six replicates the groups selected a diet comprising 0·65H: 0·35L, which was similar to that expected from their lysine requirements. The two groups in the other replicate selected more of food L and this and the other findings are discussed in relation to the influence of social learning, previous nutritional experience and food composition on diet selection by pigs.

The objective of this study was to assess the effect of feeding steam flaked wheat and maize in diets with high and low levels of dairy products and to examine the effect of sequence of feeding the processed cereals in diets for newly weaned pigs. In experiment 1, 96 pigs were weaned at 27 days of age, blocked on sex and weight and assigned as individually penned pigs to four dietary treatments as follows: (a) high dairy product diet (6 kg of starter diet containing 230 g/kg milk powder followed by a link diet containing 125 g/kg milk powder to 26 days) with uncooked cereal (HDP), (b) high dairy product diet with steam flaked cereal (HDPC), (c) low dairy product diet (6 kg of starter diet containing 125 g/kg milk powder followed by a link diet containing no milk powder to 26 days) with uncooked cereal (LDP) and (d) low dairy product diet with steam flaked cereal (LDPC). In experiment 2, 96 pigs were weaned at 19 to 24 days of age, blocked on sex and weight and assigned as individually penned pigs to four dietary treatments containing: (a) uncooked cereal for 26 days, (b) uncooked cereal for 14 days followed by cooked cereal to 26 days post weaning, (c) cooked cereal for 26 days and (d) cooked cereal for 14 days followed by uncooked cereal to 26 days post weaning. Steaming and flaking of wheat and maize did not significantly affect pig performance during the experimental period or at any subsequent period up to slaughter. Daily gain from day 0 to 26 post weaning was 415 and 453 g/day (s.e.13•5; P < 0•05) for low and high dairy product diets, respectively. Food conversion efficiency (FCE) from day 0 to 14 post weaning on the low and high dairy product diets was 1•86 and 1•33 g/g (s.e. 0•14; P < 0•05), respectively. Pigs given the high dairy product diets during the experimental post-weaning period reached final carcass weight 5 days earlier than pigs given the low dairy product post-weaning diets (P < 0•05). In experiment 2, treatment did not affect food intake (mean = 450 s.e. 13•2 g; P > 0•05), daily gain (mean = 382 s.e. 12•5 g; P > 0•05) or FCE (mean = 1•19 s.e. 0•02 g/g; P > 0•05). In conclusion, feeding steamed flaked wheat and maize in post-weaning diets failed to improve pig performance irrespective of dairy product or sequence of feeding cooked cereals.

An experiment was conducted to determine if molasses could be successfully used to administer dotriacontane (C32) and hexatriacontane (C36) n-alkane markers to steers and to compare this method with a commercially available intra-ruminal controlled release device (CRD). The experiment was conducted over two similar periods (runs) using 24 Brahman crossbred steers in each run to study the effect of marker delivery methods and tropical grass hay diets in a randomized complete block design with three replicates. All steers were housed individually in partially covered pens, received one of two buffel-grass hays (B20: 20-week regrowth; 0·72 g nitrogen (N) per 100 g and B8: 8-week regrowth; 1·11 g N per 100 g) and one of four marker delivery treatments (control: no marker; 200 mg/day of C32 and C36 n-alkanes from a CRD or offered three times (Ms ✕ 3) or five times (Ms ✕ 5) a day in molasses). Voluntary intake (VI) and dry matter digestibility (DMD) for diets differed (P < 0·001) with B8 greater than B20. There was no difference among marker treatments for VI but the control treatment had greater, unexplained and possibly spurious, DMD than the Ms ✕ 3 marker treatment. Although the recovery of n-alkanes was variable (0·84 to 1·05) adjacent odd- and even-chain n-alkanes were similar with no differences (P > 0·05) due to marker treatment or diet. The CRD supplied a consistent marker dose between 6 and 18 days after insertion. Deviation from the 24-h mean faecal concentration seldom varied more than 0·03 for the individual markers and 0·05 for C31/C32 and C33/C32 ratios for all treatments. Over all the n-alkanes studied, the between-day variation was less than the within-day variation. For instance, the average of subsamples taken at 06:00 h and 18:00 h was within proportionately 0·05 of the 10-day mean concentration for 0·38 and 0·25 of records for C32 and C36 markers, respectively. It was concluded that molasses containing C32 and C36 n-alkane markers and given either three or five times daily was as accurate as the commercial CRD in administering n-alkane markers to steers and provides a method of delivering n-alkanes over an extended period in grazing studies.

The stomach and small intestine manifest a myoelectric activity pattern called the migrating myoelectric complex (MMC), which is controlled by both environmental and intrinsic factors. The daily MMC pattern has been little investigated, therefore the purpose of the present study was to study it, in weaned pigs given food twice a day. A wireless telemetric recording system was used for 24-h electromyography of the antrum and duodenum. The activity of the antrum showed little change if any, whereas the myoelectric activity of the duodenum significantly changed with respect to the time of day and feeding in conscious pigs. Namely, there were more frequent and regular MMC cycles occurring in the duodenum at night as compared with that during daytime. This change was due to the shortening of phase II of the MMC cycles that were registered at night. Phase I of the MMC showed transient variability in relation to feeding with no impact on the day/night differences. Phase III of the duodenal MMC cycle as well as the ‘feeding pattern’ did not change along with the time of day and feeding regime. In conclusion, daily variation in the duodenum may provide different conditions for digestive processes in the day and night.

Submerging in water is used by many species as a behavioral mechanism to reduce body temperature, and farmed mink have been shown to increase their swimming activity during summer months. Therefore we investigated whether a maintained, seasonally independent, high ambient temperature would lead to more swimming in farmed mink. Twelve mink were housed in a temperature controlled room and subjected to two periods of four different temperatures (8, 16, 24 and 32 °C) with each temperature lasting 4 days. Although some types of activities changed with changes in temperature, the total level of activity was not affected. At high temperatures, the mink did not show any increase in either swimming or stereotyped behavior. It is concluded that within the limits of the experiment, mink will not use submerging in water as a thermoregulatory mechanism.

New Zealand × Californian rabbit does were offered ad libitum three diets: diet A, with 960 g lucerne per kg dry matter (DM), having 8•7 MJ digestible energy (DE) and 108 g digestible protein (DP) per kg DM; diet AF with 920 g lucerne and 50 g animal fat per kg DM, having 9•6 MJ DE and 105 g DP per kg DM; and diet C, as a control diet having 12•0 MJ DE and 122 g DP per kg DM. Productive parameters were measured for the first five parities, and food intake and milk yield during the first two parities.

In experiment 1, 79 does (342 parities) were housed in a cooled building, litters were standardized to eight kits and weaned at 28 days of age. DM intake during lactation was lower (P < 0•001) but DE intake, milk yield and litter growth were higher for group C. Values for does on diet AF generally were between those of groups A and C. Average results for groups A, AF and C were respectively: 59, 65 and 51 days for the parturition interval; 160, 170 and 193 g for daily milk output in the first two lactations; 3•7, 4•0 and 4•5 kg for litter weight at weaning.

In experiment 2, 64 does (294 parities) were housed in a climatic chamber at a constant temperature of 30oC, litters were standardized to six kits and weaned at 35 days of age. DM intake during lactation was lower (P < 0•001) but milk yield and litter growth were higher (P < 0•001) for C does. Average results for groups A, AF and C were respectively: 70, 70 and 56 days for parturition interval; 106, 128 and 128 g for daily milk output in the first two lactations; 3•7, 4•4 and 4•4 kg for litter weight at weaning. Lucerne-based diets allowed a reasonable performance of reproductive rabbit does in the long term, even under hot conditions.

Resistance and resilience to naturally acquired gastro-intestinal (GI) nematode parasite infections (predominantly Haemonchus contortus) were studied in 1785 lambs born over six lambings (1991 to 1996) consisting of 212 Red Maasai, 311 Dorper and 1262 crossbred (Red Maasai-Dorper) lambs in the sub-humid coastal region of Kenya. These lambs were the progeny of 41 Dorper and 35 Red Maasai rams. Live weights (LWT), blood packed cell volume (PCV) and faecal egg counts (FEC) were recorded at 1- to 2-monthly intervals from birth until the lambs were about one year of age. Red Maasai were more resistant and resilient post weaning to infections with GI nematodes than Dorper lambs as shown by their significantly lower FEC and their significantly higher PCV, respectively. An increasing proportion of Red Maasai genes in the crossbred lambs was associated with decreased FEC and higher PCV, but there was no heterosis for logarithm-transformed FEC (LFEC) or PCV. From one month of age Red Maasai lambs were significantly lighter than Dorper lambs by about 1 kg, but Red Maasai lambs had significantly lower lamb mortality rate from birth to 12 months of age (proportionately 0·30 and 0·66, respectively). Heritability estimates from a repeated measures analysis for records taken at 6 and 8 months of age were 0·14 (s.e. 0·05) for PCV from an animal model and 0·12 (s.e. 0·05) for LFEC from a sire model. The heritability estimate for LFEC from a repeated measures analysis including the four measurements recorded between 6 and 12 months of age was significantly higher (P < 0·05) for Dorper-sired lambs (0·15, s.e. 0·05 for an animal model and 0·19, s.e. 0·07 for a sire model) than for Red Maasai-sired lambs (0·00 and 0·01, s.e. 0·02). The phenotypic and genetic correlations between PCV and LFEC were moderately to highly negative and averaged –0·34 and –0·81, respectively. None of the genetic correlation estimates between LWT and PCV and LWT and LFEC for lambs post weaning were significantly different from zero. The heritability estimates for PCV and LFEC have important implications for within-breed genetic improvement programmes: for the Red Maasai, improvement should concentrate on resilience (e.g. selection for high PCV); for the Dorper, selection should be feasible for both improved resistance (low FEC) and resilience (high PCV).

The rôle of body reserves stored during early pregnancy on the periparturient breakdown of resistance to nematode parasites was investigated. From the 35th day of pregnancy, 46 ewes were distributed in four groups and given access to a lucerne pelleted diet. Two groups were given food at maintenance (M and C) and the other two were offered food either ad libitum (H) or at 0·70 their maintenance requirements (L) in order to achieve three well differentiated levels of body reserves by the 90th day of pregnancy when backfat thickness reached a mean value of 10·6, 7·5, 7·4 and 5·0 mm for H, M, C, and L treatments respectively. After the 90th day of pregnancy all animals were given food at 50 g/kg live weight per day. All ewes in groups H, M and L received 5000 infective larvae per week (40% Teladorsagia circumcincta, 40% Trichostrongylus colubriformis, 20% Haemonchus contortus) from 5 weeks before to 3 weeks after lambing. The animals in group C remained as uninfected controls.

Host resistance, as measured by faecal egg counts, was significantly affected by the nutritional treatment established during early pregnancy, showing a mean excretion of 546, 766 and 1007 eggs per gram (e.p.g. ) for H, M, and L treatments, respectively, until 3 weeks post lambing. This response was accompanied by a significant effect on circulating eosinophils and better fed ewes showed a higher concentration with a maximum mean value of 10·1, 6·9, 5·5 and 4·0 cells per mm3 for H, M, L and C treatments, respectively, 2 weeks post infection. The effect of the worm infection per se was evident in that the lambs of the M treatment ewes grew at 0·90 of the rate of those in the control treatment (189 v. 213 g/day). Ad libitum feeding in early pregnancy appeared to sufficiently compensate for this depressive effect, with the H ewes producing lambs that grew at a rate similar to those of the C ewes (213 v. 213 g/day).

The results support the view that fat mass stored by ewes in early pregnancy is involved in the expression of immunity against gastro-intestinal nematode infection around parturition. Furthermore, the depressive effect of ewes’ infection on lambs’ growth rate can be overcome by increasing the plane of nutrition of their dams. These results have clear implications for grazing animals, particularly their nutritional management in early pregnancy and provide a simple management strategy in sustainable management systems.

The objective of the study was to evaluate the effect on reproductive performance of varying level of concentrate supplementation with both high and medium genetic merit cows in a spring calving grass-based system of milk production. The effect of year, cow genetic merit for milk production and concentrate feeding level on milk production, body condition score, live weight, blood metabolites and dry-matter (DM) intake were studied. A repeated measures model with a factorial arrangement of genetic merit and concentrate feeding level was used to do this. Associations between these variables and pregnancy to first service (PREG1), pregnancy to first and second service (PREG12) and overall pregnancy (PREG) rates were assessed using logistic regressions for year 2.

Cows were grouped into high (HM) and medium (MM) genetic merit based on their pedigree indices for milk production (PD milk). The HM cows had a PD milk of + 276 (s.d. 100) kg, while the MM cows had mean PD milk of + 81 (s.d. 95) kg. Within genetic merit groupings, cows were assigned to one of three concentrate feeding levels; low (LC), 376 kg; medium (MC), 810 kg; and high (HC), 1540 kg of concentrate per cow per lactation. In year 1, all 78 cows were second lactation animals, while in year 2, 71 cows (previously in year 1) were third lactation and 12 second lactation. All cows calved between February and April, and were presented for rebreeding from late April until late July each year.

When treatment means were compared, genotype and concentrate feeding levels had no significant effects on reproductive performance while year was significant for most parameters. Comparing year 2 to year 1 pregnancy rate to first service (P 0•001; 37 v. 64%), pregnancy rate to first and second service (P < 0•05; 64 v. 81%), overall pregnancy rate (P < 0•05; 78 v. 92%) were lower. Also in year 2, cows had significantly higher milk yields at first insemination (36•9 v. 32•3 kg per cow per day), greater live-weight losses from calving to first insemination (-86 v. –53 kg per cow), lower live-weight gain in the 90 days after their first insemination (+ 24•6 v. + 34•2 kg per cow), higher DM intake (20•6 v. 17•3 kg DM per cow per day) and lower plasma glucose concentrations (3•18 v. 3•61 mmol/l) than in year 1.

In year 2, there were significant negative associations between the likelihood of PREG12 and both PD milk and live-weight gain in the 90 days after first insemination. The results of this study indicate that continued selection for increased milk production, resulting in greater partitioning of energy to milk production rather than body reserves will reduce reproductive performance and offering higher levels of concentrate supplementation may not alleviate this problem.