The digestive system of the weaned piglets can be affected by the type of ingredients present in the diet, and a high fibre content in diets can limit the use of other nutrients and energy. The study was conducted to determine the effects of multicarbohydrase (MC) and phytase (Phy) supplementation on the nutritive value of wheat bran (WB) in weaned piglets. Multicarbohydrase preparation had 700 U α-galactosidase, 2200 U galactomannanase, 3000 U xylanase and 22 000 U β-glucanase per kilogram of diet, and Phy had 500 phytase units – FTU/kg of diet. Twenty-five weaned piglets (6.1 ± 0.63 kg) at 21 days old were fed five diets in a completely randomised experimental design with a 2 × 2 + 1 (0 and 200 mg/kg MC; 0 and 50 mg/kg Phy; and basal diet – BD) factorial arrangement used to determine treatment effects. An additional group of piglets was fed a corn-basal diet during apparent digestibility of nutrients, and fed a 5% casein-corn starch basal diet during apparent and standardised ileal digestibility (SID) of amino acid evaluations. Piglets were individually caged until 38 days old, when Ileal digesta was collected at slaughter. Test diets were made by mixing the basal diets and WB 7 : 3 (w/w), with or without MC, Phy or the combination. There was an interaction trend (P = 0.07) between MC and Phy in the balance of ash, digestible energy (DE) and metabolisable energy (ME). Effects of MC (P < 0.01) on DM, N retention, DE and ME, as well as an effect of Phy (P < 0.05) on ash, DE and ME and a trend in protein digestibility (P = 0.07) also was observed. The enzyme combination showed effect (P < 0.05) on SID of Lys, Pro and Ser; as a trend (P < 0.07) on His, Thr and Val. Isolated, MC also suggested improving (P < 0.07) on SID of His, Lys, Ala (P < 0.05), while Phy improved (P < 0.06) SID of Leu, Lys, Met (P < 0.01), Thr, Val, Ala (P < 0.01), Pro and Ser (P < 0.05). The MC carbohydrate complex was characterised as a viable alternative to increase the apparent nutrients digestibility and SID of amino acids when WB was used in the diet of young pigs and, when combined with Phy, suggested an additive effect on the apparent use of energy.

This study examined feed intake, growth, body condition, muscle glycogen content and nutrition-related health in 16 Standardbred horses fed a high-energy, forage-only diet ad libitum and allocated to either a control training programme (C-group) or a training programme with the high-intensity training distance reduced by 30% (R-group), from January as 2-year olds until December as 3-year olds. Feed intake was recorded on 10 occasions during 3 consecutive days. Body weight was recorded once in a week and height, body condition score (BCS), rump fat thickness and thickness of the m. longissimus dorsi were measured at 7±3-week intervals throughout the study. Muscle biopsies of the m. gluteus medius were taken in December as 2-year olds and in November as 3-year olds and analysed for glycogen content. Nutrition-related health disorders were noted when they occurred. Horses consumed 1.7% to 2.6% dry matter of BW, corresponding to 19 to 28 MJ metabolisable energy/100 kg BW. There were no differences between training groups in feed intake or any of the body measurements. The pooled weekly BCS was maintained between 4.8 and 5.1 (root mean square error (RMSE)=0.4). Muscle glycogen content was 587 and 623 mmol/kg dry weight (RMSE=68) as 2- and 3-year olds, respectively, and there was no difference between training groups. When managed under normal conditions, no nutrition-related health disorders or stereotypic behaviours were observed. It was concluded that the training programme did not affect feed intake, growth, BCS or muscle glycogen content. In addition, the forage-only diet did not appear to prohibit muscle glycogen storage, growth or maintenance of body condition, and seemed to promote good nutrition-related health.

Twenty-eight female and 26 uncastrated male Scottish Blackface sheep were shorn and subjected to two acute cold exposures one week apart. Between exposures and for one week before the first exposure the sheep were kept either at +30°C (thermoneutral), or at +8°C (subcriticai), or at + 30°C with daily short cold shocks. Food intakes were restricted.

Females showed significantly greater resistance to body cooling than males during both acute exposures.

Both males and females showed acclimatization (increased resistance to body cooling) as a result of the first acute exposure.

Exposure to +8°C for one week did not produce significant acclimatization. Exposure to +8°C for two weeks tended, in females only, to increase acclimatization above that resulting from the first acute exposure.

Daily short cold shocks reduced cold resistance and inhibited acclimatization in females, but had little effect in males.

The male sheep lost significantly more weight during treatment and became thinner than the females. It was suggested that this, and their low cold resistance, might be related to a lesser ability of males to store fat as a subsequent source of energy.

Miniature pigs have been recognized as valuable experimental animals in medical research. However, porcine models related to gene knockout of human diseases are not widely available. The objective of this study was to establish Mx1-Cre pigs using somatic cell nuclear transfer. In this study, we created transgenic pigs using somatic cell nuclear transfer (SCNT). Transfer of 210, 230, 250 and 215 zygotes to four surrogates produced 10 piglets. The Cre recombinase expression in transgenic pigs was studied using reverse transcriptase (RT)-PCR and immunohistochemistry. Mx1-Cre swine were shown to harbor the Cre gene in their genomic DNA using the PCR. In conclusion, Mx1-Cre transgenic piglets were successfully produced by SCNT. These transgenic swine, in conjunction with inducible systems for controlling Cre expression and function, are likely to have a profound impact on the study of human diseases.

The effect of increased female reproductive rates on selection response, on efficiency of progeny testing and on the openness of the nucleus was investigated in open nucleus breeding plans. Conventional progeny testing plans and closed nucleus plans are special classes of open nucleus plans. In the open nucleus plans, generation intervals and selection across tiers were optimized. The number of offspring per elite dam was varied from 1 to 41, progeny testing of young bulls in the female base population was varied from 0 to 100 test records and the size of the nucleus was varied from 250 to 2000 young bulls born per year. Also efficiency of selection was varied: efficient selection in T(heoretical)-schemes and less efficient selection in P(ractical)-schemes. Especially, selection of base parents was less efficient i n P-schemes.

The deterministic prediction model took account of variance reduction due to selection and reduction of selection differentials due to correlations between estimated breeding values of relatives (order statistics). For closed nucleus plans, the results of the model were verified with Monte Carlo simulation results.

By increasing female reproductive rates, genetic gain increased by a factor 0·08 and 0·16 for the T- and P-schemes respectively. The nuclei in P-schemes were less open, due to the less efficient selection in the female base population. Schemes that were less open benefited more from increased female reproductive rates because selection differentials in small nuclei increased more than those in large base populations. The optimal open nucleus plan became less open with increasing female reproduction. Generally, progeny testing of bulls reduced genetic gain (by up to a factor 0·1) but it also reduced inbreeding rates. Progeny testing was more efficient in schemes that were less open: in P-schemes with 41 offspring per dam, progeny testing increased genetic gain. With many offspring per dam there were fewer full-sib families, causing lower selection differentials due to order statistics effects. This effect could be prevented by increasing the size of the nucleus.

Maternal nutrition during pregnancy can affect kidney development in the foetus, which may lead to adverse consequences in the mature kidney. It was expected that high-salt intake by pregnant ewes would lead to a reduction in foetal glomerular number but that the ovine kidney would adapt to maintain homoeostasis, in part by increasing the size of each glomerulus. Merino ewes that were fed either a control (1.5% NaCl) or high-salt (10.5% NaCl) diet during pregnancy, as well as their 5-month-old offspring, were subjected to a dietary salt challenge, and glomerular number and size and sodium excretion were measured. The high-salt offspring had 20% fewer glomeruli compared with the control offspring (P < 0.001), but they also had larger glomerular radii compared with the control offspring (P < 0.001). Consequently, the cross-sectional area of glomeruli was 18% larger in the high-salt offspring than in the control offspring (P < 0.05). There was no difference in the daily urinary sodium excretion between the two offspring groups (P > 0.05), although the high-salt offspring produced urine with a higher concentration of sodium. Our results demonstrated that maternal high-salt intake during pregnancy affected foetal nephrogenesis, altering glomerular number at birth. However, the ability to concentrate and excrete salt was not compromised, which indicates that the kidney was able to adapt to the reduction in the number of glomeruli.

The management of pastures used by horses poses various problems: swards are often grazed down rapidly, patches of bare ground and refused areas develop. In order to gain a better understanding of the plant-animal interaction behind this problem the influence of sward height on bite dimensions (bite depth, weight, volume, area) of horses was investigated. Perennial ryegrass (Lolium perenne) microswards were grown on artificial substrate to four different heights (3, 8, 15, 19 cm) but the same plant density. Biomass and bulk density for each sward height was determined. Eight horses (predominantly Thoroughbred ×) were allowed to take six bites of each grass height. Bite depth, weight, volume and bite area were calculated.

Bite depth, weight, volume and area were not fixed, but increased with sward height (P < 005). For all sward heights, the horses removed between 51% and 68% of the initial grass length. The horses adjusted their bite dimensions to sward height but did not maximize food intake per bite. The response to sward height might be explained by a preference for easily digested food or the trade-off between energy intake and the cost for food processing.

This experiment suggests that grass height has a major influence on bite dimensions of horses. However there may be more complex factors influencing ingestive behaviour of horses (e.g. age, dietary experience and social behaviour) that have to be considered when horses are grazing pasture.

An experiment was conducted to measure the effects of stocking density (increased number of pigs per pen) on lysine requirements of pigs grown from 25 to 60 kg live weight. Two hundred and sixty-four female Large White ✕ Landrace pigs were assigned at 25 kg to one of four dietary lysine treatments (13·3 (L1); 11·4 (L2); 9·5 (L3) and 7·6 (L4) g/kg) and either seven or 13 pigs per pen (or 1 0 and 0·5 m2 per pig, respectively). An additional treatment of one pig per pen (20 m2 per pig) was included to compare the responses of solitary- versus group-penned pigs. Animals were given ad libitum access to dietary treatments from a mean pen starting weight of 261 (s.e. 0·35) kg to a mean pen finishing weight of 63·4 (s.e. 0·61) kg live weight. There were no significant interactions between dietary lysine content and floor space per pig on food intake (FI), average daily growth rate (ADG), the amount of food per unit of gain (FCR) and the rate of protein retention (PR). Significant interactions were evident for body composition and the rate of lipid retention (LR). Over the weight range 25 to 40 kg there were significant differences in FI (P < 0·05) and FCR (P < 0·001) between dietary lysine treatments but most of these differences had disappeared over the 40 to 60 kg live weight. Individually penned animals had significantly higher (P < 0·05) FI and ADG than group-penned animals. However, there were no differences between seven and 13 pig per pen treatments. Stocking density had no effect on LR or body protein content but did cause a significant reduction in PR (P < 0·001) and an increase in body lipid content (P < 0·05) as the number of pigs per pen increased from seven to 13. Lysine requirements (expressed in g/day) therefore could be seen to be reduced with increasing stocking density. However, as lysine intake was reduced in group-penned animals, the reduced daily requirement does not necessarily warrant a reduction in the lysine content of the food. Feeding according to the requirements for maximum PR will still produce the best carcass and growth performance irrespective of the group size. The improvement in PR associated with higher dietary nutrient levels did not completely offset the adverse physiological effects of higher stocking density but may partly counteract the effect of reduced lysine intake. However, there were indications that feeding crowded pigs a lower dietary lysine concentration may not further reduce the already diminished protein (lysine) growth rate. An additional experiment was performed to test whether the number of feeder bins may have constrained food intake and therefore growth in group-penned animals. The results of this experiment showed that the number of bins had no significant effect on FI, ADG and FCR in group-penned pigs, and therefore a single feeder bin was not considered a constraining factor in pigs housed with limited floor space.

To investigate the effects of energy source and protein level of diets on milk protein content, 12 multiparous Holstein-Friesian cows were used in a 4 × 4 Latin square change-over experiment with 4-week periods. Four diets were offered, with ad libitum silage as proportionately 0·40 of the diet, and the remaining 0·60 as one of four concentrates, two based on barley and two on molassed sugar-beet pulp. Two protein levels were achieved by altering the amounts of digestible undegraded protein in the concentrates, with all diets formulated to supply equal quantities of rumen degradable protein. There was no effect of diet on dry-matter intakes. Both starch and high dietary protein levels significantly increased milk protein concentration (P < 0·05), but had no effects on milk fat and lactose concentrations. Mean milk yields were significantly higher (P < 0·05) with increased dietary protein. Dietary protein significantly affected the yields of milk protein (P < 0·01) and lactose (P < 0·05) but not that of fat. Urinary allantoin excretion was significantly greater with both high protein (P < 0·05) and starch-based diets (P < 0·05). No significant interaction effects were found. It is concluded that dietary effects were due largely to differences in supply of rumen degradable protein; increases in milk protein concentration were therefore brought about by increasing the protein supply to the animal.

Progesterone is essential for maintaining pregnancy, and several authors have suggested that low peripheral concentrations of progesterone may be responsible for high rates of embryonic loss. The primary organ involved in the catabolism of progesterone is the liver, and cytochrome P450 2C and 3A sub-families account for a large proportion of this catabolism. Elucidating a mechanism to decrease progesterone catabolism, thereby increasing embryonic and uterine exposure to progesterone, seems a logical approach to ameliorate high rates of embryonic loss. The objectives of the current experiment were to determine the pattern of insulin secretion after supplementing feed with either sodium acetate or sodium propionate and to determine any association between the differential patterns of insulin secretion with the hepatic activity of cytochrome P450 2C and 3A and progesterone clearance. Sixteen ovariectomized ewes were fed 3 kg/day for 10 days of a diet consisting of 50% corn silage, 38% triticale haylage, 12% soybean meal and 600 ml of 3.5 M sodium acetate (energy control; n = 8) or 2.0 M sodium propionate (gluconeogenic substrate; n = 8). Equal portions of the ration (1 kg as-fed basis along with 200 ml of 3.5 M sodium acetate or 2.0 M sodium propionate) were offered three times daily at 0600, 1400 and 2200 h. Concentrations of insulin in plasma were determined immediately before feeding and at 15, 30, 60, 90, 120, 180, 240 and 300 min after feeding. Progesterone clearance from peripheral circulation (ng/ml per min) was measured by giving a 5 mg injection of progesterone into the left jugular vein and collecting blood via the right jugular vein at 0, 2, 4, 6, 8, 10, 15, 20 and 30 min afterwards. Liver biopsies were taken 1 h after feeding to determine cytochrome P450 2C and 3A activities. Insulin concentrations in ewes supplemented with sodium propionate were elevated at 15, 30 and 60 min after feeding compared to the sodium acetate group. Cytochrome P450 2C and 3A activities were decreased 1 h after feeding in the sodium propionate-treated ewes relative to sodium acetate. Insulin appears to down-regulate cytochrome P450 activity, which could be used to decrease the catabolism of progesterone during early gestation, thereby increasing peripheral concentrations of progesterone and, consequently, embryonic exposure to progesterone.

Thirty-four Dorset and 34 Suffolk rams were slaughtered in pairs within breed at birth, weaning, at monthly intervals to 420 days and then at bimonthly intervals until 600 days to compare factors used to estimate mature size and to determine how genetic size-scaling affects the comparison of body composition between breeds. At equal empty body weights there were no detectable differences between the breeds in amounts of water, protein or ash but Dorsets contained more lipid. Dorset and Suffolk asymptotic values of water (40 and 61 kg), water-plus-protein-plus-ash (51 and 77 kg), metacarpal bone length (127 and 147 mm) and metacarpal bone weight (59 and 101 g) were used to estimate mature size. Regardless of the estimator of mature size, there were no significant differences between breeds in degree of maturity at a given metabolic age. At the same degree of maturity within the estimators of mature size, there were no differences between breeds in the degree of maturity of water, protein or ash, with the exception of small differences in protein for two of the mature size indicators. Because lipid appeared to accumulate without limit in these sheep, the mature body was assumed to contain 300 g lipid per kg. Using this proportion to estimate amount of mature lipid, there was a higher degree of maturity of lipid for Suffolk than for Dorset rams at equal degrees of maturity of water, water-plus-protein-plus-ash or metacarpal bone weight. Thus, Dorsets with greater lipid content at equivalent empty body weights were leaner than Suffolks when adjusted for mature size.

1. Two experiments have been performed to compare the performance of pigs given cool ‘whey’ (15°C) with that of pigs fed warm ‘whey’ (40°C). Pigs were penned individually and the ‘whey’ was reconstituted from concentrated materials.

2. In both experiments pigs offered cool ‘whey’ grew at a slower rate and required more dry matter/kg live-weight gain than pigs offered warm ‘whey’; the differences in rate of gain were 11 % at 16°C air temperature in Experiment 1 and 5% at 22°C air temperature in Experiment 2.

3. It was estimated that the ‘heat of warming’ for the cool ‘whey’ might have accounted for its entire effect on rate of gain.

A long-term experiment (first 24 weeks of lactation) with Danish Black and White cows and a short-term experiment with Jersey cows (experiment periods of 6 weeks) were carried out. In the long-term experiment, the effect of supplementing a normal dairy ration with 0·5 kg calcium (Ca) soap, 10 kg Ca-soap or 2 kg rolled barley was investigated in two herds, where silage was given ad libitum. The daily intakes of fatty acids in the diets were approximately 625, 1000, 1400 or 650 g respectively. Energy intake increased markedly by the supplementation, but not differently between soap or barley supplementation. The effect on milk production was not consistent in the two herds. In one herd, the soap supplement tended to increase milk fat yield (80 g/day) but not more than the barley supplementation which, in contrast to the fat supplementation, also increased milk protein yield. The effect of the fat was consistent over the first 6 months of lactation. In the other herd, only small differences in milk production were obtained with either supplements. In the short-term experiment carried out in mid lactation, a supplement of 0·8 kg Ca-soap increased daily intake of fatty acids from 730 to 1280 g per cow daily. Total food intake, milk and milk fat yield were not affected by the supplement but milk protein yield and live-weight gain were significantly reduced.

Thirty-four British Friesian bull calves were used in experiments to identify diurnal patterns of respiratory quotient (RQ), as an indicator of substrate utilization and to measure energy balance when the same daily amount of milk replacer was given on either 1, 2, 4 or 6 occasions. Each calf spent two 4-day periods in an open-circuit respiration chamber followed immediately, in selected calves, by an 8-day period in a metabolism crate, period 1 starting when calves were 12 days of age and period 2 at 28 days of age. The amount of milk replacer given daily was 32 and 48 g/kg M0·75 during periods 1 and 2 respectively.

Neither rate of live-weight gain nor the energy balance of the calves was affected by frequency of feeding. However, raising the frequency of feeding from one to four times daily significantly affected the pattern of RQ. Reduced feeding frequency tended to raise the mean maximum and lower the mean minimum values of RQ; reducing the frequency of feeding significantly increased the range in RQ (F < 0·01).

The apparent dry-matter digestibility of the milk replacer was higher in 36-day-old than in 20-day-old calves (0·93 v. 0·88; s.e.d. 0·011, P < 0·01). The effect was mainly due to an increase in the digestibility of fat (0·82 v. 0·73; s.e.d. 0·019). In 20-day-old calves, there was a linear increase in fat digestibility with increased frequency of feeding (P < 0·01) rising from 0·67 in calves given milk once daily to 0·85 when milk was given in six meals.

The results suggest that calves given milk replacer once daily (at a level of intake of 32 rising to 48 g milk powder per kg M0·75) do not pass through a diurnal period of severe nutrient deprivation and that raising frequency of feeding would do little to improve efficiency of energy utilization.

The effects of different types of energy or protein supplementation on performance of cows given grass silage-based diets were studied. The possibility of maintaining high energy intakes by using different grain sources, barley or maize, or by the use of the physical processing of the barley was investigated. In addition, the relative quality of rapeseed meal as a protein supplement compared with alternative protein supplements was examined. In experiment 1 16 Finnish Holstein-Friesian cows were used in a cyclic change-over design experiment with eight diets and four 21- day periods. The concentrate supplements comprised a 2 ✕ 2 ✕ 2 factorial arrangement of two grain sources (barley (B) and maize (M)) given either ground (T–) or steam-rolled (T+), each supplemented with either rapeseed expeller (R) or a mixture of maize gluten and soya-bean meal (GS). Grass silage was given ad libitum and concentrates at a rate of 11·2 kg DM per day. M supplements increased milk, milk protein and lactose output (P < 0·05) and decreased milk urea concentration (P < 0·01) compared with B supplements. Blood β-hydroxy-butyrate (BHB) and plasma urea concentrations were higher (P < 0·01) for B than M diets. R supplements increased silage intake, energy-corrected milk yield and milk protein output and concentration (P < 0·05) compared with GS supplements. Steam-rolled grain decreased food intake, blood BHB (P < 0·05) and plasma and milk urea concentrations (P < 0·001). Steam rolling improved organic matter digestibility (grain ✕ processing interaction, P < 0·05) with M but not with B supplements.

In experiment 2 four Finnish Holstein-Friesian cows fitted with rumen cannula were used in a balanced complete change-over design to evaluate ground or steam-rolled barley (T– v. T+) and two protein treatments (rapeseed expeller, R or a mixture of maize gluten/soya-bean meal/sugar beet solubles, GSS). Cows were given concentrates at 11·2 kg dry matter (DM) per day and offered grass silage ad libitum. There were no differences (P > 0·05) in food intake, digestibility or milk production and composition between treatments. Plasma urea concentrations (P < 0·01) and molar proportion of butyrate (P < 0·05) in rumen fluid were decreased with R compared with GSS supplements. The results showed that replacing B with M grain resulted in minor increases in milk production. Steam rolling of grain did not influence animal performance. Among the protein supplements R increased animal performance compared with GS supplement.

Scottish Blackface ewes in uniform, good, body condition at mating were differentially fed during pregnancy, such that two groups lost 0·15 to 0·20 (groups A and B) and one group gained 0·05 (group C) of maternal live weight by lambing time. The treatments had little effect on the number of lambs born per ewe lambing (1·39, 1·46 and 148 respectively).

Prior to parturition, group A was transferred to a poor hill pasture, and groups B and C to an improved upland reseeded pasture. Herbage intake by six single- and six twin-suckling ewes from each group was estimated in the 3rd, 6th and 8th week after parturition, and mean daily milk production was estimated on 1 day following each intake measurement period. Herbage intake by six dry ewes in each of groups A and B was also estimated.

There were significant differences amongst groups A, B and C, respectively, in mean organic matter digestibility of the herbage consumed (0·701, 0·771 and 0·773), mean daily digestible organic-matter intake (1·06, 1·46 and 1·46kg), mean live-weight change over the period ( –2·9, +5·4 and +l·3kg) and mean daily milk yield (0·64, 1·93 and 1·95 kg).

By the following mating time, after grazing the same pasture from weaning, there was still a difference in body condition score according to pasture type during lactation (2·08, 2·36 and 2·29, respectively). Ovulation rate measured after mating was consistent with the direct effect of body condition (1·34, 1·56 and 1·52, respectively).

Data from 4150 Landrace pigs tested during the period 1989-94 for backfat thickness and age at 100 kg in an open selection nucleus were analysed with the standard restricted maximum likelihood/best linear unbiased prediction method and with a Bayesian approach based on the marginal posterior distributions of parameters of interest achieved via Gibbs sampling. Breeding values and fixed effects were sampled from normal distributions and (co)variance components from inverted Wishart distributions. The Bayesian analysis indicated that the selection was effective for both traits. Assuming flat priors for the (co)variance components, the posterior means of the annual rates of response to selection for both traits were −0·473 days and −0·212 mm. The influence of informative priors constructed from (co)variances estimated in the French Landrace breed on inferences about genetic and common environmental parameters, genetic group effects and total and annual responses was also examined.

In all, 18 multiparous and 19 primiparous Holstein dairy cows were used in a completely randomized design with restrictions to evaluate the effects of feeding propylene glycol (PG) as a dry product, via two delivery methods, on production and blood parameters. PG treatments were administered from parturition through 21 days postpartum. Treatments were: (i) control, no PG; (ii) top dress, 162.5 g PG/day by top dressing onto the total mixed ration (TMR) and; (iii) mixing, 162.5 g PG/day as a part of the TMR by incorporating it into the TMR. PG used was a dry product which contained 65% pure PG and 35% silicon dioxide as the dry carrier. Coccygeal blood was sampled on 4, 7, 14 and 21 days in milk (±1.50 pooled s.d.). Supplementation of dry PG by top dressing onto, or incorporating into, the TMR had no effects on average dry matter intake, milk yield and composition, serum insulin, serum and plasma metabolites and milk ketones. Concentrations of urine ketones tended (P = 0.10) to be reduced by PG supplementation from 41.5 to 15.2 mg/dl. Supplementation of PG tended (P = 0.07) to decrease the incidence for subclinical ketosis from 39% to 24% and 13% for cows fed a TMR supplemented with no dry PG, with dry PG as a top dress and dry PG as a part of the TMR, respectively. It is concluded that supplementing PG as a dry product via incorporating into the TMR is as effective as when used as a top dress, based on the efficacies of both delivery methods to numerically reduce urine ketones concentrations and, therefore, the incidence for subclinical ketosis during the first 21 days of lactation. However, it should be noted that the number of cows used in the current study was minimal, and more cows are needed to confirm the efficacy of supplementing PG as a dry product on reducing the prevalence of subclinical ketosis in dairy cows during the first month of lactation.

This study investigated the physiological basis of differences in nutrient partitioning between the North American (NA) and New Zealand (NZ) strains of Holstein–Friesian cattle by determining the responses to homeostatic challenges at two stages of lactation. Glucose tolerance tests, epinephrine challenges and insulin challenges were carried out on consecutive days commencing on day 32 ± 0.48 (mean ± s.e.) of lactation (T1) and again commencing on day 137 ± 2.44 of lactation (T2). The insulin and non-esterified fatty acid (NEFA) responses to glucose infusion did not differ between the strains. The NZ strain had a greater clearance rate (CR) of glucose (2.04% v. 1.66%/min) and tended to have a shorter (34.4 v. 41.1 min) glucose half-life (t½) at T2 when infused with glucose. The NA cows had a greater glucose response to epinephrine infusion across T1 and T2, and tended to have a greater insulin response to epinephrine infusion. Plasma NEFA concentration declined to similar nadir concentrations for both strains at T1 in response to insulin, though from a higher basal concentration in NA cows, resulting in a greater (−2.29 v. −1.38) NEFA area under the response curve for NA cows. Glucose response to insulin varied with time, tending to be greater for NA at T1, but tending to be lower for NA at T2. The results indicated that NA cows had a greater glycogenolytic response to epinephrine, but both strains had similar lipolytic responses. The results also imply that higher basal circulating NEFA concentrations in the NA strain in early lactation were not due to diminished adipose tissue responsiveness to insulin. There were indications that glucose CR was greater in NZ cows in mid-lactation, and may form the basis of increased body tissue accretion during mid- to late-lactation in this strain.

Our work aims at the exploration of cortisol secretion in the Bedouin goat, native to the Algerian Sahara desert, to understand the mechanisms of adaptation to extreme hot climates. In the present study, diurnal and seasonal variations of cortisol concentrations were measured in basal conditions, as well as the response to ACTH stimulation tests across seasons in bucks. The plasma concentrations of cortisol showed no diurnal cycle but a large variation across seasons. The highest levels occurred in summer and winter when the environmental conditions are at their extreme levels. The rectal temperature showed nychthemeral and seasonal variations, and BW was also different across seasons with highest values in summer and lowest in winter. The results obtained after administration of two doses (2 or 10 μg/kg BW) of synthetic ACTH to three different age groups (kids, adults and elderly animals) showed a strong increase in plasma cortisol concentrations under all conditions with maximum levels achieved between 15 and 120 min. The analysis of the area under the cortisol curve showed no significant difference between the responses to the two doses of ACTH and between age groups, but showed seasonal variations with the lowest response in autumn than in other seasons. We conclude that season significantly affects secretion of cortisol in both basal state and under ACTH stimulation. However, the variation of adrenal reactivity to ACTH is not sufficient to explain seasonal differences, and in particular the summer peak in basal circulating cortisol concentrations. Further research should focus on the respective contribution of environmental factors (such as day length, temperature, humidity) and the mechanisms involved in cortisol regulation.