Key determinants of adaptive strategies of goats to a 2-day nutritional challenge during early lactation

Little is known about the key determinants of the physiological adaptations to environmental challenges and how these determinants interact. We evaluated how the response/recovery profiles to a short-term nutritional challenge during early lactation are affected by early-life nutritional strategies in dairy goats divergently selected for functional longevity. We used 72 females, split into two cohorts, daughters of Alpine bucks divergently selected for functional longevity. The females from the two lines were fed with two divergent diets, normal vs low-energy, from weaning until the middle of first gestation, and then fed with the same standard diet. Individual BW, body condition score, morphology, and plasma samples were collected from birth to first kidding. The adaptative physiological strategy to a nutritional challenge was assessed via a 2-day feed restriction challenge, during early lactation, which consisted of a five-day control period on a standard lactation diet followed by a 2-day challenge with straw-only feeding and then a 10-day recovery period on a standard lactation diet. During the challenge, DM intake, BW, milk yield (MY), and plasma and milk metabolite composition were recorded daily. Linear mixed-effects models were used to analyze all traits, considering the individual nested in the cohort as a random effect and the 2 × 2 treatments (i.e., line and rearing diet) and litter size as fixed effects. Linear mixed-effects models using a piecewise arrangement were used to analyze the response/recovery profiles to nutritional challenge. Random parameters estimated for each individual, using the mixed-effects models without the fixed effects of rearing diet and genetic line, were used in a stepwise model selection based on R2 to identify key determinants of an individual's physiological adaptations to environmental challenges. Differences in stature and body reserves created by the two rearing diets diminished during late gestation and the 5-day control period. Genetic line did not affect body reserves during the rearing phase. Rearing diet and genetic line slightly affected the recovery profiles of evaluated traits and had no effects on prechallenge and response to challenge profiles. The prekidding energy status measures and MY before challenge were selected as strong predictors of variability in response-recovery profiles of milk metabolites that have strong links with body energy dynamics (i.e., isoCitrate, ß-hydroxybutyrate, choline, cholesterol, and triacylglycerols; R2 = 35%). Our results suggested that prekidding energy status and MY are key determinants of adult resilience and that rearing diet and genetic line may affect adult resilience insofar as they affect the animals' energy status.

Kick-starting ovarian cyclicity by using dietary glucogenic precursors in post-partum dairy cows: a review

The objective of this review is to describe how dietary glucogenic precursors could stimulate ovarian activity in post-partum dairy cows and improve reproductive success. Although the nutrient requirements for the early resumption of ovarian cycles, and for follicle and embryo development are quantitatively small, reproductive success is deteriorated by post-partum negative energy balance. Since very little glucose is absorbed directly from the digestive tract of ruminants one of the targets for nutritional manipulation could be the glucogenic potential of the diet. This could be achieved by giving rumen-resistant starch or mono-propylene glycol. Both these adaptations increase glucose, insulin and insulin-like growth factor-1 plasma concentrations and stimulate ovarian follicle growth.

Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Dietary supplementation with propylene glycol (PG) increases in vitro production of high-quality embryos in feed-restricted heifers. The aim of the present study was to evaluate the effects of PG in feed-restricted heifers on follicular fluid insulin and insulin-like growth factor (IGF) 1 concentrations, expression of IGF system genes in oocytes and cumulus cells and the expression of selected genes in blastocysts. Feed-restricted (R) heifers were drenched with water or PG during induced oestrous cycles (400mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle). Ovum pick-up (OPU) was performed after superovulation to produce in vitro embryos and without superovulation to recover oocytes, cumulus cells and follicular fluid. OPU was also performed in a control group (not feed restricted and no drenching). Follicular fluid IGF1 concentrations were reduced by R, and PG restored IGF1 concentrations to those seen in the control group. In cumulus cells, expression of IGF1, IGF1 receptor (IGF1R) and IGF binding protein 4 (IGFBP4) was decreased in the R group, and fully (IGF1 and IGF1R) or partially (IGFBP4) restored to control levels by PG. Blastocyst perilipin 2 (PLIN2; also known as adipophilin), Bcl-2-associated X protein (BAX), SCL2A1 (facilitated glucose/fructose transporter GLUT1), aquaporin 3 (AQP3), DNA (cytosine-5)-methyltransferase 3A (DNMT3A) and heat shock 70-kDa protein 9 (HSPA9B) expression were decreased in R heifers; PG restored the expression of the last four genes to control levels. In conclusion, these results suggest that, during follicular growth, PG exerts epigenetic regulatory effects on gene expression in blastocyst stage embryos.

Dietary propylene glycol and in vitro embryo production after ovum pick-up in heifers with different anti-Müllerian hormone profiles

Rapid genetic improvement in cattle requires the production of high numbers of embryos of excellent quality. Increasing circulating insulin and/or glucose concentrations improves ovarian follicular growth, which may improve the response to superovulation. The measurement of anti-Müllerian hormone (AMH) can help predict an animal's response to superovulation treatment. The aim of the present study was to investigate whether increasing circulating insulin concentrations, through propylene glycol (PG) drenches, could improve in vitro embryo production in oestrus-synchronised superovulated heifers with different AMH profiles. Holstein heifers were grouped according to pre-experimental AMH concentrations as low (L) or high (H). The PG drench increased circulating insulin and glucose concentrations and reduced β-hydroxybutyrate and urea concentrations compared with the control group. AMH was a good predictor of follicle and oocyte numbers at ovum pick-up (OPU), and of oocyte and embryo quality (AMH H>AMH L). PG in the AMH H group increased the number of follicles and blastocyst quality above that in the control group, but did not improve these parameters in the AMH L group. These results indicate that short-term oral PG supplementation modifies an animal's metabolic milieu and is effective in improving in vitro embryo production, after superovulation-OPU, more markedly in heifers with high rather than low AMH concentrations.

231 EFFECTS OF DIETARY PROPYLENE GLYCOL ON FOLLICULAR FLUID AND OVUM PICK UP IN VITRO EMBRYO PRODUCTION IN GROWTH-RESTRICTED HEIFERS WITH TWO PROFILES OF ANTI-MÜLLERIAN HORMONE

Fertility and embryo quality can be improved in cattle by using diets that induce a programmed modulation of circulating insulin concentrations. The aim of this study was to test whether the daily oral administration of propylene glycol (PG) could modify metabolite and hormone plasma and follicular fluid concentrations and improve in vitro embryo production in superovulated growth-restricted heifers (600 g day–1). Sixteen Holstein heifers were grouped according to their pre-experimental anti-Müllerian hormone (AMH) plasma concentrations: low (L = 1–80 pg mL–1; n = 7) or high (H: >150 pg mL–1; n = 9). Heifers received a single daily drench from Day 1 to Day 9 of an oestrous cycle [first cycle, 400 mL of water (control) and second cycle, 400 mL of PG]. Serial jugular blood samples were collected on Day 7 of each cycle to monitor plasma insulin, glucose, and β-hydroxybutyrate (BHB) concentrations in relation to the drench. Blood samples were also collected to measure insulin-like growth factor-1 (IGF1) and progesterone (P4) concentrations on Days 0, 2, 5, 7, and 9 of the oestrous cycle. Follicular fluid was collected on Day 9 to measure insulin and IGF1 concentrations. Ovarian ultrasonography was performed on Days 2 and 5 to count follicles between 2 and 8 mm in diameter and estimate their size. After ovum pickup (OPU) performed following superovulation on Day 5 of the oestrous cycle, oocytes were matured and fertilized in vitro, then embryos were cultured for 7 days. Propylene glycol increased plasma concentrations of insulin and glucose and reduced BHB in both groups of heifers compared with control. It also increased IGF1 concentrations on Days 5 and 7 in AMH L heifers and on Days 2, 5, and 7 in AMH H heifers, and reduced P4 concentrations on Days 5 and 9 of the oestrous cycle in all heifers. In follicular fluid, there was no difference in insulin concentrations between groups, but PG increased IGF1 concentrations in all heifers. In ovaries, PG increased the number of small follicles (2–3 mm) and total follicles on Day 2 of the cycle in all heifers, and medium follicles (4–8 mm) and total follicles on Day 5 in AMH H heifers. Propylene glycol improved the in vitro embryo development rate (total number of embryos/number of fertilized oocytes) in all heifers (AMH L: control, 37.9% v. PG, 50.0%; P < 0.05; AMH H: control, 36.4% v. PG, 48.3%; P < 0.05). In AMH H, the number of grade 1 blastocysts was increased by PG (control, 5.2 ± 1.0 v. PG, 8.9 ± 1.0; P < 0.01), whereas there was no difference between treatments in AMH L heifers (control, 1.9 ± 1.1 v. PG, 3.2 ± 1.1; P > 0.05). These results indicate that short-term oral PG supplementation affects the concentrations of metabolites and metabolic hormones in blood and IGF1 concentrations in follicular fluid. PG administration is effective in improving in vitro embryo production more markedly in heifers with high AMH compared with low AMH endocrine levels.

5 PROPYLENE GLYCOL FEEDING SUPPLEMENTATION MODIFIES INSULIN-LIKE GROWTH FACTOR SYSTEM GENE EXPRESSION IN CUMULUS–OOCYTE COMPLEXES AND THE EXPRESSION OF SELECTED CANDIDATE GENES IN EMBRYOS PRODUCED IN VITRO IN FEED-RESTRICTED HEIFERS

Dietary supplementation with propylene glycol (PG) increases the rate of grade 1 embryos produced from feed restricted females (Gamarra et al. 2014 Reprod. Fertil. Dev.). The aim of this study was to evaluate if a PG feeding supplement could modify the expression profile of selected candidate genes that are important for in vitro embryo development and the gene expression patterns of the insulin-like growth factor (IGF) system in oocytes and cumulus cells in feed-restricted heifers. Feed-restricted heifers (n = 16, growth rate of 600 g day–1) received a single daily drench of 400 mL of water (group restricted, R) from Day 1 to Day 9 of a first synchronized oestrous cycle followed by 400 mL of PG from Day 1 to Day 9 of the second synchronized oestrous cycle (group restricted + PG, RPG). Ovum pick-up (OPU) was performed following superovulation, on Day 5 of the oestrous cycle to produce embryos in vitro and on Day 9 without superovulation to obtain oocytes and cumulus cells. The same protocol was used in control animals (n = 6, growth rate of 800 g day–1). Real-time PCR was used to determine the relative abundance of genes involved in lipid metabolism and storage (PLIN2, SCD), energy metabolism (ATP5A1, GLUT1), membrane permeability (AQP3), epigenetic marks (DNMT3a), apoptosis (BAX, TP53), and protein processing (HSPA9B) in grade 1 blastocysts, IGF1, IGF1R, IGFBP2, IGFBP4 in cumulus cells, and IGF1R and IGFBP2 in oocytes. Mann-Whitney nonparametric tests were performed to analyse gene expression results. The expression of PLIN2, ATP5A1, GLUT1, AQP3, DNMT3a, BAX, and HSPA9B were decreased in embryos collected from restricted compared with control animals. The expression levels of these genes were restored when females were supplemented with PG. The expression of TP53 and SCD were not affected. In cumulus cells, the expression levels of IGF1, IGF1R, and IGFBP4 were decreased in restricted compared with control animals. The expression levels of IGF1 and IGF1R were restored with PG supplementation. No differences were observed for the IGFBP2 gene. In the oocytes, no differences were observed for the expression levels of IGF1R and IGFBP2 genes. In conclusion, this work shows for the first time that feed restriction and dietary supplementation by PG in heifers produced changes in gene expression in blastocysts and modified the pattern of the IGF system in cumulus cells. These results suggest the existence of an epigenetic regulation induced by PG during follicular growth, which can regulate the level of gene expression up to the blastocyst stage. In general, PG supplementation of feed-restricted donors restored gene expression at the levels observed after normal feeding.

Energy and lipid metabolism gene expression of D18 embryos in dairy cows is related to dam physiological status

We analyzed the change in gene expression related to dam physiological status in day (D)18 embryos from growing heifers (GH), early lactating cows (ELC), and late lactating cows (LLC). Dam energy metabolism was characterized by measurement of circulating concentrations of insulin, glucose, IGF-1, nonesterified fatty acids, β-hydroxybutyrate, and urea before embryo flush. The metabolic parameters were related to differential gene expression in the extraembryonic tissues by correlation analysis. Embryo development estimated by measuring the length of the conceptuses and the proportion of expected D18 gastrulating stages was not different between the three groups of females. However, embryo metabolism was greatly affected by dam physiological status when we compared GH with ELC and GH with LLC but to a lesser extent when ELC was compared with LLC. Genes involved in glucose, pyruvate, and acetate utilization were upregulated in GH vs. ELC conceptuses (e.g., SLC2A1, PC, ACSS2, ACSS3). This was also true for the pentose pathway ( PGD, TKT), which is involved in synthesis of ribose precursors of RNA and DNA. The pathways involved in lipid synthesis were also upregulated in GH vs. ELC. Despite similar morphological development, the molecular characteristics of the heifers' embryos were consistently different from those of the cows. Most of these differences were strongly related to metabolic/hormone patterns before insemination and during conceptus free-life. Many biosynthetic pathways appeared to be more active in heifer embryos than in cow embryos, and consequently they seemed to be healthier, and this may be more conducive to continue development.

Medium-term effects of repeated exposure to stray voltage on activity, stress physiology, and milk production and composition in dairy cows

The medium-term effects of permanent or random exposure to stray voltage applied to the water trough were evaluated on milk production and stress physiology in lactating dairy cows. Seventy-four Holstein cows were assigned during two 8-wk experimental periods to 1 of 3 treatments. The treatments were permanent exposure to voltage (PERM, 1.8 V, n=23) applied to the water trough, random exposure to voltage (RAND, 1.8 V, 36 h/wk, n=25), and no exposure to voltage (control, n=26). On the first day of voltage exposure, PERM cows had higher activity levels than control cows (9.8+/-2.70 vs. -2.3+/-2.74 14-s periods of movement/h). During the eighth week of exposure, RAND cows had higher activity levels than control cows (4.2+/-3.64 vs. -7.7+/-3.54 14-s periods of movement/h) and higher milk cortisol concentration than PERM cows (0.21+/-0.024 vs. 0.14+/-0.020 ng/mL). No differences were observed between treatments for cortisol response after an ACTH challenge during the seventh week of exposure. No effects of voltage exposure were observed on production traits and daily water intake. There was a transient decrease in milk yield on the second day of exposure in PERM cows (-1.4+/-0.74 kg) and on the third day of exposure in RAND cows (-3.5+/-1.03 kg) compared with control cows. In dairy cows, permanent or random exposure to stray voltage (1.8 V; 3.6 mA) could induce a transient stress response. Moreover, unpredictable voltage exposure could be considered a mild stressor, with slight modifications in stress physiology and activity but no impairment in production in the medium term.

Hyperlipidic hypercholesterolemic diet in prepubertal rabbits affects gene expression in the embryo, restricts fetal growth and increases offspring susceptibility to obesity

Maternal hypercholesterolemia has been shown to lead to fetal intra-uterine growth retardation (IUGR) in rabbits. The effects of a long term maternal hyperlipidemic and hypercholesterolemic diet on embryo, fetal and post-natal development, have not been addressed so far. Rabbit does were fed either a hypercholesterolemic (0.2%) hyperlipidic (8%) (HH) or a control (C) diet from 10 weeks of age. Sixteen does (N = 8 HH and N = 8 C) were euthanized at 18 weeks to assess the effect of the diet on dams before mating. Embryos from 18 females (N = 9 HH and N = 9 C) were collected from the oviducts at the 16-20 cell stage (embryonic genome activation stage) for gene expression analysis (micro array and quantitative RT-PCR). Thirty females (N = 16 HH and N = 14 C) were mated naturally and fetal growth was monitored by ultrasound. Six of them (N = 4 HH and N = 2 C) were euthanized at D28 of gestation to collect fetuses and placentas. Finally, the remaining 24 does delivered at term and litters were cross fostered and equilibrated in number to create 4 groups according to the biological dam and the foster dam (C-C, C-HH, HH-C, HH-HH). Growth was monitored until weaning. A subset of 26 offspring from the 4 groups was fed the control diet until 25 weeks of age and then fed the HH diet for three weeks. All does had similar growth rates and bodyweight. Transcriptomic analyses evidenced an overexpression of Adipophilin in HH embryos at the stage of embryonic genome activation. This was confirmed by quantitative RT-PCR. During pregnancy, IUGR was observed from D9 by ultrasound and subsequently, fetal weight at 28 days, birthweight and fat deposition in newborn offspring were significantly decreased in HH (P < 0.05). After weaning, there was no significant difference for weight between HH-HH and HH-C offspring and both groups became significantly heavier (P < 0.0001) than C-C and C-HH offspring. During the 3 weeks when offspring were fed the HH diet, the differences in feed intake were no longer significant between groups but the differences in body weight remained. At post-mortem, offspring from HH does had significantly more abdominal and inter-scapular fat than offspring from C does (P < 0.05). These data illustrate the importance of maternal nutrition before and during gestation in the establishment and control of the growth trajectory of the conceptus and in the onset of disease in adult life.

255 EFFECT OF THE TYPE OF DIETARY FATTY ACID (α-LINOLENIC ACID OR LINOLEIC ACID) ON THE NUMBER AND THE QUALITY OF OOCYTES COLLECTED BY OVUM PICKUP AND ON IN VITRO EMBRYO PRODUCTION BY DAIRY HEIFERS

A supplement of dietary fat can improve oocyte quality in ruminants. However, to our knowledge, the effect of the type dietary fat (differing in fatty acid profile) on oocyte and embryo production has never been reported in cattle. Therefore, in this study the effect of the type of fat supplement on the number and quality of oocytes collected by ovum pickup (OPU) and on the production of embryos was investigated in Holstein heifers. The experiment was conducted over 2 years: year 1: 8 heifers, and year 2: 10 heifers (16 to 20 months old, body weight 368 � 8.2 kg and BCS 2.3 � 0.1). Heifers were given a diet of hay (67% DM) and a concentrate (33% DM). The concentrate (130 g fat/kg DM) was formulated with either extruded linseeds (L, rich in α-linolenic acid (ω-3 fatty acid),n = 9) or extruded soybeans (S, rich in linoleic acid (ω-6 fatty acid), n = 9). Oocytes were collected by OPU for 6 weeks (2 sessions/week) and their morphological quality was assessed (Q1, excellent; Q2, good; Q3, fair; and Q4, low). The oocytes from one session/week were frozen and those from the other session were used to produce embryos (in vitro maturation and fertilization). Embryo quality was judged following IETS criteria (EQ1, excellent; EQ2, good; EQ3, fair; and EQ4, low). Blood samples were collected weekly throughout the experiment for the analysis of insulin, insulin-like growth factor-1, glucose, non-esterified fatty acids, β-hydroxybutyrate, and urea. Statistical analysis was performed on the growth rate, BCS, hormone, metabolite, and fatty acid data and on the oocyte and embryo data using Split plot ANOVA. Growth rate was not affected by diet (S, 0.93 � 0.21 kg d-1 vs. L, 0.90 � 0.21 kg d-1), and there was no effect of dietary treatment on plasma hormone and metabolite concentrations. However, treatment L increased the proportion of α-linolenic acid (P &lt; 0.0001), and treatment S increased the proportion of linoleic acid (P &lt; 0.0001) in the plasma. Neither the oocyte characteristics (number of oocytes collected, 5.3 � 1.0 vs. 5.7 � 1.0; their quality: Q1, 1.1 � 0.3 vs. 1.0 � 0.3; Q2, 1.8 � 0.3 vs. 1.6 � 0.3; Q3, 1.4 � 0.4 vs. 2.1 � 0.4; and Q4, 1.0 � 0.2 vs. 1.1 � 0.2; and oocytes inseminated, 4.4 � 0.8 vs. 5.1 � 0.8, and cleaved, 3.4 � 0.7 vs. 3.5 � 0.7 per heifer per session; L vs. S, respectively) nor the embryo characteristics (number of embryos, 1.1 � 0.3 vs. 0.9 � 0.3; their quality: EQ1, 0.4 � 0.1 vs. 0.3 � 0.1; EQ2, 0.4 � 0.1 vs. 0.3 � 0.1; EQ3, 0.2 � 0.1 vs. 0.3 � 0.1; and EQ4, 0.04 � 0.03 vs. 0.05 � 0.03 per heifer per session; L vs. S, respectively) were affected by dietary treatment. In conclusion, under our experimental conditions, the type of fatty acid (ω-3 vs. ω-6) does not modify significantly the numbers of oocytes and embryos produced by OPU and their quality in dairy eifers.

Reduction of body-weight gain enhances in vitro embryo production in overfed superovulated dairy heifers

The aim of our study was to test whether a reduction in dietary intake could improvein vitroembryo production in superovulated overfed dairy heifers. Cumulus–oocyte complexes of 16 Prim’ Holstein heifers (14 ± 1 months old) were collected by ovum pick-up (OPU), every 2 weeks following superovulation treatment with 250 μg FSH, before being matured and fertilizedin vitro. Embryos were cultured in Synthetic Oviduct Fluid medium for 7 days. Heifers were fed with hay, soybean meal, barley, minerals and vitamins. From OPU 1 to 4 (period 1), all heifers received individually for 8 weeks a diet formulated for a 1000 g/day live-weight gain. From OPU 5 to 8 (period 2), the heifers were allocated to one of two diets (1000 or 600 g/day) for 8 weeks. Heifers’ growth rates were monitored and plasma concentrations of metabolites, metabolic and reproductive hormones were measured each week. Mean live-weight gain observed during period 1 was 950 ± 80 g/day (n= 16). In period 2 it was 730 ± 70 (n= 8) and 1300 ± 70 g/day (n= 8) for restricted and overfed groups respectively. When comparing period 1 and period 2 within groups, significant differences were found. In the restricted group, a higher blastocyst rate, greater proportions of grade 1–3 and grade 1 embryos, associated with higher estradiol at OPU and lower glucose and β-hydroxybutyrate, were observed in period 2 compared with period 1. Moreover, after 6 weeks of dietary restriction (OPU 7), numbers of day 7 total embryos, blastocysts and grade 1–3 embryos had significantly increased. On the contrary, in the overfed group, we observed more <8 mm follicles 2 days before superovulation treatment, higher insulin and IGF-I and lower nonesterified fatty acids in period 2 compared with period 1 (no significant difference between periods for embryo production). After 6 weeks of 1300 g/day live-weight gain (OPU 7), embryo production began to decrease. Whatever the group, oocyte collection did not differ between period 1 and 2. These data suggest that following a period of overfeeding, a short-term dietary intake restriction (6 weeks in our study) may improve blastocyst production and embryo quality when they are low. However, nutritional recommendations aiming to optimize both follicular growth and embryonic development may be different.

Ultrasound fetal measurements and pregnancy associated glycoprotein secretion in early pregnancy in cattle recipients carrying somatic clones

Somatic cloning in the bovine species leads to high levels of fetal losses which occur throughout pregnancy. These losses are most often associated with fetal overgrowth, a syndrome known as large offspring syndrome (LOS), and excessive maternal plasma pregnancy serum protein 60 (PSP60), a protein similar to a pregnancy-associated glycoprotein of 67 kDa (PAG I67) produced by the bovine placenta. Predicting the outcome of pregnancies initiated from cloned embryos has become an important issue both to prevent potential harm to the mother because of excessive fetal size at birth and also to get a better understanding of the relationships between growth, differentiation and placental functions in developing cloned fetuses. Here, we report on a systematic analysis of fetal and placental development in the first trimester of pregnancy performed by ultrasonographic imaging and by measurement of the maternal concentrations of pregnancy associated glycoproteins (PAGS), using four different radioimmunoassays (RIA) (two homologous RIA systems with PSP60 and PAG I67; two heterologous RIA systems with PAG I67 as standard and tracer, and antisera anti-caprine PAGs). We showed that crown-rump length (CRL) in clones appeared smaller than controls at 35, 50 and 62 days (P<0.05). At 62 days of pregnancy, CRL in cloned fetuses that died before 90 days was smaller compared to the other cloned fetuses (P<0.05) whereas the width of the fetal sack and the biparietal diameter (BPD) was larger in fetuses that developed LOS in late gestation (P<0.05). Maternal PAGs concentrations were statistically different between controls and all clone recipients as early as Day 34, suggesting early abnormal placental glycoprotein synthesis for clone pregnancies regardless of pregnancy outcome. This work provides a practical, non-invasive tool to follow up clone pregnancies and suggests that primary growth retardation and abnormal placental function precedes excessive fetal and placental growth at later stages of pregnancy.

Estrus synchronization in beef cows: comparison between GnRH+PGF2alpha+GnRH and PRID+PGF2alpha+eCG

The aim of this study was to compare two protocols for estrus synchronization in suckled beef cows over a 2 years period. The population studied consisted of 172 Charolais and 168 Limousin cows from 12 and 14 beef herds, respectively. In each herd, cows were allotted to groups according to parity, body condition score and calving difficulty. Cows in Group 1 (n=174) received PRID on Day-8 with estradiol benzoate (10mg, vaginal capsule), dinoprost on Day-4 (25mg i.m.), eCG on Day 2 (500 IU i.m.). The PRID was removed on Day-2 and cows were inseminated on Day 0, 56 h after PRID was removed. Cows in Group 2 (n=166) received GnRH on Day-10 (100 microg i.m.), dinoprost on Day-3 (25mg i.m.) and GnRH on Day-1 (100 microg i.m.), and were inseminated on Day 0, 16-24h after the last GnRH treatment. Plasma progesterone concentrations were measured to determine cyclicity prior to treatment (Days-20 and -10), to confirm the occurrence of ovulation (Days 0 and 10) and to determine the apparent early pregnancy rate (Days 0, 10 and 24). Pregnancy diagnosis was performed by ultrasonography between Days 35 and 45. The effects of various factors on ovulation, apparent early pregnancy and pregnancy rates were studied using logistic mixed models. There was no significant difference between Groups 1 and 2, respectively, for the cyclicity rate before treatment (80.5% versus 80.1%), for apparent pregnancy rate on Day 24 (62.1% versus 54.8%, P=0.09) and for pregnancy rate on Days 35-45 (53.8% versus 46.3%, P=0.16). Ovulation rate was higher (P<0.01) in Group 1 (90.8%) than in Group 2 (77.1%) and was affected by cyclicity prior to treatment in Group 2 but not in Group 1 (Group 1: 88.2% in anestrous cows versus 91.4% in cyclic cows; Group 2: 45.5% in anestrous cows versus 85.0% in cyclic cows, P interaction=0.05). Apparent pregnancy rates on Day 24 were influenced by the year of study (52.4% versus 68.8%, OR=2.12, P<0.01) and by the cyclicity before treatment (anestrous cows 46.3% versus cyclic cows 61.5%, OR=1.86, P<0.05). Pregnancy rates at 35-45 days were influenced by the year of study (44.2% versus 59.8%, OR=1.92, P<0.01). In conclusion, although pregnancy rates were similar for the two treatments, the combination of GnRH+PGF2alpha+GnRH in suckled beef cows induced a lower rate of ovulation than treatment with PRID+PGF2alpha, particularly in anestrous cows.

Influence of the type of energy supply on lh secretion, follicular growth and response to estrus synchronization treatment in feed-restricted suckler beef cows

The present experiment aimed to compare the efficiency of supplementation (+17.5 MJ Net Energy/d starting 47 +/- 4 days after calving) with concentrate (CS, maize grain, n = 10) or with forage (FS, maize silage, n = 10) in estrus-synchronized (Norgestomet implant 10 days inserted 60 +/- 4 days postpartum + PMSG at implant removal) beef cows previously restricted (47 MJ Net Energy/d, 785 g CP/d, 70% of requirements). The type of diet had no significant effect on basal LH concentrations (CS: 0.18 +/- 0.12 vs FS: 0.11+/- 0.02 ng/mL), LH pulse frequency (CS : 0.7 +/- 0.3 vs FS: 0.8 +/- 0.2 pulse/10 h), LH pulse amplitude (CS: 0.55 +/- 0.50 vs FS : 0.62 +/- 0.50 ng/mL) or estradiol (E2) concentrations (CS: 3.3 +/- 0.8 vs FS: 4.6+ /- 0.8 pg/mL) 13 days after the beginning of energy supplementation. No differences between CS and FS cows were observed for the number of small, medium and large follicles nor on the size of the largest follicle from 11 days before implant insertion to implant removal (IR). After IR, an LH surge was observed in 2 of the CS and 4 of the FS cows. The type of energy supplementation had no significant effect on LH (CS: 0.16 +/- 0.06 ng/mL vs FS 0.48 +/- 0.06 ng/mL; P > 0.05) or on estradiol concentrations (CS : 7.8 +/- 0.2 vs FS : 8.9 +/- 0.2 pg/mL, P > 0.10) measured hourly from 29 to 49 h after IR. Cows that ovulated after IR tended to have higher E2 concentrations than cows that did not ovulate (9.4 +/- 0.2 vs 6.3 +/- 0.2 pg/mL, P = 0.08). Similar ovulation and pregnancy rates were observed in CS and FS cows (CS: 6/10 vs FS: 7/10 and CS: 6/10 vs FS: 5/10 respectively, P > 0.05). To conclude, energy supplementation with forage was as effective as energy supplementation with concentrate to influence follicular growth, ovulation and pregnancy percentage after estrus synchronization treatment in diet-restricted beef cows.

Postpartum subestrus in dairy cows: comparison of treatment with prostaglandin F2 alpha or GnRH + prostaglandin F2 alpha + GnRH

Two experiments (Experiment 1, 185 cows in 1996/97; Experiment 2, 168 cows in 1997/98) were conducted with Prim Holstein dairy cattle in the Mayenne region of France to investigate subestrus. Cows which had not been observed in estrus since calving were allocated alternately to treatment groups between 60 and 90 d post partum as follows: Experiment 1-Group 1: GnRH (Day 0, 100 micrograms i.m.), PGF2 alpha (Day 7, 25 mg i.m.), GnRH (Day 9, 100 micrograms i.m.) and AI (Day 10); Group 2: PGF2 alpha (Day 0, 25 mg i.m.), AI at estrus, or, if estrus was not observed, a second PGF2 alpha injection on Day 13, and AI on Day 16 and Day 17. Treatments in Experiment 2 were as follows: Group 1: as Experiment 1-Group 1 but AI at the observed estrus after Day 0, or at Day 10 if estrus was not observed; Group 2: as Experiment 1--Group 2, however, if a second PGF2 alpha injection was given on Day 13, AI at the observed estrus. Progesterone was measured in serum at Day 0 and in milk at AI. Pregnancy diagnosis was performed by measuring bovine pregnancy-specific protein B (bPSPB; Day 50 +/- 3) and confirmed by ultrasonography when the result was doubtful. In Experiment 1, farmers observed 47/101 (46.9%) Group 1 cows in estrus, 33/91 cows on Day 10 and 10 cows before Day 10. The progesterone concentrations were compatible with estrus in 69/86 (80%) cows on Day 10. In Group 2, 36/83 (43.4%) cows were inseminated after the first PGF2 alpha injection. After the second PGF2 alpha injection, only 29/43 (67%) cows had a low progesterone concentration at AI. Pregnancy rates were 36.1 and 32.5% for Groups 1 and 2, respectively. In Experiment 2, estrus was observed in 31/93 (33.7%) Group 1 cows. In Group 2, 51/75 (66%) cows were inseminated after the first injection of PGF2 alpha, 13/75 (17.3%) cows after the second injection, while 11/75 (14.7%) were not observed in estrus. Pregnancy rates were 53.7 and 53.3% in Groups 1 and 2, respectively. In conclusion, it is recommended that subestrus be treated with PGF2 alpha followed by AI at the observed estrus when estrus detection is good, while the use of GnRH + PGF2 alpha + GnRH is recommended when estrus detection is poor.

Influence of flushing on LH secretion, follicular growth and the response to estrus synchronization treatment in suckled beef cows

The effects of energy supplementation (flushing) on LH and estradiol secretion, follicular growth and the response to estrus synchronization treatment (Norgestomet + PMSG initiated 41.9 +/- 3.4 d after calving) were investigated in 16 suckled beef cows fed either 70% (Group C, n = 8) of energy requirements from calving to 3 wk after AI or fed the same restricted diet until 11 d before synchronization and then were supplemented with 2 kg concentrate until 3 wk after AI (Group S, n = 8). Concentrations of LH and estradiol 17 beta were measured from 3 sampling periods: 25 and 39 d after calving and between 29 and 49 h after implant removal. Ovaries were examined by ultrasonography 11 d before treatment to implant withdrawal (IR). The effects of energy level, day (or hour) of observation and corresponding interactions were tested on repeated measurements by split-plot ANOVA. No positive effect of flushing was observed on characteristics of LH secretion on Day 39. However, the size of the largest follicle and the number of large follicles were higher in Group S than in Group C cows, respectively, 7 and 9 d after the beginning of flushing to 2 d after the start of treatment. After IR, the estradiol secretion tended to be higher in Group S than in Group C cows (9.8 +/- 0.4 pg/mL vs 7.2 +/- 0.2 pg/mL; P = 0.06), but no effect on LH secretion was observed. After implant removal 12 cows ovulated (Group S: 7/8 vs Group C: 5/8; P > 0.05), 7 were pregnant at 21 d after AI (Group S: 6/8 vs Group C: 1/8; P < 0.05) and 4 at 45 d after AI (Group S: 4/8 vs Group C 0/8; P > 0.05). To conclude, flushing had a positive effect on follicular growth, which does not seem to be mediated by LH. In cows fed a restricted diet, flushing enhanced follicular growth, increased the fertilization rate and/or reduced early embryonic death.

Effects of chronic parenteral pyridoxine and acute enteric tryptophan on pyridoxine status, glycemia and insulinemia stimulated by enteric glucose in weanling piglets

In order to investigate the importance of the relation between pyridoxine and tryptophan on glucose tolerance and insulin response to glucose, 12 Large White × Pietrain piglets (males and females), weaned at 3 wk of age, were allocated to two treatment groups. Within each of the six pairs (four females and two males), one piglet received daily 3 mL i.m. of pyridoxine.HCl (5 g L−1) and the other received a control injection of saline. The animals were fed a liquid feed through a gastric tube surgically inserted on the day of weaning. Seven days later, one catheter was placed in the duodenum and another in the jugular vein. One week after recovery, the piglets received an intraduodenal infusion of glucose or glucose + tryptophan; 2 d later, each piglet received the opposite treatment. There was no effect (P > 0.18) of the administration of pyridoxine.HCl on plasma pyridoxal and pyridoxal-5-phosphate. Whatever the pyridoxine treatment, the plasma glucose response was lower (P ≤ 0.05) after the glucose + tryptophan infusion than after the glucose infusion. There was, also, an interaction between parenteral pyridoxine and duodenal infusion on changes in plasma insulin concentrations following the duodenal infusion (P ≤ 0.02). The greatest response, observed in piglets supplemented with pyridoxine.HCl and infused with glucose, was 55% higher than for the three other treatments. Further work is needed for an eventual reliable estimate of the pyridoxine status and requirements of weanling piglets. The tryptophan and pyridoxine effects on insulin metabolism suggest a different action of these nutrients on sensitivity and release of insulin. Key words: Pyridoxine, tryptophan, glucose, insulin, weanling piglets

Influence of postpartum energy restriction on energy status, plasma LH and oestradiol secretion and follicular development in suckled beef cows

Effects of postpartum energy restriction, parity and time after parturition on energy status (measured by glucose, insulin, non-esterified fatty acids (NEFAs) and beta-hydroxybutyrate), LH secretion and follicular growth were investigated in ten primiparous and nine multiparous suckled cows. Females were allocated by parity, body mass and body condition score at calving to diets supplying either 100% (CE, n = 10) or 70% (LE, n = 9) of energy requirements until day 70 postpartum. Metabolic parameters were measured every week from calving to day 70 postpartum. Blood samples were collected at intervals of 15 min for 10 h on day 30 and day 50 after parturition for LH measurement. Ovaries were examined between days 20 and 30 and days 40 and 50 postpartum by ultrasonography. Energy supply affected mean plasma concentrations of glucose (CE: 0.64 +/- 0.01 g l-1 versus LE: 0.61 +/- 0.01 g l-1; P < 0.05) and NEFA (CE: 168 +/- 17 mu eq l-1 versus LE: 309 +/- 18 mu eq l-1; P < 0.01) but by day 70 postpartum, glucose and NEFA concentrations were not significantly different between the two groups. LH pulse amplitude and frequency were not affected by energy supply (P > 0.10). However, at day 30 postpartum, LH pulse frequency was negatively correlated with plasma concentration of NEFA (r = -0.61; P < 0.01). Cows fed diets supplying 100% of energy requirements had more large follicles than did cows fed low energy diets (CE: 0.82 +/- 0.05 versus LE: 0.31 +/- 0.05; P < 0.05). The size of the largest follicle was greater in CE cows than in LE cows (CE: 10.2 +/- 0.1 mm versus LE: 8.7 +/- 0.2 mm; P < 0.05). Between 40 and 50 days postpartum, the size of the largest follicle was negatively correlated with NEFA concentration (r = -0.5; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of energy source and tryptophan on the rate of protein synthesis and on hormones of the entero-insular axis in the piglet

The present experiment was designed to study the influence of dietary energy source (fat or carbohydrate) and tryptophan (TRP) on protein synthesis and plasma insulin concentrations in the piglet. Six dietary regimens, based on either a high-fat (F) or a high-carbohydrate (C) diet with three levels of TRP (deficient, 1; adequate, 2; excess, 3), were used. Fractional protein synthesis rate (ks; % per d) was measured in the liver, Longissimus dorsi (LD), Semitendinosus (ST), skin, femur, brain, pancreas, stomach, mucosa of the duodenum and jejunum, and the whole body, using a 'flooding dose' of 3H-phenylalanine. Mean integrated insulin, gastric inhibitory polypeptide (GIP) and glucose concentrations were higher after the C diets compared with the F diets, TRP supplementation globally augmented ks linearly in the liver, ST, skin and whole body, while it had quadratic effects in the LD (ks highest in the TRP-adequate diet groups) and jejunal mucosa (ks lowest in the TRP-adequate diet groups). Pancreatic ks was increased by TRP addition up to a plateau. Ks was highest after the F diets in the digestive tissues while in the skin and LD ks was highest after the C diets. Fasting concentrations of gluconeogenic amino acids were lower (and urea higher) with the F than the C diets, suggesting their use as precursors for glucose synthesis. In conclusion, we have confirmed the depressive effects of TRP deficiency on ks, RNA activity and growth. We could not establish a relationship between plasma insulin and muscle ks. This may be related to the way in which we manipulated plasma insulin concentrations.

Intragastric tryptophan reduces glycemia after glucose, possibly via glucose-mediated insulinotropic polypeptide, in early-weaned piglets

The aim of this experiment was to investigate the influence of oral tryptophan on insulin, glucose-mediated insulinotropic polypeptide and glucose concentrations in early-weaned piglets. Piglets were given by intragastric infusion, at the same level of feeding, either a tryptophan-deficient or tryptophan-adequate diet for 22 d. During the experiment blood samples were taken after intragastric infusion of 1) the accustomed meal, 2) a glucose plus tryptophan load and 3) a glucose load. Plasma samples were analyzed for insulin, glucose-mediated insulinotropic polypeptide, glucose and lactate. After the accustomed meal plasma insulin concentrations were augmented and liquid gastric emptying faster in pigs fed tryptophan-adequate compared with tryptophan-deficient diets (P < 0.05) but glucose-mediated insulinotropic polypeptide, glucose and lactate were unaffected. The addition of tryptophan to a glucose load increased glucose-mediated insulinotropic polypeptide and reduced glucose in both tryptophan-adequate and tryptophan-deficient diet fed pigs (P < 0.05). Piglets adapted to the tryptophan-adequate diet had a greater glucose-mediated insulinotropic polypeptide response to intragastric glucose plus tryptophan than piglets adapted to the tryptophan-deficient diet. Adaptation to a tryptophan-adequate diet seems to increase the release of glucose-mediated insulinotropic polypeptide due to infusion of a tryptophan-adequate compared with a tryptophan-deficient diet. The addition of tryptophan to a glucose load reduces the level of glycemia, possibly through glucose-mediated insulinotropic polypeptide-mediated glucose disposal.

The effect of energy source and feeding level on the hormones of the entero-insular axis and plasma glucose in the growing pig

The aim of the experiment was to test the theory that accustoming pigs to a high-fat diet causes exaggerated gastric inhibitory polypeptide (GIP) secretion in response to a high-fat meal, and to determine whether hypersecretion of GIP could be related to an increase in the GIP content of the small intestine. Twenty-four pigs were fed one of three dietary regimens for 11 weeks: a high-carbohydrate diet (CL), or a high-fat diet (FL), both fed at 1.46 MJ gross energy (GE)/kg live weight0.75 per d, or a high-fat diet (FH) fed at 2.10 MJ GE/kg live weight0.75 per d. At the end of the period two acute tests were performed. For acute test 1 the accustomed meal (diets CL, FL and FH) and for acute test 2 a standard high-fat meal (diet FL) were given; blood samples were taken during the next 5 h and analysed for GIP, insulin and glucose. Integrated increases in hormone and glucose levels were compared by analysis of variance (0-300 min). In acute test 1 there were significantly different plasma GIP concentrations between groups (CL greater than FH greater than FL; P less than 0.05). Plasma insulin concentrations were significantly higher in group CL compared with groups FL and FH (P less than 0.002). There were no differences in glucose levels. In acute test 2 integrated increases in plasma GIP (0-300 min) concentrations were not significantly different; however, GIP (0-45 min) concentrations were significantly higher in group FH than in groups CL and FL (P less than 0.05). There were no differences in plasma insulin concentrations. Plasma glucose (0-300 min) concentrations were significantly higher in groups FL and FH compared with group CL (P less than 0.05). The GIP content of tissue samples taken at the end of the experiment from the duodenum, jejunum, upper and lower ileum decreased significantly in a proximal to distal direction (P less than 0.001). Diet FH significantly increased the average GIP content of the small intestine compared with diets CL and FL (P less than 0.05). It is concluded that fat meal-stimulated GIP secretion was enhanced by increased feeding level during a pre-treatment phase, possibly due to an increase in GIP synthesis in the small intestine. The high-fat diet caused glucose intolerance after a high-fat meal. This may be due in part to the action of dietary fat on glucose transport and metabolism.