Dietary iron or inulin supplementation alters iron status, growth performance, intramuscular fat and meat quality in finisher pigs.

Forty LW × L pigs (20 boars and 20 gilts) (51.1 ± 0.41 kg) were allocated to a 2 × 2 × 2 factorial design with the respective factors being supplemental organic iron (Fe, 0 and 500 mg/kg), inulin (In, 0 and 50 g/kg) and sex (boars and gilts). After 5 weeks the animals were transported to an abattoir before slaughter and collection of samples. Serum iron was increased by supplemental Fe (28.4 v. 30.9 µmol/L, P = 0.05), although there was an interaction (P = 0.03) such that pigs fed diets with In had lower serum Fe concentrations than those without In (26.8 v. 32.3 µmol/L). Boars had lower (P < 0.01) haemoglobin (116 vs 125), haematocrit (36.7 v. 39.7%) and erythrocyte (6.6 v. 7.1 × 106/mL) concentrations than gilts. Dietary In increased liveweight gain (795 v. 869 g/d, P < 0.02) and carcass weight (62.9 v. 65.2 kg, P < 0.02). Dietary Fe or In supplementation did not improve muscle Longissimus thoracis et lumborum (LTL) total Fe concentration (P > 0.05). Muscle non-heme Fe concentration was higher in Fe-supplemented pigs (P < 0.04) and gilts (P < 0.05) than their counterparts. Muscle heme Fe concentration was greater (3.04 vs 2.51, P < 0.05) in boars than in gilts. The LTL marbling score was greater (P < 0.01) for In-supplemented pigs, and the response was more notable when Fe and In were fed together. These data show that dietary supplementation of Fe increased serum Fe and muscle non-heme Fe concentrations. Supplementation of In at 5% in the diet of finisher pigs improved liveweight gain and the marbling score of pork.

Effects of niacin and betaine on bovine mammary and uterine cells exposed to thermal shock in vitro.

The objective of this study was to investigate the direct effects of feed supplements niacin and betaine on the heat shock responses of in vitro cultured cells derived from bovine mammary and uterine tissues. First, we determined the mRNA expression profiles of the niacin receptor (GPR109A) in bovine tissues (liver, skin, uterus, udder, and ovary) and in cells derived from bovine mammary epithelium (mammary alveolar cells, MAC-T; bovine mammary epithelial cells, BMEC) and endometrium (bovine endometrial cells, BEND). We found that GPR109A was distributed in all examined tissues and cells, and the highest expression was in cells from skin and udder. Second, we evaluated the effects of niacin treatment on the mRNA abundance of heat shock proteins 70 and 27 (HSP70 and HSP27) in MAC-T, BMEC, and BEND under thermoneutral conditions and heat stress, and whether these effects were associated with alterations in the mRNA expression of prostaglandin E2 synthesis-related genes, including cyclooxygenase 1 and 2 (COX-1 and COX-2) and microsomal prostaglandin E synthase 1 and 2 (mPGES-1 and mPGES-2). Quantitative PCR data indicated that niacin suppressed HSP70 mRNA expression in BMEC and both HSP70 and HSP27 in BEND under thermoneutral conditions. Only COX-2 expression was downregulated by niacin in BMEC; other prostaglandin E2 synthesis-related genes stayed unaltered in BMEC and BEND. The mRNA abundance of HSP70, COX-1, COX-2, and mPGES-1 were elevated in niacin-treated MAC-T. During heat stress, niacin increased mRNA levels of HSP70 and HSP27 in MAC-T and HSP27 in BEND, but decreased HSP70 in BMEC. Although mPGES-2 was stimulated by niacin in BEND, the mRNA expression of prostaglandin E2 synthesis-related genes were consistent with neither HSP70 nor HSP27 expression patterns in niacin-treated BMEC and MAC-T. These data suggest that the effects of niacin on heat shock protein expression and prostaglandin E2 synthesis were not well coupled in these cells. Finally, we tested the effects of betaine treatment on viability and apoptosis in BMEC. Compared with control cultures, viability was higher in betaine-treated cells at 8 h under thermoneutral conditions and at 16 h in heat stress, and apoptotic rates were lower at 8 h. Our data support a dual role for niacin in regulating heat shock protein expression in normal and heat-shocked cells derived from mammary and uterine tissues, and positive effects of betaine in regulating mammary cell viability during heat stress.

Boar taint, meat quality and fail rate in entire male pigs and male pigs immunized against gonadotrophin releasing factor as related to body weight and feeding regime.

The objective of this experiment was to compare the pork quality of entire male pigs and pigs immunized against GnRF (IC males) at both light (64.8kg) and heavy (106kg) liveweights and two feeding regimes (restricted at 2.5 times maintenance and ad libitum). There was no difference in objective measurements (P>0.05) or eating pork quality (P>0.1) between entire male and IC males. Fail rates were reduced by 9.1% and 12% for pork from IC males for quality grade (P=0.007) and re-purchase intention (P=0.001), respectively, compared to pork from entire males. Skatole (P=0.001) and androstenone (P<0.001) levels in belly fat were higher in entire male than IC male pigs. In addition, 37.5% of the light entire male pigs fed ad libitum showed skatole levels that exceeded the sensory threshold of 0.2µg/g. This work confirms that immunization against GnRF is effective in eliminating boar taint and reducing pork quality fail rates by approximately 10% compared to pork from entire males.

Effect of feed restriction and initial body weight on growth performance, body composition, and hormones in male pigs immunized against gonadotropin-releasing factor.

Pigs immunized against gonadotropin-releasing factor (GnRF) have increased carcass fatness compared to entire males; however, the timing of this increase in fatness after the second immunization against GnRF has not been determined. An experiment was conducted to identify and compare the growth performance, body composition, and physiological changes in immunocastrated males (IC males) at different BW and feeding levels. A total of 64 pigs were used in a 2 × 2 × 2 factorial experiment with the treatments being 1) sex (entire males or IC males), 2) initial BW (45.9 kg [light] or 78.3 kg [heavy]), and 3) feeding regime (2.5 times maintenance [restricted] or ad libitum). The pigs were individually housed, and the diets were fed for 4 wk after the second immunization against GnRF until slaughter at either 68.4 kg BW (light) or 105.8 kg BW (heavy). Immunocastrated males on a restricted feed intake had a lower ADG compared to entire males from d 15 to 28 and d 0 to 28 ( 0.011 and 0.011, respectively). Fat deposition was not affected by sex from d 0 to 14, but from d 15 to 28 IC males deposited 45 g/d more fat than entire males ( = 0.025). Immunocastrated male pigs fed ad libitum deposited 87 g/d more fat from d 15 to 28 than entire males fed ad libitum ( = 0.036). However, there was no difference in fat deposition between IC males and entire males when feed intake was restricted from d 15 to 28. Plasma urea nitrogen levels were greater in IC males compared to entire males from d 7 after the second immunization against GnRF ( 0.05 for d 7, 10, 14, 21, and 28). Plasma concentrations of IGF-1 were lower for IC males compared to entire males on d 3, 7, 10, and 28 ( 0.05 for all days). The following conclusions were made: 1) when pigs are immunized at a light BW (50 kg) and/or are on a restricted feed intake, they have a reduced propensity to deposit fat; however, the restriction in feed intake adversely affects growth rate. 2) The majority of fat deposition for males immunized at heavy BW (80 kg) occurs from d 15 to 28 after the second immunization against GnRF.

Evaluation of dietary betaine in lactating Holstein cows subjected to heat stress.

Betaine (BET), a natural, organic osmolyte, improves cellular efficiency by acting as a chaperone, refolding denatured proteins. To test if dietary BET reduced the effect of heat stress (HS) in lactating dairy cows, multiparous, lactating Holstein cows (n=24) were blocked by days in milk (101.4±8.6 d) and randomly assigned to 1 of 3 daily intakes of dietary BET: the control (CON) group received no BET, mid intake (MID) received 57mg of BET/kg of body weight, and high dose (HI) received 114mg of BET/kg of body weight. Cows were fed twice daily and BET was top-dressed at each feeding. Cows were milked 2 times/d and milk samples were taken daily for analysis. Milk components, yield, feed intake, and water intake records were taken daily. Rectal temperature and respiration rate were taken 3 times/d at 0600, 1400, and 1800h. Cows were housed in environmentally controlled rooms and were allowed acclimation for 7d at thermoneutral (TN) conditions with a mean temperature-humidity index of 56.6. Cows were then exposed to 7d of TN followed by 7d of HS represented by a temperature-humidity index of 71.5 for 14d. This was followed by a recovery period of 3d at TN. Dietary BET increased milk yield during the TN period. No differences were found between BET and CON in total milk production or milk composition during HS. The increase in water intake during HS was not as great for cows fed BET compared with controls. The cows on CON diets had higher p.m. respiration rate than both MID and HI BET during HS, but lower rectal temperature compared with BET. No difference was found in serum glucose during TN, but cows given HI had elevated glucose levels during HS compared with CON. No differences were found in serum insulin levels between CON and BET but an intake by environment interaction was present with insulin increasing in HI-treated lactating dairy cows during HS. The heat shock response [heat shock protein (HSP) 27 and HSP70] was upregulated in bovine mammary epithelial cells in vitro. Blood leukocyte HSP27 was downregulated at the HI dose under TN conditions and HSP70 was upregulated at the HI dose and this effect was increased by HS. No effect was seen with the MID dose with HSP27 or HSP70. The lack of effect of BET at MID may be associated with uptake across the gut. We conclude that BET increased milk production under TN conditions and was associated with reduced feed and water intake and slightly increased body temperatures during HS of cows fed BET. The effect of BET on milk production was lost during HS with HI BET, whereas serum glucose levels increased during HS.

Standardized ileal digestible lysine requirements of male pigs immunized against gonadotrophin releasing factor.

An experiment was conducted to determine the standardized ileal digestible (SID) Lys requirement of entire male and male pigs immunized against gonadotrophin releasing factor (GnRF; immunocastrates). A total of 420 entire male and immunocastrated (IC) male pigs weighing 60.1 kg BW (SEM 0.49) were used in a 2 × 5 factorial experiment with the main effects being gender (entire males or IC males) and 5 concentrations of SID Lys:DE ratio (0.32, 0.43, 0.54, 0.64, or 0.75 g SID Lys/MJ DE). The diets were fed for 6 wk until slaughter at 107.5 kg BW (SEM 5.72). Over the entire period, IC males had a greater ADG ( < 0.001), greater ADFI ( < 0.001), and lower G:F ( < 0.001) compared with entire males. Immunocastrated males had increased plasma urea nitrogen (PUN) concentrations compared with entire males from d 10 to 42 ( < 0.001 for all days). Plasma urea nitrogen concentration also increased as Lys concentrations increased from d 3 to 42 ( < 0.001 for all days). Using the linear-plateau model, the optimal ADG for entire males was achieved at SID Lys concentrations of 0.68, 0.62, 0.54, and 0.58 g/MJ DE whereas optimal G:F was achieved at SID Lys concentrations of 0.72, 0.60, 0.54, and 0.51 g/MJ DE for the time periods d 0 to 14, d 15 to 28, d 29 to 42, and d 0 to 42, respectively. For IC males, optimal ADG was achieved at SID Lys concentrations of 0.64, 0.43, 0.38, and 0.40 g/MJ DE whereas optimal G:F was achieved at SID Lys concentrations of 0.64, 0.43, 0.36, and 0.42 g/MJ DE for the same respective time periods. Using the quadratic polynomial model, maximum ADG for entire males was achieved at SID Lys concentrations of 0.62 and 0.58 g/MJ DE whereas maximum G:F was achieved at SID Lys concentrations of 0.59 and 0.68 g/MJ DE for d 29 to 42 and d 0 to 42, respectively. For IC pigs, maximum ADG was achieved at SID Lys concentrations of 0.69, 0.54, and 0.64 g/MJ DE whereas maximum G:F was achieved at SID Lys concentrations of 0.81, 0.54, and 0.64 g/MJ DE for d 0 to 14, d 29 to 42, and d 0 to 42, respectively. A solution could not be found using the quadratic polynomial model for entire males for d 0 to 14 for both ADG and G:F and for both entire males and IC males for d 15 to 28 within the range of Lys values tested. When both the growth performance and PUN values are considered, the results suggest that IC males show a response to dietary SID Lys similar to that of entire males for 2 wk after the second immunization against GnRF. After this, IC males have a lower requirement for SID Lys than entire males.

IGFBP-2 inhibits adipogenesis and lipogenesis in human visceral, but not subcutaneous, adipocytes.

BACKGROUND/OBJECTIVE: IGF-binding protein (IGFBP)-2 is the principal IGFBP produced by white adipocytes during adipogenesis, and circulating levels are reduced in obesity. Overexpression of IGFBP-2 in transgenic mice prevents obesity, but depot-specific effects of IGFBP-2 on adipo/lipogenesis are unknown. The present study aimed to investigate whether IGFBP-2 affects adipo/lipogenesis in a depot-specific manner and explore potential mechanisms. METHODS: Following adipocyte characterisation, IGFBP-2 levels were measured from human subcutaneous and visceral preadipocytes, and IGFBP-2 dose-responses were then undertaken with exogenous IGFBP-2 in an in vitro IGF-I-free system to examine adipo/lipogenesis. Following this, both types of adipocytes were transfected with human siRNA IGFBP-2 to assess auto-/para-/intra-crine effects, with and without additional add-back IGFBP-2. To elucidate the potential mechanisms, visceral preadipocytes were treated with either wild-type or Heparin Binding Domain (HBD)-mutant IGFBP-2 (which is unable to bind to cell-surface components), and experiments were also undertaken using Echistatin (an integrin receptor blocker). Outcomes included gene expression profiles, protein levels and phosphorylation and lipid staining. RESULTS: Human visceral adipocytes produced significantly more IGFBP-2 than subcutaneous adipocytes. Subsequent dose-responses to IGFBP-2 demonstrated significant reductions in adipo/lipogenesis in visceral, but not subcutaneous, adipocytes in response to increasing IGFBP-2. Silencing IGFBP-2 resulted in exaggerated adipo/lipogenesis in visceral, but not subcutaneous, adipocytes, an effect completely inhibited by add-back IGFBP-2. These effects occurred in the absence of changes in IGF-I levels. HBD-mutant IGFBP-2 had reduced effects compared with wild-type IGFBP-2. Wild-type IGFBP-2 increased phosphorylation of focal adhesion kinase (FAK) and decreased phosphatase and tensin homolog (PTEN) levels, suggestive of integrin-mediated signalling. Blockade of this signalling, using Echistatin, completely negated the effects of IGFBP-2 on visceral adipo/lipogenesis. CONCLUSION: IGFBP-2 inhibits both adipogenesis and lipogenesis in visceral, but not subcutaneous, adipocytes. This depot-specific impairment appears to be independent of IGF-I and involves cell-surface association of IGFBP-2 and activation of integrin signalling pathways.

Dietary antioxidants at supranutritional doses modulate skeletal muscle heat shock protein and inflammatory gene expression in sheep exposed to heat stress.

The objective of this study was to investigate the effects of chronic heat (thermal) stress and dietary antioxidant supplementation on the expression of heat shock proteins and inflammatory genes in the skeletal muscle of sheep. Twenty-four Merino × Poll Dorset crossbred ewes were allocated to either a control (10 IU vitamin E and 0.24 mg Se/kg DM) or high-antioxidant (VitE+Se; 100 IU vitamin E and 1.20 mg Se/kg DM) diet and were exposed to 2 thermal (temperature) treatments (thermoneutral [TN]: 18°C-21°C and 26%-30% relative humidity; heat stress [HS]: 28°C-40°C and 40%-50% relative humidity) for 1 wk. Physiological parameters were recorded daily, and muscle biopsies were conducted at the end of thermal treatments. Total RNA was extracted from muscle samples and reverse transcribed to cDNA for real-time PCR analysis. Respiration rates and rectal temperature were increased in response to HS (84.2 vs. 161 breaths per minute and 39.52°C vs. 40.06°C for TN and HS conditions, respectively; P < 0.001). There were interactions between dietary and thermal treatments, indicating that dietary antioxidant supplementation reduced respiration rate (P = 0.097) and rectal temperature (P = 0.086) of sheep during HS but not TN conditions. Skeletal muscle heat shock transcription factor 1 (HSF1) mRNA abundance was increased by HS (1.3-fold; P < 0.050) but was not changed (P = 0.77) by dietary antioxidant supplementation. The expression of skeletal muscle heat shock protein 70 (HSP70) mRNA was increased (P < 0.001) 3.5-fold by HS and tended (P = 0.08) to be increased by dietary antioxidant supplementation. Although there were no main effects of diet (P = 0.42) or HS (P = 0.47) on skeletal muscle HSP90 mRNA expression, there was an interaction (P = 0.040) such that HSP90 mRNA expression was increased (P = 0.010) in antioxidant-supplemented sheep under HS compared to TN conditions. Skeletal muscle nuclear factor kappa B (NF-κB) and tissue necrosis factor α (TNF-α) mRNA abundances were increased by exposure to heat (5.2-fold, P = 0.005 for NF-κB; 5.7-fold, P = 0.013 for TNF-α) ,but there was no main effect (P > 0.05) of dietary antioxidant supplementation. There was, however, an interaction between thermal and dietary treatments such that dietary antioxidant supplementation ameliorated the effect of HS on NF-κB and TNF-α mRNA expression. Taken together, these results indicate that high dietary antioxidants modulate skeletal muscle expression of heat shock proteins, proinflammatory cytokine, and NF-κB transcription, which may protect against HS in sheep.

Dietary antioxidants at supranutritional doses improve oxidative status and reduce the negative effects of heat stress in sheep.

The present study was undertaken to investigate the impact of heat (thermal) stress and dietary antioxidant supplementation on the oxidative and physiological status of sheep. Twenty-four Merino × Poll Dorset crossbred ewes were housed in 1 of 2 climatic chambers (thermoneutral or heat stress) and offered either a control (10 IU vitamin E/kg DM and 0.24 mg Se/kg DM) or high antioxidant (100 IU vitamin E/kg DM and 1.20 mg Se/kg DM) diet. The sheep were exposed to 2 thermal (temperature) treatments (thermoneutral [TN]: 18-21°C and 26-30% relative humidity; and heat stress [HS]: 28-40°C and 40-50% relative humidity) for 2 wk in a single reversal design. After 1 wk of dietary treatment, animals in 1 chamber were subjected to HS for 1 wk, with the temperature being increased to 40°C between 0900 and 1700 h and then maintained at 28°C overnight. Those sheep in the TN group were maintained at 18 to 21°C. Physiological parameters were recorded 4 times a day (0900, 1300, 1700, and 2100 h) and blood samples were collected on d 1 and 7 of heat treatment. Plasma samples and red blood cell lysates were assayed for oxidative stress biomarkers. The thermal treatments were then reversed and the above measures repeated. All measured physiological parameters were elevated (P < 0.001) by thermal treatment. Respiration rate was lower during HS in sheep supplemented with antioxidants as indicated by a diet × temperature × time interaction (P = 0.010). There was 13% decline (P = 0.014) in feed intake of the unsupplemented animals during HS whereas the same was maintained in sheep supplemented with high doses of antioxidants. Plasma reactive oxygen metabolites concentrations were reduced (114 vs. 85 units/dL; P < 0.005) while biological antioxidant potential tended to be increased (3,688 vs. 3,985 µmol/L; P = 0.070) in heat stressed sheep supplemented with antioxidants. The oxidative stress index was 30% lower (P < 0.001) in supplemented sheep (2.16 ± 0.06 arbitrary units) during HS than in unsupplemented sheep (3.12 ± 0.08 arbitrary units). Plasma advanced oxidation protein products tended (P = 0.070) to decrease in antioxidant supplemented heat stressed sheep as compared to their unsupplemented counterparts. It was concluded that heat stress negatively affects the oxidative status of sheep along with the physiological responses and some of these affects can be ameliorated through dietary antioxidants supplementation at supranutritional concentrations.

The effect of immunization against GnRF on nutrient requirements of male pigs: a review.

In most countries, male pigs are physically castrated soon after birth to reduce the risk of boar taint and to avoid behaviours such as fighting and mounting. However, entire male pigs are more feed efficient and deposit less fat than barrows. In addition, many animal welfare organizations are lobbying for a cessation of castration, with a likelihood that this could lead to inferior pork unless an alternative method is used to control boar taint. An alternative to physical castration is immunization against gonadotrophin releasing factor (GnRF) which allows producers to capitalize on the superior feed efficiency and carcass characteristics of boars without the risk of boar taint. From a physiological perspective, immunized pigs are entire males until shortly after the second dose, typically given 4 to 6 weeks before slaughter. Following full immunization, there is a temporary suppression of testicular function and a hormonal status that resembles that of a barrow. Nutrient requirements will be different in these two phases, before and after full immunization. Given that there have been few published studies comparing the lysine requirements of entire males and barrows in contemporary genotypes, it is useful to use gilt requirements as a benchmark. A series of meta-analyses comparing anti-GnRF immunized boars and physical castrates and use of nutritional models suggest that the lysine requirement of entire males before the second immunization is 5% higher than for gilts, from 25 to 50 kg BW, and by 8% from 50 to 95 kg. Given that the penalty in growth performance for having inadequate dietary lysine is greater in males than in gilts or barrows, it is important to ensure that lysine requirements are met to obtain the maximum benefits of entire male production during this phase. After the second immunization, the lysine requirement of immunized males decreases and may become more like that of barrows. In addition, a consistent effect of full immunization is a marked increase in voluntary feed intake from about 10 days after the second dose. Putting these together, the estimated lysine requirement, expressed in terms of diet composition, falls to 94% of the gilt level. Although general principles can be described now, further research is needed to fully define the lysine requirements of immunized boars. It is important that the temporal pattern of tissue deposition rates and feed intake be explored to be incorporated into models to predict nutrient requirements over the period of rapidly changing metabolism.

Reducing the length of time between slaughter and the secondary gonadotropin-releasing factor immunization improves growth performance and clears boar taint compounds in male finishing pigs.

The objective of this study was to evaluate whether altering the timing of the secondary anti-gonadotropin-releasing factor (GnRF) immunization closer to slaughter in male finishing pigs would reduce the increase in P2 fat depth (6.5 cm from the midline over the last rib), while still limiting the incidence of boar taint. Entire male pigs are immunized against GnRF to reduce the concentration of testicular steroids that in turn limits the incidence of boar taint. Additionally, testicle measurements and color measurements were taken to examine whether they could be used to differentiate nonimmunized entire males from immunized male pigs. A total of 175 Large White × Landrace entire male pigs aged 16 wk (59 kg of BW) were used in a completely randomized design with 5 treatment groups based on the time that pigs received the secondary immunization before slaughter. Pigs were housed in groups of 7 and randomly allocated to 1 of 5 treatments with 5 replicates per treatment. The treatment groups were as follows: no secondary immunization before slaughter, and the secondary immunization given at 2, 3, 4, or 6 wk before slaughter. The P2 fat depth levels were reduced (P = 0.054) with the secondary immunization closer to slaughter (11.7, 11.3, 12.8, 12.6, and 13.7 mm for no secondary immunization, secondary immunization at 2, 3, 4, and 6 wk before slaughter, respectively). Androstenone concentration did not exceed the generally accepted industry sensory threshold of 1.0 µg/g of fat, and both androstenone concentration in the adipose tissue and testosterone concentrations in the blood were suppressed (P < 0.001) in all immunized pigs regardless of timing of the secondary immunization compared with pigs that did not receive the secondary immunization. Skatole concentration of all pigs in the experiment did not exceed the generally accepted industry sensory threshold of 0.2 µg/g. Testes weight was reduced (P < 0.001) with increased time between slaughter and the secondary immunization. Immunized pigs, regardless of time before slaughter, had greater L* (lightness) and b* (yellowness) color of the testicle surface (P < 0.001 and P = 0.020, respectively), and less a* (redness) color compared with entire males (P < 0.001). The study provides further evidence of the efficacy of the anti-GnRF immunization and indicates that the secondary immunization can be moved closer to slaughter, while still limiting the incidence of boar taint. Testicle measurements and color measurements together could provide a method of discrimination between carcasses from immunized entire males clear of boar taint and tainted carcasses.

Changes in insulin, glucose and ketone bodies, but not leptin or body fat content precede restoration of luteinising hormone secretion in ewes.

The reproductive system, including pulsatile luteinising hormone (LH) secretion, is inhibited by deficits in energy availability and restored by energy surfeits. Plasma LH, insulin, leptin, ghrelin, glucose, ketone body, and nonesterified fatty acid concentrations were measured in ovariectomised, food-restricted ewes before and after return to ad libitum feeding to determine the factors that change in time to account for the restoration of pulsatile LH secretion. At 07.00 h, blood was sampled every 10 min for 5 h from ovariectomised, hypogonadotrophic, chronically food-restricted and ad libitum-fed ewes (Fed). At 12.00 h, four of the food-restricted sheep were given ad libitum access to food (Re-Fed), while three ewes continued to be food restricted (Restricted). Sampling continued for 5 h and resumed again on the mornings of days 2, 4, and 9. A pulse of LH was seen within 1 h of re-feeding in all Re-Fed ewes, and interpulse interval (IPI) was significantly shorter in Re-Fed compared to Restricted ewes and longer than in Fed ewes during the period after re-feeding. Re-Fed LH IPI was not restored to that of Fed ewes until sometime between days 4 and 9. The first pulse occurred within minutes, whereas restoration of IPI occurred after 4-8 days. Prior to the initial LH pulses seen in Re-Fed ewes, plasma ketone bodies first fell and then rose to levels significantly above those in Restricted ewes. Significant changes in circulating insulin, ghrelin, glucose, and total ketone body concentrations, daily food intake and lean body mass preceded restoration of Re-Fed LH IPI some time between days 4 and 9, but there were no significant changes in adiposity or circulating leptin concentrations, consistent with the hypothesis that LH pulses are reinitiated by changes in the availability of oxidisable metabolic fuels and possibly insulin, but not leptin concentrations.

A gonadotropin-releasing factor vaccine (Improvac) and porcine somatotropin have synergistic and additive effects on growth performance in group-housed boars and gilts.

Two hundred and twenty-four pigs (112 boars, 112 gilts) housed in pens of seven pigs per pen were used in a 2 x 2 x 2 factorial design, with the factors of vaccination with a gonadotropin-releasing factor (GnRF) vaccine (Improvac; 0 or 2 mL at 13 and 17 wk of age), porcine somatotropin (pST; 0 or 5 mg/d from 17 wk of age), and gender. Pigs were weighed and feed intake was measured from 17 wk of age until slaughter at 21 wk of age. Body composition was estimated by dual-energy X-ray absorptiometry in two focus pigs per pen at 17 and 21 wk of age. Testes and ovary weights at slaughter were decreased by Improvac treatment (P < 0.001), but were not altered by pST treatment (P > 0.44). Daily gain was lower for gilts than boars (1,128 vs. 1,299 g/d, P < 0.001) and was increased by pST (1,172 vs. 1,255 g/d, P = 0.003) and Improvac (1,150 vs. 1,276 g/d, P < 0.001) treatments. Feed intake (as-fed basis) was lower in gilts than in boars (2,774 vs. 3,033 g/d, P = 0.002), was decreased by pST (3,037 vs. 2,770 g/ d, P = 0.002), and was increased by Improvac treatment (2,702 vs. 3,105 g/d, P < 0.001). As a result of the differences in feed intake and daily gain, feed conversion efficiency (gain:feed) was lower for gilts than for boars (0.403 vs. 0.427 P = 0.025), was improved by pST (0.385 vs. 0.452, P < 0.001), but was unchanged by Improvac treatment (0.423 vs. 0.410, P = 0.22). Carcass weight was lower in gilts than in boars (75.3 vs. 77.0 kg, P = 0.012), was unchanged by pST treatment (75.9 vs. 76.4 kg, P = 0.40), and was increased by Improvac treatment (75.1 vs. 77.2 kg, P = 0.003). Lean tissue deposition rate was lower in gilts than in boars (579 vs. 725 g/d, P < 0.001), was increased by pST (609 vs. 696 g/d, P < 0.001) and by Improvac treatment (623 vs. 682 g/d, P = 0.014). Fat deposition rate tended to be lower in gilts than in boars (214 vs. 247 g/d, P = 0.063), decreased by pST treatment (263 vs. 198 g/d, P < 0.001), and increased by Improvac treatment (197 vs. 264 g/d, P < 0.001). For pigs treated with both pST and Improvac, daily gain and lean tissue deposition rate was greater than for pigs that received either treatment alone, whereas fat deposition rate and feed intake did not differ from untreated control pigs. In conclusion, Improvac increased growth rate through increased lean and fat deposition, but concomitant use of Improvac and pST increased lean gain above either alone, while negating the increase in fat deposition in pigs treated with Improvac.

Vaccination of boars with a GnRH vaccine (Improvac) eliminates boar taint and increases growth performance.

Peri- and postpubertal boars accumulate substances (e.g., androstenone and skatole) in their fatty tissue that are responsible for boar taint in pork. The objective of this study was to assess the efficacy of a GnRH vaccine, Improvac, in eliminating boar taint. Three hundred male (200 intact boars, 100 barrows) crossbred (Large White x Landrace) pigs were used in a 2 x 3 factorially arranged experiment. The respective factors were sex group (barrows, boars treated with placebo, or boars treated with Improvac) and slaughter age (23 or 26 wk). Vaccines were administered 8 and 4 wk before slaughter. All Improvac-treated pigs exhibited anti-GnRH titers. Testes and bulbo-urethral gland weights in treated pigs were reduced by approximately 50% (P < 0.001) and serum testosterone levels were below 2 ng/mL in the majority of treated boars (94 and 92% across both age groups at 2 and 4 wk, respectively). Boar taint, as assessed by the concentration of androstenone and skatole in s.c. fat, was suppressed to low or undetectable levels in 100% of Improvac-treated boars. No Improvac-treated pigs had significant concentrations of either androstenone (> 1.0 microg/g) or skatole (> 0.20 microg/g). In contrast, 49.5% of placebo-treated controls had significant androstenone and 10.8% had significant skatole levels, resulting in 10% of the control boars with high concentrations of both compounds. The mean concentrations of taint compounds in the Improvac-treated pigs were not significantly different from those in barrows. Improvac-treated boars grew more rapidly (P = 0.051 and < 0.001 for pigs slaughtered at 23 and 26 wk of age, respectively) than control boars over the 4 wk after the secondary vaccination, possibly because of reduced sexual and aggressive activities. Compared with barrows, Improvac-treated boars were leaner and had superior feed conversion efficiency. The vaccine was well tolerated by the pigs, and no observable site reactions could be detected at the time of slaughter. Vaccination of boars with Improvac allows production of heavy boars with improved meat quality through prevention and control of boar taint.

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs.

BACKGROUND: Recent studies suggest that resistant starch (effective in producing butyrate and lowering possibly toxic ammonia) is rapidly fermented in the proximal colon; the distal colon especially would, however, benefit from these properties of resistant starch. AIMS: To determine whether wheat bran (a rich source of insoluble non-starch polysaccharides), known to hasten gastrointestinal transit, could carry resistant starch through to the distal colon and thus shift its site of fermentation. METHODS: Twenty four pigs were fed four human type diets: a control diet, or control diet supplemented with resistant starch, wheat bran, or both. Intestinal contents and faeces were collected after two weeks. RESULTS: Without wheat bran, resistant starch was rapidly fermented in the caecum and proximal colon. Supplementation with wheat bran inhibited the caecal fermentation of resistant starch, resulting in an almost twofold increase (from 12.9 (2.5) to 20.5 (2.1) g/day, p<0.05) in resistant starch being fermented between the proximal colon and faeces. This resulted in higher butyrate (133%, p<0.05) and lower ammonia (81%, p<0.05) concentrations in the distal colonic regions. CONCLUSIONS: Wheat bran can shift the fermentation of resistant starch further distally, thereby improving the luminal conditions in the distal colonic regions where tumours most commonly occur. Therefore, the combined consumption of resistant starch and insoluble non-starch polysaccharides may contribute to the dietary modulation of colon cancer risk.

The testis is not the major source of circulating follistatin in the ram.

The aims of this study were to determine the plasma concentrations of follistatin in rams and to assess if the testis contributes to circulating follistatin and if there is uptake or production of follistatin by the head in rams. Catheters were inserted in the carotid artery, jugular vein and spermatic vein of intact rams during the non-breeding season (experiment 1; n = 5) and breeding season (experiment 2; n = 4). In experiment 1, blood samples were collected from 5 rams every 10 min for 4 h, commencing 20-60 min after surgery. After 2 h of sampling 1 microgram gonadotrophin-releasing hormone (GnRH) was injected intravenously. In experiment 2, blood samples were collected from 4 of the rams used in experiment 1 by venipuncture 30 and 15 min before surgery and every 15 min throughout surgery. Commencing 1 h after surgery, matched samples were taken from each of the vessels every 10 min for 4 h (1-4 h after surgery), then every hour for 20 h (4-24 h after surgery) and then every 10 min for 4 h (24-28 h after surgery). In both experiments, follistatin secretion was non-pulsatile and there were no significant differences between the concentrations of follistatin in any of the vessels. There was a significant (P < 0.05) increase in the concentrations of follistatin in each of the vessels throughout the 4 h of 10-min sampling in both experiments. In experiment 2 plasma concentrations of follistatin in the jugular vein were significantly (P < 0.05) lower before surgery than at other stages of the experiment. During the non-breeding season (experiment 1) the concentrations of follistatin in all vessels were about 2-fold higher (P < 0.001) than during the breeding season (experiment 2). Concentrations of follistatin were measured in the testicular tissue of the ram, bull, monkey and rat and were found to be 13.6, 2.1, 2.5, 0.8 ng/g testis respectively. In experiment 3, blood samples were collected every 15 min for 4 h from castrated rams (n = 6) in the absence of treatment with testosterone propionate (TP) and after 7 days of treatment with a physiological dose of TP during the breeding and non-breeding seasons. There was no effect of stage of breeding season or TP on the plasma concentrations of follistatin and these concentrations in the castrated rams were similar to the concentrations in the intact rams in experiment 2. In experiment 4, the function of Leydig cells was stimulated by administration of human chorionic gonadotrophin but this had no effect on plasma concentrations of follistatin. These experiments show that the concentrations of follistatin in the plasma of rams are measurable, that the testis is not the major contributor to circulating follistatin and that there is no significant uptake or production of follistatin by the head in rams. It appears that the contribution of the testis to circulating follistatin may vary with the stage of the breeding season, being greater during the non-breeding season than the breeding season. The gonadotrophins and testosterone do not appear to have a direct effect on the secretion of follistatin in rams. The increase in concentrations of circulating follistatin during surgery and more frequent blood sampling suggest a stress-related effect on the production of follistatin.

Pregnancy but not moderate undernutrition attenuates insulin suppression of fat mobilization in sheep.

Nonpregnant and late-pregnant ditocous ewes were fed either to maintain zero energy balance in maternal tissues (fed) or at 50% of this level (underfed) for several weeks. Plasma concentrations of nonesterified fatty acids (NEFA) and glycerol were measured under basal conditions and during infusion of various doses of insulin while maintaining euglycemia (hyperinsulinemic, euglycemic clamp technique). Pregnancy and undernutrition separately increased basal plasma NEFA concentration in an additive manner; plasma glycerol was increased by pregnancy but unaffected by undernutrition. The molar ratio of NEFA to glycerol was significantly greater in underfed ewes. Analysis of dose-response relations between plasma insulin and metabolites during insulin infusions showed that maximally insulin-suppressed concentrations of NEFA and glycerol were significantly greater in pregnant than in nonpregnant ewes but were unaffected by undernutrition. Neither pregnancy nor undernutrition affected the maximally insulin-suppressed NEFA to glycerol ratio, or the plasma insulin concentration for 50% maximal responses to insulin of plasma NEFA, plasma glycerol, or the plasma NEFA to glycerol ratio. Thus, even in ewes at or close to zero energy balance, pregnancy seems to reduce adipose responsiveness but not sensitivity to the antilipolytic effect of insulin. This is another manifestation of the normal development of insulin resistance in maternal tissues during late pregnancy.

Effect of porcine somatotropin on in vivo glucose kinetics and lipogenesis in growing pigs.

Crossbred barrows were used for in vivo studies investigating hormonal regulation of lipogenesis. The first experiment examined an in vivo method for determining rates of lipogenesis. Three barrows were infused with [U-14C]glucose and incorporation of radioactivity into triglycerides was determined in up to five biopsies of subcutaneous adipose tissue obtained over 7 h. Incorporation was linear after blood glucose specific radioactivity had reached a plateau and was constant over the entire infusion. For the second experiment, eight pigs (71 +/- 2.5 kg) were allocated to one of two treatments involving daily injections of excipient (control) or porcine somatotropin (pST; 120 micrograms/kg of BW). On d 10, beginning 15 h after injection, glucose incorporation into adipose tissue lipid was determined under both basal and hyperinsulinemic/euglycemic conditions. Basal glucose incorporation into lipid, particularly fatty acids, was markedly reduced (greater than 90%) during pST treatment. Although glucose incorporation was increased to a similar extent in both groups by hyperinsulinemia, the pST-treated pigs still exhibited markedly lower rates. Based on kinetic data, the decrease in lipid accretion of pST-treated pigs was primarily the result of a decrease in the rate of de novo synthesis. Furthermore, the reductions in glucose incorporation into fatty acids, glucose irreversible loss rate, and feed intake that occur with pST treatment were quantitatively similar.