Supplementation of dextrose to the diet during the weaning to estrus interval affects subsequent variation in within-litter piglet birth weight

Effects of supplementation of dextrose to the diet of sows during the weaning-to-estrus interval (WEI) on subsequent litter size and within-litter variation were investigated. After weaning, 223 sows (first to fifth parity) were fed 3.5 kg/d. Half of the sows additionally received 150 g of dextrose per day as topdressing on the feed. WEI and estrus duration were determined as well as subsequent pregnancy rate and litter size. Piglets were weighed individually at birth and at weaning (day 26.4; S.D.: 2.5). Supplementation of dextrose to the diet during the WEI did not affect WEI (106 h), pregnancy rate (88.2%), farrowing rate (84.2%), subsequent litter size (total born: 13.70), or birth weight (1599 g). The within-litter variation in birth weight was lower in sows on the dextrose treatment (CV: 17.5% versus 21.2% for the dextrose and control group, respectively, P=0.03). From this experiment, we concluded that addition of dextrose during the weaning to estrus interval did not increase litter size, but seems to affect the uniformity in birth weight of the litter.     

IGF-1 concentration patterns and their relationship with follicle development after weaning in young sows fed different pre-mating diets

Piglet birth weight and within-litter birth weight variation are important for piglet survival and growth. Pre-mating diets may improve IGF-1 and follicle development during the weaning-to-oestrus interval (WEI) and subsequent piglet birth weight. The objective of this study was to modulate IGF-1 concentration during late lactation and the WEI of young sows by using specific pre-mating diets supplemented with microfibrillated cellulose (MF), l-carnitine (LC) or l-arginine (AR). A further objective was to investigate the relationship between IGF-1 and subsequent follicle development and oestrus and ovulation characteristics. In total, 56 first-parity and 20 second-parity sows in three consecutive batches were used for this experiment. Sows received daily either wheat (CON) or wheat plus MF, LC or AR at one of two supplementation levels (low and high) during last week of lactation and WEI. From weaning onwards, follicle and corpus luteum (CL) diameters were repeatedly measured with ultrasound. Blood samples were collected during the WEI for IGF-1 and on day 21 of pregnancy for progesterone analyses, respectively. Insulin-like growth factor-1 concentration, follicle diameter, oestrus and ovulation characteristics and CL diameter were not affected by pre-mating diets. Low IGF-1 class (≤156 ng/ml, N = 22) sows had smaller follicles at weaning (3.5 v. 3.8 mm, P < 0.05) and a longer weaning-to-ovulation interval (147.2 v. 129.8 h, P < 0.05) than high IGF-1 class sows. In first-parity sows, high loin muscle depth (LM) loss sows (≥8%, N = 28) had lower IGF-1 concentrations at weaning (167 v. 214 ng/ml, P < 0.05) compared to low LM loss sows (<8%, N = 28). However, after weaning, IGF-1 concentrations increased and did not differ between high LM loss and low LM loss sows. In conclusion, the different supplemented compounds in pre-mating diets did not improve IGF-1 concentrations around weaning in young sows. Furthermore, high body condition loss caused lower IGF-1 concentrations at weaning, but these levels rapidly recovered after weaning and were related to follicle development and the interval from weaning to ovulation.     

Supplementing sow diets with palm oil during late gestation and lactation: effects on milk production,sow hormonal profiles and growth and development of her offspring

The supplementing of sow diets with lipids during pregnancy and lactation has been shown to reduce sow condition loss and improve piglet performance. The aim of this study was to determine the effects of supplemental palm oil (PO) on sow performance, plasma metabolites and hormones, milk profiles and pre-weaning piglet development. A commercial sow ration (C) or an experimental diet supplemented with 10% extra energy in the form of PO, were provided from day 90 of gestation until weaning (24 to 28 days postpartum) in two groups of eight multiparous sows. Gestation length of PO sows increased by 1 day (P<0.05). Maternal BW changes were similar throughout the trial, but loss of backfat during lactation was reduced in PO animals (C: −3.6±0.8 mm; PO: −0.1±0.8 mm; P<0.01). Milk fat was increased by PO supplementation (C day 3: 8.0±0.3% fat; PO day 3: 9.1±0.3% fat; C day 7: 7.8±0.5% fat; PO day 7: 9.9±0.5% fat; P<0.05) and hence milk energy yield of PO sows was also elevated (P<0.05). The proportion of saturated fatty acids was greater in colostrum from PO sows (C: 29.19±0.31 g/100 g of fat; PO: 30.77±0.36 g/100 g of fat; P<0.01). Blood samples taken on 105 days of gestation, within 24 h of farrowing, day 7 of lactation and at weaning (28±3 days post-farrowing) showed there were no differences in plasma concentrations of triacylglycerol, non-esterified fatty acids, insulin or IGF-1 throughout the trial. However, circulating plasma concentrations of both glucose and leptin were elevated during lactation in PO sows (P<0.05 and P<0.005, respectively) and thyroxine was greater at weaning in PO sows (P<0.05). Piglet weight and body composition were similar at birth, as were piglet growth rates throughout the pre-weaning period. A period of 7 days after birth, C piglets contained more body fat, as indicated by their lower fat-free mass per kg (C: 66.4±0.8 arbitrary units/kg; PO: 69.7±0.8 arbitrary unit/kg; P<0.01), but by day 14 of life this situation was reversed (C: 65.8±0.6 arbitrary units/kg; PO: 63.6±0.6 arbitrary units/kg; P<0.05). Following weaning, PO sows exhibited an increased ratio of male to female offspring at their subsequent farrowing (C: 1.0±0.3; PO: 2.2±0.2; P<0.05). We conclude that supplementation of sow diets with PO during late gestation and lactation appears to increase sow milk fat content and hence energy supply to piglets. Furthermore, elevated glucose concentrations in the sow during lactation may be suggestive of impaired glucose homoeostasis.     

Effects of L-carnitine on reproductive performance,milk composition,placental development and IGF concentrations in blood plasma and placental chorions in sows

Recent studies have shown that L-carnitine supplementation of sows during pregnancy and lactation enhances their reproductive performance, but the underlying mechanisms are still needed to be further confirmed. This study was conducted to investigate the function of L-carnitine on placental development, milk nutrient content and release of hormones in sows. In this experiment, 40 multiparous crossbred sows (Yorkshire × Landrace) were allotted to two groups fed diets with or without a supplemental 50 mg/kg L-carnitine. The experimental diets were fed from d 1 post-coitus until d 21 post-partum. L-carnitine-treated sow had fewer weak piglets (p < 0.05) and a greater percentage of oestrus by 5 after 5-d post-partum (p < 0.05) than control sows. The percentage fat from colostrum was greater in L-carnitine-treated sow than control sows (p < 0.05). L-carnitine-treated sows had greater plasma concentrations of triglyceride and insulin-like growth factor (IGF)-1 and lesser plasma concentrations of glucose and IGF-binding protein (IGFBP-3) on day 60 of pregnancy (p < 0.05). A clearer structure of chorions, better-developed capillaries and absence of necrosis were observed in L-carnitine-treated sows compared with control sows. The protein abundance of IGF-1 and IGF-2 in placental chorions was greater in L-carnitine-treated sows compared with control sows (p < 0.05). This study suggests that sows fed an L-carnitine supplemented diet during pregnancy improved reproductive performance through enhancement of placental development and by increasing IGF concentrations in blood plasma and placental chorions.     

IGF-1 concentrations after weaning in young sows fed different pre-mating diets are positively associated with piglet mean birth weight at subsequent farrowing

Pre-mating diets can influence piglet birth weight and within-litter birth weight variation and thereby piglet survival and development. The major objective of this study was to evaluate the litter characteristics of young sows whose pre-mating diets received different supplementation. The supplements included a top-dressing of 200 g, consisting of either wheat (CON) or wheat plus microfibrillated cellulose, _L-carnitine or _L-arginine at one of two supplementation levels (low and high) in late lactation and during the weaning-to-oestrus interval (WEI). The second objective was to investigate the role of body condition loss and IGF-1 concentration during the WEI for subsequent litter characteristics. In total, sows after their first (N = 41) and second (N = 15) lactation were used. One week before weaning, the sows were allocated to the seven treatments based on the number of piglets and BW loss from farrowing until 1 week before weaning. Pre-mating diets did not affect litter characteristics at subsequent farrowing. However, at subsequent farrowing, sows after their first lactation had a lower total number of piglets born per litter (18.3 v. 20.3), higher mean piglet birth weight (1 365 v. 1 253 g), lower CV of birth weight (20.0 v. 26.1%) and lower percentage of piglets < 1 000 g (11.5 v. 24.4%) than sows after their second lactation. Litter weight at second parturition was positively related to IGF-1 during the WEI after first lactation (P < 0.04). Within parity, piglet mean birth weight was positively related to IGF-1 at oestrus (P < 0.02). Surprisingly, within parity, a higher relative loin muscle depth loss during previous lactation was related to lower CV and SD of birth weight (P < 0.05, for both). In conclusion, pre-mating diets did not affect litter characteristics at subsequent birth. However, a higher IGF-1 concentration during the WEI was positively associated with subsequent litter weight and piglet mean birth weight. Further studies should elucidate the role of IGF-1 during the WEI for subsequent litter characteristics and dietary interventions to stimulate IGF-1.     

Intrauterine growth retarded progeny of pregnant sows fed high protein:low carbohydrate diet is related to metabolic energy deficit

High and low protein diets fed to pregnant adolescent sows led to intrauterine growth retardation (IUGR). To explore underlying mechanisms, sow plasma metabolite and hormone concentrations were analyzed during different pregnancy stages and correlated with litter weight (LW) at birth, sow body weight and back fat thickness. Sows were fed diets with low (6.5%, LP), adequate (12.1%, AP), and high (30%, HP) protein levels, made isoenergetic by adjusted carbohydrate content. At -5, 24, 66, and 108 days post coitum (dpc) fasted blood was collected. At 92 dpc, diurnal metabolic profiles were determined. Fasted serum urea and plasma glucagon were higher due to the HP diet. High density lipoprotein cholesterol (HDLC), %HDLC and cortisol were reduced in HP compared with AP sows. Lowest concentrations were observed for serum urea and protein, plasma insulin-like growth factor-I, low density lipoprotein cholesterol, and progesterone in LP compared with AP and HP sows. Fasted plasma glucose, insulin and leptin concentrations were unchanged. Diurnal metabolic profiles showed lower glucose in HP sows whereas non-esterified fatty acids (NEFA) concentrations were higher in HP compared with AP and LP sows. In HP and LP sows, urea concentrations were 300% and 60% of AP sows, respectively. Plasma total cholesterol was higher in LP than in AP and HP sows. In AP sows, LW correlated positively with insulin and insulin/glucose and negatively with glucagon/insulin at 66 dpc, whereas in HP sows LW associated positively with NEFA. In conclusion, IUGR in sows fed high protein:low carbohydrate diet was probably due to glucose and energy deficit whereas in sows with low protein:high carbohydrate diet it was possibly a response to a deficit of indispensable amino acids which impaired lipoprotein metabolism and favored maternal lipid disposal.     

Growth and development of offspring following supplementation of sow diets with oil during mid to late gestation

This study aimed to determine the consequences of altering the fatty acid profile of sow diets during mid-to-late gestation; oils of different fatty acid composition were chosen as energy supplements to provide diets with different fatty acid profiles. Forty-eight multiparous sows were used to evaluate the effects of fat supplementation from day 60 of gestation until parturition. Sows were allocated to either 3 kg/day of commercial sow pellets (control; C) or an experimental diet consisting of 3 kg/day of commercial sow pellets supplemented with 10% extra energy in the form of excess pellets (E), palm oil (P), olive oil (O), sunflower oil (S) or fish oil (F). From days 0 to 60 of gestation, all sows were given 3 kg/day of sow pellets as for the C group. The E diet resulted in the heaviest piglets at birth whereas the offspring of O and S sows were the lightest at birth. The offspring of S sows remained lighter throughout the pre-weaning period, and were also the leanest by 14 days of age. In contrast, pigs born to S sows possessed more fat by the time they reached commercial end point (≈140 days of age). In conclusion, altering the fatty acid profile of the sow diet during the second half of gestation has long-term consequences for the development of their offspring.     

The influence of parity order and body condition and serum hormones on weaning-to-estrus interval of sows.

This study was performed to investigate the weaning-to-estrus interval (WEI) in primiparous and multiparous sows in relation to their weight and back-fat thickness changes and serum hormone imbalance (insulin, growth hormone, and cortisol) at the end of gestation and during lactation. Ten primiparous and ten multiparous Camborough sows, fourth to seventh parity, were used in this experiment. During gestation, daily food intake was 2.4 kg (sow commercial diet: 2.96 Mcal/kg, 16% crude protein) and during lactation all sows were fed on a wet commercial diet (3.34 Mcal/kg, 17% crude protein) ad libitum, three times per day. Blood samples were collected and back-fat thickness at the P(2) site were recorded at 6 days before and 2, 7, 14, 21 and 25 days after farrowing. Body weight was recorded on the same dates, except the date before farrowing. The WEI was also recorded. The average daily feed intake was different (P<0.05) between primiparous and multiparous sows during lactation (5.23 versus 5.72kg per day, respectively). There was a difference (P<0.05) between primiparous and multiparous sows in total percentage of back-fat thickness loss from the end of gestation until weaning (-20.18 and -9.03%, respectively). The total percentage of weight loss during lactation was slightly greater (P>0.05) in multiparous than primiparous sows. Weaning-to-estrus interval was greater (P<0.05) in the primiparous group when compared with the multiparous group (5.55 and 4.22 days, respectively). No differences were found in insulin, growth hormone (GH), and cortisol concentrations between parity groups, except on the 21st day of lactation, when GH was greater in primiparous sows. There was no correlation between percentage of total weight loss and WEI, or percentage of back-fat thickness loss (total or by periods) and WEI. There were positive correlations between GH serum concentration on the 14th and 21st days and the percentage of weight loss in the third week of lactation (r=0.46, P<0.04 and r=0.52, P<0.02, respectively), and between GH concentration on the 21st and on weaning days and WEI (r=0.54, P<0.02 and r=0.42, P<0.06, respectively). Our results indicate that the hormone change (imbalance) during lactation, mainly GH, seems to be a better parameter to explain the difference in WEI between primiparous and multiparous sows than change in body condition.     

Responses to n-3 fatty acid (LCPUFA) supplementation of gestating gilts,and lactating and weaned sows

Feeding n-3 long-chain polyunsaturated fatty acids (LCPUFA) to gilts or sows has shown different responses to litter growth, pre-weaning mortality and subsequent reproductive performance of the sow. Two hypotheses were tested: (1) that feeding a marine oil-based supplement rich in protected n-3 LCPUFAs to gilts in established gestation would improve the growth performance of their litters; and (2) that continued feeding of the supplement during lactation and after weaning would offset the negative effects of lactational catabolism induced, using an established experimental model involving feed restriction of lactating primiparous sows. A total of 117 primiparous sows were pair-matched at day 60 of gestation by weight, and when possible, litter of origin, and were allocated to be either control sows (CON) fed standard gestation and lactation diets, or treated sows (LCPUFA) fed the standard diets supplemented with 84 g/day of a n-3 LCPUFA rich supplement, from day 60 of first gestation, through a 21-day lactation, and until euthanasia at day 30 of their second gestation. All sows were feed restricted during the last 7 days of lactation to induce catabolism, providing a background challenge against which to determine beneficial effects of n-3 LCPUFA supplementation on subsequent reproduction. In the absence of an effect on litter size or birth weight, n-3 LCPUFA tended to improve piglet BW gain from birth until 34 days after weaning (P = 0.06), while increasing pre-weaning mortality (P = 0.05). It did not affect energy utilization by the sow during lactation, thus not improving the catabolic state of the sows. Supplementation from weaning until day 30 of second gestation did not have an effect on embryonic weight, ovulation rate or early embryonic survival, but did increase corpora lutea (CL) weight (P = 0.001). Eicosapentaenoic acid and docosahexaenoic acid (DHA) levels were increased in sow serum and CL (P < 0.001), whereas only DHA levels increased in embryos (P < 0.01). In conclusion, feeding n-3 LCPUFA to gilts tended to improve litter growth, but did not have an effect on overall subsequent reproductive performance.     

Peripartum Ca and P homeostasis in multiparous sows fed adequate or excess dietary Ca

The recent increased prevalence of uterine prolapses in sows around parturition has led to inferences that the prolapses may be associated with hypocalcemia. However, limited data are available to support that hypocalcemia occurs in sows. Hypocalcemia in dairy cows is associated with feeding excess dietary Ca during late gestation. The excess Ca is assumed to suppress homeostatic mechanisms critical to maintain serum Ca concentrations as the Ca demand increases during the early stages of lactation. In this experiment, sows were fed diets with excess Ca during late gestation and early lactation to assess the potential development of hypocalcemia in the peripartum period. Twelve crossbred (Large White × Landrace) multiparous gestating sows were fed a control diet (CON), 0.65% Ca to 0.38% standardized total tract digestible P (STTD P) and 0.67% Ca to 0.38% STTD P in gestation and lactation diets, respectively) or a high Ca diet (HCa, 1.75% Ca to 0.46% STTD P and 1.75% Ca to 0.45% STTD P in gestation and lactation diets, respectively). The diets were fed from gestation day 86 þ ± 1 until the end of lactation (27 þ ± 2 days period). On day 112 of gestation, indwelling venous catheters were placed in each sow. Blood samples were collected at 15-min intervals within four designated times (0700, 1000, 1300 and 1700 h) on gestation day 113 and lactation days 1, 3 and 5. Venous blood pH, gases (pO₂, pCO₂ and HCO₃⁻), electrolytes (K⁺, Na⁺ and Cl⁻), ionized Ca (iCa), metabolites (glucose and lactate), plasma total Ca (tCa), and P were analyzed. Overall, sows fed HCa diet had greater (P < 0.001) concentrations of blood iCa and plasma tCa than sows fed CON diets. No clinical signs of Ca metabolism disorders were observed. Unexpectedly, concentrations of plasma P in sows fed HCa diets were lower (P < 0.001) than in sows fed CON diets. Plasma P tended to decrease (P = 0.057) as day of lactation increased. Differences between dietary treatments for blood pH, gases, electrolytes and metabolites were not detected (P > 0.05). No evidence for hypocalcemia was detected in peripartum sows fed CON or HCa diets. These data imply that excess Ca in late gestation diets did not result in hypocalcemia during the peripartum period. Future experiments should focus on factors other than hypocalcemia to identify causes of uterine prolapses in sows.     

Effects of high dietary fibre diets formulated from by-products from vegetable and agricultural industries on plasma metabolites in gestating sows

The aim of the present study was to examine the biochemical influence of feeding high dietary fibre (DF) diets formulated from by-products from the vegetable and agricultural industries to sows during early to mid-gestation. The effect of feeding frequency (once vs. twice daily) on diurnal plasma metabolites patterns was also examined. The study included a total of 48 gestating sows from four blocks (12 gestating sows in each block). The sows were fed four different diets containing varying levels of starch (304-519 g/kg dry matter (DM)) and DF (171-404 g/kg DM) but with equal amounts of net energy. The low-DF diet (control) was based on barley and wheat, and the three high-DF diets formulated by replacing barley and wheat by pectin residue, sugar beet pulp and potato pulp, respectively. The experimental design comprised two periods of 4 weeks each. Half the sows were fed once daily at 08:00 h in the first period and twice daily at 08:00 and 15:00 h during the second period, and vice versa for the other half of the sows. Plasma samples from vena jugularis were collected by venipuncture at 07:00, 09:00, 12:00 and 19:00 h. Feeding high-DF increased plasma short-chain fatty acids (p = 0.02) and non-esterified fatty acids (p < 0.001). However, there was no clear effect of DF on glucose and insulin responses. A negative correlation between amount of DF in the diets and plasma creatine (R2 = 1.00; diet effect: p = 0.02) suggested that plasma creatine concentrations was an indicator for the level of glucose-glycogen interchange. Furthermore, an explorative approach using nuclear magnetic resonance spectroscopy-based metabonomics identified betaine (p < 0.001), dimethyl sulfone (DMSO2; p < 0.001) and scyllo-inositol (p < 0.001) as biomarkers for the different by-products; pectin residue was related to high plasma levels of DMSO2, sugar beet pulp to plasma betaine, DMSO2 and scyllo-inositol, and potato pulp to plasma DMSO2 and scyllo-inositol. In conclusion, replacing starch by DF affected surprisingly few metabolites in peripheral plasma. No negative effects were found in feeding pectin residue, sugar beet pulp or potato pulp for gestating sows as judged from the minor metabolic changes.     

Effects of different amounts and type of diet during weaning-to-estrus interval on reproductive performance of primiparous and multiparous sows

During weaning-to-estrus interval (WEI), the sows are usually fed with high feed level to improve the reproductive performance. However, the WEI has been reduced over the years which may reduce the impact of feed level on performance in the modern genetic lines. The aim of this study was to evaluate the effect of two feeding levels (moderate feeding level (MFL): 2.7 kg/day and high feeding level (HFL): 4.3 kg/day) and two diet types (gestation: 13.67 MJ/kg of metabolizable energy (ME) and 0.62% of standard ileal digestible lysine (SID Lys) and lactation: 14.34 MJ ME/kg and 1.20% of SID Lys) offered during the WEI on reproductive performance. In total, 19.0% of sows were excluded from the analysis due to feed intake below 75% (9.6% and 28.5% in MFL and HFL groups, respectively), remaining 254 primiparous and 806 multiparous sows. Follicular size and change in BW were measured in subsamples of 180 and 227 females, respectively. Data were analyzed considering the sow as the experimental unit. Feeding level, diet type, parity and their interactions were included as fixed effects, whereas the day of weaning was considered as a random effect. The feed intake of MFL and HFL groups averaged 2.5 ± 0.02 and 3.8 ± 0.02 kg/day, respectively. There was an interaction between feeding level and parity for daily feed intake. Within HFL, multiparous sows consumed 181 g/day more than primiparous sows (P < 0.01), but no difference was observed within MFL (P > 0.05). Both primiparous and multiparous sows lost proportionally less weight when fed HFL than MFL gestation diet during WEI. The percentage of weight loss was lower in HFL than in the MFL group in multiparous sows fed the lactation diet. The WEI was not affected by feeding level, diet type or its interaction (P > 0.05), but it was longer in primiparous than in multiparous sows (P = 0.001). There was no effect of feeding level, diet type, parity or their interactions on anestrus and farrowing rates. Multiparous sows showed greater follicular size, and greater numbers of total born and born alive piglets in the subsequent cycle than primiparous sows (P < 0.05). In conclusion, feeding weaned primiparous and multiparous sows with 4.3 kg/day of a gestation (58.78 MJ ME and 26.66 g SID Lys) or a lactation diet (61.66 MJ ME and 51.60 g SID Lys) does not improve follicular size and reproductive performance in the subsequent cycle.     

Embryo survival, progesterone profiles and metabolic responses to an increased feeding level during second gestation in sows

This study describes reproductive and metabolic responses in sows fed at two different feeding levels from day 3-35 of second gestation. After insemination, 37 sows were assigned to one of two treatments: 1) Control: 2.5 kg/day of a gestation diet; 2) Plus Feed 3.25 kg/day of a gestation diet (+30%). Sow weight, back fat and loin muscle depth were measured at farrowing, weaning, start of treatment, day 14 after start treatment and end of treatment. Frequent blood samples were taken for progesterone, luteinizing hormone (LH), glucose and insulin, insulin-like-growth-factor-1 (IGF-1), non-esterified-fatty-acids (NEFA) and urea analysis. At day 35 after insemination sows were euthanized and their reproductive tract collected to assess ovarian, embryonic and placental characteristics. Plus Feed sows gained 5.4 kg more weight and 0.9 mm more back fat and tended to be heavier at slaughter compared to Control sows (193 vs. 182 kg, P = 0.06). No difference in loin muscle gain was found. Treatment also did not affect vital embryonic survival, which was 72.1 ± 3.9% for Control and 73.4 ± 3.2% for Plus Feed sows, resulting in, respectively, 15.9 ± 0.9 and 15.7 ± 0.7 vital embryos. No effect of treatment on any of the ovarian, embryonic or placental characteristics was found. Progesterone profiles during the first month of gestation, and LH characteristics at day 14 of gestation were not different between treatments. Progesterone concentration was lower (P < 0.05) 3 h after feeding compared with the prefeeding level on days 7-11 after first progesterone rise for Plus Feed and on days 8-10 after first progesterone rise for Control sows. At day 15, preprandial glucose and insulin concentrations were not different between treatments, insulin peaked later (48 vs. 24 min) and at a higher concentration in Plus Feed than in Control sows. Furthermore, glucose area under the curve (AUC) tended to be lower (−171.7 ± 448.8 vs. 1257.1 ± 578.9 mg/6.2 h, P = 0.06, respectively) for Plus Feed vs. Control sows. IGF-1 concentration was not different between treatments, but NEFA concentrations were lower for Plus Feed vs. Control sows (149.5 ± 9.2 vs. 182.4 ± 11.9 μm/L, respectively, P = 0.04) and urea concentration tended to be higher in Plus Feed than in Control sows (4.3 ± 0.1 vs. 3.9 ± 0.1, respectively, P = 0.13). None of the metabolic parameteres were related to reproductive measures. In conclusion, feeding 30% more feed from day 3 till d 35 of second gestation increased weight gain and resulted in lower NEFA concentrations, but did not affect progesterone, LH or IGF-1 and embryonic and placental characteristics.     

Digestion, rumen fermentation and circulating concentrations of insulin, growth hormone and IGF-1 in steers fed diets based on different proportions of maize silage and grass silage

Replacing grass silage with maize silage results in a fundamental change in the ratio of structural to non-structural carbohydrates with commensurate changes in rumen fermentation patterns and nutrient utilisation. This study investigated the effects of feeding four forage mixtures, namely grass silage (G); 67 g/100 g grass silage + 33 g/100 g maize silage (GGM); 67 g/100 g maize silage + 33/100 g grass silage (MMG); maize silage (M) to four ruminally and duodenally canulated Holstein Friesian steers. All diets were formulated to be isonitrogenous (22.4 g N/kg DM) using a concentrate mixture. Dietary dry matter (DM) and organic matter (OM) digestibility increased with ascending maize silage inclusion (P < 0.1) whereas starch and neutral detergent fibre digestibility declined (P < 0.05). Ratio of non-glucogenic to glucogenic precursors in the rumen fluid increased with maize silage inclusion (P < 0.01) with a commensurate reduction in rumen pH (P < 0.05). Mean circulating concentrations of insulin were greatest and similar in diets MMG and GGM, lower in diet M and lowest in diet G (P < 0.01). There were no effects of diet on the mean circulating concentration of growth hormone (GH), or the frequency, amplitude and duration of GH pulses, or the mean circulating concentrations of IGF-1. Increasing levels of DM, OM and starch intakes with the substitution of grass silage with maize silage affected overall digestion, nutrient partitioning and subsequent circulating concentrations of insulin.     

Treatment of lactating sows with the dopamine agonist Cabergoline: effects on LH and prolactin secretion and responses to challenges with naloxone and morphine

This study was conducted to examine the effects of chronic administration of a long-acting dopamine agonist, Cabergoline, on LH and prolactin secretion during lactation in the sow. The effect of the administration of the opioid antagonist naloxone and the agonist morphine in Cabergoline treated animals was also evaluated. In Part I of the experiment, 16 sows were treated as either CONT sows (n=4; control, no treatment); CAB sows (n=4; treated with Cabergoline from days 10 to 26 of lactation); CAB+NAL sows (n=4; received Cabergoline treatment and naloxone challenges); CAB+MORP sows (n=4; treated with Cabergoline and morphine challenges). Plasma LH and prolactin concentrations were measured in blood samples taken from all sows during 6-h periods at days 12, 19 and 26 of lactation. To extend the results at the most critical response period at day 26, another 11 sows were allocated in Part II to either Control (n=3), Cabergoline (n=4) or Cabergoline and morphine (n=4) treatments as for Part I, but the effect of treatments were only confirmed in a single period of sampling at day 26 of lactation. Cabergoline treatment alone increased (P<0.001) mean plasma LH concentrations at day 26 but not at days 12 and 16 of lactation. In contrast, naloxone challenges given in the presence of Cabergoline treatment increased (P<0.05) mean LH at days 12 and 19 of lactation but not at day 26. Morphine challenges in the presence of Cabergoline treatment decreased (P<0.05) mean LH concentrations only at day 26 of lactation, but did not completely reverse the effect of Cabergoline. No treatment differences in plasma oestradiol-17β were detected at any time. Plasma prolactin decreased (P<0.001) in response to treatment with Cabergoline but there were no additional effects of naloxone or morphine. These data provide evidence for the existence of dopaminergic and opioidergic regulation of LH secretion in lactation in the sow and the relative influence of these systems changes as lactation progresses. Furthermore, the data suggest that the stimulatory effect of Cabergoline treatment on LH secretion in late lactation may be mediated by its effects on an inhibitory opioidergic mechanism. Finally, the data provide conclusive proof that prolactin does not directly influence LH secretion or estrogenic activity of the ovary during lactation in the sow.     

Studies on the growth of the fetal guinea pig. The effects of nutritional manipulation on prenatal growth and plasma somatomedin activity and insulin-like growth factor concentrations

In guinea pigs between days 41-46 of pregnancy prenatal growth has been manipulated by alteration of nutritional state. Three methods were used. Uterine artery ligation at day 30 of pregnancy depressed fetal growth rate by greater than 50% and was associated with falls in plasma insulin, IGF-1, cortisol, thyroid hormone, glucose, acetate and free fatty acid concentrations and rises in that of IGF-2, glucagon and amino acids. Fetal plasma was inhibitory to sulphate incorporation into pig costal cartilage. Complete food withdrawal from pregnant guinea pigs for 2 days at days 43-44 of pregnancy caused mild fetal growth retardation and similar changes in plasma constituents, except in that plasma IGF-2 concentrations were now depressed and plasma was not inhibitory to sulphate incorporation into pig costal cartilage. Production of hypoglycaemia by 4-times-daily maternal injections of glucose between days 41-46 of pregnancy accelerated fetal growth rate. It also elevated fetal plasma concentrations of insulin, IGF-1, IGF-2, sulphation-promoting activity, thyroid hormones, glucose and free fatty acids and depressed that of glucagon and amino acids. Fetal growth rate during the experimental period showed a good correlation with plasma glucose, insulin and IGF-1 and, to a certain extent, with sulphation-promoting activity. It did not correlate closely with fetal plasma IGF-2 concentration. Hepatic glycogen concentrations showed a good correlation with plasma IGF-2 levels.     

Effect of N,N-dimethylglycine supplementation in parturition feed for sows on metabolism, nutrient digestibility and reproductive performance

The current pilot study assessed the influence of N,N-dimethylglycine (DMG) on insulin sensitivity, glucose and fat metabolism, nutrient digestibility and reproductive performance of sows in the peripartal period. At day 105 of gestation, 25 sows were randomly assigned to the control (n = 13) or the DMG group (n = 12). Sows from the DMG group were supplemented with 1 g DMG/kg feed until day 3 of lactation. After an overnight fast 1 day after farrowing, a blood sample of each sow was drawn. The plasma was analyzed for insulin, glucose, fructosamine, leptin, thiobarbituric acid reactive substances (TBARS), ferric reducing ability of plasma (FRAP), non-esterified fatty acids (NEFA) and triglycerides (TG) and an oral glucose tolerance test was performed. A rectal feces sample was collected and the apparent fecal digestibility (AFD) of crude fat (CFAT), crude protein (CP) and nitrogen-free extract (NFE) was calculated after proximate analyses. Finally, a colostrum sample was collected from each sow and analyzed for the presence of DMG. Reproductive performance parameters were recorded. The results showed an improvement in the AFD of CFAT, CP and NFE when DMG was supplemented. This beneficial effect confirms the hypothesis that DMG acts as an emulsifying agent. The improvement in digestibility in the DMG group was accompanied by a numerical increase in plasma TG (P = 0.067). Plasma NEFA concentrations were not different between treatment groups. DMG supplementation neither affected glucose clearance nor influenced plasma insulin, glucose, fructosamine or leptin levels. TBARS and FRAP also remained unaffected, despite previously reported anti-oxidative properties of DMG. Furthermore, no significant impact on reproductive performance could be recorded. In conclusion, DMG supplementation significantly improved nutrient digestibility. Possible beneficial effects on energy metabolism and reproductive performance of sows should be tested when DMG is supplemented for a longer period of time or at a higher dose.     

Providing the plant extract silymarin to lactating sows: effects on litter performance and oxidative stress in sows

Silymarin is an extract from the plant milk thistle that was shown to have antioxidant and hyperprolactinemic properties. Taking into account the essential role of prolactin for lactating sows and the systemic oxidative stress occurring during lactation, it is of interest to investigate the potential beneficial effects of silymarin on lactating sows. A study was therefore carried out to determine the effects of providing either 1 or 8 g/day of the plant extract silymarin to lactating sows. Sows in first, second or third parity were fed conventional diets during gestation and, at farrowing, were assigned as controls (CTL, n=33), or were fed 1 g/day (SYL1, n=33) or 8 g/day (SYL8, n=33) of silymarin. The silymarin was provided in two equal amounts per day, and was fed throughout a 20-day lactation. The performance of sows and their litters was assessed and circulating concentrations of prolactin (days 7 and 18), urea (days 7 and 18) and oxidative status, via protein carbonyls and superoxide dismutase activity (day 18), were measured in sows. Milk samples were obtained on day 18 to measure standard composition. There was no effect of silymarin (P>0.10) on circulating prolactin or urea, or on oxidative damage to proteins or antioxidant potential in sows. Lactation feed intake, backfat and BW of sows were unaffected by treatment (P>0.10) as was the case for milk composition and piglet growth (P>0.10). Results demonstrate that providing up to 8 g/day of the plant extract silymarin to lactating sows had no beneficial effects in terms of circulating prolactin concentrations or oxidative status of sows, or in terms of performances of sows and their litters.     

Correlation between LH response to challenges with GNRH and naloxone during lactation, and LH secretion and follicular development after weaning in the sows.

The aim of this study was of establishing a correlation between endogenous LH secretion and the magnitude of the LH response to challenges with GnRH and the opioid antagonist naloxone during lactation, and between these characteristics and LH secretion and follicular development after weaning. Sows (n = 9) were sampled for 6 h at day 2 post-partum, for 12 h on day 26 of lactation and for 6 h immediately after weaning at day 27 of lactation. Four hours after the beginning of sampling at day 26 of lactation all sows were injected with 2 mg/kg i.v. of naloxone hydrochloride and 5 h later with 100 microg/sow of GnRH. Follicular development was studied in all sows at slaughter the day after weaning. There was an effect of time (sampling period; P < 0.001) on mean plasma LH, with an increase (P < 0.05) in LH the day after weaning compared to mean LH concentrations during lactation. Naloxone and GnRH treatment both increased (P < 0.05) mean LH concentrations. A positive relationship (r = 0.58, P < 0.01) between mean plasma LH after GnRH and after weaning was established. Although there were differences (P < 0.001) between sows in follicular fluid volume, there were no correlations between mean follicular fluid volume and mean LH concentrations after GnRH or after weaning. These data indicate that the LH response to GnRH during late lactation could be useful predictor of LH activity after weaning. However, none of the measures of endogenous or induced LH secretion were associated with differences in ovarian follicular size after weaning. Direct evidence is therefore still needed for a functional link between differences in LH in lactation and differences in fertility after weaning.     

Lipid composition of lactational diets influences the fatty acid profile of the progeny before and after suckling

The purpose of the present study was to compare the influence of adding no or 8% fat of varying sources (coconut oil, fish oil, rapeseed oil and sunflower oil) to diets for sows 1 week prior to farrowing and during lactation on the composition of fatty acids in plasma and tissues of the progeny while sucking and 3 weeks after weaning from the sow. A control diet without supplemental fat and four diets supplemented with 8% of coconut oil, rapeseed oil, fish oil or sunflower oil were provided to lactating sows (n = 15), and during the post-weaning period the same weaner diet was provided to all piglets (n = 15 litters), which were housed litterwise. The dietary ratio of n-6:n-3 fatty acids of the maternal diets largely influenced the progeny, as the ratio varying from 1.2 (fish oil) to 12.2 (sunflower oil) in the sow milk was reflected in plasma and adipose tissues of the sucking progeny. The liver showed similar variations according to dietary treatments, but a lower n-6:n-3 fatty acids ratio. From day 4 to later on during the suckling period, the concentration of C14:0, C16:0 and C18:1 in the liver of the piglets decreased, irrespective of the dietary treatments of sows. In plasma and liver, the total concentration of saturated fatty acids (SAFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) did not differ markedly in piglets sucking sows fed different dietary fatty acids, whereas the adipose tissue of piglets sucking sows fed sunflower oil and coconut oil showed the highest proportion of PUFA and SAFA, respectively. Weaning lowered the concentration of lipid-soluble extracts in plasma and the concentration of fatty acids in the liver of the piglets. Within the post-weaning period, dietary treatments of sows, rather than age of piglets, influenced the fatty acid composition of plasma and adipose tissue of the piglets, whereas the hepatic fatty acid profile was more affected by the age of the piglets during the post-weaning period. This study shows that the fatty acid profile of plasma and tissues of the progeny is highly dependent on the maternal dietary composition, and that the dietary impact persists for up to 3 weeks after the suckling period.