The effects of feed intake and body fatness on progesterone metabolism in ovariectomized gilts

We studied the effects of feed intake and fatness on metabolic clearance rate (MCR) and half-life of progesterone in 40 ovariectomized gilts (10x4 littermates). One gilt from each litter was randomly allocated to each of four treatments in a randomized block design. Gilts were reared to be either lean (Ln), 113 kg BW and 10 mm backfat measured 65 mm from the midline at the level of the last rib (P2), or fat (F), 124 kg BW and 20 mm P2 backfat. They were ovariectomized and fitted with bilateral jugular catheters. Fat and Ln gilts were then fed either low (1.15 x maintenance energy, L), or high (2.30 x maintenance energy, H) feed intakes. Gilts received an i.m. injection of 130 mg of progesterone on two consecutive days (d1 and 2). From d 3, progesterone was infused at 5.4 mg/h (130 mg/d) for 60 h. Blood samples for progesterone analysis were taken during the last 24 h of infusion and for a further 72 h. Gilts were then slaughtered, and livers were sampled for microsomal studies. Fatness did not affect any aspect of progesterone metabolism measured. Postprandial MCR was greater in H than in L gilts, 103.0 vs. 76.1 mL x min(-1) x kg BW(-1) (P<.01), respectively. Feed intake did not affect the disappearance rate constant of progesterone (mean -.019), and the estimated half-life of progesterone was 36.5 h. High-intake gilts had larger proportional liver size (P<.001) than L gilts. Microsomal metabolism of progesterone and P450 enzyme concentration were similar across treatments. We conclude that increasing feed intake increases MCR of progesterone and could be used to manipulate progesterone concentration in sows.     

The effect of infusion of urea into the vena cava on feed intake of finishing gilts

Three experiments were conducted to evaluate the relationship between feed intake and plasma urea concentration. In Exp. 1, six gilts (BW 53 kg) with catheters in their venae cavae were used in a 5x5+1 Latin square design to determine the amount of infused urea needed to mimic the plasma urea concentration of pigs fed a 25% CP diet. Five gilts were fed a 16% CP corn-soybean meal diet and were infused continuously with either saline or one of four doses of urea (6, 12, 18, and 24 g/d) during each of five periods (12 h/period). Between periods, infusions were stopped for 36 h. The sixth pig was fed a 25% CP diet and infused with saline during each of the experimental periods. Venous blood samples were obtained at 1-h intervals starting 1 h before infusion. As expected, plasma urea concentration increased with increasing amount of urea infused. A daily infusion of 24 g of urea resulted in a plasma urea concentration similar to that of the pig fed the 25% CP diet with saline infusion. In Exp. 2, 12 gilts (BW 60 kg) were used in a crossover design. Pigs received a 16% CP diet and a different treatment (saline or 24 or 30 g/d of urea) in each of three infusion periods. Each infusion period lasted 2 wk. Infusions were stopped for 2 d between periods. Blood samples were obtained before infusion and daily after infusions started. Feeders were weighed daily to determine ADFI. Experiment 3 was similar to Exp. 2, except that only two treatments (saline and 30 g/d of urea) were used. Data from Exp. 2 and 3 were combined for statistical analysis. Plasma urea concentration increased linearly (P<.001) with increasing amount of urea infused. Overall, there was a trend (P<.10) for urea infusion to decrease ADFI, and pigs infused with 30 g/d consumed less (P<.05) feed than pigs infused with saline. Therefore, plasma urea concentration may play a role in regulating feed intake in gilts consuming excess protein.     

Effect of feed intake restriction on reproductive performance and pregnancy rate in Egyptian buffalo heifers

The objective of the present experiment is to study the effect of feed intake restriction on the reproductive performance and pregnancy rate in Egyptian buffalo heifers. Thirty anestrus buffalo heifers were randomly divided into two equal groups. The low feed intake (LFI, n?=?15, 50 % restriction) group was fed a diet that consists of 3 kg concentrate, 1 kg wheat straw, and 3 kg fresh alfalfa, while the high feed intake (HFI, n?=?15) group was fed double the amount given to the LFI group for 4 months. All animals were weighed, transrectally examined, and visually checked for the signs of estrus, and blood samples were collected. Heifers in heat were mated with one fertile bull. The number of heifers showing estrus activity was 93.3 % in HFI vs. 20 % in LFI (P?<?0.01). Ovarian activity started earlier (P?=?0.03) in the HFI than LFI group. The weight at breeding, the diameter of the dominant follicle, number of heifers showing ovulations, number of services per conception, pregnancy rate, and overall mean of progesterone and estrogen concentrations were significantly higher (P?<?0.01) in the HFI than in the LFI group. The level of serum total protein, albumin, globulin, glucose, total cholesterol, and calcium were significantly higher (P?<?0.05) in the HFI group. Restriction of the daily feed intake to 50 % from NRC recommendations impair reproductive performance in terms of increasing the age at first service and reducing the pregnancy rate in buffalo heifers. In conclusion, feed intake could be effective in improvement of reproductive performance in buffalo heifers and further studies should be done on large scale of buffaloes in this point.     

The influence of high-nitrogen forages on the voluntary feed intake of sheep

The objective of this research was to examine the effect of high concentrations of nonprotein nitrogen (NPN) on the voluntary food intake of sheep fed high-quality grasses. Wether lambs (n = 6 per treatment) were fed dried switchgrass (Panicum virgatum L.; Exp. 1) or dried tall fescue (Festuca arundinacea Schreb.; Exp. 2). In both experiments, urea was added to the dried forage at 0 (control), 12, or 24 g of N/kg of DM to increase the NPN concentration. Acid detergent fiber concentrations were 305 g/kg of DM in both experiments, although DM digestibility was 663 and 618 g/ kg of DM in Exp. 1 and Exp. 2, respectively. Voluntary feed intake of the control forage was 28.2 and 19.1 g/ kg of BW in Exp. 1 and Exp. 2, respectively, and decreased for the high-urea treatments to 25.2 and 16.2 g/kg of BW in Exp. 1 (P = 0.07) and Exp 2 (P = 0.03), respectively. Total feed N concentrations increased from 29.5 g to 45.7 g of N/kg of DM in Exp. 1 (P < 0.01) and from 28.4 to 55.9 g of N/kg of DM in Exp. 2 (P < 0.01). Nonprotein N concentrations increased from 28.3 to 53.8% of the total N in switchgrass diets (Exp. 1; P < 0.01), and from 26.4 to 64.0% in tall fescue diets (Exp. 2; P < 0.01). Plasma urea concentrations of the lambs increased from 3.1 to 6.6 mM (Exp. 1; P < 0.01) and from 2.9 to 5.8 mM (Exp. 2; P < 0.01) as the amount of urea added to the diets increased. These changes resulted in an increase in plasma osmolality from 298 to 307 mOsm/kg (Exp. 1; P = 0.04), and from 299 to 307 mOsm/kg (Exp. 2; P = 0.06). Increasing feed N and NPN concentrations through the addition of urea caused a significant decrease in the voluntary feed intake of sheep fed tall fescue and switchgrass. These responses showed no significant cause-and-effect relationship between voluntary feed intake, plasma urea concentrations, and plasma osmolality.     

Effects of vitamin A and beta-carotene on reproductive performance in gilts

The effects of vitamin A and beta-carotene on various reproductive parameters were examined in 108 crossbred gilts. Gilts were fed a diet free of vitamin A and beta-carotene for 5 wk, then assigned to one of eight treatments. Statistical comparisons were performed on three sub-groupings of these treatments as follows: (1) DEFICIENT (received 2,100 IU of vitamin A X head-1 X d-1, (2) FED (received dietary supplementation of 0, 2,100 or 12,300 IU vitamin A and (or) 0, 32.6 or 65.2 mg beta-carotene X head-1 X d-1) or (3) INJECTED (received injection supplementation of 0 or 12,300 IU vitamin A and 32.6 mg beta-carotene X head-1 X d-1, administered once weekly). Gilts remained on treatment through weaning of litters at 21 d postpartum. Plasma vitamin A and beta-carotene levels were greatly elevated in INJECTED gilts. Concentrations of these compounds in plasma were similar between DEFICIENT and FED gilts. There was no treatment difference in number of corpora lutea/gilt. Embryonic mortality was lowest (P less than .01 to .02) in INJECTED gilts (14 +/- 3%) compared with DEFICIENT (29 +/- 5%) or FED (25 +/- 3%) gilts. Baby pig mortality averaged 6 +/- 1% and was not different among treatments. INJECTED gilts had more (P less than .05 to .01) piglets/litter at birth and at weaning (9.5 +/- .3 and 9.0 +/- .3 piglets/litter, respectively) than DEFICIENT (7.9 +/- .5 and 7.6 +/- .5 piglets/litter) or FED gilts (8.7 +/- .3 and 8.1 +/- .3 piglets/litter).(ABSTRACT TRUNCATED AT 250 WORDS)     

Consequences of different patterns of feed intake during the estrous cycle in gilts on subsequent fertility

The impact of different patterns of feed restriction between d 1 and 15 of the estrous cycle on subsequent reproductive performance of 23 trios of littermate gilts was tested. Some gilts were fed a high plane of nutrition (HH gilts) throughout the cycle, in contrast to HR gilts, which were restricted from d 8 to 15, and RH gilts, which were restricted from d 1 to 7. During feed restriction, weight gain in RH gilts (2.5 +/- .7 kg) was lower (P = .006) between d 1 and d 7 than in their HH and HR littermates (5.6 +/- .7 and 5.6 +/- .8 kg, respectively) and it was lower (P = .0001) in HR gilts (5.5 +/- .5 kg) between d 8 to d 15 than in their HH and RH counterparts (8.5 +/- .4 and 9.4 +/- .5 kg, respectively). There were no differences in backfat changes among groups. Embryonic survival in HR gilts at d 28 of gestation (68.3 +/- 4.8%) was lower (P < .05) than in HH and RH gilts (83.6 +/- 4.3 and 81.7 +/- 4.5%, respectively). Plasma progesterone concentrations in HR gilts were lower (P < .05) at 48 and 72 h after onset of standing estrus (.82 +/- .2 and 3.6 +/- .5 ng/mL, respectively) than in HH and RH gilts (1.44 +/- .2 and 1.24 +/- .2 ng/mL, 5.0 +/- .4 and 5.0 +/- .5 ng/mL, respectively at 48 and 72 h). No differences in ovulation rate were observed among treatments. Placental area was positively correlated to embryo size at d 28 (embryo size = .0003 x (area) + 18.35; r = .28, P = .03) but placental volume was negatively correlated to the number of embryos in utero (placental volume = -4.317 x (number) + 207.55, r = -.39, P = .002). These data demonstrate that the timing of feed restriction during follicular development has important consequences for subsequent embryo survival, possibly mediated by differences in progesterone concentrations in early pregnancy.     

Effect of feed intake during late development on pubertal onset and resulting body composition in crossbred gilts.

A total of 105 nonboar-exposed, F2 ([Landrace x Yorkshire] x Duroc) gilts were used in two replicates of a randomized complete block experiment to evaluate the effect of dietary feed intake on pubertal onset and subsequent body composition. Feed intakes were established at 50% of ad libitum (AL-50), 75% of ad libitum (AL-75), or at ad libitum (AL-100) levels from 4.5 to 9 mo of age. A corn-soybean meal diet fed to all gilts was formulated to meet or exceed nutrient requirements except for energy. Puberty was measured by two methods: 1) monitored once daily by back pressure applied by the herdsman or 2) from elevated plasma progesterone concentrations. Body composition was evaluated by the deuterium oxide method after plasma progesterone concentrations were elevated. Daily feed intake for the experimental period averaged 1.6, 2.3, and 3.2 kg, and the BW of gilts at 8 mo of age were 111, 131, and 154 kg for the AL-50, AL-75, and AL-100 groups, respectively. Body weight, backfat thickness, and body fat content increased linearly (P < .01) as feed intake increased, but age at puberty was not severely influenced. A minimum body fat content or percentage did not seem to initiate pubertal onset. There was a trend for a lower percentage of the AL-50 gilts to ovulate (P = .08) than those fed the AL-75 and AL-100 intakes. An inverse relationship resulted between the percentage of gilts that ovulated to the percentage that showed behavioral estrus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of protein intake, energy intake and stage of gestation on growth, reproductive performance, nitrogen balance and carcass composition in gestating gilts

Thirty-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P less than .01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P less than .05 and linear effect, P less than .01, respectively). Nitrogen retention (P less than .01), efficiency of N retention (P less than .05) and dry matter digestibility (P less than .01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P less than .01), liver weight (linear effect P less than .01) SM weight (quadratic effect, P less than .05) and SM percentage M (linear effect P less than .10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P less than .10, P less than .05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.     

Effect of levamisole on immune function and reproductive performance in first-litter gilts

First-litter commercial cross-bred gilts were treated with levamisole (1.5, 2.5, or 3.5 mg/kg of body weight) weekly during the last 4 weeks of gestation, because similar treatment of dairy heifers had improved postpartum maternal health and neonatal survival. In the gilts, differences in reproductive performance were not found on the basis of pig survival at birth, pig survival at weaning, birth weight, or weaning weight. Also, differences between treated and control gilts were not found in response of circulating lymphocytes to mitogen stimulation (phytohemagglutinin A, concanavalin A, and pokeweed mitogen). In all gilts, the lymphocyte response to mitogen stimulation was decreased during the first week after farrowing.     

Effect of sex ratio of the birth litter on subsequent reproductive performance of gilts

Records on age at puberty from 1,555 gilts and total number of pigs born in litters of 1,187 gilts from the Nebraska gene pool population were used to evaluate the effects of uterine environment on subsequent reproductive performance. Independent variables were line, year, line x year, proportion of males in the birth litter (sex ratio), number born in the birth litter (fraternity size) and sex ratio x fraternity size. Sex ratio, fraternity size and their interaction influenced age at puberty (P less than .01) but not number born (P greater than .2). Partial regression coefficients indicated that age at puberty tended to decrease as sex ratio increased, particularly in small litters. Although the regression coefficients were relatively large, sex ratio, fraternity size and their interaction accounted for only 1.3% of the variation in age at puberty within line x year subclass. These results offer little encouragement for the use of sex ratio as a phenotypic selection criterion for improvement of reproductive performance in gilts. Results suggest that female swine are similar to rodents in response to uterine environmental effects.     

Impact of selection for residual feed intake on breeding soundness and reproductive performance of bulls on pasture-based multisire mating

There is concern in the beef industry that selecting bulls for feed efficiency based on residual feed intake (RFI) may have a negative impact on bull reproductive performance and fertility. Here we investigated the impact of selection of bulls for low RFI on breeding soundness evaluation (BSE), reproductive performance, and fertility of bulls under natural service in multisire mating groups on pasture. Of the 412 RFI-tested bulls available, 98 (23.8%) were culled for performance, type, temperament, or other reasons, and 88 (21.4%) were culled for failing BSE, for an overall cull rate of 45.1%. From among the 314 bulls subjected to BSE, 32 (10.2%), 20 (6.4%), and 36 (11.4%) were culled for poor feet and legs, scrotal circumference, and semen quality, respectively. The BSE traits were not different (P > 0.10) between bulls categorized as either inefficient (+RFI) or efficient (-RFI), but the proportion of bulls that failed to meet the 60% minimum sperm motility requirement tended (P = 0.07) to be greater in the -RFI group than in the +RFI group (10.2% vs. 4.4%, respectively). In a subpopulation of 115 bulls, individual progressive sperm motility was greater (P < 0.05) in +RFI (85%) than -RFI (80%) bulls. A multisire natural mating experiment was conducted during 2 consecutive breeding seasons (2006 to 2007 and 2007 to 2008) using 18 +RFI and 18 -RFI bulls. The overall calving rate (calves born/cows exposed) was 72.9%. Mean number of progeny per sire was significantly greater (P < 0.01) in -RFI bulls (18.3) than in +RFI bulls (11.8). Selection for feed efficiency based on RFI appears to have no detrimental impact on reproductive performance and fertility in beef bulls bred in multisire groups on pasture. However, the decreased sperm motility and the greater number of progeny per sire associated with -RFI status need further investigation.     

The influence of prepartal bacteriuria on the reproductive performance of the sow

In a Slowakian indoor pig production unit, with high prevalence of vaginal-vulval discharges, the sows were subjected one day prefarrowing to urine analysis. Sows suffering urinary tract infection (UTI) were assigned to an UTI group (group 1, n = 384), the remaining sows were classified as free of UTI and were assigned to group 2 (n = 1099). Total born litter size, liveborn litter size, weaning litter size and the occurrence of periparturient diseases, reasons for sow cullings at weaning, subsequent weaning to estrus intervals, conceptions- and farrowing rate, next total born- and lifeborn litter size and the occurrence of periparturient diseases were evaluated. UTI having sows had smaller (p < 0.05) total born litter size (11.71 +/- 1.11) when compared to the healthy animals (12.97 +/- 1.25). Liveborn litter size was significantly (p < 0.01) lower in group 1 (10.21 +/- 0.81 vs. group 2: 11.31 +/- 1.21). The occurrence of periparturient diseases revealed highly significant (p < 0.001) differences between the groups (group one 26.24% vs. group two 4.64%). Weaning litter size showed significant (p < 0.05) differences between group 1 (9.21 +/- 1.02) and 2 (10.11 +/- 0.37). More (p < 0.05) sows were culled post-weaning in the UTI group, compared to the healthy animals. Causes of post-weaning cullings differed between the groups: all sows of the group one had the pathological signs of swine urogenital disease at culling, while the majority of sows of the group 2 were culled due to locomotor problems and chronic mastitis. Subsequent weaning to estrus intervals, conceptions-, and farrowing rate and next total born litter size differed significantly (p < 0.05) between the groups, next lifeborn litter size (p < 0.01) and the occurrence of periparturient diseases (p < 0.001) were high significantly better in the healthy than in the UTI suffering group of sows. Implications: antepartal UTI might be the sign of swine urogenital disease and might negatively influence the sows reproductive performance.     

Effect of postnatal nutritional status on subsequent growth and reproductive performance of gilts

Two trials involving 128 gilts were conducted to determine the effect of nutritional status during the first 28 d postnatally on subsequent growth and reproductive performance. Nutritional status was altered by adjusting litter size at birth to either 6 or 12 pigs and maintaining a lactation length of either 13 or 28 d. Pigs weaned at d 13 were fed on an ad libitum basis or at 50% of ad libitum through d 28. After d 28, all pigs were fed the same diets through the first parity. By market weight (d 154) pigs recovered differences in body weight imposed during the early postnatal period. Postnatal nutritional status did not alter age at puberty. Gilts weaned at d 28 from litter size 6 produced 2.4 more (P less than .05) ova than gilts from litter size 12; however, when weaned at d 13, gilts from litter size 6 produced 2.3 fewer ova than gilts from litter size 12. Feed restriction for 15 d postweaning did not depress ovulation rate in gilts. Subsequent litter size was not affected by postnatal litter size, lactation length or feed restriction, even though growth rate and ovulation rate had been altered by treatments imposed during the first 28 d postnatally. Assuming no difference in fertilization, these data suggest that prenatal mortality was altered by the early postnatal treatments and was the limiting factor for litter size. Until factors that influence prenatal losses are characterized and controlled, the alteration of nutritional status by changes in postnatal litter size, lactation length or feeding level will not detrimentally affect subsequent litter size in gilts.     

Effect of feed intake and dietary vitamin A levels on sheep performance.

A study was conducted on 20 "Rahmani" male lambs of 16 kg body weight fed on normal feed level and high vitamin A level (NF-HV); normal feed level and normal vitamin A level (NF-NV); low feed level and high vitamin A level (LF-HV) or low feed level and normal vitamin A level (LF-NV) till slaughter weight of 35-40 kg. Average daily gains of lambs were 211, 148, 117 and 87 g for the NF-HV, NF-NV, LF-HV and LF-NV groups, respectively. The corresponding feed conversions were 4.3, 5.9, 5.0 and 6.4 kg DM/kg gain. Raising feed intake and vitamin A level enhanced nutrients digestibility and nitrogen balance. Rumen liquor reflected higher pH value in animals fed higher intake (NF) in the first two diets. Both feed intake and vitamin A levels enhanced volatile fatty acids and ammonia concentrations in the rumen liquor. Feed intake and vitamin A levels positively affected haemoglobin content, packed cell volume, glucose, urea, total protein, vitamin A, insulin, cholesterol, phospholipids, glutamate oxaloacetate and glutamate pyruvate transaminases and alkaline phosphatase in blood Vitamin A, insulin, cholesterol and phospholipids in blood increased gradually over the experimental period. Dressing percentages were 56.2, 49.6, 49.1 and 44.6% for the experimental groups, respectively. Liver content of glycogen and vitamin A increased with increasing feed intake and vitamin A levels. It is concluded that higher levels of vitamin A supplementation (than usually recommended) is required during fattening of lambs. Low energy and normal vitamin A levels are not recommended in lambs feeding.     

The effect of litter size before weaning on subsequent body development, feed intake, and reproductive performance of young rabbit does

An experiment was performed to study the effect of litter size before weaning on subsequent body development and composition, feed intake, and reproductive performance of young rabbit does with the objective to improve reproductive performance. Litter size (LS) before weaning (treatment) was 6, 9, or 12 kits. After weaning (30 d), 58 female kits per treatment (in two successive replicates) were reared and fed for ad libitum intake to 14.5 wk of age (end of rearing). At 14.5 wk of age, receptive does were inseminated. Nonreceptive and nonpregnant does were inseminated at 17.5 wk of age. The experiment ended when the second litter was weaned. Part of the animals was slaughtered to determine body composition at the end of the experiment (replicate one) and at the end of rearing (replicate two). At weaning, BW differed among treatments (P < 0.05; 855, 773, and 664 +/- 15 g for LS6, 9, and 12, respectively). Compensatory growth was observed. At the end of rearing, LS12 does were smaller (P < 0.05) than LS9 and LS6 does (3,524, 3,778, and 3,850 +/- 48 g, respectively). After first lactation, no difference in BW among treatments was found. Compared with LS6, empty body weight (BW minus gut, bladder, and uterus content) of LS12 contained more (P < 0.05) nitrogen (32.5 vs 31.1 +/- 0.3 g/kg), more (P < 0.05) ash (30.7 vs 28.3 +/- 0.6 g/kg), and less (P < 0.05) fat (168.6 vs 200.2 +/- 8.6 g/kg). No differences in body composition among treatments were found at the end of the experiment. During rearing, LS12 had the lowest (P < 0.05) daily feed intake (152, 164, and 169 +/- 2 g/d for LS12, 9, and 6, respectively). During the reproductive period, no differences in feed intake among treatments were found. Kindling rate (the number of kindlings per number of inseminations) was not influenced by treatment. In the first parity, total litter size (number of alive and stillborn kits) was lower (P < 0.10) for LS12 than for LS9 (6.4 vs 8.6 +/- 0.5, respectively). When first mating was delayed by 3 wk, an increased (P < 0.05) total litter size was found regardless of treatment (7.5 and 9.4 +/- 0.3 for 14.5, and 17.5 wk, respectively). Decreasing litter size before weaning from nine to six kits did not alter future reproductive performance. Based on results of this study, it seems advisable to perform a limited standardization level (at nine kits) after kindling and postpone first mating to an older age (17.5 wk) to improve reproductive performance.     

Effects of deficiency and surplus dietary threonine on reproductive performance of primiparous pregnant gilts

Dietary threonine imbalance is known to impair reproductive performances of gestating sows, but the underlying mechanisms are largely unknown. In this study, effects of deficiency and surplus dietary threonine during gestation on reproductive performance, serum metabolites and hormones concentration, and colostral nutrient and immunoglobulin contents of primiparous sows were investigated. Ninety primiparous pregnant gilts were assigned to one of the three dietary treatments with different standardized ileal digestible threonine/lysine ratios at 0.59, 0.72 and 0.85, which represented deficient (DT), adequate (AT) and surplus (ST) dietary threonine concentration respectively. Maternal body weight gain from day 80–110 of gestation was highest (p < .05) for gilts fed AT than for gilts fed DT or ST. On days 30 and 110, serum threonine concentration increases in a dose‐dependent manner with the increasing of dietary threonine concentration in (p < .01), serum urea nitrogen concentration was lower (p < .01) in gilts fed AT than DT or ST, and serum insulin‐like growth factor‐I (IGF‐I) was lowest (p < .05) for gilts fed DT. On day 110, gilts fed AT had lower serum progesterone concentration but higher concentrations of serum prolactin (p < .05) compared to DT and ST. Concentration of colostral immunoglobulin A and G from gilts fed DT was lower (p < .05) compared with gilts fed AT or ST. In conclusion, gilts with the adequate threonine intake were more able to conserve dietary amino acids to support foetal and maternal tissue gain. Deficient or ST threonine intake may induce a delay in changes in progesterone and prolactin concentrations during the prepartum period impeding the transition from pregnancy to lactation.