Influence of exogenous insulin before breeding on conception rate and litter size of sows

Insulin in the saliva of pigs: Validation of an automated assay and changes at different physiological conditions

This study aimed to evaluate whether insulin could be measured in the saliva of pigs and if its concentration changes in some physiological conditions. For this purpose, a validation of an automated heterologous immunoassay for measuring insulin in the saliva of pigs was performed. In addition, the possible changes of salivary insulin concentration in sows after food intake and during gestation and lactation were studied. The evaluated immunoassay was able to detect insulin in the saliva of pigs in a precise and accurate way when species-specific calibrators were used. There was no correlation in insulin concentrations between serum and saliva. Insulin concentrations showed a significant increase in the saliva of sows after feeding. Sows at farrowing and lactation presented higher salivary insulin levels as compared with those in gestation. In conclusion, the results showed that insulin could be measured in the saliva of pigs, and changes in its concentration can be detected due to food intake and different physiological conditions.

A regional evaluation of chromium tripicolinate supplementation of diets fed to reproducing sows1,2

A cooperative research study involving 353 litters was conducted at three stations to determine the effects of graded levels of supplemental Cr from chromium tripicolinate (CrPic) on reproductive performance of sows and preweaning performance of their pigs. Primiparous and multiparous sows were fed fortified corn-soybean meal diets with supplemental levels of 0, 200, 600, or 1,000 ppb Cr (as-fed basis). Each station used at least three of the supplemental Cr levels, with two of those levels being 0 and 200 ppb. Station effects were observed for sow gestation weight gain, lactation weight change, lactation feed intake, litter size at birth and weaning, and pig weight at birth and weaning (P = 0.001 to 0.087). Supplemental Cr increased the number of pigs born live per litter (9.49, 9.82, 10.94, and 10.07; quadratic, P = 0.05) and sow lactation weight change (-0.2, 0.8, -4.1, and -3.9 kg; linear, P = 0.01) but decreased individual birth weight of total pigs born (1.61, 1.57, 1.47, and 1.56 kg; quadratic, P = 0.10). Tissues were obtained from a subset of sows from one station after they had completed three parities on the study. The content of Cr in the adrenal gland (16.4, 20.0, 34.0, and 48.4 ppb), kidney (35.8, 56.4, 132.6, and 176.0 ppb), and liver (22.8, 37.4, 87.6, and 92.2 ppb) was increased linearly (P = 0.001 to 0.005) by increasing CrPic supplementation. The results suggest that the supplementation level that maximizes the biological response is above that currently allowed. Additionally, supplementation of Cr at 1,000 ppb (five times currently permitted supplementation levels) was not detrimental to sow performance, even when fed continuously for three parities. There may be merit to continued research to evaluate higher supplementation rates.

Feed restriction and insulin treatment affect subsequent luteal function in the immediate postovulatory period in pigs: progesterone production in vitro and messenger ribonucleic acid expression for key steroidogenic enzymes

Progesterone production and release in vitro, and mRNA expression for key steroidogenic enzymes, were studied in luteal tissue recovered in the immediate postovulatory period from cyclic gilts allocated to one of three treatments: moderate feed restriction during the first (RH) or second week of the estrous cycle, with (HR+I) or without (HR) concomitant injections of long-acting insulin. Time of feed restriction affected neither progesterone production or release, nor mRNA expression for several key steroidogenic enzymes. However, luteal tissue from RH but not from HR gilts responded to LH stimulation by increasing progesterone production and release (P: < 0.05). Insulin treatment increased progesterone production and release, restored luteal tissue responsiveness to LH, up-regulated steroidogenic enzyme mRNA expression, and down-regulated the tissue inhibitor of metalloproteinase-I mRNA expression in HR+I compared with HR gilts (P: < 0.05). In vitro progesterone production and gene expression were affected by time of tissue collection after ovulation in RH and HR gilts but not in HR+I gilts, and were correlated with temporal changes in oviductal and peripheral plasma progesterone concentrations. Inherent differences in luteal function therefore appear to mediate latent effects of nutrition and insulin treatment on circulating progesterone concentrations in the critical postovulatory period in gilts.

Effect of insulin on feed intake and reproductive performance of well-nourished nulliparous ewes

Eighty-four nulliparous ewes were used to examine the effect of short-term insulin treatment on feed intake and reproductive performance. Following estrus synchronization, ewes were observed for estrus (= Day 0) and were penned individually beginning on Day 7. Ewes were fed twice daily and feed intake was recorded. On Days 9 through 13, ewes were treated s.c. with 1 IU/kg BW insulin (n = 44) or an equivalent volume of saline (n = 40). On Day 14, ewes were placed with fertile rams and number of ewes in estrus (bred) was recorded. Thirty days post-breeding, ewes were checked for pregnancy via ultrasonography. Feed intake and percentage of ewes in estrus did not differ between saline- and insulin-treated ewes. Similarly, neither pregnancy rate (69 +/- 8.7% vs. 80 +/- 8.1%, respectively) nor lambing rate (61 +/- 8.9% vs. 78 +/- 8.4%, respectively) differed between treatments. The number of lambs born per ewe was, however influenced by a breed-group effect (P < 0.0002). Romanov ewes had more (P < 0.001) lambs than the other breed groups in the study. Therefore, treating well-nourished, nulliparous ewe lambs with insulin did not increase reproductive efficiency, possibly because the ewes were already at a maximal nutritional and/or reproductive state.

The influence of insulin administration after weaning the first litter on ovulation rate and embryo survival in sows

Primiparous crossbred sows (n = 43), lactating for an average of 21.1 +/- 0.1 d and weaning 8.7 +/- 0.1 pigs, were used to evaluate the influence of insulin on ovulation rate and embryo survival. The sows were maintained on 2.3 kg/head/d of a 14% protein gestation diet during pregnancy, fed ad libitum during lactation, given 2.7 kg/head/d from weaning until re-breeding and fed 2.3 kg/head/d after mating. Beginning the day after weaning (Day 0) sows were treated with 0.4 IU/kg body weight (BW) insulin (n = 21) or were administered an equivalent volume of saline (n = 22) for 4 d. Beginning on Day 3 and continuing until Day 14 after weaning, the sows were checked for estrus twice daily and were artificially inseminated using pooled semen from 2 fertile boars. At slaughter (days 30 to 40 of gestation), ovaries and uteri were collected, and the ovulation rate, embryo number and viability, and uterine weight and length were evaluated and recorded. Use of insulin decreased the average interval from weaning to estrus compared with saline by increasing percentage in estrus by Day 14 after weaning (5.0 +/- 0.57 vs 6.9 +/- 0.56 d, respectively; P < 0.03). Ovulation rate, number of embryos, embryo survival, and average uterine length and weight were not influenced by insulin treatment. Overall, insulin affected reproductive efficiency in primiparous sows by increasing the percentage of sows in estrus.

Effect of insulin administration before weaning on reproductive performance in feed restricted primiparous sows

The objective of this study was to determine whether exogenous insulin administration in late can improve reproductive performance of feed restricted primiparous sows. A total of 24 pure Large White gilts were assigned at farrowing to one of the three following experimental groups. Control sows (CTRL) were fed on a plane of nutrition close to ad libitum and received 6 kg food day-1. Restricted saline-treated (RS) and insulin-treated (RI) sows received only 4 kg food day-1. Sows from RI group received 0.4 IU insulin per kg of live weight once daily during the 5-day weaning period, whereas CTRL and RS sows received saline injections as a sham treatment. Litters (8-10 piglets) were weaned at 23.5 +/- 1 days post-partum. Blood samples were collected 2 days before (Day W - 2) and after weaning (Day W + 2). Restricted sows RS and RI lost significantly more weight than CTRL sows (25 kg and 32 kg, respectively, vs. 10 kg) and more fat (5.3 mm and 4.7 mm, respectively, vs. 2.2 mm). During insulin treatment, daily litter weight gain was lower in RI than in RS and CTRL groups (P < 0.05). On Day W - 2, insulin concentration was higher, while that of glucose was lower in RI than in RS and CTRL sows (P < 0.05). Concentrations of NEFA and IGF-I were similar in the three groups of sows. On Day W + 2, concentrations of FSH and oestradiol-17 beta did not differ significantly between females of the different groups. Weaning-to-oestrus interval and ovulation rate were similar in CTRL, RS and RI females (5.7, 5.9 and 5.6 days; 19.2, 20.7 and 22.1 corpora lutea, respectively). We concluded that insulin administration during late lactation to feed-restricted primiparous sows did not improve weaning-to-oestrus interval and post-weaning ovulation rate, but was likely to decrease milk production.