Chemical composition, nitrogen degradability and in vitro ruminal biological activity of tannins in vines harvested from four tropical sweet potato (Ipomoea batatas L.) varieties.

This study investigated the potential of vines from four sweet potato varieties (Tia Nong 57, Tia Nong 66, Ligwalagwala and Kenya) as alternative feed resources for ruminant livestock. The chemical composition [neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP) and acid detergent insoluble nitrogen (ADIN)], in vitro ruminal nitrogen (N) degradability and in vitro ruminal biological activity of tannins in the vines, harvested at 70 and 110 days after planting (DAP), were determined. Variety and harvesting stage did not (p > 0.05) influence CP and NDF content of the vines. Concentration of CP ranged from 104.9 to 212.2 g/kg DM, while NDF ranged from 439.4 to 529.2 g/kg DM across harvesting stages and varieties. Nitrogen degradability (ND) at 70 and 110 DAP was highest (p < 0.05) in Ligwalagwala (743.1 and 985.0 g/kg DM, respectively). Treatment of vines with tannin-binding polyethylene glycol (PEG) increased (p < 0.05) in vitro ruminal cumulative gas production parameters (a, b and c). The in vitro ruminal biological activity of tannins, as measured by increment in gas production parameters upon PEG inclusion, had a maximum value of 18.2%, suggesting low to moderate antinutritional tannin activity. Ligwalagwala vines, with highly degradable N, would be the best protein supplement to use during the dry season when ruminant animals consume low N basal diets and maintenance is an acceptable production objective. Tia Nong 66 and Kenya varieties, with less degradable N, may be more suitable for use as supplements for high-producing animals such as dairy goats.

Antiporcine relaxin (antipRLX540) treatment decreases relaxin plasma concentration and disrupts delivery in late pregnant pigs.

Antibody against porcine relaxin (antipRLX540; 1:950,000) was produced in sheep and used to determine the effect on relaxin and progesterone secretion, and on parturition in late pregnant pigs. In group 1, Yorkshire gilts with normal estrous cycles were bred on the second observed estrus and fitted with an indwelling jugular cannula and an intraperitoneal cannula on day 100 of pregnancy. Gilts were infused at 6-h intervals with antipRLX540 (n = 10) or PBS (n = 10) beginning on day 103 until parturition. From days 103 to 120, daily blood samples (10 ml) were collected for RIA of relaxin, progesterone, and prolactin. In group 2, bred gilts were randomly assigned to antipRLX540 (n = 11), relaxin (n = 5), and PBS (n = 8) treatment on days 111, 113, and 115. Blood was collected twice daily from day 108 to 120, and every 20 min on days 111, 113, and 115 beginning 60 min before treatment and continuing 180 min. Parturition in gilts given antipRLX540 occurred on day 112.7 compared with day 114.0 in relaxin-treated gilts and day 114.3 in PBS controls (P < 0.05). Duration of delivery from first to last piglet was greatly delayed in antipRLX540 gilts (240 min) compared with PBS controls ([117 min] P < 0.005). Average number of stillborns was greater in antipRLX540- than in PBS-treated controls (2.4 vs. 1.0; P < 0.05). Relaxin concentration in peripheral plasma was lower in antipRLX540-treated gilts from day 105 to 110, but on day 113 the antipRLX540-treated group had a greater relaxin peak release compared with PBS-treated animals (P < 0.05). Plasma progesterone concentrations were similar in antipRLX540- and PBS-treated gilts throughout the period of the study. In group 2, by day 113, progesterone decreased in antipRLX540-treated gilts compared with relaxin- and PBS-treated gilts. Prolactin levels were similar in both antipRLX540- and PBS-treated gilts; however, from 1 to 3 days postpartum the antipRLX540 group had higher prolactin concentration (P < 0.05). The results indicate that antipRLX540 decreased circulating plasma concentrations of unbound or free relaxin during the last 10 days of pregnancy in Yorkshire gilts. AntipRLX540 markedly increased both the duration of delivery of piglets and the average number of stillbirths in this litter-bearing species compared with PBS-treated controls. This study provides strong evidence that increasing circulating concentrations of relaxin during late pregnancy is crucial for unimpaired parturition in the pig.

Acute shifts in relaxin, progesterone, prolactin, and growth hormone secretion in Chinese Meishan gilts during late pregnancy and after hysterectomy.

Pregnant and hysterectomized Chinese Meishan gilts were used to investigate mechanisms regulating the production and secretion of relaxin, progesterone, prolactin (PRL), and growth hormone (GH) during different reproductive states. Gilts were bred to Meishan boars on the 1st d of the second observed estrus, and unmated gilts were hysterectomized on d 8 (estrus = d 0). Blood samples (10 mL) were collected twice daily (0800 and 2000) from d 9 to 120 and every 20 min within a 3-h period on d 112 to 116. Relaxin plasma concentrations were consistently greater in hysterectomized than in pregnant (6 vs 2 ng/mL, P < .05) gilts on d 99 to 109. The surge relaxin release on d 114 was greater in pregnant (66 ng/mL) than in hysterectomized gilts (34 ng/mL, P < .05). Thereafter, relaxin remained consistently increased (12 ng/mL) in hysterectomized gilts, whereas it was basal (< .5 ng/mL) during lactation. Progesterone concentrations decreased by half from d 109 to 115 and remained at 16 ng/mL through d 120 in hysterectomized pigs, whereas in pregnant pigs progesterone became basal after parturition. Prolactin in hysterectomized gilts remained at 4 ng/mL throughout the study period, whereas in pregnant gilts PRL increased steadily from 16 ng/mL on d 99 to 39 ng/mL at parturition and remained increased during lactation. Growth hormone concentrations were similar in hysterectomized and pregnant gilts from d 99 to 114; however, GH concentrations were consistently greater (P < .05) in lactating than in hysterectomized gilts (2.6 vs 1.0 ng/mL, respectively). These results indicate that PRL and GH secretions differ in pregnant and hysterectomized pigs because of the physiological changes necessitated by the onset of lactation.

Mifepristone (RU 486) induces parturition in primiparous beef heifers and reduces incidence of dystocia.

Crossbred beef heifers (n = 21) were artificially inseminated and on d 268 (expected parturition = d 283) heifers were fitted with an indwelling jugular catheter for sequential blood sampling from d 270 to 278. Heifers were assigned randomly to three treatment groups (n = 7) on d 277: Group 1 received the synthetic steroid mifepristone (RU 486) alone, Group 2 received RU 486 plus relaxin, and Group 3 received placebo treatment. Parturition occurred 43 h after treatment in Group 1, 52 h in Group 2, and 182 h in Group 3, and hormone treatment reduced treatment-to-calving interval compared with diluent treatment (P < .01). Calf birth weights were lower in hormone-treated than in placebo-treated heifers (P < .025), but all calves were vigorous at birth. The incidence of dystocia was lower (P < .05) in heifers in Groups 1 and 2 than in controls. Conversely, placental retention longer than 24 h was observed in hormone-treated heifers, and none occurred in the control group. The RU 486 reduced circulating progesterone concentrations in treated heifers, whereas progesterone concentration remained increased in control (P < .01). The results show that RU 486 alone or combined with relaxin induces delivery in late-pregnant heifers. Hormone treatment promotes calving ease with a markedly reduced incidence of the detrimental effects of dystocia, which may be a serious problem in first-calf heifers.