prolificacy of ewes Effect of premating injections of insulin on fertility and

Transcription

1 Effect of premating injections of insulin on fertility and prolificacy of ewes Kirkwood, R. N., Thacker, P. A', Korchinski, R. S', Gonzalez, A. andlaarveld, B Effect i"iections of insutin on fertility and prolificacy of ewes. Can. J.' Anim' Sci' 71: ' "Ip..-"tirg Ninety-six Suftblk.*",.*iu.o daily injection. bf l,ong-acting insulin (1'0 IU kg-') 9t t9l1: "ith". for 3 consecutive days after introduction oi runlr. Basal serum LH concentrations were higher (P< 0 05) in insulin-treated ewes (P < 0.05) but concentratlons of estradiol- 17B and the magnitude of the preovulai;t ah,urg" *".. utiuf."t.j. Interval to breeding, pregnancy rat_e and.subsequent litter size were nor influenced Uy t..ut,,'.ni foo.6 vs h, 69 vi. iq% ana 1,.65 vs for insulin and salineinjected ewes, respectively). Key words: Insulin, sheep' fertility, prolificacy \ Kirkwood, R. N., Thacker, P. A., Korchinski, R. S., Gonzalez, A. and Laarveld, B' 1991' Effet d9 l,injection d'insuline l" luite sur la fertilitd et la prolificitd des.brebis' can' J' Anim' Sci' 7l:241-2M. euatre-vingt-seize ""urrt brebis Suffolk ont reeu uneinjection quotidienne soit d'insuline ir action ;;,.-ii.;ui6 ), r";;?;,oirtion sal6e pendant 3 jours aprds avoir t6 mises en pr6sence d'un b6lier' La concentration s6rique basale de lg etuit plus 6liv6e (P<0,05) chez les brebis trait6es ir l'insuline (P < 0,05), mais on n'a observd aucune modiication de la concentration d'estradiol-17b, ni de I'amplitude du pic pr6ovulatoo. J" fu lff. Le traitement n'a eu aucune influence sur l'intervalle avant la lutte' le taux de f6condit6 et la raille de la port6e subsdquente (66,6 c. 63,3h,69 c.74% et 1,65 c' 1,69 respectivement pour les brebis ayantlegu de l'insuline et la solution sal6e). The reproductive performance of a ewe flock can be measured in terms of the proportion ofewes exposed to the ram that subsequently produce lambs (fertility) and the litter size of iwes lambing (prolificacy). Both fertility andprolificacy oi ewes improve as the number of ova shed increases from 1 to 3 (Robinson and Scaramuzzi 1986). The number of ova shed by a cycling ewe can be influenced by plane oi nuirition (Coop 1966), although mechanisms controlling nutritional effects on ovulation rate are unclear. However, interest has focussed on metabolic hormones, such as insulin, known to be influenced by diet (Cox et al. 1987). There is evidence of a synergistic role for insulin in the gonadotrophin-mediated stimulation of steroidogenesis in cultured ovarian granulosa cells (e.g., Veldhuis and Demers i985). Furthermore, malnutrition in pigs reduced both ovulation rate and plasma insulin Can. J. Anim. Sci. Tlz (Mar. 1991) Mots cles: Insuline, ovins, fertilit6, prolificit6 241 concentrations (Flowers et al' 1989)' However, following nutritional flushing, both ovulation rate and plasma insulin were increased (Flowers et al. 1989). Recently, insulin treatment has elevated ovulation rate in swine (Cox et al. 1987)' Further, the observed effect appeared to be independent of changes in serum concentrationi of gonadotrophins, suggesting a direct effect of insulin on ovarian function' Whether insulin treatment has any effect on the endocrine status or ovarian function in ewes has not been determined. The objective of the present study was to examine the effects of insulin injections, administered during the period encompassing ovarian folli-cular development. on the fertility and prolificacy of ewes. In September, sponges rmpregnated with 60 mg medroxy-progesterone acetate fferamx, Tuco"Products, Ora-ngeville, ON) were placed intravaginally in 96 mixed-parity Suffolk ewes weighing 89.5 t 1.0 kg (mean + SE) for 14 d'

2 aaa CANADIAN JOURNAL OF ANIMAL SCIENCE A:t th9 time of sponge removal, rams were ml--l and 10.0%, respectively. Glucose placed with ewes at a ratio of one ram to concentrations in serum iamples-from blood 10 ewes and the rams remained with the ewes collected into tubes containing potassium oxafor 25 d' The rams were fitted with marking late and sodium fluoride were determined harnesses to assist in determining the interval using a commercial kit (Glucose determinafrom-sponge removal to estrus. Ewes were tion-procedure, No. 510; Sigma, St. Louis, visually checked for indications of matins MO). threetimesdaily between08:00and l6:00 h. Tieatment effects on ewe fertility and Ewes were randomly selected to receive prolificacywereexaminedbyfishers'exact subcutaneous injections oflong--acting insulin test and Students' /-test, respectively, using (Lente, Novo Laboratones. wllowdale, on) the Number Cruncher Staiistical "Syste# administered at 1.0IU. kg-r body weight (NCSS l9g7). only data from ewes con_ (n:49) or saline (n:47). The insulin dose ceiving at their first estrus (determined on the ta: pqteg on a pilot trial using eight ewes basis 6f hmbing date) were included in the which indicated that blood glucoie concentra- analysis otproli'ficacy. Treatment effects on tion was reduced for less than 12 h or more serum components were investigated using lhal 1^2.lt,f9llor'ying injection of insulin at 0.5 repeated-measure analysis of variince 1NCSS g l'u l! t g ' body weight, respectively. 198'].). Four ewes from the insulin-treated L'utng the present study, injections were group displayed signs of clinical hypoglygiven 6, 28 and 50 h after sponge removal. cemia. Treatment of these animals was Blood samples were collected from l0 ewes terminated and the ewes were removed from per treatment 12 h after sponge removal (6 h the experiment. after first injection) and ai 6-h intervals until Injeitions of insulin increased (p<0.01) 72 h' Samples were collected into tubes concentrations of serum insulin from without additives and into tubes cortaining to 6.0 * t.o ng -I_ii. il;;j;: potassium oxalate and sodium fluoride. cose concentrations were decreased (p<dgl) Sampleswerecentritugedwithin t2 handthe from 62.7 r 4.7 to 33.9 t 4.id ;i-i: serumwasstoredat -20'Cuntilrequiredfor These respective elevations and re-cluctions assays of hormone and glucose content. were maintained for approximately l2h. Serumconcentrationsofinsulinweredeter- These data demonstrate that the injected mined by radioimmunoassay (RIA; Kirkwood insulin had the."p"rt"a physiological effect. et al. 1989). Assay sensitivity- and intra-assay Concentrationrbf I-H ln r".urriup to 36 h coefficient of variation (cv) were 0.21 ng following sponge removal *"r" higt"i ml-r and 5.1%, respectively. Serum conl (P<0.05jininsuiin-treatedewesbutnoeffect centrations of estradiol-l7 B were determined was observed on the magnitude of the usilq the procedure of wettermann et al. preovulatory LH surge Ganie t). Similarly, (1972) using rabbit anti-170-estradiol-6-bsa no treatment effect was observed for serum serum (Endocrine Sciences, Tarzana, CA). estradiol-170 concentrations (Table 1). Parallelism was observed between inhibition There was no treatment effect on the curyes with purified estradiol-l7p standards proportion of ewes conceiving at the first and various dilutions of a control serum. estrous period or on the mean number of Extraction-efficiency was 89.3 r 3.5%, as lambs pioduced by these ewes (Table 1). determined by the addition of [2,4,6,7-3Hl These observations demonstrate that estradiol-176 (New England Nuclear) to exogenous insulin had no effect on the indices serum. As.say sensitivity and intra-assay CV of reproductive performance of ewes measured yer-e I.J4 pg rube-' and 11.7%, respec_ in this experiment. tively' Serum concentrations of LH were The apparent lack of effect on follicular determined by established RIA (Rawlings estradioiproduction suggests that the insulin et al' 1984), in a single assay. Assay sensi- treatment did not affect 5varian function, even tivity and intra-assay CV were b.ta ng though basal serum LH concentrations were

3 KIRKWOOD ET AL. INSULIN AT BREEDING IN SHEEP z+) Table 1. The influence of insulin injections on serum LH and estradiol concentrations and the reproductive performance of ewes (means t SE) Saline Number of ewes Basal LH 1ng ml-1)' LH peak height (ng ml-') Time to LH peak (h) Basal estradiol (pg ml-r)" Interval to breeding (h) Ewes lambing (%) Litter size of ewes lambing zdetermined in 10 ewes during 36 h after sponge removal. a,bmeans followed by different letters differ (P<0.05). elevated. This suggestion is supported by there being no observed effect of insulin on the interval between sponge removal and breeding (Table 1). It is reasonable to suggest that the granulosa cells of the ovine ovary would respond to the stimulatory effects of insulin in a manner similar to those of the porcine ovary. However, the lack of effect on the reproductive performance noted in the present experiment suggests that such a stimulation did not occur. A variable response to exogenous insulin has been observed in pigs, with insulin either increasing ovulation rate (Cox et al. 1987) or having no effect (Kirkpatrick et al. 1967). The difference in response was attributed to the dose of insulin, since in the study by Kirkpatrick et al. (1967) no effect on blood glucose concentration was observed. In contrast, Cox et al. (1987) noted a chronic reduction in blood glucose concentration throughout the treatment period suggesting a prolonged hyperinsulinemia. In the present study, the period of decreased blood glucose and increased insulin concentrations was approximately 12 h. Therefore, it is possible that the duration of hyperinsulinemia was inadequate to result in ovarian stimulation. However, indications of overt hypoglycemia in some ewes militate against the use of a higher insulin dose. In conclusion, the results ofthe present study indicate that the administration of insulin during the period of follicular growth does not influence the reproductive performance of ewes !O.06a ' O.06b t6.6+4.'.l <o 1+5 R 6.1 t We wish to thank the staff of the campus sheep facility for their assistance in the management of the ewes. Financial support for this study was provided by Province of Saskatchewan Agriculture Development Fund. Coop, I. E Effect offlushing on reproductive performance of ewes. J. Agric. Sci. (Camb). 67: Cox, N. M., Stuart, M. J.' Althen, T. G., Bennett, W. A. and Miller, H. W Enhancement ofovulation rate in gilts by increasing dietary energy and administering insulin during follicular growth. J. Anim. Sci. 64: Flowers, B., Martin, M. J., Cantley, T. C. and Day, B. N Endocrine changes associated with a dietary induced increase in ovulation rate (flushing) in gilts. J. Anim. Sci. 67: 771-7'78' Kirkpatrick, H. L., Howland, B. E., First, N. L. and Casida, L. E. D67. Some characteristics associated with feed and breed differences in ovulation rate in the gilt. J. Anim. Sci. 26: Kirkwood, R. N., Thacker, P. A., Guedo, B. L. and Laarveld, B The effect ofexogenous growth hormone on the endocrine status and the occurrence of estrus in gilts. Can. J. Anim. Sci. 69: Number Cruncher Statistical System N. J. Hintz, Kaysville, UT. Rawlings, N. C., Jeffcoate, I. A. and Rieger' D. L Influence of estradiol 17 beta and progesterone on peripheral serum concentrations of luteinizing hormone and follicle stimulating hormone in the ovarectomized ewe. Theriogenology 22: Robinson, T. J. and Scaramuzzi, R. J Immunization and out-of-season breeding in sheep. Anim. Prod. Aust. 16: '

4 CANADIAN JOURNAL OF ANIMAL SCIENCE Veldhuis, J. D. and Demers. L. M A role of somatomedin C as a differentiation hormone and amplifier of hormone action on ovarian cells: Studies with synthetically pure somatomedin C and swine granulosa cells. Biochem. Biophys. Res. Commun. 130: Wettermann, R. P., Hafs, H. D., Edgerton, L. A. and Swanson, L. V Estradiol and progesterone in blood serum during the bovine estrous cycle. J. Anim. Sci. 34: R. N. Kirkwoodt, P. A. Thackerr, R. S. Korchinskit, A. Gonzalez2, and B. Laarveldr Departments of tanimal and Poultry Science and'obstetrics and Gynecology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0W0. Received 1l Julv accepted 15 Nov

5 This article has been cited by: 1. K. Suguna, S. Mehrotra, S.K. Agarwal, M. Hoque, U. Shanker, S.K. Singh, V.P. Varshney Effect of exogenous insulin administration on ovarian function, embryo/fetal development during pregnancy in goats. Animal Reproduction Science 111:2-4, [Crossref] 2. N.C. Whitley, E.L. McFadin-Buff, D.H. Keisler Effect of insulin on feed intake and reproductive performance of well-nourished nulliparous ewes. Theriogenology 54:7, [Crossref] 3. S Landau, A Bor, H Leibovich, Z Zoref, Z Nitsan, Z Madar The effect of ruminal starch degradability in the diet of Booroola crossbred ewes on induced ovulation rate and prolificacy. Animal Reproduction Science 38:1-2, [Crossref]