The Effect of Exogenous Growth Hormone on the Endocrine Status and the Occurrence of Estrus in Gilts

Kirkwood, Roy N.; Thacker, P. A.; Guedo, B. L.; Laarveld, B.

doi:10.4141/cjas89-107

Cited by 17 publications

(12 citation statements)

References 10 publications

(7 reference statements)

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“…Numbers of medium sized follicles in the ovary were also increased in early pregnancy, suggesting that pST treatment might stimulate follicle development and potentially ovulation rate at the second ovulation post-pST treatment. A similar promotion of follicle growth in the second follicular wave has been reported in heifers and in superovulated ewes in response to treatment with recombinant bovine GH in the preceding estrous cycle [19,20].Our finding that pST treatment at higher rates tended to suppress expression of behavioural estrus is consistent with previous work using similar doses of pST purified from porcine pituitary glands (~90 μg/kg/day), where pST treatment for 8-9 days prior to mating also reduced the proportion of gilts displaying a second estrus [15,16]. Our results confirm that pST can suppress estrus at high doses in the absence of any potential interference from other pituitary hormones, since we used recombinant pST.…”

supporting

confidence: 82%

Reproductive Responses to Daily Injections with Porcine Somatotropin Before Mating in Gilts

Gatford

Grupen

Campbell³

et al. 2010

Journal of Reproduction and Development

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Abstract. Litter size and progeny birth weights are lower in gilts than in sows. Somatotropin (ST) is an important regulator of ovulation, fetal growth and survival. We therefore investigated effects of pST treatment of gilts for two to four weeks before mating on ovulation rate, behavioural estrus, fetal growth and survival, litter size and birth weights.In Experiment One, gilts were injected with 0, 30, 60 or 90 μg pST/kg/day for 14 days commencing 7 days after first estrus. Reproductive tracts were collected and corpora lutea and follicle numbers counted 5.5 days after second estrus. Ovulation rate (P=0.031) and number of medium-sized follicles (P=0.059) correlated positively with pST dose. In Experiment Two, gilts were injected with 0, 12.5, 25 or 50 μg pST/kg/day for 21 days from first estrus, and mated at second estrus. Numbers of corpora lutea, follicles and fetuses were counted at day 31 of pregnancy. Numbers of medium follicles and ovary weights were positively related to pST dose. In Experiment Three, 31 week old (1 st replicate) or 27 week old (2 nd replicate) gilts were injected daily with 0 or 12.5 μg pST/kg/day until mating 25.9 ± 0.6 days later, and delivered at term. Pre-mating pST increased total litter size in younger gilts in the 2 nd replicate only (P<0.05). In conclusion, injecting gilts with pST before mating does not consistently alter ovulation rate, increases the number of medium follicles available for recruitment at the second mating after treatment and increases subsequent litter size in younger gilts. Key words: Embryo growth, Growth hormone, Litter size, Ovulation rate, Pig (J. Reprod. Dev. 56: [540][541][542][543][544][545] 2010) eproductive performance is poor in primiparous pigs (gilts), compared with multiparous dams (sows). Litter size in the pig is lowest at their first parity, and then increases in either the second or third parity depending on breed [1][2][3]. The low litter size of gilts appears to be primarily due to low ovulation rates, with small effects of parity on embryo survival, and similar rates of still birth across parities [2,[4][5][6][7]. Birth weight is also lower in gilt than sow progeny [1,3], resulting in decreased survival and postnatal growth. Gilts can comprise 30-50% of modern commercial herds (B Luxford, personal communication), and increasing the litter size and/or birth weight of gilt progeny would therefore have a substantial impact on overall profitability. Somatotropin (ST) or growth hormone (GH) is an important regulator of ovulation in a range of mammalian species. In transgenic mice and sheep constitutively expressing ST ovulation rate is increased but fertility decreased, which is due to decreased mating rates in mice, and increased fetal loss in sheep [8][9][10]. Conversely, resistance to ST reduces litter size in the last week of pregnancy by 35-55% in GH receptor/GH binding protein knockout mice, largely due to reduced ovulation rate [11,12]. In transgenic pigs continuously expressing ST at relatively high levels, ovulation is completely...

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supporting

confidence: 82%

Reproductive Responses to Daily Injections with Porcine Somatotropin Before Mating in Gilts

Gatford

Grupen

Campbell³

et al. 2010

Journal of Reproduction and Development

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“…However. when the injection regime commenced ar day l7 of the estrous cycle, the anestrus problem was resolved (Kirkwood et al l9g9b The results presented confirm previous data from our laboratory (Kirkwood et al 1988a(Kirkwood et al , 1989b, in that pGH treatment from 14 to22 d induced anestrus in a significant proportion of gilts. The occurrence of reproductive failure associated with pGH treatment is in contrast to the effects observed in humans, where gonadotrophin simulated ovulation was facilitated by co-treatment with growth hormone (Homberg et al 1988(Homberg et al , 1990 (Fig.…”

supporting

confidence: 82%

Timing of growth hormone injections and reproduction in gilts

Gilbertson¹,

Kirkwood²,

Thacker³

1991

Can. J. Anim. Sci.

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Gilts were slaughtered 30 ;;ilt;"6"rty at which time their ovaries were recovered for the determination of ovulatio"n rate. 6:".t.n oi pGH'resulted in elevated serum concentrations of triiodothyrontne, insulin and glucose (P <'0.01). Theie was no significant (P > 0. 1) treatment effect on mean sefum concentrations of LH or FSH. However, pGH treatment tended (P:0.1) to increase LH pulse f1eque191 and to decrease (P:0.01) Li pulse u.plitud". The incidence of a second estrus was reduced (P<0'01) inGH22compared to.onttoi ilfir, *iti Cff f t being intermediate (72.7 vs. 90'9 vs' 100% lior GH22' GH17 and control gilts, respecti"ively). Ovulation rut" *u, not affected by pGH treatment (15 1 vs' l4'3 vs' 14.0 for GH1Z, G;g^ll uni.onttJf gilts, respectively). The present data confirm an adverse effect of pCU on ovarian function and sugg"est that in altered LH pulsatility may be involved'

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“…Les (Kirkwood et al 1988). In addition to this potentially beneficial effect, growth hormone treatment has been shown to induce anestrus in approximately 50% of previously cycling gilts (Kirkwood et al 1988(Kirkwood et al , 1989a (Kirkwood er al. 1989a,b).…”

mentioning

confidence: 99%

EFFECT OF EXOGENOUS GROWTH HORMONE DURING THE FOLLICULAR PHASE ON hCG BINDING BY PORCINE LUTEAL TISSUE

Kirkwood¹,

Thacker²,

Guedo³

et al. 1990

Can. J. Anim. Sci.

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The Effect of Exogenous Growth Hormone on the Endocrine Status and the Occurrence of Estrus in Gilts

Cited by 17 publications

References 10 publications

Reproductive Responses to Daily Injections with Porcine Somatotropin Before Mating in Gilts

Reproductive Responses to Daily Injections with Porcine Somatotropin Before Mating in Gilts

Timing of growth hormone injections and reproduction in gilts

EFFECT OF EXOGENOUS GROWTH HORMONE DURING THE FOLLICULAR PHASE ON hCG BINDING BY PORCINE LUTEAL TISSUE

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