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  • Title: Effect of fractionated weaning on hormonal patterns and weaning to oestrus interval in primiparous sows.
    Author: Rojkittikhun T, Rojanasthien S, Einarsson S, Madej A, Lundeheim N.
    Journal: Acta Vet Scand; 1991; 32(1):35-45. PubMed ID: 1950850.
    Abstract:
    The effect of weaning the 4-5 heaviest piglets in the litter on day 33 of lactation and the remainder 2 days later (fractionated weaning) on plasma levels of prolactin, cortisol, oestradiol-17 beta (E2), progesterone (P4) and LH, as well as on the weaning to oestrus interval in primiparous sows was studied. Twelve crossbred sows were grouped into 6 pairs according to farrowing date and litter size. The litter of 1 sow in each pair (F) was weaned in 2 stages, and the other conventionally weaned at 35 days (C). Blood samples were collected via a permanent jugular vein catheter every 3 h from 9 a m to 9 p m daily throughout the experimental period, and intensively at 15 min intervals for 12 h on the day of first and final weaning and for 6 h on the day after each weaning. All sows were slaughtered following their first post-weaning oestrus and the reproductive organs were macroscopically examined. Lactational oestrus was not observed in any of the sows. Sows from 5 out of 6 pairs showed oestrus within 8 days of weaning and post-mortem examination showed normal ovulation. There was a tendency for the F sows to have a shorter weaning to oestrus interval, as compared with the C sows (5 of 6 pairs, 4.8 days v 5.6 days). The plasma levels of prolactin around weaning were not significantly different between the 2 groups. Within 6 h after final weaning, the prolactin concentrations decreased gradually from 7.6 and 8.7 to 1.6 and 1.7 microgram/l in the control and treatment groups, respectively. The plasma levels of cortisol, showing a diurnal rhythm (with the lowest level at 6 and/or 9 p m), did on no occasion differ between the 2 groups. On the day of final weaning, no diurnal rhythm was observed, with cortisol remaining high at 6 and 9 p m. The plasma levels of E2 and P4 were low until final weaning in both groups. After final weaning the E2 levels rose faster in the F sows than in the C sows, to 44.3 and 34.8 pmol/l, respectively, on day 2 (p less than 0.01). No significant differences in levels of plasma LH and the number of LH pulses were observed between the groups. After final weaning the average and base levels of LH and the number of LH pulse(s) increased significantly. Effekten av avvånjning av de 4–5 tyngsta smågrisarna i kullen på dag 33 av diperioden och de återstående 2 dagar senare på blodplasmakoncentrationerna av prolaktin, kortisol, 17β-östradiol (E2), progesteron (P4) och LH samt intervallet från avvänjning till brunst studerades hos ungsuggor. Tolv korsningssuggor grupperades i 6 par efter grisningsdatum och kullstorlek. Kullen till en sugga i varje par (F) avvandes i 2 etapper och kullen till den andra suggan på konventioneilt sätt på dag 35 (C). Blodprov togs via permanent jugularven dagligen var 3:e timme från kl. 09.00 till kl. 21.00 under hela experimentperioden, var 15:e minut under 12 timmar dag 33 och dag 35 samt under 6 timmar dag 34 och dag 36. Suggorna slaktades efter första brunsten och könsorganen obduceredes. Ingen sugga visade brunst under diperioden. Alla suggor i 5 av 6 par visade brunst och ovulerade inom 8 dagar efter avvänjningen. Det fanns en tendens till kortare intervall hos F-suggorna än hos C-suggorna (5 av 6 par; 4,8 respektive 5,6 dagar). Prolaktinkoncentrationerna var inte signifikant skiida melian de 2 grupperna. De sjönk från 7,6 och 8,7 till 1,6 och 1,7 ug/l i C- respektive F-gruppen inom 6 timmar efter avvänjningen. Kortisolkoncentrationen visade en signifikant dygnsvariation (lägst koncentration kl. 18.00 och/eller kl. 21.00). Avvänjningsdygnet (dag 35) observerades ingen dygnsvariation av kortisol. E2 och P4 var låga fram till avvånjningen (dag 35) i båda grupperna. Efter avvånjningen steg E2-kon-centrationen snabbare hos F- ån hos C-suggorna (44,3 och 34,8 pmol/1 på dag 2 hos F- respektive C-suggorna, p < 0,01). Inga signifikanta skillnader påvisades i LH-nivåerna eller antalet LH-peakar mellen de 2 suggrupperna. Efter avvånjningen steg såvål basala LH-nivåerna som antalet LH-peakar signifikant.
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