Late-night suckling inhibits onset of postpartum oestrous activity in beef cows

Abstract

To determine whether suckling of calves late at night would prolong lactation anoestrus, 5l Hereford-type cows (21 -29 days postpartum) were divided into three treatment groups. In treatments 1 (night suckling) andZ (day suckling) cows suckled their calves five times every 24 hours; the calves in treatment I did not suckle between 09:00 and 17:00 and those in treatment 2 between 21:00 and 05:00 . Cows in treatment 3 suckled only once daily at 17:00. By 80 days after calving a significantly greater proportion (P < 0.001) of the night-suckled cows had not returned to oestrus than those from the other treatments. The mean interval to first oestrus was significantly (P < 0.001) longer in treatment 1 (67.0 + 1.5 days) than in treatments2( 42.2x.2.5) and 3 (45.1 + 3.2 ). Lactationa noestrusd oesn ot appeart o be dependent on the number of sucklings per 24 hours, but rather on the time of night when suckling occurs. 

Om te bepaal of suiping van kalwers laat in die nag, laktasie anestrus sal verleng, is 5l Hereford-tipe koeie, 2l - 29 dae na kalwing, in drie groepe verdeel. In behandelings 1 en 2 het die koeie hul kalwers vyf keer elke 24 uur laat suip. Die kalwers is in behandeling I (nag suiping) nie tussen 09:00 en 17:00, en di6 in behandeling2 (dag suiping) nie tussen2 l:00 en 05:00 toegelaaot m te suip nie. Die koeiei n behandeling 3 het net eenkeerp er dag om 17:00 laat suip. 'n Betekenisvolle groter verhouding (P < 0.001) van die koeie wat gedurende die nag laat suip het (behandeling 1), het nie estrus teen 80 dae na kalwing, as by die ander behandelings groepe getoon nie. Die gemiddelde interval tot eerstee strusw as betekenisvo(l P < 0.001) langerb y behandelingI (67.0 t 1.5 dae)a s by behandelings2 (42.2 +2.5) en 3 ( 45.7+ 3.2 ). Klaarblyklik is laktasiea nestrusv and ie tyd van die nag wanners uipingp laasvinda ftanklik en nie van die aantal suipings per 24 uur nie.

Keywords: Beef cow, night suckling, postpartum anoestrus.