Waarnemings oor die voorkoms van bronstigheid by Afrikaner en Jerseykoeie onder ekstensiewe toestande in Noord-Kaapland

Abstract

Gedurende die uitvoering van twee kruisteeltprojekte te Vaalhartslandbounavorsingstasie is inligting verkry in verband met die voorkoms van bronstigheid tydens 'n geslote dekseisoen by Afrikaner- en Jerseykoeie. Vir vyf agtereenvolgende jare is waarnemings gedoen op 'n kudde van ongeveer 270 Afrikaner en 75 Jerseykoeie. Oor genoemde periode het uit 'n totaal van 1297 Afrikaner- en 357 Jerseykoeie, 80,3 en 94.7% onderskeidelik waarneembare estrus getoon. Dit was veral lakterende Afrikanerkoeie en by uitstek die met hul eerste kalf wat geneig het tot 'n lang post partum anestrusperiode. Slegs 55,9 %van laasgenoemde groep het tydens die dekseisoen waarneembare estrus getoon teenoor 86.2% by dieselfde groep Jerseys. Die Jerseykudde is egter van 'n energielek voorsien gedurende kritieke voedingstoestande wat wel 'n effek kon gehad het. Afrikaners het 60.3 %van die waargenome bronsperiodes in die vroee oggend getoon teenoor 39,7 %in die laat namiddag. Ooreenstemmende data by die Jersey was 59,0 en 41,0%onderskeidelik vir die twee waarnemingstye, Van 543 voltooide estrussiklusse by die Afrikaner was 57,1 %binne die normalc grense (18 -23 dae) teenoor 53,6 %van 194 siklusse by die Jerseys. Siklusse korter as 18 dae het in 22.1 % van die gevalle by die Afrikaner voorgekom teenoor 32,5 %by die Jerseys. Die gemiddelde lengte van normale siklusse was 20,53 en 20.35 dae by die Afrikaner en Jersey onderskeidelik.

English Title: Observations on the occurrence of oestrus in Africander and Jersey cattle under extensive conditions in the Northern Cape

English Abstract

Data concerning the occurrence of oestrus in Africander and Jersey cattle under extensive conditions were obtained from a crossbreeding program at Vaalharts Agricultural Research Station. Observations were made during the annual two and a half month breeding season on a herd of approximately 270 Africander and 75 Jersey cattle for five consecutive years. During this period oestrus was observed in 80,3 % of 1297 Africander and in 94,7 % of 357 Jersey cows. The occurrence of a relatively long post partum anoestrous period was evident in lactating Africander cows, especially those with the first calf at foot. Only 55,9 %of the latter exhibited oestrus during the breeding season compared to 86,2 %of their Jersey counterparts. The Jersey herd, however, received an energy lick during critical nutritional periods which may have had some effects. Amongst the Africanders, 60,3 % of the observed oestrous periods were first noted during the early morning and 39,7 % in the late afternoon. The corresponding percentages for the Jersey females were 59,0 and 41,0 %respectively. Of the 543 completed oestrous cycles recorded in the Africander herd, 57,1 % were within the normal acceptable limits (18-23 days) as against 53,6 %of the 194 completed cycles of the Jerseys. A cycle length of less than 18 days was recorded in 22,1 and 32,5 % of the observations amongst the Africanders and Jerseys respectively. The average length of normal oestrous cycles was 20,53 days in the Africander against 20,35 days in the Jersey.