Our protocol and sampling regime for milk ELISA detected a large proportion (74
%) of buffaloes that had resumed their ovarian cyclicity by Day 150 post partum but the farmers’ oestrus detection rate was low under the assumption that the observed progesterone rise in milk followed an ovulation and a normal cycle. In accordance with these findings, Barkawi et al.
] showed that approximately 90
% of the buffaloes resumed their ovulatory cycle within 60
days post partum. The reasons for missed oestrus could be due to silent ovulation or anovulatory luteinization of follicles during the early postpartum period [24
]. However, differences in production system and breeds of animals might have resulted in the variation in post partum ovarian activity among the published studies. Usmani et al.
] found that 86
% of Nili-Ravi buffaloes showed at least one short luteal phase 8 to 13
days before the first oestrus. Accordingly, data of the present study indicate a higher number of missed oestrus in buffaloes that resumed luteal activity between Day 30 and Day 70 than those resuming luteal activity between Day 71 and Day 130. It remains to investigate to which extent the first post partum ovulation is associated with oestrus signs in some buffaloes. Extension programmes on educating farmers on oestrus behaviour and heat detection based on secondary signs, for instance, vulval swelling and vaginal discharge, may help increasing the oestrus detection rate [28
A poor BCS may have a negative impact on ovarian activity in buffaloes as anoestral buffaloes have lower BCS than buffaloes having oestral cycles [4
]. Our study shows that the BCS is not only associated with the interval from calving to first oestrus but also with milk production, as shown previously [29
]. In the study area, feeding opportunities for grazing buffaloes are limited during December through March. Most of the buffaloes calved during October through December. It is likely that unavailability of forage during the post partum period might have caused reduced BSC and milk production. In fact, good nutritional management in Zebu cows is important to handle the negative energy balance due to milk production [31
]. Hayashi et al.
] reported that a decline of nutrient supply as a result of fodder shortage leads to catabolism of body tissue and decreased BCS. Poor BCS of cows not only increases calving to first services interval but also reduces conception rate [9
Anoestral buffaloes had a milk progesterone concentration consistently lower than cyclic buffaloes (<1
ng/ml). Similarly, in a study of 17 complete post partum periods in Murrah buffaloes in Sri Lanka, plasma progesterone concentrations remained low (<0.25
ng/ml) for a period ranging from 92 to 210
]. McCool et al.
] reported <1
ng/ml plasma progesterone in anoestrus Swamp buffaloes.
Milk progesterone data based on three samples (Day 0, Days 10–12, and Days 22–24) helped us making a clear distinction between pregnant and non-pregnant buffaloes and identification of ovarian cyclicity. One non-pregnant buffalo had a progesterone profile of low, high and low on Day 0, Day 12 and Day 22, respectively. Uçar et al.
] reported progesterone concentrations of 0.97
2.95 and 8.04
ng/ml on Day 0, Day 11 and Day 21, respectively, of pregnant Anatolian buffaloes. Our results are in agreement with Uçar et al.
] showing progesterone profile of low (<1
ng/ml), high (≥ 1
ng/ml) and high (≥ 1
ng/ml) on Day 0, Days 10–12 and Days 22–24, respectively in pregnant water buffaloes. We showed progesterone profile of low (<1
ng/ml), high (≥ 1
ng/ml) and low (< 1
ng/ml) at Day 0, Days 10–12 and Days 22–24, respectively in cyclic water buffaloes which is in agreement with Qureshi et al.
] who determined progesterone concentrations in defatted milk of dairy buffaloes of 0.30
0.84 and 0.88
ng/ml on the stage of oestrus, developing corpus luteum, developed corpus luteum and regressing corpus luteum, respectively. Milk progesterone measurement by ELISA was 82-88
% accurate for pregnancy diagnosis in cows [37
]. In fact, milk progesterone level on Days 22–24 was used to interpret pregnancy results with 100
% accuracy of non-pregnancy diagnosis in cattle and buffaloes [38
]. In our laboratory, 94
% of pregnant cows were accurately detected by using milk progesterone ELISA and 100
% non pregnant cows were detected both by milk progesterone ELISA and radioimmunoassay [16
]. These findings suggest that a quantitative milk progesterone assay could be used in early pregnancy diagnosis in buffaloes as reported earlier [5