Experimental results of oestrus synchronisation in yak

M. Davaa,¹ D. Badamdorj,² B. Erdenebaatar,² A. Magash,¹ Y. Zagdsuren² and N. Altankhuag²

1. National Yak Research Centre, State University of Agriculture, Zaisan, Ulaabaatar-210153, Mongolia
2. Research Institute of Animal Husbandry, Zaisan, Ulaabaatar-210153, Mongolia

Summary

Fifty-three yak cows and 26 yak heifers were induced for oestrus synchronisation. Among them 52.8 and 30.8% showed fully synchronised oestrus, 18.8 and 30.8% incomplete oestrus, and 28.3 and 38.4% anoestrus, respectively. The results indicated that the calving period, fattening level (i.e. body condition) and types of hormonal preparations influenced oestrus induction.

Keywords: Hormone, oestrus synchronisation, yak

Introduction

Hormonal preparations pregnant mare serum gonadotropin (PMSG), luteinizing hormone (LH) and prostaglantin F-2 alpha (PGF2-a) have been investigated for oestrus synchronisation in yak cows. The results of these studies have shown that the oestruses of yak synchronised were in lower rates than the other bovine species. Yak is an animal well adapted to the ecological condition of highlands and has the peculiarity to become pregnant only between the summer and autumn seasons. The aim of this study was to find the opportunity to fertilise yak in large numbers through oestrus synchronisation.

Materials and methods

The oestrus of yak cows were synchronised by using PGF2-a (Prosolvin, Intervet; Lutalyse, Upjohn) in 1.0 to 2.0 mL once intramuscular injection and the oestrous behaviour of treated animals were observed for 72 hours. Only cows showing anoestrus after the treatment were repeatedly injected on the eleventh day.

Controlled internal drug release (CIDR) containing progesterone (sponge, Hamilton) was inserted into the vagina of experimental animals for 10 days and 2.0 mL Prosolvin was intramuscularly injected two days before the CIDR removal. A full oestrus was also synchronised by intravaginal progesterone releasing intravaginal device (PRID) with progesterone and krestar implantation in the ear for 12 days. The oestrus of the yak cows was detected with assistance of teaser bulls. Cows and heifers without corpus luteum in their ovaries were treated with 1000 IU of PMSG (Folligon, Aukland) and 2 mL of follicle-stimulating hormone (FSH; Super OV Rom) intramuscularly in order to promote ovarian activity during period of oestrous cycle.

Animals in oestrus were artificially inseminated twice in 8-12 hours interval. The results were analysed to examine the effects of calving period, age, live weight and hormonal treatments on the oestrous induction.

Results and discussion

Oestrus synchronisation was achieved in 43.7% of all yak cows treated with PGF2-a. Of the remainder, 25% had incomplete oestrous cycle and 31.3% were anoestrous. Among heifers treated with hormones only 15.4% were synchronised (Table 1).

Table 1. Oestrus synchronisation of yak with hormones.

Treatments	Age group	No.	Oestrus synchronised		Incompletely synchronised		Anoestrous
			No.	%	No.	%	No.	%
PGF2-a	Cow	32	14	43.7	8	25.0	10	31.3
	Heifer	13	2	15.4	5	38.5	6	46.1
Progesterone sponge	Cow	13	9	69.2	1	7.7	3	23.0
	Heifer	5	4	80.0	1	20.0
PMSG	Cow	4	4	100.0
	Heifer	4	2	50.0	1	25.0	1	25.0
FSH	Cow	4	1	25.0	1	25.0	2	50.0
	Heifer	4			1	25.0	3	75.0
Total	Cow	53	28	52.8	10	18.8	15	28.4
	Heifer	26	8	30.8	8	30.8	10	38.4

Oestrus synchronisation rates in all animals were 69.2% and 80.0%, respectively, for intravaginal use of progesterone sponge and implantation in ear. The corpus luteum was completely degenerated for a favourable development of the follicles and the oestrus was detected within a shorter period after withdrawal of progesterone sponge.

The PMSG treatment resulted in 100% synchronisation of yak cows and 50% synchronisation of heifers. For FSH, only 25% of yak cows were synchronised and none of the treated heifers were synchronised. Thus, FSH alone had poor results.

Results from the four treatments were pooled together to examine effects of live weight, fattening level and days since previous calving (Table 2).

Among heifers weighing below 190 kg, 33.3% had incomplete oestrous cycle, 66.6% were anoestrous after the treatment while none was successfully synchronised. On the other hand, oestrus synchronisation rate of heifers above 190 kg bodyweight was 57.1%. Only 14.3% were anoestrous while 28.6% had incomplete synchronisation in this group. This result should probably be considered in relation to the stage of growth and fattening level of the animals. Of the 38 'reasonably fat' animals treated, 47.4% were fully synchronised, 15.8% were incompletely synchronised and 36.8% were anoestrous. Animals in `poor' (fattening) condition, did not respond at all to the hormonal treatment.

Table 2. Effect of age, live weight, body condition and days after calving on synchronisation rates.

Influencing factors	No.	Oestrus synchronised		Incompletely synchronised		Anoestrous
		No.	%	No.	%	No.	%
Age
Cow	53	28	52.8	10	18.9	15	28.3
Heifer	26	8	30.8	8	30.8	10	38.4
Live weight of heifers (kg)
>190	12	0	0	4	33.3	8	66.7
<190	14	8	57.1	4	28.6	2	14.3
Fattening level
Good
Cow	9	9	100
Heifer	4	4	100
Reasonable
Cow	36	13	52.8	10	27.8	7	19.4
Heifer	12	4	33.3	8	66.7
Poor
Cow	8					8	100
Heifer	10					10	100
Days after calving
<60	6	2	33.3	3	50.0	1	16.7
61-90	38	18	47.4	6	15.8	14	36.8
>91	9	8	88.9	1	11.1

While the group treated less than 60 days after calving had 33.3% of the animals completely synchronised, 50% incompletely synchronised and 16.7% anoestrous, the respective rates of those treated 61–90 days post-parturition were 47.4, 15.8 and 36.8%. On the other hand 88.9% of animals treated more than 91 days post-parturition were successfully synchronised and only 11.1% were incompletely synchronised. These results indicate the need to delay synchronisation, after parturition, until animals have fully recovered from the previous calving and regained body condition.

Acknowledgements

The authors are very grateful to Dr Altanhuag H. for his support to this study.