Why is it getting more difficult to successfully artificially inseminate dairy cows?

Abstract

Successfully using artificial insemination (AI) is defined as getting cows pregnant when the farmer wants them in-calf and making the best use of appropriate genetic potential. Over the past 30 to 50 years, the percentage of animals in oestrus that stand-to-be-mounted (STBM) has declined from 80% to 50%, and the duration of STBM from 15 h to 5 h; both in parallel with a reduction in first-service-pregnancy-rate from 70% to 40%. Meanwhile, the incidence of lameness and mastitis has not decreased; and it takes more than an extra 40 and 18 days, respectively, to get a lame or mastitic cow in-calf compared to healthy herd-mates. The intensity of oestrus is 50% lower in severely lame cows, and fewer lame cows ovulate. Luteal phase milk progesterone concentrations are also 50% lower in lame cows, and follicular phase oestradiol is also lower in non-ovulating lame cows compared to ovulating animals. Furthermore, lame cows that do not ovulate do not have an LH surge, and the LH pulse frequency in their late follicular phase is lower (0.53 v. 0.76 pulses/h). Thus, we suggest that the stress of lameness reduces LH pulsatility required to drive oestradiol production by the dominant follicle. The consequent low oestradiol results in less-intense oestrus behaviour and failure to initiate an LH surge; hence there is no ovulation. A series of experimental studies substantiate our hypothesis that events activating the hypothalamus-pituitary-adrenal axis interfere at both the hypothalamus and the pituitary level to disrupt LH and oestradiol secretion, and thus the expression of oestrus behaviour. Our inability to keep stress at a minimum by appropriately feeding and housing high-production cows is leading to a failure to meet genetic potential for yield and fertility. We must provide realistic solutions soon, if we want to successfully use AI to maintain a sustainable dairy industry for the future.

Figure 1

Percentage of animals standing-to-be-mounted (STBM; ◆), first-service-pregnancy-rate (FSPR; □) and average milk yield (▲) in Holstein Friesian dairy cows reported over the last 50 years (references in text).

Figure 2

Days from calving to pregnancy in cows with different clinical production diseases (RFM retained foetal membranes; BCS body condition score; references in text).

Figure 3

Days from calving to commencement of luteal activity (CLA; ◆), and percentage of atypical profiles (■), of delayed onset of luteal activity (▲) and prolonged luteal phases (○) reported from milk progesterone studies over the past 30 years (references in text).

Figure 4

Peripheral plasma concentrations of LH in three control heifers on day 19 of the oestrous cycle (a) and in three heifers on day 19 during treatment with 100 IU ACTH every 12 h for 7 days from day 15 of the oestrous cycle (b). Dobson et al., 2000: reproduced with permission.

Figure 5

Mean ± s.e. plasma oestradiol in the upper panel, FSH in the middle panel and follicle diameters in the lower panel for (○) six control heifers, (△) five heifers that formed a prolonged follicle and (□) six heifers that formed a persistent follicle after treatment with 100 IU ACTH every 12 h for 7 days from day 15 of the cycle. Stars indicate control oestradiol values different from prolonged and persistent follicle oestradiol values (P < 0.05). Dobson et al., 2000: reproduced with permission.

Figure 6

Incidence of lameness (■) and mastitis (◇) in dairy cows reported over the last 50 years (references in text).