Effect of dietary-induced changes in plasma insulin concentrations during the early post partum period on pregnancy rate in dairy cows

Abstract

Dietary stimulation of insulin in post partum dairy cows has been found to enhance ovarian follicle development but to impair oocyte developmental competence. The objective of this study was to test the hypothesis that pregnancy rate would be improved by feeding a diet to stimulate higher insulin (H) until cows resumed ovarian cyclic activity after parturition, and then feeding a diet to lower insulin (L) during the mating period. Each diet was fed to 30 post partum dairy cows until their first rise in milk progesterone, when 15 cows in each group were transferred to the other diet (treatments HL and LH) and 15 cows in each group remained on their original diet (treatments HH and LL) until 120 days post partum. Treatments did not affect dry matter intake, milk yield and metabolisable energy balance. Plasma insulin concentration was elevated in cows fed on H compared with cows fed on L. Treatment did not affect days to first progesterone rise, first oestrus or first insemination. At 120 days post partum, 27% of cows on each of treatments HH, LL and LH were pregnant, but 60% of cows on treatment HL were pregnant (PZ0.021). These findings support the concept that physiological relationships between insulin and the reproductive system vary according to stage of the reproductive cycle, and suggest that pregnancy rate can be enhanced by a two-diet strategy tailored to optimise responses before and after the first post partum ovulation.

Prepartum and postpartum nutritional management to optimize fertility in high-yielding dairy cows in confined TMR systems

“…Garnsworthy et al (2008) proposed that feeding a glucogenic diet (higher in starch) until cows resumed ovarian cyclicity followed by a higher fat (lipogenic) diet during the breeding period would improve reproductive success. In subsequent research, the number of cows pregnant at 120 days was greater for cows fed a glucogenic (high-starch) diet that increased insulin early postpartum followed by the lipogenic diet (higher fat) during the breeding period (Garnsworthy et al, 2009). More recent studies have not confirmed this effect (Dyck et al, 2011;Gilmore et al, 2011) although diets and experimental conditions differed and cow numbers were limited.…”

Nutritional sub-fertility in the dairy cow: towards improved reproductive management through a better biological understanding

“…The results of testing glucogenic-lipogenic feeding strategies (van Knegsel et al, 2007b;Garnsworthy et al, 2009) do not yet, on their own, make an overwhelming case for this approach to be applied. We currently lack larger studies and demonstration of clear-cut differences.…”

Nutritional management to optimize fertility of dairy cows in pasture-based systems

“…Early postpartum dairy cows fed TMR diets designed to increase circulating insulin concentrations had an earlier return to cyclicity and had a more favourable conception rate to first service (Gong et al, 2002). A follow-up study reported by Garnsworthy et al (2009) indicated that the likelihood of successful pregnancy establishment was increased by feeding a diet designed to stimulate high circulating insulin concentrations until cows resumed cyclicity (average~30 days postpartum), and then switching to a diet designed to stimulate low circulating insulin concentrations until pregnancy establishment. Those authors hypothesized that after resuming cyclicity, low circulating insulin concentrations would improve follicular development, oocyte competence and embryo development (Garnsworthy et al, 2009).…”

“…A follow-up study reported by Garnsworthy et al (2009) indicated that the likelihood of successful pregnancy establishment was increased by feeding a diet designed to stimulate high circulating insulin concentrations until cows resumed cyclicity (average~30 days postpartum), and then switching to a diet designed to stimulate low circulating insulin concentrations until pregnancy establishment. Those authors hypothesized that after resuming cyclicity, low circulating insulin concentrations would improve follicular development, oocyte competence and embryo development (Garnsworthy et al, 2009). Although the cows assigned to a high-insulin diet until resumption of cyclicity followed by a low-insulin diet thereafter did have a statistically significant improvement in reproductive performance, fertility of animals on the other treatments was poor, and the study had a small number of animals per treatment (n = 15).…”