Effect of Restricted Feeding and Monopropylene Glycol Postpartum on Metabolic Hormones and Postpartum Anestrus in Grazing Dairy Heifers

Abstract

This study was designed to determine the effects of feed restriction and monopropylene glycol (MPG) supplementation on the reproductive, milk production, and somatotropic axes in dairy heifers postpartum. At calving, 49 Holstein-Friesian heifers were allowed either unrestricted (UNR; n = 18) or restricted access to pasture with (RES+MPG; n = 13) or without (RES; n = 18) MPG supplementation (250 mL drenched twice daily for 150 d). The average body condition score (BCS) of the heifers was 5.3 +/- 0.2 on a scale from 1 to 10 (where 1 = emaciated and 10 = obese). Body condition score and body weight were similar among the groups at calving and decreased after calving for all groups. However, body weight loss was around 10% greater for the RES and RES+MPG groups from wk 3 to 12 compared with UNR group. The length of the postpartum anestrous interval was similar for all groups (47, 51, and 45 +/- 5 d for the UNR, RES, and RES+MPG, respectively). Average milk production, protein, fat, and lactose yields during the first 12 wk postpartum were greater in the UNR group than in the RES and RES+MPG groups. Feed restriction affected plasma concentrations of insulin, with lower concentrations in the RES group compared with the UNR group. There were no differences in plasma concentrations of insulin between the RES+MPG group and the UNR or RES groups. An effect of feed restriction was observed on insulin-like growth factor-I concentrations and also a treatment by time interaction with a changing pattern through time as concentrations in the UNR group increased relative to the RES and RES+MPG groups. There were no differences in growth hormone concentrations among the groups. Glucose concentrations were lower in the RES group when compared with RES+MPG and UNR groups and this difference lessened over time. Plasma concentrations of nonesterified fatty acids were greater in the RES group compared with the RES+MPG and UNR groups. Leptin concentrations in the UNR group were greater than in the RES and RES+MPG groups. Hepatic growth hormone receptor 1A, total growth hormone receptor, and insulin-like growth factor-I relative mRNA expressions decreased postpartum with no effect of feed restriction, MPG supplementation, or interaction between time and treatment. During a challenge with MPG, insulin secretion was stimulated but no effect on postpartum anestrous interval in the treatment groups was observed. It was concluded that restricted pasture availability postpartum in dairy heifers calving in optimal BCS had no effect on the postpartum anestrous interval. It did however decrease milk production; thus, we can infer that monopropylene glycol supplementation does not act to prevent loss of milk yield.

Effect of feed restriction on reproductive and metabolic hormones in dairy cows

“…Increase in serum NEFA concentration ( P < 0.001) and decreases in BW ( P < 0.001) and BCS ( P < 0.02) were observed in all the FR groups (Table 3), indicative of NEB and fat mobilization, during our study. Increased serum NEFA concentration was previously observed when FR was applied to nonlactating (Rodrigues et al, 2011), early lactation (Radcliff et al, 2006; Chagas et al, 2008) and mid lactation (Velez and Donkin, 2005; Gross et al, 2011) cows. Cows fed 50ST had the greatest increase in circulating NEFA with a >4-fold increase on the first day after FR, peaking at a 7-fold increase on the second day of FR.…”

Reproductive performance of pasture-fed dairy cows supplemented with monopropylene glycol

“…In a previous study with heifers in ideal condition at calving (BCS 5.0) and at the PSM (BCS 4.1), administration of 250 ml MPG twice daily from calving to mating had no effect on the percentage of cows ovulating at the PSM (Chagas et al 2008). The nutritional status of the heifers in that study appeared to over-ride responses to supplementation.…”

“…The energy supplemented by 400 ml MPG is equivalent to 3.8% of the 170 MJ metabolisable energy /day required by a 450-kg cow producing 1.6 kg milksolids/day (Holmes et al 2003), so previous responses to MPG (Chagas et al 2007) were unlikely to be a result of additional dietary intake of energy. In another study, when MPG was given from calving it increased the frequency luteinising hormone pulses after 2 and 5 weeks of treatment, and also the concentration of insulin in plasma immediately after supplementation with MPG, suggesting a possible mode of action (Chagas et al 2008). This is supported by other work suggesting that stimulation of secretion of insulin by supplementation with monopropylene glycol could act as a trigger to the initiation of ovulation (Miyoshi et al 2001).…”

Effect of propylene glycol on fertility of postpartum dairy cows experiencing seasonal heat stress

“…Similarly, several researchers (Chagas et al, 2008;Lomander et al, 2012) observed no effect on commencement of luteal activity in cows fed with PG when compared with controls. Conversely, some researchers (Miyoshi et al, 2001;Bors et al, 2014;Rukkwamsuk and Seubsai, 2010) found that cows treated with PG had shorter days from calving to first estrus than that of cows without PG treatment.…”

“…Some studies have shown that PG treatment has no effect on onset of luteal activity in cows (Chagas et al, 2008;Lomander et al, 2012), whereas, others (Bors et al, 2014;Rukkwamsuk and Seubsai, 2010) observed that cows treated with PG had shorter days from calving to first estrus. Similarly, other researchers (Chagas et al, 2007;Miyoshi et al 2001) found no differences in the success of pregnancy at first AI for cows drenched with PG.…”