Liver blood flow and metabolic clearance rate of progesterone in sheep

195

114

The discovery of progesterone (P4) and elucidation of the mechanisms of P4 action have an important place in the history of endocrinology and reproduction. Circulating P4 concentration is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. The volume of luteal tissue and number and function of large luteal cells are primary factors determining P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. During timed artificial insemination (AI) protocols, elevations in P4 are achieved by increasing number of CL by creating accessory CL or by supplementation with exogenous P4. Dietary manipulations can also alter circulating P4, although practical methods to apply these techniques have not yet been reported. Elevating P4 before the timed AI generally decreases double ovulation and increases fertility to the timed AI. Near the time of AI, slight elevations in circulating P4, possibly due to inadequate luteal regression, can dramatically reduce fertility. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Our recent meta-analysis and manipulative study indicated small fertility benefits (3% to 3.5%) mostly in primiparous cows. Thus, previous research has provided substantial insight into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve reproductive success. Keywords: progesterone, lactating dairy cows, fertility ImplicationsThis manuscript reviews effects of circulating progesterone (P4) on dairy cattle reproduction. Various methods to elevate P4 during growth of the preovulatory follicular wave have been shown to increase pregnancies/ artificial insemination (AI) and reduce double ovulation, providing methods to improve fertility and reduce twinning rate in lactating dairy cattle. Conversely, very low concentrations of P4 near AI are needed to optimize fertility. Finally, elevations of P4 after AI can impact embryonic development and also may elevate fertility. Thus, innovative strategies to optimize circulating P4 concentrations during selected reproductive periods enhance our management tools for improving reproductive efficiency of lactating dairy cows. Discovery of Progesterone (P4)The discovery of P4 begins with a clear description by Regnier deGraaf (1641-1673) of the corpus luteum (CL), calling them 'globules' and correctly surmising (for rabbits) that 'the number of globules equals the number of offspring from a particular mating ' (deGraaf, 1672 in (Jocelyn andSetchell, 1972)). A key discovery came in the laboratory of Gustav Born , an excellent histologist, who observed that the CL was a ductless gland and correctly advanced the idea that it was a gland of internal sec...

Section: Factors Regulating Circulating P4 Concentrationsmentioning

confidence: 99%

Section: Factors Regulating Circulating P4 Concentrationsmentioning

confidence: 99%

Physiological and practical effects of progesterone on reproduction in dairy cattle

Wiltbank

Souza

Carvalho

et al. 2014

195

114

“…Underfeeding can also slow down the metabolic clearance of progesterone (Brockhus et al, 1988;Parr et al, 1993a), an effect that can be rapidly reversed by the resumption of normal intake (Mellor et al, 1987;Oddy and Holst, 1991). The metabolic clearance of progesterone is affected in two ways: (i) a greater rate of catabolism in the liver (Thomford and Dziuk, 1986;Thomas et al, 1987;Sangsritavong et al, 2002); (ii) an increase in hepatic blood flow (Parr, 1992;Parr et al, 1993b;Sangsritavong et al, 2002). About 96% of all progesterone entering the liver and the gut is removed and the breakdown products are excreted in the faeces (Parr et al, 1993b).…”

Section: Mechanism By Which Nutrition Influences Colostrum Productionmentioning

confidence: 99%

“…The metabolic clearance of progesterone is affected in two ways: (i) a greater rate of catabolism in the liver (Thomford and Dziuk, 1986;Thomas et al, 1987;Sangsritavong et al, 2002); (ii) an increase in hepatic blood flow (Parr, 1992;Parr et al, 1993b;Sangsritavong et al, 2002). About 96% of all progesterone entering the liver and the gut is removed and the breakdown products are excreted in the faeces (Parr et al, 1993b). Parr et al (1993b) also showed that the rate of blood flow in the hepatic portal vein was directly related to the level of feed intake when ewes consumed rations that provided half the maintenance requirements, full maintenance requirements or double maintenance requirements.…”

Section: Mechanism By Which Nutrition Influences Colostrum Productionmentioning

confidence: 99%

Colostrum production in ewes: a review of regulation mechanisms and of energy supply

Banchero

Milton

Lindsay

et al. 2015

In sheep production systems based on extensive grazing, neonatal mortality often reaches 15% to 20% of lambs born, and the mortality rate can be doubled in the case of multiple births. An important contributing factor is the nutrition of the mother because it affects the amount of colostrum available at birth. Ewes carrying multiple lambs have higher energy requirements than ewes carrying a single lamb and this problem is compounded by limitations to voluntary feed intake as the gravid uterus compresses the rumen. This combination of factors means that the nutritional requirements of the ewe carrying multiple lambs can rarely be met by the supply of pasture alone. This problem can overcome by supplementation with energy during the last week of pregnancy, a treatment that increases colostrum production and also reduces colostrum viscosity, making it easier for the neonatal lamb to suck. In addition, litter size and nutrition both accelerate the decline in concentration of circulating progesterone that, in turn, triggers the onsets of both birth and lactogenesis, and thus ensures the synchrony of these two events. Furthermore, the presence of colostrum in the gut of the lamb increases its ability to recognize its mother, and thus improves mother-young bonding. Most cereal grains that are rich in energy in the form of starch, when used as supplements in late pregnancy will increase colostrum production by 90% to 185% above control (unsupplemented) values. Variation among types of cereal grain in the response they induce may be due to differences in the amount of starch digested post-ruminally. As a percentage of grain dry matter intake, the amount of starch entering the lower digestive tract is 14% for maize, 8.5% for barley and 2% for oats. Supplements of high quality protein from legumes and oleiferous seeds can also increase colostrum production but they are less effective than cereal grains. In conclusion, short-term supplementation before parturition, particularly with energy-rich concentrates, can improve colostrum production, help meet the energy and immunological requirements for new-born lambs, and improve lamb survival.

“…Increasing dietary intake has been shown to reduce peripheral progesterone concentrations. It has been concluded that high feed intake increases liver blood flow and metabolic clearance, which leads to lowered plasma progesterone concentration (Parr et al, 1993a and1993b). These diet-induced alterations are mediated by insulin signalling (Smith et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Fertility and growth of nulliparous ewes after feeding red clover silage with high phyto-oestrogen concentrations

Mustonen

Taponen

Andersson

et al. 2014

The study aimed to determine the effects of red clover (Trifolium pratense) silage with high phyto-oestrogen content on ewe performance during their first breeding season. Red clover silage containing formononetin, biochanin A, genistein, and daidzein was fed to 10 nulliparous ewes of the prolific Finnish Landrace breed before, during and after the breeding season, for a total of 5 months. A control group of 10 ewes was fed with grass silage. The mean numbers of foetuses per pregnancy were 2.1 ± 0.7 and 2.2 ± 0.8 for the red clover and control groups, respectively. The total mass of the uterus with its contents was significantly greater in ewes of the red clover group compared with those of the control group. This difference was mainly explained by the greater volume of foetal fluids. Serum progesterone concentration in the red clover group was significantly lower over the entire period analysed than in the control group. In conclusion, the fecundity of the ewes was not reduced by red clover feed with high phyto-oestrogen concentrations. The volume of foetal fluids increased that could increase the risk for vaginal prolapse before the term.Keywords: ewe, red clover, phyto-oestrogen, formononetin, equol ImplicationsThe symbiotic rhizobia bacteria in red clover can fix atmospheric nitrogen, which promotes the growth of red clover itself and subsequent crops. This ability makes red clover valuable crops, especially in organic agriculture. Red clover is also a valuable ruminant feed, for example, lambs fed with red clover grow very well. Red clover is a rich source of polyphenols such as isoflavones, also referred to as phyto-oestrogens. Phyto-oestrogens can cause infertility problems in animals. As organic farming and the use of red clover is ever increasing, it is important to study what effect red clover feeding has on ewes' reproduction.