Apelin System in Mammary Gland of Sheep Reared in Semi-Natural Pastures of the Central Apennines.

Francesca Mercati,Paola Scocco,Cecilia Dall'Aglio,Linda Petrucci,Margherita Maranesi,Elena De Felice,Rolando Pasquariello,Federico Maria Tardella

doi:10.3390/ani8120223

Abstract

Simple SummaryGrazing activity is fundamental to natural grassland biodiversity preservation. Increasing summer aridity decreases the grassland pastoral value, negatively affecting animal morpho-functional features and production with detrimental effects on the extensive sheep farming sustainability. Since adipokines represent a link between a subject’s energy availability and tissue metabolism, we investigated the presence and distribution of the system composed of the adipokine apelin and its receptor in the mammary gland of sheep during the period between maximum flowering and maximum dryness of the pasture, providing a group of sheep with food supplementation. This work represents a part of a wider study aimed to buffer the negative effects of increasing summer drought stress on farm income and to maintain the grassland biodiversity. Our findings improve the knowledge of apelin/receptor system function on the sheep mammary gland and this could be a useful tool in the farm management practices.Sheep are the most bred species in the Central Italy Apennine using the natural pastures as a trophic resource and grazing activity is fundamental to maintain the grassland biodiversity: this goal can be reached only ensuring an economical sustainability to the farmers. This study aimed to investigate the apelin/apelin receptor system in ovine mammary gland and to evaluate the differences induced by food supplementation, in order to shed light on this system function. A flock of 15 Comisana x Appenninica adult dry ewes were free to graze from June until pasture maximum flowering (MxF). From this period to pasture maximum dryness (MxD), in addition to grazing, the experimental group (Exp) was supplemented with 600 g/day/head of cereals. Apelin and apelin receptor were assessed by Real-Time PCR and immunohistochemistry on the mammary glands of subjects pertaining to MxF, MxD and Exp groups. They were detected in alveolar and ductal epithelial cells. The pasture maximum flowering group showed significant differences in apelin expression compared with experimental and MxD groups. Apelin receptor expression significantly differed among the three groups. The reduced apelin receptor expression and immunoreactivity levels during parenchyma involution enables us to hypothesize that apelin receptor plays a modulating role in the system control.

Highlights

On the basis of the above-mentioned considerations, this study investigated the presence and expression of APLN and its specific receptor apelin receptor (APLNR) in the dry sheep mammary gland in order to better understand the actions and functions of APLN/APLNR system
From pasture maximum flowering to maximum dryness (MxD), ten ewes were divided into two homogenous groups as regards age, reproductive performance, body condition score (BCS) and body weight; BCS was assessed at both the middle and the end of the trial [2]
To the best of our knowledge this is the first study on the expression of APLN and APLNR in the mammary glands of ewes during the dry period

Summary

Introduction

The natural and semi-natural pastures in the central Apennines in Italy are used as trophic resources for zootechny, but the increase in summer aridity causes a decrease in the pastoral value of the grasslands; it is registering an anticipation of the moment of pasture maximum flowering and a shortening of the period between maximum flowering and maximum dryness of pastures.This fact reflects on a lower availability of both forage quality and quantity; the increase in drought stress is detrimental to the sustainability of extensive sheep farms because it affects the morpho-functional features of the animals [1,2,3,4] and greatly reduces milk production [5].The main income in Italian dairy sheep farms comes from milk (72%), followed by milk-fed or light lamb sales (21%), and subsidies (7%) [6]. The natural and semi-natural pastures in the central Apennines in Italy are used as trophic resources for zootechny, but the increase in summer aridity causes a decrease in the pastoral value of the grasslands; it is registering an anticipation of the moment of pasture maximum flowering and a shortening of the period between maximum flowering and maximum dryness of pastures This fact reflects on a lower availability of both forage quality and quantity; the increase in drought stress is detrimental to the sustainability of extensive sheep farms because it affects the morpho-functional features of the animals [1,2,3,4] and greatly reduces milk production [5]. Some adipokines, such as adiponectin, leptin and apelin [9], intervene in mammary growth, function and lactogenic regulation [10,11]

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