Diet-dependent immunohistochemical evaluation of connexin 43 in the sheep rumen

The objective of this study was to characterize the immunohistochemical localization of plasma membrane connexin 43 in the rumen of sheep after changing the diet from hay (ad libitum) to a mixed hay/concentrate diet. A total of 24 sheep were fed mixed hay/concentrate for different periods ranging from 0 weeks (control; hay ad libitum) to 12 weeks (1-1.5 kg hay plus 780 g concentrate per day in two equal portions). Using immunohistochemical technique the present study confirmed the existence of plasma membrane connexin 43 in the sheep rumen epithelium. Plasma membrane connexin 43 immunostaining was most intense at the stratum basale and stratum spinosum (suprabasal layer) and decreased iron intensity through stratum spinosum (superficial layers) to stratum granulosum. Meanwhile, stratum corneum was negative. The reaction around the cells gave a syncitial appearance with more apical-immunostaining concentration. Moreover, the present study confirmed a significant effect of concentrate diet on the immunoreactivity of plasma membrane connexin 43 in the rumen of sheep. A very strong degree of antibody reaction was seen in 4 to 12 weeks concentrate-fed groups

Invited Review: Increasing Milk Yield and Negative Energy Balance: A Gordian Knot for Dairy Cows?

The continued increase in milk production during the last century has not been accompanied by an adequate dry matter intake (DMI) by cows, which therefore experience a negative energy balance (NEB). NEB is low and of minor importance at low milk yield (MY), such as for the nutrition of one calf, and under these circumstances is considered “natural”. MY and low DMI around parturition are correlated and are the reason for the genetic correlation between increasing MY and increasing NEB up to 2000 MJ or more for 2–3 months postpartum in high-genetic-merit dairy cows. The extension and duration of NEB in high-producing cows cannot be judged as “natural” and are compensated by the mobilization of nutrients, particularly of fat. The released non-esterified fatty acids (NEFAs) overwhelm the metabolic capacity of the cow and lead to the ectopic deposition of NEFAs as triglycerides (TGs) in the liver. The subsequent lipidosis and the concomitant hampered liver functions cause subclinical and clinical ketosis, both of which are associated with “production diseases”, including oxidative and endoplasmatic stress, inflammation and immunosuppression. These metabolic alterations are regulated by homeorhesis, with the priority of the physiological function of milk production. The prioritization of one function, namely, milk yield, possibly results in restrictions in other physiological (health) functions under conditions of limited resources (NEB). The hormonal framework for this metabolic environment is the high concentration of growth hormone (GH), the low concentration of insulin in connection with GH-dependent insulin resistance and the low concentration of IGF-1, the so-called GH-IGF-1 axis. The fine tuning of the GH-IGF-1 axis is uncoupled because the expression of the growth hormone receptor (GHR-1A) in the liver is reduced with increasing MY. The uncoupled GH-IGF-1 axis is a serious impairment for the GH-dependent stimulation of gluconeogenesis in the liver with continued increased lipolysis in fat tissue. It facilitates the pathogenesis of lipidosis with ketosis and, secondarily, “production diseases”. Unfortunately, MY is still increasing at inadequate DMI with increasing NEB and elevated NEFA and beta–hydroxybutyric acid concentrations under conditions of low glucose, thereby adding health risks. The high incidences of diseases and of early culling and mortality in dairy cows are well documented and cause severe economic problems with a waste of resources and a challenge to the environment. Moreover, the growing public concerns about such production conditions in agriculture can no longer be ignored

An energy-rich diet enhances expression of Na+/H+ exchanger isoform 1 and 3 messenger RNA in rumen epithelium of goat

Rumen epithelial Na(+)/H(+) exchanger (NHE) catalyzes the exchange of extracellular Na(+) for intracellular H(+). Thus, it is of importance in the maintenance of Na and pH homeostasis of rumen epithelial cells. We have tested the hypothesis that an increase in energy and protein intake induces alterations of NHE isoform 1, 2, and 3 (NHE1, NHE1, and NHE3, respectively) mRNA abundance in the rumen epithelium of goats. Goats (n = 26) were randomly allocated to 2 experiments (n = 16 in Exp. 1, and n = 10 in Exp. 2) and fed either peanut straw ad libitum [PNS, n = 8 in Exp. 1, and n = 5 in Exp. 2; 600 kJ of ME/(kg(0.75)·d)] or PNS + concentrate [CF, n = 8 in Exp. 1, and n = 5 in Exp. 2; 1,000 kJ of ME/(kg(0.75)·d)] for 42 d. Concentrate (400 g/d) was given daily (0800 to 1700 h) in 4 equal portions at 3-h intervals. In Exp. 1, the goats were euthanized 2 h after the last portion of concentrate was fed, and in Exp. 2, the goats were euthanized after a fasting period of 16 h. In Exp. 1, goats in the CF treatment exhibited a greater ruminal short-chain fatty acid (SCFA) concentration (140.6 ± 1.30 mM) compared with those in the PNS treatment (114.3 ± 3.11 mM; P < 0.001), and pH decreased from 6.9 ± 0.09 to 5.9 ± 0.04 (P < 0.001). Correspondingly, the mRNA expression of NHE1 and NHE3 in the rumen epithelium was greater by 20% (P = 0.041) and 25% (P = 0.043) for goats in the CF treatment than for those in the PNS treatment. However, in Exp. 2, 16 h of fasting abolished differences in ruminal SCFA concentration, pH, and NHE mRNA expression between goats in the CF and PNS treatments. In both Exp. 1 and 2, a positive correlation was observed between ruminal SCFA concentration and expression of mRNA in NHE1 and NHE3, whereas expression was negatively correlated with ruminal pH. In in vitro studies with isolated rumen epithelial cells from goats fed dried grass, exposure to pH of 6.8 or to 20 mM SCFA increased (P < 0.01) NHE1 and NHE3 mRNA expression, as compared with exposure to pH of 7.4 or the absence of SCFA. A combination of reduced pH (6.8) and SCFA (20 mM) further enhanced (P < 0.05) NHE1 and NHE3 mRNA expression, indicating synergism between an increased concentration of SCFA and low pH (P < 0.05). Messenger RNA expression of NHE2 did not vary in vitro with pH (6.8) or SCFA (20 mM) or in vivo in Exp. 1 and 2. Thus, diet-dependent rumen epithelial NHE1 and NHE3 expression is probably related to ruminal SCFA concentration and pH, but that is not the case with NHE2