The poultry sector is an important and vibrant segment of agriculture in Pakistan with a significant contribution to the national GDP (1.3%). Commercial poultry production in Pakistan started in the 1960’s and has been providing a significant portion of daily proteins to the Pakistani population ever since. During its evolution the industry enjoyed promotional policies of the Government, but has faced several challenges such as disease outbreaks and retail price fluctuations. Despite its important role in the country’s economy, not a single scientific study is available on its evolutionary history. The data available in this regard are scattered and lack reliability. This review is an effort to encompass the history of the overall growth of the poultry industry in Pakistan, its present status (2012 statistics) and future directions and challenges. This article may serve as the basic source of information on Pakistan’s poultry industry achievements. It will also guide poultry experts and policy makers for developing strategic planning for further growth of the industry.

Urea transport across the gastrointestinal tract involves transporters of the urea transporter-B group, the regulation of which is poorly understood. The classical stimulatory effect of CO2 and the effect of short-chain fatty acids (SCFA) on the ruminal recycling of urea were investigated by using Ussing chamber and microelectrode techniques with isolated ruminal epithelium of sheep. The flux of urea was found to be phloretin sensitive and passive. At a luminal pH of 6.4, but not at 7.4, the addition of SCFA (40 mmol/l) or CO2/HCO 3 Ϫ (10% and 25 mmol/l) led to a fourfold increase in urea flux. The stepwise reduction of luminal pH in the presence of SCFA from 7.4 to 5.4 led to a bell-shaped modification of urea transport, with a maximum at pH 6.2. Lowering the pH in the absence of SCFA or CO2 had no effect. Inhibition of Na ϩ /H ϩ exchange increased urea flux at pH 7.4, with a decrease being seen at pH 6.4. In experiments with double-barreled, pH-sensitive microelectrodes, we confirmed the presence of an apical pH microclimate and demonstrated the acidifying effects of SCFA on the underlying epithelium. We confirm that the permeability of the ruminal epithelium to urea involves a phloretin-sensitive pathway. We present clear evidence for the regulation of urea transport by strategies that alter intracellular pH, with permeability being highest after a moderate decrease. The well-known postprandial stimulation of urea transport to the rumen in vivo may involve acute pH-dependent effects of intraruminal SCFA and CO2 on the function of existing urea transporters. pH i; urea transporter-B; short-chain fatty acids; microclimate; volatile fatty acid UREA, POSSIBLY BECAUSE OF its small size, was long thought to move passively across epithelia, depending only on the rate of delivery via blood. The urea permeability of cellular membranes has now been established to be several orders of magnitude above that of lipid membranes (11,92) and is coupled to the expression of specific urea-transporting proteins with channel-like kinetics (7,46,71,81,82,95). Whereas the role that these proteins play in the elegant renal concentrating mechanism has received much attention, their function and regulation in other parts of the body, such as the gut (39), continues to be poorly understood.In contrast to the paucity of our knowledge concerning extrarenal urea transport in humans, we have long known of the ability of camels, cows, or sheep to shift the excretion of urea from the kidney (62, 72) to the gastrointestinal tract (79). The transport of urea through the rumen epithelium was first demonstrated many years ago in vivo and in vitro (16,29,79,89) and the physiological significance is clear: in the rumen, dietary cellulose is broken down by bacteria that utilize ureanitrogen for the synthesis of microbial proteins. After passage into the duodenum, the amino acids of these proteins are absorbed and reach the liver, where new urea for secretion into the rumen can be formed. Recycling of nitrogen via urea secretion into the rumen thus ...

SUMMARYThe forestomachs of cows and sheep have historically served as important models for the study of epithelial transport. Thus, the ruminal epithelium was among the first tissues in which absorption of chloride against an electrochemical gradient was observed, requiring a tight paracellular barrier to prevent back-leakage. However, little is known about ruminal barrier function, despite the considerable implications for ruminant health. The tight junction proteins of the omasum have never been investigated, and no cell culture model exists. We present a new method for the isolation of cells from forestomach epithelia. Protein expression of cells and source tissues of sheep were studied using western blot, PCR and confocal laser scanning microscopy. Supplementary material available online at

Na absorption across the cornified, multilayered, and squamous rumen epithelium is mediated by electrogenic amiloride-insensitive transport and by electroneutral Na transport. High concentrations of amiloride (>100 μM) inhibit Na transport, indicating Na(+)/H(+) exchange (NHE) activity. The underlying NHE isoform for transepithelial Na absorption was characterized by mucosal application of the specific inhibitor HOE642 for NHE1 and S3226 for NHE3 in Ussing chamber studies with isolated epithelia from bovine and sheep forestomach. S3226 (1 μM; NHE3 inhibitor) abolished electroneutral Na transport under control conditions and also the short-chain fatty acid-induced increase of Na transport via NHE. However, HOE642 (30 μM; NHE1 inhibitor) did not change Na transport rates. NHE3 was immunohistochemically localized in membranes of the upper layers toward the lumen. Expression of NHE1 and NHE3 has been previously demonstrated by RT-PCR, and earlier experiments with isolated rumen epithelial cells have shown the activity of both NHE1 and NHE3. Obviously, both isoforms are involved in the regulation of intracellular pH, pH(i). However, transepithelial Na transport is only mediated by apical uptake via NHE3 in connection with extrusion of Na by the basolaterally located Na-K-ATPase. The missing involvement of NHE1 in transepithelial Na transport suggests that the proposed "job sharing" in epithelia between these two isoforms probably also applies to forestomach epithelia: NHE3 for transepithelial transport and NHE1 for, among others, pH(i) and volume regulation.