Proteolytic activity during the absorption of [¹³¹I]γ‐globulin in the new‐born calf

Abstract

SUMMARY1. Proteolytic activity within the small intestine of unsuckled calves less than 20 hr of age, anaesthetized with sodium pentobarbitone, has been assessed from the break-down of [131I]bovine serum y-globulin infused into the duodenum.2. Absorption of [131I]y-globulin was measured by analysis of venous blood, the levels of radioactivity attained in which were comparable with those when [131I]PVP K.60 (mean mol.wt. 160,000) was administered. When lymph collected from the thoracic duct during the absorption of [131I]y-globulin was injected into the femoral vein, the levels of radioactivity in the blood were close to those expected if the labelled material in the lymph had been retained within the plasma. These observations suggested that [131I]y-globulin was absorbed into the circulation of the anaesthetized young calf without significant break-down.3. Gel-filtration of lymph and plasma from calves fed [13I]y-globulin has confirmed that proteolysis before and during absorption was slight, since little 131I labelled material of low mol.wt. was found.4. Gel-filtration of the contents of the alimentary tract from calves fed [1311]y-globulin showed that some hydrolysis occurred in the abomasum and duodenum and that this was reduced by barbiturate anaesthesia. Protein break-down in the terminal ileum was slight both in the conscious animal and in animals anaesthetized with sodium pentobarbitone.

The break‐down of [131I]γ‐globulin in the digestive tract of the new‐born pig

“…The techniques involved here have previously been described in detail (Hardy, 1969b to pass through the origin, and theoretical regression for a 1200 g pig are also shown (see Hardy, 1969b J311 labelled fragments which were lost from the plasma. In contrast, in the young calf protein break-down was less marked (Hardy, 1969c) and in consequence the blood percentage radioactivity observed when [13JI]-bovine serum y-globulin was fed was higher than that seen in pigs (Fig. 2).…”

“…If this was indeed the case, it can be related to the high concentration of immune globulin and total protein in sow colostrum taken immediately after parturition (Norbring, 1957;Payne & Marsh, 1962). Protein break-down in the digestive tract of the new-born calf is less intensive than that in the new-born pig (Hardy, 1969c) and the immune globulin and total protein concentrations in bovine colostrum are correspondingly less than those in sow colostrum.…”

Effects of feeding pregnant beef cows selenium-enriched alfalfa hay on selenium status and antibody titers in their newborn calves

“…In cattle, IgG1 is the predominant immunoglobulin isotype in colostrum and is derived from serum (Butler, 1983;Baumrucker et al, 2010). Calves are born with a digestive tract that facilitates absorption of colostral proteins instead of degrading them (Hardy, 1969). The level of proteolytic activity is low and further decreased by trypsin inhibitors in colostrum (Quigley et al, 1995).…”

Apparent efficiency of immunoglobulin absorption in newborn calves orally treated with zeolite

“…Among those mechanisms two could have impact on the AEA% value in newborn calves: 1) ammonia binding effect, which eliminates toxic effects of NH4 + produced by intestinal microbial activity, and 2) slowing the passage rate of digesta trough the intestine. Regarding the first mechanism of ammonia binding it could eliminate negative effects of microbial destruction of proteins which are abundant in colostrum, and could be further increased thanks to the lower rate of proteolytic enzyme activity in newborn calves intestine (Hardy, 1969;James et al, 1978). Reduction of ammonia toxic effects could also contribute to the increased survival rate and pinocytotic activity of early postnatal enterocyte population that has the unique ability to absorb intact macromolecules.…”