The effects of dry extrusion temperature of whole soybeans on digestion of protein and amino acids by steers.

Five Holstein steers (450 kg) with cannulas in the rumen, proximal duodenum, and terminal ileum were used in a 5 x 5 Latin square design to study the effects of extrusion temperature on site of digestion of nitrogenous compounds in whole soybeans. The basal diet contained 50% corn silage, 24% alfalfa hay, 16.6% corn starch, 4.05% ground corn, 1% urea, and 3.4% soybean oil. Raw soybeans or soybeans extruded at 116, 138, or 160 degrees C (diets 116, 138, and 160, respectively) replaced the soybean oil and most of the corn starch in the test diets. Total N (g/d) reaching the duodenum was 232, 293, 285, 308, and 299 for the basal, raw, 116, 138, and 160 diets, respectively. No differences were observed between the raw and extruded soybeans (P = 0.81), or for the linear or quadratic effects of extrusion temperature (P = 0.56 and P = 0.45, respectively). Nonbacterial N (g/d) reaching the duodenum was 63.1, 104.6, 106.7, 101.9, and 113.9 for the same diets, respectively, and was not influenced by extrusion or extrusion temperature. Nitrogen disappearance from the small intestine (g/d) was 150 for the basal diet, 194 for the raw soybean diet, and 187,221, and 213 for the 116,138, and 160 degrees C extruded diets, respectively; no differences were observed between the raw and the extruded soybeans, or for diets containing soybeans extruded at different temperatures. Nitrogen disappearance (% of N entering) from the small intestine was lower (P < 0.05) for steers fed the basal diet than for steers fed the soybean-supplemented diets (64.1 vs 68.5%). No differences (P > 0.10) due to extrusion temperature were detected for flows of individual, essential AA, nonessential AA, and total AA at the duodenum. As extrusion temperatures increased, there were linear increases (P < 0.10) in disappearance (g/d) of all individual AA from the small intestine except for methionine and glycine. Essential, nonessential, and total AA disappearance from the small intestine were increased linearly (P < 0.10) with increasing extrusion temperature. Extrusion of soybeans can protect soy protein against extensive ruminal degradation without compromising intestinal digestibility.

Technical note: a technique for multiple liver biopsies in neonatal calves.

Our objective was to develop a rapid and safe liver biopsy technique that could be repeated on multiple occasions in individual neonatal calves. A pilot study was performed to verify the efficacy of sedation and restraint procedures and to evaluate different biopsy instruments. Following the pilot experiment, a biopsy trocar was fabricated and an experiment was conducted using this procedure. Liver biopsies were performed in neonatal calves on d 4, 9, 15, 21, and 28 of life to evaluate the effect of vitamin A intake on liver vitamin A concentrations. On these days, a single injection of ceftiofur sodium was administered i.m. 1 to 2 h prior to the procedure. Calves were lightly sedated with xylazine and placed on a surgical table in left-lateral recumbency. The right caudo-thoracic area was clipped and scrubbed with an iodophor agent. Following administration of a local anesthetic (lidocaine), a small incision was made in the skin between the 12th and 13th ribs approximately 15 cm from the dorsal midline. The biopsy trocar was inserted through the body wall and peritoneum and introduced into the liver parenchyma, and a liver sample was collected. Following the biopsy, the cutaneous incision was sutured and an antiseptic agent was applied to prevent infection. An i.m. injection of an analgesic was administered 1 h following the procedure to alleviate postsurgical discomfort. Most calves were able to stand within 2 h after the biopsy. The entire procedure, which could be performed by a single individual, usually required about 20 min from initial sedation until skin closure. Although liver samples of up to 500 mg were obtained, most samples weighed 75 to 150 mg (wet weight). A total of 156 liver biopsies were performed on 33 calves. Complications due to the biopsy procedure were observed in only two calves. Therefore, this procedure can be useful for studies designed to monitor changes in liver composition or enzyme activities over time.

Influence of dietary vitamin A content on serum and liver vitamin A concentrations and health in preruminant Holstein calves fed milk replacer.

Evidence has suggested that the current requirement for vitamin A tabulated by the NRC [(approximately 3800 IU of vitamin A/kg of dry matter (DM)] for dairy calves fed liquid diets is too low. The objective of this study was to assess the effects of vitamin A content in milk replacers on serum and liver vitamin A concentrations, growth, and development of clinical signs of vitamin A deficiency in calves. Male Holstein calves were separated from their dams at birth and given standardized feedings of colostrum and milk replacer for 3 d. On d 4, calves were assigned to five groups and fed milk replacer containing 2300, 6200, 9000, 18,300, or 44,000 IU of vitamin A/kg of DM. Liver biopsies and serum samples were taken on d 4, 9, 15, 21, and 28 to monitor vitamin A concentrations. Weekly physical and neurological examinations were performed to monitor the development of deficiency signs. Fecal scores, body temperature, and the presence of nasal and ocular discharge were recorded daily. Liver vitamin A concentrations in calves allotted to diets with 2300 and 6200 IU of vitamin A/kg decreased from d 4 to 28. Calves fed 9000 IU of vitamin A/kg maintained liver stores, while those fed 18,300 and 44,000 IU of vitamin A/kg had significant increases in hepatic vitamin A. A strong negative association existed between incidence of hyperthermic temperatures and vitamin A concentration in the diet; calves fed 2300 IU of vitamin A/kg had approximately three times more hyperthermic readings than did calves fed other treatments. A strong negative association also existed between fecal score and concentration of vitamin A in the diet; calves fed diets containing low vitamin A concentration had a higher incidence of high fecal scores (more watery) than did calves fed diets with higher vitamin A concentrations. Although slight differences were detected in serum retinol concentration, growth performance and incidence of ocular and nasal discharges were not different among treatment groups. Our data indicate that vitamin A concentrations of less than 9000 IU/kg of DM in milk replacers result in declining liver vitamin A stores in preruminant calves. Using the human Dietary Reference Intakes as a model for calculating the requirement, we recommend that the vitamin A requirement for preruminant calves should be increased to 11,000 IU of vitamin A/kg of DM.