Effects of supplementing humates on rumen fermentation in Holstein steers

Humates have nitrogen-binding qualities that could prove to be beneficial in the retention of ammonia nitrogen in the rumen of Holstein steers fed a high-concentrate finishing diet. Therefore, four ruminally fistulated Holstein steers were used in a 4 x 4 Latin Square design to determine the effects of humates (HA) on serum urea nitrogen, rumen pH, rumen ammonia nitrogen and volatile fatty acid (VFA) production. Steers were randomly assigned one of four treatments; a control (0), 5.0, 10.0 or 15.0 g/kg HA (DM basis). The steers were fed ad libitum for 21 days prior to sample collection with dry matter intake (DMI) determined from days 14 to 21. For DMI, a quadratic response was observed; lowest for 5.0 and 10.0 g/kg HA and highest for 15.0 g/kg HA compared to control. Treatment by time interactions was not observed. No treatment differences were observed for total VFA concentrations (mM), or molar proportions of acetate, propionate, butyrate or valerate, but there was a quadratic response observed for butyrate. It was determined that HA do not alter rumen fermentation of Holstein steers fed high-concentrate diets.Keywords: Humic acid, volatile fatty acids, high-concentrate diets, serum urea nitrogen, intak

Effects of ovariectomy and anabolic steroid implantation on the somatotrophic axis in feedlot heifers

A 2 x 2 factorial experimental design was used to evaluate effects of ovariectomy and implantation (200 mg trenbolone acetate and 28 mg estradiol benzoate; Synovex-Plus) on the performance, serum urea nitrogen, serum insulin like growth factor -1 (IGF-1), and mRNA expression of hepatic IGF-1, growth hormone (GH) receptor and estrogen receptor-α as well as pituitary GH, estrogen receptor-α and GH releasing hormone receptor in feedlot heifers. Thirty-two British x Continental heifers were randomly assigned to either an ovariectomized (OVX) or intact group and then to either a control group or a Synovex-Plus implant group. Heifers were fed a 900 g/kg concentrate steam-flaked maize based diet for 42 d. Liver biopsies were taken before OVX for baseline expression of IGF-1, GH receptor and hepatic estrogen receptor-α, which did not differ between treatment groups. Blood and body weight (BW) were taken on d 0, 28, and 42 and one heifer/pen was slaughtered on d 42 for liver and pituitary tissue samples. Initial and final BW did not differ due to OVX or implant. No gender x treatment interaction was observed for average daily gain (ADG) or final BW. Neither OVX nor implant affected ADG for the final 14 d of the feeding period, but 28 and 42 d ADG were greater in implanted than in control heifers. No 2- or 3-way interactions with day were observed for serum urea nitrogen. Serum urea nitrogen was greater in control heifers than in implanted heifers, but gender had no effect. Both implant and OVX increased serum IGF-1 and a gender x treatment interaction was observed. Neither gender nor implant treatment affected hepatic estrogen receptor-α, hepatic IGF-1, hepatic GH receptor, GH releasing hormone receptor, GH, or pituitary estrogen receptor-α. Data indicate that implanting heifers with Synovex-plus increases serum IGF-1, but the reason for this increase cannot be explained by mRNA expression of key somatotropic genes in the present study.A 2 x 2 factorial experimental design was used to evaluate effects of ovariectomy and implantation (200 mg trenbolone acetate and 28 mg estradiol benzoate; Synovex-Plus) on the performance, serum urea nitrogen, serum insulin like growth factor -1 (IGF-1), and mRNA expression of hepatic IGF-1, growth hormone (GH) receptor and estrogen receptor-α as well as pituitary GH, estrogen receptor-α and GH releasing hormone receptor in feedlot heifers. Thirty-two British x Continental heifers were randomly assigned to either an ovariectomized (OVX) or intact group and then to either a control group or a Synovex-Plus implant group. Heifers were fed a 900 g/kg concentrate steam-flaked maize based diet for 42 d. Liver biopsies were taken before OVX for baseline expression of IGF-1, GH receptor and hepatic estrogen receptor-α, which did not differ between treatment groups. Blood and body weight (BW) were taken on d 0, 28, and 42 and one heifer/pen was slaughtered on d 42 for liver and pituitary tissue samples. Initial and final BW did not differ due to OVX or implant. No gender x treatment interaction was observed for average daily gain (ADG) or final BW. Neither OVX nor implant affected ADG for the final 14 d of the feeding period, but 28 and 42 d ADG were greater in implanted than in control heifers. No 2- or 3-way interactions with day were observed for serum urea nitrogen. Serum urea nitrogen was greater in control heifers than in implanted heifers, but gender had no effect. Both implant and OVX increased serum IGF-1 and a gender x treatment interaction was observed. Neither gender nor implant treatment affected hepatic estrogen receptor-α, hepatic IGF-1, hepatic GH receptor, GH releasing hormone receptor, GH, or pituitary estrogen receptor-α. Data indicate that implanting heifers with Synovex-plus increases serum IGF-1, but the reason for this increase cannot be explained by mRNA expression of key somatotropic genes in the present study. Keywords: Synovex-plus, mRNA, genderSouth African Journal of Animal Science Vol. 38 (3) 2008: pp. 207-21