G.F. Hartnell

Physiological responses to repeated endotoxin challenge are selectively affected by recombinant bovine somatotropin administration to calves.

The study determined 1) whether the pretreatment of calves with recombinant bovine somatotropin (bST, sometribove) would alter the change in packed cell volume (PCV), rectal temperature (RT), and the plasma concentrations of Ca2+, Fe2+, glucose (G), urea N (PUN), nonesterified free fatty acids (NEFA), albumin (ALB), and blood cell populations after endotoxin challenge (EC) and 2) whether the natural development of physiologic tolerance to repeated EC was affected by bST. Twelve steer beef calves were assigned to either control (-bST) or +bST treatment in equal numbers. Calves were injected intramuscularly with either HCO3(-)-buffered saline or bST (0.1 mg/kg) daily for 5 d. On Day 6, the first EC was administered (Escherichia coli, 055:B5, 0.2 microgram/kg, intravenous bolus in pyrogen-free saline). Saline or bST injections were continued from Day 7 up to the repeat of EC on Day 11. RT and PCV were measured hourly through 12 and 6 hr, respectively. Jugular blood was obtained at 0, +1, 2, 3, 4, 6, 8, 12, and 24 hr relative to each EC. bST had no effect on the increase in RT, the hyperglycemic phase of the G response, the biphasic change in Fe2+, or increases in NEFA and PUN. PCV increased after each EC only in -bST. The mean decrease in G during the hypoglycemic phase was less in +bST. Hypocalcemic responses were significantly less in +bST. ALB concentrations decreased after each challenge; the response was unaffected by bST. CD2+, CD4+, and CD8+ T-lymphocyte populations were unaffected by bST and EC. Overall, the magnitude of change in all plasma variables was less after the second EC compared with the first, either in terms of magnitude or duration. The data suggest that the treatment of calves with bST diminishes the magnitude of hypoglycemic, hypocalcemic, and PCV changes after EC and does not compromise fever response, changes in blood cell populations, or tolerance to repeated EC.

Alfalfa Containing the Glyphosate-Tolerant Trait Has No Effect on Feed Intake, Milk Composition, or Milk Production of Dairy Cattle

The objective of this experiment was to assess if feeding glyphosate-tolerant alfalfa affects feed intake, milk composition, or milk production of dairy cows. One alfalfa (Medicago sativa), variety expressing the CP4 EPSPS protein and grown in southeastern Washington State was harvested at the late vegetative stage as hay. Three commercial conventional varieties of alfalfa hay of similar nutrient composition and harvested in the same geographic region were fed to cows as controls. The commercial hays were selected to be similar in crude protein [18% of dry matter (DM)] and neutral detergent fiber (40% of DM) to the glyphosate-tolerant hay. Sixteen multiparous Holstein cows were fed diets containing alfalfa hay (39.7% of diet DM) from either the glyphosate-tolerant alfalfa, or 1 of the 3 conventional varieties. Diets contained at least 15.7% crude protein and 29% neutral detergent fiber. Experimental design was a replicated 4 x 4 Latin square. Periods were 28 d and feed intake, milk yield, and milk composition were summarized over the last 14 d of each period. Daily milk yield (38.0 kg) and 4% fat-corrected milk (34.7 kg) were not affected by treatment. Milk fat (3.44%) and milk true protein (2.98%) were also not affected by source of hay. Milk lactose (4.72%) and soldis-not-fat (8.5%) did not differ due to treatment. Dry matter intake was similar across treatments (24.4 kg/d). These results are consistent with data from feeding trials with other glyphosate-tolerant crops and previously reported compositional comparisons of glyphosate-tolerant alfalfa with controls. Milk production, milk composition, feed intake, and feed efficiency were not affected by feeding diets that contained nearly 40% glyphosate-tolerant alfalfa hay to lactating dairy cows.

Performance of growing-finishing pigs fed diets containing Roundup Ready wheat (MON 71800), a non-transgenic genetically similar wheat, or conventional wheat varieties

The objective of this study was to compare growth performance and carcass and meat quality characteristics of growing-finishing pigs fed diets containing Roundup Ready wheat (MON 71800), compared with the non-transgenic genetically similar parental control wheat (MON 71900), and four commercial varieties of non-transgenic wheat (HANK, Westbred 926, Express and Zeke). The study was carried out as a split-plot design with a 2 × 6 factorial arrangement of treatments (two genders and six wheat varieties). A three-phase dietary program was used; all diets were formulated with a fixed level of wheat inclusion (70%, 80% and 85% for the Grower, Finisher I and Finisher II phases, respectively). A total of 240 commercial hybrid pigs (equal numbers of barrows and gilts) were grown from 29.5 ± 0.29 to 114.5 ± 2.23 kg live weight in single-gender pens (barrows or gilts) of five pigs (eight pens per dietary treatment) with ad libitum access to feed and water throughout the study. At the end of each dietary phase and of the test period, ultrasound measurements were taken at the 10th rib. Animals from the transgenic (MON 71800) and non-transgenic (MON 71900) treatments were harvested at the end of the study and carcass and meat quality measurements were taken. Pigs fed the six wheat varieties had similar (P > 0.05) feed intake, live weight gain, gain : feed ratio and ultrasound measures of backfat thickness and longissimus muscle area. There was a wheat variety × gender interaction (P < 0.05) for longissimus fat content. Gilts fed the transgenic wheat had higher (P < 0.05) longissimus fat content than those fed the non-transgenic control wheat; however, for barrows there was no effect (P > 0.05) of wheat variety on longissimus fat content. However, there was no effect (P > 0.05) of wheat variety on other longissimus muscle quality or composition measures. Gilts had lower (P < 0.01) feed intake, growth rate and backfat thickness, and similar gain : feed ratio (P > 0.05) compared to barrows. This study, with growing-finishing swine, suggests that the Roundup Ready wheat (MON 71800) resulted in equivalent animal performance to conventional wheat.

Performance of dairy cows fed silage and grain produced from second-generation insect-protected (Bacillus thuringiensis) corn (MON 89034), compared with parental line corn or reference corn

Corn grain and corn silage are major feed components in lactating dairy cow rations. Bacillus thuringiensis (B.t.) is a naturally occurring soil bacterium that produces a protein that is toxic to lepidopteran insects that may damage plant tissues and reduce corn quality and yields. During each of the four 28-d periods, cows were offered 1 of 4 rations in which the corn grain and silage originated from different corn hybrids: a nontransgenic corn control (from hybrid DKC63-78; Monsanto Co., St. Louis, MO), a B.t. test substance corn (MON 89034 in hybrid DKC63-78; Monsanto Co.), and 2 commercial nontransgenic reference (Ref) hybrids: DKC61-42 (Ref 1) and DKC62-30 (Ref 2; Monsanto Co.). Sixteen multiparous Holstein cows averaging 110 ± 21 d in milk and weighing 684 ± 62.3 kg were blocked by days in milk and milk yield and randomly assigned to one of four 4 × 4 Latin squares. Diets were formulated to contain 36.4% corn silage and 16.3% corn grain. Dry matter intake was greater for cows consuming B.t. corn (26.6 ± 0.59 kg/d) compared with the control, Ref 1, and Ref 2 corn diets (25.4, 25.0, and 25.6 ± 0.59 kg/d, respectively). Milk yield, fat yield, and percentage of fat (36.8 ± 0.98 kg/d, 1.22 ± 0.05 kg/d, and 3.3 ± 0.10%), milk protein yield and percentage of protein (1.11 ± 0.03 kg/d and 3.01 ± 0.05%), milk urea nitrogen concentration (14.01 ± 0.49 mg/dL), and 3.5% fat-corrected milk yield (35.7 ± 1.07 kg/d) were not different across treatments. The results from this study show that lactating dairy cows that consume B.t. corn (MON 89034) do not differ from lactating dairy cows that consume nontransgenic corn in milk yield, 3.5% fat-corrected milk per unit of dry matter intake, or milk components.