Ten calves less than 14 h of age (average 8.6 h) were anaesthetized, and the intestine was ligated into segments 10 cm in length at 3-cm intervals beginning 1.8 m anterior of the ileocecal junction and proceeding proximally. Seven treatments were assigned in random order to segments in three successive sections of the small intestine. Segments received 1 ml of viable bacteria of intestinal origin, autoclaved bacteria of intestinal origin, or sterile microbiological broth at zero time; then after 4 h they were injected with iodine-125 labeled gamma-globulin. After an additional 1.5 h, the experiment was ended and uptake assayed. Two treatments measured anaerobic microbial growth after 4 h incubation with 1 ml of either sterile broth or live bacteria culture. Residual [iodine-125] gamma-globulin was measured in segments receiving 1 ml of sterile broth or live bacteria culture with 5.5-h incubation followed by 15-s exposure to labeled gamma-globulin. Uptake was lowest in segments receiving live bacteria as compared to segments receiving sterile inocula. Number of bacteria per gram of tissue was correlated negatively with uptake. Low corticosteroids in serum were associated with low uptake of gamma-globulin.

Multiparous Holstein cows at six universities were utilized to examine effects of ruminally protected methionine and lysine on lactational performance. Three hundred and four cows began the study; 259 cows were included in the production analysis. Following a 21-d standardization period, cows received a basal diet of corn silage and ground corn supplemented with one of five dietary treatments, which were supplements of soybean meal or corn gluten meal, the latter with zero and three combinations of protected methionine and lysine (methionine; methionine and lysine; methionine and double (2x) lysine). Treatment effects were evaluated during early, mid, late, and total lactation (22 to 112, 113 to 224, 225 to 280, and 22 to 280 d postpartum, respectively). On a DM basis, ratios of forage to concentrate (50:50, 60:40, and 70:30) increased, and dietary CP (16.0, 14.5, and 13.0%) decreased during the three periods of lactation. Amount of amino acid supplementation also decreased (15, 12, and 9 g/d methionine; 20, 16, and 12 g/d lysine; and 40, 32, and 24 g/d 2x lysine) with period of lactation. Actual and least squares means for milk, FCM, and milk protein yields were greater for soybean than for corn gluten meal during early, mid, and total lactation. In addition, these variables responded linearly to lysine in early lactation. Response to lysine was quadratic during mid and total lactation for these variables. Differences in nutrient intake explained production responses to protein sources but not to lysine. Serum amino acid responses primarily reflected differences in dietary protein source and rumen-protected amino acid.

Fifty-five multiparous Holstein dairy cows were used to evaluate the singular and combined effects of somatotropin and monensin treatments during the late dry period on postpartum metabolism and production. Treatments were 1) control (C); 2) injection of exogenous bovine somatotropin (bST); 3) TMR top dressed with 300 mg of monensin/day (M); and 4) monensin and somatotropin in combination (bST+M) during the last 28 days before expected parturition. A 500-mg subcutaneous injection of sustained release somatotropin was administered adjacent to the tail head at d -28 and -14 relative to expected calving. Diet and management were the same for all cows after parturition. Production and intake were measured daily until 63 d in milk. Milk composition, blood metabolites, and body weight and condition score were measured weekly. Prepartum glucose, nonesterified fatty acid, and blood urea nitrogen concentrations were not different among treatments. Cows on the M treatment tended to have greater dry matter intake postpartum than those on the C treatment and 30% lower plasma nonesterified fatty acid concentrations during wk 1 postpartum than all other treatments. Milk yield and milk fat yield were not different among treatments, but milk fat percent tended to be lower for the bST+M treatment than the C treatment. Changes in plasma amino acid concentrations were consistent with mobilization of skeletal muscle protein, possibly for use in gluconeogenesis. Results from this study provide evidence that prepartum feeding of monensin reduced plasma nonesterified fatty acid concentrations and may improve glucose metabolism of the periparturient dairy cow.

No abstract

The objectives were to determine effects of prepartum protein intake and dietary amino acid balance on production, adaptations in body fat and protein, amino acid concentrations, and, indirectly, body protein breakdown in early lactation. Multiparous Holstein cows (n = 42) were fed diets containing 11 or 14% crude protein with or without 20 g/d of methionine hydroxy analog for 21 d prepartum and then fed a common diet of 17% crude protein for 120 d postpartum, with or without 50 g/d of methionine hydroxy analog. Dry matter intake postpartum averaged 25.4 kg and milk production 41.6 kg. Cows fed the 14% CP diet ate 0.7 kg more dry matter and gave 1.7 kg more milk than those fed the 11% diet postpartum, but this difference was not significant. Cows fed methionine hydroxy analog prepartum lost less body protein from -14 to 60 d in milk. From d 60 to 120, body fat increased 8.5 and 11.5 kg for low and high protein groups and body protein increased 0.5 and 1.0 kg. Serum concentrations of branched chain amino acids fell 17% in the first few weeks postpartum, lysine fell 15%, histidine fell 16%, methionine increased 20%, and cysteine increased 30%. The ratio of serum 3-methylhistidine to creatinine was determined to indicate muscle protein degradation. An increase in this ratio at 7 d postpartum indicated increased body protein breakdown, there was no effect of prepartum ration. Increased protein intake prepartum may allow more feed intake and milk production postpartum, and supplementing a methionine analog on a ration already balanced in methionine by contemporary models may spare body protein.

Early lactation in the dairy cow is associated with an increased demand for energy that can only be met by hormone-mediated partitioning of nutrients. The purpose of this study was to determine adaptive responses of basal and glucose-stimulated glucagon (IRG), insulin (IRI), and growth hormone (GH) concentrations to early lactation. Blood was collected via jugular cannulas from nonpregnant nonlactating (NPNL) cows and cows 14 days antepartum (AP) and 5 and 30 days postpartum (PP). Basal concentrations of IRI decreased with lactation, IRG was essentially unchanged, and GH was increased with lactation. The molar IRI/IRG (I/G) ratio was decreased from 4.6 at day 14 AP to 1.3 at day 30 PP. The effects of exogenous glucose (0.56 mM/kg body wt) on IRI were greatest during pregnancy and declined with lactation. IRG responses to glucose were similar except in NPNL cows, which had a minimal but prolonged IRG inhibition, GH responses to glucose infusion were absent in NPNL cows and were most significant at 5 days PP. The decreased I/G and elevated GH concentrations suggests that both IRG and GH play a role in nutrient partitioning during early lactation.

No abstract

No abstract