Changes in free amino acid profile of red snapper Lutjanus campechanus, eggs, and developing larvae.

The free amino acids (FAA) profile was determined for newly fertilized eggs and resultant larvae from wild-caught red snapper Lutjanus campechanus induced to spawn with hCG. Yolk sac and oil globule volumes of eggs and larvae were monitored over time from digital photographs. FAA profiles of the eggs and larvae were measured in picomoles (pmol) of FAA/mg of eggs by HPLC. Newly fertilized eggs had a mean total FAA content of 21.72 +/- 3.55 nmoles/egg (92.81 +/- 9.71 nmoles/mg eggs). Leucine, valine, lysine, and isoleucine were the most abundant essential FAA comprising 35.9% of the total FAA. Alanine, serine, asparagine, and glycine were the most abundant non-essential FAA comprising 34.2% of the total FAA. At 24 h post-hatch (hph) the mean total FAA had decreased by 81% since egg fertilization. The bulk of the FAA decrease was between the time of hatch and 12 hph. Only 8.5 +/- 1.5% of the initial concentration in fertilized eggs of isoleucine, 9.7 +/- 2.5% of arginine, and 9.9 +/- 2.0% of threonine remained at 12 hph. Among the non-essential FAA, alanine dropped the most by 12 hph with 4.6% of the concentration found in a recently fertilized egg remaining, while cysteine had increased 254.7 +/- 26.2%. The yolk sac volume decreased rapidly in the first 12 hph and was further reduced 77.0 +/- 2.5% from 12 to 24 hph. The oil globule depletion rate was a more linear decline from fertilized egg to 36 hph.

Amino acid supplementation of hydrolyzed feather meal diets for finisher pigs.

The objective of this study was to determine the possibility of replacing soybean meal (SBM) in finisher pig diets completely with hydrolyzed feather meal (FM). Forty-five gilts and 45 castrated males (57.8+/-0.8 kg of BW; 3 gilts or 3 castrated males/pen) were randomly assigned to 5 finisher-1 diets with 6 pens per diet. At an average pen BW of 81.0+/-1.4 kg, pigs were offered finisher-2 diets. Corn-SBM, finisher-1 and finisher-2 positive control (PC) diets were formulated to contain 6.1 and 4.7 g of apparent ileal digestible (AID) Lys/kg, respectively. Corn-FM negative control (NC) diets were formulated to be iso-N to the PC diets. The NC diets were supplemented with Lys and Trp (NRC; NC + Lys and Trp) to alleviate apparent deficiencies based on AID AA in FM reported by the 1998 NRC. In addition, the NC diets were supplemented further with the third limiting AA, Thr (40+3AA; NC + Lys, Trp, and Thr), and fourth and fifth limiting AA, His and Ile (40+5AA; NC + Lys, Trp, Thr, His, and Ile), based on the assumption that the apparent ileal digestibility of all indispensable AA in FM is 40%. Pigs had ad libitum access to feed and water. At the end of the study (112.1+/-1.8 kg), blood samples were collected from all pigs before slaughter. As expected, overall ADFI, AID Lys (representing indispensable AA) intake (LysI), ADG, and G:F were greater and BW gain:LysI (G:LysI) was less in pigs fed the PC diet than those fed the NC diet (P<0.001). Pigs fed the NRC diet grew slower than those fed the PC diet (P=0.004), and their G:LysI tended to be less than those fed the PC (P=0.083) or the 40+3AA and 40+5AA diets (P=0.094). Greater fat-free lean percentage (P=0.005), fat-free lean gain (LG; P<0.001), and LG:F (P<0.001) were observed in pigs fed the PC diet compared with those fed the NC diet, but their LG:F or LG:LysI was similar to those fed the NRC diet. However, LG:F (P=0.030) and LG:LysI (P=0.028) were greater in pigs fed the 40+3AA and the 40+5AA diets than those fed the NRC diet. Pigs fed the 40+5AA diet tended to utilize AID Lys more efficiently for LG than those fed the 40+3AA diet (P=0.068). Subjective meat color (P<0.001), firmness (P=0.004), and marbling (P<0.001) scores were greater in pigs fed the 40+5AA diet than those fed the 40+3AA diet. Diets seemed to have no clear effect on the weight of liver, kidney, and heart or serum urea N and triacylglycerides. Pigs fed the PC diet had more serum albumin and total protein (P<0.001), but less glucose (P=0.031) and cholesterol (P<0.001) than those fed the NC diet. Serum total protein was greater (P=0.031) in pigs fed the 40+5AA diet than those fed the 40+3AA diet. The results indicated that the corn-FM diets were not as effective as the corn-SBM diet in supporting BW gain of finisher pigs. However, the results seemed to indicate that pigs fed the corn-FM diet supplemented with the necessary AA can utilize feed and AA for BW gain and lean gain as efficiently as those fed the corn-SBM diet. Further research is needed to explore fully the optimal AA supplementation strategy to effectively utilize FM for pig production.

The effect of dietary copper supplementation on fatty acid profile and oxidative stability of adipose depots in Boer x Spanish goats.

A feeding trial was designed to examine the effects of copper sulfate pentahydrate (CuSO(4).5H(2)O) on the fatty acid composition and oxidative stability in muscle and adipose tissues of Boer x Spanish goat kids. Fifteen (n = 5 per treatment) goats were fed 0, 100, or 200 mg of supplemental Cu per day as copper sulfate for 98 d. The animals were slaughtered, and LM, s.c. adipose from the sternal region, and mesenteric adipose tissues were collected. Total lipids were extracted with chloroform:methanol (2:1), methylated and isolated via GLC from all tissues. The subsequent peaks were then positively identified by mass spectrometry. Thiobarbituric acid-reactive substances were measured also. In s.c. adipose, dietary Cu significantly decreased C14:0 (P = 0.03) and C16:0 (P = 0.01). In muscle, C15:0 (P = 0.03) was linearly increased by Cu. Dietary Cu supplementation did not influence oxidative stability in goat muscle or s.c. adipose. Copper supplementation at 200 mg/d resulted in a significant increase in malondialdehyde in mesenteric adipose (P = 0.01) compared with the 0 or 100 mg/d groups. These results indicate that lipid composition may differ from depot to depot and that depending on the depot, dietary Cu seems to elicit a variable response on the fatty acid composition.

Short commuunication: Effect of dietary protein depletion and repletion on skeletal muscle calpastatin during early lactation.

Sixteen multiparous Jersey cows were assigned at calving to one of 4 dietary treatments. An 18% crude protein (CP) diet was fed as a total mixed ration through 30 d in milk (DIM), and beginning at 31 DIM a 9, 12, 15, or 18% CP diet was fed through 58 DIM (depletion). All cows were then fed the 18% CP diet until 84 DIM (repletion). Muscle biopsies were taken under local anesthesia at 49 and 84 DIM from the semitendinosus muscle. Milk production, DMI, and milk component contents were measured. Calpain and calpastatin contents of muscle taken at biopsy were evaluated using Western blotting techniques. Milk production and milk protein content were reduced during the depletion period by decreasing dietary protein. Diet had no effect on milk fat content or DMI. During repletion, DMI was affected by dietary treatment. Western blots of muscle extracts indicated no differences in calpain content at any stage of the experiment or in calpastatin content of muscle at 49 DIM. However, at 84 DIM, calpastatin (135 kDa) was lower or undetectable in cows fed either the 9 or 12% CP diets from 31 to 59 DIM. Bands for a 110-kDa degradation product of calpastatin were present in some cows fed the 9, 12, and 15% CP diets during the depletion period. Results indicate a change in skeletal muscle calpain/calpastatin proteolytic system during protein repletion following depletion with diets of less than 15% CP during early to peak lactation in dairy cows.

Adaptations in body muscle and fat in transition dairy cattle fed differing amounts of protein and methionine hydroxy analog.

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.

Effect of dietary ascorbyl-2-phosphate on immune function after transport to a feeding facility.

Effects of dietary ascorbyl-2-phosphate on immune function after a 210-km trip were measured in 18 Holstein heifers. After transport on d 0, 10 g of ascorbyl-2-phosphate each were added to the diets of 10 heifers, whereas eight heifers were fed a control diet. Plasma cortisol concentrations increased by an average of 25.6 microgram/ml on d 0 following transport, but by d 7 after transport had decreased to pretransport levels. Average daily gain was lower in heifers fed ascorbyl-2-phosphate from d 28 to 49 d after transport, but did not differ over the entire study. Feeding ascorbyl-2-phosphate maintained plasma ascorbate concentrations on d 7 post-transport, which decreased in control heifers. Plasma keyhole limpet hemocyanin antibody titers were significantly higher in control heifers from d 7 to 49. Mononuclear leukocyte proliferation responses were decreased on d 0 in lymphocytes stimulated by mitogens, with pokeweed mitogen-stimulated cells showing less of a response than cells stimulated by the other mitogens. In the absence of mitogens, dietary ascorbyl-2-phosphate increased basal 3H-methyl thymidine incorporation by cultured lymphocytes. Across diets and mitogens, lymphocytes treated with cortisol showed decreased 3H-methyl thymidine incorporation. Transportation acted as a stressor, as evidenced by the increased plasma cortisol levels at d 0 immediately after transport, but immunological effects were not apparent by d 7. Feeding ascorbyl-2-phosphate maintained plasma ascorbate concentrations on d 7, but had negative effects on immune responses posttransport.

Effects of prepartum somatotropin and monensin on metabolism and production of periparturient Holstein dairy cows.

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.

Effects of dietary protein on whole-body protein turnover and endocrine function in young-adult and aging dogs.

Thirty-six adult female Beagles averaging 2 (young-adult) or 8 (geriatric) yr of age were used to assess the effects of graded levels of dietary protein (16, 24, or 32%) on endocrine-controlled regulation of whole-body protein turnover. Rates of whole-body protein synthesis (WBPS) and whole-body protein degradation (WBPD) were estimated using orally administered 15N-glycine and total excreta collection. Although N balance was similar for all dogs, N flux through the metabolic pool increased linearly (P < 0.05) as protein intake increased. Rates of WBPS, WBPD, or the difference between them were not influenced by age (P > 0.10). A quadratic increase (P < 0.05) in WBPS and WBPD was observed in response to dietary protein. Serum insulin-like growth factor-I (IGF-I), IGF-I-binding protein 3, and total IGF-I-binding proteins were higher (P < 0.05) in geriatric dogs than in young-adult dogs regardless of protein intake. These results indicate that dietary protein in excess of 16% may not be required to maintain N balance in young-adult and aging dogs despite the linear increase in N flux through the metabolic pool. Furthermore, age-induced changes in endocrine functionality may differ between dogs and other species.

Growth performance and carcass traits of pigs subjected to marginal dietary restrictions during the grower phase.

Sixty-four individually housed pigs were used to investigate the effect of amino acid content of finisher diets on growth performance of pigs subjected to marginal dietary amino acid restrictions (80% of the 1988 NRC lysine recommendation) during the grower phase. In each of the two trials, low- and high-amino-acid grower diets (.421 and .765 g lysine/MJ DE, respectively) and four finisher diets (.421, .516, .612, and .707 g lysine/MJ DE) were randomly assigned within sex to 16 gilts and 16 castrated males weighing 23.0 +/- 2.0 kg in a 2 x 4 factorial arrangement of treatments. The average weight of pigs after a completion of diet change was 50.4 +/- 2.1 kg. All pigs were slaughtered at an average weight of 105.2 +/- 4.1 kg. Ultrasound backfat thickness was measured at the time of diet change and before slaughter. Pigs were allowed ad libitum access to feed and water. During the grower phase, pigs fed the high-amino-acid diet grew faster (P < .001) and more efficiently (P < .001) and had less ultrasound backfat (P < .001) than those fed the low-amino-acid diet. The grower diet had no effect on weight gain during the finisher phase. Consequently, pigs fed the high-amino-acid grower diet had better overall weight gain (P < .01) than those fed the low-amino-acid diet. The rate of lean accretion was, however, similar between the two groups of pigs. Furthermore, pigs fed the low-amino-acid grower diet seemed to have better carcass quality, as indicated by less ultrasound backfat (P < .01) and larger carcass longissimus muscle area (P < .05). Average and 10th rib carcass backfat decreased linearly (P < or = .05) and lean accretion rate improved linearly (P < .05) as the amino acid content of finisher diets increased, but there was no grower x finisher diet interaction in these and other response criteria. Although no evidence of compensatory weight gain was observed, it is possible that compensatory lean tissue growth may have occurred in pigs subjected to early amino acid restrictions at the expense of fatty tissue growth.

Potassium flux in juvenile striped bass (Morone saxatilis): influence of external concentrations of sodium chloride and calcium.

Whole-body influx and efflux of K(+) were determined for 25-day-old striped bass,Morone saxatilis, in conditions that simulated harvesting fish from ponds. During the first 5h in fresh water with combined high NaCl (80 mM) and low Ca(2+) (0.12 mM) concentrations, a combination that is acutely lethal to this age of striped bass, K(+) influx for fish in 0.07 mM K(+) was 21±1.7 (SEM) compared to 3.4±0.33 nmol g(-1) h(-1) for fish in water with low Na(+) (0.25 mM) or high Ca(2+) (2.5 mM) concentrations. Influx of K(+) was inhibited during the first few hours after fish were placed in flux chambers. Potassium efflux as percentage of(42)K lost per hour was two-fold higher from fish in the high Na-low Ca treatment compared to fish in low concentrations of Na(+) or high concentrations of Ca(2+). Potassium efflux was probably much greater than influx, but exact values for efflux could not be calculated from the data available. Survival of fish in water with high Na-low Ca was not increased by addition of KCl to the water, indicating that the net loss of K(+) was probably not the cause of death.

Abomasal nitrogen flow affects the relationship between dietary nitrogen and insulin-like growth factor-I in growing lambs.

Twelve abomasally cannulated wether lambs were fed isocaloric diets containing 9, 12 or 15% crude protein to determine insulin-like growth factor-I (IGF-I) responses to altered abomasal nitrogen flow and nitrogen status. Lambs were offered 1100 g/d of their respective diets. Voluntary feed consumption was not affected by nitrogen intake. Ruminal and total tract digestibilities of dry matter, organic matter and nitrogen increased linearly (P < 0.05) with increased dietary nitrogen. Abomasal flows of total, bacterial and rumen escape nitrogen increased (linear, P < 0.01), whereas dry matter and organic matter flows decreased (linear, P < 0.01). Total amino acid flow was greater (linear, P < 0.01) in lambs fed additional nitrogen due to increased (linear, P < 0.01) flows of essential and nonessential amino acids. Nitrogen retention and blood urea nitrogen increased linearly (P < 0.01). Serum IGF-I concentrations and relative hybridization intensity of hepatic IGF-I mRNA increased (linear, P < 0.05) as lambs consumed more nitrogen. Serum IGF-I and hepatic IGF-I mRNA were correlated positively (P < 0.05) with nitrogen intake and abomasal flows of nitrogen and various amino acids. These data provide evidence of a relationship between abomasal amino acid flow, as influenced by nitrogen intake, and hepatic gene expression and serum concentrations of IGF-I in growing lambs.

Effects of steroids on the olfactory function of the dog.

Twenty-four (24) mature, mixed breed, healthy dogs weighing from 14.6 kg to 27.6 kg were used to study the effects of various steroids on the olfactory function of the dog using olfactory detection threshold as an index. Two odorants were used, viz; benzaldehyde and eugenol. Of the various steroids used, only dexamethasone produced classical signs of Cushing's syndrome in the dogs. However, all dogs that received either dexamethasone alone or hydrocortisone plus DOCA exhibited a significant elevation in the olfactory detection threshold for both odorants without any observable structural alteration of the olfactory tissue using light microscopy. On the other hand, neither DOCA, hydrocortisone alone, nor any of the vehicles used in the study significantly altered the olfactory function of the dogs. The results show that Cushing's syndrome can be experimentally produced in dogs using exogenous steroids and that this condition diminishes the olfactory capability of the dog without producing classical signs of the disease.

Effect of dietary acid detergent fiber on responses to high environmental temperature.

Twenty-seven multiparous Holstein cows averaging 120.7 DIM, 9 per diet, were assigned at random to 20, 17, or 14% ADF diets of corn, corn silage, and soybean meal, following a covariant period when all cows received the 14% ADF diet. An 18-d period (period 1) of cool weather preceded the onset of high environmental temperature from June 1988 to the end of July 1988 (period 2). Mean daily maximum air temperatures were 35.2, 36.8, and 34.7 degrees C for the covariant period and for periods 1 and 2, respectively. Minimum temperatures were 14.5, 16.0, and 21.5 degrees C. Milk production during both periods was higher, and the decrease in milk production associated with the onset of hot weather was lower, in cows fed the 14% ADF diet. Intake was not affected by diet during period 1 but was lower in cows fed the 17 and 14% ADF diets in period 2 relative to period 1. At any given environmental temperature, DMI was higher in cows fed lower ADF diets. Although DMI declined more rapidly with increasing daily minimum temperature with lower ADF diets, milk production was less sensitive to daily minimum temperature in cows fed the 14% ADF diet.

Responses of dairy cows to supplemental rumen-protected forms of methionine and lysine.

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.

Developmental changes in the regulation of plasma growth hormone concentrations in Holstein calves.

A study was initiated to determine whether development of a functional ruminant digestive system was associated with alterations in plasma growth hormone (GH) concentration. Holstein bull calves were fed milk or milk with grain until studied at the age of 1 month (n = 12). Calves placed on pasture with some grain supplementation were studied at the age of 3 months (n = 6) to determine plasma GH concentration in an animal with fully developed ruminant metabolism. Blood samples were taken at 10-minute intervals for 5 hours, followed by administration of bovine GH-releasing factor (0.075 micrograms/kg of body weight) and subsequent blood sample collection for 1 hour. On the following day, a blood sample was collected via jugular cannula, clonidine (10 micrograms/kg) was administered, and blood samples were subsequently obtained. Data indicated that milk-fed calves had higher mean plasma GH concentration than did either milk/grain-fed or older calves. The difference in mean plasma GH concentration was related to higher secretory pulse amplitude. Pituitary responses to bovine GH-releasing factor did not differ among the 3 groups, but response to clonidine were greater in milk-fed calves than in calves of the other groups. These data indicate that the change from a nonruminant to a ruminant-type gastrointestinal tract, perhaps attributable to subsequent changes in metabolism, may induce changes in hypothalmic function to decrease GH concentration.

Effect of calf housing on plasma ascorbate and endocrine and immune function.

The effect of housing calves in indoor metal pens (1.2 m x 1.2 m) or commercial calf hutches was determined on plasma concentration of cortisol, antibodies, and ascorbate. Six calves per treatment were deprived of colostrum, assigned randomly to treatment, and fed a commercial milk replacer until 56 d of age. Calves housed in hutches had higher plasma IgG concentrations than calves in pens at 42 and 56 d of age. Housing had no effect on plasma IgM concentration. Antibody titers to keyhole limpet hemocyanin injected at 14 and 28 d of age were higher in hutch-housed calves from 21 to 56 d of age. Calves housed in hutches also had lower plasma cortisol concentrations, although cortisol decreased with age in both treatment groups. Plasma ascorbate and ascorbate plus dehydroascorbate were higher in hutch-housed calves. Regression analysis indicated a positive relationship between plasma ascorbate and IgG in metal penhoused calves and a negative relationship in hutch-housed calves. Housing in 1.2 m x 1.2 m metal pens decreases cortisol, plasma ascorbate, IgG, and specific antibody titers in dairy calves relative to calves housed in hutches.

Differential growth hormone responses to glucose and growth hormone releasing hormone in lactating dairy cows.

Dairy cows in early lactation were reported to secrete growth hormone in response to declining glucose concentrations at day 5 but not day 30 post-partum, whereas GH responses to TRH were reported to be enhanced after day 30 post partum. The present study examined GH response following glucose infusion and the effect of GHRH as well as effects of SRIH on GHRH-stimulated GH release. Declining plasma glucose concentrations after glucose infusion stimulated GH release at day 5 post partum but not in nonpregnant, nonlactating cows or in cows at days 30 and 90 post partum. GHRH stimulated GH release on all days tested, but the response was highest at day 30 post partum when compared to other days. Somatostatin infusion inhibited GHRH effects on GH concentrations only at day 30 post partum and in nonpregnant, nonlactating cows. Thus, a differential response of the GH regulatory system could be demonstrated between days 5 and 30 post partum utilizing different stimuli. Evaluation of plasma glucose and free fatty acid concentrations on days 5, 10, 20, and 30 post partum revealed a progressive decrease in FFA but not glucose as lactation progressed. Decreased plasma FFA concentrations were paralleled by a decrease in basal GH, somatomedin-C and epinephrine. Thus, a decline in FFA may be responsible for the disparity between effects of GHRH and glucose on GH release between days 5 and 30 post partum.

Dietary ascorbic acid and immune response in dairy calves.

Colostrum-fed, colostrum-deprived, and colostrum-fed and colostrum-deprived calves fed ascorbic acid (1.75 g/d) in whole, raw milk to 6 wk of age were sampled from 0 to 8 wk of age in order to determine whether ascorbate supplementation would increase plasma Ig concentrations, antibody response to immunization, and disease resistance. Plasma IgG concentrations were lower at 14 and 28 d of age in calves fed ascorbate compared with plasma concentrations in calves not receiving ascorbate supplementation, irrespective of colostrum feeding. Colostrum feeding had no effect on antibody titer to keyhole limpet hemocyanin at any age, but ascorbate-supplemented calves had lower plasma antibody titers to keyhole limpet hemocyanin at 35 and 56 d of age. Calves fed ascorbate had lower clinical scores for diarrhea. Dietary ascorbate does not appear to be immunostimulatory in dairy calves to 56 d of age and appeared to inhibit antibody synthesis. However, at 14 d of age there was an interaction of ascorbate supplementation and colostrum feeding; plasma IgG concentrations were higher in colostrum-deprived calves fed ascorbate then in colostrum-deprived calves not fed ascorbate.

Plasma concentrations of metabolic hormones in high and low producing dairy cows.

Concentrations of insulin, glucagon, growth hormone, adrenocorticotropin, and cortisol were determined in plasma samples obtained at 20-min intervals for 6 h from low and high producing dairy cows at d 30 and 90 postpartum. Four nonpregnant, nonlactating cows also were sampled. Insulin concentrations were reduced at d 30 in both groups of lactating cows compared with concentrations in nonlactating cows; glucagon concentrations were unchanged. The molar insulin: glucagon was reduced at d 30 in both groups and at d 90 for low, but not high producers. Growth hormone concentrations were higher at d 30 in high producers than at d 90, in low producers at d 30, and higher than in nonlactating cows. Cortisol concentrations were lower in high producing cows at d 30 than at d 90 or in nonlactating cows due to a reduced pulse amplitude. No differences were observed for adrenocorticotropin. Reduced molar insulin: glucagon may be an integral response of the cow to lactation, while the difference in the insulin: glucagon for high and low producers at d 90 postpartum may indicate a continued need for a gluconeogenic stimulus in low producers. The elevated growth hormone and low cortisol concentrations likely participate in the enhanced production observed in high producing dairy cows.

Multiple infusions of cloxacillin for treatment of mastitis during the dry period.

Efficacy of multiple and single intramammary infusions of benzathine cloxacillin (500 mg/quarter) were compared for treatment of mastitis during the dry period. Treatments were three infusions, one each at 0, 7, and 14 d into the dry period; one infusion at drying off; and no infusions. Cows were grouped (30/treatment) based on previous mastitis history, mean monthly SCC, mature equivalent milk production, and pathogen detected pretreatment. Infected quarters/cow at parturition, posttreatment were 1.26, 1.6, and 2.35 for multiple, single, and no infusion groups, respectively. Milk production and somatic cell count posttreatment were not affected by treatment. Across all genera of microorganism, 75.5, 73.6, and 52.8% of infections were eliminated in the multiple, single, and no infusion groups, respectively. Primary effect of multiple infusions with cloxacillin in the dry period was to prevent new streptococcal infections. Sensitivity tests on staphylococcal isolates indicated that cloxacillin was still an effective dry cow treatment after 7 yr of use in the herd. Resistance to cloxacillin in approximately half the posttreatment staphylococcal isolates appeared to be nonenzyme (penicillinase) dependent. Multiple dry cow treatments with cloxacillin do not offer any advantage over a single treatment.