Bovine somatotropin.

Bovine somatotropin has the potential to alter profoundly the way that dairy herds are managed and to change the ways in which veterinarians provide services to those herds. This article describes the structure, function, and action of somatotropin. The metabolic effects of somatotropin on dairy cattle are discussed.     

Recombinant porcine somatotropin for sows during late gestation and throughout lactation.

Two experiments were conducted to evaluate whether administration of recombinant porcine somatotropin (pST) to sows (Hampshire-Yorkshire) enhanced lactational performance. In Exp. 1, sows (n = 84) were fed a corn-soybean meal diet (17.8% CP), or a similar diet with 8% added fat, from d 108 of gestation to d 28 of lactation. Half of the sows fed each diet were injected with 6 mg/d of pST from d 108 of gestation to d 24 of lactation. Diets were fed at 2.27 kg/d from d 108 of gestation until farrowing and then were self-fed during lactation. By d 3 of lactation, litter size was standardized at 8 to 10 pigs per litter. Treating sows with pST resulted in a 10-fold increase (P less than .001) in serum somatotropin at 4 h postinjection. Serum glucose was increased (P less than .01) and serum triglycerides, creatinine, and urea N were decreased (P less than .01) by pST. During the summer, apparent heat stress occurred in pST-treated sows, resulting in 14 deaths. Most (10) of the deaths occurred just before, during, or shortly after farrowing. Fewer (P less than .08) deaths occurred when pST-treated sows were fed the diet with added fat. Sows treated with pST consumed less feed (P less than .10) and lost more backfat (P less than .10) during lactation than controls. Increasing the dietary fat did not prevent these changes. Weaning weights of pigs and milk yield of sows (estimated by deuterium oxide dilution) were not affected by pST treatment. In Exp. 2, sows (n = 42) were injected weekly with 0 or 70 mg of pST on d 3, 10, 17, and 24 of lactation. Litters were standardized by d 3 at 8 to 10 pigs, and sows were fed the same control (low fat) diet as in Exp. 1. Sows treated with pST consumed less feed and lost more weight and backfat during lactation than untreated sows. Litter size, average pig weaning weights, and milk yield were not influenced by pST treatment. These data indicate that a 6-mg daily injection of pST from 6 d prepartum to d 24 of lactation or a 70-mg weekly injection of pST from 3 d postpartum to d 24 of lactation does not increase milk production in lactating sows.     

Response to metabolic challenges in early lactation dairy cows during treatment with bovine somatotropin

Milk production is increased in lactating cows treated with bovine somatotropin (bST) because a greater portion of absorbed nutrients are partitioned for milk synthesis. This homeorhetic action may be caused by alterations in response of key tissues to homeostatic signals. To examine this theory, acute metabolic challenges were administered to 8 multiparous Holstein cows (61 +/- 2 days postpartum) receiving daily subcutaneous injections of pituitary-derived bST (26.3 mg) or excipient during two 14-day treatment periods (crossover experimental design). Treatment with bST increased milk yield 12%. Feed intake did not change so that net energy balance decreased (+ .5 vs. -4.3 Mcal/day). Plasma concentrations of nonesterified fatty acids (NEFA) were chronically elevated in bST-treated cows, consistent with energy balance differences. However, baseline concentrations of glucose, insulin, and glucagon in plasma did not differ. On the last 3 days of treatment, individual metabolic challenges were administered via jugular cannulas: epinephrine (700 ng/kg BW), glucose (250 mg/kg BW), insulin (1.0 micrograms/kg BW), and glucagon (175 ng/kg BW). Plasma glucose was reduced after the insulin challenge to a lesser extent during bST treatment. In bST-treated cows, the increase in plasma NEFA in response to epinephrine was greater, and NEFA concentrations were lowered to a greater extent after insulin and glucose challenges. Glucose, insulin, and glucagon removal rates were not altered, nor was plasma glucose response to epinephrine or glucagon challenges. Treatment of lactating cows with bST primarily altered the response of adipose tissue to homeostatic signals which affect lipid metabolism.     

Impact of bovine somatotropin administration beginning at day 70 of lactation on serum metabolites, milk constituents, and production in cows previously exposed to exogenous somatotropin.

Metabolic and production responses are reported for 72 cows treated with bovine somatotropin (BST) for 30 days starting at day 70 of lactation. Of these 72 cows, 48 had been exposed in the preceding lactation to long-term treatment with BST at 3 dosages and 24 (controls) had not been given BST. Approximately half of the cows in each group were parity-2 cows, the rest were older. Comparisons between groups were made separately for parity-2, and older cows. Analyses, using pretreatment values of each variable as a covariate, indicated that older cows, but not parity-2 cows, significantly (P less than 0.05) increased milk production during treatment. Parity-2 cows, however, had a significantly higher milk fat percentage than controls following treatment. Cows treated with 51.6 or 86 mg BST/d in both parity groups had significantly higher serum-free fatty acids than controls. Estimated net energy balances were significantly lower for older treated cows, but did not significantly differ from controls for parity-2 treated cows. Older cows in the 86 mg of BST/d group tended to have higher concentrations of blood glucose than did older control-group cows. Treatment with BST did not significantly increase serum ketone concentrations in any group of animals, and none of the cows developed clinical ketosis during this period. Estimated net energy balance (ENEB) during treatment was a significant (P less than 0.05) covariate for free fatty acid concentrations in older cows and for milk fat percentage in parity-2 cows. Covariate adjusted analyses, using ENEB during treatment as a covariate, indicated that lipolytic stimuli already acting may be enhanced by treatment with BST, but a negative energy balance was not a necessary precondition for free fatty acid concentrations to increase following somatotropin treatment. Similarly, milk fat percentages for parity-2 treated cows were significantly (P less than 0.05) higher during treatment than controls when ENEB during treatment was used as a covariate. Increased milk fat concentrations in parity-2 treated cows were not associated with significant increases in the ratio of C18:C4-10 milk fatty acids, indicating that increased milk fat resulted from either an increase in incorporation of C18 fatty acids into milk fat coupled with an increase in de novo mammary synthesis of C4-10 milk fatty acids or an increase in C12-16 fatty acids that may arise either from increased tissue mobilization, from diet, or from de novo mammary synthesis.     

Bovine respiratory disease: commercial vaccines currently available in Canada

Bovine respiratory disease (BRD) remains a significant cost to both the beef and dairy industries. In the United States, an estimated 640 million dollars is lost annually due to BRD. Losses are largely a result of pneumonic pasteurellosis ("shipping fever"), enzootic pneumonia of calves, and atypical interstitial pneumonia. In Canada, over 80% of the biologics licensed for use in cattle are against agents associated with BRD. The objectives of this paper were (a) to summarize information available concerning commercial vaccines currently used in Canada for protection against BRD, and (b) to provide an easily accessible resource for veterinary practitioners and researchers. Information from the most recent Compendium of Veterinary Products has been tabulated for each vaccine by trade name, according to vaccine type, and the pathogens against which they are designed to protect. Additional information from published articles (peer-reviewed and other) has been provided and referenced.     

Bovine leukemia virus: Duration of BLV colostral antibodies in calves from commercial dairy herds

A study was conducted to determine the duration of colostral antibodies to bovine leukemia virus (BLV) in diary calves from commercial dairy farms. Sera of pregnant dams from four different dairy farms and sera of the calves of these dams were analyzed for BLV antibodies using the agar gel immunodiffusion (AGID) test. Precolostral serum samples were collected from the female calves of known BLV serologically positive dams. Postcolostral serum samples of the same calves were collected on Day 2 and biweekly until 2 consecutively negative AGID tests performed 4 weeks apart were obtained. Subsequently, the biweekly serum samples from each calf were analyzed quantitatively for BLV antibodies with the AGID test. End-point titers were determined using phosphate buffered saline to make two-fold dilutions. A logarithmic transformation of the inverse of the end-point titer was used to determine the regression line of antibody decay for each calf. Estimated weighted regression analysis was used to determine the least-squares regression line for 27 of the 38 calves sampled. The duration of colostral antibodies was calculated as 71 days using the prediction equation. The minium and maximum durations of colostral antibodies were 14 days and 147 days, respectively. The half-life of the antibodies was 36.05 days. Factors affecting the duration of BLV colostral antibodies and the practical applicability of this study were discussed.     

A semi-parametric model for lactation curves: development and application

We propose a semi-parametric model for lactation curves that, along with stage of lactation, accounts for day of the year at milk recording and stage of gestation. Lactation is described as having 3 different phases defined by 2 change points of which the second is a function of gestation stage. Season of milk recording is modelled using cosine and sine functions. As an application, the model is used to estimate the association between intramammary infections (IMI) dynamics as measured by somatic cell count (SCC) over the dry period and the shape of the lactation curve. Milk recording data collected in 2128 herds from England and Wales between 2004 and 2007 were used in the analysis. From a random sample of 1000 of these herds, smoothed milk production was used to test the behaviour of the model and estimate model parameters. The first change point was set at 60 days in milk. The second change point was set at 100 days of gestation or 200 days in milk when the latter was not available. Using data from the 1128 remaining herds, multilevel models were then used to model individual test-day milk production within lactations within herds. Average milk production at 60 days in milk for cows of parities 1, 2, 3 and greater than 3 were 26.9 kg, 31.6 kg, 34.4 kg and 34.7 kg respectively and, after this stage, decreases in milk production per 100 days milk of lactation were 3.1 kg, 5.1 kg, 6.3 kg and 6.7 kg respectively. Compared to cows that had an SCC below 200,000 cells/mL on both the last milk recording in a lactation and the first milk recording in the following lactation, cows that had an SCC greater than 200,000 cells/mL on their first milk recording after calving had an estimated loss of milk production of between 216 and 518 kg depending on parity. These estimates demonstrate the impact of the dynamics of SCC during the dry period on milk production during the following lactation.     

Recombinant porcine somatotropin: an immunotoxicology study.

The present study was designed to determine the effect of recombinant porcine somatotropin (rpST; 5, 15, or 25 mg.pig-1.d-1 for 57 d) on a variety of immune function variables. We observed no significant effect of rpST treatment on the gross pathology of the pigs, histopathology of the immune system organs, total and differential white blood cell counts, lymphocyte blastogenic response to mitogens, or the neutrophil functions of chemotaxis, ingestion, reduction of cytochrome C, iodination, and antibody-dependent cell-mediated cytotoxicity. Those variables that were significantly affected by rpST treatment include a decreased hemoglobin and packed red blood cell volume (at some time points for all three rpST dosages), a decrease in plasma protein level at the 25-mg dose, a small increase in neutrophil random migration (at all three rpST dosages), and a decrease in IgG antibody response to tetanus toxoid at 15 d after immunization (but not at d 8, 22, or 29). Additionally, rpST treatment was associated with a decreased rate of BW gain (at 15-mg dose), increased liver and kidney weights (at all three dosage levels), and an increased incidence of renal tubular cytoplasmic vacuolation of minor severity. There were no observed differences in the overall health of the pigs due to rpST treatment, based on clinical observations as well as determination of antibody titer to, and isolation of, common swine pathogens. Therefore, there was no evidence that the observed influence of rpST treatment on immune function would be clinically relevant.     

离子载体对泌乳奶牛影响的应用研究进展

研究表明应用离子载体(IOP)有助于提高奶牛泌乳量和刺激免疫应答反应。目前IOP对奶牛泌乳影响的一些研究成果已经被广泛应用于奶牛生产中。IOP能抑制瘤胃中的革兰氏阳性菌,改变瘤胃内环境,从而提高饲料中的氮和能量的利用率。资料显示,泌乳奶牛服用IOP后有助于体内能量平衡、提高自身对疾病的抵抗力和增加产奶量。因而,IOP对分娩前后的奶牛,特别是那些泌乳能力强的奶牛的作用更加显著。     

Daily treatment of horses with equine somatotropin from 4 to 16 months of age.

Fourteen foals between 4 and 4.5 mo of age were used to determine the effects of 12 mo of daily treatment with equine somatotropin (eST) on growth, metabolic, and hormonal characteristics. The foals were paired by sex, type, and lineage, and one of each pair was administered eST daily at 20 microg/kg of BW. Body weights, body measurements, and assessments of glucose tolerance and feedback effects on endogenous somatotropin (ST) secretion were made routinely. Treatment with eST did not alter (P > 0.10) BW, height at withers, length of body, widths of chest and rump, heart girth, length of head, front or rear cannon lengths, front or rear cannon circumferences, gaskin circumference, or skin thickness, even though plasma IGF-I concentrations were doubled (P = 0.012). Glucose concentrations were higher (P = 0.03) in treated horses before glucose infusion; there was no difference (P > 0.10) in the glucose response to infusion. The insulin response to glucose infusion in the treated horses was generally higher (P = 0.0069) than in controls. Endogenous ST secretion in response to a ST secretagogue was reduced (P = 0.0001) in foals treated with eST in all months. The prolactin and thyroid-stimulating hormone responses to thyrotropin-releasing hormone on June 1 were not affected (P > 0.10) by treatment. In conclusion, daily treatment of growing horses with eST for 12 mo at the recommended dose altered the hormonal and metabolic characteristics known to be affected by ST but did not alter the growth characteristics of the animals.     

高效液相色谱法在饲料科学中的应用

在各个领域的研究与发展中,实验仪器都发挥了不可估量的作用,现代仪器更加精密(如全自动电泳扫描仪),分析技术更加高效(如色谱-质谱结合),从而进一步地推动了科学的迅猛发展。动物营养与饲料科学的前进同样需要借助于实验仪器。我们制定饲养标准之前,需要利用实