Low Doses of Bovine Somatotropin During the Transition Period and Early Lactation Improves Milk Yield, Efficiency of Production, and Other Physiological Responses of Holstein Cows

[The lipidosis of the liver of dairy cows: Part 1 - Role of insulin and the Growth Hormone-IGF-1 axis]

Lipidosis of the liver of dairy cows is a metabolic disease known since many years and is caused by an uptake of nonesterified fatty acids (NEFA) into the liver cells, limited metabolism of NEFA (oxidation and production of β-hydroxybutyrate), and resynthesis in relation to a low efflux as triglyceride (TG). The pathogenesis of lipidosis includes a) an augmented release of NEFA by mobilisation of adipose tissue, b) uptake of NEFA into the liver cells, c) metabolism of NEFA and d) re-synthesis of triglyceride and e) an efflux of TG as very low density lipoprotein (VLDL). The steps a-e are postpartum modified by hormones as an increase of growth hormone, a pronounced insulin resistance in combination with a decreased insulin and of IGF-1 concentrations. These hormonal changes are related to an uncoupling of the growth hormone-IGF-1-axis with enhanced lipolysis and consequences mentioned above. These alterations are associated with inflammation, oxidative and endoplasmatic stress. The metabolic and hormonal alterations are the result of the selection of dairy cows primarily for milk production without adequate food intake with the consequence of lipidosis, ketosis and further health risks (production diseases).

Symposium review: Integrating the control of energy intake and partitioning into ration formulation

Energy intake and partitioning are determined by many interacting factors and their prediction is the Achilles' heel of ration formulation. Inadequate energy intake can limit milk yield and reproductive performance, whereas excessive energy intake will increase body condition, increasing the risk of health and reproductive issues in the subsequent lactation. Ration composition interacts with the physiological state of cows, making it difficult to predict DMI and the partitioning of energy accurately. However, understanding the factors controlling these allows us to devise grouping strategies and manipulate rations to optimize energy intake through lactation. Eating is controlled by the integration of signals in brain feeding centers. Ration composition affects DMI of cows via signals from ruminal distention and the hepatic oxidation of fuels. Dairy cow rations must contain a minimal concentration of relatively low-energy roughages for proper rumen function, but signals from ruminal distension can limit DMI when the drive to eat is high. Signals from the hepatic oxidation of fuels likely dominate the control of DMI in the peripartum period when cows are in a lipolytic state and later in lactation when signals from distension diminish. Therefore, the effects of the ration on DMI vary with the physiological state of the animal. Furthermore, they interact with environmental stressors such as social (e.g., overcrowding) and thermal stress. The objective of this article is to discuss the effects of ration composition on energy intake and partitioning in lactating cows and how they can be manipulated to optimize productive performance.

Maladaptation to the transition period and consequences on fertility of dairy cows

After parturition, dairy cows undergo a plethora of metabolic, inflammatory, and immunologic changes to adapt to the onset of lactation. These changes are mainly due to the homeorhetic shift to support milk production when nutrient demand exceeds dietary intake, resulting in a state of negative energy balance. Negative energy balance in postpartum dairy cows is characterized by upregulated adipose tissue modelling, insulin resistance, and systemic inflammation. However, half of the postpartum cows fail to adapt to these changes and develop one or more types of clinical and subclinical disease within 5 weeks after calving, and this is escorted by impaired reproductive performance in the same lactation. Maladaptation to the transition period exerts molecular and structural changes in the follicular and reproductive tract fluids, the microenvironment in which oocyte maturation, fertilization, and embryo development occur. Although the negative effects of transition diseases on fertility are well-known, the involved pathways are only partially understood. This review reconstructs the mechanism of maladaptation to lactation in the transition period, explores their key (patho)physiological effects on reproductive organs, and briefly describes potential carryover effects on fertility in the same lactation.

Effect of bovine somatotropin injection in late pregnant Holstein heifers on metabolic parameters and steroidogenic potential of the first postpartum dominant follicle

The aim of this study was to determine the effect of pre-partum injections of bovine somatotropin (bST) in dairy heifers on metabolic markers and the steroidogenic potential of the first postpartum dominant follicle. Heifers were assigned to two groups: bST (ST; n = 29), that received two doses of bST (500 mg/dose) at -28 and -14 days relative to calving; and control (CTL; n = 30), that did not received bST. Follicular development was monitored via ultrasound every 3 days starting at 8 days in milk (DIM) in a subset of 20 heifers until the day the first large follicle reached a diameter of 16 mm. From these cows follicular fluid was aspirated and the follicular cells recovered (ST; n = 8 and CTL; n = 10). Blood samples were collected weekly for all heifers. Follicular fluid IGF-I concentrations of the first postpartum dominant follicle was higher (P = 0.05) in ST (87.1 ± 7.7 mg/mL) than CTL cows (64.3 ± 6.8 mg/mL). Also, E2 concentration in the follicular fluid was higher (P = 0.02) for ST (199.7 ± 55.9 ng/mL) than CTL cows (74.5 ± 37.7 ng/mL). The expression of LHCGR and STAR mRNA in follicular cells was higher (P < 0.05) in ST than CTL cows. Nonetheless, HSD3B, P450scc, P450c17, IGFr and CYP19A1 mRNA expression was not different between groups (P > 0.05). Serum IGF-I concentration was higher in ST treated heifers during the pre-partum period (P = 0.01) and no difference was observed in the postpartum period (P = 0.19). In conclusion, pre-partum bST treatment in dairy heifers increased intrafollicular IGF-I and expression of LHCGR and STAR mRNA in follicular cells of the first postpartum dominant follicle. These changes were associated to increased intrafollicular and serum E2 concentration, which can potentially increase the chance of ovulation of the first follicular wave.

Mammary transcriptome analysis of lactating dairy cows following administration of bovine growth hormone

The galactopoietic effect of growth hormone (GH) in lactating ruminants is well established; however the mechanisms that mediate these effects are not well understood. The first objective of this study was to determine the effect of GH on the synthesis of the major casein and whey proteins. The second objective was to identify the genes and pathways that may be involved in mediating the effect of GH on milk synthesis. A single subcutaneous injection of a commercially available slow release formulation of GH (Lactatropin®), or physiological saline solution (control) was administered to non-pregnant dairy cows (n=4/group) in mid-late lactation. Milk samples were collected for composition analysis and mammary lobulo-alveolar tissue was collected postmortem 6 days post injection. Gene expression profiles were evaluated using either a 22 000 bovine complementary DNA microarray or quantitative PCR (qPCR), and microarrays were validated by qPCR. The yield of all the major casein and whey proteins was increased 32% to 41% in GH-treated cows, with the exception of α-lactalbumin yield which was elevated by 70% relative to controls. Treatment with GH treatment tended to increase the concentration of α-lactalbumin but had no effect on the concentration of any of the major milk proteins. Messenger RNA (mRNA) abundance of the major whey and casein genes, with the exception of α-s2-casein, was increased in response to GH compared with controls, which is consistent with the positive effect of GH on milk production. Treatment with GH treatment influenced the mRNA abundance of genes involved in cell growth and proliferation, transcriptional and translational regulation, actin cytoskeleton signalling, lipid metabolism and cell death. This study has provided new insights into the cell signalling that may be involved in mediating the effect of GH on milk production in the mammary gland of lactating dairy cows.

Effect of administration of recombinant bovine somatotropin on health and performance of lactating dairy cows diagnosed with hyperketonemia

The effect of administering recombinant bovine somatotropin (rbST) to cows with hyperketonemia during the early postpartum period on health, metabolic parameters, milk production, and early reproductive performance was evaluated in a double-blinded clinical trial. Cows from 8 dairy herds in New York State were tested weekly between 3 and 16d in milk for elevated serum β-hydroxybutyrate. Cows were enrolled in the study when blood β-hydroxybutyrate was ≥1.3mmol/L for the first time. Enrolled cows were randomly assigned to a treatment (n=273) or placebo control (n=270) group. Treated cows were given 325mg of rbST subcutaneously on the day of enrollment and again 14d later. Control cows received the same regimen except the syringe contained only the carrier without somatotropin. After enrollment, blood samples were collected weekly for 4wk and submitted to the laboratory to be analyzed for selected metabolites. Risk ratios for clinical diseases subsequent to treatment were calculated using Poisson regression. Continuous data were analyzed using linear mixed models. Time to first insemination was assessed with survival analysis. In the 42d following the first administration of rbST, incidence risks of displaced abomasum, clinical ketosis, metritis, clinical mastitis, and lameness were not different between treatment groups. Cows treated with rbST had a slightly lower body condition score 28d after enrollment compared with control cows. In the 4wk following enrollment, serum nonesterified fatty acids and aspartate amino-transferase were slightly higher for treated than control cows, respectively. Serum glucose, calcium, haptoglobin, and β-hydroxybutyrate were similar between groups. Treatment had no effect on resolution of hyperketonemia in any of the 4wk after enrollment. Milk production in either of the 2-wk periods after each treatment was not different between treated and control cows. Furthermore, milk production was not different between groups from enrollment to 98d in milk (42.6±0.6 and 42.1±0.7kg/d for treatment and control groups, respectively). Treatment had no effect on time to first insemination (83 and 74d in milk for treatment and control groups, respectively; hazard ratio=0.72) or first insemination pregnancy risk (27 and 29% for treatment and control groups, respectively; risk ratio=0.92). Based on the current results, it is not recommended to use a low dose of rbST as therapy for cows with hyperketonemia.

Effects of recombinant bovine somatotropin during the periparturient period on innate and adaptive immune responses, systemic inflammation, and metabolism of dairy cows

The aim of this experiment was to determine effects of treating peripartum dairy cows with body condition score ≥3.75 with recombinant bovine somatotropin (rbST) on immune, inflammatory, and metabolic responses. Holstein cows (253±1d of gestation) were assigned randomly to 1 of 3 treatments: untreated control (n=53), rbST87.5 (n=56; 87.5mg of rbST), and rbST125 (n=57; 125mg of rbST). Cows in the rbST87.5 and rbST125 treatments received rbST weekly from -21 to 28d relative to calving. Growth hormone, insulin-like growth factor 1, haptoglobin, tumor necrosis factor α, nonesterified fatty acids, β-hydroxybutyrate, glucose, and cortisol concentrations were determined weekly from -21 to 21d relative to calving. Blood sampled weekly from -14 to 21d relative to calving was used for hemogram and polymorphonuclear leukocyte (PMNL) expression of adhesion molecules, phagocytosis, and oxidative burst. Cows were vaccinated with ovalbumin at -21, -7, and 7d relative to calving, and blood was collected weekly from -21 to 21d relative to calving to determine IgG anti-ovalbumin concentrations. A subsample of cows had liver biopsied -21, -7, and 7d relative to calving to determine total lipids, triglycerides, and glycogen content. Growth hormone concentrations prepartum (control=11.0±1.2, rbST87.5=14.1±1.2, rbST125=15.1±1.3ng/mL) and postpartum (control=14.4±1.1, rbST87.5=17.8±1.2, rbST125=21.8±1.1ng/mL) were highest for rbST125 cows. Cows treated with rbST had higher insulin-like growth factor 1 concentrations than control cows (control=110.5±4.5, rbST87.5=126.2±4.5, rbST125=127.2±4.5ng/mL) only prepartum. Intensity of L-selectin expression was higher for rbST125 than for control and rbST87.5 cows [control=3,590±270, rbST87.5=3,279±271, rbST125=4,371±279 geometric mean fluorescence intensity (GMFI)] in the prepartum period. The PMNL intensities of phagocytosis (control=3,131±130, rbST87.5=3,391±133, rbST125=3,673±137 GMFI) and oxidative burst (control=9,588±746, rbST87.5=11,238±761, rbST125=12,724±781 GMFI) were higher for rbST125 cows than for control cows during the prepartum period. Concentrations of serum IgG anti-ovalbumin tended to be higher for rbST125 cows than for control cows (control=0.75±0.11, rbST87.5=0.94±0.10, rbST125=1.11±0.11 optical density) in the prepartum period. Haptoglobin concentration was significantly reduced 7d postpartum for rbST125 treatment compared with control and rbST87.5 treatments (control=2.74±0.28, rbST87.5=2.81±0.28, rbST125=1.87±0.28 optical density). Although treatment tended to affect postpartum β-hydroxybutyrate (control=747.5±40.2, rbST87.5=753.2±40.1, rbST125=648.8±39.7 µmol/L), it did not affect liver contents of total lipids, triglycerides, or glycogen. Incidence of metritis among rbST125 cows was reduced compared with that in control cows (control=23.1, rbST87.5=18.0, rbST125=7.8%). Treatment of dairy cows with 125mg of rbST improved innate immune responses and IgG concentration, with limited effects on metabolism.

Prepartum administration of recombinant bovine somatotropin (rBST) on adaptation to subclinical ketosis of the ewes and performance of the lambs

The aim of this study was to determine the effect of prepartum rbST injection on the metabolic profile of pregnant ewes induced to subclinical ketosis, as well as the metabolism until seven days of life and weight gain until seven weeks of life of the lambs. Twenty seven pregnant ewes of the pantaneiro genetic group were used, divided into two groups: rbST group (n = 14) and control group (n = 13). The rbST group received two applications of 1 mg/kg of rbST, at 97 and 111 days gestation, while the control group received placebo injections. There were significant differences between groups in levels of GGT in the ketosis post induction period and BHB concentrations in the postpartum period. Concentrations of glucose, urea, phosphorus, albumin, cholesterol, AST, NEFA and insulin were not different between dams from the two groups in different periods of the study (P>0.05). There was an effect of rbST on body weight observed already at fourteen days of life (P<0.0001), there was an increase in serum phosphorus levels at birth of lambs (P=0.0014), and albumin at seven days of life (P = 0.0014) of the lambs, with no difference between groups for the other metabolites. Therefore, the use of rbST was effective in increasing the weight of the lambs until the seventh week of life. In addition, rbST treatment had positive effects on the dam metabolism with reduction of liver overload, as indicated by decreased GGT after ketosis induction and decreased BHB at the postpartum period.

Invited review: Sustainability of the US dairy industry

The US dairy industry has realized tremendous improvements in efficiencies and milk production since the 1940s. During this time, farm and total cow numbers have decreased and average herd size has increased. This intensification, combined with the shift to a largely urban public, has resulted in increased scrutiny of the dairy industry by social and environmental movements and increased concern regarding the dairy industry's sustainability. In response to these concerns, a group of scientists specializing in animal welfare, nutrient management, greenhouse gas emissions, animal science, agronomy, agricultural engineering, microbiology, and economics undertook a critical review of the US dairy industry. Although the US dairy system was identified as having significant strengths, the consensus was that the current structure of the industry lacks the resilience to adapt to changing social and environmental landscapes. We identified several factors affecting the sustainability of the US dairy industry, including climate change, rapid scientific and technological innovation, globalization, integration of societal values, and multidisciplinary research initiatives. Specific challenges include the westward migration of milk production in the United States (which is at odds with projected reductions in precipitation and associated limitations in water availability for cattle and crops), and the growing divide between industry practices and public perceptions, resulting in less public trust. Addressing these issues will require improved alignment between industry practices and societal values, based upon leadership from within the industry and sustained engagement with other interested participants, including researchers, consumers, and the general public.

Effect of prepartum somatotropin injection in late pregnant Holstein heifers with high body condition score on metabolic parameters, resumption of ovulation and milk production

Acosta, D. A. V., Pfeifer, L. F. M., Schmitt, E., Schneider, A., Silveira, P. A. S., Jacometo, C. B., Brauner, C. C., Rabassa, V. R., Corrêa, M. N. and Del Pino, F. A. B. 2013. Effect of prepartum somatotropin injection in late pregnant Holstein heifers with high body condition score on metabolic parameters, resumption of ovulation and milk production. Can. J. Anim. Sci. 93: 287–292. In the early post-partum period of dairy cows the duration and intensity of negative energy balance, the level of body condition score (BCS) loss and the milk yield are strongly associated with the timing of the first ovulation. The aim of this study was to determine the effect of pre-partum injections of somatotropin in dairy heifers with high BCS on the metabolism, resumption of ovarian activity and milk production. Holstein heifers (n=20) with high BCS, were divided randomly into two groups: somatotropin (n=10), which received two doses of somatotropin (500 mg) at −28 and −14 d from calving and Control (n=10), which received placebo. Blood samples were collected for evaluation of β-hydroxybutyrate (BHBA) and non-esterified fatty acids (NEFA) concentrations. Follicular development was also monitored via ultrasound. Somatotropin had no effect on plasma NEFA (P=0.35 and P=0.46) or BHBA (P=0.20 and P=0.44,) concentrations in the pre-partum and post-partum period, respectively. Milk production was not different between control (17.53±0.66 kg cow−1 d−1) and somatotropin groups (16.13±0.67 kg cow−1 d−1) (P=0.14). Pre-partum somatotropin administration did not affect (P=0.28) the time of the first post-partum ovulation. The proportion of cows ovulating the first post-partum follicular wave was not different between groups (P=0.49). In conclusion, pre-partum somatotropin treatment in dairy heifers with high body condition score seems not to have any effect on markers of energy balance, milk production or development of the first follicular wave in the early post-partum period.

Hypophagic effects of propionic acid are not attenuated during a 3-day infusion in the early postpartum period in Holstein cows

We previously showed that propionic acid was more hypophagic than acetic acid when infused intraruminally in cows in the postpartum period and that the degree of hypophagia from short-term propionic acid infusion (18 h) was related to the acetyl coenzyme A (CoA) concentration in the liver. The objective of this experiment was to evaluate adaptation over time with longer-term infusions over 3 d. Twelve multiparous cows (2-13 d postpartum) were blocked by calving date and assigned randomly to treatment sequence in a crossover design experiment. The experiment was 12 d long with covariate periods preceding each 3-d infusion period. Treatments were 1.0 M propionic acid or 1.0 M acetic acid, infused intraruminally at 0.5 mol of volatile fatty acids/h beginning 6 h before feeding and continuing for 78 h with 3 d between infusions. Propionic acid decreased dry matter intake (DMI) relative to acetic acid (15.9 vs. 17.0 kg/d). However, a period-by- treatment interaction was detected for DMI. During period 1, propionic acid decreased DMI relative to acetic acid (14.3 vs. 17.5 kg/d) because of a reduction in meal size (1.30 vs. 1.65 kg), with no effect on intermeal interval. Propionic acid decreased DMI over the first 4 h following feeding (5.86 vs. 8.23 kg) but did not affect DMI 4 to 24 h after feeding. The depression in DMI in period 1 was positively related to hepatic acetyl-CoA concentration during the covariate period. Propionic acid was increasingly more hypophagic than acetic acid as hepatic acetyl-CoA concentration was elevated. No treatment-by-day interaction for DMI was observed, suggesting little or no measurable adaptation to treatment over the 3-d infusion period. These results suggest that hypophagia from propionic acid is enhanced when hepatic acetyl-CoA concentrations are elevated, such as when cows are in a lipolytic state.

Increased cleavage and blastocyst rate in ewes treated with bovine somatotropin 5 days before the end of progestin-based estrous synchronization

Treatment with bovine somatotropin (bST) during estrous synchronization increased fertility and prolificacy in sheep. In the present study, a single dose of bST 5 days before the end of progestin treatment improved cleavage and embryo development. Stage of estrous cycle was synchronized in ewes (n=32) with progestin and superovulation was induced by use of FSH. Five days before the end of progestin treatment, ewes were randomly assigned to two groups: bST group (n=16) received a depot injection of 125 mg of bST sc (Lactotropina, Elanco, México) and the control group (n=16) received saline solution. Estrous was detected with rams fitted with an apron every 2 h and estrous sheep were mated every 8 h whilst in estrous. Embryos were recovered on Day 7 post mating, assessed microscopically and fixed in 4% paraformaldehyde. Cell number in blastocysts was counted after Hoechst 33342 staining. Plasma concentrations of IGF-I, insulin and progesterone were determined in eight sheep per group from the day of bST treatment to the day of embryo recovery. Cleavage rate, percentage of transferable embryos (transferable embryos/cleaved) and percentage of embryos reaching the blastocyst stage (blastocyst/cleaved) were compared between groups by logistic regression. IGF-I, insulin and progesterone plasma concentrations were analyzed by ANOVA for repeated measurements and cell number by ANOVA. Cleavage rate was greater (P<0.01) in bST treatment group (86%) than in the control group (62%). Similarly, the proportion of embryos reaching the blastocyst stage (bST=68.7 vs control=42.5) and the number of cells per blastocyst (bST group 91.8±5.5 compared to control group 75±6) were greater (P<0.01) in the bST-treated sheep. Plasma concentrations of IGF-I and insulin were greater (P<0.01) in the bST-treated group. No changes were observed in progesterone concentrations (P=0.5). It is concluded that bST injection 5 days before progestin removal increases cleavage rate and the proportion of embryos that reach the blastocyst stage. These effects are associated with an increase in IGF-I and insulin concentrations.

Drug delivery systems in domestic animal species

Delivery of biologically active agents to animals is often perceived to be the poor relation of human drug delivery. Yet this field has a long and successful history of species-specific device and formulation development, ranging from simple approaches and devices used in production animals to more sophisticated formulations and approaches for a wide range of species. While several technologies using biodegradable polymers have been successfully marketed in a range of veterinary and human products, the transfer of delivery technologies has not been similarly applied across species. This may be due to a combination of specific technical requirements for use of devices in different species, inter-species pharmacokinetic, pharmacodynamic and physiological differences, and distinct market drivers for drug classes used in companion and food-producing animals. This chapter reviews selected commercialised and research-based parenteral and non-parenteral veterinary drug delivery technologies in selected domestic species. Emphasis is also placed on the impact of endogenous drug transporters on drug distribution characteristics in different species. In vitro models used to investigate carrier-dependent transport are reviewed. Species-specific expression of transporters in several tissues can account for inter-animal or inter-species pharmacokinetic variability, lack of predictability of drug efficacy, and potential drug-drug interactions.

Effects of plasmid growth hormone-releasing hormone treatment during heat stress

A gene therapy treatment with plasmid-based growth hormone-releasing hormone (GHRH) delivered by electroporation (EP) was investigated during heat stress; 32 primiparous cows received 2.5 mg of a GHRH-expressing myogenic plasmid (pSP-HV-GHRH), while 20 were designated as controls. Offspring of treated animals showed a reduction in mortality (47%; p < 0.02), and survival from birth to 260 days was dramatically improved (0% mortality vs. 21% in controls) along with an increase in weight gain (p < 0.05). Milk production was increased compared to controls with an average yield gain of 421 kg/cow (p = 0.028). Prolactin (PRL) levels were also significantly increased compared to controls (p < 0.05). The second pregnancy rate was improved by GHRH treatment (53.3% vs. 30.8%). This study shows that the use of plasmid-mediated therapy delivered by EP can maintain health status during periods of heat stress, important for both animals and potentially humans in hot, challenging climates.

The role of endocrine insulin-like growth factor-I (IGF-I) in female bovine reproduction

Insulin-like growth factor-I (IGF-I) plays a pivotal role in cattle fertility, acting as a monitoring signal that allows reproductive events to occur when nutritional conditions for successful reproduction are reached. However, endocrine IGF-I is not a predictor of reproductive events, but rather an indirect estimator of the suitability of the animal to achieve the reproductive event in question. Although measuring circulating IGF-I concentrations might not have any clinical application in the cattle industry, endocrine IGF-I screening will continue to be important for the study of interactions between nutrition and reproduction. In addition, endocrine IGF-I screening could be used as an ancillary test for the selection of cattle for high reproductive potential, especially in herds of high genetic merit for milk production, in which a decline in fertility has been identified.

Supplementing Holstein cows with low doses of bovine somatotropin prepartum and postpartum reduces calving-related diseases

The objective of this study was to evaluate whether supplementing Holstein cows with bovine somatotropin (bST; 142.8 mg/14 d), beginning at 21 d (+/-3 d) before expected calving and continuing through 42 d in milk (+/-3 d), affected the incidence rates of retained fetal membranes (RFM), metritis (MET), clinical mastitis (MAS), digestive problems (DIG), ketosis (KET), milk fever (MF), displaced abomasum (DA, left or right), lameness (LAM), or number of sick cows during the first 60 d in milk. Data for multiparous Holstein cows from 3 separate trials were merged for analyses (n = 437). Cows in the bST-supplemented group (n = 162) received biweekly subcutaneous injections of Posilac, whereas control cows (n = 166) and a group of cohorts (n = 109) were not supplemented. Incidences of disease were collected from the herd health records. Across all treatment groups, the incidence rates (number of diseased cows divided by the total number of cows) for RFM, MET, MAS, DIG, KET, MF, DA, and LAM were 8.47, 18.31, 16.02, 4.35, 4.35, 3.66, 3.20, and 3.66%, respectively. The incidence rates of RFM, MET, MAS, DIG, KET, MF, DA, and LAM for cows in the bST-supplemented, control, and cohort groups were 6.79, 7.83, and 11.93%; 16.05, 7.47, and 22.94%; 10.49, 18.07, and 21.10%; 1.23, 5.42, and 7.34%; 1.23, 6.02, and 6.42%; 2.47, 4.22, and 4.59%; 2.47, 3.61, and 3.67%; and 3.70, 3.61, and 3.67%, respectively. The percentages of sick cows (number of cows having one or more cases of disease divided by the total number of cows) in the bST-supplemented, control, and cohort groups were 33.95, 43.37, and 49.54%, respectively. Significant chi-squared values were detected between the bST-supplemented and control groups for MAS, DIG, and KET, with a greater number of healthy cows in the bST-supplemented group. No differences in incidences of diseases or sick cows were detected between the control and cohort groups. Results indicated that a low dose of bST supplemented to Holstein cows for 3 wk prepartum through 60 d in milk reduced the incidences of some calving-related diseases compared with nonsupplemented controls or cohorts. Importantly, no negative effects of bST supplementation on postpartum calving diseases were detected compared with nonsupplemented cows.

Milk Production from Holstein Half Udders After Concurrent Thirty- and Seventy-Day Dry Periods,

The objective of this study was to use a within-cow, half-udder model to compare the effect of cessation of milk removal from mammary quarters within respective half udders at either 30 or 70 d before expected calving date (ECD) on the ability of the half udders to subsequently produce milk. Pregnant Holstein cows were assigned to control (n = 14) or treatment (TRT, n = 26) groups. All mammary quarters in the udder of cows in the control group had 70-d (68 +/- 9 d) dry periods, whereas in each cow of the TRT group, 1 randomly selected half udder was dried at 70 d before ECD and the other half udder continued to be milked twice daily until dried at 30 d before ECD. From 80 through 70 d before ECD, amounts of milk produced by the left and right half udders of cows in the TRT group were measured at the first-shift milking. No differences were detected in the actual or relative amounts of milk produced by the left (3.46 +/- 0.2 kg; 48.8 +/- 1.0%) and the right (3.63 +/- 0.2 kg; 51.2 +/- 1.0%) half udders. Furthermore, the actual and relative amounts of milk produced by the half udders (n = 12 left, 14 right) subsequently dry for 67 +/- 7 d (3.56 +/- 0.2 kg; 50.2 +/- 1.0%) and the half udders (n = 14 left, 12 right) subsequently dry for 27 +/- 7 d (3.54 +/- 0.2 kg; 49.8 +/- 1.0%) did not differ before they were dried. However, from 3 to 100 d of the subsequent lactation, the 30-d dry half udders produced 18.9% less milk than the 70-d dry half udders (16.3 vs. 20.1 +/- 1.0 kg/d). In addition, relative amounts of total-udder milk produced by the 30- and 70-d dry half udders in the same cow differed (44.9 vs. 55.1 +/- 0.2%, respectively). Cows in the control group produced more milk than cows in the TRT group through 80 DIM (39.5 vs. 35.2 +/- 0.6 kg/d), but not from 3 through 150 DIM (39.0 vs. 36.2 +/- 1.6 kg/d). Thus, half udders that produced the same actual and relative amounts of milk before being dried did not do so when given a 30-d dry period instead of a 70-d dry period. When compared with the pre-dry value (49.8%), the relative contribution of half udders dry for 30 d to the total milk yield during the first 100 DIM was decreased by 9.8%.

Effect of modified dry period lengths and bovine somatotropin on yield and composition of milk from dairy cows

Dry periods of 40 to 60 d have been an industry standard because dry periods <40 d have resulted in reduced milk yields in the subsequent lactation by 10 to 30%. However, recent research has demonstrated no production losses for cows given a 30-d dry period. The current study evaluated milk production effects of shortened or omitted dry periods for cows at mature-equivalent production >12,000 kg of milk and treated with bovine somatotropin (bST). The study used 2 commercial dairies and one university dairy and included 4 treatments. Five multiparous and 5 primiparous cows from each farm were assigned to each treatment: 1) 60-d dry period, label use of bST (60DD); 2) 30-d dry period, label use of bST (30DD); 3) continuous milking, label use of bST (CMLST); and 4) continuous milking with continuous use of bST (CMCST). Per label, bST use started at 57 to 70 d in milk and ended 14 d before drying (60DD and 30DD) or expected calving date (CMLST). In primiparous cows, average milk yields during the first 17 wk of lactation were reduced for cows on treatments 30DD, CMLST, and CMCST vs. the 60DD treatment. (38.3, 35.1, and 37.5 vs. 44.1 +/- 1.3 kg/d, respectively). For multiparous cows, respective milk yields did not differ (46.6, 43.4, 46.5, and 47.7 +/- 2.1 kg/d). Shortened or omitted dry periods may impede mammary growth in primiparous cows, resulting in reduced milk yield in the subsequent lactation. In contrast, a shortened or omitted dry period with either bST protocol did not alter production in multiparous cows treated with bST. Quality aspects of prepartum milk and colostrum require additional characterization. For multiparous cows, milk income generated for short dry periods or for continuous milking might increase their profitability. At 17 wk of the subsequent lactation, estimates of the cumulative net margins of multiparous cows on the 30DD treatment and continuous milking treatments exceeded those of cows on the 60DD treatment by 40 dollars to 60 dollars per cow.