Effect of dietary energy and previous bovine somatotropin on milk yield, mastitis, and reproduction in dairy cows.

Thirty multiparous lactating Holstein cows were blocked according to time of calving and assigned to a 2 x 3 factorial arrangement of treatments in a randomized complete block design to evaluate the effects of two dietary energy concentrations either without or with bST (20.6 mg/d per cow) administered to cows that had not or had received bST during the preceding lactation. Subcutaneous injection of bST began 28 to 35 d postpartum and continued for 39 wk. The dietary energy concentration x bST interaction was not significant for any response variable. Compared with DMI of control cows, DMI was higher for cows receiving bST, being 1.6 and 2.4 kg/d higher for cows receiving bST for one and two lactations, respectively. Milk, fat, and protein yields were higher for cows receiving bST than for controls. Those receiving bST for a second lactation also produced more milk than controls until wk 20; thereafter, milk yields were similar to those of controls. Somatotropin administration had no adverse effect on udder health. Cows receiving bST tended to ovulate less regularly than controls, which may be attributed to their higher milk yield. However, BW gains during lactation were similar for all treatments, indicating that bST-treated cows built energy reserves for the subsequent lactation. Although energy concentrations of the diets had no significant impact on yield, the higher energy diet tended to depress milk fat concentration. Administration of bST to dairy cows for a second, consecutive lactation yielded responses similar for the first 20 wk of the study to those receiving bST for the first time. However, after wk 20, milk yield was less than that by cows receiving bST for the first lactation but similar to that of control cows.     

Response to recombinant bovine somatotropin in dairy cows with different genetic merit for milk production

Thirty-nine multiparous cows obtained from two genetic lines were utilized to determine the effect of genetic merit on lactation response to long-term administration of recombinant bST. Cow index ranged from -70 to 456 (mean = 183) and -494 to -88 (mean = -288) kg milk for high and low genetic groups, respectively. Cows were blocked by calving date and randomly assigned to treatment within genetic group. Treatments were 0, 10.3, 20.6, and 30.9 mg somatotropin injected daily from wk 14 through 44 postpartum. Cows were fed one of two total mixed rations. Diet 1 (NE1 = 1.65 Mcal/kg, CP = 18%, and ADF = 22%) was fed from start of lactation to at least 4 wk after initiation of treatment. Cows were switched to diet 2 (NE1 = 1.56 Mcal/kg, CP = 16%, and ADF = 27%) when milk output fell below 25 kg/d. Forty-four week lactation yields were 9800 and 9447 kg milk; 364 and 354 kg fat; and 322 and 309 kg protein for high and low genetic groups, respectively. Milk, milk fat, or protein yield due to somatotropin did not differ between genetic groups. Increasing dosage of bST increased milk, 4% FCM, fat, and protein yields in a linear fashion. Percentages of fat and protein of milk were similar for all treatment groups. Body weight changes were not significantly different among treatments, but condition score changes decreased linearly with increasing dose of bST. Long-term treatment with recombinant bST had no apparent effect on incidence of health problems or reproduction.     

Induced lactation in nonpregnant cows: profitability and response to bovine somatotropin

Significant culling of high-producing cows with low fertility reduces profitability of dairy farms as those cows are replaced with heifers. Induced lactation of nonpregnant cows may be a management alternative to reduce culling and increase profits. The objectives of this study were to evaluate the efficacy of bovine somatotropin (bST) to increase milk production in cows induced into lactation with estrogen plus progesterone, and to determine the profitability of inducing cows into lactation vs. using replacement heifers entering the herd as first-lactation cows. Parity 1 or greater, nonpregnant, healthy Holstein cows (n = 28) were induced into lactation by administration of estradiol-17beta (0.075 mg/kg of body weight [BW] per d) and progesterone (0.25 mg/kg of BW per d) for 7 d. Milking began on d 18. Cows were randomly assigned to control or bST treatment groups on d 37 +/- 20 of milking, and milk production was compared for 70 d. After the 70-d comparison, all cows received bST for the duration of lactation. Cows receiving bST produced more milk (28.4 kg/d) than controls (24.1 kg/d), with variable yields among cows. For the economic analysis, induced cows were compared to first-lactation cows in the same herd using fair market value for costs and multiple component pricing for milk. Net present value for an induced cow (1966 dollars) was significantly greater than that for a first-lactation cow (1446 dollars). Our data suggest that bST use in induced cows is profitable. If a reliable method were developed and approved by the FDA, inducing nonpregnant cows into lactation could be used by dairy producers to increase profitability.     

Responses by lactating cows in commercial dairy herds to recombinant bovine somatotropin

Cows (890) in 15 US herds were assigned randomly in equal numbers to control or bST injections (500 mg in a prolonged-release form every 14 d for 12 wk) within three stages of lactation (57 to 100, 101 to 140, and 141 to 189 d postpartum) and two parity groups (primiparous and multiparous). Yield and milk composition were monitored 1 d/wk for 16 wk including 2 wk pretreatment and 2 wk posttreatment. Increases in milk and FCM due to bST injections were less at 57 to 100 d than at 101 to 189 d postpartum (milk 3.6 vs. 5.5; FCM 3.9 vs. 6.1 kg/d per cow), and increases in milk and FCM were more for multiparous than for primiparous cows (milk 5.5 vs. 4.2; FCM 6.0 vs. 4.7 kg/d cow). Temporarily, concentration of milk fat increased and protein decreased; later, concentrations for control and injected cows were similar. Postinjection milk fat concentration decreased, but milk protein concentration increased temporarily. The net increase in milk (and FCM) varied significantly among herds from 2.9 to 7.6 kg/d per cow (mean, 4.9 kg). Responses in FCM were similar over a wide range of pretreatment yields. A great variety of feed ingredients were fed as total mixed rations, and nutrient concentrations varied greatly. The SCC were similar before, during, and after treatment, but increase in FCM of injected cows exhibited a negative correlation with pretreatment SCC. Changes in body condition score of sometribove-injected cows varied among herds (.25 to -.45) and averaged -.02 compared with .07 for controls. There was no pattern in incidence of mastitis during sometribove injections.     

Postparturient metabolic and production responses in cows previously exposed to long-term treatment with somatotropin.

Postparturient metabolic and production responses were studied for 85 multiparous cows consisting of controls and animals that had been previously exposed to long-term treatment with bST. Older cows previously exposed to bST at high doses (51.6 mg/d) had lower milk yields than controls. However, there were no significant differences compared with controls in milk yield for lower dose (17.2 mg/d) older cows or parity 2 cow groups. The bST-treated groups had higher postpartum DMI, lower serum FFA, lower serum beta-hydroxybutyrate levels, and higher serum glucose than controls. Some bST-exposed groups had lower milk fat but higher milk protein levels. All bST-treated groups had significantly lower ratios of C18 to C4 to 10 milk fatty acids. Control cows of both parity groups were in higher body condition and weighed more than bST-treated cows prior to calving. The differences in postpartum metabolism may be attributed to differences in body composition resulting from bST treatment in the prior lactation, because use of body condition score prior to calving as a covariate did not substantially alter responses. The control cows probably had greater reserves of mobilizable lipid. These contentions are supported by changes in milk composition for bST-treated cows, which were consistent with animals of greater appetite, mobilizing less lipid. The bST-treated cows were probably more energetically efficient milk producers because they produced milk from feed rather than from mobilization of tissue stores. These data suggest that bST use in a prior lactation may have potential benefit in reducing risk of metabolic disorders associated with lipid mobilization in the postparturient period.     

Metabolic and production responses to dietary protein and exogenous somatotropin in late gestation dairy cows.

Forty-three multiparous Holstein cows were used in a completely randomized design to evaluate the effects of protein supplementation and the use of bovine somatotropin (bST; Posilac, Monsanto Co., St. Louis, MO) in late gestation on animal metabolism and productivity in the periparturient period. Treatments were initiated 28 d prior to expected calving date and continued through parturition. Diets contained either 13.3 or 17.8% crude protein and were formulated to be similar in profile of protein fractions. Within each dietary treatment, cows were assigned to receive either 0 or 500 mg of sustained released bST once every 14 d until parturition. Following parturition, all cows were subjected to the same management and dietary treatments, and production measurements were followed until 42 d in milk. The use of bST increased plasma glucose and decreased plasma nonesterified fatty acids and beta-hydroxybutyrate prior to calving. Despite these changes in metabolism, bST did not affect concentrations of fat and triglyceride in the liver prepartum or postpartum. Feeding the 17.8% protein diet failed to stimulate glucose metabolism and tended to elevate plasma beta-hydroxybutyrate in late gestation. Cows treated with bST produced 3.3 kg/d more milk than did controls across the first 42 d of lactation; the difference was 4.6 kg/d in wk 6 of lactation. The use of bST in late gestation has considerable promise to alter cow metabolism positively. The results of these and other possible periparturient responses to somatotropin may increase milk production in early lactation.     

Evaluation of sometribove in a prolonged-release system in lactating dairy cows--production responses

Primiparous (n = 105) and multiparous (n = 136) Holstein cows were used to evaluate efficacy of sometribove (n-methionyl bovine somatotropin, bST) in a dose titration study. Cows were fed TMR for ad libitum intake, were milked twice daily, and were allocated randomly within parity (1 vs. 2+) to treatments of 0, 250, 500, or 750 mg bST/14 d in a prolonged-release formulation. Subcutaneous injections commenced 60 +/- 3 d postpartum and continued throughout lactation. During a standardized treatment period of 252 d, treatment with increasing dosages of bST increased 3.5% FCM yield in a dose-dependent manner for both primiparous (2.5 kg/d, 10.2%; 3.5 kg/d, 14.3%; and 5.9 kg/d, 24.1%) and multiparous cows (3.1 kg/d, 12.1%; 3.9 kg/d, 15.2%; and 6.8 kg/d, 26.5%). Milk content of fat, protein, lactose, ash, Ca and P, and SCC were not affected by treatment. Over the 252-d treatment period, voluntary intake of energy was increased in bST-treated cows such that BW gain, body condition score, and net energy balance did not differ among treatment groups. Productive efficiency (milk per unit NEL intake corrected for BW change) over the treatment period was significantly increased in a dose-dependent manner for multiparous cows (4.1, 6.8, and 11.0%). Results demonstrated that bST administered in a prolonged-release formulation was efficacious in enhancing milk production and feed efficiency.     

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.     

Recombinant bovine somatotropin with lactating cows fed diets differing in energy density

Sixty-four Holstein cows (32 primiparous) were assigned randomly at parturition to one of two diets differing in forage:grain ratio and were further assigned to either control or treatment with recombinant bST. A full lactation study was conducted. Total mixed rations consisted of alfalfa silage, high moisture ear corn, soybean meal, and vitamin and mineral supplements. Percentages of forage in the diet (dry basis) for the high and medium energy diets were wk 1 to 12, 38.2 and 58.2; wk 13 to 26, 48.2 and 68.2; and wk 27 to 44, 68.2 and 88.2. Injection of a saline placebo or 20.6 mg/d per cow of bST started at wk 13 and stopped at wk 43 of lactation. Administration of bST increased 305-d milk yield by 19.9 and 18.3% for multiparous cows fed high and medium grain diets and by 13.0 and 5.9% for primiparous cows fed the same diets. Body weight gain during lactation tended to be lower for cows treated with bST, and body condition scores were significantly lower for those treated with bST and fed the medium energy diets. Daily injection of bST did not change concentrations of glucose or urea in blood or beta-hydroxybutyrate in plasma. Multiparous cows had a transitory increase in plasma FFA concentration immediately after bST treatment started. Milk composition, health, and reproductive parameters observed were not adversely affected by bST administration. Cows fed low energy diets during bST administration in the first lactation did not produce as much milk as controls when compared during the first 10 wk of their second lactation.     

Responses to metabolic challenges in dairy cows with high or low milk yield during an extended lactation

Responses of dairy cows with high or low milk yield (MY) beyond 450 d in milk (DIM) to 3 metabolic challenges were investigated. Twelve multiparous Holstein-Friesian cows that calved in late winter in a pasture-based system were managed for a 670-d lactation by delaying re-breeding. Cows were selected for either high MY (18.9 ± 1.69 L/cow per d; n = 6) or low MY (12.3 ± 3.85 L/cow per d; n = 6) at 450 DIM. Cows were housed indoors for 2 periods of 12 d at approximately 460 and 580 DIM. Each cow was fed freshly cut pasture (460 DIM) or pasture silage (580 DIM) plus 6.0 kg of DM barley grain daily (approximately 200 MJ of total metabolizable energy/cow per day). At all other times, cows were managed as a single herd and grazed pasture supplemented with cereal grain to an estimated intake of 180 MJ of metabolizable energy/cow per d. Cows were fitted with a jugular catheter during the final week of each experimental period. Over a period of 3 d, each cow underwent an intravenous glucose tolerance test (0.3 g/kg of body weight), an insulin tolerance test (0.12 IU of insulin/kg of body weight), and a 2-dose epinephrine challenge (0.1 and 1.6 µg/kg of body weight). Cows selected for high MY had greater milk and milk solids yields between 450 and 580 DIM than low MY cows (17.3 vs. 10.8 ± 1.49 kg of milk/d and 2.4 vs. 1.5 ± 0.23 kg of milk solids/d). The results indicated that whole body and peripheral tissue responsiveness to insulin may vary between cows of high and low MY. Following the glucose tolerance test, high MY cows had a lower plasma insulin response with a greater glucose area under the curve than low MY cows. Further, high MY cows had slower plasma glucose clearance compared with low MY cows during an insulin tolerance test. The plasma nonesterified fatty acid (NEFA) responses to the IVGTT and the ITT were similar between cows of high and low MY, but the clearance of NEFA from the plasma following both the IVGTT and ITT were slower at 580 compared with 460 DIM. The sensitivity to epinephrine was greater in high MY cows compared with low MY cows as the glucose and NEFA area under the curve and the percentage change in NEFA were greater in high MY after the low dose epinephrine challenge. However, the lipolytic but not the glucose appearance in response to epinephrine was greater in high MY cows than low MY cows. Following the high dose of epinephrine, the glucose response was lower, but the NEFA response was greater in high MY compared with low MY cows. Cows able to sustain greater MY to 580 DIM had a greater propensity for lipid mobilization, possibly enhancing nutrient partitioning to the mammary gland during the late stages of an extended lactation.     

Somatotropin treatment for a second consecutive lactation

Twenty-five Holstein cows were used to examine effects of recombinant bST administration for a second successive lactation on milk yield and composition, BW change, body condition, and health. Treatments were 0 (physiological saline), 10.3, 20.6, and 33 mg bST/d (8, 8, 7, and 3 cows per treatment, respectively). Saline and bST were given daily as subcutaneous injections beginning 4 to 5 wk postpartum and continuing for 38 wk. Somatotropin increased 3.5% FCM yield linearly from 8 to 36% over controls (control FCM was 30.1 kg/d). Milk composition was not affected by bST except that milk from cows given the 10.3-mg dosage had slightly higher Ca and P contents than did milk from cows receiving 0 or 20.6 mg. Cows receiving bST were 9 to 30% more efficient than controls in converting feed to milk. Body weight gain was unaffected by treatment. Average condition score was unchanged for control cows during the first 84 d following initiation of treatment, but declined in cows given bST. Thereafter, condition score increased in a similar manner for all groups. No treatment-related patterns were found in incidence of mastitis, feet and leg problems, ketosis, or milk fever. Blood hormone, chemistry, and hematology revealed no effects of bST treatment other than to raise plasma bST concentrations. Under conditions of this experiment, use of bST during a second consecutive lactation did not change the normal physiology or productive capacity of lactating cows.     

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 objectives of this experiment were to determine whether low doses of bovine somatotropin (bST) during the transition period and early lactation period improved dry matter intake (DMI), body weight (BW), or body condition score (BCS); provoked positive changes in concentrations of somatotropin, insulin, insulin-like growth factor-I (IGF-I), glucose, nonesterified fatty acids, and Ca; or improved milk yield (MY) response without obvious adverse effects on health status. Eighty-four multiparous Holstein cows completed treatments arranged in a 2 x 3 x 2 factorial design that included prepartum and postpartum bST, dry period (30 d dry, 30 d dry + estradiol cypionate, and 60 d dry), and prepartum anionic or cationic diets. Biweekly injections of bST began at 21 +/- 3 d before expected calving date through 42 +/- 2 d postpartum (control = 0 vs. bST = 10.2 mg of bST/d; POSILAC). At 56 +/- 2 d in milk, all cows were injected with a full dose of bST (500 mg of bST/14 d; POSILAC). During the prepartum period and during the first 28 d postpartum, no differences in mean BW, BCS, or DMI were detected between the bST treatment group and the control group. During the first 10 wk of lactation, cows in the bST treatment group had greater mean MY and 3.5% fat-corrected milk yield and lower SCC than did cows in the control group. When cows received a full dose of bST, an increase in milk production through wk 21 was maintained better by cows in the bST group. Mean concentrations of somatotropin, IGF-I, and insulin differed during the overall prepartum period (d -21 to -1). During the postpartum period (d 1 to 28), cows in the bST group had greater mean concentrations of somatotropin and IGF-I in plasma. Concentrations of Ca around calving did not differ because of bST treatment. Results suggest that changes in concentrations of blood measures provoked by injections of bST during the transition period and early lactation period resulted in improved metabolic status and production of the cows without apparent positive or negative effects on calving or health.     

Concentrate supplementation of a diet based on medium-quality grass silage for 4 weeks prepartum: Effects on cow performance,health, metabolic status,and immune function

Because negative energy balance (EB) contributes to transition-period immune dysfunction in dairy cows, dietary management strategies should aim to minimize negative EB during this time. Prepartum diets that oversupply energy may exacerbate negative EB in early lactation, with detrimental effects on immune function. However, with lower body condition score (BCS) cows, it has been shown that offering concentrates in addition to a grass silage-based diet when confined during an 8-wk dry period resulted in increased neutrophil function in early lactation. The aim of this study was to examine if similar benefits occur when concentrate feeding was restricted to a 4-wk period prepartum. Twenty-six multiparous and 22 primiparous Holstein-Friesian cows were offered ad libitum access to medium-quality grass silage until 28 d before their predicted calving dates (actual mean of 32 d prepartum; standard deviation = 6.4). At this time multiparous cows had a mean BCS of 2.9 (standard deviation = 0.12) and primiparous cows a mean BCS of 3.0 (standard deviation = 0.14) on a 1 to 5 scale. Cows were then allocated in a balanced manner to 1 of 2 treatments (13 multiparous cows and 11 primiparous cows on each treatment): silage only (SO) or silage plus concentrates (S+C) until calving. Cows on SO were offered the same grass silage ad libitum. Cows on S+C were offered an ad libitum mixed ration of the same grass silage and additional concentrates in a 60:40 dry matter (DM) ratio, which provided a mean concentrate DM intake (DMI) of 4.5 kg/cow per d. After calving, all cows were offered a common mixed ration (grass silage and concentrates, 40:60 DM ratio) for 70 d postpartum. Offering concentrates in addition to grass silage during the 4 wk prepartum increased prepartum DMI (12.0 versus 10.1 kg/cow per d), EB (+40.0 versus +10.6 MJ/cow per d), and body weight (BW; 640 versus 628 kg), and tended to increase BCS (3.02 versus 2.97). However, postpartum DMI, milk yield, milk composition, BW change, BCS change, serum nonesterified fatty acid, and β-hydroxybutryrate concentrations, health, and corpus luteum measures were unaffected by treatment. The in vitro assays of neutrophil phagocytosis, neutrophil oxidative burst, and interferon gamma production, conducted on blood samples obtained at d 14 prepartum and d 3, 7, 14, and 21 postpartum, were unaffected by treatment. Primiparous cows had higher phagocytic fluorescence intensity at d 14 prepartum and d 3 and 7 postpartum; a higher percentage of neutrophils undergoing oxidative burst at d 3, 7, and 21 postpartum; and a higher oxidative burst fluorescence intensity at d 14 prepartum and d 7, 14, and 21 postpartum compared with multiparous cows. This suggests that neutrophil function of primiparous cows was less sensitive to the changes occurring during the transition period than that of multiparous cows. In conclusion, offering concentrates during the 4-wk period prepartum had no effect on postpartum DMI, milk yield, body tissue mobilization, EB, measures of neutrophil or lymphocyte function, health, or corpus luteum activity.     

The effect of extended calving intervals in high-yielding lactating cows on milk production and profitability

A field trial was conducted to examine the effect of extended calving interval (CI) on production and profitability of high yielding cows (n = 937). First insemination was performed at 154 and 93 d postpartum (pp), for treatment and control primiparous cows, respectively, and at 124 and 71 d pp for treatment and control multiparous cows, respectively. During the first experimental lactation, average daily value-corrected milk (VCM) yield was 28.5 and 27.7 kg/d of CI for treatment (n = 131) and control (n = 133) primiparous cows, respectively. No significant difference in average daily VCM yield (33.0 and 32.8 kg/d of CI) was found between treatment (n = 271) and control (n = 215) multiparous cows . In the first 150 d of the subsequent lactation, there were significant differences in milk and VCM production in favor of the treatment primiparous cows (41.4 vs. 39.7 kg of VCM/d) but no significant differences in the production of multiparous cows. Primiparous and multiparous cows with extended lactations were more profitable. During the first experimental lactation, there were advantages of $0.19 and $0.12/d of CI in the net returns for primiparous cows and multiparous cows with longer CI, respectively. When the economic analysis included the first experimental lactation plus the first 150 d of the subsequent one, the net return per day of CI was higher for cows with an extended voluntary waiting period: $0.21/d and $0.16/d for primiparous and multiparous cows, respectively. A delay of 60 d with respect to the usual voluntary waiting period in the beginning of inseminations of high yielding cows has economic advantages and allows the farmer an option for decisions regarding individual cows.     

Performance and nutrient digestibility by dairy cows treated with bovine somatotropin and fed diets with steam-flaked sorghum or steam-rolled corn during early lactation

This study compared effects of exogenous bovine somatotropin (bST) on the performance of early lactation cows fed diets differing in ruminally degradable starch. Thirty-two Holstein cows (24 multiparous) in early lactation (5 d in milk) were divided into four groups and fed diets containing 39% grain as steam-flaked sorghum or steam-rolled corn with or without exogenous bST for 90 d. Grain processing did not affect dry matter intake as a percentage of body weight or yields of milk, but steam-rolled corn improved efficiency of feed utilization during the first 45 d of the study. Cows receiving bST had lower dry matter intake during the first 45 d of treatment. Milk yield and efficiency of feed utilization were increased by bST treatment, and milk yield response was greater during the first half than during the second half of the study. Milk composition and yield of milk components did not differ among treatments. Flaked sorghum increased in vitro starch hydrolysis and digestibilities of dry matter, organic matter, and starch, but neither method of grain processing nor bST affected digestibilities of crude protein, acid detergent fiber, or neutral detergent fiber. Grain type did not affect milk yield, and responses to bST were lower from 7 to 13 wk than from 1 to 6 wk prepartum.     

Anti-idiotypic responses of lactating cows immunized with monoclonal antibodies against bovine somatotropin.

The objective of this study was to produce anti-idiotypic antibodies with bovine somatotropin (bST)-like activity by active immunization of lactating cows and to determine their effects on milk yield. Several monoclonal antibodies against bST were evaluated for their interaction with bST in a rat growth bioassay. Two bST-agonist monoclonal antibodies (1 and 2), and two bST-antagonist monoclonal antibodies (3 and 4) were selected. Cows were immunized with immunoglobulin G as a control (n = 12) or with one of the four anti-bST monoclonal antibodies (1, 2, 3, 4; n = 12) on d 3, 24, 45, 66, 87, 108, 129, and 150 of lactation. From wk 3 of lactation, all cows immunized with each of the four anti-bST monoclonal antibodies developed anti-idiotypes until wk 30 of lactation. Total lactation yields were not different among monoclonal antibodies 2, 3, and 4 and control cows (9299, 9321, 9733, and 9415 kg, respectively). However, cows immunized with anti-bST monoclonal antibody 1 had reduced lactation yield compared with cows on other treatments (8136 kg). Daily milk yield of cows immunized with monoclonal antibody 1 was decreased from wk 9 of lactation [36.2 vs. 40.9 kg/d (control)] until the end of lactation, concomitantly with decreased bST concentration from wk 9 of lactation. Cows immunized with anti-bST monoclonal antibody 4 had increased milk yield compared with that of controls during wk 3 to 6 and wk 18 to 21 of lactation. Therefore, anti-idiotypes directed against anti-bST 1 had bST-antagonistic effects on lactation performance; anti-idiotypes against anti-bST 4 transiently increased milk yield.     

Effects of transition diets varying in dietary energy density on lactation performance and ruminal parameters of dairy cows

Forty cows and twenty heifers were used to study the effects of dietary energy density during late gestation and early lactation on lactation performance and ruminal parameters. A 2 x 2 factorial arrangement of treatments was used. During prepartum (-28 d to calving), animals were fed a low energy density diet [DL; 1.58 Mcal of net energy for lactation (NE(L))/kg, 40% neutral detergent fiber (NDF) and 38% nonfiber carbohydrate (NFC)] or a high energy diet (DH; 1.70 Mcal NE(L)/kg, 32% NDF and 44% NFC). After calving, half of the cows from each prepartum treatment group were assigned to a low energy density diet (L; 1.57 Mcal NE(L)/kg, 30% NDF and 41% NFC) or a high energy density diet (H; 1.63 Mcal NE(L)/kg, 25% NDF and 47% NFC) until d 20 postpartum. After d 20, all cows were fed H until d 70. Animals fed DH had 19.8% greater dry matter intake (DMI; % of body weight) and 21.5% greater energy intake than animals fed DL prepartum and the response was greater for cows compared to heifers. Animals fed DH had lower ruminal pH compared to animals fed DL, but no major changes in volatile fatty acid concentrations were observed. Effects of dietary energy density during prepartum on postpartum production responses were dependent on parity. Primiparous cows fed DL had higher 3.5% fat-corrected milk yield and milk fat production and percentage during the first 10 wk of lactation than those fed DH. Prepartum diet did not affect lactation performance of multiparous cows. Cows fed H had higher DMI and energy intake for the first 20 d of lactation compared to cows fed L. Diets did not affect DMI after the third wk of lactation. Milk production increased faster for cows fed H compared to cows fed L. Animals fed DL-L sequence of treatments tended to have the lowest energy intake during the first 10 wk of lactation. Prepartum treatments did not affect ruminal fermentation characteristics postpartum. Cows fed H had lower ruminal pH and higher propionate concentrations than cows fed L. No prepartum x postpartum interactions were observed for ruminal fermentation parameters. The effects of DH on prepartum DMI did not carry over to the postpartum period or influence early postpartum production. Increasing concentrate content of the diet immediately postpartum instead of delaying the increase until d 21 postpartum is associated with a higher rate of increase.in milk production and higher DMI.     

Milk yield, health, and reproduction of dairy cows given somatotropin (Somavubove) beginning early postpartum.

Cows (n = 210) were assigned to the following treatments: uninjected controls through 130 d postpartum; zero to high, uninjected through 60 d then injected with 14 mg of bST/d from 61 through 130 d postpartum; low, 5 mg of bST/d from 14 through 130 d postpartum; low to high, 5 mg of bST/d from 14 through 60 d then 14 mg of BST/d from 61 through 130 d postpartum; and high, 14 mg of bST/d from 14 through 130 d postpartum. Cows given 5 mg of bST/d (low and low to high treatments) yielded 1.2 kg of FCM/d more and high group cows yielded 1.3 kg of FCM/d more than control cows between 14 and 60 d postpartum. Cows given bST yielded 2.7 to 4.1 kg of FCM/d more than control cows during 61 to 130 d postpartum. Overall, control cows yielded 35.1 kg of FCM/d, and bST-dosed cows yielded 2.2 to 3.2 kg/d more FCM. Low group cows had improved pregnancy rate (80.0%) and conception rate (82.2%) compared with high group cows (57.2 and 60.3%). Neither pregnancy (70.0%) nor conception rates (71.5%) of controls differed from other groups. However, low group cows had first service conception rate of 57.8% compared with 34.3% for high and 38.2% for low to high group cows. First postpartum estrus was observed in high group cows about 13 to 16 d later than in low and low to high group cows, whereas low group cows came into first estrus 9 d sooner than controls. Cows of high group had lower body condition than controls (2.5 vs. 2.9), but other groups did not differ (2.7 to 2.9) from controls. Health was not adversely affected. Early postpartum bST administration at 5 mg/d increases FCM and, perhaps, reproductive performance of dairy cattle compared with herdmates.     

Effects of shortening the close-up period length coupled with increased supply of metabolizable protein on performance and metabolic status of multiparous Holstein cows

This experiment was conducted to compare conventional (CON; 21 d) and shortened (SH; 10 d) close-up period, and evaluate the effect of shortened close-up period combined with feeding different metabolizable protein (MP) levels on dry matter (DM) intake, metabolic status, and performance of dairy cows. Forty-eight multiparous Holstein cows with similar parity, body weight (BW), and previous lactation milk yield were divided into 2 groups. The first group (n = 24) received the far-off diet from ?60 to ?21 d (CON), and the second group (n = 24) received same far-off diet from ?60 to ?10 d (SH) relative to expected parturition. Cows were then moved to individual stalls and randomly allocated to 1 of 3 close-up diets: low MP diet (LMP; MP = 79 g/kg of DM), medium MP diet (MMP; MP = 101 g/kg of DM), or high MP diet (HMP; MP = 118 g/kg of DM). Treatments were used in a 2 × 3 factorial arrangement with 2 lengths of close-up period (CON and SH) and 3 levels of MP (LMP, MMP, and HMP). All diets were fed for ad libitum intake during the close-up period. After calving, all cows received the same fresh cow diet. We found no interaction between close-up period length and MP levels for traits, except for postpartum serum fatty acids and β-hydroxybutyrate (BHB). The concentrations of postpartum serum fatty acids and BHB were higher on LMP than MMP and HMP diets in SH group. The cows of the SH group tended to produce less colostrum in the first milking than cows in CON group. The length of close-up period did not affect pre- and postpartum DM intake or energy balance of cows during the last week of prepartum, but cows of the CON group had greater BW changes during the last 3 wk before parturition than cows in SH group. Cows fed MMP and HMP diets consumed 1.2 and 1 kg more DM than for those fed LMP prepartum, respectively. The concentrations of prepartum BHB and Ca were higher for SH cows than CON group cows. Except for blood urea N concentration, no other blood metabolite in prepartum was affected by dietary MP. We found no effects of close-up period length or MP levels in the close-up diet on urinary pH, purine derivative excretion, and microbial N flow. Postpartum, milk yield was not affected by close-up period length, but cows in CON group tended to have higher 4% fat-corrected milk yield, had higher milk fat content and yield, had greater BW and body condition score loss, and higher energy negative balance than cows in the SH group. Cows fed MMP diet ate 1.8 kg more DM and yielded 3.37 kg more milk than those fed the LMP diet. Milk fat, protein, and lactose content, milk urea N, and somatic cell count were not affected by MP levels, but the yield of milk protein and lactose were higher on MMP diet than on LMP diet. Concentrations of postpartum serum fatty acids and BHB were decreased by shortening the close-up period length, but glucose, cholesterol, and triglyceride were similar between close-up groups. During the postpartum period, serum fatty acids, BHB, aminotransferase, and Ca concentrations were decreased by increasing the MP levels in the close-up diet. It appears from this data set that multiparous cows will benefit from a shortened close-up period, and feeding a moderate MP diet could improve DM intake, milk yield, and metabolic status of periparturient dairy cows.     

Individual variation in the milk yield response to bovine somatotropin in dairy cows

The objective was to relate the short-term milk yield response (MYR) following use of exogenous bovine somatotropin (bST) to changes in plasma concentrations of metabolites and hormones. Twenty-four Holstein cows (52 +/- 4.1 d postpartum) received daily subcutaneous injections of saline for 1 wk followed by subcutaneous injections of 33 mg/d of bST for 2 wk (Trial 1). The difference in milk yield between wk 1 and 3 for each cow was used to determine the 5 cows with the highest (HR) and 5 with the lowest responses (LR) to bST. These 10 cows were then used in 3 further trials of the same design (Trials 2, 3, and 4, conducted at 122, 181, and 237 +/- 7.6 d postpartum, respectively). Blood samples were taken 2 h after the administration of bST on d 1, 3, 5, 15, 17, and 19 of each trial. The HR group had consistently greater MYR to bST than the LR group throughout their lactation. The LR group had a higher milk yield and lower plasma insulin like growth factor-I (IGF-I) concentrations during the saline treatment in all trials. The increase in plasma somatotropin concentrations following injections of bST was greater for the LR group, whereas the difference in plasma IGF-I level between wk 1 and 3 was greater for the HR group. The HR group had lower levels of 3-hydroxy-butyrate and nonesterified fatty acids before bST treatment. Low short-term response to bST was associated with plasma concentrations of hormones and metabolites that indicate negative energy balance, although other factors may be involved.