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Effect of Dietary Energy and Previous Bovine Somatotropin on Milk Yield, Mastitis, and Reproduction in Dairy Cows1
Effect of Dietary Energy and Previous Bovine Somatotropin on Milk Yield, Mastitis, and Reproduction in Dairy Cows’ R.
w.
HEYKEN? R. J. HARMON, w. J. SILVIA, w. B. TUCKER? G. HEERSCHE, and R. G. E G G E ~ Department of Animal Science Unlversity of Kentucky Lexington 40546
indicating that WT-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. (Key words: bovine somatotropin, energy, lactating dairy cows, milk yield)
ABSTRACT
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, B W gains during lactation were similar for all treatments,
Abbreviation key: bST-1 = cows receiving bST treatment for the first lactation, bST-2 = cows receiving bST treatment for the second lactation, F:C = forage to concentrate ratio, IMI = intramammary infection. INTRODUCTION
Received February 6, 1991. Accepted June 14, 1991. ‘This manusCript (91-5-26) is published with the a p proval of the director of the Kentucky Agricultural Expaiment Station. +o whom requests for rcppints should be addressed. 3 ~ e n address: t ~nimalscience ~ ~ p a r t m e n Oual homa State University, Stillwater 74078. 4Amckan Cyanamid Company, Princctoq NJ. 1991 J Dairy Sci 74426-272
primarily because of the scarcity of exogenous bST, most studies evaluating its effects on performance of lactating dairy cows during the early 1980s had a duration of only 1 to 2 wk (10, 13, 17). However, with the advent of recombinant DNA technology and mass production of peptide hormones, more recent studies have examined responses to bST for 27 to 38 wk (3, 4, 5, 7, 8, 21). In addition to effects of administering bST during an entire lactation, bST use during consecutive lactations has practical significance. Annexstad et al. (1) reported that subcutaneous injection of 25 or 40 mg bST/d for 38 wk in a second, consecutive lactation increased DMI and 3.5% FCM yield compared with controls not receiving bST. In another study (12), direct comparison of cows receiving bST for the fist time to
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One of the cows initially assigned to 0 bST those receiving bST for either a second or third lactation revealed a greater response to bST and 40:60 F C erroneously received bST treatfrom the latter group. McBride et al. (15) ment. This increased the number of cows 6 0 reported that administration of bST for a sec- receiving bST for the first time and a a ond, consecutive lactation increased milk yield F:C to 6 and reduced the number of cows similarly to that of cows receiving bST for the receiving 0 bST and e 6 0 F:C to 4. Another first time; however, the increase in feed effi- cow assigned to 0 bST and F:C of 6040 ciency that they observed for cows receiving developed severe leg problems and was rebST for the first time was less than for those moved from the study, reducing this group to 4 receiving bST for a second, consecutive lacta- cows. Finally, 1 cow receiving bST for a section. 6 0 F C group developed ond lactation in the a Energy requirements are increased because a systemic infection; although the causative milk yields are elevated by bST. Needs appear organism was not isolated, the cow recovered. to be met primarily by an increase in feed Data from this cow remain in the summary, intake or, when cows are in negative energy although mean milk yield was depressed for balance, by lipid mobilization (16). Because that treatment group during the remainder of the restoration of body energy stores during the study. Cows initially were housed in a tie-stall late lactation is important to yield in subsequent lactations, the objective of our aid was barn and were allowed ad libitum access to a to evaluate the influence of two dietary energy TMR offered twice daily. However, after 24 concentrations on milk yield, milk composi- wk of treatment, three replicates of cows (18 tion, BW, and health of lactating dairy cows cows) were moved to a loose housing area and receiving bST either for the first time or for a fed in groups. Feed intake data presented from second. consecutive lactation. this study represent only the observations from cows fed individually. Diets (Table I) consisted of corn and alfalfa silages in a 1:l DM MATERIALS AND METHODS ratio in a TMR with a commercial, pelleted Thirty multiparous, lactating Holstein cows concentrate. The low energy and high energy were blocked according to time of calving and diets were formulated with 60:40 and 4&60 assigned to a 2 x 3 factorial arrangement of F:C ratios (DM basis). Feed samples were coltreatments in a randomized complete block lected weekly, cornposited monthly, and frozen design. Factors were dietary forage to concen- for subsequent nutrient analyses (2). Cows trate (F:C) ratios (60:40 or 4050) and bST were milked twice daily at 0430 and 1530 h; treatment (no bST, cows receiving bST for the milk was sampled twice weekly during confirst time, or cows receiving bST for a second, secutive am. and p.m. milkings and analyzed consecutive lactation). Individual treatments for fat, protein (Multi-Spec 2, Multispec Limitwere 1) 0 bST and F C of 60:40 (DM basis); ed, Wheldrake, York, England), and SCC 2) 0 bST, F:C of 40:60; 3) 0 previous bST, (Coulter milk cell counter, Coulter Electronics, 20.6 mg of bST/d per cow, F:C of 60:40; 4) 0 Hialeah, FL). Body weights were recorded previous bST, 20.6 mg of bST/d per cow, and weekly. F:C of 40:60; 5 ) cows receiving bST during Duplicate quarter foremilk samples were preceding lactation, given 20.6 mg of bST/d collected aseptically for bacteriological examiper cow, and F:C of 60:40; and 6) cows receiv- nation monthly during the first 5 mo of the ing bST during preceding lactation, given 20.6 trial and every 2 mo thereafter. Teats were mg of bST/d per cow, and F C of 4&60. Cows washed with water and thoroughly dried with receiving bST for the second lactation previ- single-use paper towels. Teat ends were ously had received either 10.3, 20.6, or 41.2 scrubbed with cotton swabs soaked in 70% mg of bST/d per cow. Treatments were admin- isopropyl alcohol prior to sample collection. istered for 39 wk, beginning 28 to 35 d post- Samples were collected into sterile, screwcap partum. Dry, powdered bST was reconstituted glass tubes and stored at 4°C until plating. in buffered saline and administered once daily Each milk sample was plated (.01 ml) within via subcutaneous injection, rotating among 18 h onto one quadrant of a 5% blood esculin four sites on the neck. agar plate to determine the presence of mastitis Journal o f Dairy Science Vol. 74, No. 12. 1991
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SOMATOTROPIN FOR A SECOND LACTATION TABLE 1. Ingredient and nutrient composition of experimental diets listed as a percentage @M basis). Forage to concentrate ratio Ineredient ~
6040
40:m
30.00
20.00 20.00
~
Corn silage Alfalfa silage Wheat middlings Ground corn Corn distillers dried grains Soybean meal (48% CP) Sodium bicarbonate Limestone Dicalcium phosphate Potassium-magnesium sulfate S d u m chloride Trace-mineral mix Vitamin A and D premix
Nutrient DM CP ML, Mcavkg
ADP ADF
Ca
P
30.00 12.36 11.26
18.54 16.89 15.00 6.59
10.00
4.39 .60 .40 .40 .20 .20 .I5
.90 .60
.so 30 .30 .22
.04
.06
Alfalfa silage
Corn silage
38.20 19.30 1.25 37.50 49.70 1.62 .34
39.10 9.30 1.43 29.20 58.00 .36 .24
pathogens. Isolated microorganisms were identified as described by Matthews et al. (14). A quarter was considered to have an intramammaxy infection (IMI) when duplicate quarter samples yielded the same organism. If only one of the duplicate samples was positive for a pathogen, then the quarter was considered free of infection. Two exceptions to this were if Staphylococcus aureus and coliforms were isolated. Because of the likelihood of infected quarters shedding low numbers of organisms, any isolation of S. aureus or coliforms in pure culture was considered an IMI.The isolation of multiple (23) colony types from a sample was considered contamination. If one sample was contaminated but its duplicate was negative, the quarter was considered negative. The detection of an IMI for the first time during the bST injection period was considered a new infection. However, only one new IMI for each pathogen was counted for each quarter during the trial. Cows were allowed access to either sand or concrete exercise lots for 3 to 4 h/d and were observed for estrus during this time and during the a.m. milking. Beginning d 70 postpartum, weekly blood samples were collected via coc-
Concentrate
90.60 20.20 1.91 10.10 35.30 .87
.93
cygeal venipuncture until the cow was diagnosed pregnant. Blood was centrifuged, and plasma was analyzed for progesterone concentration via radioimmunoassay (20). Initiation of ovarian luteal activity was identified as the 1st wk of 2 consecutive wk in which plasma progesterone concentrations were greater than 1 ng/ml (18). Statistical analysis was via SAS general linear models ANOVA (19); the model included bST administration, dietary energy content, bST by energy content interaction, and residual error. Single degree of freedom contrasts were employed to compare control versus bST and first versus second lactation bST. Preliminary BW was utilized as a covariate for analyzing mean BW for the last 4 wk of the study. Chi-square analysis was utilized to test the statistical sigmficance of new IMI.Significance was declared at P < .05 unless otherwise noted. RESULTS AND DISCUSSION
Mean DMI for the first 24 wk are presented in Table 2. Figure 1 presents intake for the entire 39-wk period. During the fmal 15 wk, J o d of Dairy Science Vol. 74. No. 12, 1991
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SOMATOTROPIN FOR A SECOND LACTATION
a" e
-z*
.m
-6 1- 0 I O 20 30 40
Week Figure 1. Dry matter intake versus week of study for
25+I 20t 15 1 . . . . 0 I O 20 30 40
Week
cows receiving no bST (. - -), bST for the first time (----) ,and bST for (he second, consecutive lactation (- -
Figure 2. Milk yield versus week of study for cows receiving no bST (. -. - .), bST for the first time (- ---), and bST for the second, consecutive lactation (----).
data were included only for the three replicates maintained in the tie-staU barn. Although DMI was somewhat higher (nonsignificant) for the high energy density diet, the only treatment effect was an increase in DMI for cows treated with bST; cows receiving bST for the first (bST-1) and second lactations (bST-2) consumed 1.6 and 2.4 kg more DM than controls. Intake (Figure 1) increased dramatically for bST-2 during the first 10 wk of the study; after wk 10, however, intake decreased to approximately that of controls until wk 33, when it recovered to that of bST-1. Intake for bST-1 was a little higher (nonsignificant) than the control throughout the study. Bauman et al. (4) reported that feed intake increased in response to bST administration and that, by wk 10, intake was adequate to place the cows in positive energy balance. After wk 10, mean intake for bST cows remained higher than for controls throughout their study. In our study, the reduction in feed intake after wk 10 for bST-2 was reflected in slightly lower (nonsignificant) milk yield than for bST1 when averaged for the entire study (Table 2); this response was most pronounced during the last 19 wk of treatment (Figure 2) when yield of bST-2 cows was similar to that of controls. When averaged for the entire trial, both bST treatments produced more milk, fat, and protein than controls. Inclusion of data from 1
bST-2 cow that developed a systemic infection may have affected performance on this treatment. Gibson et al. (11) reported that during the first 9 wk of their study, WT-treated cows receiving bST in previous lactations produced 9.2% less milk than those receiving bST for the first time, but, when averaged for the entire 38-wk period, yield was similar for the first lactation and multiple lactation bST treatments. They suggested that previous treatment with bST may have reduced body condition and milk yield during the early phase of the treatment. In contrast, Huber et al. (12) reported that milk yield response to bST was greater for second and third lactations than for the fnst lactation of administration. In our study, inability of bST-2 cows to maintain milk yield above that of controls after 20 wk of bST treatment appears correlated with a corresponding reduction in DMI during wk 20 through 33. The reason for this decreased DMI is unclear. Milk fat content (Table 2) was two points higher (nonsigdicant) for the low energy diet, but the corresponding reduction in milk yield for this diet resulted in similar milk fat yields for low versus higher energy density diets. Energy density of the diet had no effect on milk protein content (Table 2), but protein yield tended to be higher for the high energy diet as the result of increased milk yield with
-.
- -).
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HEMKEN ET AL.
700 -
700 -
9 650m
. . . I 550 0 10 20 30 40
550 . . 4 0 10 20 30 40 Week
I
a
I
a
-'
9
Week ing no bST
P i p e 3 . Body weight versus of study for cows receiv6 - .-.), bST for the fust time (----), or bST for the second, consecutive lactation (- - - -).
Figure 4. Body weight versus week of study for cows receiving diets containing a forage to concentrate ratio of 6040 (.-.-.) or 40x50 (----).
the higher energy diet. Milk SCC was not affected by either energy density of the diet or bST treatment. The increase in fat yield for bST cows was the result of both higher milk yield (P < .05) and milk fat percentage ( P < .Ol), whereas the higher protein yield was attributable primarily to increased milk yield. West et al. (23) reported that milk fat percentage for Holstein cows increased quadratically ( P < .05) as bST dose was increased from 0 to 20 mg/d, whereas that of Jersey cows was unaffected. According to Peel and Bauman (16), milk fat
content increases in response to bST administration only when cows are placed in a negative energy balance. Although protein yield typically increases with bST administration, this response is due to increased milk yield; protein content of the milk generally is not affected by bST. However, if bST places cows in negative N balance, milk protein content can be reduced (16). Body weight (Table 2, Figures 3 and 4) was not affected by dietary energy density or bST treatment. All cows gained weight during the study so that body reserves for the subsequent
TABLE 3. New inbamammary infections in control versus bST-treated cows.
Organism
First lactation
None (n)
Negative' 18' SraphyIococcus a w w s 3 Coagulase-negative staphylococci 6 ~treptococci~ 1 Colifom 0 Corynebacteria 1 Total quarters 32 Total cows 8
(W2
(n)
56.3 9.4
18
18.8 3.1 0 3.1
9 3 1 2 43 11
5
Second lactation
(n)
(%I
41.9 11.6
19
52.8 13.9
20.9 7.0 2.3 4.7
6 3
5
0
2 36 9
%fferences within each type of pathogen or for total infections were not significant (E' > .05). 'Quarters remained bacteriologically negative during treatment period. 2Percentage of total quarters within each treatment group. '~meptocaccus spp. other than ~treptococcusagalactiae. Journal of Dairy Science Vol. 74, No. 12, 1991
16.7 8.3 0 5.6
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SOMATOTROPIN FOR A SECOND LACTATION TABLE 4. Influence of bST administration and dietary energy concentration on reproductive performance. Days from calving to first eshus No bST Low energy High energy First lactation bST LOW energy High energy Second lactation bST Low energy High energy Energy density LOW
High
bST Treatment None First lactation Second lactation
cows conceiving
Services Per conception'
84.2 69.8
3of4 4 of 4
5.67 4.25
127.8 93.2
2 of 5 5 of 6
2.50 3.60
130.2 70.0
4 of 5 2 of 5
3.00 1.00
116.2 79.2
9 of 14 1 1 of 15
3.78 3.36
77.0 119.8 100.1
7 of 8 7 of 11 6 of 10
4.86 3.29 2.33
'Calculated only for cows that conceived.
lactation were assumed to be similar for each treatment; however, this assumption is justified only if bST administration does not change body composition. If nutritional support for the extra milk produced with bST treatment is inadequate, body energy reserves wouId be reduced; that could reduce the response to bST in the subsequent lactation (11). If body reserves are maintained during bST administration, response to it in subsequent lactation appears to be similar to that of cows receiving bST for the first time. Chi-square analysis revealed no effect of treatment on new LMI (Table 3). The increased milk yield associated with bST treatment might be expected to increase the vulnerability of the mammary gland to injury and infection. However, Eppard et al. (9) reported that administration of bST for 188 d did not increase the incidence of clinical mastitis. In the present study, milk was cultured routinely to detect new infections. Although numbers of infections for each pathogen were low, there was no effect of bST on total new infections. These results are consistent with the absence of treatment effects on SCC (Table 2). Days from calving to first observed estrus were not significantly higher for the low versus high energy diets (Table 4) but were higher for both bST-1 and bST-2 than for controls.
Negative energy balance during early lactation will increase interval to first ovulation (6), a response possibly mediated via a reduction in insulin-like growth factor-I production (22). In our study, interval to first observed estrus was longest for bST-1 cows. The DMI of bST-1 cows increased more slowly than for bST-2 cows and, because milk yield was similar between the two groups, may have reduced energy balance more severely and thereby retarded reproductive function. Ovarian quiescence, which we defined as a period of at least 4 consecutive wk during which serum progesterone remained below 1 ng/ml, was exhibited more frequently by cows receiving bST (11 of 21) than by controls (2 of 8). However, because of our small sample size, chi-square analysis detected no difference (P> .lo) between these groups. In our study, 7 of 8 controls (88%) became pregnant compared with 13 of 21 cows (62%) receiving bST (Table 4). Paradoxically, services per conception were somewhat lower for the bST treatments than for control, suggesting the possibility that cows cycling normally may conceive more readily, albeit later, when treated with bST. CONCLUSIONS
Cows receiving bST for either the first time or €or a second, consecutive lactation produced Journal of Dairy Science Vol. 74, No. 12, 1991
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similar amounts of milk and produced more milk than untreated controls until wk 20 of bST administration; after wk 20, however, milk yield of cows receiving bST for a second lactation decreased to that of controls. The reason for this reduction is not apparent; it may be attributable partially to inclusion of data from 1 cow with a systemic infection. Dietary energy concentration did not influence response to bST; however, we did not evaluate the effects of an energy-deficient diet. Temporal changes in DMI and milk yield accompanying administration of bST for consecutive lactations should be evaluated further to determine nutritional aspects of managing for successful, chronic administration of bST. REFERENCES 1 Annexstad, R. J., D. E. Otterby, J. G. Linn, W. P. Hansen, C. G. Sodexholm, and R. G. Eggert. 1987. Responses of cows to daily injections of recombinant bovine somatotropin @ST) during a second lactation. I. Dairy Sci. 7qSuppl. 1):176.(Abstr.) 2Association of Official Analytical Chemists. 1980. Official methods of analysis. 12th ed. AOAC, Washington, Dc. 3 Baird, L. S., R W.Hemken, R. J. Harmon, and R. G. Eggert. 1986. Response of lactating dairy cows to recombinant bovine growth hormone (rbGIi). J. Dairy Sci. 69(Suppl. 1):118.(Abstr.) 4Bauman. D. E., P. J. Eppard, M. J. D a t e r , and G. M. Lanza. 1985. Responses of high producing dairy cows to long-tenn treatment with pituitary somatotropin and recombinant somatotropin. J. Dairy Sci. 68: 1352. SBurton, J. H., B. W. McBride. K. Bateman, G. K. Macleod, and R. G. Eggert. 1987. Recombinant bovine somatotropin: effects on production and reproduction in lactating cows. J. Dairy Sci. 7O(Suppl. 1): 175.(Abstr.) 6Butler, W. R, and R D. Smith 1989. Interrelationships between enezgy balance and postpartum reproductive fimction in dairy cattle. J. Dairy Sci 72:767. 7Chalup4 W., L. Baird, C. Soderholm, D. L. Palmquist, R W. Hemken, D. Ottertry, R. Annexsted, B. Vecchiarelli, R. Harmon, A. Sinha, J. Linn, W. Hansen, F. Ehle, P. Schneider. and R. Eggert. 1987. Responses of dairy cows to somatotropin. J. Dairy Sci. 7O(Suppl. 1):176.(Abstr.) 8 Chalupa,W., B. Vccchiarelli, P.Schneider, and R. 0. Eggert 1986. Long-term responses of lactating cows to daily injection of recombinant somatotropin. J. Dajr Sci. 69(Suppl. l):lSl.(Absir.) 9 Eppard, P. J., D. E. Bauman, C.R. Cmtis, H. N. Erb,
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G. M, Lama, and M. J. m e t e r . 1987. Effect of 188-day treatment with somatotropin on health and reproductive performance of lactaw dairy cows. J. Dairy Sci. 70582. lOFronk, T. J.. C. J. Peel, D. E. Bauman, and R. C. Gorewit. 1983. Comparison of different palterns of exogenous growth hormone administration on milk production in Holstein cows. J. Anim. Sci. 57699. 1 Gibson, J. P., B. W. McBride, I. H. Burton, and R. G. Eggen. 1990. Effect on production haits of administration of rbST for up to three consecutive lactations. J. Dairy Sci. 73(Suppl. 1):158.(Abstr.) 2Huber. I. T., J. L. Sullivan, and S. Willman. 1990. Response of Holstein cows to biweekly sometribove (SB) injections for three. consecutive lactations. J. Dairy Sci. 73(Suppl. 1): 157.(Abstr.) 3MaChlin, L. J. 1973. Effect of growth hormone on milk production and feed utilization in dairy cows. J. Dairy Sci. 56:575. 4 Matthews, K. R., R. J. Harmon, B. E. Langlois, W. L. Crist, and R. W. Hemken. 1988. Use of latex teat dip with germicide during the prepartum period. J. Dairy Sci. 71:1940. 15 McBride, B. W., J. L. Burton, I. P. Gibson,J. H. Burton, and R. G. Egg&. 1990. Use of recombinant bovine somatotropin for up to two consecutive lactations on dairy production traits.J. Dairy Sci. 73:3248. 16Pee1, C. J., and D. E. Bauman. 1987. Somatotropin and lactation. J. Dairy Sci. 70:474. 17Pee.1, C. J.. T. J. Fb% D. E. Bauman, and R. C. Gorewit 1983. Effect of exogenous growth hormone in early and late lactation on lactational performance of dairy cows. J. Dairy Sci. 66:776. 18Richds, M. W., R P. Wettemann. and H. M. Schoenemann. 1989. Nutritional anestrus in beef cows: concentxations of glucose and nonesterified fatty acids in plasma and insulin in serum. J. Anim. Sci. 672354. 19 SAS@User’s Guide: Statistics. 1982. SAS Jnst., Inc., Gary, NC. 20SiIvia, W. J., and M. L. Taylor. 1989. Relationship between uterine secretion of prostaglandin F2a ind a d by oxytocin and endogenous concentrations of estradiol and progesterone at three stages of the bovine estrous cycle. J. Anim. Sci. 67:2347. 21Soderholm. C. G., D. E. Otterby, F. R. Eble, I. G. Linu, W. P. Himen, and R. J. Annexstad. 1986. Effects of diffmnt doses of recombinant bovine m matotropin (rbSTH) on milk production, body composition, and condition score in lactating cows. J. Dairy Sci. 69(Suppl. 1):152.(Abstr.) 22Spicer, L. J., W. B. Tucker, and G. D. A h . 1990. Insuljn-like growih factor-I in dairy cows: relationships among energy tdance., body condition,ovarian activity, and estrous behavior. J. Dairy Sci. 73:929. 23 West, J. W.,K.Bondari, and J. C. Johoson, Jr. 1990. Effects of bovine somatotropin on milk yield and composition, body weight, and condition score of Holstein and Jersey cows. J. Dairy Sci. 731062.
w.
HEYKEN? R. J. HARMON, w. J. SILVIA, w. B. TUCKER? G. HEERSCHE, and R. G. E G G E ~ Department of Animal Science Unlversity of Kentucky Lexington 40546
indicating that WT-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. (Key words: bovine somatotropin, energy, lactating dairy cows, milk yield)
ABSTRACT
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, B W gains during lactation were similar for all treatments,
Abbreviation key: bST-1 = cows receiving bST treatment for the first lactation, bST-2 = cows receiving bST treatment for the second lactation, F:C = forage to concentrate ratio, IMI = intramammary infection. INTRODUCTION
Received February 6, 1991. Accepted June 14, 1991. ‘This manusCript (91-5-26) is published with the a p proval of the director of the Kentucky Agricultural Expaiment Station. +o whom requests for rcppints should be addressed. 3 ~ e n address: t ~nimalscience ~ ~ p a r t m e n Oual homa State University, Stillwater 74078. 4Amckan Cyanamid Company, Princctoq NJ. 1991 J Dairy Sci 74426-272
primarily because of the scarcity of exogenous bST, most studies evaluating its effects on performance of lactating dairy cows during the early 1980s had a duration of only 1 to 2 wk (10, 13, 17). However, with the advent of recombinant DNA technology and mass production of peptide hormones, more recent studies have examined responses to bST for 27 to 38 wk (3, 4, 5, 7, 8, 21). In addition to effects of administering bST during an entire lactation, bST use during consecutive lactations has practical significance. Annexstad et al. (1) reported that subcutaneous injection of 25 or 40 mg bST/d for 38 wk in a second, consecutive lactation increased DMI and 3.5% FCM yield compared with controls not receiving bST. In another study (12), direct comparison of cows receiving bST for the fist time to
4265
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One of the cows initially assigned to 0 bST those receiving bST for either a second or third lactation revealed a greater response to bST and 40:60 F C erroneously received bST treatfrom the latter group. McBride et al. (15) ment. This increased the number of cows 6 0 reported that administration of bST for a sec- receiving bST for the first time and a a ond, consecutive lactation increased milk yield F:C to 6 and reduced the number of cows similarly to that of cows receiving bST for the receiving 0 bST and e 6 0 F:C to 4. Another first time; however, the increase in feed effi- cow assigned to 0 bST and F:C of 6040 ciency that they observed for cows receiving developed severe leg problems and was rebST for the first time was less than for those moved from the study, reducing this group to 4 receiving bST for a second, consecutive lacta- cows. Finally, 1 cow receiving bST for a section. 6 0 F C group developed ond lactation in the a Energy requirements are increased because a systemic infection; although the causative milk yields are elevated by bST. Needs appear organism was not isolated, the cow recovered. to be met primarily by an increase in feed Data from this cow remain in the summary, intake or, when cows are in negative energy although mean milk yield was depressed for balance, by lipid mobilization (16). Because that treatment group during the remainder of the restoration of body energy stores during the study. Cows initially were housed in a tie-stall late lactation is important to yield in subsequent lactations, the objective of our aid was barn and were allowed ad libitum access to a to evaluate the influence of two dietary energy TMR offered twice daily. However, after 24 concentrations on milk yield, milk composi- wk of treatment, three replicates of cows (18 tion, BW, and health of lactating dairy cows cows) were moved to a loose housing area and receiving bST either for the first time or for a fed in groups. Feed intake data presented from second. consecutive lactation. this study represent only the observations from cows fed individually. Diets (Table I) consisted of corn and alfalfa silages in a 1:l DM MATERIALS AND METHODS ratio in a TMR with a commercial, pelleted Thirty multiparous, lactating Holstein cows concentrate. The low energy and high energy were blocked according to time of calving and diets were formulated with 60:40 and 4&60 assigned to a 2 x 3 factorial arrangement of F:C ratios (DM basis). Feed samples were coltreatments in a randomized complete block lected weekly, cornposited monthly, and frozen design. Factors were dietary forage to concen- for subsequent nutrient analyses (2). Cows trate (F:C) ratios (60:40 or 4050) and bST were milked twice daily at 0430 and 1530 h; treatment (no bST, cows receiving bST for the milk was sampled twice weekly during confirst time, or cows receiving bST for a second, secutive am. and p.m. milkings and analyzed consecutive lactation). Individual treatments for fat, protein (Multi-Spec 2, Multispec Limitwere 1) 0 bST and F C of 60:40 (DM basis); ed, Wheldrake, York, England), and SCC 2) 0 bST, F:C of 40:60; 3) 0 previous bST, (Coulter milk cell counter, Coulter Electronics, 20.6 mg of bST/d per cow, F:C of 60:40; 4) 0 Hialeah, FL). Body weights were recorded previous bST, 20.6 mg of bST/d per cow, and weekly. F:C of 40:60; 5 ) cows receiving bST during Duplicate quarter foremilk samples were preceding lactation, given 20.6 mg of bST/d collected aseptically for bacteriological examiper cow, and F:C of 60:40; and 6) cows receiv- nation monthly during the first 5 mo of the ing bST during preceding lactation, given 20.6 trial and every 2 mo thereafter. Teats were mg of bST/d per cow, and F C of 4&60. Cows washed with water and thoroughly dried with receiving bST for the second lactation previ- single-use paper towels. Teat ends were ously had received either 10.3, 20.6, or 41.2 scrubbed with cotton swabs soaked in 70% mg of bST/d per cow. Treatments were admin- isopropyl alcohol prior to sample collection. istered for 39 wk, beginning 28 to 35 d post- Samples were collected into sterile, screwcap partum. Dry, powdered bST was reconstituted glass tubes and stored at 4°C until plating. in buffered saline and administered once daily Each milk sample was plated (.01 ml) within via subcutaneous injection, rotating among 18 h onto one quadrant of a 5% blood esculin four sites on the neck. agar plate to determine the presence of mastitis Journal o f Dairy Science Vol. 74, No. 12. 1991
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SOMATOTROPIN FOR A SECOND LACTATION TABLE 1. Ingredient and nutrient composition of experimental diets listed as a percentage @M basis). Forage to concentrate ratio Ineredient ~
6040
40:m
30.00
20.00 20.00
~
Corn silage Alfalfa silage Wheat middlings Ground corn Corn distillers dried grains Soybean meal (48% CP) Sodium bicarbonate Limestone Dicalcium phosphate Potassium-magnesium sulfate S d u m chloride Trace-mineral mix Vitamin A and D premix
Nutrient DM CP ML, Mcavkg
ADP ADF
Ca
P
30.00 12.36 11.26
18.54 16.89 15.00 6.59
10.00
4.39 .60 .40 .40 .20 .20 .I5
.90 .60
.so 30 .30 .22
.04
.06
Alfalfa silage
Corn silage
38.20 19.30 1.25 37.50 49.70 1.62 .34
39.10 9.30 1.43 29.20 58.00 .36 .24
pathogens. Isolated microorganisms were identified as described by Matthews et al. (14). A quarter was considered to have an intramammaxy infection (IMI) when duplicate quarter samples yielded the same organism. If only one of the duplicate samples was positive for a pathogen, then the quarter was considered free of infection. Two exceptions to this were if Staphylococcus aureus and coliforms were isolated. Because of the likelihood of infected quarters shedding low numbers of organisms, any isolation of S. aureus or coliforms in pure culture was considered an IMI.The isolation of multiple (23) colony types from a sample was considered contamination. If one sample was contaminated but its duplicate was negative, the quarter was considered negative. The detection of an IMI for the first time during the bST injection period was considered a new infection. However, only one new IMI for each pathogen was counted for each quarter during the trial. Cows were allowed access to either sand or concrete exercise lots for 3 to 4 h/d and were observed for estrus during this time and during the a.m. milking. Beginning d 70 postpartum, weekly blood samples were collected via coc-
Concentrate
90.60 20.20 1.91 10.10 35.30 .87
.93
cygeal venipuncture until the cow was diagnosed pregnant. Blood was centrifuged, and plasma was analyzed for progesterone concentration via radioimmunoassay (20). Initiation of ovarian luteal activity was identified as the 1st wk of 2 consecutive wk in which plasma progesterone concentrations were greater than 1 ng/ml (18). Statistical analysis was via SAS general linear models ANOVA (19); the model included bST administration, dietary energy content, bST by energy content interaction, and residual error. Single degree of freedom contrasts were employed to compare control versus bST and first versus second lactation bST. Preliminary BW was utilized as a covariate for analyzing mean BW for the last 4 wk of the study. Chi-square analysis was utilized to test the statistical sigmficance of new IMI.Significance was declared at P < .05 unless otherwise noted. RESULTS AND DISCUSSION
Mean DMI for the first 24 wk are presented in Table 2. Figure 1 presents intake for the entire 39-wk period. During the fmal 15 wk, J o d of Dairy Science Vol. 74. No. 12, 1991
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Journal of Dairy Science Vol. 74, No. 12, 1991
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SOMATOTROPIN FOR A SECOND LACTATION
a" e
-z*
.m
-6 1- 0 I O 20 30 40
Week Figure 1. Dry matter intake versus week of study for
25+I 20t 15 1 . . . . 0 I O 20 30 40
Week
cows receiving no bST (. - -), bST for the first time (----) ,and bST for (he second, consecutive lactation (- -
Figure 2. Milk yield versus week of study for cows receiving no bST (. -. - .), bST for the first time (- ---), and bST for the second, consecutive lactation (----).
data were included only for the three replicates maintained in the tie-staU barn. Although DMI was somewhat higher (nonsignificant) for the high energy density diet, the only treatment effect was an increase in DMI for cows treated with bST; cows receiving bST for the first (bST-1) and second lactations (bST-2) consumed 1.6 and 2.4 kg more DM than controls. Intake (Figure 1) increased dramatically for bST-2 during the first 10 wk of the study; after wk 10, however, intake decreased to approximately that of controls until wk 33, when it recovered to that of bST-1. Intake for bST-1 was a little higher (nonsignificant) than the control throughout the study. Bauman et al. (4) reported that feed intake increased in response to bST administration and that, by wk 10, intake was adequate to place the cows in positive energy balance. After wk 10, mean intake for bST cows remained higher than for controls throughout their study. In our study, the reduction in feed intake after wk 10 for bST-2 was reflected in slightly lower (nonsignificant) milk yield than for bST1 when averaged for the entire study (Table 2); this response was most pronounced during the last 19 wk of treatment (Figure 2) when yield of bST-2 cows was similar to that of controls. When averaged for the entire trial, both bST treatments produced more milk, fat, and protein than controls. Inclusion of data from 1
bST-2 cow that developed a systemic infection may have affected performance on this treatment. Gibson et al. (11) reported that during the first 9 wk of their study, WT-treated cows receiving bST in previous lactations produced 9.2% less milk than those receiving bST for the first time, but, when averaged for the entire 38-wk period, yield was similar for the first lactation and multiple lactation bST treatments. They suggested that previous treatment with bST may have reduced body condition and milk yield during the early phase of the treatment. In contrast, Huber et al. (12) reported that milk yield response to bST was greater for second and third lactations than for the fnst lactation of administration. In our study, inability of bST-2 cows to maintain milk yield above that of controls after 20 wk of bST treatment appears correlated with a corresponding reduction in DMI during wk 20 through 33. The reason for this decreased DMI is unclear. Milk fat content (Table 2) was two points higher (nonsigdicant) for the low energy diet, but the corresponding reduction in milk yield for this diet resulted in similar milk fat yields for low versus higher energy density diets. Energy density of the diet had no effect on milk protein content (Table 2), but protein yield tended to be higher for the high energy diet as the result of increased milk yield with
-.
- -).
Journal of Dairy Science Vol. 74, No. 12, 1991
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HEMKEN ET AL.
700 -
700 -
9 650m
. . . I 550 0 10 20 30 40
550 . . 4 0 10 20 30 40 Week
I
a
I
a
-'
9
Week ing no bST
P i p e 3 . Body weight versus of study for cows receiv6 - .-.), bST for the fust time (----), or bST for the second, consecutive lactation (- - - -).
Figure 4. Body weight versus week of study for cows receiving diets containing a forage to concentrate ratio of 6040 (.-.-.) or 40x50 (----).
the higher energy diet. Milk SCC was not affected by either energy density of the diet or bST treatment. The increase in fat yield for bST cows was the result of both higher milk yield (P < .05) and milk fat percentage ( P < .Ol), whereas the higher protein yield was attributable primarily to increased milk yield. West et al. (23) reported that milk fat percentage for Holstein cows increased quadratically ( P < .05) as bST dose was increased from 0 to 20 mg/d, whereas that of Jersey cows was unaffected. According to Peel and Bauman (16), milk fat
content increases in response to bST administration only when cows are placed in a negative energy balance. Although protein yield typically increases with bST administration, this response is due to increased milk yield; protein content of the milk generally is not affected by bST. However, if bST places cows in negative N balance, milk protein content can be reduced (16). Body weight (Table 2, Figures 3 and 4) was not affected by dietary energy density or bST treatment. All cows gained weight during the study so that body reserves for the subsequent
TABLE 3. New inbamammary infections in control versus bST-treated cows.
Organism
First lactation
None (n)
Negative' 18' SraphyIococcus a w w s 3 Coagulase-negative staphylococci 6 ~treptococci~ 1 Colifom 0 Corynebacteria 1 Total quarters 32 Total cows 8
(W2
(n)
56.3 9.4
18
18.8 3.1 0 3.1
9 3 1 2 43 11
5
Second lactation
(n)
(%I
41.9 11.6
19
52.8 13.9
20.9 7.0 2.3 4.7
6 3
5
0
2 36 9
%fferences within each type of pathogen or for total infections were not significant (E' > .05). 'Quarters remained bacteriologically negative during treatment period. 2Percentage of total quarters within each treatment group. '~meptocaccus spp. other than ~treptococcusagalactiae. Journal of Dairy Science Vol. 74, No. 12, 1991
16.7 8.3 0 5.6
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SOMATOTROPIN FOR A SECOND LACTATION TABLE 4. Influence of bST administration and dietary energy concentration on reproductive performance. Days from calving to first eshus No bST Low energy High energy First lactation bST LOW energy High energy Second lactation bST Low energy High energy Energy density LOW
High
bST Treatment None First lactation Second lactation
cows conceiving
Services Per conception'
84.2 69.8
3of4 4 of 4
5.67 4.25
127.8 93.2
2 of 5 5 of 6
2.50 3.60
130.2 70.0
4 of 5 2 of 5
3.00 1.00
116.2 79.2
9 of 14 1 1 of 15
3.78 3.36
77.0 119.8 100.1
7 of 8 7 of 11 6 of 10
4.86 3.29 2.33
'Calculated only for cows that conceived.
lactation were assumed to be similar for each treatment; however, this assumption is justified only if bST administration does not change body composition. If nutritional support for the extra milk produced with bST treatment is inadequate, body energy reserves wouId be reduced; that could reduce the response to bST in the subsequent lactation (11). If body reserves are maintained during bST administration, response to it in subsequent lactation appears to be similar to that of cows receiving bST for the first time. Chi-square analysis revealed no effect of treatment on new LMI (Table 3). The increased milk yield associated with bST treatment might be expected to increase the vulnerability of the mammary gland to injury and infection. However, Eppard et al. (9) reported that administration of bST for 188 d did not increase the incidence of clinical mastitis. In the present study, milk was cultured routinely to detect new infections. Although numbers of infections for each pathogen were low, there was no effect of bST on total new infections. These results are consistent with the absence of treatment effects on SCC (Table 2). Days from calving to first observed estrus were not significantly higher for the low versus high energy diets (Table 4) but were higher for both bST-1 and bST-2 than for controls.
Negative energy balance during early lactation will increase interval to first ovulation (6), a response possibly mediated via a reduction in insulin-like growth factor-I production (22). In our study, interval to first observed estrus was longest for bST-1 cows. The DMI of bST-1 cows increased more slowly than for bST-2 cows and, because milk yield was similar between the two groups, may have reduced energy balance more severely and thereby retarded reproductive function. Ovarian quiescence, which we defined as a period of at least 4 consecutive wk during which serum progesterone remained below 1 ng/ml, was exhibited more frequently by cows receiving bST (11 of 21) than by controls (2 of 8). However, because of our small sample size, chi-square analysis detected no difference (P> .lo) between these groups. In our study, 7 of 8 controls (88%) became pregnant compared with 13 of 21 cows (62%) receiving bST (Table 4). Paradoxically, services per conception were somewhat lower for the bST treatments than for control, suggesting the possibility that cows cycling normally may conceive more readily, albeit later, when treated with bST. CONCLUSIONS
Cows receiving bST for either the first time or €or a second, consecutive lactation produced Journal of Dairy Science Vol. 74, No. 12, 1991
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similar amounts of milk and produced more milk than untreated controls until wk 20 of bST administration; after wk 20, however, milk yield of cows receiving bST for a second lactation decreased to that of controls. The reason for this reduction is not apparent; it may be attributable partially to inclusion of data from 1 cow with a systemic infection. Dietary energy concentration did not influence response to bST; however, we did not evaluate the effects of an energy-deficient diet. Temporal changes in DMI and milk yield accompanying administration of bST for consecutive lactations should be evaluated further to determine nutritional aspects of managing for successful, chronic administration of bST. REFERENCES 1 Annexstad, R. J., D. E. Otterby, J. G. Linn, W. P. Hansen, C. G. Sodexholm, and R. G. Eggert. 1987. Responses of cows to daily injections of recombinant bovine somatotropin @ST) during a second lactation. I. Dairy Sci. 7qSuppl. 1):176.(Abstr.) 2Association of Official Analytical Chemists. 1980. Official methods of analysis. 12th ed. AOAC, Washington, Dc. 3 Baird, L. S., R W.Hemken, R. J. Harmon, and R. G. Eggert. 1986. Response of lactating dairy cows to recombinant bovine growth hormone (rbGIi). J. Dairy Sci. 69(Suppl. 1):118.(Abstr.) 4Bauman. D. E., P. J. Eppard, M. J. D a t e r , and G. M. Lanza. 1985. Responses of high producing dairy cows to long-tenn treatment with pituitary somatotropin and recombinant somatotropin. J. Dairy Sci. 68: 1352. SBurton, J. H., B. W. McBride. K. Bateman, G. K. Macleod, and R. G. Eggert. 1987. Recombinant bovine somatotropin: effects on production and reproduction in lactating cows. J. Dairy Sci. 7O(Suppl. 1): 175.(Abstr.) 6Butler, W. R, and R D. Smith 1989. Interrelationships between enezgy balance and postpartum reproductive fimction in dairy cattle. J. Dairy Sci 72:767. 7Chalup4 W., L. Baird, C. Soderholm, D. L. Palmquist, R W. Hemken, D. Ottertry, R. Annexsted, B. Vecchiarelli, R. Harmon, A. Sinha, J. Linn, W. Hansen, F. Ehle, P. Schneider. and R. Eggert. 1987. Responses of dairy cows to somatotropin. J. Dairy Sci. 7O(Suppl. 1):176.(Abstr.) 8 Chalupa,W., B. Vccchiarelli, P.Schneider, and R. 0. Eggert 1986. Long-term responses of lactating cows to daily injection of recombinant somatotropin. J. Dajr Sci. 69(Suppl. l):lSl.(Absir.) 9 Eppard, P. J., D. E. Bauman, C.R. Cmtis, H. N. Erb,
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G. M, Lama, and M. J. m e t e r . 1987. Effect of 188-day treatment with somatotropin on health and reproductive performance of lactaw dairy cows. J. Dairy Sci. 70582. lOFronk, T. J.. C. J. Peel, D. E. Bauman, and R. C. Gorewit. 1983. Comparison of different palterns of exogenous growth hormone administration on milk production in Holstein cows. J. Anim. Sci. 57699. 1 Gibson, J. P., B. W. McBride, I. H. Burton, and R. G. Eggen. 1990. Effect on production haits of administration of rbST for up to three consecutive lactations. J. Dairy Sci. 73(Suppl. 1):158.(Abstr.) 2Huber. I. T., J. L. Sullivan, and S. Willman. 1990. Response of Holstein cows to biweekly sometribove (SB) injections for three. consecutive lactations. J. Dairy Sci. 73(Suppl. 1): 157.(Abstr.) 3MaChlin, L. J. 1973. Effect of growth hormone on milk production and feed utilization in dairy cows. J. Dairy Sci. 56:575. 4 Matthews, K. R., R. J. Harmon, B. E. Langlois, W. L. Crist, and R. W. Hemken. 1988. Use of latex teat dip with germicide during the prepartum period. J. Dairy Sci. 71:1940. 15 McBride, B. W., J. L. Burton, I. P. Gibson,J. H. Burton, and R. G. Egg&. 1990. Use of recombinant bovine somatotropin for up to two consecutive lactations on dairy production traits.J. Dairy Sci. 73:3248. 16Pee1, C. J., and D. E. Bauman. 1987. Somatotropin and lactation. J. Dairy Sci. 70:474. 17Pee.1, C. J.. T. J. Fb% D. E. Bauman, and R. C. Gorewit 1983. Effect of exogenous growth hormone in early and late lactation on lactational performance of dairy cows. J. Dairy Sci. 66:776. 18Richds, M. W., R P. Wettemann. and H. M. Schoenemann. 1989. Nutritional anestrus in beef cows: concentxations of glucose and nonesterified fatty acids in plasma and insulin in serum. J. Anim. Sci. 672354. 19 SAS@User’s Guide: Statistics. 1982. SAS Jnst., Inc., Gary, NC. 20SiIvia, W. J., and M. L. Taylor. 1989. Relationship between uterine secretion of prostaglandin F2a ind a d by oxytocin and endogenous concentrations of estradiol and progesterone at three stages of the bovine estrous cycle. J. Anim. Sci. 67:2347. 21Soderholm. C. G., D. E. Otterby, F. R. Eble, I. G. Linu, W. P. Himen, and R. J. Annexstad. 1986. Effects of diffmnt doses of recombinant bovine m matotropin (rbSTH) on milk production, body composition, and condition score in lactating cows. J. Dairy Sci. 69(Suppl. 1):152.(Abstr.) 22Spicer, L. J., W. B. Tucker, and G. D. A h . 1990. Insuljn-like growih factor-I in dairy cows: relationships among energy tdance., body condition,ovarian activity, and estrous behavior. J. Dairy Sci. 73:929. 23 West, J. W.,K.Bondari, and J. C. Johoson, Jr. 1990. Effects of bovine somatotropin on milk yield and composition, body weight, and condition score of Holstein and Jersey cows. J. Dairy Sci. 731062.