Recombinant Bovine Somatotropin with Lactating Cows Fed Diets Differing in Energy Density N. J. TESSMANN, T. R. DHIMAN, J. KLEINMANS, H. D. RADLOFF, and L. D. SATTER US Dalry Forage Research Center Agricultural Research Service, USDA and Department of Dalry Science University of Wisconsin Madison 53706 ABSTRACT
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. fujection 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 j3-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 fust lactation did not produce as much milk as controls when compared during the first 10 wk of their second lactation. (Key words: forage, grain, milk) Abbreviation key: BHB = ~-hydroxybutyrate, CTL = control group given buffered saline, PFFA = plasma free fatty acids. INTRODUCTION
A number of studies have shown that pituitary-derived bST can increase milk production and gross efficiency of milk production (2, 11, 12, 13, 15, 23). Most of the recent research with bST has dealt with testing the efficacy of recombinant bST. Bauman et al. (4) observed an increase in daily milk production of 23 to 41 % during the 188 d of bST injection. Soderholm et al. (25) reponed daily milk production increases of 12 to 25% due to bST administration for 38 wk. Administration of bST tends to increase gross feed efficiency while not affecting milk composition (3, 8, 16), and bST-treated cows tend to regain less BW during lactation (6, 25, 27). Questions about the response of cows to bST administration in different feeding situations and the comparative response in primiparous and multiparous cows need to be answered. The objective of this research was to study the response in primiparous and multiparous cows fed diets based on alfalfa silage and differing in energy content. MATERIALS AND METHODS
Experiment 1 Received November 2. 1990. Accepted February 19. 1991. 1991 I Dairy Sci 74:2633-2644
Thirty-two primiparous and 32 multiparous Holstein cows were assigned randomly at par2633
2634
TESSMANN ET AL.
TABLE 1. Week of lactation in which cows left experiment, number of cows, and reasons for leaving the experiment early. wk 39
R
P
wk 41
wk 40
R
P
R
P
wk 42
R
P
wk 43
R
wk 44
R
P
P
- - - - - - - - - - - (number of cows) - - - - - - - - - - Multiparous 1 CTL 1 bST 3CTL 3 bST
1
2
Primiparous 1 CTL 1 bST 3CTL 3 bST
2
1
2 2
lTreatment 1 = High energy diet. Treatment 3 = Medium energy diet. CTL = Control cows received buffered saline injection; bST = cows received bST injection. 2Reproduction; cows dried off to allow a 55-d dry period. 3Production; milk production less than 9.1 kg/d.
turition to one of two diets differing in energy content and to either a control (CTL) (buffered saline) or bST (20.6 mgld per cow reconstituted with saline; American Cyanamid Co., Princeton, NJ) injection groups. Eight cows from each dietary treatment group were assigned to each injection treatment. Cows in the two CTL groups were part of treatment groups one and three of a larger study (26). Experimental design, procedures, concentrate composition, sampling, and measurements were described by Tessmann et al. (26). Table 1 shows the number of cows dried off on any particular week and the reason for drying off early (reproduction or production). Composition of individual diets is in Table 2.
Table 3 shows the diet fed during each phase of lactation for each of the treatments. Eighteen different silages were fed during the course of the experiment. The average chemical composition for each silage for the period during which it was fed is in Table 4 of Tessmann et al. (26). Silages 2 through 19 in this table were used for this part of the experiment. Statistics were by general linear models procedure with a protected least squares means t test of SAS (24) on 305-d production, reproductive influence, health, body condition score, and DMI data. The experimental design was a randomized model with treatments applied in a 2 x 2 factorial arrangement.
TABLE 2. Composition of the five different total mixed diets fed during the experiment. 1 Diet
Alfalfa silage
High moisture ear com
38.2 58.2 48.2 68.2 88.2
42.0 26.6 40.2 24.8 9.4
Soybean meaI2
Dicalcium phosphate2
Trace-mineral salt1
1.1 1.1 1.1 1.1 1.1
.7 .7 .7 .7 .7
(%, DM basis)
1 3 6 8
10
18.0 13.4 9.8 5.2 .6
lVitamins supplemented (IU/d per cow): vitamin A, 52,000; vitamin D, 17,000; vitamin E, 17. 2Dicalcium phosphate. Guaranteed analysis: P not less than 18.5%, Ca not more than 23% and not less than 19%, F not more than .185%. 3Trace-minerai salt. Guaranteed analysis: salt, not more than 98.5%, not less than 96.0%; not less than .35% Zn; .2% Mn; .2% Fe; .03% Cu; .007% 1; and .005% Co.
Journal of Dairy Science Vol. 74, No.8, 1991
2635
BOVINE SOMATOTROPIN
TABLE 3. Diets! fed in each stage of lactation in each treatment to achieve desired protein and grain content Treatmen~
Cn. I bST 3Cn. 3 bST
Early, wk 1-12
Mid, Late, wk 13-26 wk 27-44 (Diet number)
1 1 3
6 6 8 8
8 8 10 10
3 ITable 2 shows diet composition. 2rreatment 1 = high energy diet. Treatment 3 = medium energy diet. CTL = Control cows received buffered saline injection; bST = cows received bST injection.
The model was Yijkl = I! + q + Tj + Bk + TBjk + CBik + CTij + CI'B ijk + Ejjkl where
between 1000 and 1200 h with a disposable syringe having an 18-gauge, 12.7-mm needle. Feed intake for individual cows was measured by recording daily feed offered and orts. Body weights were recorded once weekly after the morning milking. Dry matter digestibility of the diet was measured between wk 19 and 26 of lactation using Yb as a marker. Lanthanum was used as a marker to measure rumen retention time of forage as described by Combs (9). Blood samples from the tail artery or vein were collected during 2, 3, 4, 6, 8, 12, 14, 16, 18, 20, 22, 24, and 28 wk of lactation and analyzed for blood glucose and urea and plasma ~-hydroxybutyrate (BHB) and FFA (10). Net energy balances for the entire lactation were estimated using net energy intake (17) minus milk energy output (28) and energy spent for maintenance (17). Experiment 2
Yijkl
I!
q
Tj Bk TBjk CB ik CTij CTB ijk Ej,jkl
= observation
of cow I on bST treatment k on dietary treatment j in lactation i, = population mean, = effect of lactation i, = effect of dietary treatment j, = effect of the bST treatment k, = effect of the interaction between bST treatment k and dietary treatment j, = effect of the interaction between bST treatment k and lactation i, = effect of the interaction between dietary treatment j and lactation i, = effect of the interaction between bST treatment k and dietary treatment j and lactation i, and = experimental error.
Daily injections of saline or bST started at the beginning of wk 13 of lactation and continued through wk 43. Cows dried off before reaching 44 wk because of production or reproductive reasons as described by Tessmann et aI. (26) received injections through a week before they were off the experiment. Injections were given subcutaneously in the rump on alternating sides. The rump area to be injected was cleaned with ethanol before injection. Two milliliters of solution were injected once daily
Primiparous cows in Experiment 1 were observed into their next lactation to estimate treatment carry-over effects. Cows were fed a diet containing 48.2:50.0 forage:grain ratio, which was diet 2 from Experiment 1 in Tessmann et aI. (26). The four treatment groups had 8 cows each in Experiment 1, and 7 of the 8 were available for Experiment 2 in all but the medium energy bST groups, for which 5 cows were available. AU cows were fed the same diet and received no injections but were retained in their experimental groups for data analysis. Twelve different alfalfa silages were fed during the course of the experiment (silages 10 through 21); they are listed in Table 4 of Tessmann et aL (26). Data were analyzed statistically for 100wk milk production, milk composition, OM!, and BW by a general linear models procedure with a protected least squares means t test (24). The completely randomized model with treatments applied as a 2 x 2 factorial arrangement was Yijk
= I!
+ T i + Bj + TBij + Ejjk
where Yijk = observation of cow k on bST treatment j on dietary treatment i, I! = population mean, Ti = effect of treatment i, Journal of Dairy Science Vol. 74, No.8, 1991
2636
TESSMANN ET AL.
Bj = effect of bST treatment j, TBij = effect of the interaction between bST treatment j and dietary treatment i, and &jk = experimental error. Significance was declared at P < .05 unless otherwise noted. RESULTS AND DISCUSSION
Experiment 1
Milk, fat, and protein production for the first 12 wk of lactation, when no bST was administered, were analyzed by a randomized statistical model (24) as described by Tessmann et al. (26). There was no difference between CTL and bST designated groups within dietary treatments and within age groups. No difference was noted among dietary treatments within primiparous cows in wk-12 milk and fat production. Protein production was higher (P < .10) for high energy compared with medium energy treatment for primiparous cows. Multiparous cows fed high energy diets produced more milk (P < .15) and protein in the first 12 wk but did not differ in fat production. Significant differences between
bST and CfL cows within dietary treatments and age groups in Tables 4 and 5 can be considered increases (or decreases) due to bST administration in wk 13 through 43. Milk yield and composition for multiparous and primiparous cows are in Tables 4 and 5. Main effects of parity, energy density, and bST treatments on lactational measurements are in Table 6. Milk composition did not change due to bST administration, which supports results from earlier research (1, 4, 14, 25, 27). Both multiparous and primiparous cows in treatment 1 injected with bST had the highest milk, FCM, and cheese yields. Actual milk production (305-
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. fujection 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 j3-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 fust lactation did not produce as much milk as controls when compared during the first 10 wk of their second lactation. (Key words: forage, grain, milk) Abbreviation key: BHB = ~-hydroxybutyrate, CTL = control group given buffered saline, PFFA = plasma free fatty acids. INTRODUCTION
A number of studies have shown that pituitary-derived bST can increase milk production and gross efficiency of milk production (2, 11, 12, 13, 15, 23). Most of the recent research with bST has dealt with testing the efficacy of recombinant bST. Bauman et al. (4) observed an increase in daily milk production of 23 to 41 % during the 188 d of bST injection. Soderholm et al. (25) reponed daily milk production increases of 12 to 25% due to bST administration for 38 wk. Administration of bST tends to increase gross feed efficiency while not affecting milk composition (3, 8, 16), and bST-treated cows tend to regain less BW during lactation (6, 25, 27). Questions about the response of cows to bST administration in different feeding situations and the comparative response in primiparous and multiparous cows need to be answered. The objective of this research was to study the response in primiparous and multiparous cows fed diets based on alfalfa silage and differing in energy content. MATERIALS AND METHODS
Experiment 1 Received November 2. 1990. Accepted February 19. 1991. 1991 I Dairy Sci 74:2633-2644
Thirty-two primiparous and 32 multiparous Holstein cows were assigned randomly at par2633
2634
TESSMANN ET AL.
TABLE 1. Week of lactation in which cows left experiment, number of cows, and reasons for leaving the experiment early. wk 39
R
P
wk 41
wk 40
R
P
R
P
wk 42
R
P
wk 43
R
wk 44
R
P
P
- - - - - - - - - - - (number of cows) - - - - - - - - - - Multiparous 1 CTL 1 bST 3CTL 3 bST
1
2
Primiparous 1 CTL 1 bST 3CTL 3 bST
2
1
2 2
lTreatment 1 = High energy diet. Treatment 3 = Medium energy diet. CTL = Control cows received buffered saline injection; bST = cows received bST injection. 2Reproduction; cows dried off to allow a 55-d dry period. 3Production; milk production less than 9.1 kg/d.
turition to one of two diets differing in energy content and to either a control (CTL) (buffered saline) or bST (20.6 mgld per cow reconstituted with saline; American Cyanamid Co., Princeton, NJ) injection groups. Eight cows from each dietary treatment group were assigned to each injection treatment. Cows in the two CTL groups were part of treatment groups one and three of a larger study (26). Experimental design, procedures, concentrate composition, sampling, and measurements were described by Tessmann et al. (26). Table 1 shows the number of cows dried off on any particular week and the reason for drying off early (reproduction or production). Composition of individual diets is in Table 2.
Table 3 shows the diet fed during each phase of lactation for each of the treatments. Eighteen different silages were fed during the course of the experiment. The average chemical composition for each silage for the period during which it was fed is in Table 4 of Tessmann et al. (26). Silages 2 through 19 in this table were used for this part of the experiment. Statistics were by general linear models procedure with a protected least squares means t test of SAS (24) on 305-d production, reproductive influence, health, body condition score, and DMI data. The experimental design was a randomized model with treatments applied in a 2 x 2 factorial arrangement.
TABLE 2. Composition of the five different total mixed diets fed during the experiment. 1 Diet
Alfalfa silage
High moisture ear com
38.2 58.2 48.2 68.2 88.2
42.0 26.6 40.2 24.8 9.4
Soybean meaI2
Dicalcium phosphate2
Trace-mineral salt1
1.1 1.1 1.1 1.1 1.1
.7 .7 .7 .7 .7
(%, DM basis)
1 3 6 8
10
18.0 13.4 9.8 5.2 .6
lVitamins supplemented (IU/d per cow): vitamin A, 52,000; vitamin D, 17,000; vitamin E, 17. 2Dicalcium phosphate. Guaranteed analysis: P not less than 18.5%, Ca not more than 23% and not less than 19%, F not more than .185%. 3Trace-minerai salt. Guaranteed analysis: salt, not more than 98.5%, not less than 96.0%; not less than .35% Zn; .2% Mn; .2% Fe; .03% Cu; .007% 1; and .005% Co.
Journal of Dairy Science Vol. 74, No.8, 1991
2635
BOVINE SOMATOTROPIN
TABLE 3. Diets! fed in each stage of lactation in each treatment to achieve desired protein and grain content Treatmen~
Cn. I bST 3Cn. 3 bST
Early, wk 1-12
Mid, Late, wk 13-26 wk 27-44 (Diet number)
1 1 3
6 6 8 8
8 8 10 10
3 ITable 2 shows diet composition. 2rreatment 1 = high energy diet. Treatment 3 = medium energy diet. CTL = Control cows received buffered saline injection; bST = cows received bST injection.
The model was Yijkl = I! + q + Tj + Bk + TBjk + CBik + CTij + CI'B ijk + Ejjkl where
between 1000 and 1200 h with a disposable syringe having an 18-gauge, 12.7-mm needle. Feed intake for individual cows was measured by recording daily feed offered and orts. Body weights were recorded once weekly after the morning milking. Dry matter digestibility of the diet was measured between wk 19 and 26 of lactation using Yb as a marker. Lanthanum was used as a marker to measure rumen retention time of forage as described by Combs (9). Blood samples from the tail artery or vein were collected during 2, 3, 4, 6, 8, 12, 14, 16, 18, 20, 22, 24, and 28 wk of lactation and analyzed for blood glucose and urea and plasma ~-hydroxybutyrate (BHB) and FFA (10). Net energy balances for the entire lactation were estimated using net energy intake (17) minus milk energy output (28) and energy spent for maintenance (17). Experiment 2
Yijkl
I!
q
Tj Bk TBjk CB ik CTij CTB ijk Ej,jkl
= observation
of cow I on bST treatment k on dietary treatment j in lactation i, = population mean, = effect of lactation i, = effect of dietary treatment j, = effect of the bST treatment k, = effect of the interaction between bST treatment k and dietary treatment j, = effect of the interaction between bST treatment k and lactation i, = effect of the interaction between dietary treatment j and lactation i, = effect of the interaction between bST treatment k and dietary treatment j and lactation i, and = experimental error.
Daily injections of saline or bST started at the beginning of wk 13 of lactation and continued through wk 43. Cows dried off before reaching 44 wk because of production or reproductive reasons as described by Tessmann et aI. (26) received injections through a week before they were off the experiment. Injections were given subcutaneously in the rump on alternating sides. The rump area to be injected was cleaned with ethanol before injection. Two milliliters of solution were injected once daily
Primiparous cows in Experiment 1 were observed into their next lactation to estimate treatment carry-over effects. Cows were fed a diet containing 48.2:50.0 forage:grain ratio, which was diet 2 from Experiment 1 in Tessmann et aI. (26). The four treatment groups had 8 cows each in Experiment 1, and 7 of the 8 were available for Experiment 2 in all but the medium energy bST groups, for which 5 cows were available. AU cows were fed the same diet and received no injections but were retained in their experimental groups for data analysis. Twelve different alfalfa silages were fed during the course of the experiment (silages 10 through 21); they are listed in Table 4 of Tessmann et aL (26). Data were analyzed statistically for 100wk milk production, milk composition, OM!, and BW by a general linear models procedure with a protected least squares means t test (24). The completely randomized model with treatments applied as a 2 x 2 factorial arrangement was Yijk
= I!
+ T i + Bj + TBij + Ejjk
where Yijk = observation of cow k on bST treatment j on dietary treatment i, I! = population mean, Ti = effect of treatment i, Journal of Dairy Science Vol. 74, No.8, 1991
2636
TESSMANN ET AL.
Bj = effect of bST treatment j, TBij = effect of the interaction between bST treatment j and dietary treatment i, and &jk = experimental error. Significance was declared at P < .05 unless otherwise noted. RESULTS AND DISCUSSION
Experiment 1
Milk, fat, and protein production for the first 12 wk of lactation, when no bST was administered, were analyzed by a randomized statistical model (24) as described by Tessmann et al. (26). There was no difference between CTL and bST designated groups within dietary treatments and within age groups. No difference was noted among dietary treatments within primiparous cows in wk-12 milk and fat production. Protein production was higher (P < .10) for high energy compared with medium energy treatment for primiparous cows. Multiparous cows fed high energy diets produced more milk (P < .15) and protein in the first 12 wk but did not differ in fat production. Significant differences between
bST and CfL cows within dietary treatments and age groups in Tables 4 and 5 can be considered increases (or decreases) due to bST administration in wk 13 through 43. Milk yield and composition for multiparous and primiparous cows are in Tables 4 and 5. Main effects of parity, energy density, and bST treatments on lactational measurements are in Table 6. Milk composition did not change due to bST administration, which supports results from earlier research (1, 4, 14, 25, 27). Both multiparous and primiparous cows in treatment 1 injected with bST had the highest milk, FCM, and cheese yields. Actual milk production (305-
