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Effects of Altering Milk Production and Composition by Feeding on Multiple Component Milk Pricing Systems1
Effects of Altering Milk Production and Composition by Feeding on Multiple Component Milk Pricing Systems1 R. G. C R A G L E , ; M. R. M U R P H Y , 2 S. W. W I L L I A M S , 3 and J. H, C L A R K 2 University of Illinois Urbana 61801
ABSTRACT
Data representing 1105 cows were obtained from published scientific reports to estimate the extent to which changes in feeding may affect the composition of milk and the production of milk protein and milk fat. Changes in milk pricing systems were also related to dairy cattle feeding practices that dairy producers may profitably implement. Regression equations were derived to estimate the transfer of gross energy in feed and gross energy in crude protein of feed into milk fat and milk protein. Feeding rations that contained 59% concentrate increased dry matter and crude protein intakes compared to feeding rations that contained 49% concentrate. Feeding higher energy rations also resulted in increased production of milk, milk fat, and milk protein and returned a greater profit over feed costs when milk was priced using each of four milk pricing systems. An increase in milk production, rather than a change in composition of milk components, accounted for most of the economic gain. I N T R O D U C T I ON
F o r a number of years, marketing of milk in the United States has been oriented to the fluid milk market. Currently, a minimum standard of 11.5% total solids and 8.25% solids-not-fat (SNF) is required by state regulations in most markets for Class I whole milk, with the notable exception of California, where 12.2%
Received April 12, 1985. 1Supported in part by the Illinois Agricultural Experiment Station. 2 Department of Dairy Science. 3Department of Agricultural Economics. 1986 J Dairy Sci 69:282-289
total solids and 8.8% SNF is required (24). In most markets, a differential is paid for milk fat. It is added to the base price paid for milk that contains more than 3.5% fat but subtracted from the base price if milk contains less than 3.5% fat. This differential paid for milk fat represents a one-component marketing system that has been replaced by a two-component marketing system in some locations. The twocomponent system includes differential payments for milk protein as well as for milk fat. Differential payment based on the SNF content of milk also has been used rather than protein content. The development of a price differential for the protein component of milk is driven by increasing consumer demand for hard cheese. Hard cheese is cheese that contains 38 to 42% moisture. Commercial production of hard cheese in the United States increased 23% between 1976 and 1983 (3). Approximately 30% of the milk produced in the United States in 1983 was used for the manufacture of hard cheese (3). As a result of the focus on end products of milk production such as cheese, there is an increasing demand among milk producers to receive economic equity for the production of components in milk. Currently there is concern about how producers will be compensated for production of milk protein. If a two-component milk pricing system, based on either protein and fat, or SNF and fat, is adopted on a wide scale, dairy scientists and milk producers will need to develop management, feeding, and breeding systems that will allow production to respond to the economic signals generated by the market. One of the major ways in which producers may respond almost immediately is through changes in feeding. The objectives of this study were 1) to estimate the extent to which changes in feeding may affect the composition of milk and the production of milk protein and milk fat, and 2) to relate market prices of milk protein
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MATERIALS AND METHODS
To determine the effects of feeding on milk production and milk composition, data from 27 reports (1, 2, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 3 3 ) w e r e r e v i e w e d and summarized. These reports were selected to provide complete data sets that included milk production, protein, fat and lactose percentages in milk, and dry matter and crude protein intakes. F o r 17 of these reports lactose was calculated by use of the equation: lactose percentage = SNF percentage minus protein percentage minus mineral (ash) percentage. An average of .71% was used for the mineral content of milk (23). Lactose was reported in two publications; and in three reports where neither SNF nor lactose concentrations were provided, an average of 4.75% was used to estimate the lactose concentration in milk. Reports were selected that used feeding and management conditions common to those practiced on dairy farms in the United States. Cows used in the selected studies were generally reported to be healthy, and problems associated with herd health appeared to be evenly distributed among treatments. All data were normalized to a daily basis. After analysis of data sets from the 27 reports, data were grouped according to stage o f lactation o f cows at the time the information was collected. Data were grouped as follows: 1) experiments started with cows at parturition but not continued for a complete lactation; 2) experiments started with cows near the peak of lactation; and 3) experiments started with cows at parturition and continued for a complete lactation. All studies published prior to 1971 were in group 2. The production and management practices of the pre-1971 reports did not, on average, compare favorably to present standards; therefore, data from four of these reports (1, 11, 12, 3 1 ) w e r e removed from the study and one 1975 report was excluded as well (25). Cows included in group 3, fed rations with 49% concentrate, averaged 6405 kg of milk in 305 d; cows fed rations that averaged 59% concentrate averaged 7503 kg of milk in 305 d.
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A total of 1105 cows from 22 trials representing 97 dietary treatments were included in the revised data set. Of these, 1080 were Holstein, 15 were Jersey (27), and 10 were Ayrshire (28). Parity varied and some cows were in their first lactation. Cows were milked twice daily except in two trials in which they were milked three times daily (7, 8). Group 1 included data for 228 cows from seven trials (8, 10, 13, 15, 16, 28, 32). Data collection periods averaged 17 wk and ranged from 4 to 40 wk. Group 2 included data for 392 cows from nine trials (2, 9, 17, 21, 22, 26, 27, 29, 33), and data were collected for an average of 12.5 wk and ranged from 10 to 16 wk. Group 3 included 485 cows from six trials (4, 6, 7, 14, 20, 30). These data were collected for a minimum of one 305-d lactation and a maximum of three 305-d lactations. Calculations were made to relate intakes of gross energy in feed and the gross energy present in crude protein of feed to output of gross energy in milk fat and milk protein. Calculations were made using a linear model (y = a + bx) in which the energy in milk fat and milk protein was expressed as a function of total gross energT intake in feed or in crude protein of feed for all cows or for each of the three groups of cows. Gross energy of feed and milk components expressed in megacalories (Mcal) was estimated as follows: milk protein, 5.85 Mcal/kg; milk fat, 9.23 Mcal/kg; milk lactose, 3.70 Mcal/kg (19); crude protein in feed, 5.85 Mcal/kg; and nonprotein dry matter, 4.40 Mcal/ kg (2, 15, 16). Corrections were not made for diets that included supplemental nonprotein nitrogen, but inflation of total dietary gross energy was estimated to have been 3.2 (9), 3.8 (10), .5 (20), and .9% (30). Economic input-output data were calculated based on four systems of marketing milk and current feed prices. RESULTS A N D DISCUSSION
A summary of data relating dry matter, gross energy, and crude protein intakes to the production of milk and milk components for all cows is presented in Table 1. Components of milk and feed were expressed as megacalories of gross energy produced or consumed per day so that efficiency of conversion of gross energy in feed to milk constituents could be calculated on a common basis. Journal of Dairy Science Vol. 69, No. 1, 1986
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TABLE 1. Summary of data relating dry matter, gross energy, and crude protein intakes to the production of milk and milk components (1105 cows). SD Milk, kg/d Milk protein, kg/d Milk fat, kg/d Milk lactose, kg/d
24.93 .786 .817 1.179
4.76 .146 .164 .256
Milk gross energy, Mcal/d
16.50
3.14
Dry matter intake, kg/d Crude protein intake, kg/d
17.61 2.69
2.71 .55
Energy intake, Mcal/d Energy intake from crude protein, Mcal/d
77.48 15.75
11.91 3.21
Conversion of gross energy in feed to gross energy in milk Conversion of crude protein in feed to crude protein in milk Milk protein, % Milk fat, % Crude protein in feed, %
In an attempt to refine the data, 36 withinexperiment comparisons were selected from the 97 experimental treatments. Comparisons consisted of rations that averaged 59 or 49% concentrate. Average differences in dry matter intakes, crude protein intakes, feed protein percentages, and concentrate percentages in the rations are in Table 2 for the 36 treatment comparisons among all cows and for treatment comparisons for cows divided into groups according to stage of lactation. Cows fed 59% concentrate in the ration produced an average of 11% more milk, 13% more milk protein, 3% more milk fat, and 11% more milk lactose than cows fed rations that contained 49% concentrate (Table 3). Eighty-five percent of the increased milk protein yield was attributed to increased milk volume and only 15% was attributed to increased protein percentage of the milk. Cows fed rations that contained 59% concentrate consumed an average of 7% more dry matter and 19% more crude protein than cows fed rations that contained 49% concentrate. Similar increases were obtained for the production of milk and milk components and the intakes of dry matter and crude protein when cows were grouped by stage of lactation. The largest increase in these parameters occurred for cows in group 3, but these data were also the most variable. Because of the variation in these Journal of Dairy Science Vol. 69, No. 1, 1986
.216 .299 3.16 3.29 15.25
.046 .063 .21
.34 1.70
data, there were no significant differences between rations that contained 49 or 59% concentrate for any of these comparisons. Many reports discuss the influence of feeding on the production of milk fat and milk protein by dairy cows. In general, feeding a diet of 60% concentrate and 40% forage, balanced to meet the cow's nutrient requirements, results in the greatest energy intake, milk production, and energy output in milk. Feeding more than 60% concentrate in the diet usually lowers milk fat percentage and yield and may, under certain conditions, severely depress milk fat yield. Under certain conditions, feeding large amounts of concentrate may result in a small increase in milk protein percentage and yield. Emery (5) reported that milk protein was increased .015 percentage units for each megacalorie of additional net energy intake, from 9 to 40 Mcal. Milk protein also increased .02 percentage units for each one percentage unit increase in dietary crude protein when dietary protein was increased from 9 to 17%. Oldham (18) reviewed protein-energy interrelationships in dairy cows and pointed out the importance of adequate protein intake for maximizing digestibility and dry matter intake. He further showed that interrelationships between protein and energy yielding nutrients, both within the rurnen and within the ruminant's tissues, can
TABLE 2. Average m i l k p r o d u c t i o n and composition, dry m a t t e r (DM) intakes, and differences between t r e a t m e n t comparisons for cows fed 59% c o n c e n t r a t e or 49% co ncentra te rations. Feed Milk Production (kg/d) All cows (36 t r e a t m e n t comparisons) H1
~a
25.9
L~
23.5
D3
2.4
SD
5.0 4.7 2.0
DM
Protein
Fat
intake
(kg/d) SD
(%)
SD
(kg/d) SD
(%)
.82 .73 ,09
3,19 3.12 .06
,24 .20 .12
.82 .80 .02
3.17 .33 3.42 .30 - . 2 5 .26
,15 ,14 .08
.18 .18 .10
SD
(kg/d)
17.7 16.7 .9
SD
2.7 2.9
1.7
Crude protein i n t a k e
Concentrate
(kg/d) SD
(%DM)
SD
(%Diet) SD
2.8 2.4 .4
16.1 14.6 1.4
1.3 1.8 1.9
59.1 49.2 9.8
.6 .5 .5
13.1 15.6 13.9 ©
Group 1 cows (12 t r e a t m e n t comparisons) H L D
29.3 27.0 2.3
3.9 4.4 1.2
.94 .85 .09
,11
3,23
,12
3,16
.06
Group 2 cows (15 t r e a t m e n t comparisons) H L D
24.0 22.3 1.7
5,6 4.3 2.2
.74 .68 .07
Group 3 cows (9 t r e a t m e n t comparisons) H L D
24.6 21.0 3.6
2.9 3.4 2.2
.80 ,67 .13
.06
,15 ,14 ,11
.94 .95 -.01
.15 .17 .09
3,23 .38 3.54 .28 - . 3 0 .27
16.3 15,5 .8
2.9 3.0 1.3
2.6 2.5 .1
.6 .6 .2
15.9 15.8 ,2
1.1 1.2 .2
67.7 57.1 10.6
9.7 14.4 10.5
,15 .12 .07
3.13 3.05 .07
.32 ,25 .12
.73 .73 .00
.17 .13 .10
3.07 .33 3,32 .35 - . 2 5 .30
18.6 18.0 .6
2.7 2.4 1.7
3.1 2,5 .6
.6 .4 .5
16.4 13.9 2.5
1.5 1.1 2.2
53.2 42.9 10.4
12.2 13.2 18.4
.10 .12 .09
3.24 3.20 .05
.15 .14 .15
.80 .72 .08
.13 .14 .08
2.25 .23 3.42 .20 - . 1 7 .15
18.0 16.3 1.7
1.5 3.0 2.2
2.8 2.4 .5
.4 ,7 ,4
15.7 14.3 1,4
1.3 2.6 1.7
56,8 49.4 7.4
13,6 17.9 8.5
,.-I
~a
on Z 9
0o ox
1 Ration c o n t a i n e d 59% concentrate. 2 R a t i o n contained 49% concentrate. 3Difference for cows fed 59% concentrate minus 49% c o n c e n t r a t e rations. Differences were calculated i n d e p e n d e n t l y ; therefore, small discrepancies exist due to rounding.
tJ 0o
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TABLE 3. Percentage increase for milk production, milk components, and feed intakes of cows fed 59% concentrate rations compared with cows fed 49% concentrate rations. Parameter
All cows
Group 11
Group 2~
Group 33
(% increase) SD
SD
.~
SD
.~
SD
Milk volume Milk protein Milk fat Milk lactose Dry matter intake Crude protein intake
11 13 3 11 7 19
10 13 13 11 12 22
9 11 0 9 6 7
5 7 9 7 8 8
7 10 0 7 4 23
8 10 13 9 9 23
18 21 13 19 13 27
15 2O 16 16 17 29
Percentage increase in crude protein content of feed dry matter
44
91
17
17
151
120
35
72
Number of cows Numb er of comparisons
752 36
194 12
306 15
252 9
1Experiments started with cows at parturition but not continued for a complete lactation. 2 Experiments started with cows near the peak of lactation. 3 Experiments started with cows at parturition and continued for a complete lactation.
have large effects on the overall conversion of dietary nutrients to milk. Regression equations were calculated f r o m data summarized in Tables 1 and 2 to estimate t h e transfer o f gross energy f r o m feed or f r o m crude protein in feed to milk fat and milk protein (Table 4). Equations calculated f r o m data for cows in each of groups 1, 2, and 3 resulted in less variable estimates of the transfer of gross energy than did equations calculated using p o o l e d data f r o m all cows. This probably occurred because grouping cows by stage of lactation r e m o v e d s o m e of the variation caused by energy mobilization from, or deposition to, b o d y tissues. F u r t h e r m o r e , changes in a m o u n t and types of feeds consumed at various stages of lactation alter ruminal f e r m e n t a t i o n and a p p a r e n t digestibility of ration ingredients, which w o u l d affect the q u a n t i t y of gross energy in feed that is transferred to milk and milk components. I n c o m e above feed costs was calculated for cows fed either 59% concentrate or 49% concentrate rations based on f o u r systems of pricing milk and current feed prices (Table 5). F o u r systems of pricing milk were: 1) base price plus fat differential, 2) base price plus fat differential plus protein differential, 3 ) b a s e Journal of Dairy Science Vol. 69, No. 1, 1986
price plus fat differential plus SNF differential, and 4) end p r o d u c t pricing for cheese. End p r o d u c t pricing for cheese returns m o n e y to the producer based on the m a r k e t price of cheese and the yield of cheese f r o m milk. Daily inc o m e f r o m the sale of milk p r o d u c e d by all cows fed rations t h a t contained either 59% concentrate or 49% c o n c e n t r a t e was not altered when a price differential was included for either protein or SNF (systems 2 and 3) c o m p a r e d with the sale of milk based on o n l y a price differential for fat (system 1). The greater q u a n t i t y of milk p r o d u c e d by cows fed 59% c o n c e n t r a t e in their rations increased daily inc o m e f r o m milk $.42 and daily income over feed costs by $.15 c o m p a r e d with cows fed 49% concentrate in the rations w h e n milk pricing systems 1, 2, and 3 were used. When system 4 for pricing milk was used, additional i n c o m e f r o m milk and income over feed costs was $.45 and $.18/d greater, respectively, for cows fed rations that contained 59% concentrate than for cows fed rations that contained 49% concentrate. Therefore, w h e n cows fed 59% c o n c e n t r a t e w e r e c o m p a r e d w i t h cows fed rations that contained 49% concentrate, pricing milk using system 4 resulted in $.03/d m o r e i n c o m e over feed costs for cows fed 59% con-
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TABLE 4. Regression equations relating the conversion of gross energy in feed and gross energy in feed protein to energy in protein and fat of milk. 1,2 Slope All cows
MPE = MPE = MFE = MFE =
2.5907 2.5662 4.4924 4.7419
+ .1273 + .0262 + .1935 + .0361
Group 13 cows
MPE = MPE = MFE = MFE =
2.9135 2.5457 4.9864 4.9631
+ + + +
Group 24 cows
MPE MPE MFE MFE
Group 3 s cows
MPE= MPE= MFE = MFE=
r:
PE TE PE TE
P<.0001 p<.o002 p<.o001 P<.0049
.2285 .1332 .1676 .0804
.1593 PE .0389TE .2489 PE .0531 TE
P<.O001 P<.O001 P<.O006 P<.0058
.5805 .5338 .3813 .2670
= 1.5681+.1696PE = -.0353 + .0539 TE = 3.4185 + .2244 PE = .7529 + .0779 TE
P<.O001 P<.O001 P<.O018 P<.O001
.3695 .4983 .2102 .3390
P<.O006 P<.O041 P<.O002 P<.O031
.3955 .2959 .4512 .3115
2.4923+.1157PE 1.5234+.0354TE 3.6077 + .2237 PE 1.9434+ .0658TE
MPE = Gross energy in milk protein, PE = gross energy in feed protein, MFE = gross energy in milk fat, and TE = gross energy in feed. 2 The MPE, MFE, PE, and TE are all expressed in megacalories. 3 Experiments started with cows at parturition but not continued for a complete lactation. 4 Experiments started with cows near the peak of lactation. s Experiments started with cows at parturition and continued for a complete lactation.
c e n t r a t e in t h e i r rations t h a n did using s y s t e m s 1, 2, o r 3. F e e d i n g 59% c o n c e n t r a t e in t h e ration o f cows in g r o u p 3 increased milk yield m o r e t h a n f e e d i n g 49% c o n c e n t r a t e in t h e ration. T h e additional milk p r o d u c e d increased i n c o m e f r o m milk $.84 to $ 1 . 0 5 / d a n d i n c o m e over f e e d c o s t $.46 t o $ . 6 7 / d d e p e n d i n g o n t h e pricing s y s t e m used t o calculate t h e value o f milk (Table 5). Largest increases in i n c o m e f r o m milk and f r o m i n c o m e over f e e d cost w e r e o b t a i n e d w h e n t h e price of milk was calculated b a s e d o n e n d p r o d u c t pricing for cheese (system 4). Pricing milk based o n s y s t e m 2 ( p r o t e i n differential i n c l u d e d ) also increased t h e value o f milk versus using fat differential or fat d i f f e r e n t i a l plus S N F differential. When each o f t h e pricing s y s t e m s f o r milk was used, f e e d i n g cows a p p r o x i m a t e l y 60% c o n c e n t r a t e in t h e r a t i o n r e s u l t e d in greater e c o n o m i c r e t u r n over feed costs t h a n f e e d i n g less c o n c e n t r a t e . C u r r e n t l y a n u m b e r o f milk
m a r k e t i n g cooperatives are suggesting t h a t producers be paid a p r e m i u m f o r their milk based o n its SNF c o n t e n t . However, E r n s t r o m (personal c o m m u n i c a t i o n , 1984) has p o i n t e d o u t t h a t t h e p r o t e i n c o n t e n t o f t h e SNF c o m p o n e n t o f milk m a y vary b e t w e e n 32 and 42%. T h e yield of cheese f r o m milk is d i r e c t l y related t o its p r o t e i n (casein) c o n t e n t . T h e r e f o r e , p a y m e n t f o r milk o n its S N F c o n t e n t m a y n o t p r o v i d e e q u i t y for milk p r o t e i n p r o d u c t i o n because milk p r o t e i n is t h e p r i m a r y c o n t r i b u t o r t o changes in t h e p e r c e n t a g e o f SNF in milk, w h e r e a s lactose a n d mineral p e r c e n t a g e s r e m a i n relatively c o n s t a n t . However, e q u i t y can be achieved for t h e p r o d u c t i o n o f milk p r o t e i n t h r o u g h p a y m e n t based o n S N F c o n t e n t if the a d d e d p r e m i u m is paid for SNF c o n t e n t s above 5.40%, w h i c h r e p r e s e n t s t h e average concent r a t i o n o f lactose and mineral in milk. Pricing milk o n a p r o t e i n basis s t a r t i n g w i t h 0% o r S N F s t a r t i n g w i t h a p p r o x i m a t e l y 5.40% and p a y i n g t h e s a m e rate p e r p o i n t o f increase will result in Journal of Dairy Science Vol. 69, No. 1, 1986
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TABLE 5. Daily income above feed costs based on method of pricing milk for cows fed rations that contained 59 or 49% concentrate. Economic input-output data calculated from within-report comparisons of daily production and feed intakes for cows fed rations that contained 59 or 49% concentrate. Method of pricing milk 1
Plan
Base + fat differential (1)
Base + fat differential + protein differential (2)
Base + fat differential + SNF 2 differential (3)
End product priced for cheese (4)
All cows, 36 treatment comparisons 59% Concentrate rations 49% Concentrate rations Additional income from milk Cost of extra feed 3 Income over feed costs
$6.87 6.45 .42 .27 .15
$6.87 6.45 .42 .27 .15
$6.87 6.45 .42 .27 .15
$7.43 6.98 .45 .27 .18
Group 3 cows, 4 9 treatment comparisons 59% Concentrate rations 49% Concentrate rations Additional income from milk Cost of extra feed 3 Income over feed costs
6.60 5.76 .84 .38 .46
6.63 5.76 .87 .38 .49
6.60 5.76 .84 .38 .46
7.21 6.16 1.05 .38 .67
1Base price = $12.60/45.4 kg; fat differential = $. 17/point with a 3.5% standard; protein differential = $. 13/ point above 3.2%; SNF differential = $.10 above 8.75%; end product pricing= $1.40/.454 kg for 40% moisture cheese. 2 SNF = Solids-not-fat. 3The cost of extra feed was calculated using the following assumptions: soybean meal, $12/45.4 kg (90% dry matter and 44% protein) and corn grain, $7.00/45.4 kg (85.5% dry matter). 4 Experiments started with cows at parturition and continued for a complete lactation.
a b o u t t h e same e c o n o m i c r e t u r n a b o v e f e e d costs f o r p r o d u c t i o n o f p r o t e i n . Alternatively, m i d p o i n t s of 3.2% milk p r o t e i n or 8.60% milk SNF can be u s e d as a starting p o i n t f o r p a y i n g a differential f o r these milk c o m p o n e n t s t o achieve p r o t e i n p a y m e n t e q u i t y b a s e d on a premium and debit system. As m o r e is learned a b o u t t h e cost o f transferring milk c o m p o n e n t s i n t o milk p r o d u c t s c o n s u m e d b y t h e public a n d h o w c o m p o n e n t pricing will a f f e c t r e t u r n s t o t h e p r o d u c e r and processor, changes will o c c u r in milk pricing systems. T h e s e changes should r e f l e c t e q u i t a b l e p a y m e n t t o t h e p r o d u c e r based o n t h e c o m p o n e n t s in milk t h a t are u s e d f o r p r o d u c i n g products c o n s u m e d b y t h e public. REFERENCES
1 Bishop, S. E., J. K. Loosli, G. W. Trimberger, and K. L. Turk. 1963. Effects of pelleting and varying Journal of Dairy Science Vol. 69, No. 1, 1986
grain intakes on milk yield and composition. J. Dairy Sci. 46:22. 2 Blair, T., D. A. Christensen, and J. G. Manns. 1974. Performance of lactating dairy cows fed complete pelleted diets based on wheat straw, barley and wheat. Can. J. Anim. Sci. 54:347. 3 Dairy Outlook and Situation. 1984. US Dep. Agric. DS-396, Mar. 4 Edwards, J. S., E. E. Bartley, and A. D. Dayton. 1980. Effects of dietary protein concentration on lactating cows. J. Dairy Sci. 63:243. 5 Emery, R. S. 1978. Feeding for increased milk protein. J. Dairy Sci. 61:825. 6 Gardner, R. W., and R. L. Park. 1973. Protein requirements of cows fed high concentrate rations. J. Dairy Sci. 56:390. 7 Gordin, S., R. Volcani, and Y. Birk. 1971. The effects of nutritional level on milk yield and milk composition in cows and heifers. J. Dairy Res. 38: 287. 8 Gordin, S., R. Volcani, and Y. Birk. 1971. The effect of varying ratios of roughage to concentrate on composition and yield of cow's milk. J. Dairy Res. 38:295.
OUR INDUSTRY TODAY 9 Heinrichs, A. J., and H. R. Conrad. 1984. Fermentation characteristics and feedingvalue o f ammoniatreated corn silage. J. Dairy Sci. 67:82. 10 Hernandez-Urdaneta, A., C. E. Coppock, R. E. McDowell, D. Gianola, and N. E. Smith. 1976. Changes in forage-concentrate ratio of complete feeds for dairy c o w s J. Dairy Sci. 59:695. 11 Holmes, W., G. W. Arnold, a n d A . L. Provan. 1960. Bulk feeds for milk production. I. The influence o f level of concentrate feeding in addition to silage and hay on milk yield and milk composition. J. Dairy Res. 27 : 191. 12 Holmes, W., R. Waite, D. S. MacLusky, and J. N. Watson. 1956. Winter feeding o f dairy cows. I. The influence of level and source of protein and of the level of energy in the feed on milk yield and composition. J. Dairy Res. 23:1. 13 Kincaid, R. L., and J. D. Cronrath. 1982. Milk yield and metabolic meamres o f cows fed grain free choice during early lactation. J. Dairy Sci. 65: 740. 14 Lamb, R. C., G. E. Stoddard, C. H. Mickelson, M. J. Anderson, and D. R. Waldo. 1974. Response to concentrates containing two percents o f protein fed at four rates for complete lactations. J. Dairy Sd. 57:811. 15 Lodge, G. A., L. J. Fisher, and J. R. Lessard. 1975. Influence of prepartum feed intake on performance o f cows fed ad libitum during lactation. J. Dairy Sci. 58:696. 16 MacGregor, C. A., M. R. Stokes, W. H. Hoover, H. A. Leonard, L. L. Junkins, Jr., C. J. Sniffen, and R. W. Mailman. 1983. Effect of dietary concentration o f total nonstructural carbohydrate on energy and nitrogen metabolism and milk production of dairy cows. J. Dairy Sci. 66:39. 17 Macleod, G. K., D. G. Grieve, and I. McMillan. 1983. Performance of first lactation dairy cows fed complete rations of several ratios of forage to concentrate. J. Dairy Sci. 66:1668. 18 Oldham, J. D. 1984. Protein-energy interrelationships in dairy cows. J. Dairy Sci. 67:1090. 19 Opstvedt, J., and M. Ronning. 1967. Effect upon lipid metabolism of feeding alfalfa hay or concentrate ad libitum as the sole feed for milking cows. J. Dairy ScL 50:345. 20 Papas, A. M., S. R. Ames, R. M. Cook, C. J. Sniffen, C. E. Polan, and L. Chase. 1984. Production responses of dairy cows fed diets supplemented with ammonium salts o f iso C-4 and C-5 acids. J. Dairy Sci. 67:276. 21 Rock, C. G., C. E. Polan, W. M. Etgen, and C. N. Miller. 1974. Varying dietary fiber for lactating
22 23
24
25
26
27
28
29
30
31 32
33
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cows fed corn and barley silages. J. Dairy Sci. 57: 1474. Staples, C. R., C. L. Davis, G. C. McCoy, and J. H. Clark. 1984. Feeding value o f wet corn gluten feed for lactating dairy cows. J. Dairy Sci. 67:1214. Tyrrell, H. F., and J. T. Reid. 1965. Prediction o f the energy value of cow's milk. J. Dairy Sci. 48: 1215. United States Department of Agriculture. 1980. Federal and state standards for the composition o f milk products. Agric. Handbook No. 51, Food Safety Qual. Serv., Washington, DC. Van Horn, H. H., S. P. Marshall, C. J. Wilcox, P. F. Randel, and J. M. Wing. 1975. Complete rations for dairy cattle. III. Evaluation of protein percent and quality, and citrus plus-corn substitutions. J. Dairy Sci. 58:1101. Van Horn, H. H., E. A. Olaloku, J. R. Flores, S. P. Marshall, and K. C. Bachman. 1976. Complete rations for dairy cattle. VI. Percent protein required with soybean meal supplementation o f lowfiber rations for lactating dairy cows. J. Dairy Sci. 59:902. Van Horn, H. H., C. A. Zometa, C. J. Wilcox, S. P. Marshall, and B. Harris, Jr. 1979. Complete rations for dairy cattle. VIII. Effect of percent and source o f protein on milk yield and ration digestibility. J. Dairy Sci. 62:1086. Varga, G. A., E. M. Meisterling, R. A. Dailey, and W. H. Hoover. 1984. Effect of low and high fill diets on dry matter intake, milk production and reproductive performance during early lactation. J. Dairy Sci. 67:1240. Whiting, F. M., W. H. Brown, and J. W. Snail. 1976. Coarse barley straw in dairy rations containing alfalfa hay cubes. J. Dairy Sci. 59:764. Wohlt, J. E., and J. H. Clark. 1978. Nutritional value of urea versus preformed protein for ruminants. I. Lactation of dairy cows fed corn based diets containing supplemental nitrogen from urea and/or soybean meal. J. Dairy Sci. 61:902. Yousef, I. M., J. T. Huber, and R. S. Emery. 1970. Milk protein synthesis as affected by high-grain, low-fiber rations. J. Dairy Sci. 53:734. Zanartu, D., C. E. Polan, L. E. Ferreri, and M. L. McGilliard. 1983. Effect o f stage o f lactation and varying available energy intake on milk production, milk composition and subsequent tissue enzymic activity. J. Dairy Sci. 66:1644. Zeremski, D., H. H. Van Horn, A. D. McGilliard, and N. L. Jacobson. 1965. Effect o f the net energy concentration of total ration on milk production and composition. J. Dairy Sci. 48:1467.
Journal of Dairy Science Vol. 69, No. 1, 1986
ABSTRACT
Data representing 1105 cows were obtained from published scientific reports to estimate the extent to which changes in feeding may affect the composition of milk and the production of milk protein and milk fat. Changes in milk pricing systems were also related to dairy cattle feeding practices that dairy producers may profitably implement. Regression equations were derived to estimate the transfer of gross energy in feed and gross energy in crude protein of feed into milk fat and milk protein. Feeding rations that contained 59% concentrate increased dry matter and crude protein intakes compared to feeding rations that contained 49% concentrate. Feeding higher energy rations also resulted in increased production of milk, milk fat, and milk protein and returned a greater profit over feed costs when milk was priced using each of four milk pricing systems. An increase in milk production, rather than a change in composition of milk components, accounted for most of the economic gain. I N T R O D U C T I ON
F o r a number of years, marketing of milk in the United States has been oriented to the fluid milk market. Currently, a minimum standard of 11.5% total solids and 8.25% solids-not-fat (SNF) is required by state regulations in most markets for Class I whole milk, with the notable exception of California, where 12.2%
Received April 12, 1985. 1Supported in part by the Illinois Agricultural Experiment Station. 2 Department of Dairy Science. 3Department of Agricultural Economics. 1986 J Dairy Sci 69:282-289
total solids and 8.8% SNF is required (24). In most markets, a differential is paid for milk fat. It is added to the base price paid for milk that contains more than 3.5% fat but subtracted from the base price if milk contains less than 3.5% fat. This differential paid for milk fat represents a one-component marketing system that has been replaced by a two-component marketing system in some locations. The twocomponent system includes differential payments for milk protein as well as for milk fat. Differential payment based on the SNF content of milk also has been used rather than protein content. The development of a price differential for the protein component of milk is driven by increasing consumer demand for hard cheese. Hard cheese is cheese that contains 38 to 42% moisture. Commercial production of hard cheese in the United States increased 23% between 1976 and 1983 (3). Approximately 30% of the milk produced in the United States in 1983 was used for the manufacture of hard cheese (3). As a result of the focus on end products of milk production such as cheese, there is an increasing demand among milk producers to receive economic equity for the production of components in milk. Currently there is concern about how producers will be compensated for production of milk protein. If a two-component milk pricing system, based on either protein and fat, or SNF and fat, is adopted on a wide scale, dairy scientists and milk producers will need to develop management, feeding, and breeding systems that will allow production to respond to the economic signals generated by the market. One of the major ways in which producers may respond almost immediately is through changes in feeding. The objectives of this study were 1) to estimate the extent to which changes in feeding may affect the composition of milk and the production of milk protein and milk fat, and 2) to relate market prices of milk protein
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OUR INDUSTRY TODAY and milk fat to changes in dairy cattle feeding practices that dairy producers may profitably implement.
MATERIALS AND METHODS
To determine the effects of feeding on milk production and milk composition, data from 27 reports (1, 2, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22, 25, 26, 27, 28, 29, 30, 31, 32, 3 3 ) w e r e r e v i e w e d and summarized. These reports were selected to provide complete data sets that included milk production, protein, fat and lactose percentages in milk, and dry matter and crude protein intakes. F o r 17 of these reports lactose was calculated by use of the equation: lactose percentage = SNF percentage minus protein percentage minus mineral (ash) percentage. An average of .71% was used for the mineral content of milk (23). Lactose was reported in two publications; and in three reports where neither SNF nor lactose concentrations were provided, an average of 4.75% was used to estimate the lactose concentration in milk. Reports were selected that used feeding and management conditions common to those practiced on dairy farms in the United States. Cows used in the selected studies were generally reported to be healthy, and problems associated with herd health appeared to be evenly distributed among treatments. All data were normalized to a daily basis. After analysis of data sets from the 27 reports, data were grouped according to stage o f lactation o f cows at the time the information was collected. Data were grouped as follows: 1) experiments started with cows at parturition but not continued for a complete lactation; 2) experiments started with cows near the peak of lactation; and 3) experiments started with cows at parturition and continued for a complete lactation. All studies published prior to 1971 were in group 2. The production and management practices of the pre-1971 reports did not, on average, compare favorably to present standards; therefore, data from four of these reports (1, 11, 12, 3 1 ) w e r e removed from the study and one 1975 report was excluded as well (25). Cows included in group 3, fed rations with 49% concentrate, averaged 6405 kg of milk in 305 d; cows fed rations that averaged 59% concentrate averaged 7503 kg of milk in 305 d.
283
A total of 1105 cows from 22 trials representing 97 dietary treatments were included in the revised data set. Of these, 1080 were Holstein, 15 were Jersey (27), and 10 were Ayrshire (28). Parity varied and some cows were in their first lactation. Cows were milked twice daily except in two trials in which they were milked three times daily (7, 8). Group 1 included data for 228 cows from seven trials (8, 10, 13, 15, 16, 28, 32). Data collection periods averaged 17 wk and ranged from 4 to 40 wk. Group 2 included data for 392 cows from nine trials (2, 9, 17, 21, 22, 26, 27, 29, 33), and data were collected for an average of 12.5 wk and ranged from 10 to 16 wk. Group 3 included 485 cows from six trials (4, 6, 7, 14, 20, 30). These data were collected for a minimum of one 305-d lactation and a maximum of three 305-d lactations. Calculations were made to relate intakes of gross energy in feed and the gross energy present in crude protein of feed to output of gross energy in milk fat and milk protein. Calculations were made using a linear model (y = a + bx) in which the energy in milk fat and milk protein was expressed as a function of total gross energT intake in feed or in crude protein of feed for all cows or for each of the three groups of cows. Gross energy of feed and milk components expressed in megacalories (Mcal) was estimated as follows: milk protein, 5.85 Mcal/kg; milk fat, 9.23 Mcal/kg; milk lactose, 3.70 Mcal/kg (19); crude protein in feed, 5.85 Mcal/kg; and nonprotein dry matter, 4.40 Mcal/ kg (2, 15, 16). Corrections were not made for diets that included supplemental nonprotein nitrogen, but inflation of total dietary gross energy was estimated to have been 3.2 (9), 3.8 (10), .5 (20), and .9% (30). Economic input-output data were calculated based on four systems of marketing milk and current feed prices. RESULTS A N D DISCUSSION
A summary of data relating dry matter, gross energy, and crude protein intakes to the production of milk and milk components for all cows is presented in Table 1. Components of milk and feed were expressed as megacalories of gross energy produced or consumed per day so that efficiency of conversion of gross energy in feed to milk constituents could be calculated on a common basis. Journal of Dairy Science Vol. 69, No. 1, 1986
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CRAGLE ET AL.
TABLE 1. Summary of data relating dry matter, gross energy, and crude protein intakes to the production of milk and milk components (1105 cows). SD Milk, kg/d Milk protein, kg/d Milk fat, kg/d Milk lactose, kg/d
24.93 .786 .817 1.179
4.76 .146 .164 .256
Milk gross energy, Mcal/d
16.50
3.14
Dry matter intake, kg/d Crude protein intake, kg/d
17.61 2.69
2.71 .55
Energy intake, Mcal/d Energy intake from crude protein, Mcal/d
77.48 15.75
11.91 3.21
Conversion of gross energy in feed to gross energy in milk Conversion of crude protein in feed to crude protein in milk Milk protein, % Milk fat, % Crude protein in feed, %
In an attempt to refine the data, 36 withinexperiment comparisons were selected from the 97 experimental treatments. Comparisons consisted of rations that averaged 59 or 49% concentrate. Average differences in dry matter intakes, crude protein intakes, feed protein percentages, and concentrate percentages in the rations are in Table 2 for the 36 treatment comparisons among all cows and for treatment comparisons for cows divided into groups according to stage of lactation. Cows fed 59% concentrate in the ration produced an average of 11% more milk, 13% more milk protein, 3% more milk fat, and 11% more milk lactose than cows fed rations that contained 49% concentrate (Table 3). Eighty-five percent of the increased milk protein yield was attributed to increased milk volume and only 15% was attributed to increased protein percentage of the milk. Cows fed rations that contained 59% concentrate consumed an average of 7% more dry matter and 19% more crude protein than cows fed rations that contained 49% concentrate. Similar increases were obtained for the production of milk and milk components and the intakes of dry matter and crude protein when cows were grouped by stage of lactation. The largest increase in these parameters occurred for cows in group 3, but these data were also the most variable. Because of the variation in these Journal of Dairy Science Vol. 69, No. 1, 1986
.216 .299 3.16 3.29 15.25
.046 .063 .21
.34 1.70
data, there were no significant differences between rations that contained 49 or 59% concentrate for any of these comparisons. Many reports discuss the influence of feeding on the production of milk fat and milk protein by dairy cows. In general, feeding a diet of 60% concentrate and 40% forage, balanced to meet the cow's nutrient requirements, results in the greatest energy intake, milk production, and energy output in milk. Feeding more than 60% concentrate in the diet usually lowers milk fat percentage and yield and may, under certain conditions, severely depress milk fat yield. Under certain conditions, feeding large amounts of concentrate may result in a small increase in milk protein percentage and yield. Emery (5) reported that milk protein was increased .015 percentage units for each megacalorie of additional net energy intake, from 9 to 40 Mcal. Milk protein also increased .02 percentage units for each one percentage unit increase in dietary crude protein when dietary protein was increased from 9 to 17%. Oldham (18) reviewed protein-energy interrelationships in dairy cows and pointed out the importance of adequate protein intake for maximizing digestibility and dry matter intake. He further showed that interrelationships between protein and energy yielding nutrients, both within the rurnen and within the ruminant's tissues, can
TABLE 2. Average m i l k p r o d u c t i o n and composition, dry m a t t e r (DM) intakes, and differences between t r e a t m e n t comparisons for cows fed 59% c o n c e n t r a t e or 49% co ncentra te rations. Feed Milk Production (kg/d) All cows (36 t r e a t m e n t comparisons) H1
~a
25.9
L~
23.5
D3
2.4
SD
5.0 4.7 2.0
DM
Protein
Fat
intake
(kg/d) SD
(%)
SD
(kg/d) SD
(%)
.82 .73 ,09
3,19 3.12 .06
,24 .20 .12
.82 .80 .02
3.17 .33 3.42 .30 - . 2 5 .26
,15 ,14 .08
.18 .18 .10
SD
(kg/d)
17.7 16.7 .9
SD
2.7 2.9
1.7
Crude protein i n t a k e
Concentrate
(kg/d) SD
(%DM)
SD
(%Diet) SD
2.8 2.4 .4
16.1 14.6 1.4
1.3 1.8 1.9
59.1 49.2 9.8
.6 .5 .5
13.1 15.6 13.9 ©
Group 1 cows (12 t r e a t m e n t comparisons) H L D
29.3 27.0 2.3
3.9 4.4 1.2
.94 .85 .09
,11
3,23
,12
3,16
.06
Group 2 cows (15 t r e a t m e n t comparisons) H L D
24.0 22.3 1.7
5,6 4.3 2.2
.74 .68 .07
Group 3 cows (9 t r e a t m e n t comparisons) H L D
24.6 21.0 3.6
2.9 3.4 2.2
.80 ,67 .13
.06
,15 ,14 ,11
.94 .95 -.01
.15 .17 .09
3,23 .38 3.54 .28 - . 3 0 .27
16.3 15,5 .8
2.9 3.0 1.3
2.6 2.5 .1
.6 .6 .2
15.9 15.8 ,2
1.1 1.2 .2
67.7 57.1 10.6
9.7 14.4 10.5
,15 .12 .07
3.13 3.05 .07
.32 ,25 .12
.73 .73 .00
.17 .13 .10
3.07 .33 3,32 .35 - . 2 5 .30
18.6 18.0 .6
2.7 2.4 1.7
3.1 2,5 .6
.6 .4 .5
16.4 13.9 2.5
1.5 1.1 2.2
53.2 42.9 10.4
12.2 13.2 18.4
.10 .12 .09
3.24 3.20 .05
.15 .14 .15
.80 .72 .08
.13 .14 .08
2.25 .23 3.42 .20 - . 1 7 .15
18.0 16.3 1.7
1.5 3.0 2.2
2.8 2.4 .5
.4 ,7 ,4
15.7 14.3 1,4
1.3 2.6 1.7
56,8 49.4 7.4
13,6 17.9 8.5
,.-I
~a
on Z 9
0o ox
1 Ration c o n t a i n e d 59% concentrate. 2 R a t i o n contained 49% concentrate. 3Difference for cows fed 59% concentrate minus 49% c o n c e n t r a t e rations. Differences were calculated i n d e p e n d e n t l y ; therefore, small discrepancies exist due to rounding.
tJ 0o
286
CRAGLE ET AL.
TABLE 3. Percentage increase for milk production, milk components, and feed intakes of cows fed 59% concentrate rations compared with cows fed 49% concentrate rations. Parameter
All cows
Group 11
Group 2~
Group 33
(% increase) SD
SD
.~
SD
.~
SD
Milk volume Milk protein Milk fat Milk lactose Dry matter intake Crude protein intake
11 13 3 11 7 19
10 13 13 11 12 22
9 11 0 9 6 7
5 7 9 7 8 8
7 10 0 7 4 23
8 10 13 9 9 23
18 21 13 19 13 27
15 2O 16 16 17 29
Percentage increase in crude protein content of feed dry matter
44
91
17
17
151
120
35
72
Number of cows Numb er of comparisons
752 36
194 12
306 15
252 9
1Experiments started with cows at parturition but not continued for a complete lactation. 2 Experiments started with cows near the peak of lactation. 3 Experiments started with cows at parturition and continued for a complete lactation.
have large effects on the overall conversion of dietary nutrients to milk. Regression equations were calculated f r o m data summarized in Tables 1 and 2 to estimate t h e transfer o f gross energy f r o m feed or f r o m crude protein in feed to milk fat and milk protein (Table 4). Equations calculated f r o m data for cows in each of groups 1, 2, and 3 resulted in less variable estimates of the transfer of gross energy than did equations calculated using p o o l e d data f r o m all cows. This probably occurred because grouping cows by stage of lactation r e m o v e d s o m e of the variation caused by energy mobilization from, or deposition to, b o d y tissues. F u r t h e r m o r e , changes in a m o u n t and types of feeds consumed at various stages of lactation alter ruminal f e r m e n t a t i o n and a p p a r e n t digestibility of ration ingredients, which w o u l d affect the q u a n t i t y of gross energy in feed that is transferred to milk and milk components. I n c o m e above feed costs was calculated for cows fed either 59% concentrate or 49% concentrate rations based on f o u r systems of pricing milk and current feed prices (Table 5). F o u r systems of pricing milk were: 1) base price plus fat differential, 2) base price plus fat differential plus protein differential, 3 ) b a s e Journal of Dairy Science Vol. 69, No. 1, 1986
price plus fat differential plus SNF differential, and 4) end p r o d u c t pricing for cheese. End p r o d u c t pricing for cheese returns m o n e y to the producer based on the m a r k e t price of cheese and the yield of cheese f r o m milk. Daily inc o m e f r o m the sale of milk p r o d u c e d by all cows fed rations t h a t contained either 59% concentrate or 49% c o n c e n t r a t e was not altered when a price differential was included for either protein or SNF (systems 2 and 3) c o m p a r e d with the sale of milk based on o n l y a price differential for fat (system 1). The greater q u a n t i t y of milk p r o d u c e d by cows fed 59% c o n c e n t r a t e in their rations increased daily inc o m e f r o m milk $.42 and daily income over feed costs by $.15 c o m p a r e d with cows fed 49% concentrate in the rations w h e n milk pricing systems 1, 2, and 3 were used. When system 4 for pricing milk was used, additional i n c o m e f r o m milk and income over feed costs was $.45 and $.18/d greater, respectively, for cows fed rations that contained 59% concentrate than for cows fed rations that contained 49% concentrate. Therefore, w h e n cows fed 59% c o n c e n t r a t e w e r e c o m p a r e d w i t h cows fed rations that contained 49% concentrate, pricing milk using system 4 resulted in $.03/d m o r e i n c o m e over feed costs for cows fed 59% con-
OUR INDUSTRY TODAY
287
TABLE 4. Regression equations relating the conversion of gross energy in feed and gross energy in feed protein to energy in protein and fat of milk. 1,2 Slope All cows
MPE = MPE = MFE = MFE =
2.5907 2.5662 4.4924 4.7419
+ .1273 + .0262 + .1935 + .0361
Group 13 cows
MPE = MPE = MFE = MFE =
2.9135 2.5457 4.9864 4.9631
+ + + +
Group 24 cows
MPE MPE MFE MFE
Group 3 s cows
MPE= MPE= MFE = MFE=
r:
PE TE PE TE
P<.0001 p<.o002 p<.o001 P<.0049
.2285 .1332 .1676 .0804
.1593 PE .0389TE .2489 PE .0531 TE
P<.O001 P<.O001 P<.O006 P<.0058
.5805 .5338 .3813 .2670
= 1.5681+.1696PE = -.0353 + .0539 TE = 3.4185 + .2244 PE = .7529 + .0779 TE
P<.O001 P<.O001 P<.O018 P<.O001
.3695 .4983 .2102 .3390
P<.O006 P<.O041 P<.O002 P<.O031
.3955 .2959 .4512 .3115
2.4923+.1157PE 1.5234+.0354TE 3.6077 + .2237 PE 1.9434+ .0658TE
MPE = Gross energy in milk protein, PE = gross energy in feed protein, MFE = gross energy in milk fat, and TE = gross energy in feed. 2 The MPE, MFE, PE, and TE are all expressed in megacalories. 3 Experiments started with cows at parturition but not continued for a complete lactation. 4 Experiments started with cows near the peak of lactation. s Experiments started with cows at parturition and continued for a complete lactation.
c e n t r a t e in t h e i r rations t h a n did using s y s t e m s 1, 2, o r 3. F e e d i n g 59% c o n c e n t r a t e in t h e ration o f cows in g r o u p 3 increased milk yield m o r e t h a n f e e d i n g 49% c o n c e n t r a t e in t h e ration. T h e additional milk p r o d u c e d increased i n c o m e f r o m milk $.84 to $ 1 . 0 5 / d a n d i n c o m e over f e e d c o s t $.46 t o $ . 6 7 / d d e p e n d i n g o n t h e pricing s y s t e m used t o calculate t h e value o f milk (Table 5). Largest increases in i n c o m e f r o m milk and f r o m i n c o m e over f e e d cost w e r e o b t a i n e d w h e n t h e price of milk was calculated b a s e d o n e n d p r o d u c t pricing for cheese (system 4). Pricing milk based o n s y s t e m 2 ( p r o t e i n differential i n c l u d e d ) also increased t h e value o f milk versus using fat differential or fat d i f f e r e n t i a l plus S N F differential. When each o f t h e pricing s y s t e m s f o r milk was used, f e e d i n g cows a p p r o x i m a t e l y 60% c o n c e n t r a t e in t h e r a t i o n r e s u l t e d in greater e c o n o m i c r e t u r n over feed costs t h a n f e e d i n g less c o n c e n t r a t e . C u r r e n t l y a n u m b e r o f milk
m a r k e t i n g cooperatives are suggesting t h a t producers be paid a p r e m i u m f o r their milk based o n its SNF c o n t e n t . However, E r n s t r o m (personal c o m m u n i c a t i o n , 1984) has p o i n t e d o u t t h a t t h e p r o t e i n c o n t e n t o f t h e SNF c o m p o n e n t o f milk m a y vary b e t w e e n 32 and 42%. T h e yield of cheese f r o m milk is d i r e c t l y related t o its p r o t e i n (casein) c o n t e n t . T h e r e f o r e , p a y m e n t f o r milk o n its S N F c o n t e n t m a y n o t p r o v i d e e q u i t y for milk p r o t e i n p r o d u c t i o n because milk p r o t e i n is t h e p r i m a r y c o n t r i b u t o r t o changes in t h e p e r c e n t a g e o f SNF in milk, w h e r e a s lactose a n d mineral p e r c e n t a g e s r e m a i n relatively c o n s t a n t . However, e q u i t y can be achieved for t h e p r o d u c t i o n o f milk p r o t e i n t h r o u g h p a y m e n t based o n S N F c o n t e n t if the a d d e d p r e m i u m is paid for SNF c o n t e n t s above 5.40%, w h i c h r e p r e s e n t s t h e average concent r a t i o n o f lactose and mineral in milk. Pricing milk o n a p r o t e i n basis s t a r t i n g w i t h 0% o r S N F s t a r t i n g w i t h a p p r o x i m a t e l y 5.40% and p a y i n g t h e s a m e rate p e r p o i n t o f increase will result in Journal of Dairy Science Vol. 69, No. 1, 1986
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TABLE 5. Daily income above feed costs based on method of pricing milk for cows fed rations that contained 59 or 49% concentrate. Economic input-output data calculated from within-report comparisons of daily production and feed intakes for cows fed rations that contained 59 or 49% concentrate. Method of pricing milk 1
Plan
Base + fat differential (1)
Base + fat differential + protein differential (2)
Base + fat differential + SNF 2 differential (3)
End product priced for cheese (4)
All cows, 36 treatment comparisons 59% Concentrate rations 49% Concentrate rations Additional income from milk Cost of extra feed 3 Income over feed costs
$6.87 6.45 .42 .27 .15
$6.87 6.45 .42 .27 .15
$6.87 6.45 .42 .27 .15
$7.43 6.98 .45 .27 .18
Group 3 cows, 4 9 treatment comparisons 59% Concentrate rations 49% Concentrate rations Additional income from milk Cost of extra feed 3 Income over feed costs
6.60 5.76 .84 .38 .46
6.63 5.76 .87 .38 .49
6.60 5.76 .84 .38 .46
7.21 6.16 1.05 .38 .67
1Base price = $12.60/45.4 kg; fat differential = $. 17/point with a 3.5% standard; protein differential = $. 13/ point above 3.2%; SNF differential = $.10 above 8.75%; end product pricing= $1.40/.454 kg for 40% moisture cheese. 2 SNF = Solids-not-fat. 3The cost of extra feed was calculated using the following assumptions: soybean meal, $12/45.4 kg (90% dry matter and 44% protein) and corn grain, $7.00/45.4 kg (85.5% dry matter). 4 Experiments started with cows at parturition and continued for a complete lactation.
a b o u t t h e same e c o n o m i c r e t u r n a b o v e f e e d costs f o r p r o d u c t i o n o f p r o t e i n . Alternatively, m i d p o i n t s of 3.2% milk p r o t e i n or 8.60% milk SNF can be u s e d as a starting p o i n t f o r p a y i n g a differential f o r these milk c o m p o n e n t s t o achieve p r o t e i n p a y m e n t e q u i t y b a s e d on a premium and debit system. As m o r e is learned a b o u t t h e cost o f transferring milk c o m p o n e n t s i n t o milk p r o d u c t s c o n s u m e d b y t h e public a n d h o w c o m p o n e n t pricing will a f f e c t r e t u r n s t o t h e p r o d u c e r and processor, changes will o c c u r in milk pricing systems. T h e s e changes should r e f l e c t e q u i t a b l e p a y m e n t t o t h e p r o d u c e r based o n t h e c o m p o n e n t s in milk t h a t are u s e d f o r p r o d u c i n g products c o n s u m e d b y t h e public. REFERENCES
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Journal of Dairy Science Vol. 69, No. 1, 1986