Response of Dairy Cows in Early Lactation to Additions of Cottonseed Meal in Alfalfa-Based Diets1 E. E. GRINGS,2 R. E. ROFFLER,3 and D. P. DEITELHOFF' Department of Animal SCience University of Idaho Moscow 83843

ABSTRACT

lactation. Increasing dietary CP above 17.5% showed little benefit in milk yield. Increasing dietary protein caused an increase in blood urea N and milk NPN, indicating N wastage by the animal. (Key words: cottonseed meal. protein, dairy cows)

The effect of increasing CP levels by additions of cottonseed meal to diets for early lactation was studied in 24 multiparous Holstein cows. Diets containing 13.8, 17.5,20.4, and 23.9% CP were fed during three 3-wk periods beginning at wk 4 postpartum. Each cow received three of the four dietary treatments giving 18 observations per treatment in a randomized complete block design. Undegraded intake protein as a fraction of total protein for the diets was .25, .32, .36, and .39. Dry matter intake increased linearly with increasing dietary CP concentrations. Daily milk yield increased as dietary CP increased from 13.8 to 17.5%. Increased milk yield was accompanied by increased daily yields of milk fat and protein, but the concentration of these components in milk was not altered. The proportion of total milk N that was NPN increased linearly with increasing dietary CP level. Plasma amino acids and urea N were increased by increasing the dietary CP level. The conclusions of the study were that increasing dietary CP levels from 13.8 to 17.5% by the use of cottonseed meal was beneficial to cows consuming alfalfa-based diets in early

Abbreviation key: CSM = cottonseed meal, DIP = degradable intake protein, EE = ether extract, UIP = undegraded intake protein, UIPIP = UIP as a fraction of intake protein, WCS = whole cottonseed. INTRODUCTION

Received November 19. 1990. Accepted February 19, 1991. lIdaho Agricultural Experiment Station Publication Number 9047. Supported by the University of Idaho. National Cottonseed Products Association, and the United D~ of Idaho. Present address: USDA-ARS. Ft. Keogh Livestock and Range Research Laboratory. Roule I, Box 2021. Miles City. MT 59301. 3Present address: Dairy Nutrition Services. Chandler. AZ 85224. 4Present address: Western Wisconsin Technical College, LaCrosse 54602. 1991 1 Dairy Sci

74:258~2587

Current recommendations (12) for formulating rations for lactating dairy cows involve the use of degraded (DIP) and undegraded intake protein (UlP). Recommendations also are being made for dietary NDF levels. Evaluating performance based on these values will help to further refine estimates of the dietary needs of these components. Evaluating the response in milk. production and feed intake with increasing levels of a single protein supplement provides information needed to develop a doseresponse that can be used with current feed cost and milk. price information to formulate economical dairy rations. Alfalfa is a widely used source of energy, fiber, and protein for dairy cows in the western United States. The high solubility and degradability of alfalfa protein, however, may result in N wastage in the rumen. Additional sources of feed protein, a portion of which will pass out of the rumen undegraded, may be necessary to supplement the protein in alfalfa forage. The objectives of this study were to evaluate the effects of increasing dietary CP and UIP by increasing dietary levels of cottonseed meal (CSM) for cows in early lactation fed alfalfa-based diets.

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COTIONSEED MEAL IN EARLY LACfATION TABLE 1. Ingredient composition of TMR. Dietary CP

Ingredient

13.8%

175%

2004%

23.9%

- - - - - - - (% of DM) - - - - - - -

Alfalfa hay Alfalfa-grass silage Whole cottonseed Barley Com Cottonseed meal Dicalcium phosphate Diammonium pho~hate Trace-mineral saltl Sodium bicarbonate Magnesium oxide Vitamin-Se mix2

28.9 12.5 10.3 27.0 17.8

28.9 12.5 10.3 21.8 14.4 8.6

1~

1~

51 .41 .51 .26 .16

.51 .41 .51 .26 .16

28.9 12.5 10.3 16.7 U.5 16.6 1M .51 Al .51 .26 .16

28.9 12.5 10.3 125 8.1 24.2 1.65

.51 .41 .51 .26 .16

IContains 99% NaCl, .35% b1, .2% Fe, .18% Mn, .037% Mg, .035% Cu, .01% I and .006% Co. 2Each idIogram contains 8.8 million IU vitamin A, 4.4 million IU vitamin D, 4996 IU vitamin E, and 176 mg Se.

MATERIALS AND METHODS

Twenty-four multiparous, lactating Holstein cows were used in a randomized complete block design to determine the effect of increasing CP in the diet along with increased UIP on production parameters. Dietary CP levels were increased by the addition of prepressed, solvent-extracted CSM to the grain mix. The proportions of barley and corn in the mix were decreased as the amount of CSM increased (Table 1). Cows were fed a diet containing 17.5% CP (OM basis) during the fIrst.3 wk after calving. Cows producing a minimum of 27 kg/d of milk during the 3rd wk of lactation were placed on experiment. Each cow was assigned to a sequence of three diets that were fed during three 21 -d experimental periods so that each cow received three out of four treatments and all 24 possible sequences of three diets were used. The 1st wk of the period was used as an adaptation period, and the fmal 2 wk were used for data collection. Cows were fed diets containing 48% concentrate mix, 10% whole cottonseed (WeS), and 42% mixed alfalfa forage (OM basis; Table 1). Dry matter of forages was measured weekly, and the amount of silage and hay was adjusted to maintain a constant ratio of 70% hay to 30% silage on a DM basis. Total mixed rations were fed twice daily with 5 to 10% feed refusal. Orts were weighed once daily. Cows were housed together but were fed individually with electronic doors (American Calan, Inc., Northwood, NH).

Samples of TMR were collected daily, and samples of concentrate mixes, forages, WCS, and orts were collected twice weekly. All feed and ort samples were dried in a forced-air oven at 55·C for 48 h. Samples of forages and TMR were ground to pass a I-rom mesh screen in a Wiley mill (Arthur H. Thomas, Philadelphia, PA) and composited on a biweekly basis for analysis of DM and CPo Two consecutive 2-wk composites were combined for further chemical analysis. Analysis included DM, ash, Kjeldahl N, ADF (I), NDF, and ADIN (4). Ether extract (EE) was determined by refluxing a 2.5-g sample in anhydrous ethyl ether for 7 h. Calcium and P were determined by inductively coupled plasma spectroscopy (Bausch and Lomb, Sunland, CA) after a wet ash digestion (6). Samples of each ingredient were collected each time a batch of concentrate was mixed. These samples were ground to pass a I-rom screen using a Wiley mill. Each dietary ingredient was composited into three samples for amino acid analysis (Beckman 121 Amino Acid Analyzer, Bellevue, WA). Samples of WCS were subjected to extraction of ethersoluble compounds prior to amino acid analysis. Dietary amino acid composition was calculated based on proportions of ingredients in the diet and actual amino acid composition of dietary ingredients. Ruminal degradability of CP was evaluated in situ using composites of individual feed ingredients. Two lactating Holstein cows were Journal of Dairy Science Vol. 74, No.8, 1991

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TABLE 2. Chemical composition of TMR. Dietary CP

Item

13.8%

17.5%

20.4%

23.9%

OM, %

73.0

73.3

73.3

73.5

ADIN, % of total N UIPIP1

7.39 .25

6.94 .32

30.43 40.79 4.47 9.21 .96 .74

29.32 40.60 4.47 9.20 .94 .72

622 .36

5.69 .39

30.10 40.12 4.15 9.90

30.68 40.70 4.00 9.99 1.07 .86

(% of OM) ADF NDF EEl Ash Ca

P lUIPIP

= Undegraded

1.06

.83

intake protein as a fraction of intake protein, EE

fed an alfalfa forage-based diet that contained soybean meal as the protein source. Cows were fed four times daily with a total intake at 3.0% of BW. Three grams of ground feed were placed into Fyntex bags (B&S Thompson & Co., LID., Montreal, PQ, Canada) (48-1J. pore size, 7 x 11 cm), and bags were tied with dental floss. Two bags of each feed were placed into the rumen of cows at each of five incubation times (2, 6, 12, 24, and 48 h). Placement of bags was such that all bags were removed from the nnnen at one time. Bags were washed in a washing machine through two rinse cycles, dried for 48 h at 55"C, cooled, and weighed. Kjeldahl N was determined on the residue. Rate and extent of degradation were determined using the NUN procedure of SAS (19) and the equations suggested by NRC (10). A mobile nylon bag procedure (3) was used to detennine the availability of CSM protein in the small intestine. One gram of CSM was placed into Fyntex bags (3.5 x 7 cm), and the bag was closed with dental floss. Four bags were placed into the rumen of each cow and incubated for 12.5 h. Upon removal from the rumen, two of the bags were frozen, and the other two were placed into pepsin (I g pepsin! L .IN HCI, pH 2.0, 39"C) for 3 h followed by insertion into the proximal duodenum through a T cannula. Upon recovery from the feces, bags were frozen until all bags had been recovered. This procedure was repeated on a 2nd d. Bags were washed, dried, and weighed, and the residue was analyzed for N. Cows were milked twice daily, and milk weights were recorded in a computerized recJournal of Dairy Science Vol. 74, No.8, 1991

= ether extract.

ord keeping system. Milk was sampled during four consecutive milkings during d 5 to 7 of each week, and weekly composites were analyzed for fat by infrared analysis (Washington DHIA, Bellingham, WA) and for total solids, ash, N (1), NPN and noncasein N (18). Blood was collected from the coccygeal vein 4 h after the moming feeding on d 20 of each experimental period. Blood was placed into heparinized tubes and kept on ice until return to the laboratory. Plasma was separated by centrifugation (5000 x g for 15 min). Plasma was deproteinized with 15% 5-sulfosalicylic acid for 30 min at room temperature followed by centrifugation at 15,000 x g for 30 min. Deproteinized blood samples were stored for later analysis of amino acids (Beckman) and urea N (Sigma Chemical Co., St. Louis, MO).

Data were analyzed using the general linear models procedure of SAS (19) with a model that included cow, diet, period, and diet by period interaction. Trends due to increasing CP level were analyzed using orthogonal polynomials. Comparisons among least squares means were by least significant difference. Significance was declared at a probability of .05 unless otherwise noted. A response curve relating UIP to milk yield was generated using Gauss-Newton techniques (19). RESULTS AND DISCUSSION

Chemical composition of the TMR is presented in Table 2. In addition to increased CP content, concentrations of ash, Ca, and P also increased as greater proportions of CSM were

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TABLE 3. Rapidly degrade