Effects of dietary protein level on performance of Angora and cashmere-producing Spanish goats

Small Ruminant Research ELSEVIER

Small Ruminant Research 16 (1995) 113-119

Effects of dietary protein level on performance of Angora and cashmere-producing Spanish goats Z.H. Jia, T. Sahlu”, J.M. Fernandez, S.P. Hart, T.H. Teh E (Kika) de la Garza Insfirm forGoat Research, P.O. Box 730, Lmgston University, Lungston, OK 73050, USA

Accepted 10 May 1994

Abstract Effects of dietary crude protein level on fiber production of Angora and cashmere-producing Spanish goats were studied in 16 yearling doelings (eight Spanish, eight Angora) for 8 weeks. Goats were housed in individual stalls and maintained at constant temperature (21°C) with 9 h light and 15 h darkness each day. Goats were initially sheared, blocked by body weight (BW) and assigned to one of two dietary treatments (8% or 16% crude protein (CP) ) in a 2 X 2 factorial design. Diets were isocaloric (2.9 Meal kg- ’ digestible energy (DE) ) and were fed ad libitum. Dry matter intake (DMI) was similar for Angora and cashmere-producing Spanish goats. Daily DMI (612 vs. 892 g day-‘) and BW gain (38 vs. 127 g day-‘) were greater (P < 0.05) for cashmere-producing Spanish goats fed the 16% CP diet compared to 8% CP. For Angora goats, DMI (734 vs. 832 g day - ’ ) and BW gain (55 vs. 116 g day - I) were also increased (P < 0.05) at the 16% CP level. Nitrogen retention (2.2 vs. 8.7 g day- ‘) increased (P 0.05) by diet CP level for cashmere-producing Spanish goats. Increasing diet CP level increased mohair production, diameter and staple length, but had little effect on cashmere fiber production. Increasing dietary protein also increased DMI, BW gain and feed efficiency in both types of goats. Keywords: Angora goats; Cashmere;

Metabolites;

Mohair; Protein; Spanish goats

1. Introduction Both mohair and cashmere fibers grow from the secondary hair follicles of goats (McGregor, 1988). Cashmere fiber growth in goats differs from mohair growth in Angora goats because cashmere grows during decreasing daylength and is shed during increasing daylength (Ryder, 1966)) whereas mohair growth is a continuous process ( Shelton, 198 1) . Most non-Angora * Corresponding 0921488/95/$09,50

author. 0 1995 Elsevier Science B.V. All rights reserved

SsDlO921-4488(95)00616-8

breeds of goats in America produce cashmere (Teh, 1989). Wool growth and fiber diameter significantly increased in sheep with increased protein intake (Weston, 197 1). Sahlu et al. ( 1992b) reported that mohair production was greater from Angora goats fed diets containing 19% crude protein (CP) than from those fed 12% CP. For cashmere-producing goats, Australian studies have concluded that there was no relationship between dietary CP intake and cashmere fiber production (Ash and Norton, 1984; Johnson and Rowe, 1984; McGregor, 1988). Objectives of the present study were

114

Z.H. Jia et al. /Small Ruminant Research 16 (1995) 113-119

to compare responses of cashmere-producing Spanish goats and Angora goats to low (8%) and high ( 16%) dietary CP levels in terms of body weight (BW), mohair and cashmere fiber parameters, nitrogen (N) retention and blood parameters.

2. Materials and methods

week experimental period. Goats were fed ad libitum daily (09:OO h) to allow 10% orts, and fresh water was continuously available. Orts were composited weekly for calculation of weekly dry matter intake (DMI). Representative feed samples were taken throughout the trial. Feces and urine were collected daily over the 8 week study. Fecal and urine samples were composited for each week and frozen ( - 20°C) for analysis. Body weights were taken on two consecutive days each week.

2.1. Animal and diets 2.2. Measurements Effects of dietary protein levels on fiber production in Angora and cashmere-producing Spanish doeling goats (Cashmere) were studied in a 2 X 2 factorial design with 16 yearling goats (eight Spanish, mean BW 19.5 kg; eight Angora, mean BW 20.4 kg). Goats were housed in individual metabolism cages at constant temperature (21°C) and controlled photoperiod (9 h constant lighting: 08:00-17:00 h). Doelings were stratified by BW and assigned to one of two diets. The diets were formulated to be isocaloric (2.9 Meal digestible energy (DE) kg- ’ ) and contained 8% or 16% CP. Composition and chemical analyses of the diets are shown in Table 1. All goats were handled as a single group for 2 weeks adaptation prior to the 8 Table 1 Composition

and chemical analyses of the experimental

rations

Protein level

Item

8%

16%

Diet composition (% DM) Ground corn Ground oats Cotton seed hulls Soybean oil meal (44%) Dicalcium phosphate Trace mineral mix” Calcium carbonate Vitamins A, D, Eb

50.0 2.8 44.0 1.1 1.0 0.2 0.7 0.2

29.5 2.8 44.0 21.9 0.7 0.2 0.7 0.2

Chemical analysis DM CP NDF ADF

89 8.7 61.2 26.0

90.0 15.7 64.4 27.3

(% DM)

“Contained 98.8% NaCI, 7.2 ppm Cu; 5.4 ppm Co, 21.0 ppm Fe, 24.0 ppm Mn, 21.6 ppm Zn, 10.2 ppm I. bProvides 1000 IU vitamin A, 100 IU vitamin D and 10 IU vitamin E kg- ’ diet.

and analyses

Samples of feed, orts and feces were dried at 65°C for 3 days, allowed to air-equilibrate, and ground in a Wiley mill to pass a 1 mm screen. Dry matter (DM) was determined by drying a 1 g sample overnight at 105°C. Ground feed, orts, fecal samples and freezedried urine samples were analyzed for N (Technicon, Tarrytown, NY). Energy content (gross energy, GE) was measured using a Parr adiabatic oxygen bomb calorimeter (Parr Instrument, Moline, IL) ; acid detergent fiber ( ADF) and neutral detergent fiber (NDF) were measured by the method of Goering and Van Soest ( 1970). Jugular blood samples were obtained on Days 14, 28 and 42 at 0 and 3 h post-feeding. Blood samples were collected and handled as described by Sahlu et al. ( 1992a). Samples were analyzed for packed cell volume (PCV; Readacrit Centrifuge, Clay Adams, Parsippany, NJ), plasma total protein (PTP), urea-N (PUN), glucose and non-esterified fatty acids (NEFA) as previously described (Sahlu and Fernandez, 1992). Plasma creatinine was assayed using a commercial kit (No. 555; Sigma, St. Louis, MO). The hormones triiodothyronine (Kit 72661)) thyroxine (Kit 72662) and cortisol (Kit 72659) were assayed using radioimmunoassay kits (Ventrex Laboratories, Portland, ME). Hormone assays were duplicated in a single assay, and duplicate samples exhibiting greater than 7% error were reanalyzed. The average intra-assay coefficient of variations for triiodothyronine, thyroxine and cortisol procedures were 9.2%, 6.0% and 8.2%, respectively. Goats were sheared at the beginning and end of the experiment. Total fleece weight was determined for both breeds. Yields of fleeces were determined after scouring (ASTM, 1990). Mohair and cashmere fiber length and diameter were determined as previously described (Sahlu et al., 1992b). For each Cashmere

Z.H. Jia et al. /Small

Ruminant Research 16 (1995) 113-119

115

goat two subsamples ( 1.OO g) were randomly drawn and separated manually into cashmere and guard hair, and weighed (to nearest 0.1 mg) to determine percentage cashmere yield. Data were analyzed as a completely randomized design. Analyses for factors of breed, protein level and their interaction were calculated using methods of the SAS Institute Inc. ( 1989). Blood parameters were analyzed as a split-plot in time.

ing the high protein diet gained 150% more weight (P < 0.001) than those on the lower CP diet. Hart et al. ( 1993) also observed a similar improvement in BW gains of goats consuming high protein forages over goats consuming low protein forages. Feed efficiency (kg gain per kg of feed) was 58% greater (P < 0.01) for Cashmere goats as compared to Angora goats. Feed efficiency was twice as great (P < 0.002) for animals consuming the higher CP diet, indicating that protein level was limiting.

3. Results and discussion

3.2. Digestibility and nitrogen balance

3.1. Dry matter intake and liveweight change

DM, energy and digestibilities were significantly greater (P < 0.01) for goats consuming the high protein diet (Table 2). This was attributed to increased CP (P < 0.001) and NDF (P < 0.10) digestibilities for the high CP diet. Cheema et al. (1991) reported a direct relationship between percentage of dietary protein and apparent digestibility of feed protein. The regression

DMI was similar for both breeds of goats, but was greater (P < 0.005) for the higher CP diet (Table 2). Higher levels of CP are known to stimulate DMI (Huston et al., 1988). Cashmere goats gained 66% more weight (P < 0.05) than Angora goats. Goats consumTable 2 Effects of dietary protein level on DM intake, BW gain and feed efficiency and cashmere-producing Spanish goats Parameter

DMI (gday-I) Gain (g day-‘) FE (kg gain per kg feed)

Protein

Breed Angora

134 63.3 0.080

(FE), digestion of diet components

Cashmere

8% CP

SE 16% CP

752

673

862

37

105

46

115

11

0.126

0.066

0.132

Significance

Protein

(B)

(P)

_

0.05

0.001

_

0.011

0.02

0.002

_

_ _

0.01 0.001 0.10 _ _ _ 0.01 0.00 1

_ _ _ _ _ _ _

0.001

_

0.001

_

59.6 44.3 51.6 11.1 45.8 24.9 59.8 15.4

55.2 31.5 47.4 22.1 40.0 22.1 55.5 9.33

61.1 55.2 53.2 22.2 34.5 15.4 61.3 21.6

1.3 1.1 2.1 2.8 3.4 5.0 1.3 0.7

(gday-‘) N absorbed

7.2

1.6

2.9

11.9

0.3

71.1

72.4

76.4

73.1

4.2

_

5.6

5.3

2.2

8.7

0.2

_

(g day-‘)

BxP

0.005

56.7 42.4 49.1 27.2 28.7 12.5 56.9 15.5

absorbed N retained N retained

P<

Breed

Digestibility DM CP NDF ADF Ca P Energy N intake

(gday-‘) Percentage of

and nitrogen balance of Angora

0.05 0.01 _ _ _

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Z.H. Jiaetal./SmaN

RuminantResearch 16(1995) 113-119

equation describing digestible protein in the. present study is DP=0.845( _+O.O23)CP-4.6( +0.3) as compared to an overall digestibility of 70% used by the NRC ( 198 1) . This equation is different from the one given by Knight and Harris (1966) for goats (DP = 0.9 16CP - 2.76). Digestibility of ADF was greater (P < 0.05) for Angora goats than for Cashmere goats, whereas calcium digestibility was greater (P < 0.01) for Cashmere goats than for Angora goats. There were no breed or protein effects (PO. 10) on digestibility of P. There were no breed effects (P > 0.10) for N balance variables. Sahlu et al. ( 1993) observed no significant differences in digestibility or N balance when Angora, Alpine and Nubian wethers were fed diets containing 9%, 12% and 15% CP in a total mixed ration. In the present study N intake, N absorbed and N retained were all significantly greater (P
Huston, 1966) and the UK (Deaville and Gailbraith, 1992). The increased fiber weight was due to an increase in both staple length and fiber diameter. In this study 80% of the difference was attributed to increased mohair staple length and only 20% to increased fiber diameter. This is contrary to our other studies which showed a dominant effect of increased fiber diameter on mohair weight when Angora goats were fed higher protein levels (Hart et al., 1993; Sahlu et al., 1993). Fiber diameter had increased (P < 0.05) at the high level of protein, in agreement with our studies (Hart et al., 1993; Sahlu et al., 1993) and that of Deaville and Gailbraith ( 1992). The increase in fiber diameter ( 1.6 pm) is less than that calculated (2.5 pm) from the equation of Sahlu et al. ( 1993). This can be attributed to these goats being younger than those used in the previous study (10 vs. 16 months of age and 21 kg vs. 27 kg), which may account for the different proportion of increased mohair coming from increased fiber length.

3.3. Fleece growth

3.3.2. Cashmere Increased dietary protein level increased guard hair production (P < 0. IO) but did not affect any cashmere production traits (Table 3). This agrees with previous studies (Ash and Norton, 1984; Johnson and Rowe, 1984; McGregor, 1988) for Australian cashmere-producing goats. The lack of increase in cashmere fiber production in response to increased protein was attributed to the fact that cashmere production in a given

3.3. I. Mohair Mohair fiber weight was increased (P < 0.01) 3 1% with the higher protein diet (Table 3). This is comparable to the 40% increase in mohair production observed by Sahlu et al. ( 1992b), as dietary protein level was increased from 9% to 15%, and consistent with studies on Angora goats in Texas (Shelton and Table 3 Effect of dietary crude protein level on mohair and cashmere parameter Parameter

Angora Clean fiber weight (g) Fiber length (cm) Fiber diameter (pm) Cashmere Fleece weight (g) Down mechanical yield (%) Guard hair mechanical yield (%) Cashmere down weight (g) Guard hair weight (g) Down length (cm) Fineness

Protein level

Difference

SE

8%

16%

P<

862 4.80 30.6

1132 s.21 32.2

0.01 0.005 0.05

43 0.06 0.4

62.3 62.4 38.6 40.1 22.1 2.12 15.5

71.3 51.8 48.2 38.7 32.5 1.83 15.8

_

13.1 5.0 5.0 10.4 3.1 0.14 0.2

_ 0.10 _

Z.H. Jiaetal./Stnall Table 4 Blood parameters Parameter

in Angora and cashmere producing-Spanish Breed Angora

Glucose

70.0

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goats fed low and high levels of dietary protein Protein

Cashmere 68.7

117

8% CP 67.0

SE 16% CP 71.7

Significance Breed

5.5

P< Protein

BXP

_

(mg dl-‘) NEFA (IJeo 1-l) Urea-N (PUN) (mg dl-‘) Plasma

156

242

215

183

80

0.10

-

13.1

14.4

8.4

19.1

1.5

_

0.001

-

59.7

57.4

58.1

59.0

4.4

_

_

_

0.05

0.10

0.02

0.01

0.001 -

total protein (g I--‘) Creatinine (CRE) (mgdl-‘) PUNICRE Packed cell volume (%) Thyroxine (ng ml-‘) Triiodothyronine (ng ml-‘) Cortisol (wgdl-‘)

0.46

0.54

0.55

0.44

34.8 27.7

29.6 31.3

15.5 29.9

48.9 29.2

3.7 2.0

78.7

81.5

86.9

73.2

10.2

_

2.1

2.0

2.3

1.8

0.3

-

0.01

4.6

12.0

4.5

12.4

2.2

0.001

0.001

-

0.05

climate and photoperiod is predominantly controlled by genetic factors (Johnson and Rowe, 1984), as indicated by high he&abilities for these traits (Pattie and Restall, 1992). Later, McGregor ( 1988) reported an increase in total cashmere production and fiber diameter over the entire cashmere growing season when energy supplementation increased goats’ body condition and BW. The lack of response in cashmere production and quality in the present experiment and in previous studies with either increasing amounts of protected proteins (Johnson and Rowe, 1984) or D,Lmethionine supplementation (Ash and Norton, 1987) suggests that the cashmere production potential of goats used in these studies was too low to respond to supplemental protein, whereas Angora goats increased fiber production in response to protein supplementation. These present findings warrant further investigation of protein nutrition of Cashmere goats having high fiber production potential.

0.005

3.4. Blood metabolites and hormones Plasma glucose and NEFA were not affected (P > 0.10; Table 4) by protein level or breed and were within normal ranges for fed goats (Sahlu et al., 1993). De Jong (1981) reported an initial sharp decline in circulating glucose concentration of goats after feeding, followed by a rise 1 h after feeding. Trenkle and Kuhlemeir ( 1966) reported an inverse relationship between glucose and NEFA, especially with feed deprivation. Sahlu et al. ( 1993) did not see any changes in plasma glucose and NEFA in response to dietary CP. However, concentrations of plasma glucose were relatively lower and of NEFA higher between samples taken before and after feeding in agreement with present observations (data not shown). PUN was not affected (P > 0.05) by breed but was higher (P 0.10) by breed or CP level. In a previous study (Sahlu et al., 1993) PTP

118

Z.H. Jiaetal./SmallRuminantResearch16(I995)113-119

was elevated in does fed a 19% CP diet compared to 12% CP. Creatinine was reduced (P
4. Conclusion

Increasing CP levels increased fiber production in Angora goats while not affecting cashmere production in Spanish goats. Angora goats appeared to digest ADF better than Spanish goats whereas the reverse was true for calcium digestion. Protein supplementation increased intake and digestibility of the diet. Creatinine and PCV were lower for Angora goats. PUN and PUN/ creatinine were increased for the high protein diet and triiodothyronine and thyroxine were reduced.

Acknowledgments The research was supported by the USDA, Cooperative State Research Service Project Number OKLX94-01. The authors thank Glenn Detweiler and Ronald Starks of the E. (Kika) de la Garza Institute for Goat Research for care and feeding of the goats; we appreciate the assistance of Kesete Tesfai in the laboratory analyses.

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