Interrelationships Between Feed Quality, Digestibility,. Feed Consumption, and Energy Requirements in. Desert (Bedouin) and Temperate (Saanen) Goats.
Interrelationships Between Feed Quality, Digestibility, Feed Consumption, and Energy Requirements in Desert (Bedouin) and Temperate (Saanen) Goats NISSIM S l L A N I K O V E 1 Faculty of Life Science University of Tel Aviv Israel ABSTRACT
are meager and primarily of low quality. Low quality pastures are characterized by low protein and high cell wall content, resulting in a relatively low intake. Bedouin goats from extreme desert areas have higher gross energy digestibility than Swiss Saanen goats from temperate areas (17, 18, 19, 21, 22). Digestibility by the desert bred animals was superior even when good quality hay (alfalfa) was offered (21, 22). It was more pronounced when a poorer quality feed, wheat straw, was offered. When wheat straw was the only feed, Bedouin goats utilized more energy and maintained their body weights, whereas Saanen goats lost weight continuously (22). The objective o f this study was to elucidate the interrelationship between feed quality, digestibility, feed consumption, and energy requirements in goats from desert (Bedouin) and temperate (Saanen) regions.
Intake of high quality roughage (alfalfa hay) by black Bedouin goats was lower than by Swiss Saanen goats. Bedouin goats have lower energy requirements and less tendency to accumulate solids. Apparent dry matter digestibility was higher in Bedouin than Saanen goats even when high quality hay was offered. It was more pronounced when a medium quality roughage (Rhodes grass mixed with alfalfa) was fed. Differences in apparent digestibility of dry matter were greater when a poor quality feed such as wheat straw was offered. Similar differences between the two breeds were noted in relation to the apparent digestibility of cell wall constituents (cellulose, hemicellulose, and lignin) and nitrogen. When medium quality roughage was fed, Bedouin goats apparently consumed enough energy to sustain both maintenance and production, whereas Saanen goats consumed only enough to maintain very low production. Bedouin goats maintained their b o d y weight and solids on an energy intake up to 50% less than the estimated maintenance requirement of goats, whereas Saanen goats lost body weight and solids. It is suggested that reduction in metabolic rate helps desert ruminants cope with chronic energy shortage.
MATERIALS AND METHODS Animals
INTRODUCTION
Feed resources in desert and tropical areas are dependent on rainfalls, which are restricted to several months only. Consequently, pastures
Received June 24, 1985. I MIGAL - Galilee Technological Center, Kiryat Shmona, 10200, Israel 1986 J Dairy Sci 69:2157--2162
A small herd of Black Bedouin goats was purchased from Bedouins in the Eastern Sinai along the Gulf of Eilat. The herd was kept and bred in the research zoo of Tel Aviv University under continuous veterinary supervision. Experiments were conducted on four Black Bedouin and four Swiss Saanen goats. All animals were adult nonlactating females. Body weight of the goats ranged from 18 to 22 kg (Bedouin) to 30 to 50 kg (Swiss). Diets
High (alfalfa hay), medium (Rhodes grass mixed with alfalfa), and low (wheat straw) quality roughage diets were tested. Grading of diets was based on composition of nitrogen and cell-wall constituents (Table 1).
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TABLE 1. Chemical composition of diets. 1
Energy, kcal/g Protein (N × 6.25), % Celt wall, % Cell content, % Acid detergent fiber, % Acid detergent fignin, % Hemicellulose, % Cellulose, % Ash, %
Alfalfa hay
Rhodes grass mixed with alfalfa hay
Wheat straw
4.42 16.25 50.84 49.16 42.12 7.62 8.72 34.50 7.91
4.41 11.18 63.48 36.52 37.72 6.70 25.76 30.02 7.71
4.42 3.63 85.13 14.87 54.22 14.15 30.91 40.07 7.53
1Dry matter basis.
Experimental Procedures
Goats were kept in metabolic cages at room temperatures ranging from 20 to 26°C and relative humidity of 60 to 70%. Thirty days were allowed for adaptation to each diet. Feed in baled form in an amount 10% above the intake recorded on the previous day was given in two equal portions at 700 and 1600 h. Animals were weighed every 3 d during adaptation and collection periods. Water was offered once a day for several minutes in the afternoon. Following adaptation, feed intake, feed residues, and fecal output were recorded daily for 10 d. Daily subsamples (5%) of feed residues and feces were pooled for chemical analysis. Apparent dry matter digestibility was calculated by the total collection method. Total body water and body solids were determined 20 and 50 d after the introduction to each dietary treatment. Body water was determined as tritiated water space (12) and body solids as the difference between body weight and body water. Chemical Methods and Statistical Analysis
Core samples from bales were taken twice during the 10-d collection period. Dry matter, organic matter, and nitrogen (Kjeldahl) were determined by standard procedures (1). Cellwall (neutral detergent fiber) constituents (cellulose, hemicellulose, and lignin) and acid detergent fiber were determined by procedures of Goering and Van Soest (11). Gross energy of Journal of Dairy Science Vol. 69, No. 8, 1986
diets was determined in triplicate in ballistic bomb calorimeter (Gallenkamp, UK). Treatment means from the three feed trials were examined for significance by t test for each trial separately. RESULTS
When high quality alfalfa hay was given to both breeds, intake of dry matter was 33% lower (P
