Seasonal changes in composition and intake of chaparral by Spanish goats

Abstract

Seasonal changes in utilization of one-year regrowth of chaparral vegetation by Spanish goats were investigated. The dominant shrub species were: oak ( Quercus dumosa and Q. wislizenii), chamise ( Adenostoma fasciculatum), manzanita ( Arctostaphylos glandulosa) and ceanothus ( Ceanothus cuneatus, and C. foliosus). Oesophageal and faecal samples were obtained during the spring, summer and autumn seasons of 1979. Mean daily temperatures for the three seasons were 19, 18 and 12° C, respectively. Winter sampling was restricted by cold weather at the 985-m elevation site. Cover was measured from ten permanent transects. Preference of Spanish goats was highly directed towards oak (> 50%) and chamise (> 30%) in all seasons. Correlation of selectivity (percentage botanical composition in the diet) and availability data indicated that goats may be generalist in their feeding strategies, but display some sort of specialized behaviour in selecting between the most dominant species. The observation that selection of herbaceous vegetation was restricted by availability conforms with the recent classification of goats as adaptive mixed feeders rather than browsers. Daily feed intake (g DM/kg BW 0.75) was calculated by dividing faecal residue by (100—digestibility in vitro). Intake values were equivalent to maintenance requirements during spring (60 g) and summer (57 g). However, autumn chaparral provided sub-maintenance intake levels (36 g). Condensed tannins (ADF—NAD), estimated as the difference between acid detergent fibre (ADF) and sequential acid detergent residue of neutral detergent residue (NAD), were variable in the clipped shrub samples but low in all dietary samples (2.1 ± 1.8%). The low levels of tannins did not appear to be affecting utilization of this browse. Predictive equations for intake (DMI) and digestibility in vitro (IVOMD) were derived from step-wise regression analysis using the following independent variables: cell wall content (CWC), NAD, cellulose (NADC), NAD sulphuric acid insoluble lignin (NADL s), hemicellulose (NADHC), lignin: ADF—NAD tannins, ash and nitrogen (N) The equation for intake was: DMI (g DM/kg BW 0.75) = −25.67 + 1.80 OMD ( n = 56, Syx = 17.72, r = 0.59, P < 0.005), while digestibility (%) was predicted as OMD = 56.98 − 0.46 CWC − 0.45 NADL s + 0.65 N + 0.09 DMI ( n = 56, Syx = 2.77, r = 0.88, P < 0.005). It is concluded that recently-burnt chaparral vegetation would provide a maintenance browse for Spanish goats during the spring and summer seasons only.