Development of organs and tissues in lambs raised on Spanish mountain grassland

The present study was conducted to establish the pattern of body development in grass-raised Churra Tensina lambs. Forty-nine single male lambs were slaughtered at three body-weight intervals, according to the commercial categories of suckling (11.1 ± 1.0 kg), light (22.1 ± 0.8 kg) and heavy lamb (32.0 ± 2.9 kg). Non-carcass and carcass components were recorded and the half left carcasses were completely dissected. Lambs showed a low growth rate of main organs in relation to empty body weight (BW) (P < 0.01). Skin+ fleece and liver accompanied the rest of mass growth (P > 0.05). The allometric coefficients of forestomachs and large intestine were higher than that of the small intestine (P < 0.05). Joints related to locomotion had early development (P < 0.01), whereas those belonging to the trunk grew at faster rates than did carcass weight (P < 0.01). The fatty tissues had increased growth coefficients (P < 0.01), whereas bone and lean coefficients decreased (P < 0.01) with increasing carcass weight. Intermuscular fat attained greater growth rates in lambs slaughtered at light BW than in heavy lambs (P < 0.01). However, the former group displayed lower relative growth of pelvic-renal, subcutaneous and abdominal fat than the latter (P < 0.01). This trait might reflect improved investment of dietary energy towards deposition of adipose tissue through the increased digestive tract capacity.