Effect of dietary forage: concentrate ratio on growth performance and carcass characteristics of growing Baladi kids

The objective of this study was to determine the effect of forage: concert trate ratio on growth performance, nutrient digestibility and carcass characteristics of growing Baladi (black) kids. Thirty-two male kids (initial body weight = 15.3 +/- 1.3 kg) were assigned randomly to four dietary treatments (8 kids/treatment) in a completely randomized design. Experimental diets were: (1) high forage (HF); (2) medium high forage (MHF); (3) medium low forage (MLF); (4) low forage (U), and contained 60:40, 45:55, 30:70 and 15:85 forage:concentrate ratios, respectively. Metabolizable energy contents were 2.39, 2.56, 2.73, and 2.90 Mcal kg(-1) for the HF, MHF, MLF, and LF diets, respectively. Diets were isonitrogenous (16% CP) and were fed twice daily for 68 days. Dry matter intake for kids fed the MLF diet was greater (P < 0.05) compared with kids fed the HF, MHF and LF diets. Metabolizable energy intake was higher (P < 0.05) for kids fed the MHF, MLF and LF diets (average = 1.73 Meal day(-1), S.E. = 0.1) compared with kids fed the HF diet (1.40 Meal day(-1)). Average daily gain (ADG) for kids fed the LF diet (179 g day(-1)) was greater (P < 0.05) compared with kids fed the HF diet (78 g day(-1)). Kids fed the MHF and MLF diets had intermediate ADG (average 116 g day(-1)). Dry matter, OM and CP digestibilities increased (P < 0.05) with increasing the concentrate portion of the diets. The NDF and ADF digestibilities decreased (P < 0.05) with the increasing levels of concentrates in the experimental diets. Kids fed the HF and MHF diets had the greatest NDF and ADF digestibility (average = 60.1 and 53.8%, respectively). Hot and cold carcass weights were greater (P < 0.05) for kids fed the LF diet compared with kids fed the HF diet. Kids fed the MHF and MLF diets had intermediate hot and cold carcass weights. Kids fed the LF diet had higher (P < 0.05) liver weights compared with kids fed the MLF diet. On the other hand kids fed the MLF diet had greater (P < 0.05) liver weights (498 g) compared with kids fed the HF diet (387 g). Kidney, spleen, heart and skin weights were not affected by the dietary treatment. Ruminal pH for kids fed the HF diet (6.92) was greatest (P < 0.05) and declined linearly for the MLF and LF diets to 6.09. This study indicates that increasing the concentrate portion of fattening diets increases ADG, improves feed efficiency and carcass characteristics of growing Baladi kids. Higher concentrate diets reduced production costs compared to higher forage diets as well. (C) 2004 Elsevier B.V. All rights reserved.