EFFECT OF DRAUGHT WORK ON BODY WEIGHT GAIN, BLOOD BIOCHEMICAL CHANGE, CARCASS CHARACTERISTICS AND MEAT QUALITY OF HARARGHE HIGHLAND BULLS

Abstract

Livestock, particularly cattle, play a vital role in the Ethiopian economy and agricultural activities. The use of draught animals is integral to productivity and food security in the country's diverse agro-ecology. However, the sustainability of draught animal-based agriculture faces challenges in the context of feed availability and nutritional adequacy during periods of intense draught work, which consequently affects animal performance, and beef quality. Thus, this study aimed to assess the effects of draught service on feed intake, daily weight gain (ADG), feed conversion efficiency (FCE), body condition score (BCS), biochemical change and it’s nutritional implications. Moreover, carcass and meat characteristics, and qualities of the primal meat cuts: Supraspinatus (SS), Latissimus dorsi (LD), Longissimus-dorsi (LDM), and Semitendinosus (ST) muscles were evaluated. Twelve bulls of Hararghe highland were divided into three groups of four based on their initial body weight (IBW). They were then allocated to three treatment durations: control (0), 4, and 6 hours, considering their height within the group, using a complete randomized design (CRD). The bulls in the experiment were fed according to their daily net energy requirements within their respective groups. Feed intake was calculated based on the differences between feed offered and refused on a dry matter (kg DM) basis. Body weight (BW) measurements and BCS estimations were done once a week. ADG was calculated as the BW difference between consecutive weeks divided by the number of days. FCE was expressed as the ratio of kg ADG to daily dry matter intake (kg DMI/d). Blood samples were collected from the jugular vein before work in the morning at the initial, middle, and end of the experiment. Feed composition was analyzed once a week, and Cobas Integra 400 Plus was used to measure the concentrations of metabolites in serum. All bulls were slaughtered at the end of the experiments for beef quality evaluation. IBW and BCS, and daily dry matter intake (kg DMI/d and g DMI/d/kgW0.75) of the bulls were evaluated using analysis of variance (ANOVA); FCE was subjected to the mixed model xvi procedure, while weekly ADG and BCS, and blood metabolite concentrations over test days (TD) were analyzed using a mixed model procedure with covariate (s); Carcass characteristics, meat yield, and meat quality attributes were subjected to the covariance analysis (ANCOVA) procedures in SAS-JMP Pro 17 software. The results of the study revealed that, draught work hour (WH) did not have a statistically significant effect on daily grass dry matter intake (kg DMI/d and g DMI/d/kgW0.75) (p > 0.05), however total kg DMI/d of the higher concentrate supplemented (4 and 6 hours) groups was significantly increased compared to the less supplemented (none-working) group (p < 0.05). ADG of working bulls were significantly lower regardless of kg DMI/d, and they were also less efficient (P < 0.05) in converting feed into body mass compared to non-working bulls. The ADG of the bulls and FCE, were notably affected by the experimental weeks (P < 0.05), with the highest growth rates and feed efficiency observed in the 2nd week and the lowest in the 3rd week. Conversely, the BCS remained consistent across the weeks, regardless of both the kg DMI/d and the initial BCS. The study also found a strong correlation between ADG and FCE (r = 0.98). The concentrations of glucose (GLU, mg/dL), total protein (TP, g/dL), and blood urea nitrogen (BUN, mg/dL) in the working groups were not changed compared to their control counterpart (P > 0.05). However, calcium (Ca, mmol) and phosphorus (P, mmol) levels decreased significantly in bulls that work for six hours a day (p < 0.05), while the bulls in the four-hour working group did not exhibit any noticeable difference from the bulls that were subjected to non-work and work for 6 hours a day, in the case of Ca. Hot carcass weight (HCW), chilling loss, total edible and nonedible offal’s, fat thickness (FT), deboned meat yield (kg), meat to bone ratio, muscle distribution, and KPH% (kidney, pelvic, and heart) fat were not affected by draught work (P > 0.05). A WH × kg DMI/d interaction was significant for LD lightness (L*) and LDM chroma (C). Draught WH did not have significant effect on ultimate pH, color, WHC, and tenderness (WBSF) except in ST muscle L* of the six hour working bulls. From the result of the study, it was concluded that, draught work hour did not have a marked impact on the performance and quality of beef except Ca and P concentration provided that daily energy requirement satisfied