EFFECTS OF MANAGEMENT SYSTEMS ON PHYSIOLOGICAL AND BIOCHEMICAL BIOMARKERS OF STRESS, PRODUCTIVITY, AND REPRODUCTIVE PERFORMANCE OF DJALLONKÉ SHEEP

Abstract

Four related studies were conducted to evaluate the effect of different sheep management system on biomarkers of stress, productive and reproductive performance of Djallonké sheep in northern Ghana. In the first study, a resource-based assessment of sheep management systems was conducted to assess the available production resources and production practices under the various management systems and to highlight potential stressors faced by sheep under the different management systems. The study used a structured questionnaire and farm observations to obtain data from 176 sheep farmers in the Tolon, Kumbungu, Savelugu, Sagnarigu and Tamale districts of the Northern Region. The second study assessed farmers’ perceptions of factors that constitute stressors in sheep production environment as well as their consequences and possible ameliorative measures. In the third study, physiological, biochemical, and hormonal adaptive profiles were monitored under the different management systems to establish stress indicators linked to the potential stressors identified previously. In the final study 12 representative flocks were followed to monitor the performance of sheep under each of the management systems. The flocks were monitored over the course of a year and their feed intake, growth rate and reproductive parameters were assessed. The different management types identified were: the extensive, semi-intensive, intensive, and tether-extensive system used by 41.5%, 38.1%, 6.3% and 14.2% of the farmers, respectively. The sheep raised in the more extensive systems (extensive and tether-extensive systems) grazed only natural pasture whose CP content significantly (p<0.05) declined from 15.1% in the rainy season to 5.3% in the dry season. Within the same period, digestibility also significantly (p<0.05) dropped from 57.4% to 32.7%. These conditions could therefore predispose these sheep to nutrition stress. The sheep raised extensively were also persistently exposed to temperature humidity index (THIs) greater than the threshold (>25), where sheep are comfortable in their environment. The sheep under the more extensive environments were exposed to comparatively higher (p<0.001) mean daily temperatures and THIs (32.3 ℃ vs 30.2 ℃) and (29.8 vs 28.0), respectively, than those under the intensive system which were housed and provided with shade. Additionally, orthodox veterinary health care was not offered to sheep under the extensive and tether-extensive systems, unlike for sheep under the intensive and semi-intensive systems where farmers sought veterinary interventions. The study concluded that sheep under the more extensive systems were exposed to more stressors (heat, nutrition, disease) compared to sheep under the intensive and semi-intensive management systems. All the sheep farmers held a strong perception that poor nutrition, poor water availability and diseases were major stressors. Most farmers also largely agreed that extreme temperatures, poor housing conditions, plastics and toxicants constituted sources of stress. The farmers linked these stressors to various production losses such as poor growth, weight loss, poor reproductive performance, and high mortalities. The sheep reared under the more extensive systems showed elevated thermoregulatory parameters compared to sheep raised under intensive management (p<0.001). Respiratory rate (RR) was highest (p<0.001) in extensive sheep and lowest in intensive sheep (85.4 vs 77.1, respectively). This pattern was repeated for pulse rate (PR) (91.8 vs 81.6), rectal temperature (RT) (39.24 vs 39.07) and panting score (PS) (2.28 vs 2.07). Serum cortisol levels significantly differed (p<0.001) between management system, with serum cortisol measurements of 25.7ng/ml, 33.4ng/ml, 52.9ng/ml and 65.7ng/ml for the intensive, semi-intensive, extensive, and tether-extensive systems, respectively. Hair cortisol similarly differed significantly (p<0.001) between the different management systems, with measurements of 18.8ng/mg, 21.6ng/mg, 30.7ng/mg and 36.9ng/mg being recorded for the intensive, semi-intensive, extensive, and tether-extensive systems. Haematological profiles showed higher (p<0.001) Hb, PCV and RBCs for the sheep under intensive management. Serum biochemical profiles showed superior (p<0.001) glucose levels for sheep under the intensive and semi-intensive systems (3.84g/dl and 3.41g/dl, respectively) compared to the extensive and tether-extensive systems (2.58 and 2.55g/dI, respectively). Similarly, total protein (TP) was significantly (p<0.001) higher among the intensively managed sheep (8.1g/L) compared to the semi-intensively managed ones (7.36g/L). The extensive and tether-extensive sheep had lower (p<0.001) TP (6.35 and 6.45g/L) compared to the intensive and semi-intensive sheep. Serum albumins, cholesterol, and triglycerides for intensively raised sheep were also significantly (p<0.001) higher than extensive and tether-extensive systems, which had the lowest values for these parameters. Creatinine levels were however, higher (p<0.001) in extensively raised sheep compared to semi-intensive, intensive, and tether-extensive systems. The study revealed that dry matter intake (DMI) differed significantly (p<0.001) between management systems, being higher in intensively raised sheep (780.9g/d) and decreasing through the semi-intensive sheep (590.1g/d) to the extensive and tether-extensive sheep (511.8 and 456.9g/d, respectively). Similarly, organic matter intake (OMI) and crude protein intake (CPI) were significantly higher (p<0.001) in the flocks raised under the intensive system (662.1g/d and 93.6g/d, respectively) while having the lowest intake levels under the extensive (437.8g/d and 37.6g/d) and tether-extensive system (386.5g/d and 31.9g/d, respectively). Body condition scores (BCSs) were also significantly higher (p<0.001) in the intensive group compared to all other groups (semi-intensive, extensive, and tether-extensive system), with tether-extensive sheep having the worst BCS. The lambing rate was significantly higher (p<0.001) in intensively raised sheep relative to the other management systems. Sheep under the extensive and tether-extensive systems had the lowest lambing rate among the different systems (85% vs 74.3%, respectively). Similarly, prolificacy was significantly higher (p<0.001) in intensively raised sheep compared to the semi-intensively raised sheep (1.72 vs 1.16), but both systems had a higher prolificacy compared to sheep raised in the extensive and tether-extensive systems (1.08 vs 1.04). Oestrus duration significantly decreased in trend from the intensive through the semi-intensive to the extensive and tether-extensive systems (33.4h, 30.6h, 26.6h and 24.4h, respectively). Survival rate was higher (p<0.001) in the intensive system compared to the semi-intensive, but both had a higher (p<0.001) survival rate compared to the extensive and tether-extensive systems. It can be concluded from this study that the intensive and semi-intensive systems exposed Djallonké sheep to a less stressful environment than the extensive and tether-extensive systems which produced the worst outcomes in terms of stress indicators and general productive performance. It is therefore recommended that economically viable heat alleviation, nutrition and health interventions strategies be introduced to minimize the stressfulness of the more extensive systems to enhance performance of Djallonké sheep.