Respostas nutricionais e bioeconômicas de ovelhas mestiças santa inês em confinamento submetidas a redução da oferta hídrica

Abstract

Water scarcity is an alarming problem affecting humans and livestock worldwide, especially in arid and semi-arid regions. The native and naturalized sheep of these regions have developed adaptive mechanisms that allow them to produce in situations of water scarcity. The objective of this study was to evaluate the effect of reduced water supply on nutrient intake and digestibility, ingestive behavior, water and nitrogen balance, and bioeconomic performance (performance and economic indicators) of sheep under confinement. Thirty-two Santa Inês crossbred ewes with a live weight of 32.2 ± 7.4 kg and age of 2.3 ± 0.99 years were used. They were distributed in an entirely randomized design with four treatments (ad libitum water (Control - 100% intake), 80; 60 and 40% supply from the control group) and eight repetitions per treatment. The experiment lasted 72 days (14 for adaptation and 58 for data collection). Variables were subjected to normality test and regression analysis using PROC REG of the Statistical Analysis System, effects were considered significant when P>0.05. Nutrient intake and digestibility coefficients, mineral intake, ingestive behavior and performance were not influenced by water offers (P>0.05). A linear decreasing effect was observed for free water intake, total water intake (P<0.001), total urine output (P=0.008), water excreted via urine (P=0.006) water excreted via faeces (P=0.006), total water loss (P<0.001), water absorbed (P<0.001), for the ratios FWI/DMI, FWI/CPI and FWI/NDFI (P<0.001) and nitrogen excreted via faeces (P=0.002). There was an increase of 5.84% and 7.46% in feed costs at 60% and 40% water supply, respectively. There was a decrease in water costs with the reduction of water supply and an increase in effective operational costs, effective total operational costs and total costs, in water supply of 60% and 40%. A decrease in gross income, gross margin, net margin, profit, and profitability was observed with the 60% water supply and an increase in gross income with the 40% supply. The break-even cost values were similar among the four water offers. The cost benefit ratio in all offers was above 1. In conclusion, reducing water supply levels did not affect nutrient intake and digestibility, ingestive behavior, water and nitrogen balance, and performance. Furthermore, the proposed rearing system, regardless of the water supply level is economically feasible and can be adopted according to water availability in similar conditions of the present study.