EFFECT OF ZINC ADDITION TO DRINKING WATER ON PERFORMANCE AND BEHAVIOR OF GROWING LAMBS DURING HOT CLIMATE

The aim of the current study was to determine whether adding zinc to water will improve lamb performance and behavior during a hot climate. In this experiment, twenty seven lambs were housed indoor in individual pens (1.50 x 1.30m). Zinc was added to the fresh drinking water in three different levels namely T 1 (0 mg Zn/day), T 2 (36 mg Zn/day) and T 3 (72 mg Zn/day). Rumination (m/h), feeding time (m/h), number of visiting feeds (n/h), standing time (m/h), lying time (m/h) and standing bouts (n/h) were recorded three times a day by visual observation. Dry matter intake (kg/d), drinking water intake (litter/day), daily live weight gain and feed conversion ratio were also recorded. The current results indicated that rumination, feeding duration, and the visiting feed number were significantly (P ≤ 0.05) higher in T 2 than T 1 and T 3 groups. However, no-differences were noticed among T 1 , T 2 and T 3 groups regarding standing time, lying time, standing bouts, dry matter intake, water intake, daily live weight gain, and feed conversion ratio. In conclusion, adding zinc to fresh drinking water improved rumination, feeding duration and the feed visiting number.


INTRODUCTION
It is well recognized that hot weather has a negative impact on lamb performance and behavior (3, 12 and 20); this could lead to a tremendous economic loss for lamb production. One of the major problems facing lamb performance and behavior during hot climate is the heat stress resulting from high ambient temperature and solar radiation, causing the effective environment temperature to exceed the thermo-neutral zone, particularly during the summer season (19). Heat stress reduces animal feed intake (37), rumination time, digestibility and changes in water intake, causing a reduction in their productivity, including body weight, reproductive performance and milk production (14, 16, 34 and 36). Heat stress can affect lamb's behavior and performance by reducing antioxidant defense or overproduction of free radicals and reactive oxygen species (6, 8 and 24). The metabolism process in the body is constantly generating the reactive oxygen species (ROS; 23), which considered as a major reason for causing oxidative stress (30). Reduction of oxidative stress could help lamb performance improvement (1 and 28). Several nutritional management approaches have been used to reduce heat stress and improve farm animals' performance and behavior. The adverse effects of environmental stress can be decreased by antioxidant nutrient supplementation, mainly Zinc (28 and 30) and improve lamb behavior. In addition, zinc is known to affect animals' growth and immune system by influencing enzyme activity (17). Zinc is also required for the structural and functional integrity of over 2000 transcription factors (31). Furthermore, studies on the effect of adding Zn on nutrients digestibility and ruminal fermentation is scarce (15), and, where available, results are inconsistent. However, in this regard, Salama et al. (25) revealed that dietary Zn increased the digestibility of dry matter (D.M.), organic matter and crude protein (C.P.) for goats. Previous studies used several methods for heat stress alleviation and improved farm animals' performance, including feeding strategies and management (35). However, there was lake information about using zinc supplement to reduce heat stress effect on performance and behavior of Iraqi native lamb. Therefore, the objective of the current study was to determine the influence of different levels of zinc added to drinking water to alleviate the impact of heat stress on lamb performance and behavior during hot climate.

MATERIALS AND METHODS
This study was conducted during the period 16 th July 2020 and 3 rd September 2020 at the Animals Farm Project, Department of Animal Production, College of Agricultural Engineering Sciences, University of Duhok. Ethical approval of the research protocol was obtained from the Ethics Committee of the Department of Animal Production, College of Agricultural Engineering Sciences, University of Duhok. Experimental animals Twenty seven lambs aged 8 ± 1.1 months with a 26.0 ± 3.0 kg live body weight were used at the farm pertaining to the Department of Animal Production. The lambs were housed indoor in individual pens (1.50 x 1.30m) in randomized blocks on sawdust. The lambs were moved into the study area one week before data collection for adaptation. After the adaptation period, two kg of a total mixed ration (TMR; see Table 1) was offered daily at approximately 08:30 a.m. and 5:00 p.m. for ad libitum availability using individual clean plastic buckets. The remaining feed was removed daily, and the plastic buckets were cleaned prior to RMR was allocated. Water was offered ad libitum daily using the plastic buckets. Samples of TMR (0.5 kg) were collected weekly for chemical composition analysis. The nutrient content of the ration composed of dry matter (88.5%), energy (280 kcal/kg DM), crude protein (16% DM), ether extract (2.5% DM), neutral detergent fiber (36.4% DM) and ash (4.8%).

RESULTS AND DISCUSSTIONS Rumination and feeding behavior:
There was an effect of time (P ˂ 0.05) on rumination (m/h), feeding duration (m/h) and the number of visiting feed (n/h; Table 2, 3 and 4). Rumination, feeding duration and number of visiting feed were declined with the experiment progress; however, the lambs in T 2 group had higher values of the above mentioned measurements. There was an effect of Zn addition to drinking water on rumination (m/h), feeding duration (m/h) and the number of visiting feed (n/h; Table 2, 3 and 4), respectively. The T 2 group exhibited rumination (m/h; P < 0.001), feeding duration (m/h; P < 0.001) and the number of visiting feed (n/h; P < 0.010). The present study results revealed that zinc addition to drinking water had beneficial for the lamb rumination and feeding behavior during heat stress. Rumination time is a good feeding behavior marker to distinguish efficient and inefficient lambs (18). The present study found that the rumination period (m/h; P < 0.001) was greater in T 2 lambs' group than T 1 and T 3 groups at weeks 2, 3, 4 and trended to be higher at week 5. These results are in accordance with those reported by Jenkins and Hidiroglou (11) and Ott et al. (21), who found an increase in zinc intake with food increased rumination in ruminant lamb. Moreover, the present study revealed that feeding duration (m/h; P < 0.001) was also longer in the T 2 lambs' group compared to T 1 and T 3 groups. This result is consistent with the previous finding of Underwood et al. (33), who found that lamb's fed diet with zinc supplementation had longer a higher feed intake. Furthermore, the results show that the numbers of visiting feed (n/h; P = 0.010)) were more in the T 2 lambs' group than T 1 and T 3 groups. Rice et al. (23) observed that the number of visiting feed was reduced during heat season and reported a positive relationship between the number of visiting feed and cortisol concentration in lamb. To the best of our knowledge, the present study is the first to report the effect of adding zinc to drinking water on lamb feeding duration the numbers of visiting feed during a hot climate. An increase in rumination period, feeding duration and the number of visiting feed may be due to that drinking zinc with water reduces the impact of heat stress on the lamb (30). Standing time, lying time and standing bouts: There was an effect of time (P ˂ 0.05) on Standing time (m/h), lying time (m/h) and standing bouts (n/h; Figure 1, 2 and 3). There was a fluctuation in standing time, lying time and standing bouts with experiment progress.
There was no effect of adding zinc to drinking water on standing time, lying time and standing bouts ( Figure 6 and Table 3 (27) found that standing up is a general response of the animal to heat stress. Spending greater time standing with inconstant standing bouts during hot climate designates the level of heat stress experienced by the lambs indicated to increase the efficiency of body heat loss through amended airflow (29). These results were also irrelevant to results observed by previous studies (17)and (26), which found lower activity levels in lambs than the present. These differences may be due that lamb activity was recorded by visual observation, and lambs were fed zinc addition to drinking water; however, other studies recorded lamb activity by small behavior monitoring devices called IceTags (IceTag sensor, IceR-robotics, Edinburgh, U.K.), which were more accurate and sensitive than visual observation (23). However, there was no published information on the effect of zinc addition to the drinking water on lamb sating bouts. The effect of hot climate on lamb behavior may be that heat stress changes lamb activities and intensifies stresses experienced by lambs during hot climate, which leads to increased time and energy spent in behaviours to stabilize body thermoregulation (13).

Dry matter intake, water intake, body weight gain and feed conversion ratio:
There was an effect of time (P ˂ 0.05) on feed dry matter intake (DMI), water intake, and lambs live weight (Figure 4, 5 and 6). There was a fluctuation in feed dry matter intake (DMI) and water intake, while lambs weight had increased with experiment progress. There was no effect (P ˃ 0.05) of zinc addition to the drinking water on feed dry matter intake, water intake and lambs live weight ( Figure 6 and Table 3 and 4). In addition, zinc addition to the drinking water had no effect on the average dry matter intake, water intake, daily body weight gain and feed conversion ratio (  15), who found that dry matter intake was significantly higher for the lambs fed the diet supplemented with zinc. There was also no effect (P = 0.916) of Zinc addition on the average water intake (L/d) in the current study. In addition, there was no effect of zinc addition to the drinking water on the average daily body weight gain (g/d; P = 0.614) between T 1 , T 2 and T 3 lambs. These results disagree with the previous study (15), who reported that average daily weight gain increased significantly with Zn addition and was higher for the lambs fed with Zn than the control diet lambs. The results of the current study are also in contrast to those showed (Garg et al., 2008), who reported that the average daily gain of lambs during 150 days of experimental feeding zinc supplementation was significantly higher compared to the control. Furthermore, feed conversion ratio (FCR; kg feed/1kg gain; P = 0.389) was also not different between T 1 , T 2 and T 3 lambs. Although the number of feeding bouts in the present was higher in T 2 than T 1 and T 3 lamb groups, feeding bouts may not be a direct measure of feed intake and conversion ratio (23). Similarly to the present study, Mallaki et al. (15) found that ZnS supplementation had no effect on feed conversion ratio compared to the control group.        In contrast to the current study, previous studies Underwood et al. (33) and Ott et al. (21) also found improved feed conversion ratio in finishing lambs fed organic Zn compared to the control group. It is documented that the bioavailability of organic zinc is higher than inorganic (7,9 and 15). The available source of zinc in the local markets that supplemented in the current experiment was inorganic. This could be the reason that there was no effect of zinc supplementation on dry matter intake, feed conversion ratio and daily weight gain.

Conclusion
Adding Zinc to the fresh drinking water was significantly improved rumination, feeding duration and the number of visiting feed in lambs during heat stress. However, this addition with water had no effect on standing time, lying time, standing bouts, dry matter intake, water intake, daily body weight gain and feed conversion ratio in lambs during hot climate. This means that inorganic zinc supplementation with water had no effect on lamb performance improvement during hot climate.