​Growth Performance and Biometry of Nellore Brown Lambs from Birth to Weaning under Different Systems of Rearing

In India, Sheep are raised on natural vegetation, common grazing lands, waste lands, stubbles of cultivated crops and top feeds. In developing countries like India, the farming system could be categorized as Intensive, Semi-intensive and Extensive system of rearing. The contribution of small ruminants is highly important in rural areas (Ramesh et al., 2012). The most important factor for adoption of type of farming system are climate and regional conditions but the cost of production is the most significant factor affecting the success of the system. Sheep need fewer capital to expand and provide an alternative source of income for marginal farmers (Arora et al., 2016).

Of the three strains in Nellore breed, Nellore brown is popular amongst the farmers due to its hardiness and better adaptability to the very hot and humid climatic conditions. Sheep farmers are evincing keen interest in intensive system of rearing of Nellore brown sheep, on account of shrinking grazing lands, changes in the cropping patterns and poor pasture quality. Presently very little information is available on performance of Nellore brown sheep under different systems of rearing. Keeping in view of the shrinking grazing resources and increasing popularity of Nellore brown sheep, the present study is planned to know the performance of the Nellore brown sheep in the different systems of rearing.

Animals
 
Sixty Nellore brown ewes (1.5 - 2 years) were selected from Sheep unit, Livestock Research Station, Mamnoor, Telangana for the present study. Three rams of average 2.5 years age were selected for tupping of ewes during the study period. The animals were housed in well ventilated shed made up of asbestos sheet roofing with morum flooring and maintained under hygienic conditions. The animals were provided with bore well water ad libitum for drinking purposes. The waterers were cleaned every day and filled with fresh water in the morning and evening. The ewes were dewormed at the starting of the study. Prophylactic measures against Sheep pox, Enterotoxaemia, Pests des petits ruminants, Blue tongue, Hemorrhagic Septicemia, endo and ecto parasitic infections were carried out as per the institution calendar to ensure animal health conditions throughout the study period. The estrous ewes were identified by teaser rams in the morning and evening hours. The separated estrous ewes were tupped by designated rams and date of tupping was recorded.

The lambs born (G1- 14, G2 -14 and G3 - 12) in each systems of rearing were used to study the growth performance and biometry of lambs. The lambs in intensive system of rearing kept along ewes throughout the day. In semi-intensive and extensive system of rearing, the lambs kept along with ewes in the sheds except during the grazing hours.
 
Body weight recording
 
The body weight of lambs at birth were recorded within 24 hours after lambing. The body weight of the lambs at different fortnights were recorded at 7.30 - 8.30 am in the morning by using platform balance. The weight of the lambs were recorded at 15^th, 30^th, 45^th, 60^th, 75^th and day weaning i.e 90^th day.
 
Biometry of lambs
 
The biometric measurement of lambs were measured in centimetres with the help of a flexible measuring tape. Pin shoulder length was measured from the shoulder point to pin bone. Height at withers was measured from the ground to the level of withers. Heart girth was measured as circumference around the chest just behind the point of elbow. Paunch girth was measured as circumference of the body just before the hind legs.
 
Experimental procedure
 
The study was conducted for a period of more than 1 years from March 2019 to June 2020. All 60 ewes selected for the study was allotted to three rearing systems i.e Intensive (G1), Semi- intensive (G2) and Extensive (G3) system by using complete randomized design (3x20). In G1 group, the ewes were kept in the shed throughout the day  provided with farm grown chaffed green fodders (APBN, CO-3 and 4, Super Napier, SSG and Hedge lucerne which ever available in the farm) in the morning and evening time, concentrate feed @ 1% of their body weight offered only in the evening time and not sent for grazing. In G2 group, the ewes were sent for grazing for about 6 hours per day and offered 200 grams of concentrate feed in the shed in the evening time.  For G3 group ewes no concentrate feed were offered in the shed and sent for grazing for 8-10 hours per day. The concentrate feed offered to the ewes in G1 and G2 group contain CP - 17.3 per cent, TDN - 72 per cent. The statistical significance of body weight and biometry of lambs were analyzed as per the methods described by Snedecor and Cochran (1994).

Body weight gain
 
The lower birth weight of lambs in G3 (Table 1) group might be due to thermal and nutritional stress during pregnancy period. These results were similar to findings of (Chaturvedi et al., 2006), (Chaturvedi et al., 2010), (Idris et al., 2010), (Sultana et al., 2011), Kumar and Vasanthakumar (2016) and (Kumar et al., 2017d) have reported that the birth weight of lambs was higher in supplemented ewes than grazing ewes.



In the present study, the mean weaning weight of lambs in G1 group was significantly (P<0.01) higher followed by G2 and G3 groups, which could be the result of lambs getting sufficient quantity of quality milk from ewes in intensive system. The results of the present study were not in agreement with Sultana et al., (2011), however (Sahoo et al., 2016) reported that the lambs born to ewes fed with concentrate feed during late gestation had higher weaning weights than lambs from ewes only on grazing. In contrast, (Jalajakshi et al., 2017) reported slightly higher weaning weight of Nellore brown lambs in semi-intensive system of rearing.

The weaning weight of the lambs reared in different systems in the present study was similar to the findings of (Raman et al., 2003), (Mishra et al., 2004) in Ganjam sheep and (Kumar et al., 2017c) in Nellore jodipi sheep, but higher weaning weights were reported by (Lalit et al., 2016) in Harnali sheep.
 
Average daily gain
 
In the present study, the ADG of lambs was significantly (P<0.01) higher in G1 group (Table 2) from birth to weaning and these results were supported by Bharambe and Burte (2012). Further, the overall mean ADG of lambs in the study was higher than those reported by (Devendran et al., 2009), (Sivakumar et al., 2009), (Balasubramanyam et al., 2010) and (Dass et al., 2016): lower than (Mandal et al., 2012) and similar to (Lalit et al., 2016), (Kumar et al., 2017a) and (Reddy et al., 2017a).


 
Biometry of lambs from birth to weaning
 
Pin shoulder length (cm)
 
The average pin shoulder length of lambs at birth in G1, G2 and G3 group was 22.75±0.15, 22.42±0.11 and 22.31±0.12, respectively (Table 3). The present study values were similar to the findings Mondal and Kakati (2010) and (Dass et al., 2012). Further, (Mishra et al., 2004) and (Tailor and Yadav 2011) reported slightly higher at birth because have considered pin shoulder length measured  up to one month age as pin shoulder length at birth. There was significant (P<0.01) difference in the pin shoulder length of lambs at the time of weaning in three systems of rearing and the findings of the present study are similar to the average pin shoulder length at weaning observed by (Mishra et al., 2004).


 
Height at withers (cm)
 
The mean height at withers of lambs at birth in G3 group was lower than G2 and G1group as the pregnant ewes in extensive system were not provided with supplemented feed and forage which leads to less nutrients available for foetal skeletal development. (Mishra et al., 2004) and (Dass et al., 2012) have reported similar birth height at withers in lambs of Ganjam and Muzzffarnagari breeds, respectively reared in farmers flocks.

The height at withers of the lambs at the time of weaning in G1 group was significantly (P<0.01) higher than other two groups. But, the gain in height at withers of lambs in G1 group from birth to weaning had no significant (P<0.05) difference with G2 and the means of G2 and G3 groups were comparable (Table 4). (Mishra et al., 2004) and Mondal and Kakati (2010) have reported a lower height at withers of lambs than the results of the present study at 3 months of age and could be due to the fact that Nellore breed is  the tallest among sheep breeds in India  (Yadav et al., 2017).


 
Heart girth (cm)
 
The heart girth of lambs at birth in G1and G2 group was significantly (P<0.01) higher than the G3 group (Table 5). This was due to more bony growth along with body weight as a result of better nutrients availability during pregnancy in ewes. (Dass et al., 2012), Tailor and Yadav (2011), Mondal and Kakati (2010) and (Mishra et al., 2004) who have also reported similar heart girth values at birth of the lambs.



At the time of weaning, the mean heart girth of lambs in G1 group was significantly (P<0.01) higher than G2 and G3 group due to more body weight gain. The findings of (Mishra et al., 2004), Tailor and Yadav (2011) and (Dass et al., 2012) revealed similar values of heart girth of lambs at 3 months age in different sheep breeds.
 
Paunch girth (cm)
 
The mean paunch girth (cm) of lambs from birth to weaning in G1 group had non-significant (P<0.05) difference with G2 group (Table 6). The result of the present study was in agreement with (Chaturvedi et al., 2003) who have observed non supplemented group had no significant difference with supplemented group in paunch girth. (Arora et al., 2007) observed higher paunch girth value than present study.

The body weight gain, average daily weight gain was statistically higher in intensive system rearing than semi intensive and extensive system of rearing. The biometrical measurements of lambs were lower in the extensive system of rearing than two other systems might be due to milk from the ewes in the extensive system was not sufficient to meet the growth rate of the lambs.

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