Effect of restricted feeding and realimentation on feed performance and carcass characteristics of growing lambs

Abstract

-Forty Najdi ram lambs weighing 26.6±0.3 kg were utilized in this experiment to determine the effects of feed restriction followed by realimentation and body weight at the onset of feed restriction (30 and 36 kg body weights) on performance and carcass characteristics; feeding and restriction levels were ad libitum, 0.75 and 0.60 of the ad libitum intake. All lambs were slaughtered after 14 weeks of experimentation. The results showed that, during the feed restriction phase, average daily gain (ADG) and feed efficiency decreased as the level of restriction increased. During the realimentation phase, the 30 kg lambs gained weights and consumed dry matter (DM) similarly to the ad libitum group, whereas the ADG for the 36 kg lambs of both 0.75 and 0.60 ad libitum groups were 20 and 43.8% faster than the ad libitum group, respectively. At the end of the trial, final body weight and overall ADG of the realimented 30 kg groups were lower than ad libitum group, whereas the ADG of the 36 kg groups were not different compared with the ad libitum group. Although empty body, hot and cold carcass, empty stomach compartments, empty intestines and liver weights for the 36 kg groups were not affected by feed restriction followed by realimentation, weights of visceral fat depots, subcutaneous fat and tail fat decreased much more than those of the ad libitum group. Carcass composition of the realimented 0.75 and 0.60 ad libitum groups tended to have 5.1 and 8.8% less lean tissue than the ad libitum group when the restriction started at 30 kg, respectively. On the other hand, the realimented lambs of both 0.75 and 0.60 ad libitum groups tended to be 5.1 and 2.8% leaner than those of the ad libitum group when restriction started at 36 kg body weight, respectively. Feed restriction of up to 40% for a 5-week period followed by a 4-week period of refeeding in 36 kg lambs is economically feasible and does not offset production.

Effect of different feed restriction regimens on lamb performance and carcass traits

“…Regarding lambs fed ad libitum, lambs held to less than maximal DMI had reduced ADG as a function of the plane of nutrition, thereby resulting in inadequate intake of nutrients required to sustain normal growth and development (Dashtizadeh et al, 2008;Abouheif et al, 2013). During the two-week period of realimentation, lambs had improved ADG (Al-Selbood, 2009; Abouheif et al, 2013) and improved FG (Homem Junior et al, 2007;Shadnoush et al, 2011).…”

“…Regarding lambs fed ad libitum, lambs held to less than maximal DMI had reduced ADG as a function of the plane of nutrition, thereby resulting in inadequate intake of nutrients required to sustain normal growth and development (Dashtizadeh et al, 2008;Abouheif et al, 2013). During the two-week period of realimentation, lambs had improved ADG (Al-Selbood, 2009; Abouheif et al, 2013) and improved FG (Homem Junior et al, 2007;Shadnoush et al, 2011). This higher gain could not be attributed to DMI because intake values were not different between realimented (RR) and control groups, but possibly due to the better FG in realimented lambs and/or the decreased heat production during the restriction and its continuation during realimentation (Yambayamba et al, 1996).…”

“…Several reports have shown that there are no differences in body composition between ad libitum and realimented steers (Rompala et al, 1985) and sheep (Marais et al, 1991). Drouillard et al (1991) found an increase in body fat content, whilst others have reported increases in the lean tissue of the compensated goats (Dashtizadeh et al, 2008) and lambs (Atti and Ben Salem, 2008;Al-Selbood, 2009;Abouheif et al, 2013) in comparison with the controlfed animals. The discrepancies could be due to different intensities and durations of restriction before realimentation, and breed types with different maturity ages (Tolla et al, 2003).…”

“…The response varies according to the breed, duration and severity of restriction, duration of realimentation, quality of the diet and stage of development at the start of restriction (Al-Selbood, 2009). Abouheif et al (2013) found that compensatory growth was better expressed when feed restriction occurred at 36 than 30 kg body weight in indigenous Najdi sheep from Saudi Arabia. There are conflicting results about the amount of feed intake after a period of feed restriction; some authors reported a significant increase in feed intake (Homem Junior et al, 2007;Dashtizadeh et al, 2008), whilst others reported no significant difference (Mahouachi and Atti, 2005;Shadnoush et al, 2011).…”

“…To mitigate the increasing costs of feeds and to make lamb production profitable, efforts have been made to investigate possible strategies to reduce the cost of production through the imposition of feed restriction followed by compensatory growth (Al-Selbood, 2009;Abouheif et al, 2013). Compensatory growth is manifested in the feedingestion ability of previously restricted animals to outgain their better counterparts when given free access to good quality feed.…”