Refeeding ewe's ad libitum after energy restriction during mid-pregnancy does not affect lamb feed conversion ratio, animal performance and meat quality

摘要

The aim of the study was to evaluate maternal energy restriction in ewes from day 48 to 106 of gestation on pre and post-weaning lambs" performance, carcass and meat quality when their dams were fed ad libitum after the restriction period. Ewes bearing single or twin lambs were assigned to two dietary treatments from day 48 to day 106 of gestation: restricted (R; n = 60) at 60% of their metabolizable energy (ME) requirements, or non-restricted (NR; n = 54) at 100% of their ME requirements. After the restriction period ewes grazed all together ad libitum until weaning. Subsequently, male lambs were placed in a feedlot until slaughter. Ewes body weight was recorded during nutritional treatment application and at weaning. Litter size and lamb sex were recorded, and feed intake and body weight were measured from birth until slaughter. After slaughter, carcass weight and yield, subcutaneous tissue depth (GR site), carcass (CL) and leg length (LL), frenched rack (FR) and leg weights were determined. After 5 days of meat aging, color parameters and Warner-Bratzler shear force were determined on longissimus lumborum muscle. Non-restricted ewes weighed 7.5 kg more than R ewes (P 0.05) at the end of the restriction period. Lamb birth weight (BW) was no affected (P > 0.05) by dams' treatment although male and single lambs had a greater (P 0.05) BW than females and twins, respectively. No significant differences (P > 0.05) were detected on the weaning weight between ewes' feeding treatments or lamb sex. Estimated average milk intake by lambs was not affected (P > 0.05) by dams' treatments and litter size. Lambs born to R or NR ewes did not differ (P > 0.05) in feed conversion ratio (FCR) of milk, while twins were more efficient (P 0.05) than single-born. Male lambs from R and NR ewes did not differ (P > 0.05) in weaning and final weight, feed intake and FCR during the fattening phase. Slaughter and hot carcass weight, carcass yield (CYd), GR, CL and LL were not affected (P > 0.05) by treatment and litter size. Brightness of meat (L* value) was greater (P 0.05) in lambs from R ewes than NR. Ewes restricted at 60% of their ME requirements in mid-gestation seems to have the capacity to compensate any detrimental effects on lamb growth and development if adequate refeeding conditions are provided in late gestation and throughout lactation.