Effect of different feeding regimens on energy and protein utilization and partitioning for maintenance and growth in pre-weaned lambs reared artificially1

Abstract

Estimation of metabolizable energy (ME) requirement for maintenance (ME) and growth (ME) in pre-weaned lambs have been limited to milk-only fed lambs. This study aimed to determine energy and nitrogen metabolisability of milk and pellets when fed together, compare the growth and chemical body composition of lambs fed varying levels of pellets in addition to milk, and to estimate ME, ME, and the CP:ME ratio requirements for growth. The study included 32 twin-born Romney-cross ram lambs. Four lambs were slaughtered at 24 h post-partum to estimate initial body composition and the remaining 28 were assigned to 1 of 4 treatment groups of 7. Group 1 was fed milk replacer (MR) only; group 2 was fed MR and allowed ad libitum access to pellets; groups 3 and 4 were offered 30% and 60%, respectively of the average pellet intake of the ad libitum group the previous day while being fed MR. Milk replacer was fed as a proportion of the lamb's live weight (LW). Lambs from each treatment were placed in metabolic cages at 17 kg LW for 4 d to allow for total fecal and urine collection. All lambs were slaughtered at 18 kg LW. The ADG, ADG:ME ratio, stomach and liver weight, and rumen papillae lengths increased ( < 0.05) with increasing pellet intake. Increasing daily ME intake increased ( < 0.05) both daily energy and protein deposition but had no effect ( > 0.05) on fat deposition. However, the total chemical body composition was unaffected ( > 0.05) by dietary treatment. Digestibility of energy and N decreased ( < 0.05) with increasing ME intake. Percent energy and N retained for growth were 96% vs. 71% and 72% vs. 30% for milk and pellets, respectively. The ME and ME values obtained were 0.40 MJ ME/kg LW·d and 13.8 MJ ME/kg ADG, respectively. The CP:ME ratio of MR and pellet was 11.1 and 15.7, respectively. However, a simulation model suggested that lambs require a CP:ME ratio of 13.1 at 5 kg and 10.9 at 18 kg LW, indicating that protein intake may be limiting to lamb growth in early life and in excess by 18 kg LW. In conclusion, increasing pellet intake was associated with decreased N retention. The inclusion of pellets, however, improved the efficiency of ME utilization for growth in pre-weaned lambs and was beneficial for rumen development. The ME was higher than previously recommended values and the CP:ME intake of lambs does not match their requirements which may warrant further studies.

Growth and Body Composition of Artificially-Reared Lambs Exposed to Three Different Rearing Regimens

“…All lambs were fed milk replacer at 2.1 times their maintenance energy requirement based on their LW as per previous studies by our group [ 5 , 6 ]. The maintenance requirement was calculated as ME m = 0.40 MJ/kgLW 0.75 d −1 [ 18 ]. The commercial milk replacer contained 969.8 g/kg dry matter, 262.9 g/kg crude protein (CP), 275 g/kg fat, 56.2 g/kg ash, 350.4 g/kg lactose, 11.4 g/kg calcium, 6.1 g/kg phosphorous, 22.7 MJ/kg gross energy, 21.8 MJ/kg metabolisable energy (ME) and 12.05 g/MJ CP:ME on fresh matter basis (Milligans Feed Ltd., Oamaru, New Zealand).…”

“…Metabolisable energy content was calculated as metabolisability coefficient multiplied by gross energy considering metabolisability coefficient of milk replacer and milk protein concentrate as 0.96 [ 4 ]. To prepare the milk, the powdered milk replacer was mixed with warm tap water at a ratio of 1/4 ( w / w ) [ 4 , 5 , 18 ]. Lambs were bottle-fed five times daily (at 8.00 a.m., 11.00 a.m., 2.30 p.m., 6.30 p.m., and 9.00 p.m.) up to two weeks of age, then four times daily (at 8.00 a.m., 11.00 a.m., 2.30 p.m., and 6.00 p.m.) up to the milk-weaning phase (days 38 to 42) for HFP42 and LFP42 lambs and until the end of experiment for HFP57 lambs.…”

Rumen Development of Artificially-Reared Lambs Exposed to Three Different Rearing Regimens

“…The three rearing treatments were (i) commercial milk replacer fed to 57 d of age plus high fibre concentrate pellets (HFP57, n = 9); (ii): commercial milk replacer, high fibre concentrate pellets, and weaning from milk replacer at 42 d of age (HFP42, n = 9); (iii) high protein milk replacer from 2–16 d of age, followed by commercial milk replacer, low fibre concentrate pellets, and weaning from milk replacer at 42 d of age (LFP42, n = 9). All lambs were provided milk replacer at 2.1 times their maintenance energy requirement [ 15 ], considering maintenance energy requirement (ME m ) as 0.40 MJ/kg live weight (LW) 0.75 d −1 [ 16 ]. The crude protein (CP) and metabolisable energy (ME) contents (expressed as fed basis) of commercial milk replacer powder were 263 g/kg and 21.8 MJ/kg, respectively (Milligans Feed Ltd., Oamaru, New Zealand).…”

Effects of three kinds of different protein-to-fat ratio ingredi-ents on growth, slaughter performance and fat deposition of Small-Tail Han lambs

“…Muscle protein deposition is the major determinant of rapid growth and development in animals [18], the body content of protein, fat, energy and ash for lambs from 5 to 30 kg (kg EBW) ranged from 141.69 to 186.24 g; 24.49 to 158.11 g; 1088.75 to 2451.55 Kcal and 27.55 to 33.70 g, respectively [19,20]. Therefore, regulating the protein to energy ratio is a technique for promoting rapid weight gain in lambs.…”