F.L. Fluharty, K.E. McClure, D.D. Clevenger, and G.D. Lowe
Department of Animal Sciences
Sixty Targhee ewes were used in an experiment to examine the effects of ionophore addition to alfalfa haylage-based diets fed at or below the maintenance energy requirements of ewes during gestation and lactation. There were no differences (P > 0.10) in the ewes' weights at lambing or average daily gain (ADG) due to energy intake or ionophore inclusion. However, body condition scores (BCS) at lambing were higher (P < 0.05) for ewes fed at 100% compared with those fed at 85% of their energy requirements. Overall, lasalocid increased (P < 0.05) 24-hour milk production of ewes rearing twins to 6.38 pounds compared with 5.08 pounds for the ewes not fed lasalocid. From birth to 7 days of age, ewes rearing twin lambs and receiving lasalocid had lambs that had an 81% greater (P < 0.01) ADG compared with twin lambs from ewes not receiving lasalocid. Overall, twin lambs from ewes receiving lasalocid had a 15% greater (P < 0.05) 28-day weight and a 32% greater (P < 0.05) ADG compared with twin lambs from ewes not receiving lasalocid. Twin lambs from ewes being fed the 100% energy level had a 41% greater ADG compared with twin lambs from ewes being fed the 85% energy level. Therefore, both the higher energy intake and lasalocid inclusion in ewes' diets resulted in improved lamb performance to 28 days post-lambing.
Lasalocid alters ruminal fermentation by shifting the acetate to propionate ratio toward more propionate (Bartley et al., 1979) and decreases ruminal protein degradation and deamination (Wasichei and Bergen, 1980). Altering ruminal fermentation in this way may be beneficial to pregnant ewes, because the rate of glucose use and the need for gluconeogenic precursors, such as propionate, increases during pregnancy (Thomas et al., 1988a).
Recent studies have found increased reproductive performance in gestating ewes fed lasalocid while grazing on winter range. Thomas et al. (1988a) reported that the percentage of lambs born to ewes fed lasalocid was greater than for ewes not fed lasalocid (145.9 vs 139.6%, respectively). In a later study, Thomas et al. (1990) reported that ewes fed lasalocid had a greater percentage of lambs born per ewe than those not fed lasalocid (120.7 vs 112.1%, respectively), and the lasalocid-fed ewes also produced more total weight of weaned lamb than did the control ewes (25.9 vs 23.4 kg, respectively). These authors speculated that "the higher percentage of lambs born and weaned and the subsequent increase in kg of lamb weaned for those fed lasalocid may be due to reduced embryonic mortality."
Thomas et al. (1988b) reported on the effects of feeding lasalocid to ewes during the last 4 weeks of gestation on blood metabolites, lamb birth weight, colostrum composition, and ewe performance. The ewes were fed in excess of the NRC (1985) energy and protein requirements. These authors found that feeding lasalocid decreased blood urea-N, with minor effects on nutrient utilization and ewe productivity. Maternal nutrient restriction also had been shown to reduce colostrum volume and total yields of lactose, lipid, and protein (Mellor and Murray, 1985), which could influence lamb performance.
The preceding studies involved feeding ewes in excess of their NRC protein and energy requirements. Inclusion of lasalocid, an ionophore, into ewe gestation diets may result in improved nutrient utilization and increased metabolic efficiency. This could result in reduced feed costs without adversely affecting animal performance if used in conjunction with restricted feeding. The objective of the current study was to determine the effects of ionophore addition to diets at or below the maintenance energy requirements of ewes during gestation and lactation.
Sixty Targhee ewes were used in a 2 x 2 factorial experiment with a completely randomized design. Ewes were bred prior to initiation of the trial. At the start of the trial, they were weighed, their body condition scored, and were allotted to one of four treatments. Random allotments within treatments were based upon age, parity, body condition score (BCS), and weight. The four dietary treatments were:
All diets were formulated to meet the animals' requirements for protein (NRC, 1985) to ensure that protein intake did not confound the results (Table 1). The trial started at 7 to 8 weeks of gestation and ended at the time the lambs were weaned. Ewes were weighed every 14 days during gestation immediately prior to feeding at 0800 hours. Additionally, BCS were recorded for each animal at each time of weighing as a subjective measure of nutritional status, using the scoring system of Russel et al. (1969). Within 6 hours following lambing, ewes and lambs were weighed. Milk yields of the ewes were determined on days 7, 14, 21, and 28 of lactation according to the procedure of Palmquist et al. (1977), except that 10 USP units of oxytocin were given intravenously. The ewes and lambs were separated, the ewes were injected with oxytocin and milked, and the milk was discarded. After 3 hours, the ewes again were injected with oxytocin and milked, and the milk samples were collected to estimate daily milk production and composition. Lambs then were returned to the ewes. Milk samples were analyzed for fat and protein (AOAC, 1984). During the lactation phase of the trial, those ewes giving birth to zero live lambs and those giving birth to triplets were not used. Lambs were given access to creep feed starting at day 29 post-lambing. The ewes were weighed on days 28 and 42 of lactation. The lambs were weaned on day 42 of lactation. The number of lambs born, survival percentage, lamb birth and weaning weights, and number of lambs weaned were determined.
Statistical analysis of data was conducted using the GLM repeated measures procedure of SAS (1988) for a completely randomized design experiment with a 2 x 2 factorial arrangement of treatments. Animal was used as the experimental unit.
| Table 1. Diet composition for ewes. | |
| Item | |
| Ingredient | (% DM basis) |
| Alfalfa haylage | 90.000 |
| Ground corn | 8.050 |
| Monosodium phosphate | 1.070 |
| Trace mineral salt1 | 0.500 |
| Vitamin A, 30,000 IU/g | 0.010 |
| Vitamin D, 3,000 IU/g | 0.010 |
| Vitamin E, 44 IU/g | 0.010 |
| Selenium, 201 mg SE/kg | 0.050 |
| Dynamate2 | 0.300 |
| Calculated composition | |
| Crude protein, % | 18.054 |
| Calcium, % | 1.352 |
| Phosphorus, % | 0.521 |
| Potassium, % | 2.019 |
| ME, Mcal/kg | 2.176 |
| NEm, Mcal/kg | 1.325 |
| 1 Contained > 93% NaCl, 0.35% Zn, 0.28% Mn,
0.175% Fe, 0.035% Cu, 0.007% I, and 0.007% Co.
2 Magnesium sulfate and potassium sulfate. Contained 22% S, 18% K, 11% Mg (International Minerals and Chemical, Terre Haute, IN). | |
The effects of energy intake and ionophore inclusion on weights and body condition scores (BCS) of gestating ewes from the initiation of the trial to immediately post-lambing are shown in Table 2. There were no differences (P > 0.10) in the ewes' weights at lambing or ADG due to energy intake or ionophore inclusion. However, BCS at lambing were higher (P < 0.05) for ewes fed at 100% compared with those fed at 85% of their energy requirements. There were no differences (P > 0.10) in final weights or weight loss due to diet.
The effects of energy intake and ionophore inclusion on milk production and composition from ewes rearing single lambs are shown in Table 3. Lasalocid increased (P < 0.05) both 24-hour milk production and the total amount of milk protein on days 21 and 28 and overall compared with ewes not given lasalocid. The effects of diet on milk production and composition from ewes rearing twin lambs are shown in Table 4. Overall, lasalocid increased (P < 0.05) 24-hour milk production to 6.38 pounds compared with 5.08 pounds for the ewes not fed lasalocid. During the first 21 days following parturition, ewes fed lasalocid had a lower (P < 0.05) milk protein percent compared with ewes not fed lasalocid. However, because total milk production was numerically greater when lasalocid was fed, the actual pounds of milk protein produced were numerically higher with lasalocid compared with ewes that did not receive lasalocid. Overall, the 100% energy intake group had a greater (P < 0.05) total production of milk protein compared with the 85% energy intake group.
There were no differences (P > 0.10) in performance of single-born lambs due to ewes' diets (Table 5). However, ewes rearing multiple lambs had an increased demand for milk production compared with ewes rearing single lambs due to the greater total pounds of lambs being reared in multiple birth situations. Earlier research (Gardner and Hogue, 1964; Loerch et al., 1985) has shown that ewes rearing multiple lambs have increased milk production compared with ewes rearing single lambs as a direct result of stimulation of the mammary gland. From birth to 7 days of age, ewes rearing twin lambs and receiving lasalocid had lambs that had an 81% greater (P < 0.01) ADG compared with twin lambs from ewes not receiving lasalocid. Overall, twin lambs from ewes receiving lasalocid had a 15% greater (P < 0.05) 28-day weight and a 32% greater (P < 0.05) ADG compared with twin lambs from ewes not receiving lasalocid. Twin lambs from ewes being fed the 100% energy level had a 41% greater (P < 0.01) ADG compared with twin lambs from ewes being fed the 85% energy level. Therefore, in multiple birth situations, both the higher energy intake and lasalocid inclusion in the ewes' diets resulted in improved lamb performance to 28 days post-lambing.
| Table 2. Main effects of energy intake and ionophore inclusion on weights and body condition scores of gestating ewes from initiation of the trial to immediately post-lambing. | |||||
| Energy intake | Lasalocid | ||||
| Item | 85% | 100% | No | Yes | |
| (Ewes giving birth to one lamb) | |||||
| Initial weight, pounds | 196.90 + 5.70 | 189.10 + 7.10 | 190.10 + 5.70 | 196.00 + 7.10 | |
| Final weight, pounds | 200.80 + 6.00 | 207.80 + 7.30 | 202.50 + 6.00 | 206.00 + 7.30 | |
| Weight change, pounds | 3.80 + 4.00 | 18.60 + 4.90 | 12.40 + 4.00 | 10.00 + 4.90 | |
| ADG1, pound/day | 0.06 + 0.06 | 0.26 + 0.08 | 0.18 + 0.06 | 0.14 + 0.07 | |
| Initial BCS2 | 3.40 + 0.20 | 3.80 + 0.24 | 3.60 + 0.20 | 3.50 + 0.24 | |
| Final BCS, pre-lambing2,3,4 | 2.90 + 0.16 | 3.60 + 0.20 | 2.80 + 0.16 | 3.80 + 0.20 | |
| BCS change2 | -0.44 + 0.28 | -0.13 + 0.34 | -0.81 + 0.28 | +0.25 + 0.34 | |
| Post-lambing weight, pounds | 184.70 + 6.80 | 185.80 + 7.70 | 182.70 + 6.40 | 187.80 + 7.70 | |
| % of initial weight | 93.20 + 1.90 | 98.10 + 2.10 | 95.40 + 1.70 | 95.90 + 2.10 | |
| (Ewes giving birth to multiple lambs) | |||||
| Initial weight, pounds | 197.50 + 4.90 | 208.20 + 5.10 | 205.10 + 5.10 | 200.50 + 4.90 | |
| Final weight, pounds | 208.90 + 5.70 | 224.80 + 6.00 | 218.10 + 6.00 | 215.60 + 5.70 | |
| Weight change, pounds | 11.40 + 2.60 | 16.70 + 2.90 | 13.00 + 2.90 | 15.00 + 2.60 | |
| ADG, pound/day | 0.16 + 0.04 | 0.23 + 0.04 | 0.18 + 0.04 | 0.21 + 0.04 | |
| Initial BCS2 | 3.20 + 0.13 | 3.10 + 0.14 | 3.00 + 0.31 | 3.30 + 0.29 | |
| Final BCS, pre-lambing2 | 2.40 + 0.13 | 2.80 + 0.14 | 2.70 + 0.31 | 2.50 + 0.29 | |
| BCS change2,3 | -0.75 + 0.15 | -0.25 + 0.16 | -0.28 + 0.16 | -0.72 + 0.15 | |
| Post-lambing weight, pounds | 171.30 + 5.70 | 184.30 + 6.40 | 181.00 + 6.40 | 174.50 + 5.70 | |
| % of initial weight | 86.70 + 1.90 | 89.10 + 2.10 | 88.60 + 2.10 | 87.20 + 1.90 | |
| 1 ADG = Average daily gain.
2 BCS = body condition score: 1 = thin; 5 = fat. 3 Energy intake effect (P < 0.05). 4 Lasalocid effect (P < 0.05). | |||||
| Table 3. Main effects of energy intake and ionophore inclusion on milk production and composition from ewes rearing singles. | |||||
| Energy intake | Lasalocid | ||||
| Day | 85% | 100% | No | Yes | |
| (24-hour milk production, pounds) | |||||
| 7 | 3.62 + 0.45 | 3.19 + 0.45 | 3.08 + 0.43 | 3.73 + 0.43 | |
| 14 | 4.00 + 0.45 | 3.16 + 0.45 | 3.13 + 0.44 | 4.04 + 0.44 | |
| 211 | 3.27 + 0.28 | 3.66 + 0.28 | 2.98 + 0.27 | 3.95 + 0.27 | |
| 281 | 3.36 + 0.44 | 3.72 + 0.44 | 2.71 + 0.42 | 4.37 + 0.42 | |
| Overall1 | 3.56 + 0.35 | 3.43 + 0.35 | 2.97 + 0.34 | 4.02 + 0.34 | |
| (Milk fat, %) | |||||
| 7 | 7.60 + 0.86 | 9.60 + 0.86 | 8.60 + 0.83 | 8.60 + 0.83 | |
| 14 | 10.50 + 0.80 | 9.30 + 0.80 | 9.60 + 0.77 | 10.20 + 0.77 | |
| 21 | 10.10 + 0.57 | 9.40 + 0.57 | 10.10 + 0.54 | 9.40 + 0.54 | |
| 281,2 | 10.50 + 0.29 | 9.00 + 0.29 | 10.50 + 0.28 | 9.00 + 0.28 | |
| Overall | 9.70 + 0.39 | 9.30 + 0.39 | 9.70 + 0.37 | 9.30 + 0.37 | |
| (Milk fat weight, pounds) | |||||
| 7 | 0.29 + 0.06 | 0.31 + 0.06 | 0.29 + 0.05 | 0.32 + 0.05 | |
| 14 | 0.41 + 0.05 | 0.30 + 0.05 | 0.30 + 0.05 | 0.41 + 0.05 | |
| 21 | 0.33 + 0.03 | 0.35 + 0.03 | 0.30 + 0.03 | 0.37 + 0.03 | |
| 28 | 0.34 + 0.04 | 0.34 + 0.04 | 0.28 + 0.04 | 0.40 + 0.04 | |
| Overall | 0.34 + 0.04 | 0.32 + 0.04 | 0.29 + 0.03 | 0.37 + 0.03 | |
| (Milk protein, %) | |||||
| 7 | 4.80 + 0.22 | 5.10 + 0.22 | 5.00 + 0.21 | 4.90 + 0.21 | |
| 14 | 4.30 + 0.17 | 4.50 + 0.17 | 4.50 + 0.16 | 4.20 + 0.16 | |
| 21 | 4.50 + 0.18 | 4.80 + 0.18 | 4.70 + 0.17 | 4.50 + 0.17 | |
| 28 | 4.70 + 0.17 | 4.90 + 0.17 | 5.00 + 0.17 | 4.60 + 0.17 | |
| Overall | 4.50 + 0.16 | 4.80 + 0.16 | 4.80 + 0.16 | 4.60 + 0.16 | |
| (Milk protein weight, pound) | |||||
| 7 | 0.17 + 0.02 | 0.16 + 0.02 | 0.15 + 0.02 | 0.18 + 0.02 | |
| 14 | 0.16 + 0.02 | 0.14 + 0.02 | 0.14 + 0.01 | 0.16 + 0.01 | |
| 211 | 0.14 + 0.01 | 0.17 + 0.01 | 0.14 + 0.01 | 0.18 + 0.01 | |
| 281 | 0.15 + 0.02 | 0.18 + 0.02 | 0.13 + 0.02 | 0.20 + 0.02 | |
| Overall1 | 0.16 + 0.01 | 0.16 + 0.01 | 0.14 + 0.01 | 0.18 + 0.01 | |
| (Milk somatic cell count) | |||||
| 7 | 377 + 263 | 783 + 263 | 547 + 253 | 614 + 253 | |
| 14 | 251 + 185 | 654 + 185 | 411 + 178 | 495 + 178 | |
| 21 | 354 + 338 | 957 + 338 | 490 + 325 | 821 + 325 | |
| 28 | 1068 + 726 | 1198 + 726 | 1324 + 698 | 943 + 698 | |
| Overall | 513 + 321 | 898 + 321 | 693 + 309 | 718 + 309 | |
| 1 Lasalocid effect (P < 0.05).
2 Energy intake effect (P < 0.01). 3 Lasalocid effect (P < 0.01). | |||||
| Table 4. Main effects of energy intake and ionophore inclusion on milk production and composition from ewes rearing twins | |||||
| Energy intake | Lasalocid | ||||
| Day | 85% | 100% | No | Yes | |
| (24-hour milk production, pounds) | |||||
| 7 | 5.96 + 0.77 | 7.30 + 0.77 | 5.53 + 0.84 | 7.73 + 0.84 | |
| 14 | 5.58 + 0.45 | 6.00 + 0.45 | 5.32 + 0.48 | 6.27 + 0.48 | |
| 21 | 5.04 + 0.69 | 6.30 + 0.69 | 5.10 + 0.75 | 6.24 + 0.75 | |
| 28 | 4.23 + 0.51 | 5.44 + 0.51 | 4.40 + 0.55 | 5.28 + 0.55 | |
| Overall1 | 5.20 + 0.41 | 6.26 + 0.41 | 5.08 + 0.45 | 6.38 + 0.45 | |
| (Milk fat, %) | |||||
| 72 | 10.50 + 0.72 | 8.30 + 0.72 | 10.10 + 0.78 | 8.70 + 0.78 | |
| 14 | 9.90 + 0.81 | 9.60 + 0.81 | 10.40 + 0.87 | 9.10 + 0.87 | |
| 211 | 11.60 + 0.55 | 11.70 + 0.55 | 10.70 + 0.59 | 12.60 + 0.59 | |
| 28 | 10.30 + 0.65 | 10.60 + 0.65 | 10.10 + 0.70 | 10.80 + 0.70 | |
| Overall | 10.60 + 0.32 | 10.10 + 0.32 | 10.30 + 0.35 | 10.30 + 0.35 | |
| (Milk fat weight, pounds) | |||||
| 7 | 0.62 + 0.07 | 0.55 + 0.07 | 0.56 + 0.07 | 0.61 + 0.07 | |
| 14 | 0.57 + 0.08 | 0.58 + 0.08 | 0.56 + 0.08 | 0.58 + 0.08 | |
| 21 | 0.60 + 0.10 | 0.76 + 0.10 | 0.56 + 0.11 | 0.79 + 0.11 | |
| 28 | 0.43 + 0.06 | 0.58 + 0.06 | 0.44 + 0.07 | 0.58 + 0.07 | |
| Overall | 0.55 + 0.05 | 0.62 + 0.05 | 0.53 + 0.06 | 0.64 + 0.06 | |
| (Milk protein, %) | |||||
| 71 | 4.40 + 0.14 | 4.70 + 0.14 | 4.80 + 0.15 | 4.30 + 0.15 | |
| 141 | 4.30 + 0.15 | 4.20 + 0.15 | 4.50 + 0.16 | 4.00 + 0.16 | |
| 211 | 4.30 + 0.16 | 4.30 + 0.16 | 4.60 + 0.17 | 4.00 + 0.17 | |
| 28 | 4.60 + 0.13 | 4.70+ 0.13 | 4.80 + 0.14 | 4.50 + 0.14 | |
| Overall1 | 4.40 + 0.12 | 4.50 + 0.12 | 4.70 + 0.13 | 4.20 + 0.13 | |
| (Milk protein weight, pounds) | |||||
| 7 | 0.26 + 0.03 | 0.34 + 0.03 | 0.26 + 0.04 | 0.33 + 0.04 | |
| 14 | 0.24 + 0.02 | 0.25 + 0.02 | 0.24 + 0.02 | 0.25 + 0.02 | |
| 21 | 0.21 + 0.02 | 0.26 + 0.02 | 0.23 + 0.03 | 0.25 + 0.03 | |
| 28 | 0.19 + 0.02 | 0.25 + 0.02 | 0.21 + 0.03 | 0.24 + 0.03 | |
| Overall2 | 0.22 + 0.02 | 0.28 + 0.02 | 0.24 + 0.02 | 0.27 + 0.02 | |
| (Milk somatic cell count) | |||||
| 7 | 758 + 435 | 745 + 435 | 1004 + 470 | 499 + 470 | |
| 142 | 398 + 202 | 1022 + 202 | 675 + 219 | 745 + 219 | |
| 21 | 1039 + 624 | 1560 + 624 | 1682 + 674 | 917 + 674 | |
| 28 | 623 + 688 | 1801 + 688 | 1282 + 743 | 1142 + 743 | |
| Overall | 705 + 385 | 1282 + 385 | 1161 + 416 | 826 + 416 | |
| 1 Lasalocid effect (P < 0.05).
2 Energy intake effect (P < 0.05). | |||||
| Table 5. Main effects of energy intake and ionophore inclusion in ewes' diets on lamb performance. | |||||
| Energy intake | Lasalocid | ||||
| Day | 85% | 100% | No | Yes | |
| (Single-born lambs) | |||||
| (Lamb weight, pounds) | |||||
| Birth | 12.06 + 0.67 | 12.66 + 0.67 | 11.79 + 0.63 | 12.93 + 0.63 | |
| 7 | 14.82 + 1.00 | 14.48 + 1.00 | 14.25 + 0.96 | 15.04 + 0.96 | |
| 14 | 18.86 + 1.31 | 19.14 + 1.31 | 18.15 + 1.26 | 19.85 + 1.26 | |
| 21 | 21.84 + 1.51 | 22.00 + 1.51 | 20.80 + 1.46 | 23.04 + 1.46 | |
| 28 | 25.35 + 1.92 | 26.45 +1.92 | 24.05 + 1.85 | 27.75 + 1.85 | |
| Overall | 18.60 + 1.23 | 18.90 + 1.23 | 17.80 + 1.18 | 19.70 + 1.18 | |
| (Lamb ADG1, pound/day) | |||||
| Birth to day 7 | 0.42 + 0.09 | 0.29 + 0.09 | 0.39 + 0.08 | 0.33 + 0.08 | |
| Day 7 to day 14 | 0.53 + 0.05 | 0.58 + 0.05 | 0.50 + 0.05 | 0.60 + 0.05 | |
| Day 14 to day 21 | 0.46 + 0.06 | 0.48 + 0.06 | 0.43 + 0.06 | 0.52 + 0.06 | |
| Day 21 to day 28 | 0.45 + 0.08 | 0.54 + 0.08 | 0.41 + 0.08 | 0.58 + 0.08 | |
| Overall | 0.47 + 0.05 | 0.48 + 0.05 | 0.43 + 0.05 | 0.51 + 0.05 | |
| (Twin lambs) | |||||
| (Lamb weight, pounds) | |||||
| Birth | 12.37 + 0.57 | 12.42 + 0.57 | 12.00 + 0.62 | 12.79 + 0.62 | |
| 7 | 14.02 + 0.63 | 14.60 + 0.63 | 13.39 + 0.68 | 15.13 + 0.68 | |
| 142 | 16.71 + 0.87 | 17.92 + 0.87 | 15.96 + 0.93 | 18.68 + 0.93 | |
| 212 | 17.84 + 0.95 | 20.04 + 0.95 | 17.33 + 1.03 | 20.55 + 1.03 | |
| 28 | 20.31 + 1.25 | 23.38 + 1.25 | 20.18 + 1.35 | 23.51 + 1.35 | |
| Overall2 | 16.26 + 0.82 | 17.65 + 0.82 | 15.77 + 0.88 | 18.13 + 0.88 | |
| (Lamb ADG, pound/day) | |||||
| Birth to day 73 | 0.27 + 0.04 | 0.33 + 0.04 | 0.21 + 0.04 | 0.38 + 0.04 | |
| Day 7 to day 14 | 0.32 + 0.04 | 0.42 + 0.04 | 0.32 + 0.04 | 0.41 + 0.04 | |
| Day 14 to day 212, 4 | 0.20 + 0.04 | 0.37 + 0.04 | 0.22 + 0.04 | 0.36 + 0.04 | |
| Day 21 to day 28 | 0.29 + 0.06 | 0.54 + 0.06 | 0.35 + 0.06 | 0.34 + 0.06 | |
| Overall 2, 4 | 0.27 + 0.03 | 0.38 + 0.03 | 0.28 + 0.03 | 0.37 + 0.03 | |
| 1 ADG = Average daily gain.
2 Lasalocid effect (P < 0.05). 3 Lasalocid effect (P < 0.01). 4 Energy intake effect (P < 0.01). | |||||
The authors wish to thank Hoffman-LaRoche, Nutley, NJ, for their generous support of this research.
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