Progress 10/01/08 to 09/30/12
Outputs
OUTPUTS: Supplementation with rumen by-pass fat increases the energy density of diets without reducing forage intake, and is a practice commonly used in dairy cows. Two trials were conducted to evaluate the effect of rumen by-pass fat supplementation on milk composition, lamb and ewe body weight, and postpartum interval. In the first trial, rumen by-pass fat (Megalac-R) was provided at 50 g/ewe/day to Barbados Blackbelly and St. Croix ewes (n=100) following December lambing. As ewes lambed they were allocated, blocked by breed, to a control cracked corn, soybean meal supplement or the same supplement with rumen by-pass fat at 1.5% of body weight. For feeding, ewes were transferred together with their lamb(s) to one of 6, 0.4 ha pastures within 7 days after lambing. Ewes were provided with grass hay once pasture forage resources become limited. Sterile rams with marking harnesses were used for estrus detection. Milk samples were collected at 50 days, and lambs weaned at 60 days. By-pass fat supplementation had no effect on litter weaning weight and litter pre-weaning daily gain (13.4 vs. 13.9 kg, and 137 vs. 140 g/d for control and rumen by-pass fat groups, respectively). Ewe body weight change during lactation was also not affected by by-pass fat supplementation (-39 vs -41 g/d, respectively), nor was time to first partum estrus (32.5 vs. 35.2 d, respectively). Milk composition was not different between treatment groups. In the second trial, we evaluated the effect of rumen by-pass fat supplementation at a higher level (150 g/day per ewe) on and milk composition of ewes following August (Fall) and April (Spring) lambing. Ewe management was similar as described for trial 1. Milk samples were collected at 7-8 weeks of lactation. Data was analyzed for the effect diet, season, breed, and number of lambs nursing. Rumen by-pass fat supplementation had no effect on pre-weaning litter daily gain (228 g/d)) or litter weaning weight (19.4 kg), however, ewe lactation weight change was less in control ewes than in ewes fed rumen by-pass fat (-6 vs. -29 g/d). Breed did not affect litter daily gain and weaning weight, though St. Croix ewes were heavier than Barbados Blackbelly ewes. Fall lambing ewes had significantly higher litter weights and ewe daily weight gains than spring lambing ewes. Single-lamb litters were significantly lighter than twin litters, while ewe daily weight change was lower in single than twin-rearing ewes. Milk samples were collected from 84 ewes following spring lambing and 93 ewes following fall lambing. Rumen by-pass fat supplementation had no effect on milk fat, but significantly reduced protein (4.97 vs. 4.64%), lactose (5.23 vs. 4.98%), solids-not-fat (11.09 vs. 10.50%). Season affected levels of milk fat, protein, and solids-not-fat, and were significantly higher in fall than in spring. Differences between seasons in protein and solids-not-fat were more pronounced in control than by-pass fat-supplemented ewes. There was no effect of breed on milk composition, but lactose was significantly higher in ewes nursing single compared to twin lambs. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Inclusion of rumen by-pass fat at a level of 50 to 150 g per ewe per day in a corn/soybean meal supplement during lactation did not improve weaning performance of hair sheep ewes managed under a forage-based system. The lack of a response was independent of lambing season, breed or litter size weaned. Rumen by-pass fed supplementation affected the protein, rather than the fat component of milk in the hair sheep here, and is in contrast to the observations made in dairy sheep.
Publications
- Wildeus, S., 2012. Accelerated hair sheep lamb production systems in the tropics: Joining three times in two years. Tecnol. & Cliet. Agropec. 6:55-63
- Wildeus, S. and Zeng, S. S., 2012. Effect of season and by-pass fat supplementation on milk composition of hair sheep ewes lambing in spring and fall. Proc. Ann. Meet. South. Sect. Am. Soc. Anim. Sci., p. 30.
- Wildeus, S., 2012. Pregnancy rates in hair sheep ewes following vaginal insemination with fresh and short-term stored liquid semen. Reprod. Dom. Anim., 47 (Suppl. 4): 422.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: In a preliminary study at our location, supplementation with rumen by-pass fat at a level 50 g/day per ewe did not affect lambing performance and milk composition in hair sheep ewes. In these subsequent experiments we evaluated if rumen by-pass fat supplementation at a higher level (150 g/day per ewe) would affect the milk composition of ewes following fall and spring lambing. Supplementation with rumen by-pass fat increases the energy density of diets without reducing forage intake, and is commonly used in dairy cows. In dairy ewes by-pass fat increases milk fat content while decreasing protein content, but there is no such information on its use in hair sheep ewes managed under an accelerated mating system. Primiparous and multiparous Barbados Blackbelly (BB) and St. Croix (SC) ewes were joined for 30 d in 3 single-sire mating groups per breed in March and again in November. Ewes were managed as one group during pregnancy, and lambed unassisted on pasture. As ewes lambed they were allocated, blocked by breed, to be supplemented at 1.5% body weight with cracked corn and soybean meal (16% CP) with or without rumen by-pass fat (Megalac-R; 150 g/day per ewe). Within 7 days after lambing ewes were transferred randomly together with their lamb(s) to 1 of 6 experimental 0.4 ha pastures (3 pastures/treatment). Ewes were group-fed supplement on pasture, and provided with grass hay as forage availability warranted. Sterile rams with marking harnesses were used for estrus detection. Milk samples were collected from ewes 7-8 weeks post partum by stripping teats after lambs had been separated for 3 hours. Samples were collected from 84 ewes following spring lambing and 93 ewes following fall lambing. Milk composition was determined by an automated infrared milk analyzer, and composition data analyzed for the effect diet, season, breed, and number of lambs nursing. Rumen by-pass fat supplementation had no effect on milk fat, but reduced (P<0.001), protein (4.97 vs. 4.64%), lactose (5.23 vs. 4.98%), solids-not-fat (SNF; 11.09 vs. 10.50%). Season affected levels of milk fat, protein, and solids-not-fat, and these were higher (P<0.001) in fall than in spring. Differences between seasons in protein and solids-not-fat were more pronounced in control than by-pass fat-supplemented ewes (diet x season interaction; P<0.05). There was no effect of breed on milk composition, but lactose was higher (P<0.01) in ewes nursing single compared to twin lambs. Rumen by-pass fed supplementation affected the protein, rather than the fat component of milk in the hair sheep and is in contrast to the observations made in dairy sheep. This contrast may have also been related to total milk production. However, total milk production was not evaluated in this experiment. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Supplementation with rumen by-pass fat had no effect of milk fat content, but lowered such components as milk protein and milk fat. This effect of rumen by-pass fat may have been associated with a higher total milk production in supplemented ewes.
Publications
- Wildeus, S. and E.J. Chozu, 2011) Performance of two breeds of lactating hair sheep ewes fed rumen by-pass fat following winter lambing. Proc. Ann. Meet. South. Sect. Am. Soc. Anim. Sci., p. 33
- Clary, A.P., E.J., Chozu, S. Wildeus, , and S.S. Zeng, 2011. Effect of rumen by-pass fat supplementation on milk composition of hair sheep ewes. Proc. 16th Biennial Research Symposium, Assoc. Res. Dir., p. 133-134.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Supplementation with rumen by-pass fat increases the energy density of diets without reducing forage intake, and is commonly used in dairy cows. In dairy ewes by-pass fat increased milk fat content while decreasing protein content, but there is no such information on its use in hair sheep ewes managed under an accelerated mating to improve lamb performance and reduce the postpartum interval. The experiment evaluated effects of supplementation with rumen by-pass fat (Megalac-R) on reproductive performance, pre-weaning lamb growth, and milk composition in hair sheep ewes managed under an 8-month accelerated mating following December lambing. Primiparous and multiparous Barbados Blackbelly (BB) and St. Croix (SC) ewes (n=100) bred in July were used. Ewes were managed as one group on pasture during pregnancy, and supplemented with a corn/whole soybean supplement during the third trimester of pregnancy increasing from 1% to 1.5% of bodyweight during the last month of gestation. Ewes lambed on pasture with minimal assistance. As ewes lambed they were allocated, blocked by breed, to be fed either a control cracked corn, soybean meal supplement or the same supplement with rumen by-pass fat (Megalac-R; 50 g/ewe/day) at 1.5% of BW. For feeding, ewes were transferred together with their lamb(s) to one of 6, 0.4 ha pastures within 7 d after lambing (3 pastures per treatment groups). Ewes on pastures were provided with grass hay ad lib once pasture forage resources become limited. Sterile rams with marking harnesses were used for estrus detection. Milk samples were collected at 50 days, and lambs weaned at 60 days post-partum. Megalac supplementation had no effect (P>0.05) on litter weaning weight and litter pre-weaning daily gain (13.4 vs. 13.9 kg, and 137 vs. 140 g/day for control and Megalac, respectively). Ewe body weight change during lactation was also not affected (P>0.05) by Megalac supplementation (-39 vs -41 g/d, respectively), nor was time to first partum estrus (32.5 vs. 35.2 day, respectively). Milk composition was not different between treatment groups, with the exception of solids-not-fat, which were higher in control than Megalac ewes (11.4 vs. 11.0%, respectively). Data suggest that rumen by-pass fat supplementation at 50 g/hd/day had a limited effect on milk composition, difference in composition were actually more pronounced between breeds. There was no effect of either supplementation or breed on weaning performance. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The use of by-pass fat at a level of 50 g/head/day was not effective in reducing the postpartum intervals, changing milk composition, and improving the weaning weights of lambs. Further research is needed to evaluate the benefits of higher levels of by-pass fat supplementation on ewe reproductive and lambing performance.
Publications
- Wildeus, S. and E.J. Chozu. 2010. Liquid semen vaginal AI in three hair sheep breeds during transition to seasonal breeding. J. Anim. Sci., 88, E-Suppl. 3:34
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: In order to maintain an 8-month lambing interval in an accelerated mating system, ewes should conceive early during the breeding season to aid mating in the subsequent breeding cycle. Strategic short term supplementation with melengestrol acetate (MGA), has the potential to synchronize and induce estrus in ewes as they transition between seasonal breeding. Preliminary work in our lab with liquid semen for vaginal (shot-in-the-dark) artificial insemination (AI)in yearling ewes during the breeding season using MGA synchronization resulted in an overall pregnancy rate of 75%. This experiment was conducted to evaluate the use of MGA supplementation to synchronize hair sheep ewes for liquid semen AI in June during the transition to seasonal estrus. A mixed breed flock of Barbados Blackbelly (BB), Katahdin (KA) and St. Croix (SC) multiparous hair sheep ewes (n=195) was initially synchronized by feeding MGA (0.3 mg/head/day) for 4 days followed by an injection with prostaglandin (10 mg Catalyse/head; im) 12 hours after the last MGA meal. Estrus was detected with sterile teaser rams on days 17 to 21 after the last MGA feeding, and ewes were bred 10-14 hours after onset of estrus with either fresh extended semen (within 2 hours of collection), or semen stored for 12 hours at 5 degree C. Ewes were inseminated by deep vaginal deposition of semen without speculum using a standard 0.5 ml AI gun. Semen for AI was collected twice daily by artificial vagina from 12 rams (4 rams/breed), diluted in a skim milk powder (11% w/v) and egg yolk (5% v/v) extender to a concentration of 350 million sperm/ml, and packaged in 0.5 ml straws for use. Ewes were bred to rams of like breed. Pregnancy was determined 23 d after the last day of AI by transrectal ultra-sonography. Only 33% of ewes displayed estrus during the 5 day AI period, and incidence of estrus was similar (P > 0.1) between breeds (BB: 33%; KA: 29%; SC: 37%). Pregnancy rate to AI was low, and similar for BB and SC ewes (28 and 23%, respectively), while KA ewes failed to become pregnant (P < 0.1). In BB and SC ewes pregnancy rate was not different (P > 0.1) for fresh and 12 h-stored semen (28 and 23%, respectively), but was higher (P < 0.05) for AM than PM inseminations (41 and 14%, respectively). PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Short-term MGA supplementation in June failed to generate a satisfactory estrus response in hair sheep ewes, and additional steps may be needed to induce estrus. Pregnancy rates in this trial were also lower than those achieved previously during the breeding season, and suggest that liquid seman AI should be delayed until late summer or early fall.
Publications
- No publications reported this period
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