Croix Ewes Research Articles

Influence of the concentration and nature of total dissolved solids in brackish groundwater on water intake, nutrient utilization, energy metabolism, ruminal fermentation, and blood constituents in different breeds of mature goats and sheep

Brackish water is being progressively utilized in livestock farming across the globe where freshwater is scarce, potentially leading to detrimental consequences for animal health and performance. This study was conducted to determine effects of different brackish groundwater types on water and feed intake, nutrient utilization, ruminal fluid characteristics, and blood constituent concentrations in different breeds of goats and sheep in a 6 (animal types; AT) × 6 (water treatments; WT) Latin square design. Six AT (Boer, Spanish, and Tennessee Stiff-Leg does and Dorper, Katahdin, and St. Croix ewes) consumed drinking water differing in total dissolved solids (TDS) and mineral composition. Six WT were fresh water (FRW; 287 mg TDS/kg), a natural brackish water (BR) alone (100-BR; 5734 mg TDS/kg), BR with concentrations of all minerals increased by about 100 % (200-BR; 10,603 mg TDS/kg), FRW added with NaCl having similar TDS level (6654 mg/kg) as 100-BR (100-SL), FRW added with NaCl having similar TDS (12,197 mg/kg) as 200-BR (200-SL), and water with similar TDS (10,643 mg/kg) level as 200-BR by adding NaCl to 100-BR (200-BR/SL). Water treatment only affected (P < 0.05) water intake, total volatile fatty acids in ruminal fluid, blood phosphorus, blood aldosterone, and plasma osmolality. Water intake was greater (P < 0.05), but total ruminal volatile fatty acid concentrations were lower (P < 0.05) for 200-SL than other WT. Plasma osmolality and aldosterone concentrations were lower (P < 0.05) for 200-SL and 200-BR/SL than FRW. There were no significant interactions between WT and AT for any variable. Water and feed intake, digestibilities, ruminal ammonia concentration, and methane emission were similar among AT (P > 0.05). There were differences (P < 0.05) among AT for many ruminal fermentation and blood characteristics. Although there were some differences among WT, no AT seemed adversely affected by water with a TDS level near or slightly above 10,000 mg/kg regardless of mineral sources.

Effects of Nutritional Plane at Breeding on Feed Intake, Body Weight, Condition Score, Mass Indexes, and Chemical Composition, and Reproductive Performance of Hair Sheep.

This study was conducted to assess effects of the nutritional plane before and during breeding on feed intake, body weight (BW) change, reproductive performance, body condition score (BCS), body mass indexes (BMI), and body composition of three breeds of hair sheep. Twenty-five Dorper, 27 Katahdin, and 33 St. Croix ewes were allocated to groups and treatments based on initial BW and age. Supplementation treatments were soybean meal fed at 0.16% BW (LS) and a mixture of 25% soybean meal and 75% ground corn given at 0.8% BW (HS; dry matter basis) for 88 to 102 days including 17 days after breeding. Wheat straw intake (% BW) was greater (p < 0.01) for LS than for HS. Average daily gain and BCS change were similar among breeds, but both were greater for HS vs. LS. Birth rate, litter size, total litter birth weight, gestation length, and number of services were similar among breeds (p > 0.05), although individual lamb birth weight was lower for St. Croix than for Katahdin (p < 0.05). None of these reproductive variables were influenced by treatment or the breed × treatment interaction (p > 0.05). There were no breed differences in whole body concentrations of water, fat, protein, ash, or energy in week 0 or 4, but in 8 week concentrations of water, protein, and ash were greatest among breeds for St. Croix (p < 0.05) and levels of fat and energy were lower for St. Croix than for Dorper (p < 0.05). In week 8, total amounts and concentrations of fat and energy were greater for HS vs. LS and those of water, protein, and ash were less for HS (p < 0.05). There were interactions (p < 0.05) between treatment and period in blood concentrations of cholesterol and non-esterified fatty acids and between breed, treatment, and period in level of triglycerides and total antioxidant capacity. The concentration of cortisol was greater for HS vs. LS (p < 0.05). In conclusion, supplementation did not influence reproductive performance despite differences in BW and BCS change, which may be due to the initial moderate BCS and greater wheat straw intake for the LS treatment.

176 Costs for Supplementing Small Ruminants Under the Various Grazing-Based Production Systems

Abstract The supplementary feeding costs of small ruminants can be substantial when there is not much vegetation available for grazing or browsing. However, such costs have not been reported well and the strategies to minimize them not discussed enough. The objective of this study was to quantify the feeding costs involved in supplementing small ruminants under grazing-based production systems. Grazing studies were conducted from July to October in 2021 (88 d) in woodlands with lactating Kiko does (17) along with their young kids (33). Animals were divided into two groups (1 &amp; 2) and randomly allocated to three woodland plots each for rotational stocking. Group 1 was allowed to rotationally graze in nearby silvopasture plots for 3-4 hours daily and Group 2 was supplemented with ad lib. hay and corn (0.5% metabolic wt.). Another study was conducted from October to December 2021 (70 d) involving 56 Kiko goats and 18 Katahdin-St. Croix ewes. During this study, there was not much foliage available, and animals were supplemented with hay (ad lib.) and corn (0.5% live wt.). Cost and amount of hay and corn used for supplementation were recorded. Data were analyzed in Excel for descriptive statistics. In the woodland study, cost for supplementing animals was $0.13 per animal per day, with 86% of the cost accounted for hay and 14% for corn. In the second study, when not much vegetation was available for grazing, cost for supplementing animals was $0.43 per animal per day, with hay cost accounting for 77% and remaining for corn. Findings of this study suggest that planted forages can be used to replace the need for purchased feed during the forage-growing period. The costs of supplementation can be significantly high during the lean period of forage production.

121 Breed and Mating Season Effects on Gestation Length in Landrace Hair Sheep Ewes

Abstract Gestation length in sheep varies with breed, but little information is available on hair sheep and any effects of time of year of mating. Data were collected between 1997 and 2021 on straight-bred Barbados Blackbelly (BB) and St. Croix (SC) ewes managed under pasture-based, accelerated mating. Rams were fitted with marking harnesses and ewe gestation length was determined as the difference between lambing and marking date. Gestation length (n = 1291) was analyzed with fixed class effects of ewe breed (BB or SC), age class at mating (4 levels), mating month (March, July, or November), and litter size (1, 2, or ≥ 3) and the linear and quadratic effects of total litter birth weight (LBW). Two-way interactions were initially fit but removed as none were significant (P &amp;gt; 0.15). Random effects included ewe and mating month – year (n = 350 and 32, respectively). Gestation length was 0.8 d longer for SC than BB ewes and 0.5 to 0.7 d longer (P ≤ 0.03) for &amp;gt; 5.5 yr-old ewes than all younger age classes. However, mating month did not impact gestation length (P = 0.11). Ewes that gestated a single lamb had longer gestation length (149.8 ± 0.20 d; P &amp;lt; 0.001) than twin- (147.4 ± 0.14 d) and triplet-bearing ewes (146.7 ± 0.28 d), which were also different from each other (P = 0.01). Finally, both quadratic and linear effects of LBW were significant (P &amp;lt; 0.001) and indicated gestation length increased with LBW until reaching an inflection point at approximately 9.1 kg. Gestation length in landrace hair sheep ewes was in line with the 147 d commonly used in gestation calculators. Slight adjustments can be made for ewe age, breed, and litter size, but are not needed for mating month.

Effects of an array of dietary treatments and length of feeding on ruminal methane emission and other variables in hair sheep

Eighteen Katahdin sheep ewes (initial body weight [BW] = 73.7 ± 1.76 kg and age = 5.2 ± 0.56 yr) and 18 St. Croix ewes (54.7 ± 1.33 kg BW and 4.1 ± 0.42 yr) were used in an experiment to determine effects of dietary level of Sericea lespedeza (Lespedeza cuneata; 5.8% condensed tannins and 10.3 % crude protein, dry matter [DM] basis) and other supplemental ingredients on BW, feed intake, digestion, energy metabolism, ruminal methane emission, and levels of blood and ruminal fluid constituents. Diets were consumed ad libitum and included a concentrate supplement at approximately 0.45 % BW (DM). Alfalfa (Medicago sativa) was the basal forage for control (CON), ionophore (ION; lasalocid at 33 mg/kg DM), coconut oil (3%; CCO), and soybean oil (3%; SBO) diets, and forage in moderate- and high-lespedeza diets was a 1:1 mixture of alfalfa and lespedeza and all lespedeza, respectively (ALF:LES and LES, respectively). There were four 6-wk periods, with digestion assessed in wk 4 and measures with a respiration calorimetry system in wk 5. Although there was a three-way interaction involving dietary treatment, breed, and period, average forage intake was greater for LES than for CON, ION, CCO, SBO (P < 0.05), and ALF:LES (P = 0.062; 988, 1072, 1265, 987, 951, and 1057 g/day for CON, ALF:LES, LES, ION, CCO, and SBO, respectively; standard error of the mean [SEM] = 69.4). Dietary level of lespedeza had marked effects (P < 0.05) on digestion of organic matter [OM] (69.2, 57.6, 50.3, 66.3, 66.0, and 68.7 %; SEM = 1.57) and nitrogen (78.3, 65.3, 46.8, 71.4, 73.9, and 75.7 %; SEM = 1.81), with digestible OM intake numerically lower (P > 0.05) for diets with lespedeza and for ION (697, 607, 589, 598, 635, and 690 g/day for CON, ALF:LES, LES, ION, CCO, and SBO, respectively; SEM = 50.4). There was a treatment by period interaction (P < 0.05) in ruminal methane emission relative to digestible energy intake, but overall, emission was greatest among treatments (P < 0.05) for CON (12.33, 9.92, 10.24, 10.41, 8.91, and 8.66 % for CON, ALF:LES, LES, ION, CCO, and SBO, respectively; SEM = 0.730). Average daily gain (ADG) was greatest among treatments (P < 0.05) for SBO (54, 28, 18, 40, 56, and 98 g; SEM = 13.2). Many findings are not closely aligned with those of previous studies with goats. For example, effects of lespedeza on feed intake and ruminal methane emission were greater in the first than second half of the experiment, though interactions observed could not be clearly attributed to factors such as microbial adaptation. The effect of the SBO diet on ADG with the alfalfa-based diet deserves future research attention.

PSXI-24 Evaluation of Barbados Blackbelly and St. Croix hair sheep under accelerated lambing using purebred and terminal sire mating: Ewe fertility, prolificacy, and productivity

Abstract Objectives were to evaluate ewe performance under an accelerated, pasture-lambing system. Barbados Blackbelly (n = 85) and St. Croix ewes (n = 91) were exposed to rams of their own breed (pure) or Dorset (terminal) in November (2012 and 2014), July (2013 and 2015), and March (2014 and 2016). Traits considered were fertility (i.e., ewes lambing/ewes exposed; n = 670) and number of lambs born (NLB), number of lambs weaned (NLW), and total 65 d adjusted litter weaning weight (LWW; n = 548 each). Data were analyzed with fixed effects of ewe age (1, 1.5, 2 yr, or ≥ 2.5 yr), breed, mating system (pure vs terminal), mating month-year, and the mating system x mating month-year interaction and a random ewe effect. Fertility was greater for Barbados Blackbelly than St. Croix ewes (0.88 vs 0.73; P &amp;lt; 0.01) but ewe breed did not affect any other trait (P ≥ 0.06). The mating system x mating month-year interaction effect impacted all traits (P ≤ 0.03) except NLB (P = 0.09) and performance between mating systems was compared within mating month. Fertility was greater for pure than terminal mated ewes in November (0.96 vs 0.85) and July (0.94 vs 0.53; P ≤ 0.01). Following July mating, both NLB and NLW were greater for pure than terminal mated ewes (1.69 vs 1.37 lambs and 1.43 vs 1.11 lambs, respectively; P &amp;lt; 0.01). However, LWW was greater for terminal than pure mated ewes after November (18.0 vs 15.7 kg) and March mating (18.1 vs 14.2 kg; P ≤ 0.02). Using a terminal sire in landrace hair sheep under accelerated mating generally reduced fertility, NLB, and NLW but improved LWW. The strategic use of terminal sire mating should be considered just during breeding season, or the use of alternative sire breeds should be evaluated.

Effects of Sericea Lespedeza on Feed Intake, Digestion, and Ruminal Methane Emission in Hair Sheep

Abstract Eighteen Katahdin (initial body weight of 74 kg; SEM=1.8) and 18 St. Croix ewes (55 kg; SEM=1.3) were used in an experiment with four 6-wk periods to determine effects of dietary level of Sericea lespedeza (Lespedeza cuneata) containing 5.8% condensed tannins (dry matter; DM) and other supplemental ingredients on feed intake, digestion, and ruminal methane emission. Diets were consumed ad libitum and included a concentrate supplement at 0.45% BW (DM). Alfalfa was the basal forage for control (CON), ionophore (ION; lasalocid at 33 mg/kg DM), coconut oil (3%; CCO), and soybean oil (3%; SBO) diets, and forage in moderate- and high-lespedeza diets was a 1:1 mixture of alfalfa and lespedeza and all lespedeza, respectively (MSL and HSL, respectively). Data were analyzed with a 2 x 6 factorial arrangement of treatments, period as a repeated measure, and a mixed effects model. Digestion and methane emission were determined in weeks 4, 10, 16, and 22. Total DM intake was similar among treatments (P = 0.070) but numerically greatest for HSL (1,197, 1,297, 1,491, 1,203, 1,195, and 1,207 g/d; SEM=81.1), OM digestibility ranked (P &amp;lt; 0.05) CON, ION, CCO, and SBO &amp;gt; MSL &amp;gt; HSL (69.2, 57.6, 50.3, 66.3, 66.0, and 68.7%; SEM=1.57), and digestible OM intake was similar among treatments (P = 0.517; 697, 607, 589, 598, 635, and 690 g/d for CON, MSL, HSL, ION, CCO, and SBO, respectively; SEM=50.4). There were no interactions involving time in ruminal methane emission, which was greatest among treatments for CON (P &amp;lt; 0.05) in MJ/d (1.39, 0.93, 0.90, 0.92, 0.85, and 0.96; SEM=0.069) and relative to digestible energy intake (20.6, 15.7, 16.8, 16.1, 13.7, and 13.9% for CON, MSL, HSL, ION, CCO, and SBO, respectively; SEM=1.223). In conclusion, dietary inclusion of Sericea lespedeza may offer a natural and sustainable means of decreasing ruminal methane emission by hair sheep as previously shown in goats, with a magnitude of impact similar to that of some other supplemental dietary ingredients.

Behavioral and physiological responses to early weaning in ewes and their single or twin lambs

As during the early postpartum, ewes and their twin lambs have a weaker bond than ewes that rear single lambs; it might be expected that early artificial weaning would trigger less intense behavioral and physiological responses in mothers and their twin lambs than in mothers and their single lambs. The aim of this study was to compare the behavioral and physiological responses of ewes and their twin or single lambs to early weaning. The study was performed with 19 Saint Croix ewes: 10 bearing single lambs and nine bearing twins (data from only one sibling from each pair of twins was collected). Lambs were weaned at 43days old. Body weight, stress-related behaviors, and blood protein concentrations were recorded in ewes and lambs before and after weaning. Single lambs were heavier and paced more frequently during the day of weaning than twin lambs (10.6 ± 0.4 vs 8.9 ± 0.4kg; P = 0.007 and 4.1 ± 0.4 vs 1.5 ± 0.4%; P = 0.0003, respectively). In addition, ewes rearing single lambs paced and vocalized more than twin lambs' mothers the day of weaning (pacing, 42.4 ± 1.1 vs 20.0 ± 1.2%; P < 0.0001; vocalizations, 43.1 ± 2.6 vs 21.3 ± 2.7%; P < 0.0001). Litter size affected only ewes' albumin concentration, without other effects in protein concentrations in ewes or lambs. In conclusion, early weaning triggered stronger behavioral responses in mothers and their single lamb than in mothers and their twin lambs.

PSX-11 Effects of nutritional plane before breeding on body condition score, mass indexes, and chemical composition of hair sheep

Abstract Twenty-five Dorper (D), 27 Katahdin (K), and 33 St. Croix (S) ewes were used to characterize changes in BW, body condition score (BCS), body mass index (BMI), and body composition with different nutritional planes before breeding. Supplement treatments were soybean meal fed at 0.16% BW and 25% soybean meal and 75% ground corn at 0.8% BW (DM; L and H, respectively). There were two animal groups and pens per breed and supplement treatment. Shrunk BW (20 h without feed and water), BCS (1–5), linear measures including wither height and length from the point of the shoulder to pin bone, and body composition via urea space were determined after 0, 4, and 8 wk. Initial values were 62.10, 59.99, 61.57, 62.25, 50.23, and 52.98 kg shrunk BW (SEM=3.601); 35.82, 34.81, 35.57, 36.41, 33.77, and 34.09% fat (SEM=1.043); 17.06, 16.72, 16.98, 17.27, 16.38, and 16.49 MJ/kg energy (SEM=0.357); 3.29, 3.41, 3.29, 3.29, 2.99, and 3.18 BCS (SEM=0.139); and 13.72, 14.22, 12.69, 12.81, 11.53, and 11.50 g/cm2 BMI (BW/(height×length); SEM=0.463) for D-L, D-H, K-L, K-H, S-L, and S-H, respectively. Change from wk 0 to 8 was -0.80, 2.90, -2.74, 3.33, -2.02, and 3.36 kg shrunk BW (SEM=0.842); -0.14, 2.03, -1.45, 1.70, -0.85, and 2.10 kg fat (SEM=0.862); -8.4, 83.7, -62.5, 73.8, -38.4, and 88.1 MJ energy (SEM=33.30); -0.02, 0.20, 0.04, 0.29, -0.08, and 0.17 BCS (SEM=0.070); and -0.265, 0.297, -0.185, 0.491, -0.571, and 0.587 g/cm2 BMI (SEM=0.488) for D-L, D-H, K-L, K-H, S-L, and S-H, respectively. Correlation coefficients between change in BCS and mass of water, fat, and energy were 0.35 and 0.44 (P ≤ 0.004), and those for BMI were 0.54 and 0.56, respectively (P &amp;lt; 0.001). In conclusion, a BMI can be more highly related to and predictive of change in body composition of hair sheep resulting from different nutritional planes compared with BCS.

PSV-13 Genetic parameters and quantitative trait loci for heat stress related traits in sheep

Abstract Greater selection emphasis has been placed on efficiency than on fitness in livestock populations over the last several decades. Heat stress is a concern in production systems due to the negative effects on production, reproduction, and immunity. The objective of the study was to estimate variance components and identify quantitative trait loci (QTL) for heat stress related traits in sheep. A total of 125 Dorper, Katahdin, and St. Croix ewes originating from four regions of the United States were selected for the experiment. Animals were separated into four trials due to facility limitations. Data were collected for each trial over four consecutive two-week periods in an environmentally controlled facility with targeted heat load index (HLI) for daytime/nighttime of 70/70, 85/77, 90/77, and 95/81. Body weight was collected three times per week and rectal temperature was collected weekly. Black globe temperature and humidity were measured every 15 minutes. Animals were genotyped using the Illumina OvineSNP50 BeadChip. After quality control, 49,396 effective single nucleotide polymorphisms were included in the univariate analysis performed with the BLUPF90 suite of programs. Fixed effects in the models included region of origin, breed, trial, and age as a covariate. Traits analyzed included rectal temperature at 95 HLI (RT95), feed intake at 95 HLI (FI95), and average daily gain for the period for HLI between 90 and 95 (ADG). Heritabilities for RT95, FI95, and ADG were 0.35, 0.10, and 0.10, respectively. Largest effect QTL were identified on chromosomes 23, 9, and 6 for RT95, chromosomes 9, 2, and 20 for FI95, and chromosomes 6, 1, and 5 for ADG. Many of the regions identified have also been associated with weight and carcass traits in other studies, but few had obvious connections to the heat stress related response. In conclusion, results suggest selection could improve heat tolerance in sheep.

Effects of water restriction on feed intake, digestion, and energy utilization by mature female St. Croix sheep

Eleven St. Croix ewes (46.9 ± 1.59 kg BW and 3.6 ± 0.67 yr age) were used in a crossover design to evaluate effects of restricted drinking water availability on intake of a 50% concentrate diet, digestion, and energy utilization. After 2 wk to determine ad libitum water consumption, there were two 4-wk periods, with measures in metabolism cages during wk 4. One treatment was water offered at the ad libitum level (CONT) and the other entailed a 25% reduction in wk 1 and 50% thereafter (REST). Although, some water was refused in wk 4, with intake of 2556 and 1707 g/day for CONT and REST, respectively (SEM=170.9). Digestibility of gross energy was greater (P = 0.034) for REST than for CONT (66.5 vs. 62.4%; SEM=1.16); however, because of a numerical difference (P = 0.448) in energy intake (15.79 and 14.66 MJ/day for CONT and REST, respectively; SEM=1.426 MJ/day), digested energy intake was similar between treatments (P = 0.870). Urinary energy was greater (P = 0.023) for CONT vs. REST (0.62 and 0.52 MJ/day; SEM=0.038) and methane energy did not differ (P = 0.213) between treatments (0.76 and 0.89 MJ/day; SEM=0.084), resulting in similar (P = 0.665) ME intake (8.50 and 8.01 MJ/day for CONT and REST, respectively; SEM=0.855). Both heat (8.60 and 8.33 MJ/day; SEM=0.437) and recovered energy (-0.10 and -0.30 MJ/day for CONT and REST, respectively; SEM=0.623) were similar between treatments (P ≥ 0.880). In conclusion, increased digestibility appears an important adaptive response to limited availability of drinking water.

PSX-40 Effects of nutritional plane before breeding on performance of hair sheep

Abstract The objective of the study was to determine effects of the nutritional plane before breeding on performance of different hair sheep breeds. Twenty-five Dorper, 27 Katahdin, and 32 St. Croix ewes with initial BW of 65.6, 65.7, and 54.3 kg (SEM=1.95) and body condition score (BCS; 1–5) of 3.35, 3.29, and 3.09, respectively, consumed wheat straw ad libitum for 11 wk before breeding. Ewes of each breed were divided into four groups, with two groups per nutritional plane (NP). Ewes on a low NP (Low-NP) were supplemented with 0.16% BW (DM) of soybean meal (SBM) and ewes on the high NP (High-NP) received 0.8% BW (DM basis) of 0.25% soybean meal and 0.75% ground corn. Ewes were divided into two groups for estrus synchronization. Four rams of each breed were used, two for the first 17 d of breeding and the other two from d 17 to 34. Conception and embryo mortality were determined by ultrasound imaging at 25 and approximately 40 d post-breeding. Average daily gain and BCS change were similar among breeds, but both were greater for High-NP vs. Low-NP (ADG: 57 vs. -4 g, SEM=8.1; BCS change: 0.22 vs. -0.02, SEM=0.041). Wheat straw DMI was greater (P = 0.01) for Low-NP than for High-NP (2.02 and 1.58% BW, respectively; SEM=0.042) and for St. Croix than for Dorper and Katahdin (P = 0.04; 1.96, 1.68, and 1.74% BW, respectively, SEM=0.060). There were no differences in the number of services or conception (P &amp;gt; 0.05), and no embryo mortality was noted. In conclusion, NP did not influence reproductive performance assessed early after breeding despite differences in ADG and BCS change. This may be due to moderate initial BCS and increased straw intake by Low-NP ewes.

Short communication: milk production and lamb development in Saint Croix and Katahdin hair sheep breeds (Ovis aries).

The aim of the present study was to characterize milk production and preweaning development of lambs from Katahdin and Saint Croix sheep. Milk production was measured weekly, from birth to 8weeks using oxytocin technique, in 12 Katahdin (62.0±5.0kg) and 11 Saint Croix (46.2±4.83kg) multiparous ewes. The mean daily milk production for the Katahdin ewes was 1.38±0.54L/day and for the Saint Croix ewes it was 1.26±0.49L/day (P>0.05) (mean ± SE for each group). However, more colostrum was produced immediately after parturition by the Katahdin than Saint Croix ewes (P<0.001). The lamb's weight and weight gain were recorded weekly. The birth weight of lambs from both breeds was similar but at weaning, the Katahdin lambs were heavier (16.46±0.58kg) than the Saint Croix lambs (12.90±0.59kg) (P<0.001). Furthermore, a significant positive correlation was found between daily milk yield and daily gain weight in both breeds, but with a greater slope in Katahdin lambs in comparison with Saint Croix lambs. It was concluded that Saint Croix and Katahdin hair sheep breeds produced similar amounts of milk during lactation, but the latter produced heavier lambs at weaning.

697 Effects of high heat load conditions on body weight, dry matter intake, and blood constituent levels of Dorper, Katahdin, and St. Croix sheep from different regions of the United States

Thirty-seven Dorper, 35 Katahdin, and 31 St. Croix ewes (57, 58, and 44 kg [SEM 2.2]) from 45 commercial farms in the Midwest (MW), Northwest (NW), Southeast (SE), and central Texas (TX), between 2.2 and 3.4 yr of age, were used to evaluate responses to high heat load index (HLI) conditions. There were 4 sequential 2-wk periods with target HLI during day/nighttime of 70/70, 85/70, 90/77, and 95/81. A 15% CP and 50% concentrate pelleted diet was fed at 120% of the ME requirement for maintenance, and water was offered free choice. Body weight was measured 3 times each week, and blood was sampled at 1300 h on the last day of each period. There was an interaction (P < 0.001) between period and week within period in BW, with slightly greater values in wk 2 vs. 1 of periods 3 and 4 and a greater difference between period 1 and 4 values in wk 2 than 1 (53.1, 54.1, 54.9, and 55.4 kg in wk 1, and 53.0, 54.2, 55.4, and 56.1 kg in wk 2 in periods 1, 2, 3, and 4, respectively [SEM 0.85]). There was an interaction (P = 0.037) in DMI (g/kg BW0.75) among region, period, and week, with values generally similar between weeks in periods 1 and 2 relative to those in periods 3 and 4 (51.0, 52.4, 51.0, and 51.2 in period 3 and wk 1; 49.5, 52.1, 50.8, and 51.6 in period 3 and wk 2; 49.6, 52.1, 50.6, and 49.4 in period 4 and wk 1; and 48.9, 52.0, 49.7, and 46.3 in period 4 and wk 2 for MW, NW, SE, and TX, respectively [SEM 1.09]). Neither blood glucose nor lactate concentration was affected by breed (P > 0.05), but there were breed differences (P < 0.02) in serum concentrations of creatinine (0.91, 0.81, and 0.77 mg/dL [SEM 0.023]), total protein (6.13, 6.42, and 6.81 g/dL [SEM 0.156]), and urea N (17.4, 18.0, and 20.0 mg/dL [SEM 0.54] for Dorper, Katahdin, and St. Croix, respectively). In conclusion, some blood constituent levels suggest breed differences in resilience to high HLI. Differences among periods and weeks in BW presumably relate to increased water consumption with high HLI. The interaction in DMI may reflect differences among regions in rate of adaptation to high HLI and the contribution of decreased feed intake to coping with high HLI.

The effect of permanent or temporary contact with the lamb and contact with males on the lambing to first ovulation interval in Saint Croix sheep

The effect of suckling and presence of the lamb, or ram, on the lambing to first ovulation interval in Saint Croix sheep was determined. Ten days after lambing 50 ewes and their lambs were assigned to three different suckling treatments: continuous suckling (CS), restricted suckling (RS), restricted lamb presence (RP). Ewes from each treatment were allocated to groups that had contact with a ram (TR) or remained isolated from rams (IR). Therefore, overall, there were six groups with 2 factors: CS-IR (n=7) CS-TR (n=7); RS-IR (n=11); RS-TR (n=11); RP-IR (n=7), and RP-TR (n=7). The presence of the ram (P=0.01) and restricted suckling (P=0.05) reduced the interval from lambing to first ovulation, while no interaction was found (P>0.05) between these two factors. An effect of treatment and its interaction influenced significantly the number of vocalizations and growth rate in lambs. At the day of weaning RP vocalized more than RS (P<0.01), which in turn vocalized more than CS (P<0.01), followed by a general decline to pre-weaning levels 48h later. Lambs in RP had greater growth rate during first 3 d after weaning compared with RS (P<0.05), which displayed greater growth rate that CS (P<0.05). In addition, an effect of treatment (P=0.05) was found in cortisol concentration. Our results indicate that Saint Croix ewes respond to the ram effect in early postpartum, shortening the resumption of postpartum ovarian activity. When this technique is combined with restricted suckling, additional benefits are achieved for lambs with reduced weaning stress.

Effect of available space and previous contact in the social integration of Saint Croix and Suffolk ewes.

Reproduction in tropical sheep is not affected by season, whereas the reproductive cycle of temperate-climate breeds such as Suffolk depends on the photoperiod. Close contact with tropical ewes during the anestrous period might induce Suffolk ewes to cycle, making the use of artificial light or hormonal treatments unnecessary. However, the integration of both breeds within the social group would be necessary to trigger this effect, and so the aim of the experiment was to determine the speed of integration of 2 groups of Saint Croix and Suffolk ewes into a single flock, according to space allowance and previous experience. For this, 6 groups of 10 ewes (half from each breed) from both breeds, housed at 2 or 4 m/ewe (3 groups/treatment) and with or without previous contact with the other breed, were monitored for 3 d. Each observation day, the behavior, movement, and use of space of ewes were collected during 10 min at 1-h intervals between 0900 and 1400 h. Generalized linear mixed models were used to test the effects of breed, space allowance, and previous experience on behavior, movement, and use of space. Net distances, interbreed farthest neighbor distance, mean interbreed distance, and walking frequencies were greater at 4 m/ewe ( < 0.05). Intrabreed nearest neighbor, mean intrabreed neighbor, and interbreed nearest neighbor distances and minimum convex polygons at 4 m/ewe were greatest for Saint Croix ewes, whereas the opposite was found for lying down ( < 0.05). Experienced ewes showed larger intrabreed nearest neighbor distances, minimum convex polygons, and home range overlapping ( < 0.05). Experienced ewes at 4 m/ewe showed longest total distances and step lengths and greatest movement activity ( < 0.05). Experienced ewes walked longer total distances during Day 1 and 2 ( < 0.05). Lying down frequency was greater for Day 3 than Day 1 ( < 0.05), and Suffolk ewes kept longer interindividual distances during Day 1 ( < 0.05). After 3 d of cohabitation, Suffolk and Saint Croix ewes did not fully integrate into a cohesive flock, with each breed displaying specific behavioral patterns. Decreasing space allowance and previous experience resulted in limited benefits for the successful group cohesion. Longer cohabitation periods might result in complete integration, although practical implementation might be difficult.

Short-term under-nutrition affects feeding and sexual behaviour in oestrous-synchronized Saint Croix ewes (Ovis aries)

ABSTRACTTo determine the effect of short-term under-nutrition on feeding and sexual behaviour in oestrous sheep, the oestrus cycles of 51 Saint Croix ewes were synchronized, and they were randomly assigned to one of two groups. Each group was maintained on a Taiwan grass (Pennisetum purpureum) pasture for 102 h after sponge withdrawal. This diet provided 400 g of dry matter/100 kg of body weight/day, the total available for one group (T), whilst another group (T + C) received an additional 350 g/animal/day of concentrate. Before and after the experimental period, all animals received the additional concentrate. A pen with two one-way gates was located in the centre of each pasture to capture those ewes showing proceptive behaviour towards a ram tethered inside, while sexual receptivity tests were performed every 6 h for 102 h, starting at sponge withdrawal, by moving the ewes to an adjacent pen and exposing them to an intact ram. Foraging behaviour was recorded by scan samples before the sexual receptivity tests. Progesterone concentration was determined on days 2 and 11 after sponge withdrawal. Only 26% of the ewes in the T + C group and none in the T group displayed proceptive behaviour. In both groups, all ewes displayed sexual receptivity and ovulated. Grazing, rumination and walking were higher in T ewes. The frequency and the duration of lying were higher in the T + C than in the T ewes. It was concluded that the short-term nutritional deficiency induced changes in foraging behaviour and decreased ram-seeking behaviour in oestrous-synchronized ewes.

Close contact with spontaneously cycling Saint Croix ewes triggers cyclic activity in seasonally anestrous Suffolk ewes

In domestic goats, oestrous activity may be induced by close contact with cyclic females. As tropical breeds of sheep show light seasonality or are even unaffected by season, the purpose of this study was to examine the hypothesis that cyclic activity may be induced in anestrous Suffolk ewes by close contact with spontaneously cycling Saint Croix ewes. The experiment was conducted with 17 anestrous Suffolk ewes that were assigned to one of two groups. Although Suffolk ewes in the Control group (n = 9) remained isolated, those of the treated group (n = 8) were joined (Day 0) and maintained in close contact with 20 Saint Croix ewes for 38 days. Serum progesterone concentration was measured in all ewes in blood samples collected on Days –8, –2, 8, 13, 18, 23, 28, 33 and 38. Before Day 0, 17/20 Saint Croix ewes were cycling, but no Suffolk ewe had luteal levels of progesterone. By Day 13, more treated than Control Suffolk ewes had progesterone luteal concentrations (8/8 vs 1/9; P = 0.0004). It was concluded that spontaneously cycling Saint Croix ewes induce cyclic activity in anestrous Suffolk ewes.

Changes in mother-offspring relationships with the increasing age of the lamb in hair sheep (Ovis aries)

Changes in the mother-offspring relationship with increasing age of the offspring were analyzed in 46 Saint Croix ewes and their single male lambs from 7 to 58 days after lambing. Physiological and behavioral variables were measured every second day during 10-minute separation periods (pen test) and after traveling 25 m toward their restrained offspring or mother (reunion test). The changes in the variables measured in both tests were analyzed using linear regression. No relationship was found between the respiration rate, heart rate, locomotor activity, number of bleats or serum cortisol concentration registered during pen tests and the age of the lambs. In contrast, although no relationship was found between heart rate, locomotor activity, and cortisol concentration, ewes displayed higher respiration rate ( r = −0.45; P < 0.05) and vocalized more ( r = −0.85; P < 0.05) in the pen tests during the first days postpartum. Bleats decreased from 22.00 ± 2.32 to 6.68 ± 0.05 bleats per minute from day 7 to day 58, respectively. In the reunion test, it was not until lambs were 16 days old that 100% of them could reach their mother. However, all ewes reached their lambs before 17 days postpartum but failed to complete the reunion test within the time limit (1 minute) or took more ( P < 0.05) time to reach their lamb as the experiment progressed. These results support the hypothesis that, in Saint Croix sheep, the interest of the mother in her young is stronger immediately after parturition and declines with increasing age of the lamb, whereas the interest of the lambs shows an inverse relationship.

Strategies for rapid rebreeding of lactating ewes in the spring

Rapid rebreeding of winter- and spring-lambing ewes is essential if ewes are to lamb more than once per year, but fertility of lactating ewes is often low and early weaning of lambs may be undesirable in forage-based production systems. Selection to improve fertility in spring matings has been successful and led to development of ewes with a reduced seasonal anestrus. Potential for rapid rebreeding of lactating out-of-season breeding (OOS) ewes was tested in three studies. In Experiment 1, effects of short-term lamb removal on rebreeding was evaluated over 2 years using 71 January-lambing OOS ewes. At an average of 63 days postpartum, 36 ewes had lambs removed for 72 h, and all ewes were joined with rams. Circulating progesterone levels indicated that 74% of ewes ovulated before lamb separation; 91% of ewes mated within 5 weeks of ram exposure, 85% were diagnosed as pregnant and 75% lambed. The average interval between lambings was 225 days. In contrast to results observed in cattle, none of the measured variables was affected by lamb separation (P>0.20). Experiment 2 compared rebreeding performance of 24 OOS and 23 St. Croix ewes that lambed in January and averaged 60 days postpartum at ram introduction. More OOS ewes ovulated, mated and became pregnant during the first 21 days of ram exposure (83.3%, 58.3%, and 41.7%, respectively; P<0.001) compared with St. Croix ewes (26.1%, 0%, and 0%, respectively). After 39 days of ram exposure, pregnancy rates still favored OOS ewes (66.7% v. 39.1%; P=0.06), but the percentage of ewes that lambed did not differ (P>0.20) between OOS (47.8%) and St. Croix ewes (34.8%). In the third study, 34 March-lambing OOS ewes were exposed to rams on May 3 at an average of 40 days postpartum to characterize their reproductive performance. After 39 days of ram exposure, 52.9±8.7% of the ewes had mated, and 38.2±8.5% were diagnosed as pregnant. However, only 20.6±7.0% of the ewes produced viable lambs, suggesting a high level of uterine insufficiency. Spring fertility of lactating OOS ewes in these studies was one of the highest reported in the literature and indicated that selection for fertility in spring mating would improve reproductive performance in accelerated lambing programs. However, exposure of lactating OOS ewes to rams at 30 to 50 days postpartum was associated with high prenatal lamb mortality.