358 Effect of Molasses Type on Pre-weaning Lamb and Ewe Performance

The objective of this study was to investigate the effects of form of molasses on lamb and ewe performance. Creep feeding of lambs is essential to lamb growth, rumen development, and reduction of milk production from dams. Molasses is often added for increased palatability and energy. Crossbred lambs (n = 47; average age = 30 d) and their accompanying dams (n= 35) were assigned to one of two treatments using a completely randomized design with similar distributions of single and twin-born lambs and sexes. Treatment diets were formulated to be isonitrogenous and contained either wet (WMOL) or dry (DMOL) molasses. Dry molasses was added at 10% of the diet DM, whereas, wet molasses was added at 14.3% of the diet DM. Lambs were fed creep rations for 42 d prior to weaning. Creep feed was provided ad libitum and mixed grass hay was offered free-choice. Lamb weights were recorded weekly until weaning (d 42) and ewe BCS was measured at d 0 and d 42 (weaning). Overall lamb ADG was comparable (DMOL = 0.268 kg/hd, WMOL = 0.293 kg/hd; P = 0.30). Lamb weaning weights were similar between DMOL and WMOL (DMOL = 27.9 kg; WMOL = 27.5; P = 0.79). Ewe BCS was similar (P = 0.88) between DMOL and WMOL at 1.4 and 1.4, respectively. Estimated creep intake was calculated based upon total consumption following the end of the project and was found to be similar between treatments (DMOL = 0.54 kg/hd/d; WMOL = 0.59 kg/hd/d). Lamb pre-weaning growth and ewe performance was similar between DMOL and WMOL. Further research is needed to further explore the economic impact and use post-weaning.

Effects of Increased Growth Rates Prior to the First Breeding as Ewe Lambs and Pregnancy Rank on Mammary Glands of Two-Year-Old Ewes

This study investigated potential carry-over effects of increased growth rates prior to breeding at seven months of age on mammary glands of two-year-old ewes bearing one or two lambs, and examined the association between ewe mammary structures and the growth of their progeny. Ewe live weight and mammary ultrasound measures were recorded at 119 days of pregnancy, 29 days of lactation (L29), and weaning of the progeny (L79) in 64 two-year-old ewes selected from two treatments. The heavy group (n = 32) was preferentially fed prior to their first breeding at seven months of age, achieving an average live weight of 47.9 ± 0.38 kg. The control group (n = 32) weighed an average of 44.9 ± 0.49 kg at breeding. Lambs (n = 74) were weighed at birth, L29 and L79. Udder ultrasound measures did not differ (p > 0.10) between treatments, indicating no carry-over effects of treatments on mammary glands of two-year-old ewes. The association between ultrasound measures and lamb growth seemed to differ depending on lamb birth rank. More research is needed to further investigate these associations and determine whether ultrasonography could be used to identify ewes whose progeny would have greater growth rates based on birth rank.

Associations among Mammary Ultrasound Measurements, Milk Yield of Non-Dairy Ewe Lambs and the Growth of Their Single Lambs

Mammary cistern size was positively correlated with milk yield of mature dairy ewes, but the association in ewe lambs is unknown. This experiment aimed to examine the associations between mammary ultrasound measurements and the milk yield of ewe lambs at one year of age and to determine the accuracy of using maternal mammary ultrasound to predict single lamb growth rates. Single-bearing ewe lambs (n = 45) were randomly selected and 30 were milked once at weeks three (W3), five (W5), and seven (W7) of lactation. Mammary ultrasound scans were performed at day 110 of pregnancy, W3, W5, W7, and weaning (L69). Single lambs (n = 30) were weighed at birth and at each mammary scanning event. Udder measurements explained 26.8%, 21.4%, and 38.4% of the variation in milk yield at W3, W5 and W7, respectively, and 63.5% and 36.4% of the variation in single lamb growth to W3 and to L69. This ultrasound technique was more accurate in predicting single lamb growth to W3 than milk yield and may enable the identification of pregnant ewe lambs whose progeny would have greater growth rates. More research is needed to identify accurate indicators of superior milk yield and determine whether ultrasound could be used to select ewe lambs.

PSIII-5 Delaying Weaning Age of Lambs Grazing Chicory (Cichorium Intybus) Increases Body Weight

Two common challenges in forage-based lamb production systems is the restriction of net energy from grass-based pastures and the production losses associated with parasitic infection. The inclusion of nutrient rich forage in the diet and delaying lamb weaning age has shown to improve lamb growth rates in some systems. The objective of this experiment was to investigate the effects of grazing chicory (Cichorium intybus) and delayed weaning on the growth and health of young pasture-raised lambs. We hypothesized that improving the quality of available forage and delaying weaning would increase the body weight and parasite resilience of lambs. A total of 18 cross-bred ewes and 36 cross-bred lambs (25.2 ± 0.5 kg) were stratified by weight, sex, and randomly assigned to one of two weaning treatments: lambs weaned at 60 days of age (weaned) and lambs remained with their dam and weaned at 120 days of age (delayed weaned). Data were analyzed using PROC MIXED in SAS. Lamb body weight and indices of parasitism were measured every 14 days. There was a treatment × day effect for body weight as delayed weaned lambs were heavier on days 28, 42, and 56 compared with the body weight of weaned lambs (P < 0.02). In addition, there was a treatment × day effect for average daily gain (ADG) whereas delayed weaned lambs demonstrated greater ADG on days 14, 28, 42, and 56 compared with the ADG of weaned lambs (P < 0.02). In monitoring lamb health, there was a treatment × day effect as weaned lambs had a greater packed cell volume (PCV) on day 14 compared with the PCV of delayed weaned lambs (P < 0.03). Conversely, on day 56, weaned lambs had a lower PCV compared with the PCV of delayed wean lambs (P < 0.004). Delayed weaning has shown to be beneficial in improving lamb growth; however, in this instance, delayed weaning demonstrated variable responses in supporting lamb health while grazing on improved pastures.

Herbage Yield, Lamb Growth and Foraging Behavior in Agrivoltaic Production System

Agrivoltaic systems are designed to mutually benefit solar energy and agricultural production in the same location for dual-use of land. This study was conducted to compare lamb growth and pasture production from solar pastures in agrivoltaic systems and traditional open pastures over 2 years in Oregon. Weaned Polypay lambs grew at 120 and 119 g head−1 d−1 in solar and open pastures, respectively in spring 2019 (P = 0.90). The liveweight production between solar (1.5 kg ha−1 d−1) and open pastures (1.3 kg ha−1 d−1) were comparable (P = 0.67). Similarly, lamb liveweight gains and liveweight productions were comparable in both solar (89 g head−1 d−1; 4.6 kg ha−1 d−1) and open (92 g head−1 d−1; 5.0 kg ha−1 d−1) pastures (all P > 0.05) in 2020. The daily water consumption of the lambs in spring 2019 were similar during early spring, but lambs in open pastures consumed 0.72 L head−1 d−1 more water than those grazed under solar panels in the late spring period (P < 0.01). No difference was observed in water intake of the lambs in spring 2020 (P = 0.42). Over the entire period, solar pastures produced 38% lower herbage than open pastures due to low pasture density in fully shaded areas under solar panels. The results from our grazing study indicated that lower herbage mass available in solar pastures was offset by higher forage quality, resulting in similar spring lamb production to open pastures. Our findings also suggest that the land productivity could be greatly increased through combining sheep grazing and solar energy production on the same land in agrivoltaics systems.

Mammary Gland Structures Are Not Affected by an Increased Growth Rate of Yearling Ewes Post-Weaning but Are Associated with Growth Rates of Singletons

The experiment aimed to examine the impacts of an increased growth rate of ewes between three and seven months of age on udder development using ultrasound and to establish whether ultrasonography could be used to identify ewe mammary structures that may be indirect indicators of singleton growth to weaning. Udder dimensions, depths of gland cistern (GC), parenchyma (PAR) and fat pad (FP) were measured in late pregnancy (P107), early lactation (L29), and at weaning (L100) in 59 single-bearing yearling ewes selected from two treatments. The ‘heavy’ group (n = 31) was preferentially fed prior to breeding achieving an average breeding live-weight of 47.9 ± 0.38 kg at seven months of age. The ‘control’ group (n = 28) had an average breeding live-weight of 44.9 ± 0.49 kg. Udder dimensions, GC, PAR and FP did not differ between treatments. Lamb growth to L100 was positively associated (p < 0.05) with PAR at P107 and GC at L29. There was no evidence of negative effects of the live-weight gain treatments on udder development of yearling ewes as measured by ultrasonography. The results suggest that this ultrasound method has the potential to identify pregnant yearling ewes which would wean heavier singletons.