Low High Treatment Research Articles

The effects of feeding rations that differ in fiber and fermentable starch within a day on milk production and the daily rhythm of feed intake and plasma hormones and metabolites in dairy cows

A daily pattern of feed intake, milk synthesis, and plasma metabolites and hormones occurs in dairy cows fed a total mixed ration once or twice a day. The objective of this study was to determine if feeding multiple rations within a day, complementing these rhythms, would improve milk production. Twelve Holstein cows were used in a replicated 3×3 Latin square design with 21-d periods. Cows were housed in tie stalls with feed tubs, and feed weight was recorded every 10 s for observation of feeding behavior. Rations were a low fiber and high fermentable starch ration [LFHS; 27.4% neutral detergent fiber (NDF) and 31.7% starch based on 55.7% corn silage and 14.1% steam-flaked corn], a high fiber and low fermentable starch ration (HFLS; 31.7% NDF and 22.3% starch based on 44% corn silage, 26.3% alfalfa haylage, and no steam-flaked corn), and a total mixed ration that was a 1:3 ratio of LFHS and HFLS (30.7% NDF, 24.5% starch). The control treatment (CON) cows were fed the total mixed ration at 0700h, the high/low treatment (HL) fed HFLS ration at 0700h and LFHS ration at 2200h, and the low/high (LH) treatment fed LFHS ration at 0700h and HFLS ration at 1100h (LFHS and HFLS rations fed at a 1:3 ratio). No effect was found of treatment on daily milk, but LH decreased milk fat concentration and yield compared with HL (0.2 percentage units and 0.24kg, respectively). Daily dry matter and NDF intake and total-tract digestibility did not differ between treatments. The HL treatment reduced intake at the morning-conditioned meal after feeding and reduced intake before the evening feeding. A treatment by time of day interaction was found for fecal NDF and indigestible NDF concentration, blood urea nitrogen (BUN), plasma insulin, and fatty acid concentration, and body temperature. The CON and LH treatments increased the daily amplitude of fecal NDF by 1.0 and 1.1 percentage units compared with HL. Plasma insulin was higher in HL than CON at 0100 and 0400h, but lower at 1300 and 1900h. Plasma fatty acids were higher for CON than HL at 0700h and HL was lower than LH at 0400 and 1900h. Plasma BUN was higher for HL than control at 0100h, but lower at 1000h. Body temperature in CON and HL treatments followed a similar diurnal pattern, whereas body temperature for LH was lower than that of HL treatment at 1300 and 2300h. No daily rhythm was found of fecal indigestible NDF concentration, plasma glucose, or fatty acids detected in the HL treatment, and the amplitude of plasma insulin and BUN was lower for HL compared with CON (70 and 60% decrease, respectively). In conclusion, feeding 2 rations that differ in fiber and fermentable starch modifies diurnal rhythms in dairy cows. Furthermore, feeding a high fiber and low fermentable starch ration during the high intake period of the day may stabilize nutrient absorption across the day.

Strategic Feeding Alternating a 2-months’ Feeding Restriction and a Short Boost of the Feeding Level Increases Conception Rate in Sheep

<p class="1Body">This study aimed to investigate if feeding patterns prior to and after artificial insemination (AI) affect the reproductive performances of ewes. Two breeds were used; the Barbarine (n = 133) and Queue Fine de l’Ouest (QFO; n = 129). For each breed, 2 experimental groups balanced for age and live weight were formed. For 75 days before AI, ewes in treatment High daily grazed for 6 hours and were supplemented with 0.6 kg of concentrate. For those in treatment Low-High, grazing was restricted to 3 hours only. From 21 days before insemination and the following 20 days, feeding pattern for Low-High ewes was switched to the High feeding regime. Changes in live weight and ovarian activity were monitored; conception rate and litter size were recorded. At the end of the restriction period and for both breeds, Low-High ewes reached lower live weights than High ewes (p < 0.05). Prior to AI and for both breeds, Low-High ewes weighed less than those in the High treatment group but no statistical differences were observed. At the end of the restriction period, more QFO ewes were cycling than for the Barbarine breed (75/129 vs. 55/133; p < 0.01). Further, less QFO ewes in the Low-High treatment were cycling than High ewes (30/65 vs. 45/64; p < 0.01). More QFO ewes conceived to AI than Barbarine counterparts (77/112 vs. 73/130; p < 0.05). For both breeds, higher proportions of ewes in the Low-High treatment groups conceived to AI but differences reached statistical significance only for Barbarine breed. Following a food-restriction period between weaning and mating, improved conception rates are achieved if the plane of nutrition is increased few weeks prior to and after AI in comparison to a continuous increase in live weight during the same period.</p>

Genetic sexing strains of mediterranean fruit fly (Diptera: Tephritidae): quality in mass-reared temperature-sensitive lethal strains treated at high temperatures.

The high-temperature treatment of eggs of mass-reared tsl genetic sexing strains in Mediterranean fruit fly, Ceratitis capitata (Wiedemann), during late embryogenesis (the low-high protocol) conserves more male flies than treatment during early embryogenesis. A tsl strain, AUSTRIA 6-97, was constructed to follow the fate of aneuploid individuals during male-only production. Aneuploid individuals are produced following segregation in the translocation heterozygous males, and they can survive to the pupal stage where they compromise quality because they do not eclose as adults. Hatching, emergence, and male fly production were quantified and the heat-treatment protocol was characterized. The low-high egg treatment conserves the number of euploid-balanced males, and there is a very low survival of aneuploid males. After heat treatment of eggs, at least 95% of the male pupae were euploid compared with only 71% from untreated eggs. The quality of euploid male pupae was diminished with successive daily collections, an effect previously attributed to aneuploid survivors. Reduced yield of euploid males from early heat treatments was the result of an emergence effect, in addition to a maternal effect. A third detrimental effect of heat was found, occurring after hatching and before pupation, that reduces the survivorship of euploid males. The low-high treatment protocol yielded more males, with a higher accuracy than other heat treatments. However, although it avoids both the maternal and emergence effects, the production of euploid males was 30% less than the potential production, implying that the low-high heat protocol for killing female embryos in tsl genetic sexing strains can be fine-tuned.

Biological control ofBemisia argentifolii(Hemiptera: Aleyrodidae) on poinsettia with inundative releases ofEretmocerus eremicus(Hymenoptera: Aphelinidae): does varying the weekly release rate affect control?

AbstractThe effectiveness of varying weekly release rates of the parasitoidEretmocerus eremicusRose & Zolnerowich for control ofBemisia argentifoliiBellows & Perring on poinsettias was determined. Two variable release rate strategies forE. eremicuswere evaluated: a low–high and a high–low release regimen. In the low–high treatment, one female parasitoid was released per plant per week for seven weeks, then the release rate was increased to five female parasitoids per plant per week for the remaining seven weeks of the trial. In the high–low treatment, five female parasitoids per plant per week were released for the first seven weeks, then the release rate was reduced to one female parasitoid per plant per week for the final seven weeks of the trial. Both release rates averaged three female parasitoids per plant per week. Life-tables were made forB. argentifoliiin the presence and absence of parasitoids. In the absence ofE. eremicus, egg to adult survivorship forB. argentifoliiwas 65%. In low–high release greenhouses, average egg to adult survivorship forB. argentifoliiwas 6% and parasitism was 28%. In high–low greenhouses, average egg to adult survivorship forB. argentifoliiwas 5% and parasitism was 16%. Average net reproductive rates forB. argentifoliiin the absence of parasitoids was 17 indicating a rapidly increasing population. Net reproductive rates were 1.46 and 1.24 for low–high and high–low release greenhouses, respectively, indicating substantially reducedB. argentifoliipopulation growth. At week 14 of the trial, densities of live nymphs and pupae were lower in high–low greenhouses when compared to low–high greenhouses. Better whitefly control is achieved with inundative releases ofE. eremicuswhen this natural enemy acts as a predator as opposed to a parasitoid.

Frost hardiness of Thujaplicata and Pseudotsugamenziesii seedlings when nutrient supply varies with season

Seedlings of coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and western redcedar (Thujaplicata Donn ex D. Don) were subject to three nutrient treatments varying the rate of application of nitrogen (N) and phosphorus (P) over the growing season. A control treatment provided seedlings with a constant supply of N and P. A high–low treatment reduced the rate of N and P supply after mid-July. A low–high treatment initially supplied seedlings with low amounts of N and P, and then increased the rate of supply after mid-July. Foliar nutrient concentration of seedlings of each species from each nutrient treatment was measured in September and the following April. Cold tolerance of seedlings was assessed five times over the winter season by freeze-induced electrolyte leakage and twice by differential scanning calorimetry (DSC). Nutrient treatment did not significantly affect foliar nutrient concentration in either species. Height of Douglas-fir seedlings was also unaffected by nutrient treatment, but western redcedar seedlings in the control treatment were 6.3 cm taller than those in the high–low treatment. Interpolated damage at −13 °C from freeze-induced electrolyte leakage indicated that Douglas-fir seedlings from the control treatment had 19.8% less damage than high–low seedlings in October, 18% less damage in November, and 1.6% less damage in December. The same trend was evident, although not always significant, in western redcedar. Differential scanning calorimetry analyses of Douglas-fir in October and November showed freezing and melting curve onset and peak temperatures to be, on average, 2.3 °C and 0.4 °C warmer, respectively, in control seedlings than in high–low plants.

Dynamics of change of leaf attributes of Brussels sprouts in response to switches between high and low supply of nitrogen

In a greenhouse pot experiment with Brussels sprouts grown in sand, 4 treatments were compared: a control without N limitation, a continuously N-deficient control and 2 treatments with a switch from the high to the low supply or vice versa. All treatments received nutrient solution at 9 dates during the experiment. The high-N and low-N controls received 1.96 and 0.56 g/application, respectively. In the high-low treatment the switch from the higher to the lower application rate took place 57 days after planting (DAP) and in the low high treatment the reverse switch took place 85 DAP; these 2 treatments received the same total amount of N. Plant N concentrations changed rapidly upon changes in N supply regime. When the supply rate was increased, N concentration increased in leaves that had completed their expansion. Changes in leaf growth started about 15 days after the switch in N regime. Leaves that were expanding at the switch responded by increase in area when N supply increased without a change in mass, i.e. specific leaf area increased. Leaf areas and specific leaf area of expanding leaves decreased when the N supply became smaller. The control of leaf size during initiation and expansion is discussed.

The effect of level of nutrition prior to mating on the reproductive performance of ewes of two welsh breeds in different levels of body condition

ABSTRACTThe effects of high-low (HL) and low-high (LH) patterns of nutrition during the 5 weeks prior to a synchronized mating were studied on the reproductive performance of 115 Welsh Mountain and 114 Brecknock Cheviot ewes in a range of body condition at the start of treatment. For 2 months prior to treatment imposition, ewes were grazed in a systematic way at different stocking rates on different sward heights to obtain a range of body condition scores. Target score groupings were 2·00 to 2·25, 2·50 to 2·75 and 3·00 to 3·25 and although scores of 1·50 to 3·25 were obtained, most lay in the 2·00 to 2·75 range. Two treatment groups, balanced for live weight and body condition score, received high and low levels of nutrition for 16 days from mid October, achieved, respectively, by a low stocking rate on a sward with a high surface height plus ad libitum concentrate and a high stocking rate on a sward with a low surface height plus 200 g hay per head per day. Treatments were then reversed for the 17 days prior to mating. Live-weight and body condition-score changes were recorded and reproductive performance at first mating was measured from counts of corpora lutea and viable embryos at slaughter either at return to service or at 4 weeks after first mating. There were no differences due to nutritional pattern in live weight or body condition score at mating. The LH treatment significantly increased the rates of ovulation, conception, multiple ova survival and potential lambing per ewe pregnant and per ewe mated in the Welsh Mountain breed but significantly increased only the rates of ovulation and potential lambing per ewe pregnant in the Brecknock Cheviot breed compared with the HL treatment. The relatively poorer response in the latter breed was partially due to a lower ovulation rate potential coupled with non-significantly lower rates of conception and survival of single-shed ova associated with the LH treatment. Much of this relatively poorer reproductive performance in the Brecknock Cheviot breed was in ewes with body condition scores 3= 2·75. Reproductive performance increased with increasing body condition at the start of treatment over the range of scores =≤ 2·25 to 2·50 in both breeds and, while continuing to improve in scores above 2·50 in the Welsh Mountain breed, in the Brecknock Cheviot breed it started to decline. Ewes with a body condition score of 2·50 in both breeds showed the greatest response in potential lambing rate to the LH treatment.