Mathematical Modeling of Lactation Curves: A Review of Parametric Models

The mathematical representation of milk production against time represents one of the most successful applications of mathematical modeling in agriculture. Models provide summary information, which is useful in making management and breeding decisions. Several empirical mathematical functions have been proposed to describe the lactation curve of dairy cattle differing in mathematical properties, in the number of parameters and in their degree of relationships with the main features of a typical lactation pattern, such as peak yield, time at peak and persistency. This review gives an overview of the parametric models used to fit of lactation curves in dairy cattle. Parametric models are those that found large application to fit the lactation curves, basically due to their limited mathematical complexity, and their abilities to fit a large kind of curves. Models to describe the lactation curve have been classified into two main groups: linear and nonlinear models. Nonlinear parametric functions have represented the preferred tools for modeling lactation curves with the main aim of predicting yields and parameters describing the shape of the curve in addition to important parameters such as peak yield and persistency. Nonlinear models need iterative techniques to be solved. Different iterative methods frequently employed in nonlinear regression models are Marquardt, Newton, Gauss and Dud. Wood model was the most popular parametric model with the largest application can be found in the immediate and easy understanding of relationships between its parameters and main curvatures of the lactation pattern

Učinci obroka i godišnjih doba na mliječnost i sastav mlijeka na malim i srednjim mliječnim farmama iz sjevernog područja Tunisa (regija Bizerte)

In Tunisia, dairy farming faced several problems limiting the improvement of the milk sector, mostly at the level of small farmers. These difficulties are related to the milk quality affected by the feed quality distributed throughout the year. This study aimed to evaluate the effect of rations and seasons on daily individual milk production (DIMP) and some physicochemical characteristics (Fat content: FC, Protein content: PC, Urea concentration: UC, Total Solids: TS). A survey and milk samplings were performed on 135 farmers. Collected data were treated by the variance analysis using the GLM procedure of the SAS system. This study allowed to identify four types of ration: TR1: Concentrate (CC)+Green Forage(GF), TR2: CC+Dry Forage (DF), TR3: CC+GF+DF and TR4: Diet containing Silage (S), used by farmers with the frequencies of 14.82, 37.19, 44.6 and 3.38 % respectively. The highest DIMP (P<0.0001) was obtained by TR1 (17.3 kg/day) and the lowest (13.6 kg/day) by TR2. TR4 allowed FC, PC (P<0.05) and TS (P<0.01) higher (3.84, 3.14 and 12.31 % respectively) than those obtained in the other rations. The UC (P<0.0001) was the highest in TR1 and TR3 (32.05 mg/dL) followed by TR4 (28.3 mg/dL) and TR2 (26.2 mg/dL). Concerning the season effect, the highest DIMP (P<0.0001) was obtained during spring (17.7 kg/day), the lowest was during autumn (13.1 kg/day). The FC (P<0.05) was the lowest in winter (3.52 %). The PC (P<0.01) was higher during autumn and winter (averaged 3.07 %). The UC (P<0.0001) was the highest in spring (32.23 mg/dL) and the lowest in autumn (25.67 mg/dL). It was concluded that milk parameters were in the acceptable ranges comparatively to the national averages.U Tunisu se mljekarstvo suočilo s nekoliko problema koji ograničavaju poboljšanje mliječnog sektora, uglavnom na razini malih poljoprivrednika. Te su poteškoće povezane s kvalitetom mlijeka na koju utječe kvaliteta hrane koja se distribuira tijekom cijele godine. Cilj ovog rada bio je procijeniti učinak obroka i godišnjih doba na dnevnu individualnu proizvodnju mlijeka (DIMP) i neke fizikalno-kemijske karakteristike (sadržaj masti: FC, sadržaj proteina: PC, koncentracija uree: UC, ukupna suha tvar: TS). Istraživanje i uzorkovanje mlijeka provedeno je na 135 mliječnih farmi, a prikupljeni podaci obrađeni su analizom varijance korištenjem GLM postupka SAS sustava (verzija 9.0, 2002). Ova studija utvrdila je utjecaj četiri vrste obroka: TR1: koncentrat (CC)+zelena krma (GF), TR2: CC +suha krma (DF), TR3: CC+GF+DF i TR4: obrok koji sadrži silažu (S). Najviša DIMP (P<0,0001) dobivena je korištenjem TR1 (17,3 kg/dan), a najmanja (13,6 kg/dan) kod TR2. TR4 povezan je sa većim sadržajem FC, PC (P<0,05) i TS (P<0,01) (3,84, 3,14 i 12,31 %) od vrijednosti uočenih u ostalim obrocima. UC (P<0,0001) bio je najviši kod TR1 i TR3 (32,05 mg/dL), zatim kod TR4 (28,3 mg/dL) i TR2 (26,2 mg/dL). Kada je riječ o sezonskom učinku, najveća DIMP (P<0,0001) je tijekom proljeća (17,7 kg/dan), a najmanja tijekom jeseni (13,1 kg/dan). FC (P<0,05) bio je najniži zimi (3,52 %). PC (P<0,01) bio je veći tijekom jeseni i zime (u prosjeku 3,07 %). UC (P <0,0001) bio je najveći u proljeće (32,23 mg/dL), a najmanji u jesen (25,67 mg/dL). Zaključeno je da su parametri mlijeka u prihvatljivim rasponima u usporedbi s nacionalnim prosjecima

Određivanje glavnih čimbenika koji utječu na prinos i sastav kozjeg mlijeka u sjeverozapadnoj regiji Tunisa

This study aimed to assess the main factors affecting goat milk yield and composition from the Northwest region of Tunisia. A survey and a sampling campaign were conducted over four months (February-May, 2018), within 112 farms in 3 regions. Individual daily milk yield (DMY) was registered and milk samples were taken in duplicate to be analysed for fat (FC), protein (PC), solid not fat (SNF), density and lactose contents. Results showed that the Alpine breed allowed the highest DMY and PC, and the Damasquine presented the highest FC. The third lactation allowed the highest DMY (0.95 Lday-1) and FC (6.68%), however the highest PC, SNF and density are recorded for primiparous. Concerning the birth weight of kids, DMY increased significantly with the weight of the kids at birth, and it resulted in a significant effect on the FC. The assessment of the region effect showed that the highest DMY was obtained in the region of Jendouba and Ghardimaou. For milk composition, when breed effect was eliminated and focused only on the local breed, we found the highest FC in Sedjnen/Nefza. The analysis of the goat feeding allowed identifying 5 types of rations. Also, statistical analysis showed that the highest DMY resulted from the rations T4 and T5 (averaged 1.06 Lday-1). No effect of ration type on FC and density was found. Concerning PC, SNF and lactose, the ration effect had no significant effect, but a trend of highest values was noted for T3. It was concluded that dairy performances were low, focusing only on the local goat population. However, the produced milk is of good quality regarding the determined chemical composition. Indeed, there is a negative correlation between milk production and the chemical composition of milk. Substantial improvements are potentially possible through actions (improvement of the quality of the ration, milk hygiene, milk collection pattern, training of breeders, etc) to develop a value chain in the region and improve farmer incomes.Cilj ovog istraživanja bio je odrediti glavne čimbenike koji utječu na prinos i sastav kozjeg mlijeka iz sjeverozapadne regije Tunisa. Istraživanje i uzorkovanje provedeni su tijekom dva mjeseca (ožujak-travanj 2018.) na 112 farmi u 3 regije. Bilježen je pojedinačni dnevni prinos mlijeka (DMY) te su uzorci mlijeka uzeti u duplikatu za analizu udjela masti (FC), proteina (PC), suhe tvari bez masti (SNF), gustoće i udjela laktoze. Rezultati su pokazali da je alpina pasmina imala najveći DMY i PC, a damaška najveći FC. U trećoj laktaciji je utvrđen najveći DMY (0,95 Ldan-1) i FC (6,68 %), dok su najveći PC, SNF i gustoća zabilježeni kod prvojarki. Uzimajući u obzir porođajnu masu jaradi, DMY se značajno povećao s masom jaradi pri jarenju, što je značajno utjecalo na FC. Analiza učinka regije pokazala je da je najveći DMY postignut u regiji Jendouba i Ghardimaou. Kada je o sastavu mlijeka riječ, nakon što se eliminira učinak pasmine, i usredotoči samo na lokalnu pasminu, najveći FC utvrđen je u regiji Sedjnen/Nefza. Analiza hranidbe koza omogućila je identificiranje 5 vrsta obroka. Također, statistička analiza pokazala je da je najveći DMY rezultat omjera T4 i T5 (prosječno 1,06 Ldan-1), dok nije utvrđen utjecaj vrste obroka na FC i gustoću. Utjecaj vrste obroka nije značajno utjecao na PC, SNF i udio laktoze, ali je zabilježen trend najviših vrijednosti za T3. Zaključeno je da su mliječne performanse bile niske, ako se u obzir uzme samo lokalna populacija koza. Međutim, kvaliteta proizvedenog mlijeka je bila dobra uzimajući u obzir utvrđeni kemijski sastav. Također, utvrđena je negativna korelacija između proizvodnje mlijeka i kemijskog sastava mlijeka. Značajna poboljšanja potencijalno su moguća primjerice kroz poboljšanje kvalitete obroka, higijene mlijeka, obrasca prikupljanja mlijeka i obuke uzgajivača za razvoj lanca vrijednosti u regiji te tako i povećanje prihoda farmera

Insects as an alternative protein source for poultry nutrition: a review

This review summarizes the most relevant scientific literature related to the use of insects as alternative protein sources in poultry diets. The black soldier fly, the housefly, the beetle, mealworms, silkworms, earthworms, crickets, and grasshoppers are in the spotlight because they have been identified as an important future source of sustainable animal proteins for poultry feeding. Insect meals meet poultry requirements in terms of nutritional value, essential amino acid composition, nutrient digestibility, and feed acceptance. Furthermore, they are enriched with antimicrobial peptides and bioactive molecules that can improve global health. Results from poultry studies suggest equivalent or enhanced growth performances and quality of end-products as compared to fish meal and soybean meal. To outline this body of knowledge, this article states established threads of research about the nutrient profiles and the digestibility of insect meals, their subsequent effects on the growth and laying performances of poultry as well as the quality of meat, carcass, and eggs. To fully exploit insect-derived products, the effects of insect bioactive molecules (antimicrobial peptides, fatty acids, and polysaccharides) were addressed. Furthermore, as edible insects are likely to take a meaningful position in the feed and food chain, the safety of their derived products needs to be ensured. Some insights into the current knowledge on the prevalence of pathogens and contaminants in edible insects were highlighted. Finally, the effect of insect farming and processing treatment on the nutritive value of insect larvae was discussed. Our overview reveals that using insects can potentially solve problems related to reliance on other food sources, without altering the growth performances and the quality of meat and eggs

Titanium Dioxide Nanotubes as Solid-Phase Extraction Adsorbent for the Determination of Copper in Natural Water Samples

International audienceTo increase the sensitivity of the analysis method of good copper sample preparation is essential. In this context, an analytical method was developed for sensitive determination of Cu (II) in environmental water samples by using TiO2 nanotubes as a solid-phase extraction absorbent (SPE). Factors affecting the extraction efficiency including the type, volume, concentration, and flow rate of the elution solvent, the mass of the adsorbent, and the volume, pH, and flow rate of the sample were evaluated and optimized. TiO2 nanotubes exhibited their good enrichment capacity for Cu (II) (~98%). Under optimal conditions, the method of the analysis showed good linearity in the range of 0–22 mg L−1 (R2 > 0.99), satisfactory repeatability (relative standard deviation: RSD was 3.16, n = 5), and a detection limit of about 32.5 ng mL−1. The proposed method was applied to real water samples, and the achieved recoveries were above 95%, showing minimal matrix effect and the robustness of the optimized SPE method

Application of Doehlert Experimental Design for Optimization of a New-Based Hydrophilic Interaction Solid-Phase Extraction of Phenolic Acids from Olive Oils

In this work, a rapid, precise, and cost-valuable method has been established to quantify phenolic compounds in olive oil using new-based hydrophilic interaction solid-phase extraction (SPE). Boehlert&rsquo;s experimental design applied the determination of the optimal operating conditions. An investigation into the effects of the methanol composition (50&ndash;100%), the volume of eluent (1&ndash;12 mL), and pH (1&ndash;3) on the extraction of phenols acids and total phenols from Tunisian olive oils was performed. The results showed that the extraction conditions had a significant effect on the extraction efficiency. The experiment showed that the greatest conditions for the SPE of phenolic acids were the methanol composition at 90.3%, pH at 2.9, and volume at 7.5 mL, respectively. The optimal conditions were applied to different types of olive oils, and it could be concluded that larger concentrations of polyphenols were found in extra virgin olive oil (89.15&ndash;218), whereas the lowest levels of these compounds (66.8 and 5.1) were found in cold-pressed crude olive oil and olive pomace oil, respectively

Application of Doehlert Experimental Design for Optimization of a New-Based Hydrophilic Interaction Solid-Phase Extraction of Phenolic Acids from Olive Oils

In this work, a rapid, precise, and cost-valuable method has been established to quantify phenolic compounds in olive oil using new-based hydrophilic interaction solid-phase extraction (SPE). Boehlert’s experimental design applied the determination of the optimal operating conditions. An investigation into the effects of the methanol composition (50–100%), the volume of eluent (1–12 mL), and pH (1–3) on the extraction of phenols acids and total phenols from Tunisian olive oils was performed. The results showed that the extraction conditions had a significant effect on the extraction efficiency. The experiment showed that the greatest conditions for the SPE of phenolic acids were the methanol composition at 90.3%, pH at 2.9, and volume at 7.5 mL, respectively. The optimal conditions were applied to different types of olive oils, and it could be concluded that larger concentrations of polyphenols were found in extra virgin olive oil (89.15–218), whereas the lowest levels of these compounds (66.8 and 5.1) were found in cold-pressed crude olive oil and olive pomace oil, respectively

Assessment of Meat-Type Sheep Welfare Using Animal-Based Measures

This study aimed to assess the welfare of Tunisian sheep in extensive sheep production systems using animal-based measures of ewe welfare. This study encompasses the first national survey of sheep welfare in which animal-based outcomes were tested. Animal-based welfare measures were derived from previous welfare protocols. Fifty-two Tunisian farms were studied and a number from 20 to 100 animals by flock were examinated. The whole flock was also observed to detect clinical diseases, lameness, and coughing. The human-animal relationship was selected as welfare indicators. It was evaluated through the avoidance distance test. The average avoidance distance was 10.47 ± 1.23 and 8.12 ± 0.97 m for a novel person and farmer, respectively. The global mean of body condition score (BCS) was 2.4 with 47% of ewes having a BCS of two, which may be associated with an increased risk of nutritional stress, disease, and low productivity. Ten farms had more than 7% of lambs with a low body condition score, which may be an indication of a welfare problem. The results obtained in the present study suggest that the used animal-based measures were the most reliable indicators that can be included in welfare protocols for extensive sheep production systems