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Dairy sheep breed genetic improvement programs have responded to the increasing market demand and popularity, especially for cheeses made from sheep's milk. These milk derivatives are an important source of bioactive substances for human health. Therefore, it is very important to learn about milk production (MPROD) and the factors that influence its variation. The typical pattern of MPROD during the period when an ewe is lactating is known as the lactation curve (LC), and this can be typical (TLC) or atypical (ACL). TLCs are characterized by reaching a maximum MPROD (lactation peak, LP) within a few days after parturition, and then gradually decreasing until the end of lactation, or lactation drying, is reached. ALCs are those that show some deviation from the normal pattern. It is important to know the graphical representation of lactation behavior, as, in addition to predicting MPROD, it makes it possible to identify health and feeding issues, as well as to select females that will excel in MPROD. Persistence of lactation (PER) has been defined as the rate of decline in MPROD after the LP was reached, and it is highly desirable for ewes to have a high PER. Mathematical models have been developed for the study of LCs and PER. There are genetic and environmental factors that influence LCs. [ABSTRACT FROM AUTHOR]

Aim of study: To estimate the heritability and genetic correlations for lactation curve traits in buffaloes. Area of study: The buffalo cows were raised on properties located in the states of São Paulo, Ceará and Rio Grande do Norte, Brazil. Material and methods: The individual parameters of Wood’s model ( , , and ) were obtained using a non-linear mixed model. Peak yield (PY), peak time (PT) and lactation persistency (LP) were also calculated. These individual parameters were employed in multi-trait analysis with the milk yield (MY) using Bayesian inference. Main results: The heritability estimates were of low to moderate magnitudes, with values ranging from 0.156 ( ) to 0.299 (PY). The estimates for genetic correlation between the Wood’s parameters and MY were of low to high magnitude and ranged from -0.533 ( and MY) to 0.983 (PY and MY). Research highlights: The heritability estimates obtained indicate that the traits studied can be used in animal breeding programs.

The objective of this study was to evaluate the use of calcium salts of fatty acids (CSFA) to increase the dietary energy levels for Saanen goats and their effects on the lactation curve, dry matter intake, body weight, and economic results of the goats. Twenty multiparous goats, weighing an average of 63.5±10.3 kg, were randomly assigned to one of four treatment groups, each receiving one of the following dietary energy levels: a control diet consisting of 2.6 Mcal of metabolizable energy per kg of dry matter (Mcal ME/kg DM) or a test diet supplemented with CSFA (Lactoplus®) to obtain 2.7, 2.8, or 2.9 Mcal ME/kg DM. Goats were housed in individual stalls and were fed and milked twice daily. The animals were evaluated until 180 days in milk by measuring dry matter intake and milk yield. These measurements were used to calculate feed efficiencies and the cost-benefit ratio of diet and lactation curves using Wood's nonlinear model. Increasing dietary energy levels showed no effect on body weight. Supplementation with CSFA did not limit dry matter intake; however, it changed the shape of the lactation curve by promoting a late peak lactation with a longer duration. Milk yields at 180 days in milk had a quadratic increase with a maximum energy level at 2.85 Mcal ME/kg DM. Increasing the dietary energy level for Saanen goats using CSFA changes their lactation curves, with the best milk production achieved with a 2.85 Mcal ME/kg DM diet; however, the greatest economic results were obtained with a 2.7 Mcal ME/kg DM diet.

The blood levels of glucose, total proteins, triglycerides, free fatty acids, total cholesterol, total proteins, albumnin, urea, total bilirubin were evaluated in peripartal and peak lactating dairy cows within physiological range. The measure values of the test parameters in puerperal dairy cows were stasticlly different from those in late gestation and peak lacting cows, wehich may be indicative of reduced gluconeogenisis rate in cows. The blood glucose levels in postpartal dairy cows were significantly bellow (p<0.05) those late -gestation and peak-lactation cows, which may be indicative of reduced gluconeogenesis rate in puerperal cows as induced by fat accumulation in the liver cells. Blood levels of free fatty acids were statistically highly significantly higher (p<0.01) in puerperal cows than in late-gesation and peak lactation cows suggesting a high degree of lipid moblisation from body depots in puerperal cows, resulting in the reestrification of fatty acids and their retention in triglyceride from the liver cells. The blood levels of trygicerides and total cholesterol in puerperal dary cows were statistically significantly lower (p<0.05) and inisigficantly lower (p>0.05), respectively, as compared to those in late -gestation and peak lactation cows, clearly indicating their increased accumulation in the liver parenchyma of early lactation cows. The average levels of total proteins, albumin and urea in puerperal cows were stasticlly significantly lower (p<0.05) as compared to those in late gestation and peak lactation cows, clearly suggesting that the fatty infiltration of liver cells induces a reduction in the synthetic capacity of hepatocites in puerpearal cows. The bilirubin levels were statisicaly higher significantly higer in puerperal cows (p<0.01) than in late-gesatation and peak-lactatating cows , being indicative of decreased excretory role of hepatocytes in puerperal cows. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to determine, using multiple logistic models, factors affecting pregnancy per AI (P/AI) following fixed-time artificial insemination (FTAI) in repeat breeders cows (RBC) treated with rbST throughout lactation. 498 RBC received a CIDR device and 100μg of GnRH on day 0. CIDR removal and PGF2α (25mg) treatment were done concurrently on day 7. Estradiol benzoate (EB, 1mg) was injected on day 8 and GnRH on day 9; cows were inseminated 16–20h later. Cows with an average milk protein <3% were 43% more likely (P <0.05) to become pregnant at FTAI than cows with milk protein ≥3%. Cows with <6 services had significantly increased chances of becoming pregnant than cows with ≥6 services at FTAI (P/AI 36 vs. 27%; P <0.05). CIDR-treated cows with less than three lactations were 1.7 times more likely (P/AI 35 vs. 21%; P <0.05) to become pregnant than cows in third or greater lactation. Cows with peak milk yields lower than 55kg were 1.5 times more likely to get pregnant than cows with peak milk yields greater than 55kg (P/AI 37 vs. 28%; P <0.05). P/AI was lower (30 vs. 35%; P <0.01) for cows with dry periods <62 days than cows with dry periods ≥62 days. Cows subjected to FTAI with a temperature–humidity index (THI) <76 were 45% more likely (P <0.05) to become pregnant than cows inseminated at a THI≥76. It was concluded that an acceptable proportion (32%) of RBC can become pregnant with the protocol used in the present study. Also, subfertility in CIDR-treated cows was associated with high peak yields, high milk protein, increased service, increased lactation, high THI at AI and short dry periods. [Copyright &y& Elsevier]

1. Small mammalian folivores, such as the koala, are considered to be energetically limited by their relatively small gut capacity compared with metabolic requirements and the gut-filling effect of their poorly digestible leaf diet. However, during peak lactation, female koalas increase their food intake (35%) to meet the nutritional demands of reproduction. 2. This study examines mechanisms by which reproductive female koalas overcome limitations to food intake. 3. Digesta retention in the gastrointestinal tract was measured in free-living koalas using inert solute (cobalt (Co) complexed with EDTA) and particle markers (chromium (Cr)-mordanted to cell wall constituents’ 600–1180 µm in diameter). 4. The whole gut rate of passage of both markers was 2–3 times faster than in captive koalas, probably because of 35%–69% greater food intakes in the wild. As in captive koalas, the solute marker was retained longer than the particle marker in free-living animals, indicating selective retention of fluid, solutes and small particles (including bacteria) in the hindgut caecum and proximal colon. The digesta retention of both markers were unaffected by the 35% increase in food intake associated with reproduction, largely due to a 42% increase in the solute marker pool size in lactating animals. The pool size of large particles in the digesta was unchanged. 5. Thus, female koalas meet the nutritional demands of reproduction at least partly by an increased solute digesta pool size, minimizing the detrimental effects of increased food intake on digestion of solutes and small particles, and on faecal loss of microbial protein. There was some indication that they also increase the passage rate of large particles or increase the efficiency of separation of large and small particles to reduce the gut-filling effects of large, poorly digestible particles. 6. Clearly the digestive strategy of the koala is more flexible, and limitations to food intake less stringent, than previously thought. Female koalas accommodate the increased food intake required to meet the demands of free-living and reproduction without compromising nutrient extraction from their eucalypt leaf diet. We suggest that similar flexibility in digestive strategy is likely to play an important role in the way that most small mammalian herbivores, especially arboreal folivores, meet the nutritional demands of reproduction. [ABSTRACT FROM AUTHOR]