Nutrient requirements of dairy cattle , Nutrient requirements of dairy cattle , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Nutrient requirements of dairy cattle

Effects of climate changes on animal production and sustainability of livestock systems

Environmentally induced periods of heat stress decrease productivity with devastating economic consequences to global animal agriculture. Heat stress can be defined as a physiological condition when the core body temperature of a given species exceeds its range specified for normal activity, which results from a total heat load (internal production and environment) exceeding the capacity for heat dissipation and this prompts physiological and behavioral responses to reduce the strain. The ability of ruminants to regulate body temperature is species- and breed-dependent. Dairy breeds are typically more sensitive to heat stress than meat breeds, and higher-producing animals are more susceptible to heat stress because they generate more metabolic heat. During heat stress, ruminants, like other homeothermic animals, increase avenues of heat loss and reduce heat production in an attempt to maintain euthermia. The immediate responses to heat load are increased respiration rates, decreased feed intake and increased water intake. Acclimatization is a process by which animals adapt to environmental conditions and engage behavioral, hormonal and metabolic changes that are characteristics of either acclimatory homeostasis or homeorhetic mechanisms used by the animals to survive in a new ‘physiological state’. For example, alterations in the hormonal profile are mainly characterized by a decline and increase in anabolic and catabolic hormones, respectively. The response to heat load and the heat-induced change in homeorhetic modifiers alters post-absorptive energy, lipid and protein metabolism, impairs liver function, causes oxidative stress, jeopardizes the immune response and decreases reproductive performance. These physiological modifications alter nutrient partitioning and may prevent heat-stressed lactating cows from recruiting glucose-sparing mechanisms (despite the reduced nutrient intake). This might explain, in large part, why decreased feed intake only accounts for a minor portion of the reduced milk yield from environmentally induced hyperthermic cows. How these metabolic changes are initiated and regulated is not known. It also remains unclear how these changes differ between short-term v. long-term heat acclimation to impact animal productivity and well-being. A better understanding of the adaptations enlisted by ruminants during heat stress is necessary to enhance the likelihood of developing strategies to simultaneously improve heat tolerance and increase productivity.

https://dspace.unitus.it/bitstream/2067/1536/1/FINAL%20ANIMAL%20repo_A77rkGLY.pdf

Metabolic and hormonal acclimation to heat stress in domesticated ruminants.

Staphylococci are the main aetiological agents of small ruminants intramammary infections (IMI), the more frequent isolates being S. aureus in clinical cases and coagulase negative species in subclinical IMI. The clinical IMI, whose annual incidence is usually lower than 5%, mainly occur at the beginning of machine milking and during the first third of lactation. These features constitute small ruminant peculiarities compared to dairy cattle. Small ruminant mastitis is generally a chronic and contagious infection: the primary sources are mammary and cutaneous carriages, and spreading mainly occurs during milking. Somatic cell counts (SCC) represent a valuable tool for prevalence assessment and screening, but predictive values are better in ewes than in goats. Prevention is most often based on milking machine management, sanitation and annual control, and milking technique optimisation. Elimination mainly relies on culling animals exhibiting clinical, chronic and recurrent IMI, and on drying-off intramammary antibiotherapy; this treatment allows a good efficacy and may be used selectively by targeting infected udders only. Heritability values for lactation mean SCC scores are between 0.11 and 0.15. Effective inclusion of ewe's mastitis resistance in the breeding goal has recently been implemented in France following experimental and large scale estimations of genetic parameters for SCC scores.

https://hal.archives-ouvertes.fr/hal-00902771/document

Mastitis of dairy small ruminants

As a complement to the concentration on negative states in welfare science, scientists are increasingly considering the desirability of measuring positive outcomes. Since evaluation of an animal’s mental state is a critical goal for welfare assessment, considerations of both positive feelings (what an animal “likes”) and resources that an animal is motivated to obtain (what an animal “wants”) appear to be important. However, since animals may make choices that are not in their long-term interests, an assessment of positive feelings and resources should include an evaluation of any associated actual or potential harms, such as fear, distress, pain, injury and disease. A review of current evidence suggests that positive welfare can be best assessed by evaluation of resources (i.e. inputs) that are valued by an animal and by positive outcomes such as behavioural responses, influences on cognitive processes and physiological markers. Since negative welfare is often inversely correlated with positive welfare measures, current welfare policy will have been achieving some positive welfare outcomes, however the explicit inclusion of positive welfare outcomes in the framework allows for analyses that are both deeper and more in tune with commonsense, which can hopefully yield more objective policies.

Assessment of positive welfare: A review

Effects of solar radiation and feeding time on behavior, immune response and production of lactating ewes under high ambient temperature.

Relationship between cortisol response to stress and behavior, immune profile, and production performance of dairy ewes.

http://directory.umm.ac.id/Data%20Elmu/jurnal/S/Small%20Ruminant%20Research/Vol37.Issue1-2.Jul2000/1899.pdf

Effect of parity on milk yield, composition, somatic cell count, renneting parameters and bacteria counts of Comisana ewes

Lambs prevented from suckling their mothers display behavioral, immune and endocrine disturbances.

Three groups of 12 lactating Comisana ewes were housed in separate rooms of the same building that contained straw-bedded pens with total areas of 12, 18 and 24 m2. The ewes were assigned to groups with different stocking densities: high (HSD, 1 m2/animal), medium (MSD, 1.5 m2/animal) or low (LSD, 2 m2/animal). The LSD treatment resulted in lower air concentrations of total microorganisms and coliform bacteria than the other two. Ewes in the LSD group gave greater yields of milk, total protein and fat than those in the other two groups. LSD treatment increased milk casein content and improved clotting time and clot firmness. LSD also resulted in ewes giving milk with lower somatic cell counts and smaller concentrations of mesophiles, psychrotrophs and faecal coliforms than MSD and HSD. Subclinical mastitis occurred in three ewes of the MSD group and four ewes of the HSD group, while no cases were recorded in the LSD group. These results indicate that stocking density is a critical factor in dairy sheep housing and suggest that a space allocation <2 m2/animal may adversely affect the performance and health of the lactating ewe.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022029999003726

G. Annicchiarico

Papers

Effects of solar radiation and feeding time on behavior, immune response and production of lactating ewes under high ambient temperature.

Relationship between cortisol response to stress and behavior, immune profile, and production performance of dairy ewes.

Effect of parity on milk yield, composition, somatic cell count, renneting parameters and bacteria counts of Comisana ewes

Lambs prevented from suckling their mothers display behavioral, immune and endocrine disturbances.

Effect of stocking density on ewes' milk yield, udder health and microenvironment.