Different Stages Of Lactation Research Articles

Comparison of different methods for monitoring of acid base status in dairy cow herds

Acid-base disorders in dairy herds can be diagnosed by determining urinary net base excretion (NBE). Modifications of this method are the differential NBE (dNBE) with determination of the urinary concentration-independent base-acid ratio (BAR) and the simplified NBE test with reduced urine volume (sNBE). The aim of this study was to compare these methods among themselves and as a pooled test, in their assessment of cow group acid base status as well as to derive recommendations for practical use. The concentrations of NBE, dNBE, and sNBE were measured in urine samples derived from 855 German-Holstein cows in 127 cow groups at different stages of lactation. BAR was then calculated. dNBE and BAR were determined both individually per cow and as a pool of a group. Mixed linear models were used to examine the relationship between the mean of the individual animal values and the pool sample result of a group for these two parameters. In addition, all groups were evaluated with respect to acidotic or alkalotic load based on their single animal results of the respective methods, the mean values formed from them, and the measured pool result. By using the single animal BAR as reference, the sensitivity and specificity of the different methods were calculated. The calculated mean values of the individual measurements of dNBE and BAR differed from the measured value in the pool sample, especially in low and high measurement ranges. In the group assessment, NBE showed the best combined sensitivity and specificity for the detection of acid base disorders. The dNBE pool assay showed satisfactory specificity with respect to acidosis and alkalosis, while the sNBE on an individual animal basis and the BAR determination in the pool showed satisfactory sensitivity with respect to acidosis. It was shown that NBE determined in individual animal samples is well suited for the assessment of acid base status of cow groups and can therefore be recommended for practical use. The determination of dNBE as well as BAR as a pool test is not sufficient for the detection of alkalotic load in cow groups but may help to confirm an existing acidotic load.

Melatonin in Human Breast Milk and Its Potential Role in Circadian Entrainment: A Nod towards Chrononutrition?

Breastfeeding is the most appropriate source of a newborn’s nutrition; among the plethora of its benefits, its modulation of circadian rhythmicity with melatonin as a potential neuroendocrine transducer has gained increasing interest. Transplacental transfer assures melatonin provision for the fetus, who is devoid of melatonin secretion. Even after birth, the neonatal pineal gland is not able to produce melatonin rhythmically for several months (with an even more prolonged deficiency following preterm birth). In this context, human breast milk constitutes the main natural source of melatonin: diurnal dynamic changes, an acrophase early after midnight, and changes in melatonin concentrations according to gestational age and during the different stages of lactation have been reported. Understudied thus far are the factors impacting on (changes in) melatonin content in human breast milk and their clinical significance in chronobiological adherence in the neonate: maternal as well as environmental aspects have to be investigated in more detail to guide nursing mothers in optimal feeding schedules which probably means a synchronized instead of mistimed feeding practice. This review aims to be thought-provoking regarding the critical role of melatonin in chrononutrition during breastfeeding, highlighting its potential in circadian entrainment and therefore optimizing (neuro)developmental outcomes in the neonatal setting.

Longitudinal modeling of residual carbon dioxide and residual feed intake in the Nordic Red dairy cattle

Feed utilization efficiency is an important trait in dairy production playing a significant role in reducing feed costs and lowering methane emission. One of the metrics used to measure feed efficiency in dairy cows is residual feed intake (RFI). This metric requires routine measurement of feed intake. Since there is a positive high correlation between heat production and carbon dioxide (CO2) production on the one hand and heat production and efficiency on the other hand, residual carbon dioxide (RCO2) might be a useful metric to improve feed efficiency. The objectives of this study were to model the trajectories of RCO2 and RFI as well as to estimate their repeatabilities and correlations at different stages of lactation. Daily CO2 output and feed intake were recorded from 46 primiparous Nordic Red dairy cows using two Greenfeed Emissions Monitoring™ systems from 2 to 305 days in milk (DIM). Edited data comprised 5 995 daily averages. To calculate predicted values of CO2 and DM intake (DMI), prediction models were developed by fitting multiple regression models to observations. Subsequently, RCO2 and RFI were calculated by subtracting predicted values of CO2 and DMI from their corresponding actual observations. A random regression bivariate model was fitted to estimate repeatabilities and animal correlations within lactation at different DIMs between RCO2 and RFI traits. The model fitted included fixed effects of year-month of recording, lactation month, fixed regressions as well as random regressions for the animal effect. The residual variance was considered to be heterogeneous. Repeatabilities and animal correlations of RCO2 and RFI between selected DIM (for every 30 DIM i.e., 6, 36,…, 246 and 276) were calculated. Repeatability of RCO2 was high at the beginning of lactation (0.72 at DIM 6) and decreased around the peak of milk production (0.27 at DIM 96) and again increased gradually toward the end of lactation. Similarly, RFI also had high repeatability at the beginning (0.86 at DIM 6); however, it decreased in mid-lactation (0.37 at DIM 156) and then increased toward the end of lactation. Animal correlations between RCO2 and RFI were moderate to high on the same DIM and ranged from 0.37 to 0.88. Overall, we found that animals with higher CO2 production than expected also consume more DMI than expected, but the moderate correlation between RCO2 and RFI found in this study calls for more research to assess the potential of RCO2 to become a new feed efficiency metric.

Influence of lactation stages on erythrocyte osmotic fragility of indigenous Badri cattle of Uttarakhand

The aim of this study was to evaluate the influence of lactation stages on erythrocyte osmotic fragility. The study was carried out using forty healthy Badri cows divided into five groups with eight animals in each group during different stages of lactation, viz. 1 (0 to 60 days), 2 (61 to 120 days), 3 (121 to 180 days), 4 (181 to 240 days) and 5 (non-lactating animals) as control animals. The per cent haemolysis of erythrocytes among different lactation groups was found significant at 0.9% during mid and early late lactation i.e. 2 and 3 group and 0.5% saline concentration during all stages of lactation as well as non- lactating animals.

Milk Composition and Productivity of Holstein Cows in Ryegrass Grazing and Crude Glycerin in The Diet

Objective: The aim of this project was to evaluate the effect of crude glycerin addition in the diet, milk composition and milk yield in dairy milking cows on different stages of lactation. Theoretical framework: It is necessary to balance the supply of protein and energy in the diet of lactating cows. Within this context, a by-product of the Biodiesel industry, called crude glycerin, is low cost and has a high energy value for ruminants, since its main component is glycerol, which ruminants have the capacity to use as a precursor gluconeogenic (Chung et al., 2007). Methods: The experiment was performed with Holstein cows (n=18), divided in two groups of treatment: 1) Basal diet without crude glycerin addition, 2) Diet with 10% of crude glycerin addition in the dry matter. Individual milk samples were collected for the analysis of the percentage of Fat, Protein, Lactose, Total Solids and Somatic Cell Count (Cs mL-1), as well as milk production (liters -1 and corrected for 4% fat). Results and conclusion: It was concluded that the addition of crude glycerin in the diet had no significant effect on the milk production and composition of cows of the Dutch breed. Originality/value: The study results have crucial implications for cow nutrition strategies. Implication of the research: The study results have crucial implications for strategies in the Nutrition of the cows.

The relationship of somatic cell count with milk yield and composition in different stages of lactation in Holstein cows

Globally, the milk yield of Holstein cows has increased considerably, but this situation has reduced the cows’ tolerance to environmental factors and, thus, it has negatively affected udder health and milk quality. This study aimed to determine the influence of somatic cell count (SCC) on milk yield and its composition in early (200 days) between November 2019 and August 2020. The study material consists of 927 records of 132 Holstein cows raised on a commercial dairy cattle farm in the Kırşehir province of Turkey. SCC was categorized into three groups (200x103 cell/mL). SCC data were logarithmically transformed to log10 base. In the study, logSCC, test day milk yield (MY), fat content (FC), solidsnot-fat (SNF), protein content (PC), lactose content (LC), fat yield (FY), and protein yield (PY) were recorded as 5.12±0.01, 37.54±0.34 kg, 3.59±0.02%, 9.08±0.01%, 3.35±0.01%, 4.99±0.01%, 1.33±0.01 kg, and 1.26±0.01 kg, respectively. LogSCC, MY, FC, SNF, PC, LC, FY, and PY were significantly affected by the parity, lactation stage, and sampling season (P200x103 cells/mL. Consequently, it may be that milk loss related to an increase in SCC was, consequently, highest toward the end of lactation. As a result, we suggest that prevalence measures should focus on reducing the incidence of SCC toward the end of lactation in Holstein cows.

Biochemical analytes during different stages of lactation in Surti buffaloes

Biochemical analytes during different stages of lactation in Surti buffaloes

Changes in hematological parameters during different stages of lactation in Surti buffaloes

Changes in hematological parameters during different stages of lactation in Surti buffaloes

Comparison of Total Antioxidant Capacity of Milk of Crossbred Holstein Friesian and Vechur Cattle during Different Lactation

Background: Milk is a rich source of vitamins, minerals, fats and high quality proteins. Milk proteins such as casein, lactoferrin and amino acids in milk like tyrosine, cysteine, tryptophan, lysine, etc. have antioxidant properties. The objective of this study was to compare the antioxidant level of milk of crossbred Holstein Friesian (CBHF) and Vechur cattle during different stages of lactation. Methods: Total antioxidant capacity (TAC) was estimated by using ferric reducing antioxidant assay. Milk samples from six animals each of CBHF and Vechur cattle were collected separately at early lactation, mid lactation and late lactation period. Results: Milk samples from CBHF and Vechur cattle during the early stages of lactation had significantly higher total antioxidant capacity than milk samples from later stages of lactation. This could be because of the high fat content in the early phases. The total antioxidant content of Vechur milk was higher than that of CBHF milk throughout lactation. The milk of the Vechur cow contains higher beta casein A2 than A1. No significant difference in the TAC values noticed between milk of mid and late lactation in both CBHF and Vechur cattle. The high antioxidant capacity of milk from Vechur cattle suggests that it has a great therapeutic potential. Different animal milk and milk products with antioxidant defense systems can be considered to have health-beneficial effects against free radical damage.

215 Optimizing the Standardized Ileal Digestible Lys-To-Net Energy Ratio for Nitrogen Utilization of Sows Throughout a 24-Day Lactation Period

Abstract Fifty multiparous sows (average parity 3.7±0.9 and initial BW 245.6±32.5 kg) were used to evaluate the effects of dietary standardized ileal digestible (SID) Lys-to-net energy (NE) ratios on nitrogen utilization throughout a 24-day lactation period. Sows were randomly assigned to one of five isoenergetic feeding programs that provided equally spaced and increasing Lys-to-NE ratios between 2.79 and 5.50 g SID Lys/Mcal NE. The feeding programs were generated by blending the two extreme diets in varying proportions using a precision feeding system and were provided to sows immediately after farrowing (d1) and until weaning at d 24 ± 1. At farrowing, litters were standardized to 12 piglets. Three nitrogen balances were conducted from d 4 to 7±1 (NB1), 12 to 15 ± 1 (NB2), and 20 to 23 ± 1 (NB3) using total urine collection and fecal grab sampling. Contrast statements were used to determine linear and quadratic effects of increasing Lys-to-NE ratios. Linear (LBL) and quadratic (QBL) broken-line and polynomial quadratic (QPM) models were used to determine the optimum dietary Lys-to-NE ratios for N retention. The Bayesian information criterion was used to assess best fit. Feeding program did not influence sow ADFI (5.96 ± 0.19 kg/d), BW change (-5.4 ± 4.1 kg) or change in backfat thickness (-2.0 ± 1.1 mm) over the entire 24-d lactation period, but piglet ADG increased with dietary Lys-to-NE ratio (linear; P < 0.05). Sow N intake increased with dietary Lys-to-NE ratio in NB2 and NB3 (linear; P< 0.001). Nitrogen retention (N intake – N output in urine and feces) increased with dietary Lys-to-NE ratio in all NB (linear; P = 0.05, P < 0.001, and P < 0.001 for NB1 -to 3, respectively). The QPM showed an inflection point at 3.75 g Lys/Mcal NE during NB1 and the QBL model showed break points at 2.87 and 4.83 g Lys/Mcal NE in NB2 and NB3, respectively. Nitrogen retention in milk increased with dietary Lys-to-NE ratio only in NB1 (linear; P < 0.05) and the QPM showed inflection points at 4.31, 4.37, and 4.90 g Lys/Mcal NE for NB1-to-3, respectively. Maternal nitrogen retention (N intake – N output in urine, feces, and milk) decreased and then increased in NB1 (quadratic; P < 0.01) and increased in NB2 and NB3 (linear; P < 0.01) with dietary Lys-to-NE ratio. The QPM showed inflection points at 4.01 and 3.01 g Lys/Mcal NE for NB1 and NB2, respectively, and the QBL model showed a breakpoint at 4.83 g Lys/Mcal NE for NB3. To optimize N retention, feeding programs with a Lys-to-NE ratio between 3.75 and 4.31, 2.87 and 4.37, and 4.83 and 4.90 g SID Lys/Mcal NE should be considered during early, mid, and peak lactation, respectively. Therefore, precision feeding programs can be developed to match the ideal SID Lys-to-NE ratio more closely at different stages of lactation to improve sow performance and reduce nitrogen excretion to the environment.

Identifying the Influence of the Dietary Polyunsaturated Fatty Acid Content on Milk Quality Traits in Najdi Sheep at Different Stages of Lactation

The quality of milk is fundamental to producing safe milk and dairy products that are suitable for consumption. The objective of this study was to determine the influence that the content of dietary polyunsaturated fatty acids (PUFA) has on the total mixed ration (TMR) and lactation stage of milk’s composition and the fatty acid profile (FA) of the dairy Najdi breed. During the lactation period, 48 Najdi ewes used the following four treatments: traditional feed (TR) and three total mixed rations (TMR1, TMR2, and TMR3) with different PUFA content. Milk samples were taken from whole milk in the morning. The chemical composition and FA profile were analyzed. The results show that the ewes fed TMR1 with a PUFA content (25.20%) produced high-quality milk as they contained high levels of polyunsaturated fatty acids (PUSF), linoleic acid (LA), α-linolenic acid (ALA) and omega-3 (n3). On the other hand, the milk of ewes fed TMR2 with PUFA (15.06%) contained high levels of unsaturated fatty acids (USF) and monounsaturated fatty acids (MUFA) and had significantly reduced hypercholesterolemia (HFA). It can be concluded that milk fat, protein, and total solids in the milk of Najdi sheep increased as lactation progressed, while lactose remained constant. Furthermore, as lactation progressed, saturated fatty acids (SFA), stearic acids, and oleic acids (OA) increased while USF and MUFA decreased. TMR diets can directly benefit the producer and livestock by producing high-quality milk while reducing its economic value.

Applying the Adjusted Chinese Dietary Balance Index-16 to Assess the Dietary Quality of Chinese Postpartum Lactating Mothers.

A balanced diet is considered necessary in maternal recovery and neonatal development; however, the dietary quality of lactating mothers in China has not been systematically evaluated in different regions and stages of lactation. In addition, the release of the Chinese Dietary Guidelines in 2022 implies that the dietary index method needs to be adjusted accordingly. In this study, the adjusted Chinese Dietary Balance Index-16 (DBI-16) was used to assess the dietary quality of lactating women, referred to as the Dietary Balance Index for lactating women (DBI-L). This study is part of the MUAI study, in which dietary intake and demographic characteristics of lactating mothers from six cities in China and at different stages of lactation were obtained through a self-administered questionnaire and a food frequency questionnaire; 2532 puerperal women were included. According to the DBI-L, 66.2% of participants had inadequate dietary intake (79.1% vegetables, 79.1% fruits, 86.7% dairy products, 39.7% soybeans, and 69.4% fish products, respectively), 57.8% had excessive intake (76.0% cereals, 64.4% meat, and 29.1% eggs, respectively) and 92.2% had unbalanced dietary consumption. Dietary quality was optimal for mothers in the first month after delivery, and the dietary quality of mothers in economically developed places such as Shanghai and Guangzhou was significantly better than that in less developed places such as Lanzhou and Changchun. The dietary quality of lactating women in China is imbalanced, with excessive and inadequate dietary intake. The country should strengthen nutritional interventions for lactating mothers, especially in economically underdeveloped regions.

An alternative remedy for the treatment of mastit in cows

Relevance. Mastitis in farm animals is widespread and ubiquitous and causes great economic damage to dairy cattle. The drugs used do not always give the desired results. The search of new highly effective methods and means of therapy for all forms of mastitis in cows is a top priority of scientific and practical veterinary workers.Methods. The therapeutic effect of the cream was carried out in the SPK «Red Partizan» of the Khunzakh region, on 90 dairy cows of the red steppe breed, on different stages of lactation, with inflammation of the skin of the nipples of the udder. Cows after milking were lubricated with inflamed nipples 2 times a day. In the experimental group 50 heads, inflamed nipples were smeared with a developed cream. In the second (control) group — 40 heads, the means used in this farm was used.Results. Studies have established that 98.0% recovered in the experimental group. The course of treatment was 3–4 days. It should be noted that in animals after 2–3 procedures of applying of the cream on the inflamed nipples, the skin became softer, dryness disappeared. On cracks and abrasions tissue, regeneration began and complete healing occurred on the 3–6th day. The animals tolerated the milking process more calmly. In the control group, 75.0% of cows were cured. Duration of treatment — 5–8 days.

Milk as an indicator of dietary imbalance.

Milk provides a readily available diagnostic fluid collected daily or more frequently on an individual animal or herd basis. Milk, as an aggregated sample in bulk tank milk (BTM) represents the status of a herd instead of a single animal. In this review, we examine the potential for milk to predict risks to efficient production, reproductive success, and health on the individual cow and herd level. For many conditions related to disorders of metabolism including hyperlipdaemia and ketonaemia, improved individual cow milk testing may allow a temporally useful detection of metabolic disorder that can target intervention. However, the extension of these tests to the BTM is made more difficult by the tight temporal clustering of disorder to early lactation and the consequent mixing of cows at even moderately different stages of lactation. Integrating herd recording demographic information with Fourier-transformed mid-infrared spectra (FT-MIR) can provide tests that are useful to identify cows with metabolic disorders. The interpretation of BTM urea and protein content provides useful indications of herd nutrition. These may provide indicators that encourage further investigations of nutritional influences on herd fertility but are unlikely to provide strong diagnostic value. The fat-to-protein ratio has a high specificity, but poor sensitivity for detection of fibre insufficiency and acidosis on an individual cow basis. Selenium, zinc, β-carotene, and vitamin E status of the herd can be determined using BTM. There appears to be increasing potential for the use of milk as a diagnostic fluid as more in-parlour tests become available for individual cows. However, the BTM appears to have under-utilised potential for herd monitoring.

Genetic parameter estimates for daily predicted gross feed efficiency and its association with energy-corrected milk in South African Holstein cattle

Genetic parameters for daily predicted gross feed efficiency (pGFE) and energy corrected milk (ECM) in the first three parities of South African Holstein cattle were estimated by repeatability animal models. Data comprised of 11,068 test-day milk production records of 1,575 Holstein cows that calved between 2009 and 2019. Heritability estimates for pGFE were 0.12 ± 0.06, 0.09 ± 0.04 and 0.18 ± 0.05 in early, mid and late lactation, respectively. Estimates were moderate for primiparous (0.21 ± 0.05) and low for multiparous (0.10 ± 0.04) cows. Heritability and repeatability across all lactations were 0.14 ± 0.03 and 0.37 ± 0.03, respectively. Genetic correlations between pGFE in different stages of lactation ranged from 0.87 ± 0.24 (early and mid) to 0.97 ± 0.28 (early and late), while a strong genetic correlation (0.90 ± 0.03) was found between pGFE and ECM, across all lactations. The low to moderate heritability estimates for pGFE suggest potential for genetic improvement of the trait through selection, albeit with a modest accuracy of selection. The high genetic correlation of pGFE with ECM may, however, assist to improve accuracy of selection for feed efficiency by including both traits in multi-trait analyses. These genetic parameters may be used to estimate breeding values for pGFE, which will enable the trait to be incorporated in the breeding objective for South African Holstein cattle.

Small ruminant lentivirus-infected dairy goats’ metabolic blood profile in different stages of lactation

Abstract The study aims to determine the differences in metabolic parameters in blood serum between asymptomatic animals with small ruminant lentivirus (SRLV) and uninfected goats. Pearson correlations were also estimated between biochemical parameters. The study included 26 goats which were divided into SRLV-infected and SRLV-free groups. Blood samples were taken at four points of lactation (days 14, 45, 85, and 240, reflecting perinatal period, early lactation, the peak of lactation, the end of lactation). Hepatic, kidney, bone, cardiac, pancreatic, lipid profiles and CRP concentrations were analyzed. Choline esterase (CHE), calcium (Ca*), creatine kinase (CK), and triglyceride (TRI) levels differed between groups, on day 240 (p≤0.05). Some parameters varied during lactation, with similar patterns observed in both groups. Mainly positive correlations between biochemical parameters were observed in the SRLV-free and SRLV-infected groups both within organ profiles and between them. CRP was not correlated with any biochemical parameters in the SRLV-free group but was negatively correlated with parameters of the liver, kidney, cardiac, and lipid profiles in the SRLV-infected group. The correlations suggest that SRLV may affect the kidneys, liver and heart, even in asymptomatic animals. Some differences were found between asymptomatic SRLV-infected and SRLV-free goats in the last stage of lactation; however, the nature of these changes requires further detailed studies.

Effects of Age, Calving Season and Specific Gravity of First Milking Colostrum on Milk Components and Somatic Cell Count in Early Lactation Anatolian Buffalo (Bubalus bubalis) Cows

This study aimed to evaluate the milk components and somatic cell count (SCC) of Anatolian buffalo cows at different stages of lactation (days 15th, 30th, 45th and 60th of lactation) by determining the effects of the age of the cow, calving season and specific gravity of colostrum (SGC) on these milk quality traits. The experiment was conducted using 62 healthy lactating primiparous and multiparous Anatolian buffalo cows at two private farms in Samsun, Türkiye. The SGC values at the second hour (first milking) after birth were measured using a colostrometer, and the milk components were analyzed using a milk analyser. In addition, the SCC in milk was measured with a portable cell counter. The data are divided into three groups: age (≤80 mo and >80 mo), calving season (spring and summer) and SGC (

Opportunities and limits of commercial farm data to study the genetic determinism of feed efficiency throughout lactation in dairy sheep.

The collective economic and environmental interest of the whole dairy sheep sector is to reduce feed costs and the negative impact of milk production on the environment. Thus, this study focused on the characterisation and genetic selection potential of feed efficiency in the Lacaune breed. Estimates for feed efficiency in dairy ewes are limited, mainly due to a lack of individual feed intake measurements in the sheepfold or in the pasture. We estimated the genetic parameters for two approximated (not entirely based on individual data) feed efficiency traits (lactation feed conversion ratio (LFCR) and residual energy intake (REI)) and daily milk yield (DMY) at different stages of lactation and throughout lactation. The accuracy of the efficiency traits was first evaluated on samples from Lacaune dairy ewes that were monitored individually, especially for their feed intake. Then, feed efficiency estimation methods were applied on eight commercial farms corresponding to 4680 Lacaune dairy ewes over two milk lactations (30854 records). Animals were collectively (for a large part of feed intake) or individually (for milk performance and dynamics of body fat reserves) monitored at different lactation stages. The heritabilities of LFCR and REI were estimated over lactations at 0.10±0.01 and 0.11±0.01, respectively. High genetic correlations were observed between the two efficiency traits and milk production traits, with a genetic correlation between LFCR and DMY of 0.74±0.04 and between REI and DMY of -0.79±0.04. A strong influence of environmental factors such as farm, year of milk production and lactation stage affected the genetic link between REI and milk production traits. Efficiency values observed in early lactation when animals were bred in the sheepfold were less genetically correlated with values obtained later in lactation when animals were grass-fed. However, individual characterisation of feed efficiency remains difficult due to the collective feeding context in dairy ewe farms.

Assessment of body conformation traits and their relationship with production performance of Sahiwal cows

Linear type scoring is key component in decision making process in the herd, as it focusses on the selection of animals with higher productive potential based on their body conformation/linear traits. The present study was carried out on 150 lactating Sahiwal cattle of first to fifth parity. Measurements on linear type traits were recorded 1 h before the evening milking at three different stages of lactation. The average score point of objective linear type traits was stature 5.77±0.08, chest width 4.59±0.10, body depth 5.24±0.10, rump width 5.56±0.09, rump angle 4.48±0.08, rear legs sets 4.81±0.12, foot angle 4.84±0.10, fore udder attachment 4.85±0.11, rear udder height 5.52±0.10, udder depth 5.31±0.08, rear udder width 4.27±0.09, central ligament 4.01±0.09, fore teat length 3.49±0.10, rear teat length 3.94±0.09, teat circumference 4.20±0.11, teat diameter 4.16±0.10 and udder balance 5.25±0.11. On the other hand, average score point of subjective linear type traits (1-9 scale) was angularity 4.69±0.09, rear leg rear view 5.05±0.06, body condition score 6.53±0.08, locomotion 4.88±0.06, fore teat placement 4.41±0.07 and rear teat placement 6.28±0.08. Most of the body conformation traits in Sahiwal cattle were falling under intermediate category and of desirable type. However, some traits like stature, chest width, body depth, rump width, angularity, central ligament, rear udder height, rear udder width and fore udder attachment expressed scope for further improvement.

PRODUCTIVE AND ECONOMIC PERFORMANCE OF BROWN SWISS COWS AT DIFFERENT STAGES OF LACTATION FED TWO CRUDE PROTEIN LEVELS

<p><strong>Background. </strong>Dairy cows convert between 24 to 32% of dietary nitrogen (N<sub>2</sub>) into milk protein, the rest of the dietary N<sub>2</sub> is excreted in urine and feces which contributes to environmental N<sub>2</sub> pollution. Besides the N<sub>2</sub> excretions, crude protein (CP) represents up to 69% of the diet´s total cost. Therefore, the best way to reduce environmental pollution and increase dairy profits is the reduction of crude protein in the diet of cows. <strong>Objective. </strong>To determine the productive and economic performance of Brown Swiss cows at different stages of lactation fed two crude protein levels 14 vs 16%. <strong>Methodology. </strong>Twenty-three multiparous Brown Swiss cows stratified by stage of lactation as early (EL), mid (ML), and late (LL) were used and subjected to two CP levels 14 and 16% on a crossover design with two experimental periods (EP) of three weeks each. Cows on experimental CP 14% in the EP1 switched to 16% in the EP-2, whereas cows that received a 16% diet in the first EP switched to 14% in the EP2. Milk-to-feed price ratio and income over-feeding cost were estimated as indicators of profitability. <strong>Results. </strong>The were no significant differences in any response variable due to dietary crude protein (P > 0.05), except for milk protein yield (kg/day) (P = 0.03), where 16% CP had higher yields (0.57) than 14% CP (0.55, kg/day). Cows in early and mid-lactation stages had higher performance than in late lactation (P < 0.05), on most of the response variables. Income over feeding-costs were 0.24 and 0.21 ($ USD/kg) for CP 14 and 16%, respectively. Total income over feeding cost per treatment was $1,020 for CP 14%, and $917 for CP 16%. <strong>Implications.</strong> The reduction of crude protein in the diet of lactating cows will allow reductions if milk production cost, as well as reductions of N<sub>2</sub> excretions to the environment. <strong>Conclusions. </strong>The productive performance of the cows was not affected by a reduction of crude protein in the diet, but the reduction of crude protein resulted in lower milk production cost and higher income-over feeding cost.</p>