Nutrition and reproduction in dairy cows

The effects of rumen protected methionine supplementation on the performance of primiparous dairy cows using the Presynch-Ovsynch protocol

The purpose of this study was to examine the effects of rumen-protected methionine (RPM) supplementation on the reproductive and productive performance of primiparous dairy cows fed two levels of protein. The Presynch-Ovsynch protocol was used to synchronize 36 lactating Holstein cows that were assigned randomly to one of six dietary treatments: (1) 14% CP and without RPM diet (14CP-0RPM; n = 6), (2) 14% CP and 15 g/head/day RPM (14CP-15RPM; n = 6), (3) 14% CP and 25 g/head/day RPM (14CP-25RPM; n = 6), (4) 16% CP and without RPM diet (16CP-0RPM; n = 6), (5) 16% CP and 15 g/head/day RPM (16CP-15RPM; n = 6), and (6) 16% CP and 25 g/head/day RPM (16CP-25RPM; n = 6). Independent of CP levels, feeding RPM had reduced the calving interval (P < 0.01). Feeding RPM increased (P < 0.01) overall plasma progesterone (P4). Feeding 16CP-15RPM increased (P < 0.01) overall plasma P4. Feeding 16% CP increased (P < 0.01) 4% fat corrected milk, energy corrected milk, milk fat and protein yield, and milk casein. Moreover, feeding the 25RPM has increased (P < 0.01) 4% fat corrected milk, energy corrected milk, milk fat, and protein yield. Compared with other treatments, feeding 16CP-25RPM or 16CP-15RPM enhanced (P < 0.01) milk yield and milk fat yield. In conclusion, feeding 16% CP with RPM boosted the productivity and reduced the calving interval in primiparous lactating dairy cows.

Retinol deficiency in animals: Etiopathogenesis and consequences

Infertility is widespread for all species of animals and causes significant economic losses to livestock due to the loss and shortage of offspring, their reduced viability and, consequently, increased morbidity and mortality. Alimentary-deficiency factors are among the commonest causes of infertility, from which A-vitamin deficiency should be singled out. The precursor of vitamin A in the body is carotene, which is an unstable compound which is easily destroyed even under the influence of moderate factors of influence, in connection with which its deficiency is global, especially at the end of the winter – stall period of keeping animals. Accordingly it is the leading etiological factor of retinol deficiency infertility. As a result, the body has two negatives that act in parallel: carotene / vitamin A deficiency adversely affects the organs, the constituent and major functional unit of which is the secretory epithelial cell, and the free radical oxides formed in high concentration are extremely effective in destroying the cells, weakening antioxidant protection. Vitamin A has a significant effect on the reproductive function of animals both directly and indirectly. It is necessary to ensure the structure and functioning of the epithelial tissues of the organs of regulation and performance of sexual function, and therefore the physiological development of the fetus and the course of pregnancy, parturition and postpartum period, ovo- and spermiogenesis, the manifestation of sexual reflexes. Instead, its deficiency underlies the etiology and pathogenesis of retinol deficiency infertility of animals, causing changes in individual indices of homeostasis and prooxidate-antioxidant system, morphostructure of the reproductive and endocrine organs, hormonal status, sperm quality and reproductive function. The consequence is the emergence and development of gynecological, andrological, mammological and perinatal (ante-, intra-, post- and neo-) pathologies. At the same time, the addition of carotene or retinol to the diets of animals or their oral administration in cases of deficiency of vitamin A prevents impaired reproductive function. The study of the features of the etiopathogenesis of retinol deficiency infertility of animals allows programs of complex diagnostics, therapy and prevention to be developed which provide determination of carotene and vitamin A content and replenishment of the organism in cases of their deficiency.

Postcalving factors affecting conception risk in Holstein dairy cows in tropical and sub-tropical conditions

The objective was to identify postpartum risk factors between nutritional imbalance and health disorders affecting first-service conception risk (FSCR) in 21 commercial Holstein herds in Reunion Island. Multivariate logistic-regression models including herd as a random effect were used to analyze the relationship between FSCR and energy status, nitrogen status, hepatic function, mineral deficiencies, and postpartum health disorders. Two models (A and B) were built on two subsets of data (n=446 and n=863) with risk indicators measured during the first month of lactation and around time of first service, respectively, adjusted for season, breed, parity, origin, milk yield, calving to first service interval (CS1), and type of estrus (spontaneous vs. induced). The averaged conception risk was 0.266+/-0.015 (n=913) (mean+/-S.E.M.). In both models, FSCR was decreased by CS1 < or = 60 d and induced estrus. In model A, FSCR was decreased (p<0.05) for cows with mean cumulative 100 d daily milk yield < or =23 kg/d and >27 kg/d, with losses of body condition score >1.5, and with retained placenta. In model B, FSCR was decreased (p<0.05) for cows inseminated during wet season, previously raised out of the farm as nulliparous, with blood magnesium concentration < or =0.9 mmol/L, and for high-yielding cows (100 d milk yield > 27 kg/d) with glutamate deshydrogenase>17 UI/L. Hence, high-body-lipid mobilization during the first month of lactation was a strong nutritional predictor of low FSCR together with liver damage in high-yielding cows. Interestingly, our models revealed that infertility is better related to nutritional factors than to postpartum health disorders occurrence.

Body condition and suckling as factors influencing the duration of postpartum anestrus in cattle: a review

Prolonged postpartum anestrus is a main factor limiting reproductive efficiency in cattle, particularly in Bos indicus and Bos taurus/Bos indicus cows from tropical regions, because it prevents achievement of a 12 month calving interval. During anestrus, ovulation does not occur despite ovarian follicular development, because growing follicles do not mature. Although many factors affect postpartum anestrus, nutrition and suckling are the major factors influencing the resumption of postpartum ovarian cycles, as they affect hypothalamic, pituitary and ovarian activity and thus inhibit follicular development. Under-nutrition contributes to prolonged postpartum anestrus, particularly among cows dependent upon forages to meet their feed requirements and it apparently interacts with genetic, environmental or management factors to influence the duration of anestrus. The nutritional status or balance of an animal is evaluated through body condition score (BCS), as it reflects the body energy reserves available for metabolism, growth, lactation and activity. There is a converse relationship between energy balance and time to resumption of postpartum ovarian activity; inadequate nutrient intake results in loss of weight and BCS and finally cessation of estrous cycles. Suckling interferes with hypothalamic release of GnRH, provoking a marked suppression in pulsatile LH release, resulting in extended postpartum anestrus. The effects of suckling on regulation of tonic LH release are determined by the ability of the cow to identify a calf as her own or as unrelated. Vision and olfaction play critical roles in the development of the maternal-offspring bond, allowing the cow to identify her own calf, and abolition of both senses attenuates the negative effects of suckling on LH secretion. Thus, the maternal-offspring bond is essential for prolonged postpartum suckling-induced anovulation, and the suppressive influence of suckling is independent of neurosensory pathways within the teat or udder.

Milk yield and composition, nutrition, body conformation traits, body condition scores, fertility and diseases in high-yielding dairy cows--Part 1

Twenty-nine pairs of high-yielding dairy cows (HC; > or = 45 kg/day reached at least once during lactation) and corresponding control cows (CC; with milk yields representing the average yield of the herds) were examined on 29 Swiss farms from March 1995 to September 1996. The hypotheses were tested that there are differences in feed intake, body-conformation traits, body weight (BW), body condition score (BCS), fertility status and disease incidence between HC and CC cows. Cows were studied 2 weeks before and at 5, 9, 13, 17 and 40 weeks post-partum. HC cows produced more energy-corrected milk (ECM) than CC cows (10,670 +/- 321 kg in 293 +/- 5 days and 8385 +/- 283 kg in 294 +/- 4 days, respectively; P < or = 0.001) and yields in the first 100 days of lactation were greater in HC than in CC cows (46.2 +/- 1.1 and 36.2 +/- 1.0 kg ECM/day, respectively; P < or = 0.001). Concentrate intake was greater (P < or = 0.05) in HC than in CC cows (7.6 +/- 0.5 and 5.7 +/- 0.5 kg/day, respectively) and dry matter intakes (measured in week 5 of lactation over 3 days on six farms) were greater in HC than in CC cows (24.0 +/- 1.1 and 20.3 +/- 1.1 kg/day, respectively; P < or = 0.001). HC cows were taller than CC cows (wither heights 143.3 +/- 0.8 and 140.1 +/- 0.8 cm, respectively; P < or = 0.01). Although BW in HC cows was greater than in CC cows throughout the study, differences and decreases of BW during lactation were not significant. BCS at the end of pregnancy and decrements during lactation were similar in HC and CC cows. Fertility parameters were similar in HC and CC cows. Incidences of mastitis, claw and feet problems, hypocalcemia/downer cow syndrome, ovarian cysts and abortions were similar in HC and CC cows, but there were more indigestion problems in HC than in CC cows.

Uterine bacteriology, histology, resumption of ovarian activity and granulocyte function of the postpartum cow in different milking frequencies

The postpartum uterine bacteriology, histology, resumption of ovarian activity and polymorphonuclear granulocyte (PMN) number and function in 18 Swedish dairy cows were studied. Cows were milked either 2x (n = 9) or 3x per day (n = 9). Endometrial biopsy samples for bacteriological and histological investigations were collected during 8 weeks postpartum, starting within one week after calving. Milk samples for progesterone determination were collected twice a week until the cows had shown normal reproductive cyclicity. Blood samples for granulocyte function (phagocytic capacity and total number) were collected from each animal on the same days as when the biopsies were obtained. All animals in both groups were free from bacteria at the latest after 6 weeks post-partum and there was no difference regarding bacterial elimination and bacterial species between milking groups. No difference regarding uterine histology between milking groups was seen. In both groups, 8 cows had normal to slight infiltration of leukocytes in the endometrium at the end of sample collection. No changes in granulocyte function could be seen in the 2 milking groups. Resumption of ovarian activity was detected on day 45.6 +/- 9.3 (mean +/- SD) postpartum in the 2x milking group and 36.6 +/- 9.0 (mean +/- SD) post-partum in the 3x milking group (p = 0.05). Based on our findings, an increased milking frequency from 2 to 3 times a day did not influence the uterine function postpartum.

Effect of energy and protein density of prepartum diets on fat and protein metabolism of dairy cattle in the periparturient period

To determine if increased nutrient density in prepartum diets improves nutrient balance of peripartum cows, we blocked 40 Holstein cows and 40 heifers by expected date of parturition and assigned them randomly within blocks to one of four treatment diets varying in density of net energy for lactation (NEL) and crude protein (CP). Diets were 1.30 Mcal of NEL/kg and 12.2% CP, 1.49 Mcal of NEL/kg and 14.2% CP, 1.61 Mcal of NEL/kg and 15.9% CP, and 1.48 Mcal of NEL/kg and 16.2% CP. These diets were fed ad libitum from 25 d prepartum until parturition, and all cows were fed the same diet after calving. Increased nutrient-density of prepartum diets did not decrease feed intake. Compared to animals fed the lowest density, those fed the highest density consumed more NEL (20 vs. 14 Mcal/d) and gained more body condition, backfat, and body weight. They also had less nonesterified fatty acids in plasma (176 vs. 233 microM) and more insulin-like growth factor-I in plasma (472 vs. 390 ng/ml) during the last 2 wk prepartum and less triglyceride in liver at parturition (0.9 vs. 1.5%, wet tissue basis). Quadratic effects of energy density were not observed, and the addition of protein in the medium energy diet had no effect. Prepartum diets did not alter any variables during lactation. In conclusion, increasing the energy and protein density up to 1.6 Mcal of NEL/kg and 16% CP in diets during the last month before parturition improves nutrient balance of cattle prepartum and decreases hepatic lipid content at parturition.

A veterinary perspective of on-farm evaluation of nutrition and reproduction

Reproductive herd health programs of the 1960s and 1970s focused primarily on the control of infectious and noninfectious diseases of the reproductive tract, estrus detection, breeding technique, semen quality and handling, and endocrine imbalances. Despite veterinary intervention, conception rates dropped from 55% before this period to 45% after this period, but milk production increased greatly. Because studies have shown that the additional nutritional needs for high producing cows may be a factor limiting reproduction, bovine practitioners have become more involved with dairy nutrition. New emphasis has been placed on the concept of total production medicine with the anticipation that improved nutrition would improve reproduction. Because of a better understanding of the dynamics of energy in the dairy cow and its effect on reproduction, fertility examinations now include nutrition monitoring and body condition scoring. Several relationships between nutrition and fertility have been identified: high producing thin cows that drop 0.75 to 1.0 in body condition score resulting in anestrus; fat dry cows that develop fatty livers and associated postpartum disease; heifers that have good milk production but prolonged anestrus; dry cows with ration imbalances during the transition period that develop milk fever, retained placenta, displaced abomasum, metritis, or endometritis; lactating cows with disease in midlactation, especially feet and leg problems, resulting in lowered fertility; and healthy, lactating cows with poor conception that have high concentrations of urea N in blood or milk.

Efficiency of nutrient use and relationship to profitability on dairy farms

As cows eat more feed to support higher milk production, the proportion of digested energy that is captured in milk increases. In contrast, as cows consume more feed, digestive efficiency decreases, but the magnitude of depression in digestibility is not characterized for high producing cows. Despite the digestibility depression, biological efficiency increases considerably as Holstein cows produce more milk up to 15,000 kg/yr. Above 15,000 kg/yr, the gain in biological efficiency per unit of increase in milk production is expected to approach 0. At 21,000 kg of milk/yr, approximately 25% of the gross energy consumed by the cow during the first 5 yr of life likely would be captured as milk, conceptus, or body tissues; further gains in biological efficiency are not likely without major advances in feed digestion. Although feeds generally cost more as cows are fed for higher milk production, increased productivity also enhances profitability, partly because of increased efficiency but also because fixed costs are decreased relative to total costs. This relationship between productivity and profitability is expected to continue up to > 21,000 kg/yr per cow. Other issues related to the efficiency of nutrient use will become more important in the future, namely, efficiency of the use of feeds that can also be consumed by humans, efficiency of use of tillable land, and minimization of nutrient losses to the environment.

Effect of supplemental fish meal on the lactation and reproductive performance of dairy cows

The influence of high protein diets (21% CP, DM basis), containing varied percentages of RUP, on lactation performance and fertility was evaluated. Sixty-two Holstein cows (65% multiparous) were blocked by age and randomly assigned to a 2 x 2 x 2 factorial design from d 12 to 125 postpartum. Factor 1 was 0 or 3.5% fish meal diet, factor 2 was location (Calan door versus free stall), and factor 3 was parity (first versus second or later). The soybean meal diet consisted of alfalfa hay, corn silage, barley, and soybean meal. The fish meal diet contained 3.5% fish meal (ruminant grade menhaden) that replaced a portion of the soybean meal. Cows fed the fish meal diet (40% RUP) had DMI, BW, and body condition similar to those of cows offered the soybean meal diet (34% RUP). Cows receiving the fish meal supplement tended to have higher milk protein production throughout the trial, higher milk production during the first 6 wk, and significantly lower ruminal ammonia concentrations than cows receiving the soybean meal diet. Differences in reproductive performance were not significant except for a diet by housing location interaction for conception rates from first AI.

Relationships between administration of GnRH, body condition score and fertility in Holstein dairy cattle

The objective of this study was to determine the effect of GnRH treatment in dairy cows differing in body condition score. A total of 2437 primiparous and multiparous cows was allocated randomly to receive either GnRH (100 microg) or placebo at the post partum exam (25 to 35 d) and at the first breeding. Complete records were available from 1906 cows: Group 1 (n = 535) placebo and placebo; Group 2 (n = 489) GnRH and placebo; Group 3 (n = 438) placebo and GnRH; and Group 4 (n = 444) GnRH and GnRH. The change of body condition score during early lactation was determined on a 1 to 5 scale (1 = emaciated to 5 = obese). Cows with a high body condition score (> or =3.0) at the first breeding had 8.8 fewer days to first service and 6.4 fewer days open but more services per conception (0.16) than cows with low body condition score (<3.0). Conception rate improved when GnRH was administered at the first breeding to cows with a body condition score of <3.0 at the first breeding regardless of parity. The administration of GnRH at the post partum exam decreased the conception rate in first lactation cows but was beneficial for cows in second and greater lactations. Thus the efficacy of GnRH may not be consistent in all parities and body condition groups.

Estrous behavior and detection in cattle

Hormonal events determine the timing and maximum duration of estrous behavior, whereas environmental and social factors modulate or completely inhibit the expression of estrus. The efficiency of estrous detection can be improved on most livestock farms if more effort is given to visual observations of estrous behavior. Heat detection aids can be of value if used as a supplement to visual observations. Knowledge of factors that inhibit estrus can help producers avoid or minimize situations that make estrous detection difficult or impossible. Each livestock enterprise should have a customized heat detection program in place because blanket recommendations often fail when applied to many operations.